Investigation of cement replacement with high content of pumice on mechanical property of concrete: a case of c-25 grade of concrete

Abstract

Pumice is a textural term for a volcanic rock that is solidified frothy lava typically created when superheated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. In view of environmental and sustainability concerns associated with the production of cement, the use of pozzolanas to replace part of Portland cement is receiving a lot of attention. The partial replacement of ordinary Portland cement by pozzolanas are known to improve the mechanical strength, resistance to sulphates and reduces pore sizes of concrete. The objective of this research is to investigate cement replacement with high content of pumice on mechanical property of concrete. For this study pumice natural pozzolona sample is collected and their chemical and physical properties were studied and the experiments were performed on C-25 grade of concrete mix with 0.51 water cement ratio with slump of 25-100mm. Concrete Cubes were casted from each batch of the mix by varying percentage of pumice as replacement of cement 0%, 30%, 40%, and 50% whereas all other parameters keeping as constant. A total of 24 cubs and 24 beams samples were prepared for testing at age of 7th and 28 days for four percentage of pumice. The result of this research was show that, at 0%, 30, 40%, and 50% replacement of cement with pumice have a compressive strength of 21.41Mpa, 18.44Mpa, 12.69Mpa, and 9.76Mpa respectively at the age of 7 day of curing and 33.8Mpa, 31.73Mpa, 29.35Mpa and 26.4Mpa respectively at the age of 28 day of curing. On the other hand, 0%, 30, 40%, and 50% replacement of cement with pumice have a flexural strength 3.84Mpa, 3.59Mpa, 3.28Mpa and 2.95Mpa respectively at the age of 7 day of curing and 3.97Mpa, 3.68Mpa, 3.61Mpa and 2.94Mpa at the age of 28 day of curing. In addition to this, the concrete mix having a slump value 65mm, 65mm, 60mm, and 60mm for 0%, 30%, 40%, and 50% replacement of cement with pumice respectively. The compressive and flexural strength of concrete shows reduction due to increment of percentage of pumice but all percentage of the replacement of cement with pumice satisfy the specified compressive strength of concrete (fc). Hence it is recommended to replace until 50% replacement of cement with pumice.