External sulfate attack on compressed stabilized earth blocks

Abstract

Cementitious materials can be damaged by external sulfate attack due to ingress of sulfate ions from external environment. This process causes loss of cohesion, increase in porosity, local expansion, spalling and cracking. The objectives of this work were to study the influence of the capillary absorption time and of the sulfate ions concentration on compressed stabilized earth blocks (CSEB) exposed to sulfate attack. The CSEB were submitted to cycles of capillary absorption of sodium sulfate solution and drying. Two sets of procedures were used to evaluate the wear of the samples. In the first set of procedures, the capillary absorption time was varied. In the second one, the sodium sulfate concentration was varied instead. The CSEB used had the same dosage of earth, cement and water and for each procedure 3 samples were tested. The masses were measured after taking the samples out of the solution and after a 2-week drying time, being that a cyclic process for each procedure. The room temperature and relative humidity allowed crystallization of thenardite and mirabilite. Granulometry, XRD, XRF and SEM tests were used to identify the materials. The results showed that capillary absorption time and sulfate concentration influences the wear of the CSEB.