THE RESEARCH OF CORE RING METHOD TO MEASURE RESIDUAL STRESS ON THE SURFACE OF CEMENT CONCRETE SLAB
In the procedure of concrete strength development,the changes in cementitious material volume results in the production of internal residual stress.Because the volume changes of cement pasted on the surface are influnced more obviously by environmental factors,the residual stress on the surface of rigid pavement slab will develop quickly and may lead to the appearance of micro crackings.According to the hole drilling strain gage(HDSG) method which is often used to measure residual stress in metal structure,some researchers developed the core ring strain gage(CRSG) method for concrete structures and the feasibility of this method was studied.In this paper a finite element model(FEM) is developed to simulate the process of core ring drilling in concrete slab.The parameters in CRSG method are selected based on FEM's results for different cases.Large scale slabs are casted in laboratory and tests using CRSG method to measure residual stress are conducted.The test results of two cases(loading on slab corner and no loading) indicate that CRSG method can release the residual stress and can be used to measure residual stress on the surface of rigid pavement slab.