PERFORMANCE OF TERNARY CEMENT MORTAR USING STEEL SLAG, FLY ASH, AND METAKAOLIN

Abstract

Green mortar is a mortar that is environmentally friendly and that uses waste materials or by-products to reduce CO2 emissions that are produced during cement production. This study aims to produce a new type of green mortar by using ternary cement mixes with acceptable fresh and hardened properties. The materials used were metakaolin (10-20%), slag (15-30%), and fly ash (10-20%). The experimental work was divided into two steps. Firstly, metakaolin was replaced with various percentages of 10%, 15%, and 20%, and then the optimum percentage having the highest compressive strength was chosen to use in ternary mixes. Secondly, cement was replaced with a ternary mix (slag, fly ash, and metakaolin) with a replacement ratio of 40% and 50%. Properties were studied flowability, compressive strength, flexural strength, water absorption, dry density, ultra-sonic plus velocity test, The results show that using metakaolin as a partial replacement for cement decreased flowability and increased superplasticizer dosage. From the results can conclude the use of ternary mixes decreased the workability of mixes and increased the dosage of superplasticizers to 1.8% at 50% replacement of cement. The results of compressive strength showed an increase of 50.6% after replacing 10% metakaolin at 7 days and 17.35% after replacing ternary mixes with 15% slag, 15% fly ash, and 10% metakaolin, while flexural strength increased by 26.47% after replacing the same percent of metakaolin and by 10.4% after replacing a ternary mix with the same percent of materials. The results show that using 10% metakaolin decreased water absorption by 28.75% while increasing slag increased water absorption in ternary mixes. The results for dry density slightly decreased or increased with the increased replacement of ternary cement mixes from 1.2% to 0.33% compared with the control mix. The UPV test result increased by 5.4% in ternary cement mixes, and when replacing metakaolin with 10% and 15%, it increased UPV by 5.7% and 5.2%, respectively, at 28 days.