scholarly journals Strength Property Study on Paver Block Made with Recycled Concrete Aggregates – An Experimental Review

2019 ◽  
pp. 480-485
Author(s):  
Gifty E ◽  
Harini Devi N ◽  
Meena P ◽  
Gunasekar S
Keyword(s):  
Natural Resources ◽  
Strength Property ◽  
Large Volume ◽  
Raw Materials ◽  
Recycled Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Save Energy

With increase in population and urbanization, demand of raw materials such as cement and aggregate has increased in the construction industries. Further it has been recognized that waste from construction &demolition sectors are of large volume and this volume is increasing every year. Utilization of demolished waste offers not only the solution of disposal problems but also helps to conserve natural resources for meeting increased demand of aggregates and save energy. This study deals with the fabrication of concrete paver blocks using construction and demolition (C&D) waste as a replacement of natural aggregates.

scholarly journals Evaluation of the Ecotoxicological Potential of Fly Ash and Recycled Concrete Aggregates Use in Concrete

2020 ◽  
Vol 10 (1) ◽  
pp. 351 ◽  
Author(s):  
Patrícia Rodrigues ◽  
José D. Silvestre ◽  
Inês Flores-Colen ◽  
Cristina A. Viegas ◽  
Hawreen H. Ahmed ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Daphnia Magna ◽  
Raw Materials ◽  
Construction Materials ◽  
Recycled Concrete ◽  
Experimental Program ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates

This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from concrete mixes produced with a replacement ratio of Portland cement with 60% of FA and 100% of natural aggregates and produced with 60% of FA and 100% of RA were classified as clearly ecotoxic mainly towards Daphnia magna mobility. Therefore, raw materials with weak evidences of ecotoxicity could lead to the production of concrete products with high ecotoxicological potential. Overall, the results obtained highlight the importance of integrating data from the chemical and ecotoxicological characterization of materials’ eluate samples aiming to assess the possible environmental risk of the construction materials, namely of incorporating non-conventional raw materials in concrete, and contributing to achieve construction sustainability.

Review of Studies concerning Effects of Unbound Crushed Concrete Bases on PCC Pavement Drainage

1996 ◽  
Vol 1519 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Mark B. Snyder ◽  
James E. Bruinsma
Keyword(s):  
Drainage System ◽  
Field Studies ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Drainage Systems ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Crushed Concrete ◽  
Pavement Structures ◽  
Natural Aggregates

Recycled concrete aggregate (RCA) products are sometimes used as replacements for virgin aggregate products in concrete pavement structures. Recent concerns have centered on the deposit of RCA-associated fines and precipitate suspected of reducing the drainage capacity of RCA base layers and associated drainage systems. Environmental concerns have focused on the relatively high pH of the effluent produced by untreated RCA base layers. Several studies have examined these concerns and others; the results of some of these studies have not been published or publicized. The most relevant of these studies are summarized herein. These research efforts demonstrate that calcium-based compounds are present in most recycled concrete aggregates in quantities sufficient to be leached and precipitated in the presence of carbon dioxide. Precipitate potential appears to be related to the amount of freshly exposed cement paste surface. Thus, selective grading or blending with natural aggregates can reduce, but not eliminate, precipitate problems. It was also noted that insoluble, noncarbonate residue makes up a major portion of the materials found in and around pavement drainage systems. Washing the RCA products before using them in foundation layers appears to reduce the potential for accumulation of dust and other fines in the drainage system, but probably has little effect on precipitate potential. Field studies have shown that precipitate and insoluble materials can significantly reduce the permittivity of typical drainage fabrics but that attention to drainage design details can minimize the effects of these materials on pavement drainage.

scholarly journals Modulus and Strength of Concretes with Alternative Materials

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4378
Author(s):  
Ana Elisabete Paganelli Guimarães de Avila Jacintho ◽  
Ivanny Soares Gomes Cavaliere ◽  
Lia Lorena Pimentel ◽  
Nádia Cazarim Silva Forti
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Model Code ◽  
Alternative Materials ◽  
Model Code 2010 ◽  
The Difference ◽  
Natural Aggregates ◽  
Predicted Values

This paper presents a study with concretes produced with natural aggregates, recycled concrete aggregates (RCA) and waste porcelain aggregates (WPA). The study analyzed the influence of recycled aggregates in the mechanical properties of conventional concretes and evaluated the difference between measured and predicted values of elasticity modulus. The incorporation of WPA in concrete showed better mechanical results compared to the concretes produced with RCA. Measured elasticity moduli were lower than moduli predicted by NBR 6118:2014 and fib Model Code 2010, while measured results were greater than values predicted by Eurocode 2:2004 and ACI 318:2014, as expected, which indicated the safety of the latter two standards.

