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Today, in order to reduce the harmful effects of the environment and increase the mechanical properties and durability of concrete, particles with high pozzolanic properties are used as a suitable alternative to ordinary cement in concrete. And filler, as an alternative to cement, has attracted the attention of researchers. In this laboratory study to investigate the effects of slag and nanosilica slag consumption on the microstructure of geopolymer concrete and compare it with the characteristics of control concrete containing Portland cement, 1 mixing design of control concrete and 3 mixing designs of geopolymer concrete containing 92, 96 and 100% composite kiln slag was fabricated with 0, 4 and 8% nanosilica, respectively. X-ray fluorescence (XRF) was performed. In order to investigate the effect of microstructural changes on the macro structure of concrete, compressive strength and tensile strength tests were performed on concrete samples at 90 days of age. Examination of the images obtained from the SEM test shows the superiority of the microstructure of the geopolymer cement matrix in all designs, compared to the microstructure of the control concrete containing Portland cement. Celsius), the effects of improvement and cohesion in the microstructure of geopolymer concrete are evident due to the presence of silica nanoparticles, in this regard, the presence of 8% nanosilica in mixture 4 (geopolymer concrete), accelerates the reactivity process and increases the volume of hydrated gels Geopolymerization was compared to other geopolymer concrete mixtures (containing 0 and 4% nanosilica). Images of concrete samples heated to 500 ° C show signs of weakening of the concrete microstructure compared to images taken of concrete at room temperature. The results of XRF test indicate the presence of the highest amount of oxidilica and aluminum oxide (the main factors in improving the density in the microstructure of concrete), in the combination of designs 4 and 2 by 36 and 8%, respectively. The high peaks created in the XRD spectrum diagram often occur in areas with angles (θ2) of 28 °, and their height varies according to the presence of aluminosilicate particles in the concrete mix. The application of high heat to the concrete specimens caused a decrease in the results of the XRD test. Evaluations performed on the results of the test to determine the compressive strength and tensile strength in concrete, showed coordination and overlap with the results of microstructural tests in this study.

Keywords: Geopolymer Concrete, Blast furnace slag, Nanosilica, Concrete Microstructure, Scanning electron microscope

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