Experimental research for elastic modulus of cement paste at ultra-early age based on indentation technique

Abstract

Based on the principle of indentation method, a testing method for ultra-early elastic modulus (EMod) of cement paste using micro-force testing machine is proposed in this study. The test results show that if the loading time is less than 2 min, the influence of cement paste viscosity can be neglected, and the ultra-early EMod of cement paste can be measured by this indentation method. Experiments prove that the EMod measured by the indentation method of conical indenter with semiangle of 45° are close to that obtained by the traditional stress-strain testing method. In order to verify the test method, different cement pastes in variety of water-binder (w/b) ratio and fly ash content are prepared, and the error between the indentation method and the traditional stress-strain method is less than 15%. The dynamic EMod is tested through using ultrasonic method, and the overall trend is consistent with the results of the indentation method. The experimental results show the relationship between the ultra-early EMod and time is linear function. Defining the EMod of initial setting time as the zero point, the EMod of the earliest measurable time through traditional stress-strain method as the end point, the ultra-early EMod of cement paste would be predicted by two-point connection. Compared with the indentation method, the error is less than 20%.