Effect of different sand grading on strength properties of cement grout

Abstract

This paper aims to study the consistency and strength properties of cement grouts prepared with three different sand grading namely 100% passing through 1.18 mm sieve (P1.18 mm), 0.90 mm sieve (P0.90 mm) and 0.60 mm sieve (P0.60 mm), respectively. The measured flowing time indicated that the specimens with the finer sand grading had lower flowability than those of the coarser sand grading. As the results, the finer sand grading specimens required a higher water to cement ratio to achieve an equivalent workability. The specimens with the coarser sand grading obtained higher 7 and 28 days compressive strengths than those of the finer sand grading when the lower water to cement ratio was adopted (0.61–0.63). However, when the higher water to cement ratio (0.65–0.67) was used, the specimens with the finer sand grading achieved higher long-term compressive, flexural and splitting tensile strengths than those of the coarser sand grading.

Introduction

The application of grout materials and grouting technique are common for construction sector nowadays. Records abound, cement-based grout or self-compacting repair mortar have been widely used since the 1800s and even earlier [1], [2]. Grouting is a process of fluids injection that set into fissures, cracks or voids [3], [4]. Nowadays, several types of grout materials have been used, including cement, cement and sand, clay–cement, slag cement, gypsum–cement, epoxy–polymer, clays–asphalt, pulverized fuel ash and a large number of colloid and low viscosity chemicals [5]. Cement grout with a high flowability is widely used in the concrete remedial works due to its flowable and self-compacting behaviors. It can easily flow into fine cracks and fissures attributed to its fluidity. High fluidity of cement grout is a vital requirement of high cohesion or segregation resistance during flow to form a uniform and homogeneous mix. As the fluid cement grout can be fully compacted without vibration, the application of the self-compacting cement grout/mortar can therefore reduce labor and machinery costs, improve compaction and hence enhance durability of the critical cover zone of a structural member [6]. Relatively few detailed studies have been reported on the influence of different grading of sand filler on the properties of cement mixes especially self-compacting cement mortar. De Schutter and Poppe [7] noticed that sand type has a significant effect on the cement mortar properties. The authors observed that geometrical parameters of sand based on the grading curve, like fineness modulus, relative specific surface and apparent weight, can be correlated with the water demand of the sand in the mortar, and may also influence the hardened properties of mortars. Westerholm et al. [8] found that the viscosity of mortar was influenced by the fines content of fine aggregates, which may increase with the increased total surface area of the fine aggregates. According to Haach et al. [9], the cementitious-based mortars (cementitious to sand ratio = 1:3; cementitious = solely Portland cement or Portland cement + lime) prepared with the finer sand filler (passing through 1.18 mm sieve) required a higher w/c than that of the coarser sand filler (passing through 4.75 mm sieve) to achieve an equivalent consistency. Reddy and Gupta [10] observed that the cementitious-based mortar prepared with the finer sand filler required 25–30% more water to achieve the desired consistency than that of the coarser sand filler. The compressive strength does not seem to be affected by the sand grading. However, the sand grading could influence the dimensional stability and modulus of elasticity in compression of the cementitious-based mortars [9], [10]. From the foregoing, there are still limited studies on the effect of sand grading on the characteristics especially long-term strengths of self-compacting cement mortar (CG). Therefore, it is of necessity to further study the effect of sand grading on the strength properties of CG for a concrete remedial work. This paper studies the effectiveness of using three different sand fillers namely P1.18 mm, P0.90 mm and P0.60 mm on workability and strength properties of CG.