Tamir ANAR

Establishment of a Simple and Reliable Direct Tensile Testing Method for Concrete

Takumi Shimomura

To evaluate concrete's tensile strength, two testing methods exist: the splitting tensile test and the direct tensile test. The splitting tensile test assesses tensile stress in the cylinder's diameter direction, which may deviate from actual concrete tensile stress. Conversely, the direct tensile test measures properties closer to tensile strength and stress-strain relationships without the splitting tensile test's weaknesses. Thus, the direct tensile test is deemed the most suitable method for determining tensile strength. However, the limited number of past experimental examples stems from several problems. One problem involves bending moments due to eccentricity caused by testing apparatus conditions and specimen shape, affecting tensile force purity. Another problem is the potential for fracture within the testing zone.
This study aimed to develop a direct tensile test method for resin concrete, as developed by Minami, and investigate its applicability to cement concrete. Various parameters, such as water-cement ratio, specimen age, and underwater curing period, were varied. Direct tensile tests, compressive tests, and splitting tensile tests were conducted over a wide strength range. Direct tensile tests used the clamping ring developed by Minami, while splitting tensile tests utilized fracture sections from direct tensile tests.
Comparisons between splitting tensile strength and direct tensile strength, as well as between compressive modulus of elasticity and direct tensile modulus of elasticity, were conducted to evaluate the direct tensile test's applicability for resin concrete to cement concrete. Results showed higher splitting tensile strength than direct tensile strength. However, previous studies suggest concrete's direct tensile strength is slightly higher than splitting tensile strength. The calculated splitting tensile strength, based on compressive strength characteristic values, was higher than conventional splitting tensile strength. This discrepancy could be due to the small size of specimens used in splitting tensile tests, possibly resulting in inaccurate data collection. Nonetheless, no issues were identified with the direct tensile test procedure. Consistency in the tensile modulus of elasticity within a certain range indicates accurate assessment of deformation properties related to tensile behavior.