The Effect of Curing Method on Properties of Roller Compacted Concrete Pavements (RCCP) with and without Silica Fume

Due to their high rate of construction and economical advantages, roller compacted concrete pavements (RCCP), are finding increased use in many countries. RCCP has successfully been used for pavement construction in ports, cargo terminals, low speed roads, parking lots and heavy and military vehicle roads. Research and development is continuing to improve skid resistance of this type of pavements which should lead to its wide spread use in high speed roads.Due to their large surface area, concrete pavements are sensitive to the curing method and duration which is applied for them applied. Roller compacted concrete pavements (RCCP) are expected to be particularly sensitive in this regard due to their low mix water content. It is thus important to characterize the effect of various curing regimes on strength and durability of RCCP concretes, so that appropriate minimum curing requirements can be set in project specifications.In this research, effects of three different curing regimes, namely; water curing, application of curing compounds and air curing, on strength and permeability of RCCP mixes were investigated. The experimental work was conducted on two different RCCP mixes with 275 and 350 of cementitious materials. The results of experimental program showed the substantial effect of curing regime on strength and durability of RCCP mixes. Considering water curing as the reference, curing in laboratory environment with a relative humidity of 40%, resulted a 45% reduction in compressive strength. Similar reduction was observed for bending strength. Curing by chemical compounds was not very effective in improving the situation and 35% reduction in both compressive and tensile strength was observed, compared to wet curing regime. The effect of curing on durability characteristics, such as water absorption and coefficient of water permeability followed a similar trend to that observed for strength, but was even more severe.Silica fume is considered as an effective industrial additive that is widely used when concrete with high strength or durability is required. The effect of incorporation of silica fume at a replacement level of 10 percent of cementitious materials on properties of RCCP mixes and the sensitivity of such mixes to various curing regimes was also investigated.The results showed that incorporation of silica fume at the aforementioned dosage resulted an increased water demand of about 10 % percent in order to keep the same level of workability as the control mix. Due to the increased water demand and water to cementitious materials ratio, the incorporation of silica fume resulted in only a modest increase of strength characteristics of 5 to 14 percent. Improvement in water absorption and permeability characteristics of RCCP due to incorporation of silica fume was also modest for the same reason.