Experimental Study on Anti-Permeability of Active Admixture Recycled-Concrete

2013 ◽  
Vol 438-439 ◽  
pp. 121-124
Author(s):  
Ai Jiu Chen ◽  
Xiao Pei Sun ◽  
Fen Yang
Keyword(s):  
Fly Ash ◽  
Coarse Aggregate ◽  
Polypropylene Fiber ◽  
Recycled Concrete ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Recycled Coarse Aggregate ◽  
Slag Powder ◽  
Optimum Proportion ◽  
Active Admixture

Active admixture recycled-concrete (AARC) is one of green high performance concretes, which took active admixture and fly ash into recycled concrete to replace part of cement. This paper researches the relationship of seepage resistance grade and chloride diffusion coefficient of recycled concrete by the regressive analysis of experimental data from NEL and gradually pressure method. The mufti-factor (slag powder, fly ash, air-entraining agent, polypropylene fiber, recycled coarse aggregate) and multi-level experiments of anti-permeability of concrete were carried out by orthogonal experiment method, and the optimum proportion of concrete is determined. The results show that seepage resistance grade of 16 groups AARC all reached W13, and chloride diffusion coefficient was between 0.5~1×10-8cm2/s, the permeability grade is IV. The impermeability of the AARC is excellent. The rate of recycled coarse aggregate and slag powder were the most important factors for the impermeability properties of concrete, the optimum proportion of concrete was 10% slag powder, 20% fly ash, 1/10000 air-entraining agent, 1.0 kg/m3 polypropylene fiber and 40% recycled coarse aggregate.

Microscopic Mechanism Study on Carbonation Resistance of Recycled Aggregate Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 1001-1006 ◽  
Author(s):  
Hai Feng Yang ◽  
Zhi Heng Deng ◽  
Xue Liang Li
Keyword(s):  
Fly Ash ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate ◽  
Concrete Carbonation ◽  
Carbonation Resistance

24 100mm × 100mm × 300mm recycled concrete prisms and 96 150mm × 150mm × 150mm cubes are completed in this paper.The relationships of the carbonation depth in each carbonation age with replacement rate of recycled coarse aggregate and fly ash is studied; The SEM is used to observe the interface structure of recycled coarse aggregate concrete and compared with ordinary concrete, and finally,a recycled concrete carbonation model is proposed. The results showed that: the substitution of recycled coarse aggregate and fly ash cut down the recycled concrete carbonation resistance significantly, which are related with the replacement rate; the content of Ca(OH)2 in the recycled aggregate concrete decreased ,also there are obvious interface transition zone between the recycled coarse aggregate and the new cement;obvious cracks and large voids are exist before the recycled aggregate concrete is loaded, which lead directly to lower carbonation resistance of the recycled concrete.

Flexural properties of steel fiber types and reinforcement ratio for high-strength recycled concrete beams

2017 ◽  
Vol 20 (10) ◽  
pp. 1512-1522 ◽  
Author(s):  
Hai-Long Zhang ◽  
Chang-Chun Pei
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Crack Width ◽  
Coarse Aggregate ◽  
Steel Fiber ◽  
High Strength ◽  
Recycled Concrete ◽  
Steel Fibers ◽  
Flexural Properties ◽  
Recycled Coarse Aggregate

This article took fly ash and silica fume as cementing materials to replace part of cement and took recycled coarse aggregate to replace part of gravel to mix plain concrete and studied the flexural properties of the beams with high-strength steel fiber–recycled concrete by changing the types of steel fiber and reinforcement ratio. The results showed that fly ash and silica fume could improve strength and flexural capacity of the recycled concrete beam by filling micro-cracks of recycled coarse aggregate and reduce the development speed of deflection and crack width of the test beam. Steel fibers could significantly slow the development of deflection and crack width of the beams with high-strength recycled concrete, and the difference in end-structure could increase the flexural capacity of the beams in varying degrees. The article put forward theory of improving the bearing capacity of the beam with three kinds of steel fibers by introducing the influence factor of steel fiber end-structure.

