DEVELOPMENT OF HYDROPHOBIC ALKALI-ACTIVATED MORTAR MADE FROM FLY ASH AND CALCIUM CARBIDE RESIDUE MIXTURE AS A BINDER

This article aims to develop hydrophobic alkali-activated mortar using fly ash with high and low calcium oxide and calcium carbide residue mixture as a binder. This study was divided into 4 parts i.e. 1) find the optimum ratio of binder by varying contents of ground low-calcium fly ash, high-calcium fly ash, and ground calcium carbide residue at the ratios of 70:0:30, 70:15:15, and 70:30:0 by weight. 2) find the optimum contents of alkali activator (sodium metasilicate pentahydrate) by varying at the ranges of 10 - 30% by weight of binder. 3) find the optimum contents of calcium stearate, the water-repellent material affecting the water absorption and contact angle of the mortar surface, by varying at the range of 5 - 10% by weight of binder. 4) study the effects of using hydraulic cement at a ratio of 10% by weight of binder. Binder to sand ratio of all mortars was kept at 1:2.75 by weight. The flowability of mortar was controlled between 110 ± 5%. The properties of mortar such as compressive strength, water absorption, the contact angle, and microstructure were investigated. The results showed that the highest compressive strength of mortar was obtained from the mixture of high-calcium fly ash at 15% blended with 15% of ground calcium carbide residue and 70% of ground low-calcium fly ash binder. Additionally, an increase in sodium metasilicate contents further enhanced the compressive strength of mortar. increased the compressive strength of mortar. The water absorption of mortar was decreased while the contact angle was increased with the increase of sodium metasilicate and calcium stearate content and the use of hydraulic cement in binder.