STRUCTURAL CHARACTERISTICS OF LATERIZED CONCRETE AT OPTIMUM MIX PROPORTION

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1 STRUCTURAL CHARACTERISTICS OF LATERIZED CONCRETE AT OPTIMUM MIX PROPORTION N.N. Osaebe 1 an T.U. Nwakonobi 1 Department of Civil Engineering University of Nigeria, Nsukka. Department of Agricultural Engineering University of Agriculture, Makuri. ABSTRACT The astronomical increase in prices of materials for builing construction in Nigeria is causing a lot of concern, creating nee for research into inigeneous materials as alternatives in builing an rural infrastructures. Research efforts are irecte towars enhancing the use of locally an reaily available material such as lateritic soils for the construction of low-cost but effective wellings, farm structures an other rural infrastructures. The knowlege of characteristics an performance of laterize concrete is a prerequisite to the accurate esign of structures built of this material. Some of the structural characteristics of laterize concrete are stuie at the preetermine optimum mix proportion an that use for general reinforce cement concrete work. The results show that the values obtaine for elasticity Moulus, rigiity Moulus, flexural strength, poisson s ratio are higher at optimum mix proportion than at the conventional mix ratio in cement concrete. Only ensity value is lower at the former mix ratio than the latter. Key Wors: Laterize concrete; lateritic soils; structural characteristics 1. 0 INTRODUCTION Lateritic soils are wiely use as a construction material in Nigeria an other uner-evelope an eveloping countries of the worl. In aition to Mu walls, brick masonry (rie or burnt type) are mae from lateritic soils in both rural an urban areas of the country, Nigeria. Accoring to Lasis an Osunae [1], the use of laterite to replace san component of concrete either wholly or partially, is becoming wiesprea among the lowincome earners for builing construction. The utilization of laterites enables the provision of low-cost houses an other rural infrastructures. However, laterites have not been extensively use in constructing meium to large-size builing structures. This is probably ue to lack of aequate ata neee in the analysis an esign of structures built of lateritic soils. To improve the utilization of this locally available materials, investigations into the properties of both stabilize an unstabilze lateritic soils have been carrie out. Some of the basic engineering properties of laterize concrete have been etermine but only at specific conitions. Osunae et al [] have stuie shear an tensile properties of unreinforce laterize concrete at specific curing ages. Ductility, shear an tensile properties of fibre-reinforce 1

2 STRUCTURAL CHARACTERISTICS OF LATERIZED CONCRETE AT OPTIMUM MIX PROPORTION 13 laterize concrete have been etermine by Osunae an Oguneko [3]. The effect of chemical amixture on the compressive strength of lateritic soil materials for masonry units has been investigate [4]. The compressive strength as affecte by types an sizes of coarse aggregates have been stuie [5]. The effect of grain size an optimum moisture content on the cement-stabilize an unstabilize lateritic soils have also been stuie [6]. Lasis an Osunae [6] reporte that the strength properties of lateritic soil is a function of probable formation processes an the source where they are collecte. With the aforementione research work on laterize concrete, ata on some structural characteristics such as elasticity moulus, rigiity moulus an poisson s ratio is not foun in literature. Only limite information on flexural strength of laterize concrete is available. In the recent stuy by Nwakonobi (005) the optimum mix proportion that will prouce maximum strength value of laterize concrete was etermine. The objective of this stuy is to etermine some of the structural characteristics of laterize concrete at both optimum mix proportion an that use for general reinforce cement concrete work..0 MATERIALS AND METHOD.1 Sources of Material The lateritic soil for this investigation was collecte from a borrow-pit at Nsukka in Enugu State, Nigeria. The coarse aggregate use was crushe granite of igneous origin with a size range of Orinary Portlan Cement the properties which conform to the British Stanar BS [8] part of 1970 was use in this stuy.. Sample Preparation The lateritic soil was sieve so as to exclue the clay content as well as the coarse aggregate contents of lateritic soils. The range of size use was 0.3 to The size ranges of coarse aggregates were chosen in compliance with BS [9] part 18:1983 that the maximum size of coarse aggregate shoul not excee one-thir of the smaller imension of the concrete member. For this stuy, the maximum size use was 14 an is less than one-thir of 100 the smallest imension of the test specimen..3 Batching an Mixing of Specimens The pre-etermine optimum mix proportions of 1:1: of cement, laterite an gravel at a water cement ratio of was use for this report Nwakonobi [7]. The pre-etermine concrete mix proportion of 1::4, which is use for general reinforce cement concrete work, was also use for this report [10]. The water-cement ratio of use for this mix proportion of 1::4 was aopte from the optimization stuy carrie out by Nwakonobi [7] for a workable mix. Batching was by weight using Avery weighing scale. Different mixtures of cement, lateritic soil an gravel were prepare an worke manually using shovel to stir. The working process involve the graual aition of preetermine quantity of water to the mixtures alreay obtaine an a continuous stirring with a shovel until a workable mix was obtaine..4 Flexural Strength Test Beam specimens of size were moule an teste for flexural strength. The specimens have a slenerness ratio of 5. The making, curing an the metho of test were in accorance with BS [9]. Three replicate samples were prepare for each of the laterize concrete mix proportions use. A total of six beam NIGERIAN JOURNAL OF TECHNOLOGY, VOL. 6 NO.1, MARCH 007

