Investigation of Durability of Self-Compacting Concretes Made of Different Aggregates under the Influence of Sulfate Environment using twist-off test

In many parts of Iran, especially in the southern regions of the country where concrete is exposed to seawater, sulfates are the main destructive factors of concrete. The main factors related to the durability of concrete are the type of materials, concrete structure, density, and curing. Inadequate compaction of concrete due to the lack of acceptable vibration in the limited parts between the formwork and rebars is one of the main factors of low structural reliability exposed to sulfates. Due to the lack of information related to the effect of aggregate strength on the performance of self-compacting concrete, in this paper, the effects of type and strength of aggregates on the durability of self-compacting concrete against sodium sulfate is presented. Granite, marble, andesite, rhyolite, travertine, lime, green tuff, crystalline green tuff, and basalt were used to make concrete. "Twist-off" and "Drilled core" tests were employed to measure the compressive strength of rocks. "Twist-off" test is an accurate method with a wide range of applications in determining the strength of materials both in the laboratory and on site and is considered as a fast, accurate and low-cost technique with minor failure in the field of semi-destructive testing. The attractiveness of this method is in accuracy, speed, simplicity, minor breakdown, and low cost of doing it, which makes it more comparable than other on-site tests. This test can be performed in horizontal, vertical, and generally on any smooth surface without the need for prior planning. The tools used in this test are very simple and accessible and performing the test does not require previous skills. The experiments were performed at ages 7, 14, and 28. The results show a direct relationship between the strength of the parent rock and the strength of self-compacting concrete made with of rock. At an early age, there is an increase in compressive strength of samples placed in sodium sulfate compared to samples treated in water. Also, a high correlation coefficient was obtained between the results of the "twist-off" test and the "Drilled core" test, which could be used to measure the compressive strength of rocks with the "twist-off" test with high confidence.