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Influence of elevated temperature on the engineering properties of ultra-high-performance fiber-reinforced concrete

Abadel Aref A., Khan M. Iqbal, Masmoudi Radhouane

Materials Science Poland

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2023

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Vol. 41, No. 1

140--160

EN

This paper investigates the effect of high temperatures on the compressive strength, flexural strength, and splitting tensile strength of ultra-high-performance concrete (UHPC), and ultra-high-performance, fiber-reinforced concrete (UHPFRC). The experimental variables in this study were fiber type, fiber content, and high-temperature exposure levels. Three different types of fibers were evaluated, including steel fibers, polypropylene (PP), and polyvinyl alcohol (PVA) fibers. Six concrete mixes were prepared with and without different combinations of fibers. One mix was made with no fibers. Others were made with either steel fibers alone; a hybrid of steel fibers and PVA; and a hybrid system of steel, PP, and PVA fibers. These mixes were tested under a range of temperatures and compared for strength. The UHPC and UHPFRC were exposed to high temperatures at 100°C, 300°C, 400°C, and 500°C for 3 hours. The results showed that UHPFRC did not exhibit any significant degradation when exposed to 100°C. However, reductions of approximately 18% to 25%, 12% to 22%, and 14% to 25% in the compressive strength, splitting tensile strength, and flexural strength were observed when the UHPFRC was exposed to 400°C. UHPFRC made of steel fibers showed higher mechanical properties after exposure to 400°C compared to UHPFRC made of PP and PVA fibers. The results also demonstrate the use of PVA and/or PP fibers, along with steel fiber, to withstand the effects of highly elevated temperature and prevent spalling of UHPC after exposure to elevated temperature. The observed spalling was a direct result of the melting and evaporation of PVA and/or PP fibers when exposed to high temperature, an effect that was confirmed using scanning electron microscopy.

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Results concerning the analysis of generalized Mittag-Leffler function associated with Euler type integrals

Khan N. U., Khan M. Iqbal

Fasciculi Mathematici

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2023

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nr 66

49--59

EN

In this paper, we obtain some results on certain Euler type integrals involving generalized Mittag-Leffler function defined by Salim and Faraj [20]. Further, we deduce some special cases involving Mittag-Leffler function, Wiman function, Prabhakar function, exponential, binomial and confluent hypergeometric functions. Moreover, we obtain a relation between Laguerre polynomials and Whittakar function.

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Development of a novel 124 MPa strength green reactive powder concrete employing waste glass and locally available cement

Abellan-Garcia Joaquin, Redondo‑Mosquera Jesús, Khan M. Iqbal, Abbas Yassir M., Castro-Cabeza Andrea

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e161, 2023

EN

In this study, a new reactive powder concrete (RPC) was developed, with environmentally friendly typical RPC components obtained from ground quartz substituted by the waste glass. In this manner, the carbon footprint and final cost are minimized by replacing aggregates and reducing cement. A challenge in this study was using high-celite phase available cement and avoiding the alkali-silica reaction. The Box–Wilson design and Derringer–Suich optimization were used to create an RPC mixture with a low cement content and high-volume waste glass dosage that achieved a compressive strength of more than 120 MPa. It was demonstrated that having all ground waste glass particles smaller than 1000 µm is not sufficient to prevent the alkali-silica expansion. Furthermore, commercially available cement with a high celite proportion had a modest beneficial influence on the compressive strength at an early-age but a significant detrimental impact on the RPC’s compressive strength at 28 days. Finally, the current study proved the potential of manufacturing an RPC that satisfied the strength threshold criterion while utilizing a local cement with over 12% celite and a substantial volume of waste glass powder comprising more than half of the RPC weight.