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RELEVANT MICRO-CONCEPTS OF COMMON NIGERIAN CIVIL ENGINEERING MATERIALS Professor Danladi Slim Matawal Abubakar Tafawa Balewa University Bauchi 5th November, 2001

ABSTRACT Of all the disciples of engineering, the greatest strides, and the most independent practice in Nigeria, has been in the branch of Civil Engineering. This is because windfall profits and incomes of oil revenue, since the middle sixties, resulted in huge developmental projects/efforts to provide basic, essential and service infrastructure, office and housing accommodation for the population and for their desire to improve. This has led, up to date, to completed and ongoing construction of over 5,000 kilometres expressways, 12,000-15,000 kilometres of cross country freeways as well as a large volume of urban roads and infrastructure. Additionally, there are 7 major bridges across the rivers Niger and Benue, not less than 80 bridges on their tributaries and up to 20 bridges across the distributaries on the Niger-delta. Major bridges like the third axial, Mainland and Eko are in Lagos, similar ones in Warri (e.g. the link across the creek from NNPC to Aladja Steel complex), Sapele, Port Harcourt and Calabar in the creeks off the Atlantic ocean have been built while major seaports and airports, huge buildings, drainages, housing estates, dams, water plants and even a new Federal Capital city of Abuja as well as many state and LG capitals have sprung up. A thriving and vibrant private sector together with frequent shortlived rise in the living standards of the populace has also resulted in private corporate and individual investment in housing and office buildings. utilizing many civil engineering materials. The civil engineering materials that have been most commonly used for these activities are soils, stone aggregates, cement, structural steelwork and reinforcement rods, asphalt and timber/wood as well as water. The ubiquitous use of these materials has imparted upon the generality of Nigerian developers the technical know-how, skills and confidence to apply them frequently without the need for references. It has also led to a complacent attitude as to the utilization of 1 All the activities have involved construction

these materials, which are frequently applied, with many avoidable misapplications resulting in uneconomical, shoddy, cracked, failing and collapsed structures and infrastructure for both the individual/private as well as the corporate developers. Many micro concepts; relevant and significant, have been ignored that could improve the quality of our developments, if known and applied. These relevant micro concepts of in-situ materials used in foundations, concrete works as well as those of water applied everywhere for mixing and drinking are espoused in this lecture. Manufactured and uncommonly used materials are mentioned but not elaborately delved into since they should always be subjected to industrial and factory quality controls where professionals are involved. However, if they have to be remolded in application, like cement, then the concepts of remolding (often with changes in the material chemistry) are presented without emphasis on purely technical issues that are taught in classes. Finally, the results of personal research works and knowledge gained from years of field experience, related to materials, are presented. It is hoped that the stuff of this lecture will be found useful and basic by the common Nigerian developer including those aspiring to build personal homes and businesses, as well as managers of corporate public and private enterprises, and those in Government. 1.0 INTRODUCTION

Civil engineering is that field of engineering concerned with the planning, design, and construction for environmental control, development of natural resources, buildings, transportation facilities, and other structures required for the health, welfare, safety, shelter, employment, and pleasure of mankind. As a result of this focus of the profession, the scope of functions undertaken by the civil engineer are quite wide and varied including land drainage, water supply, rivers, canals, harbors, docks, marine construction, water power, sewage disposal, sewerage, bridges, tunnels, railways, roads, traffic engineering, foundations, airports, municipal engineering, soil mechanics, structural engineering, town planning, and transportation engineering. In the course of implementing the functions of civil engineering, intensive and extensive use is made of natural resources, in the form of materials, for the design and construction of necessary structures and infrastructures. Some of these materials used in civil engineering include soil, water, steel and metal alloys, timber, cement, stone and stone

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aggregates, sand, admixtures, fabric and synthetic geo-textiles, plastics, bitumen and so forth and so on. The application of these materials for design and construction can be in a monolithic or composite form. The type, nature and quantity of materials used also depends largely on the complexity of the engineering scheme as certain structures, due to large forces and stresses in members, may require modification of common materials to suit the peculiar application. For example, alloys can be used rather than normal steel; soil can be stabilized rather than apply it in homogenous state, while cement concrete may need to be improved to give it higher strength/grade. It is also true that the use of Civil Engineering materials, in whatever format, must be applied, molded and cared for according to certain engineering principles, governing their behaviour and characteristics, so that optimal objectives can be attained. These principles relate to strength of the material, its elasticity and plasticity properties, water absorption and compressibility/swelling phenomena, matters related to deflection and fatigue, life-span etc. The principles could be theoretical or practical or both but which, when observed, will lead to better performance of the designed structure. It is the objective of this lecture to expose some of the very relevant micro-concepts of the use and application of Civil Engineering materials in the Nigeria environment in such a manner that it will be useful to our many people involved everyday in the building of homes for shelter, roadways for transportation, land drainage for a safe environment, water supply for life sustenance, retaining wall structures for sea, ocean and river defences and numerous other structures for the benefit of mankind. It is important, at the outset, to reiterate that the list of Civil Engineering materials is almost limitless as almost every natural and artificial item that has form, and/or strength (however low), is a potential material for building one object or another. However, when scanning them, it is always obvious that some are more abundant, cheaper and more commonly used than others. For these, their use is virtually an ubiquitous phenomenon and they are usually utilized by professionals and non-professionals, alike. It is also significant to understand that while some are manufactured and, therefore, rigorously subjected to professional factory quality control, others are actually manufactured or built or mixed on the site (in-situ). The latter include soil and cement, being the most common Civil Engineering materials. The application is usually subject to certain micro-concepts that improve their performance. 3 Some of these micro-

concepts, considered relevant, are treated in this lecture. The concept of water supply for drinking and domestic applications is also treated since water can also be considered another very ubiquitous commodity for the health, welfare and pleasure of mankind. Not really relevant is the mention, and scanty treatment, of the other civil engineering materials notably steel, timber and bitumen. It is believed that the audience as well as readers of this lecture will, no doubt, find that many of the micro-concepts are so relevant that it will change, positively, our perception and posture in the use of Civil Engineering materials for our personal estates, and business developments. It will also result in better physical development for the public enterprises that we ably manage. 2.0 NIGERIAN CIVIL ENGINEERING VERSUS THE WORLD

Before the discussion of the micro-concepts of civil engineering materials, let us look at some of the prominent structures of the world, compare them with Nigerian structures and assess what materials are used in construction. This is easily made using the categories as set out below. 2.1 Structures above ground: include bridges, dams, towers, masts and tall as well as large

clear span buildings. The world's longest span bridge is the Honshushikoku link at Akashi straight in Japan with a main span of 1780 metres made of steel trusses. As a matter of fact, the World's long spanning bridges are ally suspension types made principally of steel mainframe. In Nigeria, the longest bridge is the third axial bridge from Lagos Island linked to Herbert Macaulay way in Yaba made of concrete and passing right through the Atlantic Ocean. The world's long span bridges are all suspension types made principally of steel. Nigeria's large bridges are either at Lagos or other coastal cities or the many arch bridges crossing the rivers Niger and Benue and are all made of concrete: a mixture of cement, stone aggregates and fine aggregates with water, reinforced with structural rods. Their foundations sit on soil via specially piled footings ad caissons. The World's largest dams are in the Russia or their breakaway republics like Bratsk (with volume of reservoir 169.2km3) at Angara river, Irkutsk; and Nourek dam (highest dam at 317 metres) on the Vakhsh river in Tadjikistan close to the Afghanistan border. There are numerous other large dams like Aswam, Kariba etc. but the Kainji dam is Nigeria's largest. Large dams are generally mainly of earth fill embankment with a clay core but will usually have a central 4

