Some Flexural Behaviour of Rectangular Concrete Beams with Mound Soil as Partial Substitute for Ordinary Portland Cement

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1 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(4): Scholarlink Research Institute Journals, 2013 (ISSN: ) jeteas.scholarlinkresearch.org Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(4): (ISSN: ) Some Flexural Behaviour of Rectangular Concrete Beams with Mound Soil as Partial Substitute for Ordinary Portland Cement 1 O.U. Orie and 2 E. O. Eze Department of Civil Engineering, University of Benin, Benin City, Nigeria. Corresponding Author: O.U. Orie Abstract The paper determined the flexural characteristics of rectangular concrete beams when mound soil is used as a partial substitute for cement in a concrete mix ratio of 1:2:4 representing cement, fine aggregate and coarse aggregate respectively. The cement in the mix was substituted by bound soil at percentages ranging from 0 36% of the cement. For the purpose of the experiment the water/cement ratio was kept constant at 0.6. Granite from Ifon in Ondo, Nigeria of maximum average particle diameter of 14mm was used as coarse aggregate. The fine was Okhuahe river sand and the mound soil was randomly sourced from the habitat of common specie of Termites in Iyekeogba area of Benin City. The geotechnical properties of the materials were determined. Concrete beams measuring 100mm x100mm x 400mm were cast, cured and tested for flexural strength using the Universal Testing Machine after 28 days. The results showed that an increase in percentage content of mound soil caused the beams to behave plastically. The 0% substitute of cement control beams showed a failure load of 2.17kN, modulus of rupture 1.30N/mm 2 and flexural rigidity 4.82x10 9 N/mm 2. The optimal 8% substitute produced a failure load of 5.3 kn, modulus of rupture 3.18N/mm 2 and flexural rigidity 8.51x10 9 N/mm 2. The paper concludes that about 8% by mass of mound soil can be used to enhance the flexural characteristics of concrete beams. Rectangular concrete beams are commonly encountered in structures and mound soil has shown potentials as construction material. Keywords: cement, substitution, concrete, flexure and mound soil INTRODUCTION Concrete is a construction material composed of cement (Portland cement), aggregate (generally a coarse aggregate such as gravel limestone or granite), fine aggregate (sand), water and sometimes mineral or chemical admixtures. Concrete is generally known to be a good material in compression but poor in tension or flexure. Concrete being a composite material is relatively expensive and modern research is not only geared towards improving its cost but also its qualities. Mound soil is a natural heap of lateritic soil which may have originated as a result of some biological or bacteriological actions. It is a soil devoid of any decayed vegetable material. Beams are horizontal structural elements which help in resisting and transmitting loads to columns. Beams are subjected to flexural loads induced by moments during service. Concrete has been reported to have qualities that make it a construction material that may last for life in terms of its durability (David and Galliford, 2000). Orie and Osadebe (2010) have optimized the amount of mound soil required in a concrete mix to give a desired concrete compressive strength. Ecological reports say that Mound soils are built of earth particles which are cemented together forming hard brick-like materials resistant to weathering and 618 difficult to pick (Adepegba, 1980). The soil varies in properties depending on the earth formation of its location. The property of mound soils has been given by Felix et al (2000) and is presented in Table 1. The soil has been shown to possess some cementitious properties and hence a good construction material (Felix et al. 2000; Orie and Osadebe, 2010). This property of mound soil has been attributed to its chemical composition.the chemical analysis of the mound soil from Iyeke-Ogba is shown in Table 2. The table showed that the material has calcium a predominant component of cement. The properties of Portland cement (Neville, 2002) are given in Table 3. The calcium component of the mound soil oxidizes into its carbonate forms, thereby playing some roles as in the hydration of cement in concrete. Recent research tends towards finding alternatives for some of the components of concrete, especially cement. Some of these researches are with a view to reducing cost (Orie, 2008a; Orie, 2008b; Osarenmwinda and Awaro, 2009) and others to achieving some desired mechanical properties (Orie and Anyata, 2008). Ashour and Wafa (1993) investigated the influence of fiber addition on ultimate load, crack propagation, flexural rigidity, and ductility of concrete beams. They reported that the addition of steel fibers enhanced the strength and

