Papers by Keyword: Aggregates

Abstract: This review utilizes bibliometric analysis to examine global research trends and the chronological development of studies on the incorporation of mine wastes and tailings in concrete. A total of 345 publications were extracted from the Web of Science (WOS) database, and their analysis revealed a clear upward trajectory in scientific output since 2000. Respectively, China, India, Canada, and the USA were identified as the countries contributing the most to this research area. Among the 1139 author keywords extracted from the collected papers, 103 keywords with a minimum of three occurrences were analyzed using the VOSviewer software. VOSviewer further supports identifying research gaps and emerging trends by visualizing relationships among authors, publications, and keywords, facilitating a deeper understanding of the dynamics within the field. The analysis of keyword occurrences shows convergence towards research that focuses on the development of sustainable and high-performance materials that equate environmental responsibility with industrial economy demands. The current review also uses Biblioshiny, a web-based tool that explores topic timelines. It reflects that, in recent years, research focuses have shifted toward more sustainability, advanced materials, and performance optimization in the use of mine tailings in concrete.

Abstract: Over the years, plastic production has increased in direct proportion to the amount of plastic waste generated globally. Single-use plastics such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and polypropylene (PP) have increased significantly. Therefore, they can be used as aggregates in the production of concrete to reduce the generation of plastic waste in the environment. LDPE, LLDPE and PP were the plastic types used, with 25% and 50% of plastic aggregate replacing sand. The tests included Fourier-transform infrared spectroscopy (FTIR) analysis of the plastic granulate, density, and compression tests of the concrete specimens. The type of granulate used follows the type of plastic tested from the results of the FTIR characterization. It was found that the compressive strength of concrete containing 25% of plastic aggregates was higher than that of concrete containing 50% of plastic aggregates. The compressive strength of the LLDPE concrete specimens is 31.4 MPa, whereas the compressive strength of the LDPE concrete specimens is only 26.3 MPa and that of the PP concrete specimens is 30.4 MPa. Further research will be carried out to determine the optimum strength of concrete with plastic aggregates.

Abstract: Nowadays the construction of palm oil industry mills is advancing rapidly and the next one is Refined Palm Oil (RPO). Refined Palm Oil (RPO) is one of the derivatives of palm oil processing. One option to use structures in the construction of palm oil mills is to use concrete. Plant parts that have concrete components often suffer damage, cracks and reduced concrete strength.This study is intended to examine the mechanical properties of concrete including compressive strength, flexural strength and porosity in concrete in the RPO environment, examining changes in the weight of coarse and fine aggregates immersed in RPO. This study used concrete experiments in RPO baths with 3 combinations, 54 samples and 2 types of concrete plan life, then analyzed in the laboratory. The parameters measured are changes in aggregate weight, porosity, bending strength and compressive strength of concrete. The results showed that the higher the percentage of RPO immersed in concrete, the lower the compressive strength, bending strength and porosity of the concrete. Fine aggregate undergoes weight change when immersed in RPO for 28 and 56 days, while coarse aggregate undergoes no weight change

Abstract: Due to the seismicity of the country and especially to the geology of the province of Pichincha, it was considered important to obtain this equation in order to improve the structural design of future constructions since we do not have our own parameters to determine the mechanical properties of concrete. Based on previous investigations of the modulus of elasticity carried out in the country, it was identified that the current formula does not reflect the reality of the existing conditions since the derivation of this equation was determined in the USA whose characteristics of the materials are totally different from those of Ecuador. Therefore, it was considered convenient to carry out a complete study of the properties of the aggregates to obtain the equation of the modulus of elasticity of concrete that represents the attributes of the province of Pichincha.

Abstract: Concrete members are reinforced by steel fibers to overcome their brittle nature. This paper is focused on the effect of percentage of fiber and the maximum aggregate size on mechanical properties of concrete samples such as compressive and tensile strengths, and ductility. The mean values of these quantities show that by increasing the reinforcement content to 0.66% and the size to 12.5 mm, there is a dramatic improvement on properties of samples. Also, they demonstrate that the size of coarse aggregate has more effect on improvement of the quantities in comparison to steel fiber content and changing the size and fiber content has more effects on ductility than mechanical properties. Statistical approach which considers standard deviations of experimental data, confirms that the gravel regardless of fiber content, leads to the highest improvement on properties with size of 12.5 mm. But the results show for volumetric steel fiber without considering aggregate size, is 0.33%. This clearly indicates the effect of data scattering on mean values of mechanical properties and ductility.

