Title:
In Situ Mechanical Properties of Wall Elements Cast Using Self-consolidating Concrete
Author(s):
K. H. Khayat, K. Manai, and A. Trudel
Publication:
Materials Journal
Volume:
94
Issue:
6
Appears on pages(s):
492-500
Keywords:
admixtures; aggregates; bleeding (concrete); compressive strength;
concretes; modulus of elasticity; optimization; reinforced concrete;
reinforcing steels; slump; walls (structural members);
DOI:
10.14359/333
Date:
11/1/1997
Abstract:
The use of self-consolidating concrete (SCC) can facilitate the placement of concrete in congested members and in restricted areas. Given the highly flowable nature of such concrete, care is required to ensure adequate stability. This is especially important in deep structural members and wall elements where concrete can segregate and exhibit bleeding and settlement which can result in local structural defects that can reduce mechanical properties. The objective of this paper is to evaluate the uniformity of in-situ mechanical properties of SCC used to cast experimental wall elements. Eight optimized SCC mixtures with slump flow values greater than 630 mm and a control concrete with a slump of 165 mm slump were investigated. The SCC mixtures incorporated various combinations of cementitious materials and chemical admixtures. The water-cementitious materials ratios ranged from 0.37 to 0.42. Experimental walls measuring 95 cm in length, 20 cm in width, and 150 cm in height were cast. No consolidation was used for the SCC mixtures, while the medium fluidity control concrete received thorough internal vibration. Cores were obtained to evaluate the uniformity of compressive strength and modulus of elasticity along the height of each wall. Bond strengths were also determined for 12 horizontal reinforcing bars embedded at various heights of each wall. All SCC mixtures exhibited small variations 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 between compressive strength values determined on core samples and those of cast cylinders. Such reduction was approximately 10 and 20 percent for SCC mixtures made with 10- and 20-mm maximum size aggregate, respectively, and 10 to 15 percent for the control concrete. The top-bar factor for reinforcing bars positioned approximately at 140 cm from the bottom of the experimental walls was 1.4 + 0.2 for seven of SCC mixtures and approximately 2.0 for the Control concrete and one SCC. The optimized SCC mixtures are therefore highly stable despite their flowing nature and can ensure uniform in situ properties when cast in deep structural elements.*