Determination Research Of Early Shrinkage Of Mortar

There's great significance to study how to measure the shrinkage of cement-based materials, for the deformation of cement-based materials has important implications in its cracking. The purpose of this paper is to bring a new method for the determination of cement-based materials shrinkage deformation in the early age with the carrier of specimen.The method used is testing the strain of the specimen using gauges attached to the surface to characterize the deformation of the specimen itself. There're two problems to be solved before test of strain. The first question is up to the condition of using strain gauges, the strain gauges must be attached to the flat surface of the specimen with relatively large stiffness, therefore, a thin layer of fast hard water mud layer (base material) is coated on the surface of the specimen and then the strain gauges was attached to the fast hard water mud layer. Then the second question arises, the measured strain is the strain of the fast hard water mud layer, how will the strain be translated to the strain of the specimen itself. In this paper, the ratio of the strain of the base material and the strain of the specimen was calculated using the method of finite element under explicit material parameters. The results show that the ratio is only related to the elastic modulus and Poisson's ratio of the mortar specimens if the elastic modulus and Poisson's ratio of the base material is determined. Meanwhile, the elastic modulus and Poisson's ratio need to be tested before the translation of the base material strain to the mortar specimen strain, for the elastic modulus and Poisson's ratio is changed with the age of mortar specimen. In this article, the physical is not to be measured, which is the subject of another professional.The dynamic-static and static s were all used to data collection and recording. Dynamic-static tester was used to record the mortar specimens of 12h age, it lasted about 12h, and the physical quantity measured is the voltage. The results show that the dynamic-static tester can record the continuing declined voltage, which reflected that the mortar specimens are shrinking.Static tester was used to test the mortar specimens of 6h age, it lasted about 21h, the test results show that in this time period, the mortar specimens is expanding at first, then shrinkage deformation is occurring. This is almost coinciding with the time of exothermic of mortar hydration.From the finite element analysis and the two experiments, it is assert that the method is feasible to test the deformation of mortar by testing the strain of fast hard water mud layer sticking to the surface of the mortar.