The use of limestone as a partial rep lacement of Ordinary Portland Cement (OPC) hasrnseveral advantages like Technical, Economical and Env ironmenta l.rnThe present study aimed at investigating the phys ico-mechanical properties of freshrnand hardened cement pastes of Portland limestone cement (PLC) made by blend ingrnclinker, gypsum and fined ca lc ite. Where the percentages of limestone are 0%, 5%,rn10%, 15%, 20% and 25% by mass and the particle s izes are 6 11m, 12 11m, 18 11m andrn24 11m used to replace a part of Ordinary Portland cement. The resuiting specimensrnwere compared for, standard cons istency, sett ing time, so undness, and compress ivernstrength. Generally, the results show that as the Ca lcite fineness increase, therncompress ive strengths of PLC also increases for some amount whereas, when thernamount of fined calcite increases in PLC the compressive Strength of the mortarsrndecreases. However, the specimens have competitive strength for the rep lacementrnvalue of Calc ite powder up to 20% by mass of clinker with particle s ize 6 11m, Thesernrepresents a significant reduction o f energy, raw material consumption, costs andrnenvironmental advantages by reducing CO, emiss ion over ord inary Portland cements.rnSetting time, both init ial and final setting times, result were decreased with anrnincrease Calcite in PLC. Furthermore, at the same level replacement, the cementrnpastes of 611m and 1211m of limesto ne show lower setting time than those us ing,rnI 811m and 24!lm, respective ly.