İnvestigation of phsical and mechanical properties of alkali aktivated mortars produced with silica fume additive fly ash under the effect of different sulphates

In this study, the physical and mechanical properties of C class fly ash geopolymer mortars produced with constant potassium hydroxide (KOH) and sodium hydroxide (NaOH) and silica fume additives at 3 different rates were investigated. The mortar samples mixed in the cement mixer were placed in standard molds measuring 40×40×160 mm. Then it was kept in an oven at 100 ºC for 24 hours. After the samples removed from the oven were removed from the mold, they were kept at room temperature for 28 days, and then their physical and mechanical properties were examined. The samples were placed in sodium sulfate (Na2SO4) and magnesium sulfate (MgSO4) solution. Height and weight changes, flexural and compressive strengths of the samples were measured during 30 days, 90 days and 180 days. As a result of the experiments, it was observed that the samples produced by activating with NaOH did not lose excessive strength, while the compressive strength of the samples produced by activating with KOH and under the influence of sulfate increased on the 30th day. It was determined that the compressive strength of the samples under the influence of Na2SO4 reached 75.14 MPa on the 30th day, and the samples under the influence of MgSO4 reached 64.31 MPa. In general, it has been determined that the produced samples are durable under the effect of sulfate. It is thought that fly ash based alkali activated mortars produced with silica fume additive can be used in the production of prefabricated building materials.