Effects of Particle Size Distribution of Standard Sands on the Physical-Mechanical Properties of Mortars

Abstract

Obtained natural sands can present different particle size distributions (PSD), although they have the same mineralogical origin. These differences directly influence the physical and mechanical behavior of mortars and, therefore, the performance of mortar and ceramic renderings. Standardizing the particle size of sands based on pre-established requirements in normative standards (NBR 7214 or ASTM C778) is one way to minimize these effects. However, these standards do not consider the optimization of the granular skeleton through the analysis of bulk density and PSD, which may be insufficient to obtain satisfactory results. Therefore, this paper analyzes the effects of using different particle size ranges on the physical and mechanical behavior of cement and hydrated lime mortars. The properties of consistency index, bulk density, air content, capillary water absorption, water absorption by immersion, flexural strength, compressive strength, and dynamic modulus of elasticity were evaluated. For this purpose, standardized sands of the same mineralogical origin were made with different particle size ranges, being: (i) standardized sand constituted by 25% of coarse and fine fractions (S25-control), (ii) standardized sand constituted by 30% of coarse fraction and 20% of fine fraction (S30-20), and (iii) standardized sand composed by 40% of coarse fraction, and 10% of fine fraction (S40-10), respectively. The results indicated that variations in the particle size composition of the standardized sands are necessary to obtain mixtures with higher compactness and, therefore, mortars with better physical and mechanical performance. Thus, the dosage of the particle size fractions of standardized sand should consider the optimization of the granular skeleton, being the unit mass and the granulometric composition as important parameters to meet this premise.

The effect of sand on the mechanical characteristics of gypsum-lime mortars for heritage buildings

“…Research has shown that reducing sand particle size can enhance the mechanical strength of gypsum-cemented materials [4]. In the domain of mortar properties and characteristics, a study on alkali-activated mortar employing various binder systems revealed that the mortar's workability was influenced by both the type and quantity of binder used [5]. Similarly, another study on mortar and concrete properties utilizing machine-made sand from tunnel slag emphasized the impact of sand particle size and shape on mortar IOP Publishing doi:10.1088/1755-1315/1296/1/012002 2 workability [6].…”