Abstract: The paper studies the influence of aggregates and fillers with negative and positive electrical surface properties on the corrosion resistance of concrete. The advantage of resistance of fine-grained concrete on marble sand in comparison with concrete on quartz sand, regardless of the type of aggressive environment, is established. At the same time, the stability of samples of powdered concrete with 10 and 30% of fine-grained filler changed little when replacing the quartz powder with marble one. It is shown that the resistance coefficients of powdered concrete samples with quartz filler (10%) do not differ from the resistance coefficients of samples of a similar composition with crushed marble filler, and with an increase in the dosage of the filler (30 %) slightly exceed. It was found that in powder concretes without aggregates, the contact layer between the cement matrix and the aggregate is absent, so the composition of the mineral powder plays a much smaller role in the corrosion processes of cement stone. The obtained results allowed establishing that electrokinetic phenomena play a secondary role, and the main influence on the stability of fine-grained concrete is the processes of pore colmation by chemical reactions, as well as the interaction of the surface layers of the aggregate with the cement matrix.

Abstract: Heat-resistant concretes have been successfully used in many heat units and building structures. Making concrete heat-resistant is possible through the development of a heat-resistant phosphate matrix, aluminophosphate binder. The compositions of high-refractory concretes on aluminophosphate binder with electrocorundum and chrome-aluminous slag have relatively high strength up to 70 MPa after heat treatment. Wastes generated as a result of technological activities of enterprises have several technical and economic advantages as industrial raw materials. After passing the production possibility frontier, the material not only has not lost its properties, but became more prepared with the position of the grain composition and growth of specific surface area, heat treatment for use in the technology of concrete and refractory concrete, in particular, as heat-resistant fillers. The methodological approach in the study of defective ceramic-bond abrasive wheels has been proposed herein. The chemical, grain and mineralogical analyses of the material after mechanical grinding allowed us to define it as an aggregate for concrete in order to give it heat-resistant properties. The obtained concrete composition has a tensile strength 2.5 times higher than conventional cement composition of concrete and thermal resistance (water, 800°C) of the composition with heat-resistant filler has increased in 5 times.

Abstract: Fly ash as a pozzolanic waste material can be utilized to substitute part of Portland cement in concrete mixture. The concrete paving industry utilizes the fly ash up to 50% (by weight) of the total binder. This study aims to obtain the characteristics of fly ash applications for pervious concrete. The composition of the binder developed based on the optimal proportion of fly ash from the previous study and the maximum of fly ash percentage used by the local paving industry in general. Other mix variations were made of the same binder composition with the addition of 6% of fine aggregates. The compressive strength of pervious concrete which binder composed of 63% portland cemet composite-25% fly ash-12% silica fume gained at 28 days, was not much different from the compressive strength of the pervious concrete without fine aggregate and with the binder composition of 50% FA-50% PCC and 0% SF. The value of the compressive strength test of the pervious concrete without fine aggregate is still within the range of compressive strength values ​​according to the ACI 522 R-10. The permeability rate of the pervious concrete is in the range of permeability research result of Chopra, 2013 (0.97 ÷ 1.90 cm/sec), but still higher compared to permeability rate gained by Dewoolkar, 2009 (0.83 ÷ 0.98 cm/sec).

Abstract: The paper researches lightweight mortars based on a high content of alternative materials. 25 – 30% heating plant slag was used in order to modify the matrix. Fly ash agloporite (a lightweight aggregate produced by self-combustion from fly ash) was used as an aggregate. Mortars were exposed to the temperatures up to 1,250° C. Two types of cooling were carried out at 1,000° C; controlled slow (in the furnace) and by shock (in water baths of approximate 18° C). Developed materials were further analyzed by various methods: monitoring changes in an observation furnace, physical–mechanical (to determine strength properties), physical-chemical (phase composition - XRD) and microstructural (SEM).

Abstract: The phase change energy storage aggregate was prepared with the eutectic mixture of capric acid (CA) and stearic acid (SA) as phase change energy storage material (PCM) and waste autoclaved aerated concrete as skeleton. The results showed that the appropriate mass ratio of CA to SA is 9:1, with melting temperature 26.8°Cand latent heat of 96.4 J/g. The optimal load of PCM on waste autoclaved aerated concrete was 55%. In order to reduce leakage and increase strength of the aggregate, slag-water glass-gypsum binder was used for encapsulation, which also helped increase the compatibility with the main building materials. The simulation test showed that the phase change energy storage aggregate possesses good temperature control and energy storage performance.