scholarly journals Durability Studies on the Recycled Aggregate Concrete in China over the Past Decade: A Review

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Zhiming Ma ◽  
Qin Tang ◽  
Dingyi Yang ◽  
Guangzhong Ba
Keyword(s):  
Water Absorption ◽  
Absorption Rate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Rapid Urbanization ◽  
Aggregate Concrete ◽  
The Past ◽  
Water Absorption Rate ◽  
Average Water

Since China hosted the Olympic Games in 2008, a mass of construction and demolition (C&D) wastes were produced with the rapid urbanization construction. Recycling the C&D waste into recycled aggregates (RA) is an effective method for reducing the amount of C&D wastes. Many studies on the properties of RA and the durability of recycled aggregate concrete (RAC) were conducted in China over the past decade. Due to the restrictions of various languages, some valuable studies on the durability of RAC are hard to be acquired by the scholars around the world. Therefore, this paper is developed to review the studies on the durability of RAC in China, and the shrinkage behavior, chloride permeability, carbonation behavior, and freeze-thaw resistance of RAC are, respectively, introduced. Considering the waste concrete, bricks, and ceramics used in preparing RA are frequently mixed together in China, this study proposes an index of average water absorption rate to quantify the effects of RA types, quality, and replacement percentages on the durability of RAC. Meanwhile, the relationship between the average water absorption rate of RA and the durability parameters of RAC is established. Finally, the improving methods of RAC durability are introduced, and the RA particle shaping and carbonation modification are emphasized.

Mechanical Properties and Permeability of Recycled Aggregate Concrete at Low Water/Binder Ratio

2011 ◽  
Vol 477 ◽  
pp. 16-22 ◽  
Author(s):  
Gai Fei Peng ◽  
Qi Bin Liu ◽  
Zhu Bo Guo ◽  
Qiao Xing Hou ◽  
Si Qi Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Absorption ◽  
Experimental Research ◽  
Chloride Ion ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Binder Ratio ◽  
Water Binder Ratio

This paper presents an experimental research on mechanical properties and permeability of recycled aggregate concrete (RAC). Concretes at a water/binder ratio of 0.255 were broken into recycled aggregates (RA). A type of thermal treatment was employed to remove mortar in RA. Tests were conducted on aggregate to measure water absorption and crushed values, and on RAC and natural aggregate concrete (NAC) to measure compressive strength, tensile splitting strength, and fracture energy. The results revealed that both gravel damage and mortar attached can significantly influence the water absorption and crushed value of RA. The mechanical properties RAC were obviously lower than those of NAC at an identical mix proportion. Moreover the removal of mortar caused a decrease in mechanical properties. The behavior of the chloride ion penetration of RAC under compressive loading is different that of NAC, which may be related to the flaws of RA. Further experimental research is needed to identify its mechanism.

scholarly journals Effects of Concrete Grades on Strength Characteristics of Metakaolin Modified Recycled Aggregate Concrete

2021 ◽  
Vol 18 (3) ◽  
pp. 184-193
Author(s):  
A.U. Adebanjo ◽  
B.I.O. Dahunsi ◽  
J.O. Labiran
Keyword(s):  
Specific Gravity ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Concrete Production ◽  
Aggregate Impact Value ◽  
Control Samples

In this study, locally produced Metakaolin (MK) was used as an admixture in recycled aggregate concrete of grades M 25 and M 30. The content of MK varied from 0-15% at 5% intervals. The physical and mechanical properties (bulk density, specific gravity, water absorption, aggregate crushing value and aggregate impact value) of aggregates were determined, the chemical composition as well as reactivity of MK was evaluated using X-Ray Fluorescence (XRF) technique and modified Chappelle test. The workability  (slump) and strength (compressive and split tensile) properties of fresh and hardened RAC were examined relative to that of conventional concrete. The results of the experiments revealed that the specific gravity (SG), water absorption and aggregate impact value of recycled aggregates (RA) were 2.23, 5.35% and 32%, respectively. The MK used had an optimum reactivity of 2060.8 mg of Ca(OH)2 fixed at a temperature of 660 oC. The slump values for M 25 and M 30 control specimens were 72 mm and 65 mm, respectively while the slump values of MK modified RAC decreased from 67-45 mm for M 25 and 55-35 mm for M 30 as MK increased from 0-15%. The 56th-day compressive strength of the control samples was 21.73 N/mm2 for M 25 and 26.8 N/mm2 for M 30, respectively, while RAC samples ranged from 14.96 - 17.04 N/mm2 for M 25 and 20.55 - 22.67 N/mm2 for M 30 whereas the split tensile strength for the control samples was 2.71 N/mm2 and 3.06 N/mm2 for the two grades in that sequence, while those of RAC ranged from 2.26-2.49 N/mm2 for M 25 and 2.62 – 2.84 N/mm2 for M 30. Despite the fact that metakaolin modified RAC had lower strength properties than conventional concrete, the use of 10% metakaolin as a RA modifier in concrete production will provide a sustainable alternative to conventional aggregates in concrete mix design.