2 increased the ductility and flexural stiffness of the beams. Dobie and Henning (1975) determined the effects of utilizing lignite fly ash as a substitute for Portland cement and obtained the compressive and flexural properties of the concrete. The results showed that the incorporation of lignite fly ash increased the strength and durability of the concrete. Balaguru and Dipsia (1993) investigated the workability and the behaviour under compression, splitting tension, flexure, and shear of fiber reinforced high strength semi lightweight concrete. They used Silica fume and high-range water-reducing admixtures to obtain the high strength. The lightweight aggregate used was made of expanded shale. The primary independent variables were fiber content and fiber length. Their results showed that silica fume can be successfully used to obtain high strength and that the brittleness of silica fume concrete can be overcomed by using fibers. The addition of fibers provided a significant increase in Young's modulus, splitting tensile, and shear strengths. Bentur and Goldman (1989) characterized high strength silica fume concretes from the point of view of heat generation, shrinkage and sensitivity to curing, and compared their performance with that of concretes made of Portland cement. It was found that the presence of silica fume resulted in a marked increase in strength and low heat liberation. Table 1. Properties of Mound Soils Characteristics (1) Percentage passing No. 200 BS sieve Liquid limit Plastic limit Plasticity index Linear shrinkage AASHO classification Specific gravity Colour (After Felix et al, 2000) A (2) A Light brown Samples B (3) A Brick red C (4) A Light brown Table 2. Chemical Analysis of Iyeke- Ogba Mound Soil Component ph Clay Silt Sand Fe Zn S0 4 - Ca Mg K CEC H + +Al 3+ % % % mg/kg mg/kg Unit Fraction Key: CEC = Cation Exchange Capacity, Meq = Milli equivalent (After Orie and Osadebe 2010) Table 3. Composition of Portland cement Oxide CaO SiO 2 Al 2O 3 Fe 2O 3 MgO Alkalis Content (After Neville 2002) SO3 (Na 2O 3) Naik and Singh (1991) developed structural grade concrete containing high-volumes of ASTM Class C fly ash with cement concrete proportioned to have 28-day compressive strength of 40 N/mm 2.The effect of using solid waste materials as substitutes for fine aggregates on cementitious concrete composites have been examined (Ibrahim et al. 1996). The work concluded that, up to 20% granulated waste materials such as plastics, glass, and fiberglass can be used in cementitious concrete composites without seriously hindering its mechanical properties. It suggested that a further study should be carried out on the economic aspects involved in such research, the possibility of increasing the volume fractions beyond the range of 20% and the possibility of using other types and forms of waste materials in cementitious concrete composites. In the present paper the potentials of using mound soil as a construction material has been extended to structural elements. 619 MATERIALS AND METHOD The major tests carried out in the study were; Specific gravity, Bulk density, Compaction, Slump and compacting factor (consistency and compatibility test of workability) as well as flexural strength test along side with deflection of beam under point load. The flexural strength test was carried out on 28th day hydration period for each mix proportion. Sieve Analysis was carried out on the aggregates which were; granite from Ifon in Ondo State and Okhuahe river sand from Edo State both in Nigeria. The mound soil was randomly sourced from the habitat of common specie of termites in Iyeke-Ogba area of Benin City. It was brick red in Colour. The mound soil and aggregates were dried in open air at room temperature in the laboratory until they were dried, before being used for the experiments. The mound soil was pulverized using mortar and pestle after which sieving was carried out on it. The resultant material was silty. The apparent specific gravity (G s ) of the coarse aggregate was determined in accordance with BS.1377: Part 2, 1975 Test A. The loose and compacted densities, l b of the aggregates were determined to BS812. Compaction test was carried out for mound soil. Batching of the materials was by weight to a standard mix ratio of 1:2:4:0.6. Mixing was carried out by means of a power operated mixer. A slump test was carried out on the fresh concrete to

3 measure the effect of the mound soil on its consistency. The compaction factor, C f was computed as; ( Wp We ) Cf (1) ( W W ) f e where, W p = weight of partially compacted concrete and mould, W f = weight of fully compacted concrete and mould and W e = weight of empty mould. The beams samples measured 100mm x100mm x 400mm and were tested to BS Part 5, 2002, using the universal testing machine (UTM). Measurement of the deflections corresponding to the increments in load was done using a dial gauge fixed below the samples. This was done for all mixes at age of 28 days of hydration at 22 0 C. It was observed that the beams failed by crack initiation at the bottom fibre, the crack propagating toward the upper fibre as the load increased. The modulus of rupture, M R and flexural rigidity, EI were determined as; 3PL M R (2) 2 2 bd 2 PL EI (3) 48 Ymax where, b = 100mm, d = 100mm, L = 400mm, P = failure load and Y max = deflection at failure. Table 5. Mechanical Properties of the Mound Soil Concrete and Beam Properties Mound Soil Content Compacti on Factor Slump (mm) Flexural Strength (N/mm 2 ) Flexural Rigidity (GNmm 2 ) Percent passing, % Sand 0 Silt Sand Gravel Fine Medium Coarse Fine MediumCoarse FineMediumCoarse Particle size, mm Figure 1. Grain size distribution curves of the coarse and the fine aggregates Coarse aggregate RESULTS AND DISCUSSION The results of the tests carried out on the fresh and hardened concrete are presented as tables and figures. Results of the sieve analysis of the coarse and fine aggregates are plotted in Fig. 1. The curves show uniformly graded aggregates. The relationship between the slumps as a percentage of mound soil in the mixes is plotted in Fig. 5 described the plasticizing effect of mound soil on concrete. The figure showed that there was a decrease in slump and hence corresponding decrease in workability with increasing percentage mound soil content. The figure showed that beyond the 36% replacement of cement by mound soil, the standard mix became unworkable at the constant water/cement ratio. This relationship is also observed in the results of the compaction factor in Table 5. Table 4. Physical Properties of the Aggregates Property Aggregate Coarse (Granite) Fine (Sand) Specific gravity Bulk Density (kg/m 3 ) Loose Compacted Moisture Content

