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Author

Hamid Behdad

Document Type

Thesis - University Access Only

Award Date

1989

Degree Name

Master of Science (MS)

Department

Civil Engineering

First Advisor

M. Nadim Hassoun

Abstract

Lightweight concrete is a concrete which by one means or another has been made lighter than conventional concrete. This means, that the most obvious characteristic of lightweight concrete is its density which is always less than that of normal weight concrete. Basically, there is one means of reducing the density of concrete, and that is by including air in the concrete composition. This, however, can be achieved in four distinct ways: 1. By omitting the finer sizes from the aggregate grading, thereby creating the so-called “no-fines” concrete. 2. By replacing the gravel or crushed· rock aggregate by a hollow cellular or porous aggregate which includes air in the mix. This type of concrete is known as “lightweight aggregate concrete”. 3. By creating gas bubbles in a cement slurry which when it sets leaves a sponge-like cellular structure, termed “aerated concrete”. 4. By forming the air cells in the slurry by chemical reaction or by vigorous mixing of the slurry with a proper foam concentrate in a high-speed mixer. This type of concrete is called “cellular concrete”. The term “no-fines” concrete generally means a concrete composed of cement and a course, 3/4 in - 3/8 in (19mm - 9mm) aggregate only, the product so formed having many uniformly distributed voids throughout its mass. No-fines concrete is used for load-bearing cast in situ external and internal walls, party walls, non-load bearing walls, infilling walls for framed structures, under-floor filling for solid ground floors, and for roof screeds. In lightweight aggregate concrete, reduction in unit weight is made possible by use of lightweight aggregates which mainly consist of fine and coarse. The range of lightweight aggregates manufactured for lightweight or insulating concrete, reinforced or not, is very wide, and their names vary according to their origins and countries. in which they are produced. There are three main types of 1ightweight aggregates: 1. Natural aggregate: natural lightweight aggregates come from eruptive rocks. The principal aggregates are pumice, pozzolans, tuffs, and volcanic slags. 2. Artificial aggregate from industrial by-products: furnace clinker, foamed slag, and sintered pulverized-fuel ash are among these types of aggregates. Furnace clinker comes from the combustion of coal in domestic or industrial firing systems. Slag is a by-product of the manufacture of pig iron in blast furnaces. Fly ash or pu1verized fuel ash is the residue of the combustion of pulverized coal used as fuel in thermal power stations. 3. Industrially produced artificial aggregate, such as expanded clay, shale or slate, perlite, vermiculite, and vegetable aggregates. Expanded clay is the most extensively manufactured lightweight aggregate throughout the world. The processes differ from one factory to another. There are mainly two methods for the preparation of raw materials before burning: the dry and the wet process. Perlite comes from volcanic aluminous silicious rock. (rhyolite family) containing more than 70 percent soil. Vermiculite is a natural material with a foliated structure with hydrated components including silica, magnesia, iron, and alumina. Also, some vegetable materials can be transformed to give stable non-destructive, waterproofing, non-combustible aggregates. Cork, wood, and rice ball aggregates are some types of vegetable aggregates.

Library of Congress Subject Headings

Concrete beams

Lightweight concrete

Reinforced concrete, Fiber

Format

application/pdf

Number of Pages

319

Publisher

South Dakota State University

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