Non-Destructive Evaluation of Internal Sulphate Attack in Cement-Based Materials Applying Non-Linear Ultrasonic Techniques

Abstract

One of the most aggressive attacks to which cement-based materials can be exposed is that produced by sulphate. During this attack, expansive products are formed, causing volumetric strains in hardened materials, which brings microcracking and the reduction of their strength and durability. The use of non-destructive techniques for characterizing the microstructure of cement-based materials, and for following the development of deleterious processes which can affect them, has become an important research field. Among them, non-linear ultrasonic (NLU) techniques have shown to be useful for evaluating the material degradation. The aim of this work is to study the possibility of using the NLU technique for the non-destructive evaluation of initial development of internal sulphate attack in cement-based materials. Cement pastes were prepared using ordinary Portland cement, to which an appropriate amount of calcium sulphate 2-hydrate was added during the setting for producing an internal attack in the samples. Furthermore, its effects in the microstructure have been followed with mercury intrusion porosimetry. The expansion and linear ultrasonic pulse velocity were also determined. The preliminary results indicate that the NLU technique could be useful for studying the development of sulphate attacks in the short-term, complementing the information provided by other techniques.