A NEW METHOD FOR ASSESSING CALCIUM ALUMINATES CEMENTS

摘要

For monolithic castables, external conditions can significantly affect the initial properties, such as rheology and strength acquisition kinetics. As the long-term behaviour of castables is closely related to the firsts steps of installation and hydration, the knowledge of the evolution of rheology, setting and hardening is essential to forecast the performance. In this context, measurements of early-age properties of refractory castables are crucial. This paper presents an approach by which the various steps in the castable placing chain, from the period of workability to the completely hardened state, can be followed. This method relies on following the propagation of ultrasonic waves through the castable. Compared to traditional methods, this original one presents some advantages: practical and reliable, achievable with the whole castable and able to follow continuously the change in characteristics as function of time. It is sensitive to many parameters, like the castable formulation, the admixtures type or the fillers nature. It has to be pointed out that different castables show different curves: there is no generic or single profile. Relations with parameters issued from classical methods can be made but need to be studied in more details, as the relation greatly depends on the castable types. It is a promising method to detect variations with ambient temperature or ageing. Two main applications are emphasised: development of new castable formulations and quality control of products based on fixed castable formulations.