Simple criteria for evaluating sulphate attack in concrete
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Mixing , Blast furnaces , Slag cement , Concrete
- Type: Article
- Identifier: uj:5082 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13653
- Description: This paper attempts to analyse results from the standard test methods employed for sulphate attack and evaluates their correlations, consistency and contrasts, as well as physical observations. Data from expansions and mass change of 25 x25 x 285 mm mortar prisms and 75 x 75 x 285 mm concrete prisms were used. Mortar mixtures consisted of 1: 2.25: 0.5 cement to sand to water while concrete mixtures were of water-cementitious ratio (w/cm) of 0.45, 0.50, 0.65. Mixtures were made using CEM I 42.5N with or without 30, 50, 70% ground granulated blast furnace slag (GGBS) and stored in sodium sulphate solutions of 28 g/L and 50 g/L as SO4. Results show that ASTM C 1012 mortar expansion criteria of 0.10% corresponds to 1.2% mass gain. Similarly, concrete prism expansion criteria of 0.05% is equivalent to 0.75% mass gain. It is proposed that in the absence of expansion monitoring, the use of mass gain criteria of 1.2% mass in mortar prisms or 0.75% in concrete prisms may be sufficient for evaluating sulphate attack.
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The influence of fly ash and ground granulated blast-furnace slag on the elastic modulus of concrete
- Authors: Sun, Ryan W. , Fanourakis, George C.
- Date: 2016
- Subjects: Concrete - Elastic properties , Fly ash , Slag cement
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/217514 , uj:21649 , Citation: Sun, R.W. & Fanourakis, G.C. 2016. The influence of fly ash and ground granulated blast-furnace slag on the elastic modulus of concrete.
- Description: Abstract: The typical South African cementitious material used in industry today differs from what was commonly used in the past. With the move toward reducing carbon emissions in the cement manufacturing industry, extenders have now become a staple part of nearly all binder type materials. Along with this shift in cement type manufacturing, it is imperative that the effect of these common modern cement types be assessed in terms of their influence on the Elastic Modulus (E) of concrete. This study includes the assessment of 36 different concrete mixes where each mix differed in strength, aggregate type and cement type. A total of four cement types were utilized and chosen according to the type and proportion of extenders used. These cements were CEM I 52.5N, CEM II A-M 42.5N (15 % FA), CEM II A-M 42.5N additionally extended with 30 % FA, and CEM III A 32.5N (60 % GGBS). The E of concrete was determined for each mix and the results of specimens were grouped according to curing age and cement type for analytical purposes. Specimens were cast for 7, 28 and 56 day tests. The presence of FA had a slight influence on concrete E at early ages whereas GGBS concrete showed no significant differences in E compared to the CEM I concrete, for all ages included in this study. In general, the effect of FA and GGBS can be regarded negligible, except in the case where the E at an early ages is of vital concern.
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