Influence of Supplementary Cementitious Materials and Superplasticisers on the Rheological Properties of Concrete
The influence of different supplementary cementitious materials (SCM) and superplasticisers on the rheological properties of concrete was investigated to identify potential compatibility issues. Superplasticisers and SCM often have unexpected interaction with certain cementitious compounds, resulting in concrete that is difficult to place in the fresh state due to poor rheological properties. Various mixes were designed containing different superplasticisers and/or SCM in different quantities. Slump, slump flow and concrete rheometer tests were conducted to determine the yield stress, plastic viscosity and thixotropic behaviour of the concrete. Obtained results showed that the specific Sulphonate Naphthalene Formaldehyde (SNF) and Polycarboxylic Ethers (PCE) superplasticisers used, reduced the yield stress, thixotropic behaviour and plastic viscosity of concrete. Modified Acrylic Polymer (ACR) superplasticiser showed a similar effect except for the plastic viscosity which increased at higher dosages. The addition of fly ash and slag to concrete containing superplasticiser had little effect on the rheology and showed similar results as mixes only containing superplasticiser. The use of superplasticiser in conjunction with silica fumes caused a decrease in yield stress and thixotropic behaviour while plastic viscosity increased. The use of superplasticiser in conjunction with higher than normal dosages of gypsum also caused a decrease in yield stress and thixotropic behaviour but had negligible effect on plastic viscosity. It was also found that the use of PCE superplasticiser in conjunction with gypsum, used to control the set of concrete, can cause potential slump loss issues.
This work is based on the research supported in part by the National Research Foundation of South Africa. Any opinion, finding and conclusions or recommendation expressed in this material is that of the author(s) and the NRF does not accept any liability on this regard. The support of Pretoria Portland Cement (PPC) and Chryso South Africa are also gratefully acknowledged.
- Chakkamalayath, J., et al.: Cement-superplasticiser compatibility - Issues and challenges. Indian Concr. J. (2011). https://www.researchgate.net/publication/286714849_Cement-superplasticiser_compatibility_-_Issues_and_challenges. Accessed 3 Apr 2019
- Chryso, S.A.: General Catalogue 1ste Edition: 2007. Chryso South Africa, Boksburg (2007)Google Scholar
- Domone, P., Illston, J. (eds.): Construction Materials, 4th edn. Spon Press, New York (2010)Google Scholar
- Koehler, E.P., Fowler, D.W.: Development of a Portable Rheometer for Fresh Portland Cement Concrete (ICAR Report 105-3). International Center for Aggregates Research, Austin, TX (2004)Google Scholar
- Mapei, S.A.: General Catalogue 1ste Edition: 2017. Mapei South Africa, Roodekop Germiston (2017)Google Scholar
- Quanji, Z.: Thixotropic behavior of cement-based materials: effect of clay and cement types (2010). https://lib.dr.iastate.edu/etd/11724. Accessed 15 Feb 2019
- SANS 5861-1, S.: SANS 5861-1:2006 : 2006 SOUTH AFRICAN NATIONAL STANDARD Concrete tests Part 1 : Mixing fresh concrete in the laboratory, pp. 2–6 (2006)Google Scholar
- SANS 5862-1, S.: SANS 5862-1:2006: 2006 SOUTH AFRICAN NATIONAL STANDARD Concrete tests - Consistence of freshly mixed concrete - Slump test, pp. 1–5 (2006)Google Scholar