Hydraulic concrete production

Concrete, a material that is sometimes unloved and often misunderstood, is capable of remarkable performance when used in structures such as major bridges (the Pont de Normandie in France or the Confederation Bridge in Canada) or as the framework for high-rise buildings.

The safety of these structures obviously depends on the adequacy of the characteristics obtained during manufacture and installation of the material, compared with those taken into account in the calculations. In all cases, the predominant quality to be sought is consistency of performance, and the emphasis is as much on minimizing the coefficient of variation of the characteristics obtained as on aiming for extraordinary averages.

The manufacture of concrete is the first irreversible operation in the construction of a structure, and its correct execution determines all the properties that the concrete will acquire, properties that are the basis of the structure's dimensioning. This phase is all the more delicate in that it starts with inert constituents, some of whose characteristics are little or not at all mastered, to create a "living" material, the main component of the structure. By bringing these constituents together according to a specific scheme [1] , the manufacturing process initiates a series of physico-chemical reactions that will continue throughout the life of the structure.

Today's awareness of the need to save "noble" materials means doing our utmost to take advantage of the potential of the components, and therefore respecting the laws of physical constitution of the mixture that the chosen scheme has normally optimized.

The irreversibility of the reactions means that it is essential to reproduce this operation identically throughout the project.

This document analyses the different phases of concrete production.

Without going into the technological aspects of materials and equipment, it defines the objectives and functions of the equipment used to meet these performance and durability objectives for both batch and continuous production modes [2] . It presents the latest knowledge acquired from both laboratory research and on-site observations.

It is divided into three parts.

Concrete production describes how to "see" concrete in order to satisfy the customer's expressed or sometimes implicit requirements. This section also describes the different production methods, whether for ready-mix concrete, on-site production or production of prefabricated elements.

The making of concrete...