Apparent activation energy of concrete in early age determined by adiabatic test

Abstract

The apparent activation energy of concrete in early age was determined by adiabatic temperature rise test with different initial temperatures. The influence of mineral admixtures such as fly ash, slag and silica fume on the apparent activation energy of concrete was investigated. The equivalent age that expresses the maturity of concrete was calculated to evaluate the cracking risk of concrete in structures. The results reveal that a substitution of 20% fly ash for Portland cement obviously decreases the apparent activation energy of concrete, however, a substitution of 10% silica fume for Portland cement increases the apparent activation. Finite element method analysis of a simulating concrete wall shows that the concrete containing 20% fly ash has the lowest cracking risk.

Keywords

mineral admixtures / apparent activation energy / equivalent age / cracking risk

References

[1] Maria K. Early Age Properties of High-strength/High-Performance concrete[J]. Cement&Concrete Composites, 2002, 24(2): 253-261.

[2] Tan K. F., John M. N. Performances of Concrete under Elevated Curing Temperature[J]. Journal of Wuhan University of Technology-Material Science Edition, 2004, 19(3): 65-67.

[3] Daloia L., Chanvillard G. Determining the Apparent Activation Energy of Concrete Ea-numerical Simulations of the Heat of Hydration of Cement[J]. Cement and Concrete Research, 2002, 32(8): 1 277-1 289.

[4] Wirquin E., Broda M., Duthoit B. Determination of the Apparent Activation Energy of One Concrete by Calorimetric and Mechanical Means Influence of a Superplasticizer[J]. Cement and Concrete Research, 2002, 32(8): 1 207-1 213.

[5] Weiping M., David S., Roger M., . Calorimetric Study of Cement Blends Containing Fly Ash, Silica Fume and Slag at Elevated Temperatures[J]. Cement, Concrete and Aggregates, 1994, 16(2): 93-99.

[6] Emborg M., Bernander S. Assessment of Risk of Thermal Cracking in Hardening Concrete[J]. Journal of Structure Engineering, ASCE, 1994, 120(10): 2 893-2 912.

[7] Kanstad T., Hammer T. A., Bjφntegaard, . Mechanical Properties of Young Concrete: Part I: Experiment Results Related to Test Methods and Temperature Effects[J]. Materials and Structures, 2003, 36(5): 218-225.

[8] Kjellsen K. O., Detwiler R. J. Reaction Kinetics of Portland Cement Mortars Hydrated at Different Temperatures[J]. Cement and Concrete Research, 1992, 22(1): 112-120.

[9] Chenju G. Maturity of Concrete: Method for Predicting Early-age Strength[J]. ACI Materials Journal, 1989, 86(4): 341-353.

[10] Springenschmid R. Thermal Cracking in Concrete at Early Age[C]. Proceedings of the International RILEM Symposium, 1995. London: E&FN SPON. 60-61.

[11] Bazant Z. P. Double-power Logarithmic Law for Concrete Creep[J]. Cement and Concrete Research, 1984, 14(6): 793-806.

[12] Atrushi D and Bosnjak D. Tensile Creep of Young High Performance Concrete[C]. The 3rd International PhD Symposium in Civil Engineering, Vienna, 2000