Internal and External Effects of Sodium Sulfate on the Strength of Soil Cement

In coastal industrial zones with saturated loose soil, sulfate attack is an additional problem. The problem becomes more acute when using soil cement, because an undesirable sulfate content can enter the body of the element with the material used to create it. This research includes two parts. In the first part, the effects of internal and external sulfate attack are compared in simulation of four groups of elements: control, prefabricated, cast-in-place and soil–cement. In the second part, the effects of the sulfate-resistant cement content (100–400 kg/m3) and sulfate concentration (0–5%) on behavior of cement-stabilized sand specimens were examined. In both parts, the unconfined compressive strength of the cylindrical specimens was measured over the course of 362 days. The results of part one showed that internal attack had a significant effect on decreasing the strength of the soil–cement specimens (up to 70%) compared to prefabricated (about 40%) and cast-in-place (about 20%) specimens. The results of the second part showed a logarithmic trend in the variation of strength versus the cement factor and sulfate concentration over time.