portion of gravity masonry construction for overflow purposes and electricity generation, if it is meant for hydropower. It always sits on the parent soil, which constitutes its foundation. The World's tallest buildings are the 109 storeys twin Sears Towers in Chicago, Illinois (442 metres), until September 11, 2001 there was the 110 Storeys twin World Trade Centre at New York city, USA, (411.5 metres); the 102 storeys Empire state building, New York city (381 metres), 89 Storeys Standard Oil Building, Chicago (346 metres) etc. In fact, the eight World's tallest buildings up to September 10, 2001 were either in Chicago or New York city with the 49 storeys National Westminster Bank's headquarter in London being the tallest (183 metres) in Britain. A set of twin towers was commissioned in 2001 in Malaysia which, when the details are available, will make an impression. In Nigeria, the NITEL building in Lagos has been the tallest (37 storeys) while many other tall structures have been built along the Marina, in Lagos, as well as in the city of Abuja. The modern practice in the design and construction of skyscrapers is to use structural hybrids of masonry, iron and steel that depends partly on load-bearing walls and is the situation with world and Nigerian buildings. They use high-strength steels-alloys (up to 100 percent stronger than normal steel). The World's tallest towers and masts are generally built for communications purposes such as radio and television transmission. They exist in Nigeria and other parts of the world mainly in form of structural steel framework. The world's tallest structures are either masts or towers namely: Warszawa radio mast at Plock, Poland (645.38m), Stayed television mast in North Dakota, USA (629m), CN Tower at Toronto, Canada (553m), Ostankino TV tower in Moscow, Russia (537m), Stayed television mast at Knoxville, US (533m), Stayed television mast at Columbus, US (533m), Stayed television mast in Missouri, US (510m). The tallest structure in Nigeria is the Plateau stayed television mast at Rayfield, Jos with the author of this paper as the Soil/geotechnical consultant of the project in 1981. The World's largest buildings are assessed in terms of floor area, frequently the clearest long span and the USA has the most of the world's largest building. The Boeing Assembly hall with cubic content of building of 5.8 million m3 is the largest. In Nigeria, the National theatre at Iganmu, Lagos, the International Conference Centre, Abuja, the Multipurpose Indoors Sports hall in Bauchi and many lecture theatres, like the one in A.T.B. University built with the author as Consultant, are large buildings in Nigeria. They are constructed of concrete and steel frames/space truss to span their large centre to centre roof supporting mechanisms. 5

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Structures below ground:

include tunnels, underground workings, excavation and

dredging, foundations and ground engineering. The world's longest tunnels are scattered in USA, South Africa, Europe and Japan for water supply, irrigation, submarine railway, drainages, aqueducts, diversion works and reclamation. The Delaware aqueduct in New York at 169 kilometres is the world's longest while the 57 kilometre submarine railway tunnel from England to France made a big construction news in the last decade though it may be only the forth longest in the world. No tunneling activities of significance have, to date, been recorded in Nigeria but in the future they will be necessary to cross some of the difficult obstacles in transportation. Tunnels driven beneath the beds of rivers, estuaries and the sea are the most difficult but all tunnels involve extensive excavation (tunneling or cut-and-fill techniques) in soft ground (soil) and in rock. Subsurface drainage is an important feature of tunnels as well as the associated underground workings. Muck-Shifting, which is the odd name for excavation and dredging, is always the starting point of civil engineering and yet the records tend to be held in mining. The world's largest excavation record for many years was the Bingham Canyon copper-mine, near salt lake city, Utah, USA, from which 3500 million tones (1200 million m3) of material (soil/rock) was excavated. I have only recently watched the documentary film of the Hansai international airport project for which a new Island 4 kilometres x 1.5 kilometres was created from an 18 metres deep sea in Japan. The soil fill was obtained by completely demolishing mountains and transporting the material to create the new Island. In Nigeria, gargantuan mining pits and valleys from which millions of cubic metres of soil was excavated, some still existing as spoil mounds, have been mined on the Jos Plateau for tin and columbite. Excavations are associated with city building, earth dams and road works and these construction edifices can be sited near major cities of Nigeria in the form of borrow pits. We are also probably all acquainted with huge dredging activities by National Westminster Company along the river Niger as well as those that accompanied the construction of coastal ports at Lagos (Apapa and Tin-can Island); Port Harcourt (main Port and Onne terminal); Warri, Calabar, Sapele and Koko. The single most important civil engineering material in excavation works is soil followed by rock. Foundations generally comprise of the direct bearing and piled foundations, which are structural elements intended to transmit the super structural loads to the ground. Even though common 6

reference is usually made to them, nonetheless foundations include the sophisticated types like trench or pier foundations, buoyant foundations, caissons, cylinders and monoliths, as well as the very important sheet-piling works. There are also cut-off wall/trenches, drainage blankets and other forms of construction. In terms of foundation practice, it can be argued that wherever there is a human habit, there is always a foundation to design and construct. The Sears towers, as example, are pinned down to four basements (underground storeys) into the ground and the foundation is made of 4 metres thick raft on top of basement complex. The most common foundations in Nigeria are strips and pads but there is a very established piled practice associated with large/tall structures as well as difficult ground. The Agriculture faculty building by A.T.B. University at Gubi site is on bored piled foundation, designed by the author, because it was located on a displaced stream valley. However the lecture theatre of the university is on pad foundation as are the bigger structures like Zaranda hotel and NIDB buildings here in Bauchi. For foundations of buildings generally, the main civil engineering material is concrete reinforced with structural rods and interacting directly with soil. The soil, which in such instances is the foundation material, actually becomes the construction material as fill on ground floors and in roadways. Foundation techniques are very complex processes and involve rigorous concepts of analysis of shear capacity, structural competence, compressibility and settlement principles, and the comprehensive modeling of water seepage forces and flow patterns. The difficult foundations in literature include the deepest caissons and monoliths like the South Bisanseto bridge (75m x 64m caissons), in Japan, the San Francisco-Oakland Bay bridge (60m x 28m caisson) central anchorage in USA; etc. Caissons are concrete or steel containers of soil and the above quoted ones were sunk to depths of 129 metres and 66 metres, respectively, in fast flowing water ways. On the other hand, sheet piles which are common in city building are principally reinforced thick strong gauge steel sheets retaining soil. Major piling associated with buildings and bridges are usually concrete but can be steel and also timber. 2.3 Ground engineering: are geotechnical processes like cofferdams, control of ground water; diaphragm walls, grouting and chemical treatment (Stabilization). Much of ground engineering has to do with improving properties of poor soils or the science of movement of water in the soil for control purposes. Ground engineering techniques are very common procedures on Nigerian roads and many significant construction projects. 7

2.4 Hydraulic works: include harbours, canals, barrages, spillways, flood control, sea defence, civil works associated with hydro-electric power, pumping stations, irrigation, aqueducts, pipelines, water supply and treatment, main drainage and sewage treatment. Even though the central theme in hydraulic works is the beneficial harnessing of the properties of water for mankind, nonetheless many of the associated structures required are very huge engineering edifices of soil, rock, concrete and steel. Jetties, Terminals and deep water ports are very complex hydraulic structures to construct: the Rotterdam, as example, is the world's largest port (by length of quay or berth in the port). There are also canals and Inland Navigations, the notable ones being St. Lawrence Seaway, Europe canal, Grand Canal, Amazon, Mississippi, Suez, Panama, etc. In Nigeria, dredging has been undertaken for inland navigation on the Niger, Imo and Cross Rivers. Flood control and sea defences are great schemes for protection against river floods and tidal waves. Their main material is sand/soil and rock boulders as well as sheet piles of steel or gravity walls of masonry. Pipelines can be of asbestos-cement, galvanized iron and plastic: recently, some Nigerians have been writing on bamboo soil pipes. 3.0 MICROCONCEPTS OF SOIL AS FOUNDATION AND CONSTRUCTION MATERIAL From the account of structures presented above, it is clear at this stage that one of the versatile civil engineering materials is the soil. Later on, when I shall be listing an account of my personal contributions in research and practice, it would then be observed that Nigerian soils exist in many varieties exhibiting different properties and characteristics, some attractive and other problematic. Basically, in summary, soils are applied in practice as: i) ii) iii) iv) v) vi) Foundations of buildings and all forms of structures. Construction material for road base, sub base and sub grade courses in roadways. Construction material for the foundations of paved areas, parking spaces, airport tarmacs etc. Construction material for earth dams, cutoff walls, central core of rock fill dams and certain seepage and erosion control structures. Construction material for earth fills beneath the floors of structures. Construction material for backfills behind retaining wall structures.

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vii) viii)

Construction material in caisson foundations and land reclamation schemes as well as dredging and other works. Construction material for buildings of mud, compressed earth and burned bricks/fired clay.

