Study on Early Compressive Strength of Mortar- and Crumb Rubber-Engineered Cementitious Composites Contain Variation of Cement, Palm Shell Ash and River Sand

Engineered cementitious composite (ECC) is a composite that has better tensile properties and behavior compared to concrete. ECC is usually made from cement, water, silica sand, cementitious material, fiber, and other materials. ECC mortar does not use fiber. Cementitious material in this research uses palm shell ash, with a proportion of 5-15% of the cement weight. Crumb rubber was used as a substitute for fiber, with a proportion of 2.5-12.5% of cement weight. Workability is measured based on the slumpflow test. Aim of research is to investigate compressive strength of ECC mortar and CR-ECC with variations in the addition of palm shell ash, cement, river sand and crumb rubber. Based on the test results, the average compressive strength obtained for ECC mortar ranged from 19.70 to 42.67 MPa, and for CR-ECC specimens, the average compressive strength achieved ranging from 17.70 to 37.28 MPa. Test results show that ECC mortar and CR-ECC specimens provide good compressive strength, that is more than 17 MPa (according to provisions of SNI-2847). However, compressive strength of CR-ECC is lower than that of ECC mortar. This is because crumb rubber is compressible material, so it is not strong enough to withstand the compression loads.