scholarly journals Partially fly ash and nano-silica incorporated recycled coarse aggregate based concrete: Constitutive model and enhancement mechanism

2022 ◽  
Author(s):  
Wanhui Feng ◽  
Yunchao Tang ◽  
Yunqi Zhang ◽  
Changhui Qi ◽  
Liangyi Ma ◽  
...  
Keyword(s):  
Fly Ash ◽  
Constitutive Model ◽  
Coarse Aggregate ◽  
Nano Silica ◽  
Enhancement Mechanism ◽  
Recycled Coarse Aggregate

scholarly journals Strength and abrasion performance of recycled aggregate based geopolymer concrete

2021 ◽  
Author(s):  
Asfaw Mekonnen LAKEW ◽  
Mukhallad M. AL-MASHHADANI ◽  
Orhan CANPOLAT
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Coarse Aggregate ◽  
Steel Fiber ◽  
Splitting Tensile Strength ◽  
Partial Replacement ◽  
Geopolymer Concrete ◽  
Recycled Coarse Aggregate ◽  
One Year

This experimental work evaluated geopolymer concrete containing fly ash and slag by partial replacement of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) to manufacture environmental-friendly concrete. The proportion of recycled aggregates considered consists of 10%, 20%, 30%, and 40% of the total coarse aggregate amount. Also, a steel fiber ratio of 0.3% was utilized. The mechanical properties and abrasion resistance of fly ash/slag-based geopolymer concrete were then assessed. Majorly, the mechanical strength of the concrete samples decreased by the increase of RCA content. The geopolymer concrete with 40% RCA gave 28.3% lesser compressive strength and 24% lower splitting tensile strength than NCA concrete at one year. Also, the flexural strength of concrete specimens was reduced by 35% (from 5.34MPa to 3.5MPa) with the incorporation of 40% RCA. The incorporation of 30% RCA caused 23% and 22.6% reduction in compressive strength at 56 days and one year, respectively. The flexural and splitting tensile strength of the specimens was not significantly reduced (less than 10%) with the inclusion of a recycled coarse aggregate ratio of up to 30%. Furthermore, the abrasion wear thickness of every concrete sample was less than 1mm. RCA inclusion of 20% produced either insignificant reduction or better strength results compared to reference mixtures. As a result, it was considered that the combination of 0.3% steel fiber and 20% recycled coarse aggregate in fly ash/slag-based geopolymer concrete leads to an eco-friendly concrete mix with acceptable short and long-term engineering properties that would lead to sustainability in concrete production and utilization sector.

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.

Granular effect of fly ash repairs damage of recycled coarse aggregate

2008 ◽  
Vol 13 (2) ◽  
pp. 177-180 ◽  
Author(s):  
Jiu-su Li ◽  
Han-ning Xiao ◽  
Jian-qing Gong
Keyword(s):  
Fly Ash ◽  
Coarse Aggregate ◽  
Recycled Coarse Aggregate

scholarly journals Studying the C–H Crystals and Mechanical Properties of Sustainable Concrete Containing Recycled Coarse Aggregate with Used Nano-Silica

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 122
Author(s):  
Shahriar Shahbazpanahi ◽  
Moslem Khalili Tajara ◽  
Rabar H. Faraj ◽  
Amir Mosavi
Keyword(s):  
Mechanical Properties ◽  
Coarse Aggregate ◽  
Recycled Aggregate ◽  
Control Group ◽  
Nano Silica ◽  
Sustainable Concrete ◽  
Recycled Coarse Aggregate ◽  
The Third ◽  
Group Water ◽  
Control Samples

The present study aims to replace 30%, 40%, and 50% of the natural coarse aggregate (NCA) of concrete with recycled coarse aggregate containing used nano-silica (RCA-UNS) to produce a new sustainable concrete. Three groups of concrete are made and their mechanical properties and microstructure are studied. In the first group, which was the control group, normal concrete was used. In the second group, 30%, 40%, and 50% of the NCA were replaced with coarse aggregate obtained from crushed concrete of the control samples and with 0.5% nano-silica as filler. In the third group, 30%, 40%, and 50% of the concrete samples’ NCA were replaced with aggregates obtained from 90-day crushed samples of the second group. Water absorption, fresh concrete slump, and compressive strength of the three groups were investigated and compared through scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) tests. The results show that the third group’s compressive strengths increased by 12.8%, 10.9%, and 10% with replacing 30%, 40%, and 50% of NAC with RCA-NS at 28 days compared to the control samples, respectively. This could be due to the secondary production of calcium silicate hydrate due to the presence of new cement paste. The third group’s microstructure was also improved due to the change in the C–H and the production of extra C–S–H. Therefore, the hydration of cement with water produces C–H crystals while reactions are induced by recycled aggregate containing used nano-silica.

scholarly journals Development of Self Curing Geopolymer Concrete Incorporating Expanded Polystyrene, Recycled Coarse Aggregate and Rubber Crumbs

2020 ◽  
Vol 9 (2) ◽  
pp. 292-296
Keyword(s):  
Fly Ash ◽  
Industrial Waste ◽  
Coarse Aggregate ◽  
Expanded Polystyrene ◽  
Waste Materials ◽  
Environmental Concerns ◽  
Geopolymer Concrete ◽  
Sustainable Building ◽  
Pond Ash ◽  
Recycled Coarse Aggregate

Sustainable building production includes the effective usage of natural materials by the processing of waste materials. The present work aims to use different waste materials, such as fly ash, industrial waste pond ash, rubber crumbs from rubber tires, recycled coarse aggregate from building waste. In doing so, the goal of reducing building costs will be achieved and can help to solve the issues connected with its disposal, particularly the environmental concerns of the area. Throughout this project, Rubber Crumbs (RC) and Recycled Coarse Aggregate (RCA) were partly substituted instead of coarse aggregate with a percentage of 10, 15, 20, and 5, 10, 15, which were found to improve the flexural strength of concrete. Such products may also be used for renewable building purposes.

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