Enhancement technologies of recycled aggregate – Enhancement mechanism, influencing factors, improvement effects, technical difficulties, life cycle assessment

Chen, Feng; Cui, Buwen; Huang, Yihonge; Guo, Hui; Zhang, Wenyan; Zhu, Jianping

doi:10.1016/j.conbuildmat.2021.126168

Cited by 57 publications

(13 citation statements)

References 88 publications

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“…Based on the above analysis, it can be seen that the composite impregnation treatment of sodium silicate and silane has abundant hydration products in the transition zone of the RAC S1 has a clear boundary between the new and old mortars, but there is no obvious crack in the ITZ. This is because when the RCA makes contact with the cement mortar, the hydrolysis products of sodium silicate on the aggregate surface and in the pores can react with Ca 2+ and Al 3+ in the hydration products of cement to generate calcium silicate hydrate and calcium aluminate hydrate, thus accelerating the hydration and setting of cement [30]. The ITZ of S2 was filled with abundant hydration products, and the surface of the old mortar was covered with an obvious organic alkyl layer, which enhanced the structural compactness.…”

Section: Analysis Of the Internal Microstructure Of Recycled Aggregat...mentioning

confidence: 99%

Effect of Composite Impregnation on Properties of Recycled Coarse Aggregate and Recycled Aggregate Concrete

Zhong

Tian

et al. 2022

Buildings

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To improve the properties of recycled aggregate concrete, single and composite impregnation treatments were carried out on recycled coarse aggregates with sodium silicate solution, silane slurry, and polyvinyl alcohol solution. The effects of the three chemical modifiers and different impregnation methods on the apparent density, water absorption, and crushing index of recycled coarse aggregates, as well as the basic properties of recycled aggregate concrete, were investigated. Additionally, the microstructure of the surface of recycled coarse aggregate and the interior of recycled aggregate concrete were analyzed by scanning electron microscopy. The experimental results show that the water absorption of recycled coarse aggregate soaked in polyvinyl alcohol solution decreases most significantly, reaching 64.56%. Only the combination of sodium silicate and silane impregnation produces a positive compounding effect, with a significant increase in the apparent density and a significant reduction in the crushing index of the recycled coarse aggregate. Compared with untreated concrete, the slump, compressive strength, splitting tensile strength, and flexural strength of recycled aggregate concrete prepared by sodium silicate and silane composite impregnation are increased by 9.8%, 26.53%, 21.70%, and 14.72%, respectively. The microstructure analysis shows that the composite impregnation treatment of sodium silicate and silane is most conducive to filling the cracks and holes on the surface of recycled coarse aggregate, which makes the interfacial transition zone of recycled aggregate concrete more compact and the structure more stable.

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Section: Analysis Of the Internal Microstructure Of Recycled Aggregat...mentioning

confidence: 99%

Effect of Composite Impregnation on Properties of Recycled Coarse Aggregate and Recycled Aggregate Concrete

Zhong

Tian

et al. 2022

Buildings

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“…However, the performance of RAC is dependent on the quality of the RA itself. Due to the high permeability and low strength of RAs, they are not used in engineering practice on a large scale [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties and Durability of Geopolymer Recycled Aggregate Concrete: A Review

et al. 2023

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Geopolymer recycled aggregate concrete (GPRAC) is a new type of green material with broad application prospects by replacing ordinary Portland cement with geopolymer and natural aggregates with recycled aggregates. This paper summarizes the research about the mechanical properties, durability, and microscopic aspects of GPRAC. The reviewed contents include compressive strength, elastic modulus, flexural strength, splitting tensile strength, freeze–thaw resistance, abrasion resistance, sulfate corrosion resistance, and chloride penetration resistance. It is found that GPRAC can be made to work better by changing the curing temperature, using different precursor materials, adding fibers and nanoparticles, and setting optimal mix ratios. Among them, using multiple precursor materials in synergy tended to show better performance compared to a single precursor material. In addition, using modified recycled aggregates, the porosity and water absorption decreased by 18.97% and 25.33%, respectively, and the apparent density was similar to that of natural aggregates. The current results show that the performance of GPRAC can meet engineering requirements. In addition, compared with traditional concrete, the use of GPRAC can effectively reduce carbon emissions, energy loss, and environmental pollution, which is in line with the concept of green and low-carbon development in modern society. In general, GPRAC has good prospects and development space. This paper reviews the effects of factors such as recycled aggregate admixture and curing temperature on the performance of GPRAC, which helps to optimize the ratio design and curing conditions, as well as provide guidance for the application of recycled aggregate in geopolymer concrete, and also supply theoretical support for the subsequent application of GPRAC in practical engineering.

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“…The method of consolidating soil based on inducing calcium carbonate precipitation is a soil improvement technology that has emerged in recent years, due to its advantages of simple construction [ 6 , 7 ], environmental friendliness [ 8 , 9 ], low cost [ 10 ] and easy control [ 11 ], and it has received extensive attention from the academic community. However, the MICP technology based on microbial induced calcium carbonate precipitation has problems such as biosafety risks [ 12 ], insufficient cementation of fine-grained soils [ 13 , 14 ] and the need for an aerobic environment for bacterial growth [ 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Different Improvement Schemes of EICP-Lignin Solidified Silt

Sun

Zhong

et al. 2023

Materials

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In practical engineering applications, silt is prone to liquefaction and quicksand. This paper mainly studies the improvement effects of urease, lignin and their mixture on the strength and liquefaction resistance of silt. Based on the results and phenomena of an unconfined compressive strength and dynamic triaxial test, the improvement effects of the compressive strength, deformation resistance and liquefaction resistance of silt under different improvement schemes are analyzed, and the optimal values of the cement or lignin when enzyme-induced calcium carbonate precipitation (EICP) technology, lignin alone or EICP and lignin are obtained. The results show that the optimum concentration of the constant temperature and humidity sample (referred to as the constant humidity sample) and the constant temperature immersion sample (referred to as the soaking sample) of urease in the unconfined compressive strength test is 1.0 mol/L, and the compressive strength of the soaking sample is 4.9 MPa, which is 1.56 times that of the constant humidity sample; the optimum addition ratio of the lignin-improved constant humidity sample is 3%, and its compressive strength is 2.07 Mpa; the optimum addition ratio of the samples immersed at constant temperature is 4%, and the compressive strength is 3.05 MPa; when urease combines with lignin to improve silt, 4% is the best lignin addition ratio, the compressive strength of the constant humidity sample reaches 1.57 Mpa and the compressive strength of the soaking sample reaches 3.75 MPa; in the dynamic triaxial multi-stage cyclic load test, all samples were cured at constant humidity sample, and in the urease modified silt scheme, 1.0 mol/L was the optimal cement concentration; in the scheme of improving silt with lignin, 3% is the optimal addition ratio; when 1.25 mol/L cementation solution plus urease crude extract is combined with different ratios of lignin in the experimental scheme, 3% is the best lignin addition ratio.

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Enhancement technologies of recycled aggregate – Enhancement mechanism, influencing factors, improvement effects, technical difficulties, life cycle assessment

Cited by 57 publications

References 88 publications

Effect of Composite Impregnation on Properties of Recycled Coarse Aggregate and Recycled Aggregate Concrete

Effect of Composite Impregnation on Properties of Recycled Coarse Aggregate and Recycled Aggregate Concrete

Mechanical Properties and Durability of Geopolymer Recycled Aggregate Concrete: A Review

Experimental Study on Different Improvement Schemes of EICP-Lignin Solidified Silt

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