Quality Evaluation System for Description of Recycled Concrete Aggregates and Verification of its Functionality

2017 ◽  
Vol 902 ◽  
pp. 14-19 ◽  
Author(s):  
Iveta Nováková ◽  
Iveta Hájková
Keyword(s):  
Evaluation System ◽  
Quality Evaluation ◽  
Recycled Concrete ◽  
Demolition Waste ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Concrete Mixtures ◽  
Natural Aggregates ◽  
Set Up ◽  
Quality Evaluation System

Article presents quality evaluation system for description of recycled concrete aggregates (RCA), verification of RCA properties and subsequent application in to concrete mixtures as a partial or total replacement of natural aggregates (NA). Modernization and rehabilitation of constructions is accompanied by creation of demolition waste from old buildings and structures. The necessity of recycling is unavoidable, because volume of construction and demolition waste (C&DW) is increasing and the landfills are reaching their maximum capacity. Nowadays, there are numerous research teams focused on analysis of characteristics and application of RCA into new concrete as a replacement of NA. Test samples of RCA have always different source, grain composition and other physical and mechanical properties, which are variously described in each different paper. Up to now, there is no any uniform quality evaluation system for description of recycled concrete aggregates, which can easily describe their source and assumed properties. Our aim is to set up rules for description of RCA and simplify the evaluation of properties of various RCA. Qualification system will be applied on three different samples of RCA and verified by the selected properties tests. Tested samples of RCA will be than used as a replacement of natural aggregates in concrete mixtures. The replacement amount was set up on 20%, 40% and 100% according to the reviewed literature, to have a comparable replacement amount and valuable results for discussion. The results of RCA testing and testing of concrete with partial and total replacement of NA showed that the evaluation system is working properly. It can be concluded, that accuracy of the quality evaluation system for description of recycled concrete aggregates is sufficient, but more tests on RCA should be done to prove all connections in between description of RCA and their properties.

scholarly journals Removal of Phosphorus from Synthetic Wastewater Using Recycled Concrete Aggregates as a Filter Medium

2018 ◽  
Vol 9 (1) ◽  
pp. 13-26 ◽  
Author(s):  
S. H. Adnan ◽  
R. Hamdan ◽  
N. A. Roni
Keyword(s):  
Natural Resources ◽  
Phosphorus Removal ◽  
Recycled Concrete ◽  
Filter Medium ◽  
Alternative Methods ◽  
Synthetic Wastewater ◽  
Initial Concentration ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Alternative Method

These days, sustainability has become a primary concern as the large amount of natural resources are being used to produce materials such as concrete. Concrete from the construction industry constitutes the major proportion of construction waste. This could bring negative impact including depletion of natural resources, pollution, increasing landfill space, and high cost of waste disposal. All of these negative impacts are the sustainability issues that should be concentrated on. Hence, alternative methods have been introduced in order to reduce waste by recycling concrete waste. One of the alternative methods that can be used is by reusing recycled concrete aggregates (RCA) from discarded waste cubes. RCA can be used to produce new concrete but it will generally have a lower performance compared to normal concrete. Thus, the present study introduces an alternative method which is by reusing the RCA as a water filter medium to remove phosphorus from wastewater. Phosphorus is one of the inorganic compounds found in wastewater that can lead to environmental problems such as eutrophication. Based on previous studies, many types of materials with various chemical compositions have been used for phosphorus removal from wastewater. Therefore, this study demonstrates the ability of RCA as an alternative method for phosphorus removal from wastewater. In addition, three different factors have been considered in the removal of phosphorus namely, different initial concentration of phosphorus, different sizes of RCA and dosage of RCA used during the treatment process. Based on the experiments conducted, the lowest initial concentration of phosphorus of 10 mg/L, the smallest RCA size ranging between 0mm to 5mm and the highest RCA dosage of 50g resulted in the highest percentage of phosphorus removal in wastewater.

