Effect of recycled aggregate treatment techniques on the durability of concrete: A comparative evaluation

2020 ◽  
Vol 264 ◽  
pp. 120284 ◽  
Author(s):  
Syed Minhaj Saleem Kazmi ◽  
Muhammad Junaid Munir ◽  
Yu-Fei Wu ◽  
Indubhushan Patnaikuni ◽  
Yingwu Zhou ◽  
...  
Keyword(s):  
Comparative Evaluation ◽  
Recycled Aggregate ◽  
Treatment Techniques ◽  
Durability Of Concrete

scholarly journals Appraisal of Processing Techniques for Recycled Aggregates in Concrete

2019 ◽  
Vol 8 (6) ◽  
pp. 1661-1665 ◽  
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Bacterial Suspension ◽  
Mechanical Method ◽  
Treatment Techniques ◽  
Chemical Admixture ◽  
Surface Permeability ◽  
Natural Aggregates ◽  
Processing Techniques

Due to depletion of natural aggregates the need for the usage of recycled aggregate in concrete has gained significance. In this regard, the present study is an attempt to evaluate the performance of M20 grade of concrete made with 100% recycled aggregate processed using various techniques. Handpicked aggregate from concrete rubble is used to prepare recycled aggregate concrete. The use of chemical admixture is mandatory to compensate the extra water (3 to 6%) required by the RCA (Recycled Aggregates). RCA treated with calcite mineral precipitating bacterial suspension enhances its surface permeability. RCA exposed to different acid concentrations improved the surface of the aggregate with the removal of the loosely adhered mortar. In thermal – mechanical method the recycled aggregates from rubble are heated in microwave to 300°C to remove adhered mortar from the aggregate and placed in a rotating drum containing iron balls. In chemical– mechanical method the recycled aggregate is exposed to Na2So4 and is subjected to freeze-thaw cycles to create mechanical to separate adhered mortar from RCA. In acid soaking beneficiation method the mortar around RCA is removed by immersing them in 5% HCl and H2SO4 for 24 hours. All the above mentioned recycled aggregate processing techniques are however to be tested in full scale to study the efficiency of these treatment techniques. Compressive strength and water absorption capacities of various concrete samples made with recycled aggregate prepared using above discussed processing techniques are evaluated.

Durability of concrete bearing polymer-treated mixed recycled aggregate

2022 ◽  
Vol 315 ◽  
pp. 125781
Author(s):  
P. Velardo ◽  
I.F. Sáez del Bosque ◽  
M.I. Sánchez de Rojas ◽  
N. De Belie ◽  
C. Medina
Keyword(s):  
Recycled Aggregate ◽  
Durability Of Concrete

scholarly journals Stress–Strain Curve and Carbonation Resistance of Recycled Aggregate Concrete after Using Different RCA Treatment Techniques

2021 ◽  
Vol 11 (9) ◽  
pp. 4283
Author(s):  
Long Li ◽  
Dongxing Xuan ◽  
Chisun Poon
Keyword(s):  
Elastic Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Aggregate Concrete ◽  
Treatment Techniques ◽  
Carbonation Resistance

Five recycled coarse aggregate (RCA) treatment techniques including flow-through carbonation, pressurized carbonation, wet carbonation, nano silica (NS) pre-spraying and combined pressurized carbonation with NS pre-spraying, were utilized to improve the performance of recycled aggregate concrete (RAC). The characteristics of the stress–strain curves of RACs including peak stress, peak strain, elastic modulus, ultimate strain and toughness were evaluated after using the above RCA treatment techniques. A theoretical model for natural aggregate concrete was used to analyse the stress–strain curve of RAC. Additionally, the carbonation resistance of RAC after using different RCA treatment techniques were investigated. The results showed that the calculated stress–strain curve of RAC based on the theoretical model matched well with the experimental results. Among the three types of carbonation techniques, pressurized carbonation caused the highest improvement in peak stress and elastic modulus of RAC, followed by flow-through carbonation, the last was wet carbonation. The NS pre-spraying method contributed to even higher improvement in peak stress and elastic modulus of RAC than the pressurized carbonation method. The combined pressurized carbonation with NS pre-spraying exhibited the highest enhancement of RAC because both the RCA and the new interface transition zone (ITZ) were improved. The carbonation resistance of RAC was improved after using all the studied RCA treatment techniques.

