Ultrasonic Characterization of Cement and Concrete

Ultrasonic velocity measurements are used to control the quality of fresh Concrete and to monitor the concrete mixtures during hardening or curing process. The goal of this research is to determine the time required for a given mixture of Concrete to be hard enough for form removal in a construction site. Currently the concrete form removal time is not accurately known. The early removals of the concrete forms results in weaker concrete and the late removal of the concrete forms prolong the construction time. The shear and rigidity moduli of freshly mixed concrete increases with time and this change can be monitored by measuring the ultrasonic velocity in the concrete as a function of time. In this paper we investigate the evolution of ultrasonic pulse wave velocity as a function of time in the concrete mixtures, with different water to cement ratio. The results obtained can be used to predict the setting time of concrete and also to control the quality of the concrete in the construction industry. The curing process is a series of chemical reactions by which the concrete mixture, when not stirred, gradually increases its viscosity and hardens industry, knowledge of the setting-time of the concrete for form removal or for the addition of a new edifice is crucial for speeding up the construction. Although there are published guidelines such as tables from the American Concrete Institute, currently this time interval cannot be accurately predicted. It depends on the uncontrollable parameters such as ambient temperature and humidity, among other factors