Experimental Research on Pore Structure of RCA and its Impact on Drying Shrinkage

2011 ◽  
Vol 335-336 ◽  
pp. 1141-1144 ◽  
Author(s):  
Yun Xiang He
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Drying Shrinkage ◽  
Recycled Aggregate ◽  
Structure Theory ◽  
Replacement Rate ◽  
Pore Characteristics ◽  
Cement Ratio ◽  
Mix Proportion ◽  
The Impact

Pore structure is one of the main influencing factors of materials drying shrinkage. C30 natural mix proportion is used as reference, the impact of replacement rate of recycled aggregate, the mixing amount of fly ash, water reducer, expansion agent and water-cement ratio on recycled aggregate concrete’s porosity and pore characteristics was studied. Based on the pore structure theory, the influence of porosity and pore characteristics on recycled aggregate concrete’s drying shrinkage is analyzed.

scholarly journals Experimental Research on the Wettability of Recycled Aggregate Concrete with Fly Ash

2013 ◽  
Vol 7 (1) ◽  
pp. 232-236
Author(s):  
Yuanchen Guo ◽  
Xue Wang ◽  
Jueshi Qian
Keyword(s):  
Fly Ash ◽  
Moisture Absorption ◽  
Drying Shrinkage ◽  
Absorption Capacity ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Structure Theory ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Main Factors

Material adsorption, the reverse process of evaporation diffusion, directly reflects the wettability of materials. Wettability is one of the main factors that affect the drying shrinkage of materials. A device that measures the wettability of recycled aggregate concrete (RAC) with fly ash is proposed in this study based on pore structure theory. The isothermal absorption curve of RAC is examined with different fly ash contents. Results show that as the recycled aggregate replacement rate increases, the moisture absorption capacity of RAC gradually increases. The addition of fly ash improves the porosity of RAC structures and reduces material wettability.

Experimental Research on Isothermal Sorption of RAC Material

2011 ◽  
Vol 335-336 ◽  
pp. 1223-1226
Author(s):  
Yuan Chen Guo ◽  
Xue Wang
Keyword(s):  
Drying Shrinkage ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Absorption Curve ◽  
Structure Theory ◽  
Replacement Rate ◽  
Water Contact ◽  
Aggregate Concrete ◽  
Wetting Properties ◽  
Properties Of Materials

Material adsorption process is the reverse process of evaporation diffusion, reflecting directly the wetting degree of material, is one of the main factors of material drying shrinkage. Based on pore structure theory, this article designed a device measuring the wetting properties of materials, tested different recycled aggregate replacement rate recycled aggregate concrete isothermal absorption curve. The article proposes the water contact angle can be calculated from the initial absorption curve, and analyzes its impact on drying shrinkage of recycled aggregate concrete.

Experimental Study on Drying Shrinkage Performance of Solid Concrete Bricks Made from Recycled Coarse Aggregate

2013 ◽  
Vol 753-755 ◽  
pp. 762-770 ◽  
Author(s):  
Xi Xi He ◽  
Tao Zhang
Keyword(s):  
Moisture Content ◽  
Water Absorption ◽  
Coarse Aggregate ◽  
Drying Shrinkage ◽  
Recycled Aggregate ◽  
Test Results ◽  
Replacement Rate ◽  
Recycled Coarse Aggregate ◽  
The Impact ◽  
The Relationship

Solid recycled coarse aggregate concrete bricks were produced by QTY4-40 brick machine with strength grades of MU15-MU30. Recycled aggregate replacement rate was up to 100%. Water absorption and moisture content were tested. Two methods were taken to test the drying shrinkage. The impact of recycled aggregate replacement rate and curing period on the drying shrinkage rate, water absorption, moisture content, density was analyzed, and the relationship between them was presented. The results indicate that recycled aggregate can increase the shrinkage of solid concrete brick. The shrinkage of recycled solid concrete bricks' (fully substitute) is larger than ordinary concrete bricks' by 1.6-2 times. Water reducer is helpful to improve the water retention and decrease the shrinkage of brick. One of the test results of shrinkage got by the methods recommended in relevant specification is smaller.

scholarly journals The Permeability of Waste Fiber Recycled Concrete

2019 ◽  
Vol 26 (2) ◽  
pp. 210-217 ◽  
Author(s):  
Jinghai ZHOU ◽  
Tianbei KANG ◽  
Fengchi WANG
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Gas Permeability ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Cement Ratio

Permeability is one of the major performances for recycled aggregate concrete, which affects the durability and service life of concrete structures. In most cases, the main factor affecting the permeability of recycled aggregate concrete is the pore structure. Considering water-cement ratio, replacement rate of recycled aggregates, waste fiber length, and volume fraction of waste fibers as the design variables, pore structure and gas permeability were studied experimentally. In addition, fractal theory was here used to assess the pore structure of waste fiber recycled concrete and study the effects of pore structure on permeability. The results showed that the pore size distribution had a small impact on the permeability with the water-cement ratio and replacement rate of recycled aggregates increasing. The fractal dimension can be used to describe the complexity of the pore structure quantitatively. There is an obvious linear relationship between fractal dimension and gas permeability. The larger the pore volume fractal dimension, the better the impermeability of waste fiber recycled concrete.

scholarly journals Effect of CaSO4 Incorporation on Pore Structure and Drying Shrinkage of Alkali-Activated Binders

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1673 ◽  
Author(s):  
Hyeongmin Son ◽  
Sol Moi Park ◽  
Joon Ho Seo ◽  
Haeng Ki Lee
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Drying Shrinkage ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
Activated Slag ◽  
Capillary Tension ◽  
Alkali Activated Binders ◽  
Internal Pore Structure ◽  
Alkali Activated

