COARSE AGGREGATE

The need to reduce the increasing demand for crushed granite as coarse aggregate as well as the need to safeguard the environment from degradation has given rise to various researches on alternative materials that can serve the same purpose while minimizing environment hazard. The suitability of waste ceramic tiles as coarse aggregate in concrete and ascertain its strength against normal crushed granite were assessed. Crushed waste ceramic tiles was mixed with crushed granite stones as partial replacement for concrete. A mix ratio of 1: 2: 4, with attached mix design in appendix plate 1, for C20 concrete is produced with (0, 10, 20, 30, and 40) percent volume ceramic waste aggregate replacement for crushed granite at a constant water-cement ratio of 0.5. Concrete cubes of size 150mm x 150mm x 150mm were produced and tested for 7, 14 and 28 days for compressive strength, density and water absorption. The results obtained shows that the compressive strength of concrete reduced gradually for all ages with the increase in percentage replacement. Ceramic wastes from the construction sites and manufacturing industries could be recycled by breaking them into various coarse aggregate sizes and used in concrete mixes. However, a maximum content of 20% ceramic waste aggregate replacement in a mix is ideal to produce the required strength and durability of structural concrete. It was also observed that the percentage water absorption increased from 0% to 30%, it then dropped at 40% ceramic waste replacement of granite specimen. The increase in water absorption was probably due to relatively porous nature of the unpolished side of the ceramic waste as compared to the granite. It is therefore advised that coarse aggregate replacement must not exceed 20% since there was not much significant increase in water absorption up to this limit compared to the control. Meanwhile the density decreases with increase in percentage ceramic waste replacement, that is from 0% to 40%, for granite in the concrete produced. With no doubt, this mode of recycling ceramic waste could positively sustain the environment.

The high cost of concrete materials in building projects has been a concern in Nigeria. This project was carried out to investigate and compare the use of Palm kernel shell and Coconut shell in replacement of coarse aggregate in 1:1:2 concrete mix design and 0.5 water/cement ratio. It aimed at determining the maximum partial replacement of by Palm kernel shell and Coconut shell in concrete and comparing their compressive strength and other relavant mechanical properties. A total of 143 cubes of size 100mm × 100mm × 100mm were casted, the test conducted include: Sieve analysis test, Workability (Slump) test, Density test, Compressive strength test and Water absorbion test. From Sieve analysis result obtained, the values obtained shows that the PKS is poorly graded and will contain lot of voids while the CS contain smaller void. From the slump test results, true slump was obtained for both PKS and CS as coarse aggregate replacement as the slump values were within 7-42mm which is medium workability range, although the CS concrete had higher slump compared to PKS. Both Palm kernel shell and Coconut shell concrete had density greater than 2000kg/m³ for light weight concrete, the results shows that PKS concrete has lesser density compared to CS concrete, meaning it offers better sound insulation and fire resistance. The results shows that for PKS concrete the maximum compressive strength obtained and is useful was 21.93N/mm² (25% replacement) but with poor workability , moreover the useful maximum compressive strength for CS concrete was 20N/mm² (40% replacement) but with poor workability. The results also showed that the useful maximum compressive strength of PKS concrete and CS concrete with good workability was 28.63N/mm² (5% replacement) and 29.48N/mm² (5% replacement) respectively. CS as coarse aggregate had an appreciable strength compared to PKS as a coarse aggregate in concrete, considering strength/economic ratio, Coconut shell is recommended to be used as a partial replacement of coarse aggregate in making light weight concrete. The cost benefit analysis showed that 40% replacement with Coconut ahell in 1m³ of concrete there is a savings of #3,120 and at 35 replacement with In 1m³ of concrete there is a savings of #4,452.