Articoli di riviste: "Recycled concrete fines"

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Naruts, Vitali, Oksana Larsen e Anton Bakhrakh. "SCC with activated recycled concrete fines". MATEC Web of Conferences 239 (2018): 01024. http://dx.doi.org/10.1051/matecconf/201823901024.

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The main application of concrete waste is its use as a coarse aggregate in concretes. Recycled concrete fines can be also used in concrete mixtures as fine aggregates or fillers. The paper describes an efficient activation method of recycled concrete fines to obtain technological, economical and ecological benefits. The idea is to combine mechanical and chemical methods of activation. According to various experiments the addition of superplasticizer into the mill speeds up grinding process. The present investigation shows that adding 0.5% by mass of recycled concrete fines allows obtaining higher specific area at the same processing time. Use of the prepared filler in SCC increases compressive strength more than 10% in compare with SCC containing limestone powder and mechanically activated recycled concrete fines.

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Iduwin, Tommy, Dicki Dian Purnama, Pratiwi Septyaning Putri e Hastanto Siswo Martono. "Pengaruh Penggunaan Material Daur Ulang Terhadap Sifat Mekanik Beton Non Pasir". FORUM MEKANIKA 9, n. 1 (31 maggio 2020): 11–19. http://dx.doi.org/10.33322/forummekanika.v9i1.1080.

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Infrastructure development is increasing every year making the need for concrete materials increases. Using alternative materials can reduce the scarcity of material and environmental damage caused by taking and dredging the material. This research is to find out how much influence the recycled material has on the compressive strength of no fines concrete. The variations used are recycled materials of 0%, 25%, 50%, 75% and 100%. Mechanical testing conducted is a compressive strength test to determine the compressive strength of no fines concrete at the age of 7, 14 and 28 days. The ratio of cement and aggregate used is 1: 4 with FAS 0.5. This research uses 15 x 30 cm cylindrical molds with 45 test specimens. The test results show the highest compressive strength value of non-sand concrete occurs at 0% recycled material by 10.47 Mpa and the lowest compressive strength on non-sand concrete 100% recycled material is 8.39 Mpa. The percentage of absorption of no fines concrete shows that the more recycled material is used, the smaller the value of water absorption. The highest absorption value in no fines concrete is 0% recycled material, which is 5.93% and the smallest value is in the variation of no fines concrete 100% recycled material recycled material that is equal to 4.99%.

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Soultana, Athanasia, Michael Galetakis, Anthoula Vasiliou, Konstantinos Komnitsas e Despina Vamvuka. "Utilization of Upgraded Recycled Concrete Aggregates and Recycled Concrete Fines in Cement Mortars". Recent Progress in Materials 03, n. 03 (11 febbraio 2021): 1. http://dx.doi.org/10.21926/rpm.2103035.

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Waste concrete is the most predominant constituent material among construction and demolition waste. Current waste concrete recycling is limited to the use of recycled concrete aggregates as a road-base material and less as aggregates in new concrete mixes. Further, the production of recycled concrete aggregates results in the generation of a high amount of fines, consisting mainly of cement paste particles. Hence, this study aims to produce the cement mortars using the upgraded recycled concrete aggregates (sand granulometry) for the total replacement of natural aggregates and recycled concrete fines activated through a thermal treatment method as a partial cement substitution material. Cement mortar specimens were tested for their compressive and flexural strength, density and water absorption performance. The results showed that the combined usage of upgraded recycled concrete sand for total replacement of primary crushed sand and recycled concrete fines as partial cement replacement material is a promising option to produce cement mortars.

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Dahri, S. A., B. A. Memon, M. Oad, R. Bhanbhro e I. A. Rahu. "Quality of Recycled Aggregates and Compressive Strength of No-Fines Recycled-Aggregate Concrete". Engineering, Technology & Applied Science Research 11, n. 5 (12 ottobre 2021): 7641–46. http://dx.doi.org/10.48084/etasr.4349.

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This research paper presents the laboratory investigations of the compressive strength of no-fines concrete made with demolished waste as coarse aggregates used in percentages from 20% to 100%. The basic properties of aggregates were determined. Sieve analysis of both conventional and recycled aggregates was conducted to ensure the existence of well-graded aggregates in concrete. Nine concrete mixes were designed with an aggregate-cement ratio of 4. Additionally, three batches were prepared (conventional, recycled, conventional no-fines concrete) and the results were compared. For all mixes, the water-cement ratio was equal to 0.5. In each batch, 5 cylinders of standard size (total 60 samples) were prepared and cured for 28 days. The weight of the specimens was determined and compressive strength was checked in a Universal Testing Machine under gradually increasing load. A decrease in weight and compressive strength was recorded for the batches of the proposed concrete. Results show that at 40% replacement level the loss of compressive strength is 19% and the weight reduction of the samples was equal to 9%.

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Bounouni, Sofiane, e Tounsia Boudina. "Durability characteristics of recycled high performance concretes under an aggressive environment (sea water)". Technium Social Sciences Journal 40 (8 febbraio 2023): 578–91. http://dx.doi.org/10.47577/tssj.v40i1.8417.

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With the increase of solid construction waste (CSW) due to the acceleration of urbanization in Algeria, many ecological and environmental issues have been raised. Recycling and reuse of construction waste helps to reduce pollution, carbon emissions and preserve resources. Few studies have focused on the durability characteristics of concretes based on fine aggregates recycled from brick and concrete waste. The main purpose of this study is to formulate and analyze the performance of HPC based on waste brick and concrete fines. The substitution of alluvial sand with brick fines, causes the reduction of the heat of hydration and delays the appearance of the thermal flux peaks. while HPC rich in crushed concrete waste increases the heat of hydration. The appearance of heat flux peaks coincides for all mixtures with fines of waste concrete substitution and they will be delayed and prolonged for HPC with sand based on waste brick.