This present study investigates the effects of CaSO4 incorporation on the pore structure and drying shrinkage of alkali-activated slag and fly ash. The slag and fly ash were activated at a 5:5 ratio by weighing with a sodium silicate. Thereafter, 0%, 5%, 10%, and 15% of CaSO4 were incorporated to investigate the changes in phase formation and internal pore structure. X-Ray Diffraction (XRD), thermogravimetry (TG)/derivative thermogravimetry (DTG), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and drying shrinkage tests were carried out to find the correlation between the pore structure and drying shrinkage of the specimens. The results showed that CaSO4 incorporation increased the formation of thenardite, and these phase changes affected the pore structure of the activated fly ash and slag. The increase in the CaSO4 content increased the pore distribution in the mesopore. As a result, the capillary tension and drying shrinkage decreased.

scholarly journals Experimental study on mechanical properties and microstructures of steel fiber-reinforced fly ash-metakaolin geopolymer-recycled concrete

2021 ◽  
Vol 60 (1) ◽  
pp. 578-590
Author(s):  
Zhong Xu ◽  
Zhenpu Huang ◽  
Changjiang Liu ◽  
Xiaowei Deng ◽  
David Hui ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Steel Fiber ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Mix Proportion ◽  
Optimal Mix

Abstract Geopolymer cementitious materials and recycled aggregate are typical representatives of material innovation research in the engineering field. In this study, we experimentally investigated a method to improve the performance of geopolymer-recycled aggregate concrete (GRAC). The recycled concrete aggregates and steel fiber (SF), fly ash (FA), metakaolin (MK), and sodium silicate solution were used as the main raw materials to prepare fiber-reinforced geopolymer-recycled aggregate concrete (FRGRAC). First, the orthogonal test was carried out to study the GRAC, and the optimal mix proportion was found. Second, building on the optimal mix proportion, the effects of the SF content on the slump, 7 and 28 days compressive strength, tensile strength, and flexural strength of FRGRAC were further studied. Finally, the microscopic mechanism of FRGRAC was studied by scanning electron microscopy (SEM). The study results indicate that the slump continues to decrease as the fiber content increases, but the compressive strength, tensile strength, and flexural strength increase to a certain extent. Through SEM analysis, it is found that SF restrains the development of cracks and improves the strength of concrete.

Microscopic Mechanism of the Diffusivity of Concrete Chloride Ion

2013 ◽  
Vol 773 ◽  
pp. 687-692 ◽  
Author(s):  
Jun Liu ◽  
Feng Xing ◽  
Bi Qing Dong
Keyword(s):  
Fly Ash ◽  
Early Stage ◽  
Great Influence ◽  
Chloride Ion ◽  
Test Method ◽  
Mineral Admixture ◽  
Microscopic Mechanism ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
The Impact

Use concrete specimens with different mix proportions to conserve them for 90d taking into account the influence of mineral admixture material---fly ash. Then adopts the RCM test method to measure the rapid diffusivity of chloride ion of concrete and observes the microstructure of the cement paste using the SEM (scanning electron microscopy), aiming to study the impact of fly ash on its hydration process. The results show that the micro-pore structure of the concrete has a great influence on the rapid diffusivity of chloride ion, while its diffusivity is closely related with the water-cement ratio of concrete; after the fly ash is added, the ettringite generation of the concrete in the early stage decreases, and the interspace of the transition zone between the hydrated particles and hydration slurry is enlarged, coupled with the increase in the intercommunicating pore; after curing for 90d, the chloride ion diffusivity decreases significantly with the increase in the dosage of fly ash. For the concrete with the fly ash dosage of 15%, its chloride ion diffusivity is only 75.4% of that with the same water-cement ratio; when its fly ash content is 30%, its chloride ion diffusivity is only 32.3% of the ordinary concrete.

Effect of Admixed Recycled Aggregate on Properties of Recycled Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 743-746
Author(s):  
Ya Jun Zhao ◽  
Ying Gao ◽  
Li Li He
Keyword(s):  
Compressive Strength ◽  
Design Method ◽  
Orthogonal Design ◽  
Plain Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
The Impact

The mixture proportion of recycled concrete was discussed by orthogonal design method. The influence of water-cement ratio, recycled aggregate quantity on workability, cube compressive strength of recycled concrete was analyzed. The experimental results indicated that，Recycled concrete mix proportion design should consider the impact of the water absorption of recycled aggregate. Unit water amount of recycled concrete should be plain concrete unit water consumption and recycled aggregate additional amount of water. Sand ratio should increase in the corresponding ordinary aggregate concrete sand ratio on the basis of 1 to 3 percent. When the water-cement ratio is 0.36 and construction waste content of 40% slag content of 20%, 28d compressive strength of concrete is 48.1MPa, slightly higher than the reference concrete (48.0MPa).

Survey on Factors Affecting Impermeability of Waterproof Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 1320-1323
Author(s):  
Yi Jin Li ◽  
Yun Li Gong ◽  
Jian Yin
Keyword(s):  
Fly Ash ◽  
Ash Content ◽  
Raw Material ◽  
Factors Affecting ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Mix Proportion

This paper describes the influence of raw material, water-cement ratio, sand ratio, cement-sand ratio and fly ash content on impermeability of waterproof concrete. The value ranges of several important mix parameters are summarized, that provides the reference to select the parameters of mix proportion of waterproof concrete for subway.

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