Material Characterization Approach for Modeling High-Strength Concrete after Cooling from Elevated Temperatures

Abstract

Advanced numerical modelling of high-strength concrete ( c > 60 MPa) structures designed to withstand severe thermal conditions requires detailed and reliable information on the mechanical properties of the material exposed to elevated temperatures. The only uniaxial compressive strength variation with temperature is not enough to satisfy the big number of parameters often required by advanced non-linear constitutive models.For this reason, a complete experimental investigation is required. The paper takes a commonly used high strength concrete ( c = 73 MPa) as an example to describe a comprehensive experimental approach instrumental to the parameter definition and calibration of common constitutive models for concrete. The present study not only studied the overall compressive and tensile behaviour of the case study material, but also investigated the effect of elevated temperatures on the specific fracture energy and the evolution of internal damage, in residual conditions after a single thermal cycle at 200, 400 and 600 °C.

Physicochemical, Mineralogical, and Mechanical Properties of Calcium Aluminate Cement Concrete Exposed to Elevated Temperatures

“…Due to the importance of the different performances of various concretes against high temperatures, in this section, an attempt is made to provide a comparison between the residual mechanical properties of CACC with those of other concretes (investigated in the literature) after exposure to heat, with some parameters being variable. By comparing the residual compressive strength of different concretes shown in Figure 14 [ 15 , 40 , 41 , 54 , 57 ], the better performance of CACC, particularly for temperatures higher than 400 °C, is observed; this results from the lower dehydration and chemical water evaporation in the CACC cement matrix relative to OPC. In the results reported by Khaligh, the residual compressive strength percentage is higher than that reported in this study; this is the result of a higher alumina content in the cement and a higher heating rate in that study.…”

Experimental investigation on the structural response of RC slabs subjected to combined fire and blast

“…A detailed and comprehensive discussion of the mechanical properties of the concrete used for the RC slabs is given in [34]. Mechanical properties of concrete were evaluated at ambient and high temperatures.…”

“…Two nominally identical specimens were tested in residual conditions at different temperature levels (20,200,400, and 600 °C). Further details on the material test set-up, specimen sizes and instrumentation can also be found in [34]. The average modulus of elasticity from the three tests at 20 °C, and its standard deviation were equal to 𝐸 𝑐,20 = 27609 ± 829 MPa.…”

“…Complete stress-strain and stress-COD curves were measured during the UCTs and UTTs, in addition to peak compressive strength and peak tensile strength, but are omitted here for the sake of brevity. A detailed and comprehensive discussion of the mechanical properties of concrete exposed to high temperatures is given in [34].…”

“…For this purpose, a comprehensive experimental program was carried out at Politecnico di Milano in conjunction with the Norwegian University of Science and Technology (NTNU), adopting a shock tube and gas burner equipment, able to apply a fire and blast sequence [33]. The work presented in this study is part of a larger research programme in which static slab tests and material tests, have been performed for further understanding of the slab's behaviour [34].…”