In all theoretical and practical applications of soil, the fundamental considerations and principles are aimed at assessing the strength (shear) and consolidation/compressibility characteristics of the material. It is interesting to have known that when the twin world trade centre towers of 110 storeys (411.5 metres) collapsed following the terrorist attacks of September 11, 2001, the substructure supported by the soil was quoted to be undamaged. Indeed the soil has a tremendous capacity to take impacts from crushes of explosives, plane crashes, shuttle machines and, of course, the world's structures of all sizes and heights. The soil takes the loads imposed by these situations quite comfortably: frequently it does so with very prominent and noticeable deformations and settlements depending on the material plasticity. Because the strength and consolidation characteristics of the soils are so influential, I have found it convenient to classify the theorems and principles associated to these properties (i.e. shear and settlement) as macroconcepts. However, there are certain micro-concepts related to the behaviour and response of the soils to loading conditions that affect their strengths tremendously but which we frequently easily overlook. One of these micro-concepts deals with the influence of water within the void spaces of the soils. The concept is easily explained by the piston and spring analogy. A load (stress), is applied on the piston. The loads taken by the spring and water are / and u, respectively. At the beginning, as long as the weep hole is closed, = 0 and = u; i.e. the whole load is taken up by the water. When the weep hole is opened gradually, stress is transferred from the water to the spring so that / > 0 so that at any finite time, t, = / + u and at t = , u = 0 and = /.

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Applying our analogy to practical conditions, the spring is, in reality, the soil skeleton or solid particles, in nature, while the water in the container is the pore water in the soil voids spaces. is known as the effective stress while u is the pore water pressure. The rate at which water seeps out of the weep hole can be compared to the practical permeability of the soil. This concept; known as the principle of effective stress, was explained, in detail, by Matawal (1990). The effective stress theorem is a basic practical situation that is easily appreciated by the following illustrations: a) Foundations on low permeability soils (clay and tropical laterites, as example), are known to exhibit continuous time-dependent settlement. Under constant load, long after application of full service conditions but which is not creep. This is due to gradual dissipation of the initial excess pore water pressures: a phenomenon that can be illustrated using the mathematical model of consolidation which we can use to predict the time-settlement responses of slow draining soil media subjected to changes in loading conditions. b) Of considerable importance; but usually less obvious, are the regional settlements resulting from ground water lowering in compressible soils either due to pumping for water supply (as in boreholes) or due to other engineering situations. Regional 10

settlements were quoted in London around 1942, in Oslo, Norway in 1953 and Mexico city in 1953, Matawal (1990). The settlements resulting from land reclamation and dredging for ports construction projects at Warri, Lagos (Tin-Can Island), Calabar, Sapele and Koko, all in Nigeria, in 1979 are quoted by Matawal (1987). c) The settlement of light foundations, which are generally shallow, in Nigeria, in the dry season, due to negative pore pressures set up by drying or by suction of plant roots or; in certain instances, complete drying out is one other result of the effective stress principle. The role of water in the void space, as explained in the effective stress principle also assists us to undertake ground improvement schemes on soft soil to enhance their strengths. It is understandable that if the normal stress on a shear plane can be increased, then the shear resistance can also improved upon and, consequently in the case of soils, their strengths enhanced. The normal stress on the shear plane of a soil mass is essentially the inter-particle contact force which is about the same as the effective stress. It clearly follows that when we accelerate drainage conditions, we can then speedily dissipate the excess pore water pressures set up and thus increase the effective stresses in the soil. This is a fundamental micro-concept that is frequently used to solve recurring instability and failure problems associated with slopes in earth dams, cuts and fills, or roads and other embankments. The acceleration of drainage to improve strength and reduce the long term settlement of structures can be achieved using drainage filters: sand drains, plastic drains and cardboard drains. Conversely, slow dissipation of excess pore water pressures; as well as poor drainage of embankments, can lead to catastrophes in the following ways: · · · · Failure of downstream slopes of earth dams through rotational slips e.g. Gubi dam at inception and Bauchi ­ Jos highway. Failure or road and other earth foundations structurally by the development of potholes e.g. City roads in Nigeria as well as Federal and State highways. Failure of fills beneath the floors of buildings noticeable in many structures. Failure and severe cracking of building structures, particularly walls on strip foundations. 11

·

Failure of pile foundations due to inadequate shaft friction on the skin of the pile.

There is a phenomenon, a micro-concept, of soil relationships with water that is quite important to highlight at this juncture. It is observed in the compaction of soils, an operation that must always be undertaken when soils are used as construction material namely: fills under floors, base and sub-base courses beneath the pavements of roadways and parking lots; the general construction process involving soil placement in compacted layers. A typical compaction curve shown reveals that when soil is mixed with water and compacted, the dry density (representing a state of compaction) rises, peaks up abruptly and then drops again. Every soil exhibits this typical behaviour as confirmed in numerous studies by the author and which will be presented later.

The implication of this compaction phenomenon is that for every compaction effort, there is a `maximum dry density (MDD)' of any particular soil which is found to correspond to a moisture condition known as the `optimum moisture content (OMC)'. In fact, this typical relationship can be represented by a mathematical model known as the compaction formula (d = b / (1 + m)), correlating dry density, d, to the known and measured bulk density, b, with the water content, m, as the variable. It always gives a perfect curve. If, for some reason, the moisture content is 12

too much on the wet side of optimum, the soil rebounds or swells on application of the compaction effort and it becomes near impossible to compact the soil practically and theoretically speaking. It has led to the practice over the years in which construction works involving soil compaction, and consequently remolding, are normally suspended in periods of inclement weather. It is easily observed from the compaction curve that the density, and therefore soil strength, falls so rapidly from peak with an increase or decrease of the moisture content. In dry weather, the moisture content can be increased, in a controllable manner, on soil fills and layers to meet the optimal conditions. However in periods of inclement weather when rainfall is fierce, heavy and persistent, it is impossible to achieve optimal moisture contents. Therefore construction must either be stopped for the period (i.e. suspended) or deterioration of the constructed facility must be expected immediately the inclement weather or rainy/snowy season passes. Infact, this together with poor soil usage as well as the poor water-proofing qualities of the asphalt cement pavements are principally responsible for potholes on our roadways in highways. Another micro-concept is related to the passage of water through soil media, a process known as seepage. Forces above the normal hydrostatic level are known as excess pore water pressures. However, in the process of seepage, certain damages are usually posed to the earth structure if necessary remedial measures are not put in place. One of these, which is significant, is the installation of toe filters in the form of sand blankets, relief wells, and any similar improvisators, at the downstream end of earth dams and earth embankments. In the absence of these tow provisions, seepage flows/pressures usually wash out fines from the compacted soils of the earth structure. The result is usually devastating because there is what is commonly referred to as core erosion resulting in soil pipes. It does not take long before huge voids are created in the body of the earth structure emanating at the surface in the form of collapses and holes. It is also easy in practical situations of soil construction to trap huge hydrostatic pressures, beneath embankments, which emanate elsewhere at low points in the form of boils and quick condition. If relief wells are not installed, they can lead to blow-ups when a huge accident would have taken place.