scholarly journals Using Neural Networks to Determine the Significance of Aggregate Characteristics Affecting the Mechanical Properties of Recycled Aggregate Concrete

2018 ◽  
Vol 8 (11) ◽  
pp. 2171 ◽  
Author(s):  
Zhenhua Duan ◽  
Shaodan Hou ◽  
Chi-Sun Poon ◽  
Jianzhuang Xiao ◽  
Yun Liu
Keyword(s):  
Neural Networks ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Specific Gravity ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Curing Age

It has been proved that artificial neural networks (ANN) can be used to predict the compressive strength and elastic modulus of recycled aggregate concrete (RAC) made with recycled aggregates from different sources. This paper is a further study of the use of ANN to analyze the significance of each aggregate characteristic and determine the best combinations of factors that would affect the compressive strength and elastic modulus of RAC. The experiments were carried out with 46 mixes with several types of recycled aggregates. The experimental results were used to build ANN models for compressive strength and elastic modulus, respectively. Different combinations of factors were selected as input variables until the minimum error was reached. The results show that water absorption has the most important effect on aggregate characteristics, further affecting the compressive strength of RAC, and that combined factors including concrete mixes, curing age, specific gravity, water absorption and impurity content can reduce the prediction error of ANN to 5.43%. Moreover, for elastic modulus, water absorption and specific gravity are the most influential, and the network error with a combination of mixes, curing age, specific gravity and water absorption is only 3.89%.

scholarly journals Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

2021 ◽  
Vol 13 (10) ◽  
pp. 5741
Author(s):  
Muhammad Junaid Munir ◽  
Syed Minhaj Saleem Kazmi ◽  
Yu-Fei Wu ◽  
Xiaoshan Lin ◽  
Muhammad Riaz Ahmad
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Polypropylene Fibre ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Peak Strain ◽  
Stress Strain ◽  
Polypropylene Fibres ◽  
Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

scholarly journals Effects of Imposed Damage on the Capillary Water Absorption of Recycled Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Gao ◽  
Zhiming Ma ◽  
Jianzhuang Xiao ◽  
Fuan Li
Keyword(s):  
Absorption Coefficient ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Capillary Absorption ◽  
Capillary Water ◽  
Aggregate Concrete ◽  
Capillary Water Absorption ◽  
Freeze Thaw ◽  
Loading Level

Capillary water absorption of concrete is closely related to its pore structure, permeability, and durability. This paper intensively investigates the effects of imposed damage, including freeze-thaw damage and loading damage, on the capillary water absorption of recycled aggregate concrete (RAC). Freeze-thaw cycle test, loading test, and the experiment of capillary water absorption were carried out, respectively. The results demonstrate that the addition of recycled coarse aggregate (RCA) results in the increase in the capillary absorption behavior of RAC without imposed damage, and there exists a linear correlation between the behaviors of capillary water absorption and chloride penetration of RAC. The imposed freeze-thaw damage or load damage of RAC boosts with the increase of RCA replacement percentages after suffering the same freeze-thaw cycles or loading level. The imposed freeze-thaw damage and load damage further lead to the increase in the capillary water absorption of RAC, and the capillary absorption coefficient of RAC increases linearly with the increased RCA replacement percentages, after suffering the same freeze-thaw cycles or loading level. Furthermore, capillary absorption coefficient increases linearly with the growth of imposed freeze-thaw damage or load damage degree, which can be used to estimate the capillary absorption behavior of RAC exposed to the extreme environment.

scholarly journals MECHANICAL PROPERTIES OF RECYCLED AGGREGATE CONCRETE WITH STEEL FIBER: A REVIEW

2019 ◽  
Vol 26 (3) ◽  
pp. 37-42
Author(s):  
Ashtar S. Al-Luhybi
Keyword(s):  
Mechanical Properties ◽  
Steel Fiber ◽  
Recycled Aggregate Concrete ◽  
Strength Characteristics ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Building Process

In the building process, the recycling of aggregates arising from building and demolition debris is one of the best alternatives to maintain the environment and the areas needed to bury these debris. It also helps to preserve natural concrete sources from depletion efficiently. The use of recycled aggregates in new concrete manufacturing, however, leads to a decrease in concrete\\\’s strength characteristics. This reduction rises with the rise in the percentage of recycled aggregates used in concrete, which has caused many researchers to undertake many researches on how to enhance the characteristics of recycled aggregate-containing concrete. This paper presents several studies that examined the effect of adding steel fiber to improve the properties of concrete containing a coarse recycled aggregate.

