Investigation of the effects due to formation of cold joint in concrete

Abstract

Performance of concrete structures can be directly affected by the presence of a joint. These joints can be either intentional or unintentional. The intentional joints may be formed to make the construction sequence more convenient. Construction joints and movement joints are good examples for intentional joints in concrete structures. However, there can be joints which are formed unintentionally and can affect the performance of the structure. Cold joints are such unintentional joints which occur due to excessive delay of placing consecutive layers of concrete. This can happen when the initial setting time of the first layer has passed when placing the second concrete layer. Concrete specimens with cold joint were prepared by varying the casting time of the second concrete layer. An experimental investigation was carried out to study the effects of such cold joints on performance of concrete. Test methods were developed to find out the influence of a cold joint in concrete on mechanical properties such as shear strength and tensile strength of concrete. From the results, it was found that there is a significant reduction in shear strength and tensile strength due to presence of a cold joint.