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As an end to the discussion on soil as construction material, it is important to be acquainted with some procedures of ground improvement. Because we deal with soils of all form of properties, some with very undesirable characteristics, it is usually necessary to improve these properties to meet with the minimum specifications required for construction. This matter is treated under the topic of stabilization, which is considered in a separate chapter. 4.0 SOIL IMPROVEMENT BY STABILISATION

Stabilization of soils have been extensively pursued by three (3) Nigerian researchers namely Balogun, Matawal and Ola; in separate studies quoted in the references. Stabilization has been with the use of either cement or lime to improve the properties of soils. One of the important micro-concepts of soils engineering is the influence of the crystal structure on the properties of the material. All soils of the earth are formed from either 2 layer or 3 layer minerals. Whereas such soils like illite are formed of 2 layer minerals, others like kaolinite and montmorillonite are from three layer minerals. A 2 layer arrangement comprises of an octahedral sheet on top of a tetrahedron crystal. The basic building units of soils stack together to form the mass of soil. In the stacking arrangement of the basic units, the crystals are held together at their interfaces by certain forces. If these forces are metallic, example bonding with potassium irons, then they are usually very strong forming stiff soils with high shear strength and low compressibility characteristics. On the other hand, the bonding can be weak as is the case with adsorbed water in between the crystals. It gives rise to soils of low shear strength and high compressibility. Some of these properties are clearly undesirable and frequently need to be improved through the process of stabilization as follows: i) Cement stabilization is a common process of soil/ground improvement by spreading, mixing and compacting cement with the poor soil. However, studies by Ola (1978, 1974); Matawal (1996, 1991 and 1990) and Balogun (1991) have revealed that the economic use of cement as a stabilization agent must stop at 9 percent beyond which we are dealing with concrete (presented later in this lecture). All the studies show a varied benefit via improvement of the strength, permeability, compressibility and swelling properties of the soils. Cement stabilization actually affects the crystal structure of the soil resulting in what the author calls `soil cement'. Calcium, from 14

the cement, replaces the absorbed water layer resulting in stronger keying or bonding of the soil basic building units together giving rise to better construction material. Cement stabilization is a very common process in the construction of roads in Nigeria. ii) Lime stabilization studies have been undertaken by Ola (1974) and Balogun (1991) and involve the addition, mixing and compacting of lime to poor soil. The resulting mixture has vastly improved properties by the same changes in crystal structure of the soil as in cement stabilization. It is possibly easy to understand that cement and lime stabilization are very similar because lime is a basic raw material of cement. iii) Mechanical stabilization processes are essentially similar to compaction or even mean compaction. It is common and because compaction has already been presented needs no further elaboration. 5.0 MICRO-CONCEPTS OF CEMENT ENGINEERING MATERIAL AND CONCRETE AS CIVIL

Concrete is essentially a mixture of cement with natural aggregates of sand/quarry dust and stone. When the mixture is of cement and sand or quarry dust only, the resultant is called sancrete and if it is cement and soil only, it is soilcrete. The most interesting thing about these mixtures is that the prime objective is to attain bonding of the coarser aggregates (which provide strength) with cement (which provides the glue). The strength of natural aggregates, particularly stone, is a macro-concept and so to gain insight into this aspect of civil engineering materials, it will be sufficient to look into the micro-concepts of the cementatious material, which is regulated by the engineer. Cement, like other cementatious materials, contains inorganic nonmetallic products that are mixed with water or another liquid to form a paste. The paste, which is temporarily plastic and may be molded, may or may not have aggregate added to it. Later, it hardens or sets to a rigid mass. Driving off a liquid or gas from the natural mineral produces the simple cementing materials, such as limes and plasters. Their cementing properties arise from the re-absorption of the liquid or gas that has been expelled and the formation of the same chemical compounds of which the original raw material was composed. The more complex hydraulic cements derive their cementing properties from formation of new chemical compounds during the 15

manufacturing process. The term hydraulic applied to cements means capable of developing strength and hardening in the presence of water. Limes, plaster and hydraulic cements are not widely used. The most widely used is Portland cement concrete which is the most important construction material employing a cement. Understanding of the factors affecting the constituents of concrete, the Portland cement and aggregates, is essential to a fundamental understanding of the production and behaviour of concrete and the influence of water on its properties. 5.1 Portland Cement Manufacture: Portland cements are made by blending a mixture of

calcareous (lime containing) materials and argillaceous (clay) material. The raw materials are carefully proportioned to provide the desired amounts of lime, silica, aluminum oxide, and iron oxide. After grinding to facilitate burning, the raw materials are fed into a long rotary kiln, which is maintained at a temperature of about 1482oC. The raw materials, burned together, react chemically to form hard, walnut-sized pellets of a new material, clinker. (Lime) + (Silica + Alumina + Ferric Oxide + Water) + Heat Tricalcium silicate + Dicalcium silicate + Tricalcium aluminate + Tetracalcium Aluminoferrite = Cement. [Lime = CaO + CO2, Silica = SiO2; Alumina = Al2O3; Ferric Oxide = Fe2O3, Water = H2O]. [Tricalcium Silicate = 3CaO. SiO2, Dicalcium silicate = 2CaO. SiO2, Tricalcium aluminate = 3CaO. Al2O3; Tetracalcium aluminoferrite = 4CaO. Al2O3. Fe2O3]. The clinker, after discharge from the kiln and cooling, is ground to a fine powder ( 1600 cm2/gm specific surface). During the grinding process, a retarder (usually a few percent of gypsum) is added to control the rate of setting when the cement is eventually hydrated. The resulting fine powder is Portland cement. It is important to understand that because Portland cement is derived from unrefined raw materials, additional compounds are usually present in addition to the major essential ones. Four compounds, however, make up more than 90 percent of cement, by weight namely: Tricalcium silicate, Dicalcium silicate, Tricalcium aluminate, and Tetracalcium aluminoferrite. Each of these four compounds is identifiable in the highly magnified microstructure of Portland-cement clinker, and each has characteristic properties that it contributes to the final mixture.

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5.2

Hydration of Cement: When water is added to cement, the basic compounds present are Tobermorite gel + Calcium hydroxide Dicalcium Silicate Calcium aluminoferrite hydrate Tetracalcium aluminate hydrate Calcium monosulfo aluminate.

transformed to new compounds by some chemical reactions like: Tricalcium Silicate + Water aluminoferrite + Water + Calcium hydroxide Tetracalcium aluminate + Water + Calcium hydroxide Tricalcium aluminate + Water + Gypsum

Two calcium silicates, which constitute about 75 percent of Portland cement, by weight, react with the water to produce two new compounds: tobermorite gel and calcium hydroxide. In fully hydrated Portland cement paste, the calcium hydroxide accounts for 25 percent of the weight and the tobermorite gel makes up about 50 percent. The third and fourth reactions above show how the other two major compounds in Portland cement combine with water to form reaction products. The final reaction involves gypsum: the compounds added to Portland cement, during grinding of the clinker, to control set. Each product of the hydration reaction plays a role in the mechanical behaviour of the hardened paste. The most important of these, by far, is the compound called tobermorite gel, which is the main cementing component of cement paste. This gel has a compound and crystal structure to those of a naturally occurring mineral, called tobermorite, named for the area where it was discovered, Tobermory in Scotland. The gel is an extremely finely divided substance with a coherent structure. The average diameter of a grain of Portland cement, as ground from the clinker, is about 10 microns (0.010mm). The particles of the hydration product, tobermorite gel, are in the order of 1/1000 of that size (10 x 10-6mm). Particles of such small size can be observed only by using the magnification available in an electron microscope. The enormous surface area of the gel (about 3 million cm2/gram) results in attractive forces between particles since atoms on each surface are attempting to complete their unsaturated bonds by adsorption. These forces cause particles of tobermorite gel towards each other as well as to particles of aggregates introduced into the cement paste. Thus, tobermorite gel forms the heart of the hardened cement paste and concrete, in that it cements everything together.

17

Each of the four major compounds in Portland cement makes a contribution to the behavior of the cement as it proceeds from the plastic to the hardened state after hydration. Knowledge of the behaviour of each of these major compounds upon hydration permits us to understand the process on sites. · Tricalcium Silicate is primarily responsible for the high-early strength of hydrated Portland cement undergoing initial and final set within a few hours. The reaction is exothermic giving off large quantity of heat (heat of hydration) attaining most of its strength in 7 days. · Dicalcium Silicate exists in alpha, beta and gamma forms but only the beta is significant. It takes several days to set being primarily responsible for the later developing strength of Portland cement paste with low heat of hydration. It is known that it produces little strength until after 28 days but the final strength is equivalent to that of Tricalcium Silicate. · Tricalcium aluminate exhibits an instantaneous or flash set when hydrate. It is primarily responsible for the initial set of Portland cement and gives off large amounts of heat upon hydration. It shows little strength increase after 1 day but the gypsum added combines to control the time of set. Though it develops very low strength, nonetheless it is desirable in Portland cement as an increased amount results in faster sets and also decreases the resistance of the final product to sulfate attack. · Tetracalcium aluminoferrite also hydrates rapidly and develops only low strength but, unlike tricalcium aluminate, does not exhibit flash set. In addition to composition, speed of hydration is affected by fineness of grinding of clinker, amount of water added, and temperatures of the constituents at the time of mixing. To achieve faster hydration, cements are ground finer. Increased initial temperature, as revealed from research by Matawal and Abba-Gana (1998); and the presence of a sufficient amount of water, also speed the reaction rate.

