Experimental Study on Frost Resistance Durability of Concrete with Intensified Recycled Aggregates

2011 ◽  
Vol 280 ◽  
pp. 152-158 ◽  
Author(s):  
Wen Ge Chai ◽  
Wen Li Li ◽  
Wen Xia Gao
Keyword(s):  
High Performance ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Recycled Concrete ◽  
Mineral Admixture ◽  
Recycled Aggregates ◽  
High Quality ◽  
Freeze Thaw ◽  
High Efficient ◽  
Resistance Durability

In order to study high performance recycled concrete, the recycled concrete is prepared through the double admixing technology, i.e. mixing of high-quality mineral admixture and high-efficient water reducer. It is modified with the recycled aggregates soaked in and intensified by chemical grouts. The mass loss rate and relative dynamic elastic modulus of the recycled concrete are measured through fast freeze-thaw test, and a model for predicting the life of the recycled concrete under freeze-thaw conditions is built. The experiment results show that it is an efficient way to intensify recycled aggregates through being soaked in chemical grouts. The recycled concrete prepared with recycled aggregates intensified by chemical grouts, high-quality mineral admixture and the high-efficient water reducer feature favorable frost-resistance.

Resistance to the Penetration of Chloride Ions of Concrete with Intensified Recycled Aggregates

2011 ◽  
Vol 71-78 ◽  
pp. 1572-1577
Author(s):  
Wen Ge Chai ◽  
Wen Li Li ◽  
Wen Xia Gao
Keyword(s):  
Chloride Ion ◽  
Chloride Ions ◽  
Recycled Concrete ◽  
Mineral Admixture ◽  
Recycled Aggregates ◽  
Ion Content ◽  
High Quality ◽  
Total Chloride ◽  
High Efficient ◽  
Electric Flux

In order to study on methods for and effect of improving performances of recycled concrete, this paper has adopted the recycled aggregates intensified by dipping in the chemical grout, on which basis, the recycled concrete is prepared through the double admixing technology, i.e. mixing of the high-quality mineral admixture and the high-efficient water reducer. The chloride ion permeability of the recycled concrete is researched in the laboratory. In the test, the electric flux, the total chloride ion content and the free chloride ion content at different depths of the recycled concrete have been obtained. The research has shown that dipping in the chemical grout is an effective way to intensify recycled aggregates and that recycled concrete prepared with the intensified recycled aggregates, high-quality mineral admixture and high-efficient water reducer features favorable permeability resistance.

scholarly journals Additive Modulated Perovskite Microstructures for High Performance Photodetectors

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1090
Author(s):  
Zhan Gao ◽  
Yifan Zheng ◽  
Guancheng Huang ◽  
Genjie Yang ◽  
Xinge Yu ◽  
...  
Keyword(s):  
Molecular Interactions ◽  
Dark Current ◽  
High Performance ◽  
Visible Region ◽  
Carbonyl Groups ◽  
High Quality ◽  
Inorganic Hybrid ◽  
Simple Route ◽  
High Efficient ◽  
Crystallographic Defects

Organic-inorganic hybrid perovskites have been widely used as light sensitive components for high-efficient photodetectors due to their superior optoelectronic properties. However, the unwanted crystallographic defects of perovskites typically result in high dark current, and thus limit the performance of the device. Herein, we introduce a simple route of microstructures control in MAPbI3 perovskites that associates with introducing an additive of 3,3,4,4-benzophenonetetracarboxylic dianhydridean (BPTCD) for crystallization adjustment of the perovskite film. The BPTCD additive can facilitate the formation of high-quality perovskite film with a compact and nearly pinhole-free morphology. Through characterizing the molecular interactions, it was found that the carbonyl groups in BPTCD is the key reason that promoted the nucleation and crystallization of MAPbI3. As a result, we obtained high-efficient and stable perovskite photodetectors with low dark current of 9.98 × 10−8 A at −0.5 V, an on/off ratio value of 103, and a high detectivity exceeding 1012 Jones over the visible region.

