EFFECT OF CEMENT, LIMESTONE AND HYDRATED LIME ON SETTING TIME AND COMPRESSIVE STRENGTH OF LOCAL GYPSUM

Abstract

This paper consists of studying the effect of adding different ratios of cement, limestone powder and hydrated lime on setting time and compressive strength of gypsum which available in local market which does not conform to Iraqi Standard Specification (I.Q.S) No.28/1988. The adding materials are low-cost and available in local market and can be used to improve setting time and compressive strength for gypsum which are considered as the most important properties if it used as mortar or in finishing. The adding ratios of cement were (10, 20, 30, 40 and 50) % from gypsum weight, the ratio of (50%) was the best ratio as regarded to setting time and compressive strength. They are (10.33 minutes) and (8.04 N/mm² ) respectively. For the limestone powder addition, the ratios were (10, 20, 30, 40, 50 and 60) % from gypsum weight. The results showed that, the ratio of (10%) was the best in compressive strength (6.2 N/mm² ) and ratio of (60%) was the best in setting time. At adding hydrated lime, the ratio of addition (2.5%) gave compressive strength (7.51 N/mm²) and the ratio of (12.5%) gave setting time (14.15 min).