Invention and application of unconstrained concrete device

Along with pour volume raising and difficulty increasing,it's urgent for construction stress-strain monitor.Current professional standard "Construction technical regulation of mass concrete" YBJ224-91 doesn't express monitor requirements of stress-strain.Hot strain of concrete includes constrained strain of causing stress and free expansion strain,and then the unconstrained concrete device is designed just for distinguishing them.Through the invention and application of an unconstrained concrete device,this paper puts forward the approximation test method of linear expansion factor and shrinkage and crack-control method via constrained strain.All these can establish a new method for concrete construction monitor and be supplied for test reference to similar slab construction.