Development of Performance Optimization of Recycled Aggregate

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.

Quality Improvement of Recycled Aggregate Concrete

2006 ◽  
Vol 302-303 ◽  
pp. 308-313 ◽  
Author(s):  
Vivian W.Y. Tam ◽  
X.F. Gao ◽  
C.M. Tam
Keyword(s):  
Compressive Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Two Stage ◽  
New Approach ◽  
Aggregate Concrete ◽  
Strength Based ◽  
Mixing Method ◽  
Strength Variability

The developments of recycled aggregate concrete pressing hard in construction activities; however, the limitations on their applications had never being ended. The focus of this paper is: i) investigating the waste management strategy in construction; ii) proposing the two-stage mixing approach (TSMA) to improve the quality of RAC; and iii) experimenting the TSMA and assessing the benefits possibly gained. It proposes a new approach in mixing concrete, namely, the two-stage mixing method, to improve compressive strength of RAC and lower its strength variability. The replacement ratio from zero to thirty is under experiment on their compressive strength. Based upon the experimental results, improvements of 31 % in strength at 28 days with 30 % RA substitute was achieved. The effect can be attributably to the porous nature of the RA and the pre-mix process which can make some pores filled up resulting in a denser concrete and thus leading to higher strength when compared with the traditional mixing approach. Therefore, two-stage mixing approach can open up a wider application of recycled aggregate concrete.

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.

scholarly journals A Study on the Properties of Recycled Aggregate Concrete and Its Production Facilities

2019 ◽  
Vol 9 (9) ◽  
pp. 1935 ◽  
Author(s):  
Jung-Ho Kim ◽  
Jong-Hyun Sung ◽  
Chan-Soo Jeon ◽  
Sae-Hyun Lee ◽  
Han-Soo Kim
Keyword(s):  
Drying Shrinkage ◽  
Quality Standards ◽  
Poor Quality ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Freezing And Thawing ◽  
Construction Waste ◽  
Aggregate Concrete ◽  
Air Volume

In recent years, the amount of construction waste and recycled aggregate has been increasing every year in Korea. However, as the recycled aggregate is poor quality, it is not used for concrete, and the Korean government has strengthened the quality standards for recycled aggregate for concrete. In this study, research was conducted on the mechanical and durability characteristics of concrete using recycled aggregate, after developing equipment to improve the quality of recycled aggregate to increase the use of recycled aggregate for environmental improvements. The results illustrated improvements in the air volume, slump, compressive strength, freezing and thawing resistance, and drying shrinkage. Furthermore, this study is expected to contribute to the increased use of recycled aggregate in the future.

Development and Subjects of Recycled Aggregate Concrete in Japan

2006 ◽  
Vol 302-303 ◽  
pp. 288-300 ◽  
Author(s):  
Yoshio Kasai
Keyword(s):  
Processing Method ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
General Character ◽  
Aggregate Concrete

The quality of RCA is influenced by the processing method and quality of original concrete. The general character of RCA, RCA and TR A 0006-2000(concrete using recycled aggregate) are introduced. The execution of RAC work, examples of real constructions with RAC, recycling of concrete powder originated from production of RAC and barriers of using RAC are discussed.

Study of Surface Modification of Recycled Aggregate and Interfacial Zone Microstructure of the Concrete

2010 ◽  
Vol 150-151 ◽  
pp. 313-316 ◽  
Author(s):  
Hong Zhi Cui ◽  
Feng Xing
Keyword(s):  
Surface Modification ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Hardened Cement ◽  
Interfacial Zone ◽  
Aggregate Concrete ◽  
Optimal Value ◽  
High Concentrations ◽  
Zone Microstructure

Due to most of recycled aggregate (RA) possesses higher water absorption, therefore, the process of mixing recycled aggregate concrete (RAC) is more complex than that of normal aggregate concrete (NAC). In this paper, an organosilicone modifier was used to modify RA to reduce its water absorption. Four mixes of concrete were made up with modified RA at a concentration of 1:1, modified RA at a concentration of 1:2, unmodified RA, and NA, respectively. The water absorption unmodified RA and modified RA was compared, and effect of RA surface modification on the microstructure of the interfacial transition zone (ITZ) between the RA and the hardened cement paste was examined. The investigation results show that a higher concentration of modifier is more effective in reducing the water absorption of RA; and there is an optimal value of modifier concentration, and the use of in high concentrations modifier will adversely affect the integrity of interfacial zone.

Analysis of Microstructure of Interfacial Transition Zone (ITZ) in Recycled Aggregate Concrete

2013 ◽  
Vol 811 ◽  
pp. 249-253 ◽  
Author(s):  
Wei Li ◽  
Hai Ying Zhang
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Interfacial Structure ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Interfacial Zone ◽  
Aggregate Concrete ◽  
Mortar Strength

Experiments on influence of species of aggregate and mixing method on interfacial zone in recycled aggregate concrete were investigated. SEM observations revealed that a recycle normal-strength concrete aggregate consist of loose and porous interfacial structure, whereas a recycled high performance concrete (HPC) aggregate and a triple mixing (TM) consist mainly of dense hydrates. Various admixtures on ITZ was produced that consumed CH in the pore, modified attached cement mortar. Strength of recycled concrete was explained by interaction between cements paste and recycled aggregate. The result verified that the relatively dense pore structure of the recycled concrete benefit to development of mechanical properties.

Application of Molten Slag Fine Aggregate Concrete Using Superplasticizer

2006 ◽  
Vol 302-303 ◽  
pp. 329-338
Author(s):  
Shuzo Otsuka ◽  
Yoshihisa Nakata ◽  
Takeshi Saito ◽  
Hiroki Takahashi ◽  
Keishi Tobinai ◽  
...  
Keyword(s):  
Molten Slag ◽  
Full Scale ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
Aggregate Concrete ◽  
Significant Difference

With increasing number of melting-solidification plants for the domestic wastes and incineration ashes, the resulting molten slag is now expected as a recycled aggregate for concrete in Japan, while application examples until now are limited to non-loadbearing pre-cast concrete and concrete secondary products. This study deals with a full-scale application of molten slag recycled fine aggregate. Starting with the inspection of monthly variations in quality of molten slag fine aggregate in a plant, construction of a full-scale structure was attempted using the recycled aggregate concrete with a superplasticizer. During construction, pumpability of the recycled concrete was examined and the quality of hardened concrete in the structure was evaluated. It was shown that quality variation of the molten slag fine aggregate during eight months was sufficiently small, and pumpability as well as concrete quality in structure showed no significant difference with those of the ordinary concrete.

scholarly journals INFLUENCE OF QUALITY OF RECYCLED AGGREGATE ON QUALITY OF RECYCLED AGGREGATE CONCRETE

1995 ◽  
Vol 60 (474) ◽  
pp. 11-20 ◽  
Author(s):  
Masafumi KIKUCHI ◽  
Yasuhiro DOUSYOU ◽  
Akira YASUNAGA ◽  
Kyouji EHARA ◽  
Akira MASUDA
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete
Sign in / Sign up

Export Citation Format

Share Document