Effect of Mica Content in Stone Powder of Manufactured Sand on Performance of Cement Mortar

2014 ◽  
Vol 1044-1045 ◽  
pp. 624-628
Author(s):  
Jie Quan Xing ◽  
Shu Lin Zhan ◽  
Xin Yu Li
Keyword(s):  
Compressive Strength ◽  
Loss Rate ◽  
Cement Mortar ◽  
Mass Loss Rate ◽  
Strength Loss ◽  
Freezing Resistance ◽  
River Sand ◽  
Manufactured Sand ◽  
Freeze Thaw ◽  
Different Content

This paper studies the influence on compressive strength, freezing resistance and microstructure of cement mortar with different content of mica in stone powder, in the tests, manufactured sand with high content of mica and natural river sand were mixed with different proportion, and the content of stone powder was the same in mixed sand. Experiment results indicate that, with the increasing of mica content in stone powder, 28d and 60d compressive strength of cement mortar decreases obvious, mass loss rate and strength loss rate with 50 freeze-thaw cycles increase a little. Microstructure of cement mortar with higher content of mica is not compactly by SEM, the internal defects of cement hardened pastes could be increased because of the flake mica which surface is smooth, and it will cause the spread of micro crack.

Interaction between decomposing litter and soil fauna of the Betula ermanii forest floor of the Changbai Mountains, China

2014 ◽  
Vol 44 (12) ◽  
pp. 1507-1514 ◽  
Author(s):  
Xiaoqiang Li ◽  
Xiuqin Yin ◽  
Zhenhai Wang ◽  
Weihong Fan
Keyword(s):  
Mass Loss ◽  
Forest Floor ◽  
Loss Rate ◽  
Soil Fauna ◽  
Mass Loss Rate ◽  
Changbai Mountains ◽  
Mixed Species ◽  
High Quality ◽  
Litter Mass ◽  
Litter Mass Loss

Soil fauna play a key role in litter decomposition as they influence the litter mass loss rate in terrestrial ecosystems. However, the interaction between decomposing litter and soil fauna has not been adequately addressed. We examine the interaction between different types of decomposing litter and soil fauna on the Betula ermanii Cham. (BE) forest floor of the Changbai Mountains, China, by measuring the mass loss of six litter species groups using litterbags with two sizes of mesh (4 mm and 0.01 mm) during a yearlong experiment. Soil fauna were identified at the order level. We found that soil fauna have a limited effect on litter mass loss at the initial stage of the experiment. Its positive effect became apparent at month 12 of the experiment. After 1 year, soil fauna increased the litter mass loss rate of the high-quality litter of Parasenecio komarovianus (Pojark.) Y.L. Chen (PK) by 7.02% and of the low-quality litter of Rhododendron aureum Georgi (RA) by 25.26%. BE + PK litter was associated with a significantly higher abundance of soil fauna at months 8 and 10 of the experiment and also with a significantly higher richness of soil fauna at month 10 of the experiment. At the end of the experiment, however, the Shannon–Wiener diversity index of soil fauna was not necessarily higher in mixed-species litter. Litter mixing did promote the abundance, richness, and diversity of soil fauna during the warm season in the high-quality litter substrate of BE + PK. Our results illustrate that the impact of soil fauna on the litter mass loss of both single- and mixed-species litterbags ranges from a limited impact to a positive impact as litter mass loss advances. The soil fauna contribute more to the litter mass loss of the low-quality litter with higher C to N ratios than to those with a low C to N ratio. The promoting effect of litter mixing on the soil faunal community composition is only short term and is dependent on substrate quality.

