Critical cold joint angle in concrete

Abstract

This study aims to understand the effect of different cold joint angles on splitting tensile and compressive strength of concrete. A series of tests were conducted in the context of this study. Four different concrete grades (10, 20, 25, 30 MPa) were selected to demonstrate the very low grade, low grade, minimum grade and normal grades of concretes according to Turkish Earthquake Codes 2007 and 2018. In addition to the concrete grades, cold joint angle is also a parameter to be investigated. Zero angle was the control angle. Besides, 20, 45, 65 and 90 degrees were studied to understand the effect of cold joint angle on tensile and compressive strength of the concrete. It was found that compressive strength was not adversely affected from the cold joint angles of 0°, 20°, 45° and 90°. The difference is almost 10 %. However, 65° of cold joint angle seems to affect the compressive strength significantly since the reduction in compressive strength varied between 32.5 % and 48.4 %. Specimens having 65° cold joint angle was observed to fail by sliding over the cold joint plane. Splitting tensile tests showed that 90° cold joint angle was the most unfavorable situation. Introducing vertical cracks parallel to the loading direction before the test resulted in the lowest tensile strengths. Splitting tensile strength equation considering the cold joint angles was proposed.