Document Archives

Lightweight Aggregates and Concrete

• ID:

  386

• ESCSI:

  4000.046

• Author:

  Lewis, D.W.

• Publication Name:

  Short Course

• Type of Publication:

  Paper

• Publisher:

  Author

• Dated:

  1967

• Issue/Volume:

  November 13

• Other ID:

• Page(s):

  1-8

• Reference List:

  N

• Abstract:

  General discussion of lightweight aggregate and lightweight aggregate concretes.Concrete is, as we all know, an extremely versatile construction material. However, for some applications, the weight of ordinary concrete is a disadvantage — for example, in construction where poor foundation conditions exist, in locations where long spans are desirable or necessary in beams, and in cantilevered sections. Lightweight concrete can often be employed economically in such cases, where concretes or normal or ordinary weights could not be used. Thus lightweight concrete has the principal function of extending the uses and applications of concrete, rather than as a replacement for conventional concrete. It has been estimated that well over three-fourths of the lightweight structural concrete used is for applications where no concrete would be employed if it were not possible to obtain the special characteristics of the lightweight products.
  LIGHTWEIGHT AGGREGATES AND THEIR CHARACTERISTICS
  Let us look for a moment at the various types of lightweight aggregates, their characteristics and applications, and the ways in which they differ from the conventional or normal weight aggregates. Lightweight aggregates are covered by three ASTM tentative specifications: C 330 – Lightweight Aggregates for Structural Concretes, C 332 – Lightweight Aggregates for Insulating Concrete, and C 331 – Lightweight Aggregates for Concrete Masonry Units. Many types of lightweight aggregates are included in all three of these specifications.
  The last group of materials – and the one of major interest from the standpoint of the ready-mixed concrete industry – is one we might designate as the “structural lightweight aggregates.” Actually they are used in all types of applications: in structural lightweight concrete, in concrete masonry units, and – with high air contents – in insulating concretes. Two natural aggregates are included in this category: pumice and scoria, both of which are light, cellular volcanic rocks found in the West United States. The others of major importance are by-product or manufactured aggregates, and include expanded blast-furnace slag and the expanded shales, clays, and slates.
  The basic principles, however, that should be followed to get a good lightweight concrete job, are identical to those for any concrete: proper mix design and slump, avoidance of excessive handling and movement of aggregates or of concretes, avoidance of overworking or vibration, and proper finishing and curing.