Effects of modified binders on flowability of grout and properties of preplaced aggregate concrete

In preplaced aggregate concrete (PAC), it is important yet complex to achieve a grout with high flowability and bleed resistance simultaneously. Supplementary cementitious materials, typically incorporated to impart desired properties to concrete and to complement economic and environmental benefits, may uniquely alter the properties of PAC to that of conventional concrete. Therefore, comprehensive knowledge of incorporating supplementary cementitious materials, considering alterations in their flowability and constituent materials to improve the overall performance of PAC is essential. The present study investigates the properties of PAC, incorporating ground granulated blast furnace slag (GGBS) and silica fume (SF) as partial replacement of cement at 0–40% and 0–10%, respectively. Different proportions of GGBS and SF were considered, where, flowability and superplasticizer dosage were varied with and without incorporating sand. Grout properties were evaluated in terms of flowability and compressive strength and PAC properties were evaluated in terms of mechanical strength, durability, and dimensional stability. The findings revealed that the combination of GGBS and SF in grout displayed suitable flowability and acceptable strength. Removal of sand from grout improved the properties of grout while deteriorating the properties of PAC. PAC produced using grout with 10% SF and sand to binder ratio of 0.5, exhibiting efflux time of less than 20 s, displayed the highest compressive strength. GGBS and SF significantly improved chloride ion penetration of PAC with the drawback of increased drying shrinkage. Nevertheless, all PAC mixes could still be classified as low shrinkage concrete. PAC produced with 40% GGBS and 10% SF exhibited comparable compressive strength and enhanced resistance to chloride ion penetration to that of PAC without GGBS/SF. •SF improved the compressive strength of grout with a reduction of its flowability.•GGBS enhanced the flowability of grout with a reduction of its compressive strength.•40% GGBS and 10% SF exhibited comparable strength and enhanced durability to that of the PAC without GGBS/SF.