Development and Experimental Use of a 90 MPa (13,000 psi) Field Concrete
Pierre Laplante, and Claude Bedard
Appears on pages(s):
columns (supports); field tests; flexuralstrength;
high-strength concretes; modulus of elasticity; plasticizers;
porosity; retardants; shrinkage; silica; temperature; thermal -- gradient.
Test results of a field experiment are presented where a 90 MPa (13 000 psi) silica fume concrete was used in the construction of an experimental column of a 26-storey highrise building. This concrete used a set-retarding agent in addition to a superplasticizer, had a water/cementitious ratio of 0.25 and was delivered at a slump of 250 mm (10 inches) after 45 minutes of travel. Maximum temperature was reached about 30 hours after mixing and was about 45°C (113°F) higher than the initial temperature of the fresh concrete. The thermal gradient inside the column was never greater than 20"C/m (21"F/ft) and no thermal stress problems were noted. Expressions of the modulus of rupture and modulus of elasticity, as a function of the compressive strength, are proposed. The 91 days shrinkage of this very high strength silica fume concrete was similar to that of plain concrete having a W/C of 0.40. In one concrete batch, due to a superplasticizer overdosage that resulted in an 18-hour set retardation, entrapped air macropores of 1.0 um size were created and caused a 10 MPa (1 450 psi) strength reduction at 91 days.