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TYPICAL PROPORTIONS (%) OF MAJOR COMPOUNDS IN PORTLAND CEMENT I 53 24 8 8 93 TYPE OF PORTLAND CEMENT II III IV 47 58 26 32 16 54 3 8 2 18 8 12 94 90 94 V 38 43 4 8 93

COMPOUNDS 3CaO.SiO2 2CaO. SiO2 3CaO. Al2O3 4CaO. Al2O3. Fe2O3 Total (%)

Recollect that there are Hydraulic, simple and Portland cements. Hydraulic cements include Aluminous cements, Natural cements, White Portland cement and Hydraulic lime. Simple cements include Plasters, Limes (Quicklime and Hydrated limes) and others (Gypsum cements and oxychloride cements). Portland cements as shown in the table are: Type I ­ General Purpose, Type II ­ Modified general purpose, Type III ­ High early strength, Type IV ­ Low strength and Type V ­ Sulfate resisting. RELEVANT STRENGTHS OF CONCRETE AS FUNCTION OF CEMENT TYPE Comprehensive Strength %, of Type I Portland Cement 3 days 28 days 3 months 100 80 190 50 65 100 85 130 65 65 100 100 115 90 65

TYPES OF PORTLAND CEMENT I. General Purpose II. Modified III. High-early strength IV. Low heat V. Sulfate-resisting

There are also air-entraining Port land cements, by addition of air-entraining agent, designated types IA, IIA and IIIA, for the manufacture of concrete for exposure to severe frost action. 5.3 ENHANCING PERFORMANCE OF CONCRETE: The user of concrete, a very

versatile building material made from cement and aggregates, desires adequate strength, controlled set and consequently workability (placeability), and durability at minimum costs. The principal variables are the water to cement ratio, cement-aggregate ratio, size of coarse aggregate, ratio of fine aggregate to coarse aggregate, type of cement, and use of admixtures.

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i)

Water ­ cement ratio is a very important micro-concept for assessing strength and workability of concrete and it is easy to understand the influence of water in the hydration process of concrete from preceding discussions. Water ­ cement ratio, expressed by weight, affects the comprehensive strength of normal concrete. Strength decreases with an increase in the w-c ratio. The relationship is linear if concrete strength (log. scale) is plotted against w-c ratio, the slope is unity.

TYPICAL VARIATION OF STRENGTH OF CONCRETE WITH W-C RATIO W-C ratio N/mm2 ii) iii) iv) Cement content: there is a general decrease of strength with decrease in cement content. Type of cement affects the rate at which strength develops and the final strength. Curing conditions are very important in the development of strength of concrete. Since cement hydration reactions proceed only in the presence of an adequate amount of water, moisture must be maintained in the concrete during the curing period. It is for these reasons that watering and wrapping with wet jute bags is required for concrete elements after construction. Furthermore, the strength of concrete is detrimentally affected by early transfer from a moist atmosphere to a dry one as experiments by the U.S Bureau for reclamation shows, Merritt (1976). (N/mm2) 0.35 0.40 37 0.50 30 0.60 24 0.80 15 1.00 9 Average 28 day comprehensive strength, 42

TYPICAL CONCRETE CONDITIONS

STRENGTH

AS

FUNCTION

OF

CURING

Concrete curing/storage conditions 1. 2. 3. 4. 5. 6. Continuously in laboratory air In air after 3 days In air after 7 days In air after 14 days In air after 28 days Continuously moist cured 20

Comprehensive Strength (N/mm2) at No. of days 3 7 14 28 90 180 10 14 17 18 17 17 10 17 24 26 26 24 10 17 26 31 31 29 10 17 26 34 35 34 10 17 26 31 39 37 10 17 25 31 37 40

v)

Temperature for curing also affects concrete strength: a phenomenon amply demonstrated in experiments by Matawal and Abba-Gana (1998). Lower periods are required at lower temperatures to develop a given strength. Although continued curing at elevated temperatures results in faster strength development at 28 days, at later ages the trend is reversed as concrete cured at lower temperatures develops higher strengths.

6.0

MICRO-CONCEPTS OF STEEL AS CONSTRUCTION MATERIAL

Steel is used as reinforcement in reinforced concrete structures and as structural steelwork in frames, towers, trusses (including space tresses), bridges etc. In concrete, it is taken that concrete, being weak in tension, does not take such loading so that whenever direct or flexural tension occurs, then reinforcement must be introduced. As a manufactured material subjected to a lot of quality supervision and specifications, matters related to its uses and applications are rather too technical for a public lecture of this nature: they are macro-concepts to civil engineers taught rigorously in classrooms. Moreover, it is not a common material to the society who may never need elaborate reinforcement or structural steelwork for any work related to their housing and businesses. It is then only noteworthy to emphasise that, in use of this type of materials in the civil engineering industry, certain points must be observed to make optimal application of steel. These points are: · · · They must be free of rust or corrosion and where they have rusted, the scales should be thoroughly cleaned. The dimensions must be comprehensively monitored to ascertain that they conform to standards of the structural designs. The yield stresses should be checked because tests by Matawal (1990) revealed that while rods of smaller diameters (12mm and below) tend to give yield values equal or above specifications, the higher diameter rods (16mm and above) fall grossly below specifications.

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7.0

MICRO-CONCEPTS OF TIMBER AS CONSTRUCTION MATERIAL

Timber is remarkable for its beauty, versatility, strength, durability, and workability. It possesses a high strength-to-weight ratio and has flexibility. It performs well at low temperatures and withstands substantial overloads for short periods and has low electrical and thermal conductance. It resists the deteriorating action of many chemicals that are extremely corrosive to other building materials and is abundant in Nigeria. However timber differs in several significant ways from other civil engineering materials for which its cellular structure is responsible, to a considerable degree. As a result of this, structural properties are dependent on orientation. While most structural materials are essentially isotropic, with nearly equal properties in all directions, timber has three principal grain directions: longitudinal, radial and tangential. Loading in the longitudinal direction is referred to as parallel to the grain, whereas transverse loading is considered across the grain. Parallel to the grain, timber possesses high strength and stiffness (be it shear, tension or compression); while across the grain, strength is much lower. Timber is unlike most other structural materials in regard to the causes of its dimensional changes, which could be primarily from gain or loss of moisture; not temperature. A newly felled tree is green (contains moisture). In removing the greater part of the moisture, seasoning first allows free water to leave the cavities of the timber. A point is reached when these cavities contain only air, and the cell walls are still full of moisture. The moisture content at which this occurs, known as the fiber-saturation point, FSP, varies from 25 to 30% of the weight of the oven-dry timber. During removal of the free water, the timber remains constant in size and in most properties, but there is a weight decrease and it is called green timber. Once the fiber-saturation point has been passed, it is dry timber, and shrinkage of the timber begins as the cell wall loses water. Shrinkage continues nearly linearly down to zero moisture content. Eventually, the timber assumes a condition of equilibrium, with the final moisture content dependent on the relative humidity and temperature of the ambient air. Timber relationship of timber moisture content, temperature, and relative humidity can actually define an environment.

22

Research on Nigerian timber has been initiated in the university by the author and is continuing even though collation and analysis of results is still incomplete for presentation at this stage. 8.0 MICRO CONCEPTS OF ASPHALT AS CONSTRUCTION MATERIAL

Asphalt materials have been known and used in road and building construction since ancient times. Each type of asphalt was of natural origin, found in pool and asphalt lakes, but current supplies come mainly from the residues of refined petroleum. Asphalt, which is the black or dark brown petroleum derivative of fractional distillation process, is distinct from tar, the residue from destructive distillation of coal. Bituminous pavements result from asphalt refined to meet specifications for paving purposes, called asphalt cements. At normal temperature, it is semi-solid, with a degree of solidity measured by a penetration test. It is heated until liquefied before being blended with aggregate in paving mixtures. If asphalt is so soft that a penetration test is not an appropriate means for measuring consistency, it is called liquid asphalt. Several types of liquid asphalt are produced: · · · · Rapid curing (RC) asphalt, which is liquefied with naphtha or gasoline, both of which are highly volatile and evaporate quickly to leave asphalt cement. Medium curing (MC) asphalt, which is asphalt cement liquefied with a kerosene dilutant. Slow curing (SC) asphalt, which is blended with low-volatile oil. Emulsified asphalt, which is produced by mixing together water with an emulsifying agent and asphalt cement. This heterogeneous system of An asphalt spherical globules in the water medium hardens as the water evaporates. Asphalt pavements are composed of asphalt, aggregate, and voids (2 to 7%). pavement carries applied load by particle friction and interlock. Its strength is a function of the surface texture (particularly of the fine aggregate) and density (compactness) of the aggregate. A rough surface texture is desirable.