scholarly journals Evaluation of Eco-Efficient Concretes Produced with Fly Ash and Uncarbonated Recycled Aggregates

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7499
Author(s):  
Miren Etxeberria
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Conventional Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Carbonation Resistance ◽  
Chloride Resistance ◽  
Natural Aggregates

The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement ratio of 0.50 (Series 1) and 0.40 (Series 2). In both series, concretes were produced using 0% and 50% of RCA with 0%, 25% and 50% FA. After analysing the compressive strength, and carbonation and chloride resistance of those concretes, their eco-efficiency based on the binder intensity and CO2-eq intensity was assessed. We found that the use of 50% uncarbonated RCA improved the properties of concretes produced with FA with respect to using natural aggregates. The concrete made of 25% FA plus RCA was considered the most eco-efficient based on the tests of compressive, carbonation and chloride properties with the values of 4.1 kg CO2 m−3 MPa−1, 76.3 kg CO2 m−3 mm−1 year0.5 and 0.079 kg CO2 m−3 C−1, respectively. The uncarbonated RCA improved carbonation resistance, and FA improved chloride resistance. It can be concluded that the use of 50% un-carbonated RCA combined with FA considerably enhanced the properties of hardened concrete and their eco-efficiency with respect to concretes produced with natural aggregates.

scholarly journals Natural aggregate totally replacement by mechanically treated concrete waste

2015 ◽  
Vol 10 (1) ◽  
pp. 83-90
Author(s):  
Jozef Junak ◽  
Nadezda Stevulova
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Reference Sample ◽  
Average Density ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Recycled Material

Abstract This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

scholarly journals Design Strategy for Recycled Aggregate Concrete: A Review of Status and Future Perspectives

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 695
Author(s):  
Natt Makul ◽  
Roman Fediuk ◽  
Mugahed Amran ◽  
Abdullah M. Zeyad ◽  
Sergey Klyuev ◽  
...  
Keyword(s):  
Environmental Impact ◽  
Natural Resources ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Demolition Waste ◽  
Construction Waste ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregate

Currently, a number of disadvantages hampers the use of recycled concrete aggregates (RCA). The current review proves that concretes made with complete replacement of natural aggregate with RCA allow the production of high-quality concrete. One of the possibilities for improving concrete properties with RCA is the use of extended curing and pozzolanic materials with varying cement ratios. The potential use of RCA concretes is in the production of high-value materials that increase environmental and financial benefits. RCA have strong potential in the development of a new generation of concrete and stimulate economic activity in many countries in addition to optimizing natural resources. Economic benefits include minimal travel costs; cheaper sources of concrete than newly mined aggregates; reduction of the landfill area required for the placement of concrete waste; the use of RCA minimizes the need for gravel extraction, etc. The proposed strategy could be to sequentially separate demolition waste such as roof finishes, waterproof materials, interior and exterior materials, etc. Closing life cycles is the main approach used for efficient structures for the recycling and reuse of construction and demolition waste in the production and recovery of materials, especially when recycling and reusing materials. In the life cycle, the recycling of recovered materials allows them to be used for new construction purposes, avoiding the use of natural concrete aggregates. Government, design institutes, construction departments and project managers should be involved in the creation and use of RCA. In demolition and construction, the main players are the project owners. Their obligations, expectations and responsibilities must be properly aligned. For the past 20 years, recycled concrete aggregate from demolition and construction waste has been considered as an alternative to pure concrete in structural concrete to minimize the environmental impact of construction waste and demolition waste and the conversion of natural aggregate resources. It is now recognized that the use of RCA for the generations of concrete is a promising and very attractive technology for reducing the environmental impact of the construction sector and conserving natural resources. In the market, the selling price is not an obstacle for market applications of RCA, as there are scenarios in which their cost is lower than the cost of products made from conventional building materials. This is more of an acceptance factor in the market for recycled concrete aggregates. In this sector, the lack of identification, accreditation and uniform quality certification systems and their narrow application cause some marketing problems. With proper RCA preparation, concrete with standard physical and mechanical properties and performance characteristics can be obtained.

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