Optimization and Performance of Air-Entrained, Self-Consolidating Concrete

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Title: Optimization and Performance of Air-Entrained, Self-Consolidating Concrete

Author(s): K. H. Khayat

Publication: Materials Journal

Volume: 97

Issue: 5

Appears on pages(s): 526-535

Keywords: air entrainment; deformation; high-performance concrete; self-consolidating concrete

Date: 9/1/2000

Abstract:
The use of self-consolidating concrete (SCC) can enable the reduction of labor demand for vibration and surface finishing, accelerate placement rate of concrete, and secure superior surface quality. Despite the low yield value required for deformability, SCC is characterized by a moderate viscosity to enhance cohesiveness and stability of the fresh concrete. The air entrainment of SCC for frost durability can reduce viscosity leading to greater risk of segregation and blockage of concrete flow upon spreading between closely spaced obstacles. This paper investigates the mixture proportioning of air-entrained SCC suitable for filling congested sections, such as in the case of repair of the underside of bridge deck girders, and conventional non-restricted elements. The results of a laboratory study undertaken to optimize and evaluate properties of air-entrained SCC are presented in this paper. The mixtures were proportioned with 370, 450, and 550 kg/m 3 of cementitious materials and water-cementitious material ratios (w/cm) of 0.45 to 0.50. Ternary binders containing 20% Class C fly ash or 40% ground blast-furnace slag with 3% silica fume were used. The mixtures were evaluated for slump flow consistency, restricted deformability and surface settlement, strength development, elastic modulus, temperature rise, shrinkage, perme-ability, and frost durability. Examples of the use of such concrete for repair of a densely reinforced beam in a parking structure and a moderately reinforced beam-wall element with restricted access in a powerhouse are also discussed. Test results clearly indicate the feasibility of proportioning air-entrained SCC of high stability and resistance to blockage. Optimized mixtures exhibited adequate engineering properties and durability. The field studies demonstrated the effectiveness of such high-performance concrete to repair damaged sections presenting difficulties for placement and consolidation.