Crude Glycerin, a By-product of Biodiesel, as Admixture for Concrete Pieces

Concrete is a widely consumed material in the field of construction and is composed of fine and coarse aggregates mixed with water. However, its use is responsible for the emission of CO2 into the atmosphere and high consumption of water, thus it is very important to develop more sustainable ways to produce concrete. One way to obtain sustainable concrete is to develop new concrete mixtures with admixtures that improve their performance and are not derived from petroleum. Thus, crude glycerin has potential as an admixture because of its mechanical properties, corrosion resistance, and renewability. In this context, this study aimed to evaluate the effect of crude glycerin as an admixture on the hydration of cement paste based on infrared absorption spectroscopy, scanning electron microscopy, compressive strength, and water absorption by capillarity and mortar immersion. The addition of 7% crude glycerin increased the hydration degree of the cement paste. This was verified by analyzing the changes in the infrared spectra and alkalinity of the cement paste. However, its addition to mortars in two different proportions of sand reduced the compressive strength. The absorption of water based on immersion showed that the addition of glycerin contributed to the slightly low absorption of the mortars, all of which were classified as good quality. In the case of the absorption of water by capillarity, all samples exhibited similar behaviors with similar values after 72 h.