Effect of lightweight aggregate on key properties of SCC designated for repair applications

Abstract

An experimental program was undertaken to determine the effect of the type and substitution rate of light-weight coarse aggregate (LWCA) (0, 25, 35, and 50%, by total coarse aggregate volume) and different shrinkage-reducing strategies on key engineering properties of fiber-reinforced self-consolidating concrete (SCC) designated for repair applications. The shrinkage-reducing approaches included the replacement of normal-weight sand by light-weight sand (0 and 20%, by the total volume of sand), the incorporation of shrinkage-reducing admixture (SRA) and expansive agent. The SCC was proportioned with synthetic fibers to reduce the risk of cracking caused by shrinkage and increase the service life of the repair. Test results indicate that the investigated light-weight concrete can exhibit adequate frost durability regardless of the level of the investigated substitution rate of light-weight aggregate. The incorporation of 20% light-weight sand and 25% LWCA led to significant reduction in autogenous and drying shrinkage with limited drop in mechanical properties and durability. The contribution of internal curing to reducing autogenous and drying shrinkage seemed to offset the increased porosity and reduced stiffness caused by the use of porous aggregate. The combined use of 20% light-weight sand and 25% LWCA exhibited the best overall performance compared to other SCC mixtures. The incorporation of SRA or EA did not have significant influence on the air-void system, frost durability coefficient, and Coulomb values. Reduction in autogenous shrinkage using moderate and high contents of SRA was relatively limited compared to the use of EA (10 to 125 μm/m vs. 170 to 710 μm/m). Moderate dosage of SRA developed 20% lower drying shrinkage at 6 months compared to similar concrete prepared without any SRA.

Keywords:

• autogenous shrinkage
• creep
• durability
• light-weight aggregate
• repair
• restrained shrinkage
• self-consolidating concrete

Acknowledgment

The authors wish to thank Béton Provincial, Euclid Canada, Northeast Solite Corp., the Jacques Cartier and Champlain Bridge Inc., the Ministry of Transport of Québec, and the City of Montreal for their support.