scholarly journals Carbonization Durability of Two Generations of Recycled Coarse Aggregate Concrete with Effect of Chloride Ion Corrosion

2020 ◽  
Vol 12 (24) ◽  
pp. 10544
Author(s):  
Chunhong Chen ◽  
Ronggui Liu ◽  
Pinghua Zhu ◽  
Hui Liu ◽  
Xinjie Wang
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Total Porosity ◽  
Recycled Concrete ◽  
Carbonation Depth ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate ◽  
Carbonation Resistance ◽  
Two Generations

Carbonation durability is an important subject for recycled coarse aggregate concrete (RAC) applied to structural concrete. Extensive studies were carried out on the carbonation resistance of RAC under general environmental conditions, but limited researches investigated carbonation resistance when exposed to chloride ion corrosion, which is an essential aspect for reinforced concrete materials to be adopted in real-world applications. This paper presents a study on the carbonation durability of two generations of 100% RAC with the effect of chloride ion corrosion. The quality evolution of recycled concrete coarse aggregate (RCA) with the increasing recycling cycles was analyzed, and carbonation depth, compressive strength and the porosity of RAC were measured before and after chloride ion corrosion. The results show that the effect of chloride ion corrosion negatively affected the carbonation resistance of RAC, and the negative effect was more severe with the increasing recycling cycles of RCA. Chloride ion corrosion led to a decrease in compressive strength, while an increase in carbonation depth and the porosity of RAC. The equation of concrete total porosity and carbonation depth was established, which could effectively judge the deterioration of carbonation resistance of RAC.

scholarly journals Ternary Mixes of Self-Compacting Concrete with Fly Ash and Municipal Solid Waste Incinerator Bottom Ash

2020 ◽  
Vol 11 (1) ◽  
pp. 107
Author(s):  
B. Simões ◽  
P. R. da Silva ◽  
R. V. Silva ◽  
Y. Avila ◽  
J. A. Forero
Keyword(s):  
Fly Ash ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Bottom Ash ◽  
Chloride Diffusion ◽  
Waste Incinerator ◽  
Chloride Diffusion Coefficient ◽  
Municipal Solid Waste Incinerator ◽  
Self Compacting Concrete ◽  
Solid Waste Incinerator

This study aims to evaluate the potential of incorporating fly ash (FA) and municipal solid waste incinerator bottom ash (MIBA) as a partial substitute of cement in the production of self-compacting concrete mixes through an experimental campaign in which four replacement levels (i.e., 10% FA + 20% MIBA, 20% FA + 10% MIBA, 20% FA + 40% MIBA and 40% FA + 20% MIBA, apart from the reference concrete) were considered. Compressive and tensile strengths, Young’s modulus, ultra-sonic pulse velocity, shrinkage, water absorption by immersion, chloride diffusion coefficient and electrical resistivity were evaluated for all concrete mixes. The results showed a considerable decline in both mechanical and durability-related performances of self-compacting concrete with 60% of substitution by MIBA mainly due to the aluminium corrosion chemical reaction. However, workability properties were not significantly affected, exhibiting values similar to those of the control mix.

scholarly journals Study on the Effect of Recycled Coarse Aggregate on the Shrinkage Performance of Green Recycled Concrete

2021 ◽  
Vol 13 (23) ◽  
pp. 13200
Author(s):  
Yang Yu ◽  
Peihan Wang ◽  
Zexin Yu ◽  
Gongbing Yue ◽  
Liang Wang ◽  
...  
Keyword(s):  
Primary Particle ◽  
Coarse Aggregate ◽  
Cementitious Material ◽  
Recycled Concrete ◽  
Low Carbon ◽  
Replacement Ratio ◽  
Recycled Coarse Aggregate ◽  
Shrinkage Property ◽  
Low Carbon Emission

