||Use of Sand Lightweight Concrete and All Lightweight Concrete to Improve Properties
H. Celik Ozyildirim
Lightweight concrete (LWC) mixtures are made with lightweight coarse aggregate and normal weight sand — herein referred to as Sand LWC — or have both coarse and fine aggregate that are lightweight, herein referred to as All LWC. Using these lightweight aggregates as ingredients for concrete can enable a variation in the design density for structural elements varying between a practical maximum of about 105 lb/ft3 for All LWC and a maximum of 120 lb/ft3 for Sand LWC, which will be investigated in this study to determine the optimum proportions. The reduced density compared to normal weight aggregates enables a reduction in dead weight enabling longer spans, more slender columns, and fewer piers in structures, or larger precast elements for accelerated bridge construction (ABC). Either type of LWC also has reduced cracking potential because of internal curing, lower elastic modulus, and lower thermal coefficient of expansion. These benefits enable improved curing, and minimize shrinkage and thermal stresses resulting in less cracking and improved durability. This study will also investigate fibers in LWC to further control cracking. LWC can be used in patch repairs, piers, footings, decks, overlays, and other elements where reducing weight or avoiding cracking is desirable. The purpose of this study is to optimize mixture proportions for Sand LWC and All LWC to enable consistent low density, good workability, and reduced cracking potential. Tests will be conducted to determine the density, modulus of elasticity, coefficient of thermal expansion, shrinkage, and the curing efficiency.