Evaluation of mechanical properties and durability of geopolymer mortar based on the granulated blast furnace slag replaced with patial replacement of kaolin in different molarity

Geopolymers are aluminosilicate materials that can be a suitable alternative to all types of concrete, because they help preserve the environment by removing pollutants such as CO2. The present study examines the mechanical characteristics and durability of slag-based geopolymer mortars (GGBFS) and its replacement with different percentages of kaolin in several molar amounts. Sodium hydroxide with a concentration of 4 and 8 M and sodium silicate have been used as activators. The mentioned basic materials have been examined alone and in combination with other components of the mixture. For this purpose, kaolin powder has been mixed with slag in the percentages of 50% and 75%, which, including non-combined mixtures, has made a total of 12 mixing designs. The studied properties included: compressive, bending and tensile strengths, percentage of water absorption and electrical resistance at the age of 28 days. The compressive strength of geopolymer samples at the ages of 7, 28 and 90 days was determined and the following results were obtained: The use of polymer in the 7 and 28 day compressive strength test in the BS8 design sample compared to the S4 control design improved the strength of the samples by 15% and 24%, respectively. In the tensile test of the SC50-4 mixing design sample (2.79 Mpa) compared to the control S4 design sample (2.63 Mpa), the strength of the sample improved by 6%. In the flexural strength test, no significant difference was observed between the S4 design sample and the BS8 design sample. In the final water absorption test, the samples of mixing designs containing kaolin powder next to slag had almost the same water absorption.