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Stuerwald, Simone, Ronny Meglin, Susanne Kytzia e Sabrina Gilg. "Use of recycled concrete fines in cement and as aggregate". Acta Polytechnica CTU Proceedings 33 (3 marzo 2022): 591–96. http://dx.doi.org/10.14311/app.2022.33.0591.

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The research project focused on investigating and optimizing the processing and use of recycled crushed sand 0/4 from concrete demolition waste, as an alternative raw material in the cement and concrete industry. Crushed sand is produced during the processing of concrete demolition waste. The goal was to identify the optimum way of using the processed material along the entire process chain so that greenhouse gas emissions, waste volumes are reduced, and natural resources are conserved. Different samples of laboratory and real crushed concrete fines were collected and examined in relation to various possible applications in accordance with the applicable standards. Results highlight, that crushed concrete fines can be used in various applications in the concrete value-chain. However, for an optimal usage, additional processing is needed.

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Mustafy, Tanvir, Md Maruf Hasan, Nayeem Ahmed Shuvo e Joarder Md Sarwar Mujib. "Characterization of Mechanical Properties of Concrete Recycled Ceramic and Glass Powder Exposed to Elevated Temperatures". MIST INTERNATIONAL JOURNAL OF SCIENCE AND TECHNOLOGY 10 (26 giugno 2022): 01–14. http://dx.doi.org/10.47981/j.mijst.10(01)2022.350(01-14).

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Systematic reuse of industrial debris is a crucial component that helps shape the sustainable construction system and green technology. The effective optimization of waste ceramic and glass fines into concrete mixes, as partial replacements of natural sand by volume, has been used in this study to explore the mechanical properties of ceramic recycled aggregate (CRA) and glass recycled aggregate (GRA) concrete at higher temperatures. The study comprises 17 types of concrete mixtures comprised of normal concrete (NC) along with 8 different mixes from both GRA and CRA concrete. In both types of GRA and CRA concrete, the sand replacement (by volume) ratios are similar. This paper highlights NC along with the volumetric replacements of sand as 5%, 10%, 15%, 20%, 25%, 30%, 35%, and 40% in other mixes. A total of 306 cylinders were made whereas 18 cylinders for NC and each group (GRA and CRA) included n=18 cylinders. Selected temperatures were 25°C, 100°C, 200°C, 400°C, 600°C, and 800°C to determine the overall mechanical and chemical alterations in NC and recycled concrete. The study reveals that increasing the addition of recycled glass and ceramic fines improves the overall compressive strength, and tensile strength compared to normal concrete. Higher replacement of ceramic and glass fines reduces the cracks and enhances the durability of concrete. In addition, more strength reduction was noticed in NC with increasing temperatures, while the reduction rate was slower in both GRA and CRA concrete. Furthermore, the study expounds that, by exploiting the ceramic and glass wastes (as fines) into concrete would result in two-way environmental advantages. One is, it would reduce the hazardous ceramic and glass landfills while the other is, it would minimize the frequency of sand mining.

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Sharaky, Ibrahim A., Ahmed S. Elamary e Yasir M. Alharthi. "Effect of Waste Basalt Fines and Recycled Concrete Components on Mechanical, Water Absorption, and Microstructure Characteristics of Concrete". Materials 15, n. 13 (21 giugno 2022): 4385. http://dx.doi.org/10.3390/ma15134385.

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In this paper, the recycled fine aggregates and powders produced from crushing old basaltic concrete and natural basalt were used to produce new concrete. The sand was partially replaced by two types of recycled wastes at five percentages: 0%, 20%, 40%, 60%, and 80%. The cement was partially replaced by recycled powders and silica fume (SF) at four percentages: 0, 5%, 10%, and 20%. The concrete strengths and water absorption were obtained at several curing ages. The obtained results emphasized the positive effects of increasing the curing time on enhancing the concrete properties, regardless of the types or the waste sources. Moreover, the recycled powders retarded the hydration reaction. In addition, the recycled fine aggregates and powders could achieve about 99.5% and 99.3% of the ordinary concrete strength and enhance the tensile strength. Furthermore, the mix containing 40% of recycled fine concrete aggregate diffused the highest contents of both calcium and silicate, which led to enhancing the interfacial transition zone (ITZ) and concrete properties, compared to the other tested mixes. Finally, the water absorption of all tested concrete mixes decreased with an increase in the curing age, while the mixes integrating 10% and 20% of SF experienced the lowest values of water absorption.

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Rahu, Ahsan Ali, Bashir Ahmed Memon, Mahboob Oad, Shakeel Ahmed Dahri, Abdul Raqeeb Memon e Amjad Hussain Bhutto. "Assessment of the Flexural Strength of No-Fines Recycled Aggregate Concrete Prisms". Engineering, Technology & Applied Science Research 13, n. 1 (5 febbraio 2023): 10067–72. http://dx.doi.org/10.48084/etasr.5458.

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This study investigated experimentally the flexural strength of no-fines recycled aggregate concrete, produced using 20-70% replacement of conventional coarse aggregates with coarse aggregates from demolished waste. Six prisms in each dosage with a 1:4 mix and 0.5 water-binder ratios were prepared. A batch of prisms with conventional aggregates was also cast to compare them with the proposed concrete. An equal number of samples were cured for 7 and 28 days and tested under a gradually increasing central point load to examine failure load, central deflection, and flexural strength. The comparison of results showed an increasing trend in deflection with an increase in the dosage of recycled aggregates. The 7-day cured samples had approximately 2.6 times the deflection of conventional concrete. However, the deflection at all replacement levels remained less than that allowed by ACI-318. The results showed a decreasing trend in flexural strength with an increase in the dosage of recycled aggregates. The 40% replacement sample had a less than 20% strength reduction and is recommended as the optimum level of replacement of conventional aggregates for the production of no-fines recycled aggregate concrete.

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Zhang, Jiake, Liupeng Zhang, Boyang Xu e Jie Yuan. "Influences of Carbonated Recycled Concrete Fines on Cement Hydration". Buildings 13, n. 4 (31 marzo 2023): 926. http://dx.doi.org/10.3390/buildings13040926.

