Mechanical and durability properties of self- compacting mortars containing binary and ternary mixes of C class fly ash and ground pumice powder

In this study, the effect of ground pumice and fly ash substitution on the fresh and hardened states of self compacting mortar was investigated. A total of four series of self-compacting mortar mixes were produced, including one control mix. The first batch was the control mix. In the second batches, cement was replaced by ground pumice at 5%, 10%, 15% and 20% by weight. In the third series, the cement was replaced with fly ash at the rates of 10%, 20%, 30% by weight. In the fourth series, ground pumice and fly ash were used together, not exceeding 25% by weight of the cement. In the fourth series, 10% fly ash was used together with 5%, 10% and 15% ground pumice, and 20% fly ash was used together with 5% ground pumice. For the fresh concrete test, mini slump-flow test was performed for each mixture. For the hardened concrete test, samples with dimensions of 40x40x160 mm were cured for 7, 28 and 90 days, and then three-point bending and compressive strength tests were carried out. After 28 days of curing, the samples were exposed to temperatures of 300 °C, 600 °C and 900 °C to investigate high temperature resistance. In addition, to examine the sulfate resistance, the samples were kept in 10% magnesium sulfate solution for 90 days after a 28-day curing period. In addition, porosity, total water absorption, density and capillary water absorption tests were performed on 50 mm cube samples for each mixture. The highest flexural and compressive strengths were obtained from the mixture of 10P+10UK. After 300 °C temperature exposure, the mixture closest to the strength of the control mixture was the mixture coded 15P. After the temperatures of 600 °C and 900 °C, all samples showed significant decreases in strength, as well as significant cracks and spalling on the surface of the samples. The highest strength after exposure to magnesium sulfate was obtained from 10% UK substituted mixture. The mixture with the highest porosity and water absorption values was the mixture with the code 30UK.