Load Induced Thermal Strains in Steel Fibre Reinforced Concrete Subjected to Uniaxial Compression

Abstract:

The effect of fibre reinforcement on Load Induced Thermal Strains (LITS) has not yet been significantly investigated up to now. Creep is becoming a key research topic only in the last few years. A semi-empirical model able to take into account both the thermo-mechanical damage associated to coarse aggregates and the thermo-chemical damage induced in the matrix and calibrated on the basis of the main results on plain concrete available in the scientific literature is presented. Some tests in uniaxial compression on Fibre Reinforced Concrete (FRC) cylinders characterized by a long age – 11-years-old – have been investigated and compared with the model to highlight fibre effects, if any. The uniaxial compressive strength at 28 days of the SFRC was 75 MPa; the specimens after 11 years showed a compressive strength exceeding 110 MPa. A strong increase of SLS residual strength was observed in post-cracking tension due to the long aging, while ULS residual strengths weakly increased. The cylindrical specimens were exposed to a maximum temperature of 200°C and 400°C and loaded with two load thresholds corresponding to 20% and 40% of the compressive strength detected at 28 days of aging, that means about 12.5% and 25% of the 11-years-old specimens. Two paths were investigated: pre-heated specimens up to 200°C or 400°C, then loaded with a compression stress equal to 0.2f_c,28 and 0.4f_c,28; and pre-loaded specimens up to 0.2f_c,28 and 0.4f_c,28 and then heated up to 200°C or 400°C. The duration of each test did not exceed 12 hours. Two main fibre effects were observed: a significant reduction of irreversible strains when the specimens were loaded and then heated and cooled and a different evolution in LITS passing from 200°C to 400°C, characterized by a significant reduction of the expected deformation.

• Periodical: Key Engineering Materials (Volume 711)
• Pages: 525-532
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.711.525
• Online since: September 2016
• Authors: Thomaz E.T. Buttignol*, Matteo Colombo, Marco di Prisco
• Keywords: Aging, Bending, Classification, High Temperature, Load Induced Thermal Strain (LITS), Steel Fibre Reinforced Concrete (SFRC), Transient Creep

References

[1] Sabeur, H.; Meftah, F.; Colina, H. and Platret, G.: Correlation between transient creep of concrete and its dehydration. Magazine of Concrete Research, n° 3, April, 2008, pp.157-163, (2008).

DOI: 10.1680/macr.2007.00132

[2] Diederichs, U. and Mertzsch, O.: Behavior of Ultra High Strength Concrete at High Temperatures. Ultra High Performance Concrete (UHPC): Proceedings of the Second international Symposium on Ultra High Performance Concrete, Kassel, Kassel university Press, 2008, pp.347-354.

DOI: 10.21838/uhpc.16728

[3] Sabeur, H. and Colina, H.: Effect of heating–cooling cycles on transient creep strain of high performance, high strength and ordinary concrete under service and accidental conditions. Materials and Structures, (2014).

DOI: 10.1617/s11527-014-0254-2

[4] Khoury, G.: Strain of heated concrete during two thermal cycles. Part 3: isolation of strain components and strain model development. Magazine of Concrete Research, nº 7, pp.421-435, (2006).

DOI: 10.1680/macr.2006.58.7.421

[5] Tao, J.; Liu, X.; Yuan, Y. and Taerwe, L.: Transient strain of self-compacting concrete loaded in compression heated to 700°C. Materials and Structures, nº 46, pp.191-201, (2013).

DOI: 10.1617/s11527-012-9894-2

[6] Mindeguia, J. -C.; Hager, I.; Pimienta, P.; Carré, H. and La Borderie, C.: Parametrical study of transient thermal strain of ordinary and high performance concrete. Cement and Concrete Research, nº 48, pp.40-52, (2013).

DOI: 10.1016/j.cemconres.2013.02.004

[7] Huismann, S; Weise, F.; Meng, B. and Schneider, U.: Transient strain of high strength concrete at elevated temperatures and the impact of polypropylene fibers. Materials and Structures, nº 45, pp.793-801, (2012).

DOI: 10.1617/s11527-011-9798-6

[8] Wu, B.; et. al.: Creep Behavior of High-Strength Concrete with Polypropylene Fibers at Elevated Temperatures. ACI Materials Journal, March-April, pp.176-184, (2010).

DOI: 10.14359/51663581

[9] EN 1992-1. Eurocode 2: Design of concrete structures. Part 1-2 - General rules - Structural Fire Design. British Standards, (2004).

[10] Buttignol, T. E. T. On the Load Induced Thermal Strain for Plain and Steel Fiber Reinforced Concrete Subjected to Uniaxial Loading. PhD thesis, Politecnico di Milano, (2016).

DOI: 10.1016/j.cemconres.2019.105896

[11] Hager, I., Thermal behavior of high performance concretes at high temperature - evolution of mechanical properties, (PhD Thesis) l'Ecole Nationale des Ponts et Chaussées, (2005).

[12] Khoury, G. A.: Strain of heated concrete during two thermal cycles. Part 1: strain over two cycles, during first heating and at subsequent constant temperature. Magazine of Concrete Research, nº 6, pp.367-385, (2006).

DOI: 10.1680/macr.2006.58.6.367

[13] Colombo, M.; di Prisco, M. and Felicetti, R.: Mechanical properties of steel fibre reinforced concrete exposed at high temperatures. Materials and Structures, nº 43, p.475–491, (2010).

DOI: 10.1617/s11527-009-9504-0