Fly ash (FA) is important alternative or supplement to cement to reduce the environmental impact of concrete industry. However, early age strength development of FA is a concern due to the slower reaction rate of FA compared to cement. This paper examines the early age hydration properties of cement paste containing typical Australian FA and establishes correlations between the degree of hydration and the early-age strength development properties of mortar mixes. All mixes have the same mixture proportion of water to binder (w:b) ratio. FA sourced from different power plants are used for the tests. Cement replacement levels of 0%, 10%, 30% and 40% by mass are considered. The degree of hydration was established from the heat production of the mixes by using isothermal calorimetry. The hydration properties were characterized by hydration curve parameters obtained from curve fitting. The results show that both hydration rate and strength of the binder materials (FA and cement) were reduced with higher replacement levels of FA contributing to a reduced hydration rate at early ages. Linear relationship could be obtained between degree of hydration and strength at early ages for all the fly ash binders.
KeywordsFly AshEarly Age StrengthIsothermal CalorimetryDegree of Hydration
EPA (2010) U.S. Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Portland Cement Industry. [Cited 2017 20/04]; Available from: https://www.epa.gov/sites/production/files/2015-12/documents/cement.pdf
Mamlouk, M.S. and Zaniewski, J.P. (2011) Materials for Civil and Construction Engineers. Prentice Hall, Upper Saddle River, NJ.
Thomas, M.D.A. (2007) Optimizing the Use of Fly Ash in Concrete. Portland Cement Association, Skokie, IL, Vol. 5420.
Hemalatha, T. and Ramaswamy, A. (2017) A Review on Fly Ash Characteristics towards Promoting High Volume Utilization in Developing Sustainable Concrete. Journal of Cleaner Production, 147, 546-559. https://doi.org/10.1016/j.jclepro.2017.01.114
Sofi, M., Mendis, P.A. and Baweja, D. (2012) Estimating Early-Age In Situ Strength Development of Concrete Slabs. Construction and Building Materials, 29, 659-666. https://doi.org/10.1016/j.conbuildmat.2011.10.019
Goto, S. (2009) Hydration of Hydraulic Materials—A Discussion on Heat Liberation and Strength Development. Advances in Cement Research, 21(3), 113-117. https://doi.org/10.1680/adcr.8.00041
Mehta, P.K. (2004) High-Performance, High-Volume Fly Ash Concrete for Sustainable Development. In Proceedings of the International Workshop on Sustainable Development and Concrete Technology, Iowa State University, Ames, IA, USA, May 2004, 3-14.
Bentz, D.P., Zunino, F. and Lootens, D. (2016) Chemical vs. Physical Acceleration of Cement Hydration. Concrete International: Design & Construction, 38(11), 37-44.
Pane, I. and Hansen, W. (2005) Investigation of Blended Cement Hydration by Isothermal Calorimetry and Thermal Analysis. Cement and Concrete Research, 35(6), 1155-1164. https://doi.org/10.1016/j.cemconres.2004.10.027
Center, N.C.P.T. (2011) Isothermal Calorimetry of Cement. [Cited 2017 15/04]; Available from: http://www.cptechcenter.org/ncc/TTCC-NCC-documents/F2008-F2011/09IsothermalCalorimetry_000.pdf
De Schutter, G. and Taerwe, L. (1996) Degree of Hydration-Based Description of Mechanical Properties of Early Age Concrete. Materials and Structures, 29(6), 335. https://doi.org/10.1007/BF02486341
Bentz, D.P., Barrett, T., De la Varga, I. and Weiss, W.J. (2012) Relating Compressive Strength to Heat Release in Mortars. Advances in Civil Engineering Materials, 1, 1-16. https://doi.org/10.1520/ACEM20120002
Tanesi, J. and Ardani, A. (2013) Isothermal Calorimetry as a Tool to Evaluate Early-Age Performance of FA Mixtures. Journal of the Transportation Research Board, 2342, 42-53. https://doi.org/10.3141/2342-06
Shafiq, N. (2011) Degree of Hydration and Compressive Strength of Conditioned Samples Made of Normal and Blended Cement System. KSCE Journal of Civil Engineering, 15(7), 1253. https://doi.org/10.1007/s12205-011-1193-x
Khoury, G.A., Grainger, B.N. and Sullivan, P.J. (1985) Transient Thermal Strain of Concrete: Literature Review, Conditions within Specimen and Behaviour of Individual Constituents. Magazine of Concrete Research, 37(132), 131-144. https://doi.org/10.1680/macr.1985.37.132.131
Bentz, D.P. and Weiss, W.J. (2011) Internal Curing: A 2010 State-of-the-Art Review. US Department of Commerce, National Institute of Standards and Technology, Gaithersburg, Maryland. https://doi.org/10.6028/NIST.IR.7765
ASTM C618-05, American Society of Testing and Materials (2005) Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. West Conshohocken.
Australia, F. (2010) Sustainable Solutions for the Construction Industry. http://www.flyashaustralia.com.au/WhatIsFlyash.aspx
Schindler, A.K. and Folliard, K.J. (2003) Influence of Supplementary Cementing Materials on the Heat of Hydration of Concrete. In Advances in Cement and Concrete IX Conference, Copper Mountain Conference Resort, Colorado, 10-14 August 2003.
Bogue, R.H. (1947) The Chemistry of Portland Cement. Reinhold Publishing Corporation, New York.
Schindler, A.K. and Folliard, K.J. (2005) Heat of Hydration Models for Cementitious Materials. ACI Materials Journal, 102, 24-33.
Kwan, A.K.H., Fung, W.W.S., Chen, J.J. and Ng, P.L. (2011) Heat Generation of Curing Fly Ash Concrete at Different w/cm. ACI Materials Journal, 108(3), 307-315.
Freiesleben Hansen, P. and Pedersen, E.J. (1985) Curing of Concrete 1, Comité Euro-International du Béton, Switzerland. Structures. Draft DEB—Guide to Durable Concrete Structures.
Australian Standard (2014) 1012.8.1: Methods of Testing Concrete-Method for Making and Curing Concrete-Compression and Indirect Tensile Test Specimens. Standards Australia, Sydney.
Mills, R.H. (1966) Factors Influencing Cessation of Hydration in Water Cured Cement Pastes. Highway Research Board Special Report, 90.
Taplin, J.H. (1959) A Method for Following the Hydration Reaction in Portland Cement Paste.
Xu, Q., Hu, J., Ruiz, J.M., Wang, K. and Ge, Z. (2010) Isothermal Calorimetry Tests and Modeling of Cement Hydration Parameters. Thermochimica Acta, 499(1-2), 91-99. https://doi.org/10.1016/j.tca.2009.11.007
Deschner, F., Winnefeld, F., Lothenbach, B., Seufert, S., Schwesig, P., Dittrich, S., Goetz-Neunhoeffer, F. and Neubauer, J. (2012) Hydration of Portland Cement with High Replacement by Siliceous Fly Ash. Cement and Concrete Research, 42(10), 1389-1400. https://doi.org/10.1016/j.cemconres.2012.06.009