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TYPICAL ASPHALT ­ AGGREGATE COMPOSITION Constituent 1. Asphalt 2. Coarse aggregate 3. Fine aggregate 4. Mineral dust 5. Air Weight 6 53 35 6 0 Proportion (%) by Volume 14.4 43.7 33.4 4.9 3.6

Dense mixtures are obtained by using well-graded aggregates, where the fine aggregate fills the voids in the coarse aggregate structure. Coarse aggregate is that retained on a 0.01 mm sieve, fine aggregate passes the 0.01mm sieve, and quarry/mineral dust passes a 0.063mm sieve. The asphalt cement binds the aggregate particles together and waterproofs the pavements. The air voids allow the expansion of the asphalt cement or compaction of the composite by providing space for the asphalt cement to move into instead of pushing the aggregate further apart. 9.0 MICRO-CONCEPTS OF WATER AS CIVIL ENGINEERING TOOL

In the treatment of civil engineering materials, water is more of a tool as well as a medium for many human activities. It is an essential constituent of life that is unevenly distributed on our planet, earth. It is in excess in certain regions while there is desertification in many other parts of the world. The total estimate of the world's water resources, as example, is 1.45438 x 109 sq.km. A large proportion of these resources comprises of salt water contained mainly in the oceans, about 97.2 percent. 2.8 percent of the world's water is available as fresh water (salinity is due to dissolved salts: NaCl (80%) and MgCl2, MgSO4, CaSO4 all constitute 20%). Of the 2.8 percent fresh water, 2.2 percent is available as surface water while the remaining 0.6 percent as ground water representing the major influence in the interstices, voids and pore spaces of our substructures and the world's soils. Much of the engineering of water and water resources is in form of macro-concepts dealing with such topics like evaporation and transpiration, infiltration, stream characteristics, ground water hydrology, water conservation and other topics. Moreover, what is considered of micro-significance is the influence of water on the characteristics and processing of other civil engineering materials like soil and cement, already elaborately dealt with. Therefore what this lecture will touch on is the water for domestic use (drinking, washing etc) processed in large treatment plants for urban supplies. This is considered directly relevant to 24

the health of the common man and certain micro-concepts of water treatment may be appreciated for individual self-help. Matawal and Kulack (2001) have undertaken a comprehensive study of water from different sources of human consumption. Colony counts were made, temperatures taken, as well as tests for pH, biochemical oxygen demand (BOD) and total solids (TS) to ascertain their degrees of infection. The results of the tests reveal that these water sources; used for drinking by humans and animals as well as domestic applications, are in reality polluted above World Health (WHO) standards, some even over polluted. WHO BACTERIOLOGICAL STANDARDS FOR DRINKING WATER S/No SPECIFICATION 1. Throughout any year, 95 percent of samples should not contain any coliform organism in 100ml specimens. 2. No sample should contain more than 10 coliform organisms per 100ml specimens. 3. No sample should contain Escherichia-coli bacteria in a 100ml specimen 4. Coliform organisms should not be detectable in two consecutive samples of 100ml each.

WHO TENTATIVE LIMITS FOR TOXIC SUBSTANCES IN DRINKING WATER Toxic Arsenic Substance Max 0.050 Concentration, mg/l Cadmium 0.010 Cyanide 0.050 Lead 0.100 Mercury 0.001 Selenium 0.010

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RESULTS OF WATER TESTS ON RAW WATER SOURCES by Matawal and Kulack (2001) Sources 1. Drinking well 2. Flowing stream 3. Borehole 4. Stagnated pond 5. Pipe borne Temp. (oC) 27 28 26 30 25 pH 7.7 7.9 7.1 7.9 7.0 BOD (mg/l) 4.4 7.8 1.0 9.6 0.4 Colony ml x 106 1.10 1.16 0.00 1.39 0.03 per TS (mg/l) x 106 0.517 1.104 0.004 0.987 0.002

It is significant to know that pipe borne water, relied on by most of the population as hygienic, is in fact polluted in spite of treatment by the water works. This is quite significant but for good observers, is nothing new since, in periods of shortages, maggots have been known to flow out of our pipelines with the reestablishment of first traces of water supplies. 10.0 PERSONAL WORKS OF SIGNIFICANCE

The contributions that the author has made to knowledge of Nigerian civil engineering materials have been extensive in some areas while they are continuing on others. Accounts of these contributions are going to be presented without regard to any sequence. The influence of water in the microstructure of soils was exposed, in detail, in the presentation on effective stress principle, Matawal (1990). The influence of pore water pressures and the concept of effective stress as it affects shear strength, compressibility and other applications were researched into while the basic mathematical and physical relationships were presented and illustrated. Matawal (1990) undertook some physical and index measurements of concrete and steel elements used on construction projects in Bauchi town including reinforcement rods for the New Lecture Theatre Complex in the University campus at Yelwa. While the concrete was found to be in conformity with specifications for strength and durability, certain deficiencies were observed in the results of the reinforcement rods. As example, in addition to other analytical and professional shortcomings, it was observed that while the yield of the smaller diameter (below 16mm) rods showed agreement or even exceeded the code specifications of industry, the higher diameter (16mm and above) fell below the standards by 5 to 10 percent. Furthermore, the nominal diameters of the bars rolled out of steel industries always fell below

26

the specification by as much as 0.8mm, which is a substantial reduction of the cross-sectional area required to carry tensile stresses in reinforced concrete elements. Matawal (1990) subjected five (5) soil specimens from the Jos Plateau and from Bauchi to compaction and strength studies. Details of some tests on these soils are shown in the table below: RESULTS OF IDENTIFICATION TESTS ON SOILS FROM BAUCHI Sample No. 1 2 3 4 5 CONSISTENCY LIMITS (%) LL 30.30 35.80 32.70 31.40 38.60 PL 18.7 25.66 26.65 N.P. 20.51 PI 11.59 10.14 6.05 0.00 18.09 SL 9.07 6.43 3.57 3.21 8.93 CLAY 24 40 27 57 34 SOIL FRACTIONS (%) SILT 3 6 9 11 5 SAND 22 32 33 28 33 GRAVEL 51 24 31 3 27

Laboratory research was conducted on both the Jos and Bauchi soils and it was observed that they obey the perfect compaction model described previously. A theoretical correlation was established between a strength index, CBR, and the OMC of the soils. university construction sites. The soil data is shown below: Matawal (1991) undertook shear strength studies, using Vane apparatus, on borrow pit specimens used on the

UNIVERSITY CONSTRUCTION SOILS Depth (m) 1.0 1.9 LL % 44.0 N. P. PL (%) 29.0 N.P. PI (%) 15.2 N.P. LS (%) 7.1 N.P.

Matawal (1991) in separate studies subjected northern Nigerian soils to shear strength, compressibility and permeability analyses. Again, the compaction curves were perfect confirmation of the pattern exposed in the micro-concept studies. 27

Balogun and Matawal (1997) undertook theoretical analytical studies on reinforcing strips of metal for sheet pile wall design. Matawal et al (1996) undertook studies on the response of tropical laterites to ground improvement techniques using cement stabilization.

