An Experimental Research On The Basic Mechanical Property Of The Concrete With Cold Joint

During concreting,accidents may interrupt placing.when the break exceeds the initial setting time,a cold joint formation surface between the new-to-old concrete will be formed.The surface will destroy the inner structure of the concrete before being loading,which will influence the mechanical property of the concrete.The blinding surface is the most vulnerable part ofthe completed concrete.The paper,concerning the problems during concreting,explores the concrete with blinding surface based on experiments.The main content is as follows:(1)Choose two factors which may influence the bond surface performance,the age intervals and the type of the concrete.By splitting experiment,the influence degree of the two elements is acquired.The experiment shows that with the blinding surface,the splitting strength of the concrete will decrease by 15%to 45%.The conclusion accords with the formula of splitting tensile strength influenced by different elements.(2)Reveal the influence degree of the joint tensile strength against different breaks and strengths.The experiment shows the influence against break is limited.With the reinforcement of the new concrete,the compressive strength as a whole will increase by 35.14%to 39.26%.The paper puts forward the curvilinear equation between the splitting strength and the joint compressive strength.(3)Discuss the flexure property of the concrete with blinding surface in neutral axis.The experiment shows,with the cold joint,the bending strength of the concrete will increase with the lengthening of the breaks.The specimens with low modulus among the new-old concrete can be easily influenced by the age.With different ages,when the ratio of the flexural modulus is 1:18,the bending strength of the specimens increases greatly.The paper explores the mechanical property of the concrete affected by the cold joint and reveals how the joint affects the concrete under different loadings,hoping to provide useful knowledge for the safety assessment of the concrete and its reinforcement.