Expansive Cement Concretes-Present
State of Knowledge
ACI Committee 223
Appears on pages(s):
buildings; calcium aluminates; calcium sulfoaluminate hydrates; calcium
sulfoaluminates; concrete pavements; concretes; curing; drying shrinkage; ettringite.
This state-of-the-art report outlines the historic background of the development of expansive cement concretes abroad and in this country, presents the relevant nomenclature, and summarizes the current status of expansive cements in the United States. The hydration chemistry of expansive cements is described, with em hasis o n the components necessary for the formation of ettringite. The important in factors the choice of proportioning of materials are discussed, as well as the products of reaction, and heat of hydration. Various factors are discussed, which influence the rate and amount of expansion of all three types of expansive cement concretes. These include the chemical composition, fineness and age of cement, water-cement ratio, mixing time, admixtures, aggregates, curing, temperature, restraint, and size and shape of specimens. Th e properties of expansive cement concretes are reported separately for shrinkage-compensating and self-stressing concretes. The properties considered include workability, bleeding, time of setting, unit weight and yield, expansion, creep, shrinkage, compressive and bond strengths, modulus of elasticity, Poisson’s ratio, coefficient of thermal expansion, and the resistance to various actions (deicer scaling, sulfate attack, cracking, and abrasion). Properties are also indicated on which no data are available at present. Field performance of shrinkage-compensating concrete is summarized. The in-fluences of restraint, aggregates, additives, ambient temperatures, forms, consistency, finishing, and curing are discussed. Examples of structural installations are presented, which include flat slabs, one-way pan joists, and two-way waffle slabs for parking garages, a folded plate roof for a bank, topping on a prestressed single tee parking deck structure, grade slabs and tilt-up panel walls for a department store, and an industrial floor. Five highway installations are described, including various spacings of contraction joints, continuously reinforced pavement as well as an unreinforced one, an application of self-stressing concrete, and the use of two bridge decks. The results of 17 tests on laboratory made structural elements of self-stressing concrete are summarized. These include tests on pipes, slabs, beams, frames, columns, and hyperbolic paraboloid. A brief review is given of some overseas experience. Needed areas of research and development are discussed with respect to expansive cements, material properties and behavior, and applications. An extensive bibliography is presented.