EFFECT OF REACTIVE MAGNESIUM OXIDE ON THE PHYSICO-MECHANICAL PROPERTIES AND DURABILITY OF CEMENT MORTAR

Abstract

The present work aims at studying the effect of magnesium oxide (MgO) on the physico-mechanical properties of cement mortar (CM).In order to produce MgO with different reactivity, namely MgO550 and MgO1250,hydromagnesite was calcined at 550 and 1250°C.Different MgO550 and MgO1250 proportions (0, 2.5, 5, 10 and 15wt.%)were used as addition or replacement of CM. The results showed that, the low MgO1250 content up to 5 wt., % (as addition or replacement) has a positive impact on the physico-mechanical properties of CM. The 2.5 and 5 wt., % MgO550 (as addition) have little effect on the compressive strength enhancement. The addition of MgO550 and MgO1250 beyond 5 wt. %leads to a significant compressive strength reduction. The MgO550 (as replacement) has a negative impact on the mechanical properties CM. The linear expansion of CM containing MgO550 was higher than that having MgO1250 (as addition or replacement). The CM replaced by MgO550and MgO1250 show lowest linear expansion. The result also showed that, the CM having 5 wt., % MgO550 and MgO1250exhibit the highest resistivity to sulfate attack up to 6M comparing with control sample. The acceleration has a good impact on the mechanical properties of CM, especially in CM having MgO550 and MgO1250. The curing media plays an important role on the behavior of CM in presence and absence MgOS. The CM with or without MgO1250 exposed to CO2 gas has higher firing resistivity than that of cured in Tapwater. The XRD and TG/DTG data proved that, the hydration rate of MgO1250is lower than that of MgO550. The SEM confirmed the nucleating impact of MgO1250.