tailieunhanh - Ebook Materials for civil and construction engineers (4/E): Part 2

Part 2 book “Materials for civil and construction engineers” has contents: Portland cement concrete, masonry, asphalt binders and asphalt mixtures, wood, composites, microscopic composites, macroscopic composites, properties of composites, composites sustainability, and other contents. | C h a p t e r 7 Portland Cement Concrete Civil and construction engineers are directly responsible for the quality control of portland cement concrete and the proportions of the components used in it. The quality of the concrete is governed by the chemical composition of the portland cement, hydration and development of the microstructure, admixtures, and aggregate characteristics. The quality is strongly affected by placement, consolidation, and curing, as well. How a concrete structure performs throughout its service life is largely determined by the methods of mixing, transporting, placing, and curing the concrete in the field. In fact, the ingredients of a “good” concrete may be the same as those of a “bad” concrete. The difference, however, depends on the expertise of the engineer and technicians who are handling the concrete during construction. Because of the advances made in concrete technology in the past few decades, concrete can be used in many more applications. Civil and construction engineers should be aware of the alternatives to conventional concrete, such as lightweight concrete, high-strength concrete, polymer concrete, fiber-reinforced concrete, and roller-compacted concrete. Before using these alternatives to conventional concrete, the engineer needs to study them, and their costs, in detail. This chapter covers basic principles of conventional portland cement concrete, its proportioning, mixing and handling, curing, and testing. Alternatives to conventional concrete that increase the applications and improve the performance of concrete are also introduced. Figure shows order of activities involved in the construction process of concrete structures. Proportioning of Concrete Mixes The properties of concrete depend on the mix proportions and the placing and curing methods. Designers generally specify or assume a certain strength or modulus of elasticity of the concrete when determining structural dimensions. The