The reinforcement of ultra-high-performance concrete (UHPC) with fibers was investigated in this study. Concrete is the most widely used manmade construction material, and UHPC has remarkable mechanical properties. The mechanical properties of UHPC can be modified by a variety of curing procedures and the amount of cement used. This study aimed to examine the impact of fiber reinforcement, temperature, and exposure time on UHPC. Initially, the temperature for UHPC was changed from 300 °C to 500 °C and the exposure time set to 1 and 2 h. Various combinations of the ultrasonic pulse, thermal conductivity, compressive strength, flexural strength, splitting, modulus of elasticity, and drop hammer impact (impact resistance, impact energy, and ductility index) were investigated after 91 days of steam curing. For steam curing, the temperature was kept at 90 °C for three days. The mechanical characteristics of UHPC were the primary focus of this research. The test results showed that the accelerated curing regime achieved a maximum compressive strength of 102.6 MPa for UHPC specimens without fibers and 124.7 MPa for UHPC specimens with fibers, which represents a 22% increase in compressive strength. When compared to UHPC without fibers, all the qualities of UHPC with fibers were improved, especially when subjected to high temperatures. The incorporation of hybrid synthetic waste fibers was a key aspect in developing new ultra-high-strength concrete features.
The main objective of this paper is to investigate the effect of adding discrete glass fibers on the behavior of reinforced concrete (RC) beams under different fire and cooling conditions. Eighteen beams with different concrete compressive strengths were tested to study the behavior of reinforced concrete (RC) beams containing discrete glass fibers when exposed to different fire and cooling conditions. Nine beams were prepared from normal strength concrete (NSC) with compressive strength equal to 35 MPa while the other beams were prepared from high strength concrete (HSC) with compressive strength equal to 60 MPa. The beams contained different contents of discrete glass fibers. The modes of failure of tested specimens show that the crack patterns change according to fire condition and fiber content. Analysis of test results show that adding discrete glass fibers to NSC increased the residual stiffness of the tested specimens after firing and decreased the rate of the deflection gain during firing. Also adding fibers to concrete has a limited positive effect on the ultimate strength of the specimens compared to the control specimens. Its effect on deflection due to fire is more pronounced. Finally, the recommended optimum ratio of discrete glass fibers is not more than 0.5% of the total concrete weight.ª 2014 Production and hosting by Elsevier B.V. on behalf
Internal ballistic process of two-stage light-gas gun has been solved by many investigators using different approaches. This paper presents two different approaches to predict the interior ballistic parameters of such gun. The first approach is based on isentropic compression of the light gas in the gun pump, whereas the second approach depends on the theory for piston operated compressor in which shock wave was formed and heated the light gas. For each approach, the governing equations have been used to construct a computer program. Predicted time histories of gun parameters associated with gun firing are presented. The predicted results of each approach are compared with available experimental measurements of other investigators; good agreements are generally obtained. For both approaches, samples of the predicted time histories for powder chamber pressure, pump tube pressure, piston velocity and its travel along the gun tube, and projectile velocity and its travel along the barrel are presented for two calibers (12.7 and 28.6 mm), together with relevant analyses and discussions.
Lightweight reinforced concrete (LWC) is widely used in various reinforced concrete (RC) applications, such as its use in diverse types of reinforced concrete slabs. The aim of this study is to analyze the behavior of reinforced foam concrete slabs (flat slab type) that are exposed to fire conditions under the influence of eccentric loads as well as concentric loads. This analysis has been done using the finite element method by a (ANSYS) software program. The validity of the adopted models was verified through comparison with a previous experimental study. The studied specimens were eleven reinforced concrete flat slabs with a thickness of 150 mm. The lightweight polystyrene foam concrete was used in these specimens with a density of 1820 kg/m3. The results showed that the fire effect lead to a decrease in the maximum carrying load of foam concrete slabs by 25%. Also, by comparing the finite element results with the selected experimental study, the results showed a great agreement with the analytical study used in this research.
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