SOILS USED FOR STABILISATION STUDIES SOIL SOURCE AND COMPOSITION (%) Gubi Campus Yelwa Campus Ningi Birshin Fulani GRAVEL 8 11 22 21 SAND 59 63 56 57 SILT 2 5 7 0 CLAY 31 21 15 22

These soils were stabilized with cement contents of 1.5, 3.0 and 6.0 percent, in addition to the homogenous specimen. Detailed consolidation, compaction, CBR and swell studies were conducted on the homogenous and stabilized samples. Matawal and Daspan (1997) undertook studies on the design, construction and cost-benefit of reinforced earth wall and concluded that the basic cost of materials was only 7.24 percent of the cost of an equivalent gravity wall. Metal strips were used for reinforcement with thin facing wall of aluminum foil. Matawal and Abba-Gana (1998) undertook studies to ascertain the effects of high tropical temperatures on concrete from Ashaka Type I cement. The results confirmed that high temperatures result in increased strength at early ages but lower strengths at late curing ages than low temperatures. The temperatures of experiments were 28, 32, 38 and 42oC for which the results totally confirmed the effects of temperatures on the strength of concrete i.e. that there is much long term benefit, by the grain in strength, in the use of low temperatures for concrete works. High temperatures merely encourage accelerated hydration process for the formation of tobermonite gel at the outset of concrete batching which gives high early strength but lower long term resistance.

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MEAN CUBE STRENGTHS FOR VARYING TEMPERATURES Mean Compressive Strength (N/mm2) at indicated ages 3 days 7 days 14 days 28 days 23.60 27.22 34.55 38.56 24.00 28.78 35.00 37.78 24.89 29.78 37.45 37.56 25.22 29.22 34.89 36.67

Curing Temperature C 28 32 38 42

o

MEAN CUBE STRENGTH AS RATIO OF 28 DAY STRENGTH AT ROOM TEMPERATURE Curing Temperature C 28 32 38 42

o

Ratio (%) of 28 day ­ 28oC strength at age: 3 days 7 days 14 days 28 days 61.2 70.6 89.6 100.0 62.2 74.6 90.8 98.0 64.5 77.2 97.1 97.0 65.4 75.8 90.5 95.1

Tricalcium silicate component of cement is responsible for high early strength of concrete and its reaction exothermic, favored by high temperatures. Matawal and Ajala (1966) tackle, explicitly, the influence of pore water pressures on the stability of slopes for which computer solutions are proffered for the associated problems. Matawal and Okere (2001) map out soils, ground water and rocks of the University campus using electrical resistivity methods (the terrameter utilizing the Schlumberger fixed array configuration). Matawal and Gboganiyi (2000) analyse six (6) specimens of soils from locations in Bauchi and Gombe, identifying them and undertaking laboratory measurements to ascertain some of their properties.

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SOIL SOURCE Yelwa, Bauchi Wunti, Bauchi Miri, Bauchi Gombe Town Kari, Bauchi Bayara, Bauchi

COLOUR Reddish brown Brown Dark brown Dark Light brown Reddish brown

LL % 25.8 26.3 29.6 36.4 33.1 28.3

PL % 22.8 21.6

PI % 3.0 4.7

SL % 4.8 5.0 7.1 10.4 7.9 10.0

IDENTIFICATION

Classification A-2-6 A-2-7 A-2-6 A-6 A-2-7 A-2-6

Laterite Laterite Laterite Black Cotton Laterite Laterite

16.1 13.5 21.1 15.3 14.0 19.1 14.3 14.0

Stabilisation studies were undertaken on the soils with cement contents of 0, 1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 percent based on which the linear relationship q = qo + K.c was derived for stabilized soils. Matawal and Enunoya (2001) have undertaken sensitivity measurements on ten (10) soil specimens from Delta, Edo, Bauchi, Gombe and Plateau states to ascertain their stability as foundation and construction material under a cycle of dry and wet conditions. SOIL SOURCE 1. Warri, Delta State 2. Warri, Delta State 3. Benin city, Edo State 4. Bauchi, Bauchi State 5. Bauchi, Bauchi State 6. Bauchi, Bauchi State 7. Dadin Kowa, Gombe State 8. Baure, Gombe State 9. NNPC, Gombe State 10. Fed. Low Cost, Jos, Plateau State Depth (m) 2.00 2.00 2.00 2.25 1.60 1.60 2.00 1.50 1.60 1.60 LL% 33.10 22.50 45.40 35.50 35.00 46.00 26.70 36.40 48.41 36.10 PI (%) 14.16 9.50 24.65 17.10 18.15 16.74 NP 15.56 22.50 13.74 GS 2.63 2.67 2.62 2.51 2.42 2.30 2.74 2.47 2.48 2.38

CLASSIFICATION

A-2-6 A-2-4 A-2-7 A-2-4 A-6 A-7-6 A-1-6 A-2-6 A-2-7 A-6

It is interesting to note the existence of black cotton soils in Bauchi State somewhere in Wunti (5) and Wuya dam (6) sites. The quality of water for human consumption and domestic applications had been of concern for many years particularly with incessant reports of the unacceptable water being consumed by many communities in the North East zone. This prompted the research by Matawal and Kulack 30

reported on earlier in Chapter 8. Following the discovery that even pipe borne water is not fit for human consumption as it fell below the WHO standards for drinking, an alternative method of purification was explored. The research describes, in detail, the use of ultraviolet radiation for disinfection of water particularly for commercial purposes and is recommended for household and small community applications in addition to the old age tradition of boiling. Matawal and Kulack (2001) bombarded all the poor water sources with ultraviolet rays and discovered that it resulted in total disinfection and had no known side effects. RESULTS OF WATER TESTS SUBJECTED TO ULTRAVIOLET TRADITION SOURCE Drinking well Flowing stream Borehole Pond Pipe mains Temp. (oC) 26 25 25 26 25 pH 7.2 7.1 7.1 7.1 7.0 BOD, mg/l 0.1 0.1 0.2 0.2 0.1 Colony per ml x 106 0.0 0.0 0.0 0.0 0.0 Total solids, TS, x 103, mg/l 0.502 0.502 0.502 0.508 0.002

The dissolved and suspended solids were reduced by filtration. The accounts given above are details of researches that are relevant to the theme of common civil engineering materials. There have been accounts of applications and results of tests on new material called spunbonded polypropylene, a fabric geotextile for construction on difficult grounds, by Matawal (1997, 1990 and 1991). Additionally, in the course of construction of civil engineering projects in which numerous materials were used in Abuja, Gombe, Bauchi, Warri, Jos, Yola, Maiduguri, Keffi, Makurdi and on rural roads, numerous experiences have been gained that are immensely valuable to the development and welfare of the society. NITEL resistivity tests undertaken in Bauchi, Jos, Maiduguri, Yola and Jimeta, and at Gombe were backed by direct borings and the gains were that the soils of these locations were known first hand. Many technical reports that will be useful to planners and practitioners have been produced while mapping of construction materials have been well defined particularly in North East Nigeria.

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11.0

CONCLUSION

It is a fact that common civil engineering materials are used by professionals, knowledgeable in the science of application of these materials, as well as non-engineers. The latter do not have much knowledge of the properties and characteristics of these basic materials that they can harness economically for building their homes, improving the environments in which they live and upstaging the organisations which they administer or serve. That is not all, water is so essential to life and yet in harnessing this resource for drinking, particularly, very little attention is often given to the quality and degree of disinfection of the commodity. It is in this regard that the micro-concepts enumerated and exposed in this lecture can be harnessed for the benefit of mankind whether privileged or underprivileged. The earth's soils, cement used in concrete construction, timber and, to a lesser extent, steel and asphalts are considered common enough materials to warrant the micro-details of this lecture. A little more knowledge on one or more of these materials could make the difference between dilapidated housing, roads and other infrastructure of our generation and a new generation of gratified Nigerians. 12.0 ACKNOWLEDGEMENTS

The author, Professor Danladi Slim Matawal, is particularly thankful to Professor A. S. Sambo, the Vice Chancellor of ATBU University, Bauchi, who initiated the inaugural lecture series and energetically propelled it. Appreciation is also made to the various compatriots in the university who have given encouragement and counsel when it was necessary. The family warmth and enticement to keep working on, when the spirit is willing but the body is weak, needs mention especially from my wife, Rose D. Matawal. And to those whose contributions came after writing the lecture: typists and those who will assist with teaching aids materials, projector and the like, I say thank you all. 13.0 1. 2. LIST OF REFERENCES Abba-Gana, M. (1997) "The effect of High curing temperatures on the strength of concrete prepared using Nigerian cements", B. Eng. Project report, ATBU, Bauchi. Atkinson, J. H. and Bransby, P. L. "The mechanics of soils", McGraw hill, Maidenhead.

