A mix-design method for lightweight aggregate self-compacting concrete based on packing and mortar film thickness theories

This paper puts forward a simple mix design method for lightweight aggregate self-compacting concrete (LWASCC) based on the packing and mortar film thickness (MFT) theories. The mix design method is composed of two simple stages: optimization of granular skeleton and optimization of cementitious materials composition. The former is conducted according to ASTM C 29 by packing different amounts of coarse and fine aggregates. The latter is carried out by using the minimum water requirement method. To verify its applicability for LWASCC, five mixture proportions with varying MFT (i.e., 1.4, 1.6, 1.8, 2.0 and 2.2 mm) were designed. The results showed that the proposed mix method is an effective method to develop LWASCC. The flow-ability increases with the increase of MFT. The compressive strength at 28 d and 56 d shows a contrary variation tendency compared with its early ages, which is attributed to the stiffness difference between aggregates and mortar at different age. The splitting tensile strength of MT-1.4 is higher than that of MT-1.6. With the increase of MFT ranging from 1.6 mm to 2.2 mm, the splitting tensile strength increases due to the decrease in the quantity of aggregate content and the positive effect of MFT on the aggregate/paste interface.