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The preparation of recycled concrete aggregate generates a lot of fines, which are obstacles for implementing the recycled concrete aggregate. In this work, carbonation treatment is applied to improve the properties of recycled concrete fine, and the influences of carbonated recycled concrete fine (CRCF) on cement hydration process are evaluated. Both fresh and hardened properties of the cement paste samples replacing 0 to 30% of the CRCF are measured. The results reveal that the addition of CRCF obviously accelerates the hydration process of cement, especially during the early stage, and the initial and final setting times of the cement paste containing 30% CRCF are both reduced by approximately 25% compared to the control. The CRCF improves the strength gain of cement, and that influence becomes obvious with longer curing; the relative compressive strength of cement paste containing 30% CRCF is increased by 18% relative to the control after being cured for 28 days. At the same time, the early hydration of cement paste is accelerated with the addition of CRCF and the total hydration heat after 48 h of cement paste is significantly decreased with the addition of CRCF. Specifically, the total hydration heat after 48 h of cement paste with 30% CRCF is less than 50% of that with 0% CRCF. Besides that, CRCF consumes CH in cement paste and improves the pore structure of hardened cement paste. The morphology of hydrated samples shows that the shape of ettringite formed within the control sample with 0% CRCF is longer than those of the other ones formed in cement paste with CRCF, and the length decreases as the CRCF contents increase. In addition, the sample containing 30% CRCF does not show the particles, which means that CRCF reduces the ettringite forming in hardened paste samples. Thus, the findings from this work provide a better understanding of the field of waste concrete reuse.

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Kim, Jinyoung, BooHyun Nam, Zachary Behring e Baig Al Muhit. "Evaluation of Recementation Reactivity of Recycled Concrete Aggregate Fines". Transportation Research Record: Journal of the Transportation Research Board 2401, n. 1 (gennaio 2014): 44–51. http://dx.doi.org/10.3141/2401-05.

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Liu, Fu Ming, e Duan Yi Wang. "Influence of Material Properties on Hydraulic Conductivity and Strength of Aggregates Used for Pavement Base". Advanced Materials Research 446-449 (gennaio 2012): 2641–45. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2641.

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The hydraulic conductivity and strength of several aggregates (limestone, gravel and recycled concrete) are very important for pavement base construction. To study the influence of fines content on hydraulic conductivity and strength, constant/falling head permeability and CBR tests were performed. The results show that hydraulic conductivity exponentially decreases as fines content increases. Their values were also found to vary significantly as a function of aggregate type, gradation, and density. Particle degradation of recycled concrete aggregates is higher than crushed limestone and gravel, which leads to lower hydraulic conductivity values.

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Fawzi, Ruaa Q., e Hadeel K. Awad. "The Influence of Polypropylene Fiber and Silica Fume on the Mechanical Properties of No-Fine Concrete with Recycled Aggregate". E3S Web of Conferences 427 (2023): 02002. http://dx.doi.org/10.1051/e3sconf/202342702002.

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No-Fines Concrete is a type of concrete produced without fine aggregate or sand. Because of its high porosity, it allows rainwater to seep into the ground, directly replenishing the groundwater aquifer. With a design load of three tons, no-fine concrete can be utilized as pavement for rural roads. Additionally, this type of concrete can be utilized as a sub-base material in both flexible and rigid pavements. Aside from No-Fines Concrete's permeability properties, asphalt overlays are another option. This research studied the impact of silica fume and polypropylene fiber on the properties of no-fine concrete with recycled aggregate. The ratios of cement to aggregate and water to cement were 1:4 and 0.3, respectively. The recycled aggregate was demolished reactive powder concrete used in percentages of 10, 20, and 30% as a substitution for coarse aggregate by volume. The recycled aggregate percentage of 10% was the optimal percentage as it showed the least adverse effect on the no-fine concrete mixes. The polypropylene fiber was then added to the no-fine concrete mixes with 10% recycled aggregate in the percentages of 0.5, 1, and 1.5% by volume. The optimum percentage of polypropylene fiber was 0.5%, which improved the mechanical properties of no-fine concrete. Silica fume was used as a partial substitution for cement at a percentage of 10% and added to no-fine concrete mix with 10% recycled aggregate. The results show that using 10% silica fume and 0.5% polypropylene fiber with 10% recycled aggregate increased the splitting tensile strength, flexural strength, compressive strength, and modulus of elasticity by (22.54 and 40.32%), (22.22 and 35%), (21 and 35.37%), and (22 and 38.19%) compared to reference mix (NC) and the no-fine concrete mix with 10% recycled aggregate (RNC10), respectively. In comparison, the dry density was higher by (1.34%) than RNC10 and lower by (0.68%) than NC.

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Bergmans, Jef, Hadi Kazemi Kamyab, Debabrata Ghosh, Peter Van Mierloo, Hilde Carens e Peter Nielsen. "Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks". Sustainability 16, n. 8 (22 aprile 2024): 3494. http://dx.doi.org/10.3390/su16083494.

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Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.

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Mitchell, M. R., R. E. Link, Jiusu Li e Zhaohui Liu. "Microanalysis of Recycled Coarse Aggregate and Properties of No-Fines Pervious Recycled Concrete". Journal of Testing and Evaluation 39, n. 5 (2011): 103417. http://dx.doi.org/10.1520/jte103417.

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Rabehi, Rachid, Mohamed Rabehi e Mohammed Omrane. "Steel fiber's effects on the physical and mechanical characteristics of selfcompacting concrete (SCC) made of recycled gravel". International Conference on Scientific and Innovative Studies 1, n. 1 (14 aprile 2023): 295–301. http://dx.doi.org/10.59287/icsis.616.

