Title: Performance of Self-Consolidating Concrete for Casting Basement and Foundation Walls

Author(s): Kamal H. Khayat, John Bickley, and Michel Lessard

Publication: Materials Journal

Volume: 97

Issue: 3

Appears on pages(s): 374-380

Keywords: walls; consolidation; high-performance concretes; segrega-tion; self-consolidating concrete; stability; viscosity; workability

DOI: 10.14359/4630

Date: 5/1/2000

Abstract:
The construction of foundation and basement walls in residential and small building construction often involves the use of low-quality con-crete. Such concrete can exhibit excess cracking and low impermeabil-ity, hence affecting the quality of habitation. This paper reports the results of a field-oriented study carried out to demonstrate the suit-ability of high-performance, self-consolidating concrete for the con-struction of basement and foundation walls. Two optimized mixtures were first used to cast 4 m 3 L-shaped experimental walls measuring 15 x 1.2 x 0.2 m. The easy-flowing yet cohesive concrete was shown to spread through the narrow unrein-forced formwork and fill it in. The mean spacing factor and rapid chloride ion permeability were determined along the walls and were shown to vary between 120 and 175 µm and 575 and 900 coulomb at 56 days, respectively. The mean compressive strength of such con-crete ranged between 8 and 16 MPa after 1 day, and 50 to 60 MPa after 56 days The in-place compressive strength after 56 days varied between 30 and 40 MPa for the self-consolidating concrete made with 20% fly ash and 3% silica fume replacements (w/cm of 0.45), and 42 and 50 MPa for the richer mixture with 40% slag and 3% silica fume replacements (w/cm of 0.42). The strength decreased slightly near the top of the walls and away from the casting position. The silica fume slag concrete was used in the casting of the perimeter foundation walls of a three-townhouse complex at the Canadian Centre for Housing Technology in Ottawa. A total of 36 m 3 of self-consolidating concrete was used to fill the basement walls measuring 12 x 18 m in plan, approximately 2.5 m in height, and 0.2 m in thickness. The concrete was cast from opposite corners and was shown to spread readily into place and self-level, resulting in a high-quality surface finish.