Title: No-Fines Concrete - Its Properties
Author(s): V. M. Malhotra
Publication: Journal Proceedings
Appears on pages(s): 628-644
Keywords: air entraining agents:air entrainments;corse aggregates: freeze-thaw durability; no-fines concrete;thermal properties.
No-fines concrete consists soley of normal portland cement, water nad corse aggregate. It has been used in Europe and the United Kingdom since the 1930s for the building of single story and multistory dwellings, but had found little acceptance in North America. In recent years, however, due to increased awareness of the need for conservation of nonrenewable mineral reasources, increased consideration is being given to the use of no-fines concrete in Canada and the United States. The compressive strength of no-fines concrete is considerably lower than that of conventional portland cement concrete and varies between 200 to 2000 psi (1.37 to 13.73 MN/m^2). Young's modulus of elasticity is usally between 1.0 x 10^6 to 1.5 x 10^6 psi (0.7 x 10^4 to 1.2 x 10^4 MN/m^2) depending on the strength level of the concrete. The ratio of modulus of rupture to compressive strength expressed as a percentage varies between 10.8 and 31.0 percent. The shrinkage of no-fines concrete made with crushed limestone or river gravel, is of the order of 2 x 10^-6. This is about half that of conventional concrete. Investigations at CANMET have indicated that no-fines concrete prisms with no air-entraining agent had poor resistnace to freeze-thaw cycling; the corresponding prisms incorporating and air-entraing agent were able to withstand up to 274 freeze-thaw cycles compared with 56 for prisms without an air-entraining agent. The principal advantages claimed for no-fines concrete are economy in materials, somewhat higher thermal insulating values, lower shrinkage, and lower unit weight. The major disadvantages are its low compressive, flexural, and bond strength, and higher permiablity. The principal applications for no-fines concrete are for load-bearing cast-in-place external wallsof single story and multistory housing, small retaining walls, and as a damproofing subbase material for concrete floors cat on grade. This type of concrete is also eminately suitable for construction in Northern Canada because of its somewhat higher thermal insulating property and low cement content.