Abstract
This paper presents the results of an experimental study to investigate dynamic properties of polypropylene fiber-reinforced concrete beams with lightweight expanded shale (ES) and tire-derived aggregates (TDA). The mixture design followed past experiences in combining ES and TDA to enhance toughness and energy absorption in flexural behavior. The new mixture also contained 2% fiber by volume to improve such properties further. Experiments included compressive testing on cylindrical specimens as well as flexural testing on rectangular specimens to verify mechanical properties of fiber-reinforced tire-derived lightweight aggregate concrete (FRTDLWAC) subject to static loading. The results of these experiments confirmed reduction of mechanical strength due to addition of TDA and improvements in flexural strength due to fiber reinforcement. The dynamic testing included non-destructive impact loads applied to flexural specimens using a standard Schmidt hammer. A high-speed camera recorded the response of the system at 200 frames per second to allow detailed observations and measurements. Interpretation of energy-based dynamic results revealed that TDA enhances energy absorption through damping in flexural behavior. Results also indicated that fiber reinforcement reduces the amount of absorbed dynamic energy, even though; it enhances the absorbed strain energy due to crack bridging effect.
Highlights
The energy absorption and damping characteristics of structural materials are essential elements in determining the performance-based capacity of structures subjected to dynamic loads [1,2,3]
The second set of specimens had the same constituents as mix-1, but 80% of expanded shale aggregates were replaced by tire-derived aggregates (TDA) with uniform gradation, labeled as Tire-Derived Lightweight Aggregate Concrete (TDLWAC)
The obtained results for the mechanical properties of TDLWAC and LWAC samples were in agreement with existing literature
Summary
The energy absorption and damping characteristics of structural materials are essential elements in determining the performance-based capacity of structures subjected to dynamic loads [1,2,3]. It has been shown that adding rubber aggregates to a concrete matrix decreases the physical and mechanical properties of the hardened concrete such as density, compressive strength, and modulus of elasticity [6]. Existing literature shows that substitution of aggregates with rubber particles results in a similar trend. Typical conclusions of such observations includes suggestive limits of rubber content for structural and non-structural concrete, say 25% and 40% of total aggregate volume respectively [7,8,9]. Miller and Tehrani (2017) showed that the replacement of lightweight coarse aggregates with rubber aggregates by 20, 40, 60, 80 and 100% causes a decrease in mechanical properties as rubber content increased. Toughness was shown to increase with the addition of rubber content sometimes as much as twice when comparing maximum-rubber-content to zero-rubber-content mixes [10]
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