Effects of milling followed by different gradation sizes of lawrencepur sand on the properties of cementitious mortar

Abstract

The swift rise of urbanization and industrialization has severely depleted natural sand resources and escalated industrial waste accumulation. Environmental damage from over-dredging and limited disposal space has driven researchers to seek alternative solutions. In Lahore, Punjab, Pakistan, coarse pit sand is predominantly used, and overly fine sands from the Ravi and Chenab rivers, which do not meet ASTM grading standards. In this research, Lawrencepur Sand was milled, and its effects on the sand's physical properties and the mortar's mechanical performance were evaluated. For this, comprehensive experimental investigations were conducted, and the mechanical properties of the mortar were assessed at 3, 7, and 28 days. From the experiment, it is clear that milling refines the physical properties of sand by decreasing size, fineness modulus (FM), and absorption, while increasing density and specific gravity, which enhances mortar performance. Milled sand improved mortar density (3.1–11.5 %), compressive strength (10.6–71.4 %), and flexural strength (13.5–48 %), while reducing water absorption by 9–34 %. Excessive milling reduced strength and increased water absorption. SPSS analysis confirmed that milled sand significantly improved mortar performance, with strong statistical validation (p < 0.001). Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analysis also confirmed microstructural densification of mortar by milling, and over-milling led to a decline in performance due to poor packing.