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| Experimental study on mechanical properties of concrete with cold joints |
| QIN Yuan1, LIANG Da1*, WANG Yulong1, CHAI Junrui1, ZHOU Heng2 |
| 1. School of Water Conservancy and Hydropower, Xi′an University of Technology, Xi′an, Shaanxi 710048, China; 2. Power China Northwest Engineering Corporation Limited, Xi′an, Shaanxi 710065, China |
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Abstract Cold joints in concrete directly affect the overall performance of concrete structures. In this paper, compressive tests and splitting tensile tests were conducted on the concrete with cold joints formed by the cold joints at different ages and the concrete with cold joints formed by the superimposed concrete with different elastic modulus, the variation law of its mechanical properties was studied. The results show that the overall compressive strength of concrete specimens with cold joints and the bonding strength of the cold joints bonding surface are gradually decrease with the growth of age. The strength of new concrete is increased, which can effectively improve the compressive strength of concrete with cold joints. However, the improvement of the bonding surface strength is relatively limited. By calculating the rock brittleness characteristic coefficient, it is found that the strength improvement of new concrete can effectively improve the deformation resistance of old and new concrete. A formula for calculating the strength of cold joint bonding surface is established, which can predict the bonding strength of cold joint bonding surface well. When the age interval is about 7 to 14 day, and when the ratio of elastic modulus of new and old concrete is 1.10, the mechanical properties are better. When the age interval is more than 28 days, the ratio of elastic modulus of new and old concrete should not be more than 1.10.
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Received: 11 November 2021
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