The production of precast prestressed concrete : a study of two fabrication plants

Abstract

Man has chosen to seek the best possible conditions of life at greater effort; in fact the choice was forced upon him by his need for action. He could abandon this search only by ceasing to be himself, and this search is the cause of the enormous material development of our civilisation. The greatest advances undoubtedly, have occurred in the technical world and the rapidity of the diffusion of the idea of prestressing in the last fifty odd years is due precisely to the fact that it constitutes a trickle in that vast current which nears humanity forward towards an extension of the material powers. Prestress is more than a technique; it is a general principle - a simple one at that, it involves the artificial creation of permanent stresses within a structure, such that in combination with the stress due to the external load, the total stresses remain everywhere within the limits of stress that the material can support indefinitely. The methods employed, however, vary considerably. It is therefore obviously impossible to give a general review of all the possible applications of prestress as this would involve the whole field of civil engineering. In this work which has been divided into four chapters the objective has been to: - provide a background to the general principles of prestressed concrete and prefabrication and the methods presently involved in their execution. - discuss the various characteristics of the materials making up prestressed concrete and their influence on the finished product. - describe the process of production of hollow-core slabs, where two local plants are treated. - do actual research and structural tests on a series of slabs having two different cross-sections and produced by two different processes. Tests on the concrete mix used were also held to try to determine a possible relationship between tests which could be carried out in a laboratory and the performance of the finished product itself. These tests were also held with the intention in mind to relate the actual load carrying capacities of the slabs to those quoted by the respective managers of the plants.