3 14 N.N. Osaebe an T.U. Nwakonobi specimens were cast an teste. Each specimen was mae by filling each moul in three layers. Each layer was compacte manually by using 5 iameter ro to eliver 150 strokes on the layer. The specimens were water-cure at ambient temperature an to stanar curing age of 8 ays. For the flexural strength of the beam specimens, the thir-point loaing metho was use (Fig. 1). Loaing roller at thir point span b Supporting roller 3 5 Fig. 1: Thir-point Loaing Arrangement Supporting roller The beam was simply supporte over a span 3 times the beam epth on a pair of supporting rollers. Two aitional loaing rollers were place at the thir points between the supports iameter ro to eliver 150 strokes on the layer. The specimens were water-cure at ambient temperature an to stanar curing age of 8 ays. For the on top of the beam. The loa was applie without shock at a loaing rate of 10 KNmin -1. The flexural strength is.5 Moulus of Elasticity Cyliner specimens of size 100 in iameter an 00 in length were mae, cure an store in accorance with BS [9]. Three replications of each of the two ifferent mix ratios use were mae. Therefore, a total of six cyliner specimens relate to the loa an cross-sectional area as follows: F tb = L b (1) N where, F tb = flexural strength, ρ = maximum total loa, N L = length of the beam specimen, = epth of the beam, b = with of the beam, were cast an teste. All the specimens were teste in moist conition i.e. ieiately after removal from the water tank at the curing age of 8 ays. The test specimen was place centrally in the compression machine an strain gauges carefully fixe to measure NIGERIAN JOURNAL OF TECHNOLOGY, VOL. 6 NO.1, MARCH 007

4 STRUCTURAL CHARACTERISTICS OF LATERIZED CONCRETE AT OPTIMUM MIX PROPORTION 15 strain in both lateral an longituinal irections (Fig. ). The basic loa of 0.5 N/ was applie an the ial/strain gauge reaings taken in both lateral an longituinal irections. The loa was increase at a constant rate of 1 N/.s until the loa equal to one-thir of the preetermine compressive strength of laterize concrete was reache as upper loa [7]. The loa was maintaine for 60 secons an strain reaings recore P where, E LC = moulus of elasticity of laterize concrete, N σ a = the upper loaing stress in N (σ a = F c ) 3 σ b = the basic loaing stress (ie. 0.5 N ) = mean strain uner the upper loaing a stress = mean strain uner the basic stress b F c = compressive strength of laterize concrete..6 Poisson s Ratio The lateral strain accompanying the axial strain to the applie axial compressive stress was recore in static moulus of elasticity tests BS [9]. The poisson s ratio, μ, is calculate as the ratio of lateral strain L to longituinal strain, C L (3) c P Fig. : Deformation of Test Cyliner uner axial compression within 30 secons. One aitional preloaing cycle was carrie out by using the same loaing an unloaing rate. The specimen was reloae to upper loaing level at the specific rate an the strain reaings recore within 30 secons. The static moulus of elasticity in compression was estimate using the formula: Δ E LC = = a b..() Δ a b.7 Moulus of Rigiity The moulus of rigiity of laterize concrete was calculate utilizing experimental values for elasticity moulus, E LC an poisson s ratio μ, in the equation: G = E ( 1).(4).8 Density Cube specimens of size 150 x 150 were prepare for the ensity etermination. The preparation of the cubes was one in accorance with BS [9]. Each specimen was mae by filling each moul in three layers an compacting manually with 5 iameter ro. On each layer, 35 strokes were elivere. NIGERIAN JOURNAL OF TECHNOLOGY, VOL. 6 NO.1, MARCH 007

