We can observe the growing tendency of usage of recycled concrete aggregate (RCA). Changes in waste materials management rules will result in necessity of more common reutilization of materials from demolished concrete structures. Thus new fields of RCA application and new ways of its utilization in concrete manufacturing are still being looked for. Research presented in the paper has been conducted to examine two methods of improving poor gradation of natural aggregate (NA) using RCA. The NA that did not fulfill requirements of gradation had been chosen. It consisted of ca. 75% of 2-4 mm fraction. In the first method a part of NA was replaced with 2-16 fraction of RCA of low quality. In the second method also a part of NA was replaced this time with 4-8 mm and 8-16 mm fractions of good quality RCA. The amount of replacing fractions was precisely calculated in order to fit optimal gradation curve. Quality of the gradation was measured with so called gradation index. Mechanical properties of researched concretes was tested as well as some of their properties related to durability. It can be stated, on the basis of the results, that both methods improve most of the vital concrete properties.
In the article the possibility of utilization of two waste materials: Recycled Concrete Aggregate (RCA) fraction 0-2 mm and Class C fly ash (from lignite burning power plant) in Controlled Low-Strength Material (CLSM) was presented. The research covered twelve different mixtures. The mixtures differed in cement and fly ash content as well as content of the fine aggregate. As a fine aggregate 0-2 mm fraction of RCA or river sand were used. The results showed that use the fine fraction RCA instead of sand does not cause technological problems and allows, depending on the needs, obtaining the material with different properties and a wide range of applications.
Currently, waste generation is a huge problem all over the world. The largest source of generated waste is plastics from plastic packaging made of polyethylene and polypropylene, including PET bottles. Modern ecology aims to reduce the carbon footprint by recycling plastics or by producing biodegradable plastics that are completely broken down by microorganisms into simple particles that occur naturally in nature. Polyethylene terephthalate (PET) has good mechanical properties but is resistant to microorganisms. As a result, it cannot be classified as a biodegradable plastic, but when it is reused for the production of utility products, it becomes a bioplastic. A good way to dispose of PET is to use it for the production of utility products, in which its good mechanical properties can be used. Concrete is a basic material, the consumption of which in the construction industry is enormous. One of the negative features of concrete is its low tensile strength, which can be improved with continuous or dispersed reinforcement. This paper presents the results of compressive and tensile-bending tests of concrete reinforced with dispersed “fibres” of a different length and width, which were produced by a prototype device from PET beverage bottles. The prototype device enables repeatable fibres with a width of 2 mm, and lengths of 38 mm, 62 mm, and 93 mm to be obtained. The highest flexural tensile strength of the concrete was achieved in the case of the PET fibres with a length of 62 mm. It turned out that concrete with such reinforcement has a higher bending tensile strength by 15 % in relation to the tensile bending strength of the concrete without the dispersed reinforcement. The PET fibres also improve compressive strength. PET fibres, in order not to deteriorate in the alkaline environment of concrete, must be secured with an appropriate chemical agent. The effect of concrete reinforcement with the recycled PET fibres was compared to the effect of dispersed reinforcement made of polypropylene and steel fibres. The highest bending tensile strength was obtained in the case of the concretes with the scattered PET reinforcement. However, the differences in the bending tensile strength of concrete are not big and are equal to 0.64 MPa for polypropylene fibres and only 0.09 MPa for steel fibres.
During compaction of a concrete mix, when thin slabs are formed in a horizontal position, the components of this mix become segregated. Heavy components fall to the bottom, and light components (air and water) move to the top. This process may suggest that the upper layers of concrete elements formed in a horizontal position may have lower compressive strength than the remaining part of the element. This problem is recognized and documented in many publications, but there was a publication whose test results indicate a lack of variability in the compressive strength of concrete across the thickness of tested elements. The discrepancies appearing in the evaluation of concrete homogeneity was the reason for conducting destructive tests of the compressive strength of concrete across the thickness of horizontally concreted test elements that imitate thin slabs. The obtained results of the destructive compressive strength confirmed previous results regarding the heterogeneity of concrete. They clearly indicate that there is a differentiation of the compressive strength of concrete across the thickness of a thin element, which remained in a liquefied state for a certain time during its formation. The longer the duration of this state across the entire thickness of the formed element, the greater the differentiation of the compressive strength between the top and bottom layers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.