The effects of calcium stearate on mechanical and durability aspects of self-consolidating concretes incorporating silica fume/natural zeolite

Abstract

Moisture and aggressive ions transfer into concrete can be considered a significant threat to the durability of self-consolidating concretes (SCCs). To restrict moisture and aggressive ions transfer into concrete, utilizing damp-proofing agents is expected to be beneficial. These admixtures can decrease permeability of concrete, especially the permeability under non-hydrostatic condition, by providing a water-repellent layer along the capillary pores. This study investigated the impacts of calcium stearate (CS), as a damp-proofing agent, on durability properties of SCCs which were prepared with various types of supplementary cementitious materials (SCMs). In addition to durability properties, the effects of CS on mechanical characteristics and properties of fresh concrete, and microstructure have been studied as well. The outcomes demonstrated that in fresh concrete, CS (up to 7 kg/m3) prompted a decrease in workability and density of fresh concrete without any significant impact on slump loss. The results of hardened concrete evaluation also showed a reduction in either density of hardened concrete or compressive strength. Plus, microstructure analysis showed that incorporation of CS deteriorates both the cement paste and the interfacial transient zone. Eventually, although CS had a negligible impact on electrical resistivity, total water absorption, and chloride diffusivity, it was absolutely effective on permeability of concrete under non-hydro static pressure. In this regard, inclusion of CS drastically reduced the depth of capillary penetration of water in addition to short and long term water absorption. As a case in point, incorporation of 7 kg/m3 of CS decreased the last-mentioned parameters by respectively 60%, 72%, and 40% compared to the reference mixture after 120 days of moist curing.