Use of Sand Lightweight Concrete and All Lightweight Concrete

About the report:

Lightweight concrete (LWC) has reduced density, enabling a reduced dead load compared to normal weight concrete, thus allowing longer spans, slender columns, fewer piers in new construction, and the use of existing substructures in rehabilitation projects.  LWC in which both the coarse and fine aggregates are lightweight, called “All LWC,” has an even greater reduction in density than “Sand LWC,” where only the coarse aggregate is lightweight.  LWC also has a low cracking potential at all ages mainly because of internal curing, a low modulus of elasticity, and a low coefficient of thermal expansion.  Lightweight aggregates must be prewetted in order for these benefits to be achieved.

This study investigated All LWC and Sand LWC in the laboratory for use in bridge structures.  LWCs with varying total cementitious material contents, supplementary cementitious material, and water–cementitious material ratios had satisfactory strengths for use in bridge structures.  Differences in compressive strength between air-cured and moist-cured specimens were smaller than with normal weight concretes, which was attributed to internal curing that provided moisture for the hydration reactions.  The reduced elastic modulus obtained enables lower stresses for a given deformation, helping to reduce bridge deck cracking.  LWC with fibers had high tensile strength and ductility, which can control cracking, including that related to loads.

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