EFFECT OF SULFATE ATTACK ON BINARY BINDER SYSTEM COMPOSED OF CALCINED DOLOMITE AND RICE HUSK ASH

Resistance of mortar to sulfate attack is a critical issue of its durability and long-term performance. This study aims to evaluate durability of the binary binder system composed of calcined dolomite and rice husk ash (RHA) against sodium sulfate attack. In this regard, four mortar mixes were prepared; the first mix contains 100% ordinary Portland cement (OPC) is the reference mortar, while the other three mixes containing different levels of calcined dolomite 70, 60, 50% blended with 30, 40, and 50% of RHA respectively. The prepared mixes were studied for workability, initial and final setting time, dry weight, compressive and flexural strength. To assess the durability, another set of specimens were immersed in solution of 5%Na2SO4 for 180 d, then these specimens investigated in terms of appearance, weight loss, compressive strength loss, and microstructure. The microstructure was investigated by Scanning Electronic Microscope (SEM). The results indicate that the binary binder system composed of calcined dolomite and RHA showed lower performance against sulfate attack compared to OPC in terms of strength, expansion, cracking, and spalling.