Avaliação da autocicatrização em concretos contendo cimentos ternários do tipo LC³: desenvolvimento e impacto na durabilidade

Abstract

The objective of this study was to evaluate the self-healing phenomenon and its impact on the durability of concretes containing ternary cements of the LC³ type. For this purpose, concrete mixes with three different water/cement ratios were developed, using, in addition to the LC³ cement, the CPV ARI cement, in order to provide a comparison between both. The cracking of the samples was made by the diametrical compression test, with an opening limiter device, at the age of 7 days, and the curing procedure adopted was submerged in water for a period of 42 days. Self-healing was evaluated through the analysis of crack images by microscopy, the ultrasonic wave propagation velocity test and the low-pressure water penetration test. All concrete mixes also had molded specimens intended for the compressive strength test. For the durability analysis, in addition to the study of water penetration, the amount of material present in the crack was identified, before and after the test, in order to understand its permanence capacity. The material formed on the surface of the cracks was collected and characterized in terms of its mineralogy through the X-ray diffraction (XRD) test. Ternary cement of the LC³ type has self-healing capacity, although at a lower level when compared to CPV ARI cement, under the conditions of this study. The maximum healing achieved by mixtures with LC³ was 64.5% and for CPV ARI cement it was 76.9%. Much of the material formed in the healed cracks remained after the action of water, for both cements analyzed, indicating its probable contribution to durability. The presence of C-S-H, Ca(OH)2 and CaCO3 was identified in the healing products for CPV ARI cement, and the same crystalline phases for LC³, however with the presence also of C-A-S-H and AFm. Regarding compressive strength, a superior performance of LC³ cement was observed. Such behaviors found in the study are probably linked to the fact that ternary cement of the LC³ type culminates in the formation of more stable hydration products and a denser cementitious matrix, which hinders the migration and percolation of this material to the cracks analyzed, and benefits the development of compressive strength.