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3. 4.

Balogun, L. A. (1991) "Effect of sand and salt additives on some geotechnical properties of lime-stabilised black cotton soils". The Nig. Engr. 26 (4), 15-25. Balogun, L. A. and Matawal, D. S. (1997). "New application of reinforced earth studies in the design and construction of retaining walls". Journal of Engineering Res. JER, 5 (1), 16-34

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Bhatia, H. C. (1967). "Soil-cement: a material of construction for road and airfield pavements". Tech. Paper 1, Building and Road res. Inst. Ghana. Bitrus G. P. Philips (1989). "Geotechnical properties and behavior of some stabilized Nigerian Lateritic soils," B. Eng. Project report, A.T.B. University, Bauchi. Brand, E. W. and Brenner, R. P. "Soft clay engineering" Elsevier scientific Company, Amsterdam. Bureau of Reclamation: "Concrete manual". Government printing Office Washington, D. C. Dugdak, D. S. and Ruize, C. "Elasticity for engineers". McGraw hill, London. Emesiobi, F. C. (2000). Testing and quality control of materials in civil and highway engineering". Blueprint Ltd. Port Harcourt. Hughes, B. P. "Limit state theory of reinforced concrete design". A Pitman International text, London. Ketkukah, T. S. (1990). "Long term effect of lack of curing on structural concrete", B. Eng. Project report, A.T.B. University, Bauchi. Lea, F. M. and Desch, C. H. "The chemistry of cement and concrete". Edward Arnold Pub., London. Matawal, D. S. and Enunoya, E. (2001). "Sensitivity evaluation of some tropical soils". Journal of Engineering Tech. And Ind. App. Vol. 2. Matawal, D. S. and Kulack, P. A. (2001). "Alternative methods to chlorination for disinfecting water: Case of ultraviolet radiation". Journal of Engineering Tech. and Ind. App. Vol. 2.

16. 17.

Matawal, D. S. and Okere, C. N. (2001). "Results of subsurface exploration using the terrameter". Journal of Engineering Tech. and Ind. App. Vol. 2. Matawal, D. S. and Gbobaniyi, M. M. (2000). "Theoretical relationships in cement stabilized soils". Journal of Engineering Tech. and Ind. App., 1 (1). 33

18.

Matawal, D. S. and Abba-Gana, M. (1998). (2), 297 ­ 303.

"Curing age versus concrete strength

relationships in tropical temperatures". 5th National Engineering Conference Series, 5 19. 20. 21. 22. Matawal, D. S. and Ajala, E. O. (1998). "Computer solutions for the Bishop methods of slope stability analysis", 5th National Engineering Conference Series, 5 (2), 276-281. Matawal, D. S. et al. (1996). Matawal, D. S. (1992) "Response of some tropical laterites to cement stabilization". 3rd National Engineering Conference Series, 3(1), 90-95. "Earth response of embankments in soft ground", National Seminar (Earthdam monito0ng and Management). Matawal, D. S. (1991a) "The compaction characteristics of some stabilized Northern Nigerian laterite soils". Permeability and shear strength response. The Nig. Engr. 26(2), 41-54. 23. 24. 25. Matawal, D. S. (1991b). "The use of field and laboratory methods for the shear strength analysis of tropically weathered soils". Journal of Engineering research, JER 3(1), 1-9. Matawal, D. S. (1990). "Compaction characteristics of some tropical laterite soils" OMC-CBR relationship, Journal of Engineering Research, JER 2(2), 1-9. Matawal, D. S. and Bhalla, S. N. (1990). "Some suggested areas of practical application of reinforced earth material on civil engineering projects". Conference on utilization of engineering in rural development, Nsukka. 26. 27. 28. 29. 30. 31. 32. Matawal, D. S. (1990). "Qualitative national development through standardization". Cont. of quality con. Soc. of Nigeria, Ile-Ife. Matawal, D. S. (1990). "The concept of effective stress as an engineering principle". Civil engineering seminar, 1.12.90, A.T.B. University, Bauchi. McCormac, J. C. "Structural analysis". In text education publishers, New York. Merritt, F. S. "Standard handbook for civil engineers". McGraw hill Company, New York. Mustafa, S. and Yusuff M. I. "A textbook of hydrology and water resources"; Jenas prints Co. Abuja. Neville, A. M. and Brooks, J. J. "Concrete technology". Longman Ltd. Singapore. Neville, A. M. "Properties of concrete". Pitman books, London.

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33. 34. 35. 36. 37. 38. 39. 40. 41. 42.

Ola, S. A. (1978). "The geology and geotechnical properties of the black cotton soils of North-Eastern Nigeria". Engineering Geology, Vol. 12, 375-391. Ola, S. A. (1974). "Stabilisation of cement in Nigeria". Nigerian Journal of Engineering 1(1), 19-30. Ononuju, E. M. (1988). "Effects of cement stabilization of soils for highway "Soil cement laboratory handbook", Portland cement construction". B. Eng. Project report, A.T.B. University, Bauchi. Portland Cement Association. association, 33 West Grand Aven., Chicago, IL, 60610. Scott, C. R. "Soil Mechanics and Foundations". Applied Science Pub. Ltd, London. Scott, J. S. "The Penguin dictionary of civil engineering". Harmondsworth. Smith, G. N. "Elements of soil mechanics for civil and mining engineers". Granada Pub. London. Stephens, J. H. "The Guinness book of structures". Guinness superlatives Ltd, London. Wajahat, M. N. (1988) "Growth of comprehensive Strength of Concrete under adverse effect". B. Eng. Project report, A.T.B. University, Bauchi. World Health Organisation, WHO. "International Standards for drinking water", WHO Geneva, Switzerland. Penguin books Ltd.

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ABOUT THE AUTHOR Professor (Engr.) DANLADI SLIM MATAWAL B. Eng. (ABU), M. Sc. (London), DIC, Ph.D., C. Eng., MNSE, MNIM, MSESN Professor of Civil Engineering Born on Sunday, October 30, 1955, i.e. 46 years ago, in Bokkos, Bokkos LG of Plateau State of Nigeria, Professor Matawal had his primary school education at the N. A. Primary School in Bokkos from 1963 to 1968. He was born to Mama Undong Matawal (mother) and Pa Yakubu Matawal Yakwal (father, then adult education teacher in the defunct pankshin N.A.). From primary school, young Matawal proceeded to the Government College at Keffi in 1969 from where he passed out, in 1973, with a WASC division ONE with excellent (E1) in Mathematics, Physics and Chemistry. His best results were usually in the three subjects because he never paid a lot of attention to his other subjects like Geography, English and Bible Knowledge in which he nonetheless obtained credit 6 scores. He salvaged the Benue Plateau State prize for the best beginner of Technical drawing in 1972. He proceeded to Ahmadu Bello University at Zaria in 1974 where he spent some one and half years in the School of Basic Studies in the same class with many useful colleagues today. In September 1975, he registered for Civil Engineering in the same institution from where he graduated, in 1978, with a FIRST class honors degree earning the final year spectacular performance prize. He studied, on the Commonwealth of nations' scholarship scheme, M.Sc. and DIC at the Imperial College of the University of London where he had special departmental call for the best examination score in the course `Foundation engineering' in 1981. He registered for the Ph.D. in 1989 and was successfully awarded the advanced degree in Civil engineering in 1992. Professor Matawal has practiced mostly in the area of Structural engineering but has had vast and sufficient research and practical experience in Foundation, Soil Mechanics, Water and transportation engineering. He worked as consultant in the field for five (5) years and was one of 36

pioneer young consultant engineers for the city of Abuja in 1981.

He has designed and

supervised construction projects in Nigeria in all disciplines of Civil engineering. He has also served on various Government, University, Polytechnic and Voluntary agency boards, task forces, Visitation panels, Accreditation teams/panels and technical groups. His last major national assignment has been as Chairman (Civil engineering team) of the UNESCO-NIGERIA technical revitalization program for technical-vocational education in Nigeria from April to September 2001. He has lectured and researched in the University (at A.T.B. University, Bauchi) from 1987 and was promoted to the Chair of Professor of Civil Engineering on October 1, 1999. He is happily married with seven (7) vibrant children.

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