On Fresh and Hardened Properties of Lightweight Self-Compacting Concrete

The effects of lightweight aggregate type, content, and maximum size, as well as the water-to-binder ratio, on the fresh and hardened characteristics of lightweight self-compacting concrete (LWSCC), were investigated. Fifteen LWSCC mixtures were prepared with varying proportions of LECA and scoria (۱۰۰-۰, ۵۰-۵۰, and ۰-۱۰۰%) and divided into two groups based on water-to-binder ratios and dmax values. The slump flow, T۵۰, V-funnel flow time, and L-box were the fresh properties that were investigated, while the measurements of compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, and drying shrinkage were carried out in the hardened state. The results indicated that higher scoria content generally declined fresh state properties and improved hardened ones. An increase in dmax resulted in a reduction in the amount of superplasticizer needed to maintain the slump flow between ۷۰ and ۷۵ cm. The impact of the dmax on the mechanical characteristics of LWSCC was negligible. With increasing the dmax from ۹.۵ to ۱۹ mm, the fc merely decreased by ۷, ۴, and ۵% for S۱۰۰-L۰, S۵۰-L۵۰, and S۰-L۱۰۰ mixes, respectively. For ft, fr, and E, the decrease was between ۳.۲ and ۰.۶%. The correlation between compressive strength and splitting tensile strength was close to the CEB-FIP proposed relationship for conventional concrete, whereas the relationship between compressive strength and the modulus of elasticity was appropriately estimated using the ACI ۳۱۸-۱۹ suggested expressions. None of the proposed relations in ACI ۲۰۹.۲R-۰۸ demonstrated adequate accuracy to predict the drying shrinkage of LWSCC at all ages.

کلیدواژه ها:

Lightweight self-compacting concrete ، Scoria aggregate ، LECA aggregate ، Maximum aggregate size ، Fresh state properties ، Mechanical properties