Removal of cement mortar remains from recycled aggregate using pre-soaking approaches

Abstract. Recycled aggregate—rural building material wastes pretreated by cement mortar—are applied into concrete with different replacement rates: 0, 25%, 50%, 75%, and 100%. Results from measurements of compressive strength, cleavage tensile strength, mass loss after fast freeze-thaw cycles, and compressive strength loss indicate that a different recycled aggregate replacement rate certainly influences concrete mechanical properties and frost resistance. Recycled aggregate replacement rates less than 75% performs better than common concrete. Data from the 100% replacement rate is worse than that of rates less than 75% but still satisfy the general demands of GB standard on C30 concrete.

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Structural Concrete with Recycled Aggregate: Advances in Mechanical Properties, Durability and Sustainability

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.847.553 ◽

2016 ◽

Vol 847 ◽

pp. 553-558 ◽

Cited By ~ 1

Author(s):

Marc Antonio Liotta ◽

Marco Viviani ◽

Carlotta Rodriquez

Keyword(s):

Cement Mortar ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Mix Design ◽

Elastic Behavior ◽

Structural Concrete ◽

Concrete Aggregates ◽

Recycled Concrete Aggregates ◽

Ordinary Concrete

A large number of tests has been carried out in the last 15 years all around the world to study the possibility to use recycled concrete aggregates (RCA) to produce structural concrete.Earlier tests indicated that RCA concrete had lower properties in comparison to ordinary concrete, such as lower elastic modulus, a more brittle post-elastic behavior, lower workability, higher shrinkage and creep.Most of these issues have been addressed to the content of cement mortar remaining in adhesion to the aggregate after the recycling processes and that cannot be totally eliminated without high economic and ecological costs. This cement mortar which has undergone the crushing process creates zones of weakness in the RCA, causes higher water absorption, higher concrete porosity and causes the decay of the aforementioned properties.More recent tests prove that Recycled Concrete shows this peculiar problems only with a percentage of substitution of standard aggregates with RCA higher than 30%. Under this percentage recycled aggregate concrete (RAC) can be considered as a standard concrete, on condition that an appropriate mix design is performed.

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Effect of some Key Factors on the Strength of Recycled Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.503-504.576 ◽

2012 ◽

Vol 503-504 ◽

pp. 576-581

Author(s):

Xue Bing Zhang ◽

Zhi Fang

Keyword(s):

Coarse Aggregate ◽

Cement Mortar ◽

Recycled Concrete ◽

Recycled Aggregate ◽

Key Factors ◽

Ordinary Concrete ◽

Concrete Mix ◽

Rate Maximum ◽

Cement Strength ◽

Granule Diameter

Because there exists a used cement mortar layer outside the recycled aggregate, there are more interfaces inside recycled concrete, which would result in recycled concrete has different properties from ordinary concrete. In this paper, the effect of such key factors for recycled concrete mix ratio as water-cement ratio, cement strength, sand rate, maximum granule diameter and gradation on the properties of concrete with recycled coarse aggregate was studied by experiment, and the some useful suggestion for mix ratio of recycled concrete was provided.

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Development of Performance Optimization of Recycled Aggregate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.811.254 ◽

2013 ◽

Vol 811 ◽

pp. 254-257

Author(s):

Wei Li ◽

Ying Li ◽

Hai Ying Zhang

Keyword(s):

Performance Optimization ◽

Absorption Rate ◽

Cement Mortar ◽

Treatment Approach ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Interfacial Zone ◽

Cement Slurry ◽

Aggregate Concrete

Recycled aggregate concrete (RAC) differ from natural aggregate concrete in mechanical and durability properties. The poorer qualities of recycled aggregate (RA) limit utilization of RAC in engineering. Cement mortar attached on the surface of recycled aggregate result in higher water absorption rate. Also, interfacial zone between recycled aggregate and new mortar consist of loose and porous hydrates. Investigation is devoted to effects of different approaches on improving performance of RA to compensate the lower quality of RA. The pre-soaking treatment approach reduces the old cement mortar and removes the weaker link in interfacial zone. Moreover, The two-stage mixing approach (TSMA) is adopted, leads to the formation of a thin layer of cement slurry on the surface of RA which permeates into the porous old cement mortar, filling up the old cracks and voids for increasing compressive strength. Correlations in methods have been obtained and discussed.

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Effects of Recycled Aggregates on Water-Cement Ratio for Concrete

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.423-426.1010 ◽

2013 ◽

Vol 423-426 ◽

pp. 1010-1013 ◽

Cited By ~ 3

Author(s):

Wee Kang Choong ◽

Lau Teck Leong ◽

Choon Seng Sin ◽

Abdullahi Ali Mohamed

Keyword(s):

Cement Mortar ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Structural Concrete ◽

Cement Ratio ◽

Water Cement Ratio ◽

Different Origins ◽

Concrete Elements

Recycled aggregate differs from primary aggregate in that it constitutes of two types of materials: the primary aggregate and the attaching cement mortar. This study was conducted in order to investigate the effects on water-cement ratio for concrete cast with recycled aggregates derived from different origins (hollow blocks & structural concrete elements) and different mixed proportions of recycled aggregate contents. The outcomes of test indicate that higher water cement ratios are required for concrete cast with recycled aggregates as compare to those cast with primary aggregates. Also there appear no obvious relationships or consistencies that can be drawn among types of recycled aggregate.

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Carbonation Effects and Its Mitigation Measures in Concrete/Cement Mortar Mass Made of Cent Percentage Recycled Coarse and Fine Aggregates

International Journal of Emerging Trends in Engineering Research ◽

10.30534/ijeter/2021/15922021 ◽

2021 ◽

Vol 9 (2) ◽

pp. 109-115

Keyword(s):

Cement Mortar ◽

Recycled Aggregate ◽

Mitigation Measures ◽

Concrete Aggregate ◽

Processing Unit ◽

Effective Solution ◽

Conventional Concrete ◽

Fine Aggregates ◽

Processing Plants ◽

Intended Use

The recycled demolished concrete aggregate obtained from processing unit contains the maximum amount of calcium hydroxide (lime) andthese lime inreaction with atmosphericcarbon dioxide and forming a calcium carbonate and reducing the PH of the aggregatesand making the aggregates mass carbonated. These carbonated aggregates when used in concrete/cement mortar results in intense carbonated mass with PH of the mass less than 9 and thereby damaging the mass and rendering it unfit for its intended use. The research deals with the process and technique dealing with improving the surface and internal structure of the recycled aggregate massobtained from processing plants andmaking it fit for its usage in production of concrete /cement mortar mass and analyzing the process of the carbonation in the concrete/cement mass prepared with conventional and treated and untreated demolished concrete coarse and fine aggregates. The results obtained have shown a surface modificationand surface treatment methods founds to be an effective solution countering the carbonation of the aggregatesand the treatment helps in retaining the hydroxideion concentration (OH-) andits usage in the concrete/cement mortar mass helps in retaining the alkalinity at par with conventional concrete andmakes mass more dense and self resilient

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