Investigating the effects of loading rate and mixing design on concrete's direct tensile strength using the CTLC test

Tensile strength of concrete is measured using direct tensile tests on rectangular concrete samples with dimensions: ۱۹ cm in length, ۱۶ cm in width, ۶ cm in thickness, and a central hole of ۹ cm in diameter. The concrete specimens were prepared in the laboratory by mixing cement, fine sand, gravel, and water in appropriate proportions. Calibration of the new direct tensile strength test apparatus was carried out to determine the tensile strength of different brittle materials (gypsum and concrete) under various loading rates and different mixing design types. The direct tensile strength tests were accomplished by a compressive-to-tensile load converter (CTLC) fitted with the specimens and placed in the universal testing machine in the laboratory. For the indirect Brazilian tensile strength tests, loading rates of ۵, ۱۰, and ۱۵ kg/s were considered. For the direct tensile strength tests, loading rates of ۲, ۲.۵, and ۳ mm/min were used. The results of this paper show that the direct tensile strengths measured by the CTLC apparatus are approximately ۲۵% lower than those measured by the Brazilian tests. The average tensile strengths of the geo-material samples increase as both the loading rate and the ratio of fine sand to gravel increase.

کلیدواژه ها:

Concrete ، Direct tensile test ، Brazilian tensile test ، Mixing design ، Loading rate