Technical Report: Mechanical Properties of Mortars with Sands from Central Mexico

Abstract

The effect of fine aggregates in mortar mixtures was studied using different Portland Type II 30R RS cements, in order to achieve optimal compressive strengths according to regulations. To determine their compressive strength, 75 cubic specimens were made, using 15 mix designs based on five brands of cement and three types of sand. The results show that there is variable resistance when using different types of sand and cement. The granulometric analysis determined that only one of the three types of sand has an appropriate particle size and the evaluation of cement pastes from five Type II brands revealed differing mechanical properties. Those brands of cement that do not meet the specified strength are discussed, as well as how the sand-cement relationship must take into consideration the origin of the fine aggregate and its relationship with the brand used. Reductions of the quantity of cement needed can be achieved by understanding the performance of the sand in the mix. The sand does influence the resistance of the mortars and each aggregate presents a differentiated performance for each brand of cement. The article concludes that these banks of materials have different compositions, influencing the characteristics and properties of the sands, and the different brands of Portland Type II 30R RS cement resulted in differing resistances to compression, even when their specifications would categorize them as being of the same type.