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In order to adapt the concrete to structures with more complex and highly reinforced sections,research has been carried out in recent years in Japan with the aim of developing concrete formulationscharacterized by high workability while being stable. (Low segregation, bleeding, and compaction), withgood mechanical characteristics and durability. The culmination of this research has given rise to a newtype of concrete that can satisfy the properties mentioned above, called self-compacting concrete (SCC).SCC is characterized by its high volume of paste, a large amount of fines, the use of superplasticizers, anda low volume of gravel. For the preservation of the environment and in the vision of sustainabledevelopment, due to the increasing demand for the use of aggregates, crushed gravel can be replaced byrecycled concrete gravel. To improve the properties of SCCs based on recycled concrete gravel, metal fibersare added. The objective of this work is to study the effect of the introduction of metal fibers in selfcompacting concretes based on recycled concrete gravel on the physico-mechanical properties of theseSCCs. The results obtained show that 50% recycled concrete gravel is the best, and the 1% fibers improvethe physico-mechanical characteristics of these SCCs.

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Holeček, Petr, e Hana Stiborová. "Bacterially induced calcite formation at the surface of recycled concrete". Acta Polytechnica CTU Proceedings 40 (24 luglio 2023): 33–38. http://dx.doi.org/10.14311/app.2023.40.0033.

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The construction industry is one of the main sources of greenhouse gas emissions, and portland cement production is responsible for approximately 8 % of anthropogenic CO2 emissions. Microbially induced calcium precipitation (MICP) has the potential to partially replace cement or modify the properties of materials that would otherwise not find use in construction, for example, in concrete recycling. MICP might be an environmentally friendly method to improve the properties of recycled aggregates and form conglomerates from the finest fractions. In this paper, factors influencing MICP’s ability to solidify recycled concrete fines are thoroughly investigated. Calcium carbonate precipitate crystals produced by the bacterium Sporosarcina pasteurii were analyzed using scanning electron microscopy and energy dispersive spectroscopy.

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Shen, Peiliang, Yangyang Zhang, Yi Jiang, Baojian Zhan, Jianxin Lu, Shipeng Zhang, Dongxing Xuan e Chi Sun Poon. "Phase assemblance evolution during wet carbonation of recycled concrete fines". Cement and Concrete Research 154 (aprile 2022): 106733. http://dx.doi.org/10.1016/j.cemconres.2022.106733.

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Rabehi, Rachid, Rabehi Mohamed e Omrane Mohammed. "Study of the durability of self-compacting concrete made from recycled gravel". Journal of Engineering and Exact Sciences 9, n. 4 (6 giugno 2023): 15927–01. http://dx.doi.org/10.18540/jcecvl9iss4pp15927-01e.

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Research has been carried out in Japan recently with the aim of creating concrete formulations characterized by high workability while being stable in order to adapt concrete to structures with more complex and heavily reinforced sections. (Low segregation, compaction, and bleeding) with strong mechanical properties. The result of this research is self-compacting concrete (SCC), a new type of concrete that can fulfill the aforementioned properties. SCC is distinguished by a high paste volume, a high fines volume, the use of superplasticizers, and a low gravel volume. Due to the increasing demand for aggregates, crushed gravel may be replaced with recycled gravel in the interests of environmental conservation and sustainable development goals. Steel fibers are added to recycled concrete and gravel SCCs to improve their properties. The objective of this research is to examine the durability in the hardened state as well as the physico-mechanical characteristics of self-compacting concrete (SCC) made from recycled concrete gravel. According to the results, the best recycled concrete gravel contains 50%, and the addition of 0.5% fibers improves the properties of these SCCs.

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Rihia, Chaher, e Houria Hebhoub. "The percentage effect of slag on the behavior of a high performance concrete". MATEC Web of Conferences 330 (2020): 01040. http://dx.doi.org/10.1051/matecconf/202033001040.

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The purpose of this study is to determine the feasibility of the partial replacement of cement with recycled fines in a high performance concrete whose purpose is to minimize the use of Portland cement and reduce the environmental impact of this waste. In the context of which, we used the fines of the granulated slag from El Hadjar-Annaba as a partial replacement of cement with substitution rates of 10, 15, 20%, and to study the behaviour in the fresh state (density and workability) and the mechanical performances (compressive and flexural tensile strength) and dimensional variation in the cured state, and then compared the results found with control samples of 0% substitution rate. Subsequent to which, it can be concluded that the introduction of recycled fines reduces the density and workability and improves the concrete's mechanical performance.

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Gosk, Edyta, Katarzyna Kalinowska-Wichrowska, Marta Kosior-Kazberuk, Magdalena Joka Yildiz, Łukasz Derpeński, Przemysław Zamojski e Paweł Lipowicz. "The Basic Properties of Lightweight Artificial Aggregates Made with Recycled Concrete Fines". Sustainability 16, n. 20 (21 ottobre 2024): 9134. http://dx.doi.org/10.3390/su16209134.

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The production of lightweight aggregate based on waste is an important step towards sustainable and ecological construction. It contributes to reducing the negative impact of the construction sector on the environment by reducing the consumption of natural raw materials and reducing waste of various origins, including rubble concrete. The physical and mechanical properties, including grain shape index, water absorption, bulk density, resistance to crushing, frost resistance, leachability of heavy metals, and porosity of lightweight artificial aggregate made from rubble concrete waste (KRC) were presented in the paper. The obtained test results prove that the proposed artificial aggregate has similar water absorption and bulk density and even better frost and crushing resistance than artificial aggregates available on the market. Due to its properties, it can be used for lightweight concrete, gardening, or as a separating layer in home sewage treatment plants.

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Federowicz, Karol, Krzysztof Cendrowski e Paweł Sikora. "Low-carbon cementitious composite incorporated with biochar and recycled fines suitable for 3D printing applications: hydration, shrinkage and early-age performance". Frattura ed Integrità Strutturale 19, n. 71 (14 ottobre 2024): 91–107. http://dx.doi.org/10.3221/igf-esis.71.08.

