IN-SITU MECHANICAL-PROPERTIES OF WALL ELEMENTS CAST USING SELF-CONSOLIDATING CONCRETE

The use of self-consolidating concrete (SCC) can facilitate the placem ent of concrete in congested members and in restricted areas. Given th e highly flowable nature of such concrete, care is required to ensure adequate stability. This is especially important in deep structural me mbers and wall elements where concrete can segregate and exhibit bleed ing and settlement which can result in local structural defects that c an reduce mechanical properties. The objective of this paper is to eva luate the uniformity of in situ mechanical properties of SCC used to c ast experimental wall elements. Eight optimized SCC mixtures with slum p flow values greater than 630 mm and a control concrete with a slump of 165 mm were investigated. The SCC mixtures incorporated various com binations of cementitious materials and chemical admixtures. The water -cementitious materials ratios ranged between 0.37 and 0.42. Experimen tal walls measuring 95 cm in length, 20 cm in width, and 250 cm in hei ght were cast. No consolidation was used for the SCC mixtures, while t he medium fluidity control concrete received thorough internal vibrati on. Cores were obtained to evaluate the uniformity of compressive stre ngth and modulus of elasticity along the height of each wall. Bond str engths were also determined for 12 horizontal reinforcing bars embedde d at various heights of each wall. All SCC mixtures exhibited small va riations in compressive strength and modulus of elasticity in relation to height and were similar to those obtained with the medium fluidity control concrete. Considerable reductions were, however obtained betw een compressive strength values determined on core samples and those o f cast cylinders. Such reduction was approximately 10 and 20 percent f or SCC mixtures made with 10- and 20mm maximum size aggregate, respect ively and 10 to 15 percent for the control concrete. The top-bar facto r for reinforcing bars positioned approximately at 140 cm from the bot tom of the experimental walls was 1.4 +/- 0.2 for seven of SCC mixture s and approximately 2.0 for the control concrete and one SCC. The opti mized SCC mixtures are therefore highly stable despite their flowing n ature and can ensure uniform in situ properties when cast in deep stru ctural elements.