Thermal stresses are created in concrete pavements during the day and night due to the rise and fall in temperature. These stresses are very important in concrete since they lead to cracking and a reduction in the bearing capacity. The cause of these stresses is the low thermal conductivity of concrete, which stands in contrast to the materials which release the induced thermal stresses easily thanks to their high thermal conductivity. Since aggregates make up most of the volume of concrete, any change in aggregates proportion will have a significant impact on concrete properties. In this research, the effect of using copper slag and steel slag instead of natural aggregate on the thermal conductivity and mechanical properties of concrete has been evaluated. The reasons for using these two types of slag in concrete are helping with the disposal of these industrial wastes from the environment and preserving the resources of stone mines. Another reason is the suitable physical and chemical properties these two materials offer when used in concrete. Three types of natural aggregates, copper slag, and steel slag were used in 5 different mixing designs to make the test samples. In the prepared concrete samples, the ratio of aggregate volume to the total mixture, the amount of water, and the cement amount were fixed. The variable of this study was the percentage of aggregates used in concrete mixtures, which were zero, 50 and 100 % of the mixture volume. In this research, a range of tests, including slump tests, density of fresh concrete, ultrasonic pulse velocity, compressive strength, indirect tensile strength, flexural, abrasion resistance, and thermal conductivity test were performed. According to the obtained results, the concrete samples made of copper slag aggregate (100CSA) saw an increase of 20 MPa in compressive strength after 28 days of processing compared to samples with natural aggregate. Copper slag aggregate samples (100CSA) also experienced an increase of 2 MPa, 2.8 MPa and 10 mm in their indirect tensile strength, flexural, and slump resistance of concrete compared to samples with natural aggregate. In the test of abrasion resistance and thermal conductivity, samples with natural aggregate had best performance. Steel slag aggregate and copper slag aggregate reduced thermal conductivity of concrete by 23 % and 4.5 % respectively compared to the natural aggregate sample. Finally, according to the experiment results and the use of Vikor statistical method, it was revealed that concrete samples made of 50 % copper slag aggregate and 50 % natural aggregate (50NA + 50CSA) have the best performance among all other designs.
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