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In recent years, the construction industry has witnessed significant advancements in concrete technology, particularly with the integration of 3D printing in cement-based materials. While this innovation offers promising opportunities for the sector, the high binder and fine particle content of 3D printing mixes presents a substantial environmental challenge due to their considerable carbon footprint. To mitigate this impact, strategies often involve substituting portions of the binder or aggregate with waste materials. This article presents a comparative analysis of two promising approaches to reducing the carbon footprint of 3D printing concrete mixes by partially replacing cement with biochar and recycled fines. The study examines the effects of these materials on the rheological properties and early-age hydration processes of the 3D printing mix. A reference mix (REF) was established, followed by the development of eight additional mixes, with four incorporating biochar and four incorporating recycled fines, each replacing 1.25%, 2.5%, 5%, and 10% of the cement volume. The findings indicate that recycled fines have a neutral effect on the spread flow diameter of the mixture but increase initial deformations in printed elements. Conversely, biochar, due to its water absorption capacity, reduces fluidity, enhancing buildability by enabling faster printing with minimal initial deformation. Additionally, replacing up to 2.5 vol.% of cement with either material accelerates the normalized heat flow, contributing to a quicker gain in mechanical properties. However, biochar increases shrinkage deformations within the first 12 hours, while recycled fines mitigate them. Importantly, replacing up to 10 vol.% of cement with these materials does not significantly compromise early compressive strength.

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Boudina, Tounsia, Dalila Benamara e Rebih Zaitri. "Optimization of High-Performance-Concrete properties containing fine recycled aggregates using mixture design modeling". Frattura ed Integrità Strutturale 15, n. 57 (22 giugno 2021): 50–62. http://dx.doi.org/10.3221/igf-esis.57.05.

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This investigation means to predict and modeling the fresh and hardened concrete behavior containing fine aggregates from concrete and brick wastes, for different recycled aggregates substitution rates. To succeed this, the design of experiments DOE method was used. It is observed that slump of recycled concrete is significantly influenced by the content in recycled concrete aggregates (RCA), natural sand (NS) and recycled brick aggregates (RBA), respectively.The compressive strength (CS) reaches a maximum value of 83.48 MPa with factors values of 25% RBA, and 75% RCA. And HPC’s based on RBA sand presented greater values of flexural strength at 7 days than HPC’s based on RCA sand, it was revealed that this is due to the RBA fines pozzolanic reaction and the production of new CSHs, which leads to better cement matrix densification.Under optimal conditions, themaximum desirability is 0.65, who has given HPC no added natural sand, by mixing recycled sands RBA (9.5%) with RCA (90.5%).The statistical terms result show that the expected models are very well correlated with the experimental data and have shown good accuracy.

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Ren, Pengfei, Bo Li, Jin-Guang Yu e Tung-Chai Ling. "Utilization of recycled concrete fines and powders to produce alkali-activated slag concrete blocks". Journal of Cleaner Production 267 (settembre 2020): 122115. http://dx.doi.org/10.1016/j.jclepro.2020.122115.

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Al-Obaidi, Z. A. "Properties of no-fines recycled aggregate concrete contains waste plastic fibers". Journal of Physics: Conference Series 1895, n. 1 (1 maggio 2021): 012012. http://dx.doi.org/10.1088/1742-6596/1895/1/012012.

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Wang, Liang, Jialai Wang, Hao Wang, Yi Fang, Wenfeng Shen, Peiyuan Chen e Ying Xu. "Eco-friendly treatment of recycled concrete fines as supplementary cementitious materials". Construction and Building Materials 322 (marzo 2022): 126491. http://dx.doi.org/10.1016/j.conbuildmat.2022.126491.

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Wu, Yuqing, Hamideh Mehdizadeh, Kim Hung Mo e Tung-Chai Ling. "High-temperature CO2 for accelerating the carbonation of recycled concrete fines". Journal of Building Engineering 52 (luglio 2022): 104526. http://dx.doi.org/10.1016/j.jobe.2022.104526.

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Jiang, Yi, Ligang Peng, Zihan Ma, Jian-xin Lu, Peiliang Shen e Chi Sun Poon. "Enhancing the treatment efficiency of recycled concrete fines with aqueous carbonation". Cement and Concrete Research 174 (dicembre 2023): 107338. http://dx.doi.org/10.1016/j.cemconres.2023.107338.

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Gorgis, Ikbal, Whab Faleh Abd e Shaker Al-Mishhadani. "Acidic solution effects on no-fines concrete produced by using recycled concrete as coarse aggregate". MATEC Web of Conferences 162 (2018): 02002. http://dx.doi.org/10.1051/matecconf/201816202002.

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This paper investigates durability of no fine concrete containing demolished concrete as coarse aggregate after crushing to different sizes. Different no fine concrete mixes were considered using Portland cement type I with two types of coarse aggregates, crushed demolished concrete and crushed natural gravel were used with two ratios by weight (1:5 and 1:7) C/Agg. Graded aggregate and single size were used with a maximum size of 20 mm. W /C ratio was kept as 0.4 for all mixes and super-plasticizer was required to keep the same flow and compaction factor value for all mixes. Cube specimens with 150mm were cured and divided to two parts, the first part was exposed to 60 cycles of freezing- thawing; the second part of the sample was immersed in Nitric Acids solution with pH of 3.5 for (7, 28, 90 and 180 days) and then tested for compressive strength. The results indicated that it is possible to produce homogenous and workable mixes by using demolished crushed concrete as coarse aggregate. The compressive strength after cycles of freezing- thawing and immersing in Nitric acid (HNO3) at (7, 28, 90 and 180) days was decreased for samples made with crushed demolished concrete. Also it is found that the performance of concrete mixes containing graded coarse aggregate and 1:5 cement/aggregate ratios was better than other mixes.

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Chang, Ching Jung, e Yung Chen Chang. "Extra-Lightweight No-Fines Cellular Concrete – Use for Non-Structural Material". Advanced Materials Research 834-836 (ottobre 2013): 713–19. http://dx.doi.org/10.4028/www.scientific.net/amr.834-836.713.

