LABORATORY PERFORMANCE ASSESSMENT OF RENDERING MADE WITH DIFFERENT SHARP SAND AND SILTY SOIL BLENDS

Abstract

This study was undertaken to evaluate the engineering properties and behaviour of different type of soils used for rendering. Two soil types namely: sharp sand (SS) and silty soil (PS) were used for the study. The soil types were blended to produce six different mix combinations which include: 100%SS/0%PS, 80%SS/20%PS, 60%SS/40%PS, 20%SS/80%PS and 0%SS/100%PS by weight. The engineering properties of the two different soil types and a blend of the two different soil types were investigated. The two different soil types were mixed with Portland cement to produce plaster using a mix design of 1:3. (cement: aggregate). The structural properties of the plaster were also investigated. Findings obtained from sieve analysis test classified sharp sand and silty soil as A-2-4 and A-2-6 according to AASHTO Soil Classification System, SC (sand mixed with clay) and SM (sand mixed with clay) according to Unified Soil Classification System. The specific gravity of sharp sand and rendering  soil were 2.65 and 2.55 respectively, liquid limit, plastic limit, shrinkage limit and plasticity index ranged from 24.74% - 34.8%, 16.1% - 28.51%, 6.02% - 8.64% and 2.22% - 8.64% respectively. The maximum dry unit weight and optimum moisture content ranged from 14.91kN/m³ – 18.80kN/m³ and 14.86% - 21.77%. Findings obtained from slump test revealed that the slump of the fresh plaster increased with increase in amount of sharp sand with the slump value ranging between 15mm – 40mm, the hardened density and compressive strength of the plaster increased with increase in the amount of sharp sand. The study therefore discourage the use of only silty soils for rendering as such rendered surfaces would be susceptible to occurrence of shrinkage cracks and spalling.

Keywords; Mortar, rendering, sustainability, compressive strength,