4 The flexural strength and flexural rigidity are plotted as a function of the amount of mound soil in the concrete in Figs. 2 and 3 respectively. Fig. 2 revealed that there was a variation in strength with percentage increase in mound soil content. This variation however, showed that flexural strength decreased with an increase in percentage mound soil beyond 8% at which an optimal flexural strength of 4.0 N/mm 2 was attained. Fig. 3 showed that a maximum flexural rigidity of 21x10 9 N/mm 2 was attained at a mound soil content of 12%. The dependence of the maximum deflection of the concrete mixes on the mound soil content is shown in Fig. 4. Within the limits of the range of the tests of the experiments, Fig. 4 showed that there was a wavelike relationship on the positive side of the graph. The plot has stopped at the 36% mark because beyond this point, the resulting concrete became unworkable and would have required more water in the mix and this would have been outside the scope of the study. flexure, such as beams. Its application should however not 8% exceed by weight of the cement, and adequate water cement ratio should be used for good workability. LIMITATION OF THE STUDY A limitation of the study was the non-availability of standard equipment for the pulverization of the mound soil for which the local mortar and pestle was used. This made the process cumbersome and time consuming. REFERENCES Adepegba, D The prodigies of structural engineering. Lagos University Press, Nigeria. Ashour, S. A. and Wafa, F. F Flexural behavior of high-strength fiber reinforced concrete Beams. ACI Structural Journal, 90(3), Balaguru, P. N. and Dipsia, M. G Properties of fiber reinforced high-strength semilightweight concrete. ACI Materials Journal, 90(5), CONCLUSION Mound soil is a good concrete admixture for enhancement of flexural characteristics when used as a partial substitute for cement. This will be advantageous in structural element subjected to 621 Bentur, A. and Goldman, A Curing effects strength and physical properties of high strength silica fume concretes. Journal of Materials in Civil Engineering, 1(1), David, J. and Gallifird, N Bridge construction at Huddersfield narrow canal. Concrete, 34(6), Dobie, T. R. and Henning, N.E Lignite fly ash as a partial replacement of Portland cement in concrete. Report OSH gov/energy adaptation prdt. Felix, F. U., Alu, O. C., and Suleiman, J Mound soil as a construction material. Journal of Materials in Civil Engineering, 12(3), Naik, T. R. and Singh, S. S Superplasticized high-volume fly ash structural concrete. Procs. ASCE Energy Division Specialty Conf. on Energy, Pittsburgh, PA, Neville, A. M and Brooks, J.J Concrete technology. Pearson Education Pte Ltd., India. Osarenmwinda, J. O. and Awaro, A. O The potential use of periwinkle shell as coarse aggregate for concrete. Advanced Materials Research, 62-64, Orie, O. U. 2008a. Recycled waste concrete: an alternative to natural mineral aggregates. Journal of Science and Technology Research, 7(7),

5 Orie, O. U. 2008b. Compressive strength of hollow Sandcrete blocks with laterite soil as partial replacement of cement. Journal of Engineering Science and Applications, 5(1&2), Orie, O. U. and Anyata, B. U Effect of water/cement ratio on the compressive strength of mound soil concrete. Jornal of Civil Environmental System Engineering, 9(1), Orie, O. U. and Osadebe, N. N Optimization of the compressive strength of five-component concrete mix using Scheffe s theory a case study of mound soil concrete. Journal of the Nigerian Association of Mathematical Physics, 14, Orie, O. U. and Osadebe, N. N. (2010) The Determination of Some Mechanical Properties of Scheffe s Optimized Mound Soil Concrete, Journal of the Nigerian Association of Mathematical Physics, Vol. 17, pp