Microstructural Features of Recycled Aggregate Concrete: From Non-Structural to High-Performance Concrete

2019 ◽  
Vol 25 (3) ◽  
pp. 601-616 ◽  
Author(s):  
Diogo Pedro ◽  
Mafalda Guedes ◽  
Jorge de Brito ◽  
Luís Evangelista
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Sequential Approach

AbstractThe use of concrete-recycled aggregates to produce high-performance concrete is limited by insufficient correlation between resulting microstructure and its influence on mechanical performance reproducibility. This work addresses this issue in a sequential approach: concrete microstructure was systematically analyzed and characterized by scanning electron microscopy and results were correlated with concrete compressive strength and water absorption ability. The influence of replacing natural aggregates (NA) with recycled concrete aggregates (RCA), with different source concrete strength levels, of silica fume (SF) addition and of mixing procedure was tested. The results show that the developed microstructure depends on the concrete composition and is conditioned by the distinct nature of NA, recycled aggregates from high-strength source concrete, and recycled aggregates from low-strength source concrete. SF was only effective at concrete densification when a two-stage mixing approach was used. The highest achieved strength in concrete with 100% incorporation of RCA was 97.3 MPa, comparable to that of conventional high-strength concrete with NA. This shows that incorporation of significant amounts of RCA replacing NA in concrete is not only a realistic approach to current environmental goals, but also a viable route for the production of high-performance concrete.

scholarly journals Enhancing the Hardened Properties of Recycled Concrete (RC) through Synergistic Incorporation of Fiber Reinforcement and Silica Fume

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4112 ◽  
Author(s):  
Babar Ali ◽  
Hawreen Ahmed ◽  
Liaqat Ali Qureshi ◽  
Rawaz Kurda ◽  
Hisham Hafez ◽  
...  
Keyword(s):  
Glass Fiber ◽  
Silica Fume ◽  
High Performance ◽  
Synergistic Effects ◽  
Fiber Reinforcement ◽  
Recycled Concrete ◽  
Mineral Admixture ◽  
Portland Cement Concrete ◽  
Positive Role ◽  
Hardened Properties

Portland cement concrete is fragile in tension and it has numerous negative impacts on the environment. To deal with these issues, both fiber reinforcement and recycled materials can be utilized to manufacture sustainable and ductile concrete. In this study, the synergistic effects of high-performance mineral admixture silica fume and glass fiber reinforcement were investigated on the hardened properties of RC. For this purpose, two concrete mix families, namely, NC and RC were prepared. To understand the benefits of synergistic utilization of glass fiber and silica fume, in both NC and RC, 0.5% glass fiber was incorporated with three different levels of silica fume. i.e., 0%, 5%, and 10%. Both strength and permeability-related durability properties were investigated. Results revealed that combined incorporation of 0.5% fiber and 10% silica fume can help in the production of RC having better mechanical and durability performance compared to reference “NC”. Simultaneous incorporation of silica fume and glass fiber produces a combined effect greater than their individual effects on both mechanical and permeability properties of concrete. Silica fume plays a very dominant and positive role in the development of CS, WA, and CIPR of RC, whereas glass fiber plays a vital role in upgrading STS and FS of RC and whereas, with the addition of 0.5% glass fiber, RC can yield 8–9 times higher flexural toughness than that of the plain NC.

scholarly journals Bond Behavior of Recycled Fiber Recycled Concrete with Reinforcement after Freeze-Thaw Cycles

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1506
Author(s):  
Yu Liu ◽  
Jinghai Zhou ◽  
Di Wu ◽  
Tianbei Kang ◽  
Aixia Liu
Keyword(s):  
Bond Strength ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Building Structures ◽  
Two Phase ◽  
Bond Behavior ◽  
Freeze Thaw ◽  
Pull Out ◽  
Recycled Fiber ◽  
Recycled Fibers