5 16 N.N. Osaebe an T.U. Nwakonobi Demouling was performe in accorance with BS [9]. The specimens were then submerge in a water tank for using Avery weighing scale. The ensity was estimate from the relation: ρ = V m where; ρ = ensity of har laterize concrete, kg/m 3 m = mass of har laterize concrete cube, kg curing. The cubes were cure for 8 ays. The har laterize concrete cube after removal from curing tank was weighe V = volume of the cube specimen, m 3 3. RESULTS AND DISCUSSION The results of eterminations of physical an structural characteristics of laterize concrete at optimum mix proportion as well as conventional mix ratio use for cement concrete are shown in Table 1. Table 1: Structural Characteristic of Laterize Concrete Material Property Mix Ratio 1:1:: ::4: Density (kg/m 3 ),400,474 Flexural strength (N/ ) Compressive strength (N/ ) 7 0 Moulus of Elasticity (N/ ) 18, ,163.9 Moulus of Rigiity (N/ ) 7, ,199.9 Poisson s ratio It is clearly seen that the values obtaine for flexural strength, compressive strength, young moulus, shear moulus an poisson s ratio are higher for the optimum mix ratio of 1:1: at water cement ratio of when compare with those of the mix ratio 1::4 at water cement ratio of Only ensity is lesser for te former mix ratio than the latter. The results in the above Table 1 inicate that the optimum mix ratio of 1:1::0.650, which has the highest strength, reflects on the quality of other properties of the laterize concrete material. Thus, results in Table 1 provie ata neee for the accurate analysis an esign of structures such as silos, water reservoirs, etc built of laterize concrete. 4. CONCLUSIONS The ata provie on the structural characteristics of laterize concrete at optimum mix proportion in this stuy can be aopte in the analysis an esign of structures built of laterize concrete. The optimum mix which will have long lasting effect ue to aequate strength shoul therefore be aopte particularly for heavily loae laterize concrete structures such as silos, reservoirs, etc. However, mix ratio of 1::4:0.791 may be aopte for the construction of low cost housing an other rural infrastructure. NIGERIAN JOURNAL OF TECHNOLOGY, VOL. 6 NO.1, MARCH 007

6 STRUCTURAL CHARACTERISTICS OF LATERIZED CONCRETE AT OPTIMUM MIX PROPORTION 17 REFERENCES 1. Lasis, F an J.A. Osunae. Laterize Concrete Masonry as an alternative in builing an rural Infrastructures. Proceeing of International Conference on Structural Engineering. Ghana, Seam, 1990, pp Osunae, J.A. P.O. Aeyefa, an F. Lasis, Shear an Tensile Properties of Unreinforce Laterize Concrete. Ife, Journal of Technology, Vol. No. 1, 1990, pp Osunae, J.A. an O.F. Oguneko. Fibre-reinforcements as they affect Shear an Tensile Strengths of laterize concrete. International Journal for Housing Science an its Application, USA., 199, pp Osunae, J.A. Effect of Chemical Amixtures on the Compressive Strength of lateritic soil material for masonry units. Masonry International Journal. (In press). 5. Osunae, J.A. The Compressive Strength of Laterize concrete. The Effect of Types an sizes of coarse Aggregates. Masonry InternationalJournal Bulletin, Vol. 7, No. 1, 1993, pp Lasis, F an J.A.Osunae. Effect of Grain sizes on the strength of cubes mae from lateritic soils. Builing an Environment. Great Britain Nwakonobi, T.U. Analysis an Design of laterize concrete Cylinrical Shells for Farm Storages. A Thesis submitte to the Department of Agricultural an Bioresources Engineering University of Nigeria, Nsukka BS 1: part. Metho of Testing Concrete, British Stanars Institution, BS 1881: Parts III, : Testing Concrete. British Stanars Institutions, Reynols, C.E. an J.C. Steeman. Reinforce concrete esigner s hanbook. A View point Publ., 9 th Eition, 1981, pp NIGERIAN JOURNAL OF TECHNOLOGY, VOL.6 NO.1, MARCH 007