The influence of two South African fly ashes on the engineering properties of concrete.
Date
1991
Authors
Grieve, Graham Robert Hugh.
Journal Title
Journal ISSN
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Abstract
The South African cement producers would like to utilise cement extenders in cement
to increase manufacturing capacity at a relatively low cost. A" understanding of the
implications such a step might have for the cement user was required.
A study was made of the performance of portland cement blends made with fly ash
derived from the two commercial sources in South Africa that were being utilised by
1991. The performance of the blends was compared against the performance of
ordinary portland cement, the cement type to which the majority of users in South
Africa were exposed in the past.
An extensive literature study was provided which covered the latest research aspects
.ot the use of fly ash in many other parts or the world as well as mformation from local
South African research reports.
The ash concrete or mortar properties studied in the laboratory tests were as follows:
• workability
• rheology
• setting time
bleeding
• heat of hydration
The following properties of hardened concrete were studied in laboratory and simulated
site exposure tests:
• compressive strength
flexural strength
elastic modulus
• shrinkage
• creep
• permeability
• abrasion resistance
• carbonation
Some preliminary investigations were made into the effect that the use of fly ash had
on the effectiveness of chemical admixtures, and into the compressive strength
development of ternary (three component) blends.
As far as possible, use was made of standard SABS, BS, ASTM, DIN or RILEM test
methods although it was necessary to use other non-standard or modified test
methods in some cases to provide the necessary information. Appropriate references
or details have been provided where methods have deviated from standard methods.
Recommendations were made regarding the level of fly ash replacement which was
believed to be practical for site use for two categories of users, nameiy unsophisticated
users with a low !evel of understanding of concrete technology and relatively crude
methods of site batching and mixing, and sophisticated users with access to higher
levels of technology and equipment.
Description
A thesis submitted to the Faculty of Engineering, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy.
Keywords
Concrete -- Additives., Portland cement -- Additives -- South Africa., Cement -- Additives., Fly ash.