Shear strength of interfaces in natural and in recycled aggregate concrete

2017 ◽  
Vol 44 (3) ◽  
pp. 212-222
Author(s):  
Shakeel Ahmad Waseem ◽  
Bhupinder Singh
Keyword(s):  
Shear Strength ◽  
Shear Plane ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Failure Envelope ◽  
Interface Shear ◽  
Aggregate Concrete ◽  
Normal Strength ◽  
Strength Models

Shear strength of interfaces in natural aggregate concrete and in recycled aggregate concrete has been investigated using initially uncracked push-off specimens by varying the following parameters: replacement level of the recycled aggregates (0%, 50%, and 100%), concrete grade (normal-strength and medium-strength), and clamping force on the shear plane. Development of truss action for resisting interface shear was indicated by the observed crack patterns in the tested specimens and a truss-based analysis recommended in the literature in combination with a simplified failure envelope for concrete subjected to biaxial stresses has been used for shear strength predictions of the tested specimens. The proposed methodology, which is considered to be more rational than the empirical shear strength models available in the literature was calibrated for both the concrete types and gave conservative and reasonably accurate shear strength predictions for selected experiments taken from the literature.

scholarly journals Sulfate Resistance of Recycled Aggregate Concrete with GGBS and Fly Ash-Based Geopolymer

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1247 ◽  
Author(s):  
Jianhe Xie ◽  
Jianbai Zhao ◽  
Junjie Wang ◽  
Chonghao Wang ◽  
Peiyan Huang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Construction Projects ◽  
High Performance ◽  
High Performance Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Sulfate Resistance ◽  
Coarse Aggregates

There is a constant drive for the development of ultra-high-performance concrete using modern green engineering technologies. These concretes have to exhibit enhanced durability and incorporate energy-saving and environment-friendly functions. The object of this work was to develop a green concrete with an improved sulfate resistance. In this new type of concrete, recycled aggregates from construction and demolition (C&D) waste were used as coarse aggregates, and granulated blast furnace slag (GGBS) and fly ash-based geopolymer were used to totally replace the cement in concrete. This study focused on the sulfate resistance of this geopolymer recycled aggregate concrete (GRAC). A series of measurements including compression, X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests were conducted to investigate the physical properties and hydration mechanisms of the GRAC after different exposure cycles in a sulfate environment. The results indicate that the GRAC with a higher content of GGBS had a lower mass loss and a higher residual compressive strength after the sulfate exposure. The proposed GRACs, showing an excellent sulfate resistance, can be used in construction projects in sulfate environments and hence can reduce the need for cement as well as the disposal of C&D wastes.

scholarly journals A Review on Alkali-Silica Reaction Evolution in Recycled Aggregate Concrete

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2625 ◽  
Author(s):  
Miguel Barreto Santos ◽  
Jorge De Brito ◽  
António Santos Silva
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Mitigation Measures ◽  
Alkali Silica Reaction ◽  
Aggregate Concrete ◽  
Reactive Silica ◽  
Natural Aggregates ◽  
Exposure Conditions ◽  
Lack Of Knowledge

Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its prevention and mitigation, but despite the efforts made, there is still no efficient cure to control its expansive consequences. The incorporation of recycled aggregates in concrete raises several ASR issues, mainly due to the difficult control of the source concrete reactivity level and the lack of knowledge on ASR’s evolution in new recycled aggregate concrete. This paper reviews several research works on ASR in concrete with recycled aggregates, and the main findings are presented in order to contribute to the knowledge and discussion of ASR in recycled aggregate concrete. It has been observed that age, exposure conditions, crushing and the heterogeneity source can influence the alkalis and reactive silica contents in the recycled aggregates. The use of low contents of highly reactive recycled aggregates as a replacement for natural aggregates can be done without an increase in expansion of concrete. ASR expansion tests and ASR mitigation measures need to be further researched to incorporate a higher content of recycled aggregates.

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