A.I Agbonaye

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.