An investigation on the alkali activation potential of colemanite concentrator wastes

The alkali activation potential of colemanite concentrator waste (CW) was investigated in the scope of this thesis. Experimental studies were performed at three stages. In the first stage, alkali activation of CW calcined at different temperatures for two hours has been investigated under steam curing condition. In the second stage, the effects of activator type, dosage and curing conditions (moisture and steam curing) on the some engineering properties of alkali activated mortars, such as compressive and flexural strength, water absorption characteristics and drying shrinkage behaviours were investigated. Furthermore, XRD, ATR-FTIR, TGA/DTA and SEM/EDS analyses were carried out on the hardened paste mixtures. In the third stage, the compressive strength and drying shrinkage of alkali activated mortars produced with the replacement of ground granulated blast furnace slag with CW at different ratios were determined under steam and moisture curing conditions. Test results showed that a calcination temperature of at least 700 degress is necessary to initiate the alkali activation of WCB, while the maximum compressive strength value was obtained at 800 degress. The minimum activator concentration for alkali activation of calcined CW was found as 6 percent Na2O by weight of CW with a minimum silicate modulus (Ms=SiO2/Na2O) of 1.2 for both curing methods. Compressive strength values up to 37.6 MPa and 39.5 MPa along with acceptable water absorption characteristics and drying shrinkage values can be obtained from alkali activation of calcined CW at 800 degress under steam and moisture curing conditions, respectively. The drying shrinkage values of steam-cured alkali activated mortar mixtures were lower compared to Portland cement mortar mixture. On the other hand, in case of moisture curing alkali activated mortar mixtures showed higher drying shrinkage than Portland cement mortar. Replacing the ground granulated blast furnace slag with CW in amount higher than 20 percent for steam curing and 10 percent for moisture curing caused significant decrease in compressive strength. On the other hand, the drying shrinkage of alkali activated slag cement mortar mixtures decreased with the increase of CW content. The drying shrinkage values of steam and moisture cured 40 percent CW incorporated mortar mixtures decreased about 50 percent at 56-day compared to alkali activated slag mortar.