Shrinkage property is a significant indicator of the durability of concrete, and the shrinkage of green recycled concrete is particularly problematic. In this paper, construction waste was crushed and screened to generate simple-crushed recycled coarse aggregate (SCRCA). The SCRCA was then subjected to particle shaping to create primary particle-shaped recycled coarse aggregate (PPRCA). On this basis, the PPRCA was particle-shaped again to obtain the secondary particle-shaped recycled coarse aggregate (SPRCA). Under conditions where the dosage of cementitious material is 300 kg/m3 and the sand rate is 38%, a new high-belite sulphoaluminate cement (HBSAC) with low carbon emission and superior efficiency was used as the basic cementitious material. Taking the quality of recycled coarse aggregate (SCRCA, PPRCA, and SPRCA) and the replacement ratio (25%, 50%, 75%, and 100%) as the influencing factors to prepare the green recycled concrete, the workability and shrinkage property of the prepared concrete were analyzed. The results show that the water consumption of green recycled concrete decreases as the quality of the recycled coarse aggregate (RCA) increases and the replacement ratio decreases, provided that the green recycled concrete achieves the same workability. With the improvement of RCA quality and the decrease of replacement ratio, the shrinkage of recycled concrete decreases. The shrinkage performance of green recycled concrete configured with the SPRCA completely replacing the natural coarse aggregate (NCA) is basically the same as that of the natural aggregate concrete (NAC).

scholarly journals Performance of Recycled Concrete Aggregate in Self Compacting Concrete

2018 ◽  
Vol 7 (3.35) ◽  
pp. 1
Author(s):  
T. V. Arul Prakash ◽  
Dr. M. Natarajan ◽  
Dr. T. Senthil Vadivel ◽  
K. Vivek
Keyword(s):  
Fly Ash ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Self Compacting Concrete ◽  
Fly Ash Concrete ◽  
Local Construction ◽  
Class F Fly Ash ◽  
Strength And Durability

This article presents the influence of the Recycled Concrete Aggregate (RCA) on the mechanical properties of self-compacting fly ash concrete (M30 Grade). The RCA from local construction demolition site were employed as a replacement for natural coarse aggregate (0% - 30%) in self-compacting concrete (SCC). The Viscosity modifying material used in this study was Class F fly ash. The results indicate that recycled concrete aggregate can be replaced by an optimal 25% replacement percentage in the manufacture of SCC without significantly affecting strength and durability.  

scholarly journals Experimental Study on the Concrete with Compound Admixture of Iron Tailings and Slag Powder under Low Cement Clinker System

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Ruidong Wu ◽  
Juanhong Liu
Keyword(s):  
Diffusion Coefficient ◽  
Mineral Admixture ◽  
Chloride Diffusion ◽  
Cement Clinker ◽  
Hydration Reaction ◽  
Chloride Diffusion Coefficient ◽  
Carbonation Depth ◽  
Mixture Ratio ◽  
Slag Powder ◽  
Powder Content

In order to study the performance of concrete with compound admixture of iron tailings and slag powder under low cement clinker system, the mixture ratio of different iron tailings powder and slag powder was designed to prepare C30 and C50 concrete. The workability, strength, carbonation depth, chloride diffusion coefficient, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) of concrete were measured, respectively. The test results show that iron tailings powder is beneficial to improve the workability, and the strength of concrete decreases with the increase of iron tailings powder content, while the carbonation depth and chloride diffusion coefficient increase with the increase of iron tailings powder content. Under low cement clinker system, the iron tailings powder should not be used alone (below 70% of mineral admixture). When the ratio of iron tailings to slag powder is 1 : 1, the strength, carbonation depth, chloride ion permeation coefficient, and the microstructure of concrete are roughly the same to that of concrete with single slag powder. So, the iron tailings powder can replace S95 grade slag powder in the same quantity. Iron tailings powder does not take part in hydration reaction, but it can improve particle gradation, reach close accumulation, and increase the quantity of central grains.

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