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Overexploitation has led to the destruction of resources and endangered ecological environments. Therefore, research for renewable material has become more important in the construction industry. This study used sintered lightweight aggregate made of clay to replace the coarse and fine aggregate and processed aluminum-wastage to make the foaming agents for cement, producing a brand-new extra-lightweight expanded no-fines cellular concrete. The cellular concrete not only utilizes recycled materials, but also produces an environment-friendly, green building material. Validated throughout the experiment, the cellular concrete may provide functions such as fire protection, thermal resistance, and acoustic absorption when used as non-structural material. This paper attempts to evaluate the basic physical properties of cellular concrete by different water/cement ratio (W/C) and agent/cement (A/C) ratio for the coefficients of expansion, compression strengths, and the thermal conductivity.

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Cuong, Tran Viet, Ken Kawamoto, Tran Thi Viet Nga e Nguyen Hoang Giang. "Mechanical properties of synthetic aggregate pelletized by waste concrete fines in Vietnam". Journal of Science and Technology in Civil Engineering (STCE) - HUCE 17, n. 2 (26 giugno 2023): 1–8. http://dx.doi.org/10.31814/stce.huce2023-17(2)-01.

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Due to rapid industrialization and economic growth, the generation of construction and demolition waste (CDW) from the activities of demolishing buildings is increasing in Vietnam. The Vietnamese Government has regulations on recycling and collecting CDW for reuse, recycling to environmental protection through Circular No. 08/2017/TT-BXD in 2017, and Directive 41/CT-TTg in 2020. Waste concrete fines (WCF) are generated during demolishing process or crushing of CDW materials. To save natural resources and increase the recycling rate, a disc pelleting technology has been used to recycle WCF. The pellet machine has a disk with 1.5m of diameter and 0.3m of depth; tilted at an angle of 55 degrees and the rotation speed from 15 to 22 rpm; the capacity is 0.5 to 0.8 tons per hour. This paper presents the results of pelletizing WCF research to produce synthetic aggregate (SA). The SA pelletized by WCF and cement had an apparent specific gravity of 2.45 – 2.55 g/cm3, a dry bulk specific gravity of 1.85 – 1.95 g/cm3, a crushing value of 19.2 – 29.9%, a LA (Los Angeles) value of 23 – 33% and water absorption around 13.2%. The mechanical properties of SA meet the requirement of TCVN 11969:2018, recycled aggregate type II for concrete.

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32

Boudali, S., D. E. Kerdal, K. Ayed, B. Abdulsalam e A. M. Soliman. "Performance of self-compacting concrete incorporating recycled concrete fines and aggregate exposed to sulphate attack". Construction and Building Materials 124 (ottobre 2016): 705–13. http://dx.doi.org/10.1016/j.conbuildmat.2016.06.058.

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33

A. Salih, Sh, I. N. Gorgis e W. F. Abd. "Some Properties of No-Fines Concrete Produced by Using Demolished Concrete as Recycled Coarse Aggregate". Engineering and Technology Journal 35, n. 7 (1 luglio 2017): 741–48. http://dx.doi.org/10.30684/etj.35.7a.10.

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34

Mobili, Alessandra, Chiara Giosuè, Valeria Corinaldesi e Francesca Tittarelli. "Bricks and Concrete Wastes as Coarse and Fine Aggregates in Sustainable Mortars". Advances in Materials Science and Engineering 2018 (16 settembre 2018): 1–11. http://dx.doi.org/10.1155/2018/8676708.

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The total substitution by volume of natural coarse calcareous aggregate by coarse recycled brick aggregate (RBA) and coarse recycled concrete aggregate (RCA) has been investigated to produce more sustainable and environment-friendly mortars. Aggregates were also partially substituted by their fines at 12.5% by volume. Mortars have been tested in terms of mechanical, microstructural, and durability properties. Results show that it is feasible to replace a natural calcareous aggregate entirely by recycled aggregates. In particular, the obtained mortars, even if more porous and more prone to the water capillary absorption than that manufactured with natural aggregates, result in less stiffness and thus are less subjected to crack formation, more permeable to water vapour, and less susceptible to sulphate attack.

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Oksri-Nelfia, L., P.-Y. Mahieux, O. Amiri, Ph Turcry e J. Lux. "Reuse of recycled crushed concrete fines as mineral addition in cementitious materials". Materials and Structures 49, n. 8 (17 ottobre 2015): 3239–51. http://dx.doi.org/10.1617/s11527-015-0716-1.

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Li, Junxia, e En-Hua Yang. "Macroscopic and microstructural properties of engineered cementitious composites incorporating recycled concrete fines". Cement and Concrete Composites 78 (aprile 2017): 33–42. http://dx.doi.org/10.1016/j.cemconcomp.2016.12.013.

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37

Teune, I. E., e K. Schollbach. "Triethanolamine-promoted separation of calcium from recycled concrete fines during aqueous carbonation". Resources, Conservation and Recycling 206 (luglio 2024): 107604. http://dx.doi.org/10.1016/j.resconrec.2024.107604.

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Pawluczuk, Edyta, Katarzyna Kalinowska-Wichrowska e Mahfooz Soomro. "Alkali-Activated Mortars with Recycled Fines and Hemp as a Sand". Materials 14, n. 16 (15 agosto 2021): 4580. http://dx.doi.org/10.3390/ma14164580.

