Effects of cold joint and its direction on the compressive and flexural strength of concrete

Abstract

A cold joint is the main problem in concrete construction, especially in large quantities such as mass concrete. The capacity of mixing plan and manpower make monolith casting is impossible. The distance between the batching plant and the construction location is also an obstacle to cold joints. This study would test the compressive and flexural strength due to the effect of cold joint in concrete. The period of the casting between two concrete (cold joint) was 120 minutes and 240 minutes. Tests carried out in the form of compressive strength and flexural strength of the vertical and horizontal directions of cold joints. The types of concrete used in this study include normal concrete with 35 MPa compressive strength, concrete with high initial compressive strength using superplasticizer, and concrete using polypropylene fiber as added material. Compressive and flexural strength tests were carried out at 3, 7, 14 and 28 days. All specimens used water curing up to the predetermined test life. The test results show that specimen with the cold joint connection in normal concrete has a decrease in quality (flexural and compressive), so does with the concrete with superplasticizer (high early compressive strength), whereas in concrete using fiber has increased in strength compared to normal concrete without cold joint connection.