Evaluation of different mineral additives and fly ash in aerated concrete production

Conventional gas concrete is a lightweight concrete that is lightened by adding a pore-forming additive to the mixture of finely ground silica sand (quartz sand) and binder material (lime, cement) and which becomes stable by pressurized steam curing. The use of different natural and artificial mineral materials in aerated concrete mixes will provide product variety and economy in production. In this study, the usability of rhyolite, perlite and fly ash as a mineral additive in gas concrete production and its effect on aerated concrete properties were investigated. Based on the G2/05 gas concrete class, four different reference gas concrete mixture ratios were determined under two groups. Aluminum, slaked lime, gypsum and water/solid ratio were kept constant in each group mixtures. In the first group study, each mineral additive was used by replacing 25%, 45%, 65% and 85% cement in 3 different reference gas concrete mixes. In the second group study, productions that only 76% of each mineral additive was used as the reference mixture were made. In this group, 3 different ratios of cement (20%, 40%, 60%) and silica sand (30%, 50%, 70%) were added to the reference mixture by replacing with mineral additive. The amounts of aerated concrete components were determined according to the total amount of solid material. The produced gas concrete samples were allowed to swell at 40° C for 4 hours and then cured in autoclave at 180°C and 12 bar pressure for 6 hours. Spread, penetration, pressure, dry unit volume weight, capillary water absorption and thermal conductivity tests were performed on the gas concrete samples. SEM and XRD analyzes were also performed. According to the experiment results, compressive strength values of 2.16-2.57 MPa, 2.24-2.41 MPa and 2.04-2.53 MPa were obtained in perlite, rhyolite and fly ash reinforced gas concrete samples, respectively. Aerated concrete samples which producing without cement could not be obtained only in mixtures with mineral additives. Keywords: Autoclaved, Aerated Concrete; Perlite; Ryolite; Fly Ash; Compressive Strength