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Nowadays, effective and eco-friendly ways of using waste materials that could replace natural resources (for example, sand) in the production of concrete composites are highly sought. The article presents the results of research on geopolymer composites produced from two types of waste materials—hemp and fine fractions recovered from recycled cement concrete, which were both used as a replacement for standard sand. A total of two research experiments were conducted. In the first experiment, geopolymer mortars were made using the standard sand, which was substituted with recycled fines, from 0% to 30% by weight. In the second study, geopolymers containing organic filler were designed, where the variables were (i) the amount of hemp and the percent of sand by volume (0%, 2.5%, and 5%) and(ii) the amount of hydrated lime and the percent of fly ash (by weight) (0%, 2%, and 4%) that were prepared. In both cases, the basic properties of the prepared composites were determined, including their flexural strength, compressive strength, volume density in a dry and saturated state, and water absorption by weight. Observations of the microstructure of the geopolymers using an electron and optical microscope were also conducted. The test results show that both materials (hemp and recycled fines) and the appropriate selection of the proportions of mortar components and can produce composites with better physical and mechanical properties compared to mortars made of only natural sand. The detailed results show that recycled fines (RF) can be a valuable substitute for natural sand. The presence of 30% recycled fines (by weight) as a replacement for natural sand in the alkali-activated mortar increased its compressive strength by 26% and its flexural strength by 9% compared to control composites (compared to composites made entirely of sand without its alternatives). The good dispersion of both materials in the geopolymer matrix probably contributed to filling of the pores and reducing the water absorption of the composites. The use of hemp as a sand substitute generally caused a decrease in the strength properties of geopolymer mortar, but satisfactory results were achieved with the substitution of 2.5% hemp (by volume) as a replacement for standard sand (40 MPa for compressive strength, and 6.3MPa for flexural strength). Both of these waste materials could be used as a substitute for natural sand and are examples of an eco-friendly and sustainable substitution to save natural, non-renewable resources.

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Saiz Martínez, Pablo, Daniel Ferrández, Alberto Melane-Lavado e Alicia Zaragoza-Benzal. "Characterization of Three Types of Recycled Aggregates from Different Construction and Demolition Waste: An Experimental Study for Waste Management". International Journal of Environmental Research and Public Health 20, n. 4 (19 febbraio 2023): 3709. http://dx.doi.org/10.3390/ijerph20043709.

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Achieving sustainable management and efficient use of natural resources stands out as one of the goals included in the Goals for Sustainable Development in the 2030 Agenda. The construction sector is currently far from presenting an efficient model in terms of treating waste generated by it. Variations in the physical and chemical properties of recycled aggregates coming from construction and demolition waste are one of the main reasons of their limited use in the production of construction materials. This research presents a physicochemical characterization of three different types of recycled aggregates coming from different types of waste: concrete, ceramic and mixed. Physical characterization shows that recycled concrete aggregate has better physical properties compared with mixed recycled aggregate and ceramic recycled aggregate, which makes it more suitable for use in masonry mortars and concrete, due to its higher dry density (2210.33 kg/m3), its lower content of fines (5.17%), its lower friability coefficient (24.60%), and its water absorption coefficient (6.70%). Chemical characterization shows that none of the tested recycled aggregates contains traces of harmful chemical agents that exceed the limits established by the reference regulations. Finally, the statistical analysis shows good homogeneity for these raw materials, obtaining low coefficients of variation and values within the recommended in each of the calculated confidence intervals.

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Belebchouche, Cherif, Oussama Temami, Mohamed Lyes Kamel KHOUADJIA, Salim Hamlaoui, Amirouche Berkouche e Tarek Chouadra. "Recycling of Brick and Road Demolition Waste in the Production of Concrete". Science, Engineering and Technology 4, n. 2 (25 settembre 2024): First. http://dx.doi.org/10.54327/set2024/v4.i2.154.

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Construction and public works sites generate a significant amount of waste that is often costly to dispose of. To reduce the environmental impact and promote sustainability, recycling and recovering this waste is increasingly being recognized as a viable solution. This paper presents the findings of an experimental program investigating the feasibility of using brick and road demolition waste as concrete components. By substituting a portion of sand and cement with recycled materials, this study compares the properties of the reference concrete with concrete containing varying amounts of brick waste and road demolition debris. The obtained results demonstrate that the produced concrete with up to 40 % recycled content achieved a compressive strength exceeding 20 MPa after 28 days. This study suggests that recycled brick and road demolition waste could be a sustainable and economical substitute for conventional aggregates. Incorporating these materials into concrete reduces the cement content while maintaining or even improving the fresh and hardened properties of the concrete. However, it is crucial to limit the use of road demolition sand to 10 %, crushed brick fines to 20%, and brick sand (CBS) to 30% to ensure optimal performance.

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41

Zhang, X. Y., M. X. Fan, Y. X. Zhou, D. D. Ji, J. H. Li e R. Yu. "Development of a sustainable alkali activated ultra-high performance concrete (A-UHPC) incorporating recycled concrete fines". Journal of Building Engineering 67 (maggio 2023): 105986. http://dx.doi.org/10.1016/j.jobe.2023.105986.

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42

Fawzi, Ruaa Qassim, e Hadeel Khalid Awad. "Effect of Silica Fume on Some Properties of No-Fine Concrete with Recycled Coarse Aggregate". Journal of Engineering 30, n. 03 (1 marzo 2024): 46–59. http://dx.doi.org/10.31026/j.eng.2024.03.04.

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No-fines Concrete is a lightweight porous concrete produced by omitting sand from the traditional concrete mix. It helps replenish the groundwater aquifer by directly allowing precipitation to seep into the earth thanks to its wide pores. This work studied the influence of partially replacing cement with silica fume (SF) with percentages of 5, 8, and 10% on some properties of no-fine concrete made using recycled coarse aggregate. The natural coarse aggregate (NA) was replaced with 10%, 20%, and 30% by crushed reactive powder concrete waste volume as recycled aggregate (RA). The optimum percentage was 10% RA with 10% SF, which indicated a substantial improvement in the no-fine concrete's strength, dry density, and water absorption compared to the design mix. The results exhibit increases in percentages in compressive strength, tensile strength, flexural strength, and dry density by 18%, 14%, 16%, and 1%, respectively, while exhibiting a decrease in water absorption by 5% at 28 days.

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Zaharieva, Roumiana, Daniel Evlogiev, Nikolay Kerenchev e Tsveta Stanimirova. "Modification of Quaternary Clays Using Recycled Fines from Construction and Demolition Waste". Processes 10, n. 6 (26 maggio 2022): 1062. http://dx.doi.org/10.3390/pr10061062.

