Abstract
Due to the dense structure of ultra-high-performance concrete (UHPC), it is prone to explosive spalling at high temperatures. In this paper, flexural testing of UHPC and high-strength concrete (HSC) beams was carried out at room temperature and after being subjected to different levels of thermal exposure (300–500 °C). The cross-section of the beam specimen was 150 (width) × 200 (depth) mm, and its length was 1500 mm. The flexural and shear design of the beam specimens were carried out in accordance with the ACI 318M-14 code. All of the beams were singly reinforced with two #4 rebars (minimum reinforcement ratio) as a longitudinal tensile reinforcement at the bottom of the specimen and at an effective depth of 165 mm. The flexural load was applied using the three-point load method. The results show that, at room temperature and after being subjected to different thermal exposures, compared with the HSC specimens, the stiffness of the UHPC specimens in the post-cracking stage was relatively larger and the deflection under a given load was smaller. Moreover, whether at room temperature or after exposure to different thermal exposures, the ductility of the UHPC specimens was better than that of the HSC specimens.
Highlights
Concrete is a cement-based composite material that uses cement combined with aggregates, additives, etc., to form a hydraulic cementitious material [1]
The fire performance of ultra-high-performance concrete (UHPC) beams was tested under three load levels (20%, 40%, and 60% of the ultimate load at room temperature) and when exposed to a standard fire curve (ISO 834)
The average value of μ p of the UHPC beams was less than that of the high-strength concrete (HSC) beams regardless of whether it was at room temperature or after exposure to high temperatures
Summary
Concrete is a cement-based composite material that uses cement combined with aggregates, additives, etc., to form a hydraulic cementitious material [1]. Since the 1970s, due to the successful development of chemical admixtures (especially superplasticizers) and the application of mineral admixtures (mainly ground granulated blast furnace slag, silica fume, fly ash, etc.), various special concrete products have been developed one after another [2,3,4]. That there are three key factors in the production of UHPC, including improved micro and macro properties of the matrix composition, maximum particle packing density, and minimum size defects. The typical composition of UHPC generally includes cement, fine aggregates, fiber, mineral additives, and superplasticizer. The mix proportions of UHPC have several characteristics, including a low water-to-binder ratio, a large amount of very fine powders by using only fine sand for aggregates, a low water content
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