Effect of Ground Granulated Blast Furnace Slag (GGBFS) on Mechanical Properties of Roller-Compacted Concrete Pavement

Abstract

Abstract Because of various convenient features, such as high manufacturing speed, cost effectiveness, and high strength at low ages, roller-compacted concrete (RCC) has found growing use in the construction of concrete pavements. This study investigated the effect of ground granulated blast furnace slag on the mechanical properties (compressive and tensile strength and modulus of rupture) of RCC at the ages of 28 and 90 days. For this purpose, 40 preliminary RCC mix designs based on slag contents of 0, 20, 40, and 60 % (by weight of cementitious materials), moisture contents of 4, 4.75, 5.5, 6.25 and 7 % (by total weight of cementitious materials and aggregates), and cementitious material contents of 12 and 15 % (by weight of aggregate) were devised and tested to determine the optimum moisture content for eight primary mix designs. The primary mix designs were used to make 144 specimens for the evaluation of targeted mechanical properties. The results showed that the moisture content that was needed to reach maximum compaction increased with increasing slag content. The highest strengths were observed in the specimens that contained 40 % slag, which all exhibited equal or greater strength than the corresponding slag-free specimens. The scanning electron microscope images showed that this difference can be attributed to the better filling of pores and cracks with small-sized slag particles, which outperform cement particles in this respect. It seems that there is an optimum level for replacing cement with slag in order to achieve improved strength and that exceeding this level will lead to strength reduction. In this study, this optimum level was found to be 40 % slag. Moreover, increasing the cementitious material content from 12 to 15 % was found to increase the compressive strength, tensile strength, and modulus of rupture by reducing the water-to-cement ratio.