Freeze-thaw (F-T) damage is the major factor destroying the bond behavior of reinforced concrete in the cold areas of China. The bond behavior between recycled fiber recycled concrete (RFRC) and reinforcement after F-T cycles was investigated in this paper. The pull-out tests were undertaken with the replacement rate (0, 50%, and 100%) of recycled aggregates (RA) and volume content (0, 0.12%, and 0.24%) of recycled fibers (RFs) as test variables. The results demonstrate that the F-T cycles will reduce the bond strength between RFRC and reinforcement. Bond strength decreases by 69.41% after 150 cycles. Moreover, RF can improve the bond strength between RFRC and reinforcing steel. Bonding strength increases by 11.35% with the addition of 0.12% RF. A simplified two-phase bond-slip model between RFRC and reinforced steel after F-T cycles was eventually established, and it correlated well with the experimental results. This research presents a theoretical basis for the application of RFRC in building structures in cold areas.

scholarly journals Experimental Investigation on the Freeze–Thaw Resistance of Steel Fibers Reinforced Rubber Concrete

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1260
Author(s):  
Tao Luo ◽  
Chi Zhang ◽  
Chaowei Sun ◽  
Xinchao Zheng ◽  
Yanjun Ji ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Mass Loss ◽  
Loss Rate ◽  
Bending Strength ◽  
Mass Loss Rate ◽  
Steel Fibers ◽  
Freeze Thaw ◽  
Four Point Bending ◽  
Rubber Concrete

The reuse of rubber in concrete results in two major opposing effects: an enhancement in durability and a reduction in mechanical strength. In order to strengthen the mechanical properties of rubber concrete, steel fibers were added in this research. The compressive strength, the four-point bending strength, the mass loss rate, and the relative dynamic elastic modulus of steel fiber reinforced rubber concrete, subjected to cyclic freezing and thawing, were tested. The effects of the content of steel fibers on the freeze–thaw resistance are discussed. The microstructure damage was captured and analyzed by Industrial Computed Tomography (ICT) scanning. Results show that the addition of 2.0% steel fibers can increase the compressive strength of rubber concrete by 26.6% if there is no freeze–thaw effect, but the strengthening effect disappears when subjected to cyclic freeze–thaw. The enhancement of steel fibers on the four-point bending strength is effective under cyclic freeze–thaw. The effect of steel fibers is positive on the mass loss rate but negative on the relative dynamic elastic modulus.

scholarly journals Recycling Aggregates for Self-Compacting Concrete Production: A Feasible Option

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 868 ◽  
Author(s):  
Rebeca Martínez-García ◽  
M. Ignacio Guerra-Romero ◽  
Julia M. Morán-del Pozo ◽  
Jorge de Brito ◽  
Andrés Juan-Valdés
Keyword(s):  
High Performance ◽  
Physical And Mechanical Properties ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Structural Elements ◽  
The European Union ◽  
Self Compacting Concrete ◽  
Concrete Production ◽  
Complex Structural

The use of construction and demolition wastes (C&DW) is a trending future option for the sustainability of construction. In this context, a number of works deal with the use of recycled concrete aggregates to produce concrete for structural and non-structural purposes. Nowadays, an important number of C&DW management plants in the European Union (EU) and other countries have developed robust protocols to obtain high-quality coarse recycled aggregates that comply with different European standards in order to be used to produce new concrete. The development of self-compacting concrete (SCC) is another way to boost the sustainability of construction, due to the important reduction of energy employed. Using recycled aggregates is a relatively recent scientific area, however, studies on this material in the manufacture of self-compacting concrete have proven the feasibility thereof for conventional structural elements as well as high-performance and complex structural elements, densely reinforced structures, difficult-to-access formwork and difficult-to-vibrate elements. This paper presents an original study on the use of coarse recycled concrete aggregate (CRA) to obtain self-compacting concrete. Concrete with substitution ratios of 20%, 50% and 100% are compared with a control concrete. The purpose of this comparison is to check the influence of CRA on fresh SCC as well as its physical and mechanical properties. The parameters studied are material characterization, self-compactability, compressive strength, and tensile and flexural strength of the resulting concrete. The results conclude that it is feasible to use CRA for SCC production with minimal losses in the characteristics.

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