PARTIAL REPLACEMENT

This research investigates the suitability of cow bone ash (CBA) as a partial replacement for ordinary Portland cement (OPC) in concrete production, with the aim of reducing cement consumption, lowering environmental impact, and promoting sustainable waste management practices in Nigeria. Cow bones, which constitute a major agricultural waste product, were processed into ash through controlled calcination and evaluated for their potential pozzolanic contribution in concrete. The study focused on assessing the effects of varying percentages of CBA on the fresh and hardened properties of concrete, particularly particle size distribution, workability, strength development, and durability. To achieve the objectives of the study, concrete mixes were prepared using a nominal mix ratio of 1:2:4 and a constant water–cement ratio of 0.50. Cow bone ash was used to partially replace cement at replacement levels of 0%, 5%, 10%, 15%, 20%, and 25% by weight. Laboratory tests were conducted in accordance with relevant British and ASTM standards. These tests included sieve analysis to determine particle size distribution, slump test to assess workability, compressive and flexural strength tests at curing ages of 7, 14, and 28 days, and water absorption tests to evaluate durability characteristics. The results showed that concrete containing 5–10% cow bone ash exhibited improved performance compared to the control mix. At these replacement levels, improved particle packing and additional calcium silicate hydrate (C–S–H) formation led to enhanced strength and reduced water absorption. However, workability decreased with increasing CBA content due to higher water demand, and replacement levels above 15% resulted in reduced strength and increased water absorption caused by higher porosity and unreacted ash particles. In conclusion, cow bone ash can be effectively used as a supplementary cementitious material at replacement levels of up to 10–15%, offering an environmentally friendly and cost-effective alternative to conventional cement in concrete production.

This study investigated the effect of partially replacing Ordinary Portland Cement (OPC) with eggshell powder (ESP) in concrete production as a sustainable approach to reduce cement consumption and utilize agricultural waste. The aim of the study was to evaluate the performance of concrete containing eggshell powder as a partial replacement for cement. The specific objectives were to determine the workability of concrete containing varying proportions of ESP, evaluate its compressive strength, assess its water absorption capacity as an indicator of durability, and identify the optimal ESP replacement level that yields the best concrete performance. The experimental study was conducted by preparing concrete mixes with 0%, 5%, 10%, 15%, and 20% replacement of cement with eggshell powder. Waste eggshells were collected, cleaned, dried, ground into fine powder, and sieved before use. Concrete cubes were cast and cured in water, after which several laboratory tests were performed. Workability of the fresh concrete was determined using the slump test, compressive strength was measured at 7, 14, and 28 days using a compression testing machine, and water absorption tests were carried out at 28 days to evaluate the durability-related properties of the hardened concrete.The results showed that workability slightly increased at 5% ESP replacement, indicating improved particle packing within the mix, but gradually decreased at higher replacement levels due to increased water demand of the fine ESP particles. The compressive strength of the concrete improved at moderate replacement levels, with the optimum strength obtained at 15% ESP replacement after 28 days of curing, while further increase in ESP content led to a reduction in strength. The water absorption values for all concrete mixes were below 10%, indicating that the inclusion of ESP did not adversely affect the durability of the concrete. Based on the findings, the study concluded that eggshell powder can effectively replace cement up to 15% without significantly compromising the essential properties of concrete. It is therefore recommended that ESP be considered as a sustainable partial cement replacement material in concrete production, particularly for applications such as pavements, floor screeds, and foundations, where environmentally friendly and cost-effective construction materials are desirable

This work investigated the possibility of using waste concrete materials as partial replacement for coarse aggregates in concrete work and some of the properties of Recycled concrete aggregates. The Recycled concrete aggregate used was gotten from waste samples in the laboratory of the Department of Civil/Structural Engineering of the University of Benin. These samples were dried and crushed, they were used to replace Natural Coarse Aggregate under different percentage of 0%, 20%, 40%, 60%. The test done was Aggregate Impact Value (AIV), Sieve Analysis, Slump Test, Compressive Strength and Split Tensile Strength Test. With a total of 36 cubes and 36 cylinder made, curing age of 7, 14 and 28 days were used to investigate the strength of the concrete made. The results obtained show that the aggregate impact value of Natural coarse Aggregate was 27.43% and that of Recycled concrete Aggregate 35%. Slump value for 0%, 20%, 40%,60% are 40.50, 30.50, 30.30, 30.70mm. The compressive strength test of 0% is 23.30N/mm2 at 28 days, 20% is 28.11 N/mm 2 at 28 days, 40% is 20.10N/mm2 at 28 days, 60% is 26.96 N/mm2 at 28 days, and the split tensile strength of 0% is 2.69 N/mm2 at 28 days, 20% is 2.75 N/mm2 at 28 days, 40% is 1.78 N/mm2 at 28 days, 60% is 2.18 N/mm2 at 28 days. It was seen that Recycled concrete aggregate (RCA) decreases with increase in percentage of replacement and the maximum or optimum strength was obtained at 20% replacement.

The aim of this project is to determine the effects metakaolin powder has on the mechanical properties of concrete when partially replaced at various percentages (15%, 20% and 25%). The idea behind this study is to assess if metakaolin powder can serve as a suitable substitute for sand as a fine aggregate in terms of responses to various tests. This study seeks to serve as a guide for future research in this field. It also serves to answer the question of why seek substitutes for fine aggregate at all.The tests required for accomplishing this experiment’s objectives are the compressive, flexural, slump and density tests, to determine the compressive strengths, flexural strengths, workability and density, respectively, of various samples been tested. Conventional concrete samples are cast and compared to partially replaced concrete to analyze the effects on concrete. The results for various tests differ showing rises and falls in strengths, slumps and densities. These results are then compared using tables and charts, from which a conclusion is drawn. The conclusion drawn for workability is that it has a low workability due to the pozzolanic nature of metakaolin powder and its reaction to cement and for the strengths, it is ascertained that concrete samples experience an increase in strength at 15% of partial replacement followed by a decrease at 20% and an increase at 25% indicating a possibility of later strengths at higher percentages but more so at longer periods of curing.