Long term study on compressive and bond strength of coconut shell aggregate concrete

Effects of three types of curing on coconut shell aggregate concrete have been studied for long term performance. The pore structure of coconut shell has been studied through scanning electron microscope (SEM). The pore structures in coconut shell behave like a reservoir. Intermittent curing produced the highest coconut shell aggregate concrete strength, followed by full water, and then by air-dry curing. Biological decay was not evident as the concrete cubes gained strength even after 365 days. Up to an age of 90 days, the samples under all types of curing conditions showed improved response on the pulse velocity and subsequently an insignificant drop. The ultimate bond strength of coconut shell aggregate concrete under all types of curing conditions was much higher compared to the theoretical bond strength as per BS 8110 and IS 456. Bonding between the cement paste and the coconut shell aggregate has been studied by measuring fissure between the coconut shell and the cement paste through SEM analysis. It shows a tendency of narrowing the fissure due to its age, which shows that the bond appears to be better between the coconut shell and the cement paste.