8. Aggregates for concrete
Published:January 01, 2001
Concrete may be defined as a mixture of water, cement or binder, and aggregate, where the water and cement or binder form the paste and the aggregate forms the inert filler. In absolute volume terms the aggregate amounts to 60–80% of the volume of concrete and is, therefore, the major constituent. The aggregate type and volume influences the properties of concrete, its mix proportions and its economy.
The desirable and undesirable properties of aggregates for concrete have been thoroughly reviewed in a number of texts on concrete technology (Orchard 1976; American Society for Testing and Materials 1978; Murdock, Brook & Dewar 1997; Fookes 1980; Neville 1995). In practice, difficulties are frequently encountered in translating these properties into specification requirements for aggregates, or in assessing aggregate test results to determine compliance or otherwise with already specified parameters. This chapter considers the principal properties of concrete aggregates with the aim of assisting in the selection of appropriate specification requirements.
The essential requirement of an aggregate for concrete is that it remains stable within the concrete and in the particular environment throughout the design life of the concrete. The characteristics of the aggregate must not affect adversely the performance or cost of the concrete in either the fresh or hardened state.
For both technical and contractual reasons, these requirements have to be defined quantitatively. This involves the selection of relevant tests and assessment procedures and the specification of appropriate acceptance criteria.Hence the need for continued
Figures & Tables
Aggregates: Sand, gravel and crushed rock aggregates for construction purposes
In 1985, the Geological Society published Aggregates as the first volume in its Engineering Geology Special Publication series. It met with immediate acclaim, being awarded the Brewis Trophy by SAGA in 1986.
“If your work involves the use of aggregates, buy this book and read no further; this volume will be an essential and valuable reference that you will use for many years.” (Canadian Geotechnical Journal 1988)
In 1989, the working party whose work had resulted in the publication of Aggregates was reconvened to revise, update and extend their report. Each chapter was reviewed by independent referees. The second and greatly improved edition, published in 1993 and reprinted in 1998, represented the distillation of a vast body of knowledge and experience held not only by the members of the working party, but also by many international experts, scientists and engineers who contributed as reviewers, referees and corresponding authors.
Owing to continued demand for this unique reference book, a group of aggregate specialists was convened in 1999 in order to review thoroughly and update Aggregates for this third edition.
Outline of contents: Introduction; Occurrences; Field investigations; Extraction; Processing; Classification; Testing; Aggregates for concrete; Aggregates for mortar; Unbound aggregates; Bituminous bound aggregates; Rail ballast; Filter media; Appendix: Aggregate properties; Glossary; Index.
Working Party Members and/or third edition Reviewers: Mr L. Collis (formerly Sandberg); Professor P. G. Fookes (Chairman; consulting engineering geologist), Mr R. A. Fox (formerly RMC Aggregates (UK) Ltd), Professor G. P. Hammersley (formerly Laing Technology Group, now BRE), Mr P. M. Harris (formerly BGS), Dr I. E. Higginbottom (formerly Wimpey Environmental Ltd), Mr J. Lay (RMC Aggregates (UK) Ltd), Dr G. Lees (formerly University of Birmingham), Mr D. I. Roberts (Land and Mineral Resource consultants), Mr A. R. Roeder (formerly British Cement Association), Dr I. Sims (Secretary; formerly Sandberg, now STATS Limited), Dr M. R. Smith (formerly Imperial College, now the Institute of Quarrying), Dr R. G. Thurrell (formerly BGS), Dr G. West (formerly TRL).