A New Generation of Structural Lightweight Concrete

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Title: A New Generation of Structural Lightweight Concrete

Author(s): 0. A. Kayyali and M. N. Haque

Publication: Special Publication

Volume: 171

Issue:

Appears on pages(s): 569-588

Keywords: Blast furnace slag; compressive strength; drying shrinkage; flexural strength; fly ash; glass fibers; high-strength concrete; lightweight aggregate concretes; modules of elasticity; polystyrene.

Date: 8/1/1997

Abstract:
Two types of lightweight concrete were investigated. The first was made with polystyrene beads and blast furnace slag aggregate. This concrete yielded a dry density value of about 1650 kg/m3 with a compressive strength of 30 MPa, moduli of rupture and elasticity values of 5.3 MPa and 20 GPa respectively. Drying shrinkage of this concrete was higher than that of normal weight concrete. The second type of concrete investigated was made from sintered fly ash aggregate as a total replacement of both coarse and fine aggregate. This concrete yielded a dry density of about 1790 kg/m3 and a compressive strength above 70 MPa, and values for the moduli of rupture and elasticity of 5.5 MPa and 21 GPa respectively. The stress-strain relationship of this concrete is a straight line till very near to failure thus underlining its brittle nature. the shrinkage values for this concrete are lower than normal weight concrete and this is attributed mainly to the excellent bond capability and to the high absorptive capacity of the aggregate. Expressions for predicting the moduli of rupture and elasticity provided by some codes of practice did not give accurate results specially when applied to the polystyrene beads type concrete. Addition of fly ash as a partial replacement of fines was beneficial in eliminating segregation and increasing workability and cohesion of the fresh concrete.