Effect of temperature on mechanical properties of ultra‐high performance concrete

Abstract

High temperature mechanical property data are needed for evaluating fire resistance of structural members. Being a relatively new construction material, there is a lack of temperature-dependent mechanical property data on ultra-high performance concrete (UHPC). To address this knowledge gap, this paper presents results from an experimental study on the effect of temperature on mechanical properties of UHPC.Specimens made of two UHPC mixes: one with only steel fibers (UHPC-S) and the other with hybrid fibers, that is, both steel and polypropylene (UHPC-H), were tested under different heating conditions in 20 to 750 C temperature range. Compressive strength, tensile strength, stress-strain response, and elastic modulus of UHPC were evaluated at various temperatures. Results generated from these property tests on UHPC were compared with property relations specified in design codes for conventional normal strength concrete (NSC) and high strength concrete (HSC). The comparisons show that UHPC experiences faster degradation in compressive strength and elastic modulus as compared to conventional concrete. However, UHPC exhibits slower degradation in tensile strength and ductility at elevated temperatures due to the presence of steel fibers. Data generated from these property tests were utilized to propose relations for expressing the mechanical properties of UHPC as a function of temperature and these relations can be used as input to numerical models for evaluating fire resistance of structures made of UHPC.

Research on Dynamic Compressive Performance and Failure Mechanism Analysis of Concrete after High Temperature and Rapid Cooling

“…This is mainly due to the coupling effect of the randomness and correlation of discrete ratios for concrete. Under high strain rate conditions, the compressive peak strain of concrete is significantly higher than that under static conditions, and the compressive peak strain is gradually increased with the increase of strain rate [20,25,26]. can be observed from the SEM images.…”

“…According to Figure 10 and combined with Equation ( 1), the dynamic increase factor of concrete after different high temperature effects was obtained, as shown in Figure 11. The relationship between the compressive stress and strain rate of concrete under low and medium strain rates is generally expressed in the form of Equation ( 2) to quantitatively describe the relationship between the dynamic increase factor and strain rate [20,25].…”

“…When the temperature is 800 • C, the elastic modulus is increased from 1.46 × 10 3 MPa at the strain rate of 10 −5 /s to 1.55 × 10 3 MPa at the strain rate of 10 −2 /s, indicating an increase by 6.1% affected by the strain rate. In the relevant literature [20,25,26], research has been carried out on the elastic modulus of ordinary concrete at low and medium strain rates (10 −5 /s~10 −2 /s). Compared with static conditions, the elastic modulus of concrete is generally increased by 25-45% affected by the strain rate.…”

“…Bastami et al [19] studied the test data of post-high temperature concrete mechanical properties under compression and tension and established a high temperature intrinsic structure model. Bastami and Aslani et al [20] carried out an experimental study on the post-high temperature mechanical properties of ultra-high performance concrete and compared it with ordinary concrete and high performance concrete. The results showed that the deterioration rate of the compressive strength of ultra-high performance concrete after high temperature was relatively higher, while the deterioration rate of the tensile strength was relatively lower.…”

Performance of Different Concrete Types Exposed to Elevated Temperatures: A Review

“…For this regime, the UHPC samples have been heated to different temperatures under two different heating rates. Figure 29 and Figure 30 [ 97 ] show the effect of steel fibers and hybrid fibers (steel and PP fibers) and the effect of different heating rates on the relative compressive and splitting tensile strengths. The study states that the effect of PP fibers on UHPC is negligible.…”