Effect of Mixing Ratios Using Local Pozzolana as a Partial Cement Replacement on Plastic Cracking in Cement Mortar

Abstract

Premature cracking during the plasticization stage is an undesirable phenomenon in concrete, causing subsequent problems in the durability and structural performance of structures. The term "plastic shrinkage cracking" is used to describe cracks that form in concrete between the moment of pouring and the moment of setting. The objective of this research is to investigate the effect of different mixing ratios and the use of pozzolana as a partial cement replacement, in addition to the effect of water-to-cement ratios on the formation of plastic shrinkage cracks, particularly in hot and dry environments with high evaporation rates. Experiments were conducted on cement mortar mixes with water-to-cement ratios of 0.45, 0.60, and 0.80, and with pozzolana replacement ratios of 0%, 10%, 20%, and 30%. The results showed that increasing the water-to-cement ratio significantly increased plastic shrinkage cracking, especially in reference plots, while adding pozzolana at a rate of 10% helped reduce cracking and improve the cohesion of the mixture. As the pozzolana ratio increased to 20% and 30%, a slight increase in cracking was observed, indicating that higher than the ideal ratio may lead to adverse results. The study recommends using 15% pozzolana as a partial cement replacement to achieve the best balance between reducing cracking and improving concrete performance in harsh environmental conditions.