Abstract-This study presented an optimization of the suitability of medium-K basaltic andesite pumice and scoria as coarse aggregates on structural lightweight concrete. The testing results indicated that these pumice and scoria had a typical characteristic so that they were completely different from those existed previously. Both typical vesicular rocks also fulfilled the requirements of coarse lightweight aggregate. The mix designs of structural lightweight concrete for the specified compressive strengths yielded Portland-Pozzolan Cement (PPC) contents were relatively lower than the previous studies conducted. The property of fresh concrete tests showed that for the specified slump values, the lightweight concrete mixtures can achieved satisfactory workabilities. While the properties of hardened concrete tests showed that almost all equilbrium densities fulfilled the requirements, but three equilibrium densities of scoria lightweight concrete were slightly greater than the requirements so that they were classified as structural semi-lightweight concretes. In addition, the use of typical pumice and scoria as coarse aggregates on that concrete yielded a significant density reduction, ie. approximately 20 %. The compressive strength obtained in the tests conducted can achieved those specified in the mix designs however two pumice structural lightweight concretes did not achieve them. The ultimate strains and modulus of elasticities also remained in proportional values, while the splitting tensile strengths and modulus of ruptures were relatively low when compared with previous studies.Keywords-pumice, scoria, medium-K basaltic andesite, structural lightweight concrete I. INTRODUCTION Studies on structural lightweight concrete using pumice and scoria as a replacement for artificial lightweight aggregate have been carried out in recent years. Artificial lightweight aggregate is a highly profitable manufactory product in lightweight concrete technology. Beside its well-controlled quality, the density reduction of lightweight concrete utilizing this synthetical aggregate can reach about 28 % [29], thereby it affects the structural design results and decreases its overall costs. However, its production process is complicated, requires high thermal energy [21][23] [29] and produces certainly air pollution thus the its product becomes expensive, less energy saving and less environmental friendly. Whereas, both volcanic lightweight aggregates above are abundant in nature so that they produce certain lightweight concretes that are cheaper, conserve energy and more environmental friendly. Furthermore, their applications as aggregate on lightweight concrete have been recommended by [1][6] and they can also be classified as structural lightweight concrete [2]. Unfortunately, their existences are only in certain regions, especially in volcanic regions with characteristics and qualities vary according to the location where both pyroclastic rocks are ejected. Pumice and scoria are glassy volcanic igneous rocks that have abundan...

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The coronavirus causing the Covid-19 pandemic has been experienced by us since 2020, which has led to an increase in the use of disposable medical masks in Indonesia and even worldwide. Polypropylene is a thermoplastic polymer used as the main ingredient in medical masks that takes more than 25 years to decompose in landfills. This research offers an innovative way to use medical mask waste in high-performance concrete. The resulting medical mask waste is subjected to a sterilization process and cut into fibers to analyze the effect of its addition on the compressive strength and splitting tensile strength of high-performance concrete. The research began with testing the physical and mechanical properties of the materials, designing a concrete mix using the absolute volume method, and taking samples for compression and splitting tests. The variation in the ratio of water-cement and pozzolanic materials w/(c+p) is 0.32. As a result, the compressive strength of concrete increased with a fiber size of 5×0.5 cm and 2×0.5 cm. An increase is up to 7 % with an optimum value of 72.37 MPa with a fiber size of 2×0.5 cm and a content of 0.15 %. However, there was a decrease in the compressive strength with a 5×1 cm mask fiber size. The overall split tensile strength value of all variations in waste fiber size and content increased with an optimum value of 7.29 MPa at 0.20 % fiber content with a fiber size of 5×0.5 cm. This indicates that polypropylene fibers from medical mask waste have a positive effect on high-performance concrete, namely improve the properties of concrete with a low tensile strength, which is expected to inhibit the propagation and reduce the size of cracks in reinforced concrete structures

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This study presented observations of the suitability of medium-K basaltic andesitic pumice and scoria as a coarse aggregate on structural lightweight concrete that was environmental friendly and energy saving. Testing results indicated that this typical pumice and scoria fulfilled the requirements as a coarse lightweight aggregate. The mix design of specified compressive strengths yielded a lower proportion of Portland Pozzolan Cement (PPC) than previous studies. Testing results of fresh concrete showed a satisfactory workability at determined slump values without segregation and excessive bleeding. Testing results of hardened concrete showed that the density reduction was about 20 %, but there was a density of scoria lightweight concrete that exceeded slightly the requirements. All compressive strengths complied with the requirement but there was a pumice lightweight concrete that did not reach the specified compressive strength. The modulus of elasticity and splitting tensile strength were relatively low compared to normalweight concrete as control, whereas drying shrinkage was lower than in previous studies.