Study on Strength and Durability of Concrete Containing Recycled Coarse Aggregate Manufactured with Various Method

2011 ◽  
Vol 287-290 ◽  
pp. 1015-1018 ◽  
Author(s):  
Hong Zhu Quan
Keyword(s):  
Modulus Of Elasticity ◽  
Coarse Aggregate ◽  
Drying Shrinkage ◽  
Recycled Aggregate ◽  
Test Results ◽  
Recycled Coarse Aggregate ◽  
Concrete Mixtures ◽  
Strength And Durability ◽  
Durability Of Concrete

This paper presents the results of experimental study on the effects of adhered mortar content on strengths and durability of concrete. Compressive, tensile and shear strengths, modulus of elasticity, drying shrinkage and carbonation were tested on concrete mixtures with the water cement ratio of 0.43, 0.50 and 0.60 using 3 kinds recycled coarse aggregate and a riversand. The test results of concrete indicated higher compressive, tensile amd shear strengths and higher modulus of elasticity for concrete using recycled corase aggregate with lower adhered mortar content, lower absorption and higher specific gravity. Recycled aggregate with higher adhered mortar content also showed significunt adverse effects on drying shrinkage and carbonation. In conclusion, the upper limit of adhered mortar content of coarse recycled aggregate to keep up the quality of aggregate and concrete equal to natural coarse aggregate and those concrete is considered to be 15%.

Effect of different aggregate treatment techniques on the freeze-thaw and sulfate resistance of recycled aggregate concrete

2020 ◽  
Vol 178 ◽  
pp. 103126 ◽  
Author(s):  
Syed Minhaj Saleem Kazmi ◽  
Muhammad Junaid Munir ◽  
Yu-Fei Wu ◽  
Indubhushan Patnaikuni ◽  
Yingwu Zhou ◽  
...  
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Sulfate Resistance ◽  
Treatment Techniques

scholarly journals Effects of Recycled Aggregate on Concrete Mix and Exposure to Chloride

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Ammar Ben Nakhi ◽  
Jasem M. Alhumoud
Keyword(s):  
Sea Water ◽  
Chloride Concentration ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Chloride Diffusion ◽  
Demolition Waste ◽  
Aggregate Content ◽  
Concrete Mix ◽  
Durability Of Concrete

Construction and demolition waste has dramatically increased in the last decade, and most of it goes into landfills, increasing the burden on landfill loading and operations. Recycling of concrete is needed from the viewpoints of environmental preservation and effective utilization of resources. Regarding the durability of concrete, chloride diffusion, which is one parameter that reflects the durability of concrete, is tested in this study. Concrete made with different percentages of recycled aggregate (0%–100%, with increments of 10%) is investigated using mechanical and nondestructive testing of mixes consisting of two aggregate particle sizes (1/2″ and 3/8″). In addition, we studied the chloride diffusion of saturated concrete made with different percentages of recycled aggregate. The samples were exposed to sea water with 3% chloride concentration and tested after 2 and 4 weeks of exposure. The results indicate that the density and air content of new concrete decreased with an increase in recycled aggregates content. Compressive strength decreased with the increase in the recycled aggregate content, and a concrete mix with 40% recycled aggregate exhibited the best strength. Concrete mix with 30% recycled aggregate had the lowest chloride penetration after 2 weeks of saturation and performed better than a concrete mix with 100% natural aggregate. Owing to the lower density and higher water absorption of recycled aggregates, chloride ion diffusion increased with increasing recycled aggregate content beyond 2 weeks.

Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

1986 ◽  
Vol 51 (4) ◽  
pp. 362-369 ◽  
Author(s):  
Donna M. Risberg ◽  
Robyn M. Cox
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Comparative Evaluation ◽  
Speech Intelligibility ◽  
Hearing Aid ◽  
Hearing Aid Fitting ◽  
The Difference ◽  
Functional Gain ◽  
The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

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