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Foundation of buildings in soft soil such as quaternary clay is often associated with difficult compaction, settlement, non-uniform and/or excessive deformation, and unsatisfactory shear resistance. The present study aims to assess the possibility of using recycled fines from construction and demolition waste, such as mechanically treated gypsum and waste concrete powder (WCP), instead of ordinary binders or industrial waste, in the stabilization of quaternary clay. A detailed characterization of soil components is presented. Seven mixes with various proportions of gypsum and WCP are prepared. Main geotechnical parameters of the modified soil are studied by applying standardized methods with a few deviations. XRD analysis and pH measurements are performed. It was found that the effect of 5% to 20% recycled di-hydrate gypsum is limited to improvement in moist soil compatibility. A gypsum content of 10% positively impacts soil cohesion and the oedometer modulus. WCP is an active component, containing non-hydrated cement, portlandite, calcite and calcium silicates hydrate. As a result, by adding 5% of WCP only, significant improvement can be achieved: greater soil cohesion, reduced deformability and higher UCS. When 5% of recycled gypsum is also added, soil cohesion is further improved because of ettringite formation.

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Wang, Hao, Liang Wang, Ying Xu, Ke Cao, Yan Ge, Xuepeng Wang e Qi Li. "Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines". Materials 15, n. 15 (4 agosto 2022): 5375. http://dx.doi.org/10.3390/ma15155375.

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Sodium carbonate (Na2CO3), an environmentally friendly activator, has been shown to have vast potential for the development of sustainable alkali-activated slag mortars. However, Na2CO3-activated slag mortars exhibit a delayed reaction process and limited early-age strength development, restricting their wider application. In this work, the recycled concrete fines were calcined at a temperature of 800 °C for 1 h and then used as an auxiliary activator to improve the reaction kinetics of Na2CO3-activated slag mortars. The impact of the calcined recycled concrete fines (CRCF) dosage and Na2CO3 concentration on the compressive strength, hydration kinetics, and phase assemblage of mortars was evaluated. The results show that CRCF can react directly with Na2CO3 in the early stages, swiftly removing the CO32− in aqueous solution and providing an alkaline environment suitable for the dissolution of slag. This promotes the development of C-(A)-S-H, hydrotalcite, hemicarbonate, and monocarbonate. The hydration process and strength-giving phase of mortars can be improved further, as an increase in Na2CO3 concentration increases the initial alkaline content. Additionally, the most remarkable compressive strength value of 39.2 MPa was observed at 28 days in the mortar with 6% sodium oxide equivalent (Na2O-E) of Na2CO3 and 15% CRCF because of the synergistic effect of CRCF and Na2CO3.

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Mehdizadeh, Hamideh, Kim Hung Mo e Tung-Chai Ling. "CO2-fixing and recovery of high-purity vaterite CaCO3 from recycled concrete fines". Resources, Conservation and Recycling 188 (gennaio 2023): 106695. http://dx.doi.org/10.1016/j.resconrec.2022.106695.

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46

Jiang, Yi, Long Li, Jian-xin Lu, Peiliang Shen, Tung-Chai Ling e Chi Sun Poon. "Mechanism of carbonating recycled concrete fines in aqueous environment: The particle size effect". Cement and Concrete Composites 133 (ottobre 2022): 104655. http://dx.doi.org/10.1016/j.cemconcomp.2022.104655.

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Ananthakrishnan, V. S., Dr V. Sreevidya, S. Manoj Prabaakar e G. Ezhilarasan. "STRENGTH PROPERTIES OF LIQUID PENETRATING GEOPOLYMER NO FINES CONCRETE WITH RECYCLED COARSE AGGREGATE". International Journal of Engineering Applied Sciences and Technology 5, n. 2 (30 giugno 2020): 308–11. http://dx.doi.org/10.33564/ijeast.2020.v05i02.048.

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48

Nežerka, V., P. Havlásek e J. Trejbal. "Mitigating inclusion-induced shrinkage cracking in cementitious composites by incorporating recycled concrete fines". Construction and Building Materials 248 (luglio 2020): 118673. http://dx.doi.org/10.1016/j.conbuildmat.2020.118673.

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49

Sousa, Leila Nobrega, J. C. O. Zepper, Katrin Schollbach e H. J. H. Brouwers. "Improving the reactivity of industrial recycled concrete fines: Exploring mechanical and hydrothermal activation". Construction and Building Materials 442 (settembre 2024): 137594. http://dx.doi.org/10.1016/j.conbuildmat.2024.137594.

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50

Hassan, K. E., M. S. Kuwari e J. M. Reid. "Site Trials of Recycled and Secondary Aggregates in Concrete and Concrete Blocks in Qatar". International Journal on Pavement Engineering & Asphalt Technology 15, n. 2 (1 dicembre 2014): 37–53. http://dx.doi.org/10.2478/ijpeat-2013-0011.

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Abstract A major construction programme is underway in Qatar. A shortage of local aggregate is focusing attention on the use of recycled and secondary aggregates. Site trials using locally available materials in structural concrete and concrete blocks were carried out in three small buildings. By far the largest source of recycled and secondary aggregates in Qatar is construction, demolition and excavation waste, which is generally crudely separated into excavation waste (EW) and construction/demolition waste (CDW). The other material investigated was incinerator bottom ash (IBA). The EW was used to replace 50% of the coarse aggregate in structural C40 concrete, with the CDW replacing 50% and IBA 20% of the coarse aggregate in non-load bearing concrete blocks. The control was 100% imported gabbro coarse aggregate. The trials also incorporated replacement of 60% of the local washed sand with imported crushed rock fines; this was investigated because the reserves of suitable concrete sand in Qatar are limited. Results after one year show the materials giving equivalent or better performance than the primary aggregate controls. The Qatar Construction Specification will be updated to permit greater use of recycled and secondary aggregates (RSA) and further trials are planned in a range of applications, including unbound subbase and pavement concrete. Wider use of these materials will reduce reliance on imported aggregates. The site trials won an award for the most innovative project from the Qatar Contractors Forum 2013.

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