SETTING TIME AND COMPRESSIVE STRENGTH OF PC BASED BINARY BINDER: EFFECT OF LIMESTONE CONTENT AND FINENESS
Use of Portland cement (PC) indirectly contributes to global CO2 emission level. Embedded CO2 in PC mainly comes from the production process of clinker (main active material in PC) that approximately releases CO2 in the same amount of clinker produced. Substitution of PC with more environmentally friendly material provides the opportunity to decreases CO2 emitted from the use of PC. One of abundantly available substituting material is limestone. It is well understood that the use of limestone as substituting material in binary binder alters the properties of substituted PC binder. The degree of alteration on the properties of PC substituted by limestone is mainly as the influence of particle size distribution of limestone. Equipment to find out particle size distribution (PSD) is expensive and analysis of the test result is relatively complex. In current study, laboratory test is performed to investigate the influence of limestone fineness on setting time and compressive strength of binary binder. Fineness of limestone is measured by two common simple methods, Blaine’s test and the portion of particles resides on sieve number 325. Binary binder is prepared by blending PC meeting type 1 of ASTM C150 & limestone powder ground to different fineness. Mix preparation is following ASTM C 109 and mix with PC is used as reference. Mix preparation of each binary binder (with different fineness of substituted limestone) uses two systems of water content. First, water to binder ratio (w/b) is kept constant. Second, consistency of fresh mortar is kept constant by varying water content. Constant w/b used is 0.485 as the value in ASTM C 109 required for PC. Consistency of mortar is measured following ASTM C 1437.