scholarly journals Effect of Mortar Reduction in Recycled Aggregates Used in Concrete

2017 ◽  
Vol 11 (1) ◽  
pp. 363-370 ◽  
Author(s):  
Viviana Letelier ◽  
Ester Tarela ◽  
Pedro Muñoz
Keyword(s):  
Environmental Concern ◽  
Recycled Concrete ◽  
Raw Material ◽  
Recycled Aggregates ◽  
Structural Concrete ◽  
Mechanical Abrasion ◽  
Coarse Aggregates ◽  
Global Environmental ◽  
Material Reuse ◽  
Global Environmental Concern

Background:Following a global environmental concern, concrete manufactured with recycled materials has been widely studied. The reuse of concrete as raw material can reduce the amount of debris and the amount of natural resources needed minimizing the environmental impact.Objective:One of the fundamental issues when using recycled aggregates is the mortar that remains adhered to their surfaces. The effect of this adhered mortar on aggregates, obtained from pavement demolition debris, used in recycled concrete is studied.Method:A mechanical abrasion process is used to reduce the amount of mortar in different degrees from the recycled aggregates that will be used to replace a 40 % of natural coarse aggregates in structural concrete. The mechanical behavior is studied through the compressive and flexural strength of the material and compared with the values obtained for a control concrete, with no recycled aggregates.Results:The abrasion process is proven to be effective eliminating the adhered mortar to the aggregates and the results show that a medium abrasion level, around 200rev, improves significantly the mechanical properties of the recycled concrete, increasing its compressive strength.Conclusion:The percentage of recycled aggregates used in structural concrete can be increased if these are treated with simple mechanical abrasion. The residuals of the eliminated mortar can be also reused as cement replacement, maximizing the material reuse.

scholarly journals A Review of Cardiovascular Toxicity of Microcystins

Toxins ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 507 ◽  
Author(s):  
Linghui Cao ◽  
Isaac Yaw Massey ◽  
Hai Feng ◽  
Fei Yang
Keyword(s):  
Cardiovascular Health ◽  
Environmental Concern ◽  
Current Knowledge ◽  
Public Health Problem ◽  
Cyanobacterial Blooms ◽  
Major Public Health Problem ◽  
Cardiovascular Toxicity ◽  
Secondary Products ◽  
Global Environmental ◽  
Global Environmental Concern

The mortality rate of cardiovascular diseases (CVD) in China is on the rise. The increasing burden of CVD in China has become a major public health problem. Cyanobacterial blooms have been recently considered a global environmental concern. Microcystins (MCs) are the secondary products of cyanobacteria metabolism and the most harmful cyanotoxin found in water bodies. Recent studies provide strong evidence of positive associations between MC exposure and cardiotoxicity, representing a threat to human cardiovascular health. This review focuses on the effects of MCs on the cardiovascular system and provides some evidence that CVD could be induced by MCs. We summarized the current knowledge of the cardiovascular toxicity of MCs, with regard to direct cardiovascular toxicity and indirect cardiovascular toxicity. Toxicity of MCs is mainly governed by the increasing level of reactive oxygen species (ROS), oxidative stress in mitochondria and endoplasmic reticulum, the inhibition activities of serine/threonine protein phosphatase 1 (PP1) and 2A (PP2A) and the destruction of cytoskeletons, which finally induce the occurrence of CVD. To protect human health from the threat of MCs, this paper also puts forward some directions for further research.

scholarly journals Microstructural analysis of concretes manufactured with recycled coarse aggregates pre-soaked using different methods

2020 ◽  
Vol 70 (339) ◽  
pp. 228 ◽  
Author(s):  
Z. Sánchez-Roldán ◽  
I. Valverde-Palacios ◽  
I. Valverde-Espinosa ◽  
M. Martín-Morales
Keyword(s):  
Microstructural Analysis ◽  
Treatment Method ◽  
Absorption Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Negative Effects ◽  
Optimal Method ◽  
Transition Zones ◽  
Coarse Aggregates

Recycled concrete has a microstructure more complex than natural concrete, as it includes new interfacial transition zones, the quality of which is conditioned by the state of humidity of the aggregates used, which in turn will affect the final properties of the concrete. Bearing in mind the greater absorption capacity of recycled aggregates, it is important to improve its properties by means of a treatment method that is capable of reducing the negative effects that this may produce in the new concrete. Therefore, the influence of the pre-soaking method of recycled aggregates on the formation of the microstructure of concretes manufactured with these aggregates is analysed, to determine which treatment is the most effective for the production of concretes for non-structural use. The results show that the microstructure of the evaluated concretes differs according to the treatment method used, the most optimal method being one that uses aggregates without pre-soaking.

Nature-based climate solutions to grow globally

2019 ◽  
Keyword(s):  
Environmental Concern ◽  
Biodiversity Loss ◽  
Environmental Risks ◽  
Transformative Change ◽  
Due Diligence ◽  
Content Type ◽  
Critical Thresholds ◽  
Global Environmental ◽  
Data Gaps ◽  
Global Environmental Concern

Subject Biodiversity and climate change. Significance The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) has reported that 1 million animal and plant species face extinction and that many ecosystems are moving closer to critical thresholds, describing the rate of global change in nature as "unprecedented in human history". The report calls for "transformative change" in economic and social structures that drive biodiversity loss. As in other areas of global environmental concern, improving biodiversity action is increasingly seen not just as a matter for states, but also as a challenge for the private sector, subnational actors and the international financial system. Impacts Companies will face increased pressure to widen due diligence requirements to include environmental risks. Data gaps on quantifying the value and impact of biodiversity at a localised level will continue to limit policy mainstreaming. Efforts to increase biodiversity finance flows will look to mirror the example of climate finance.

Structural behavior of recycled aggregates concrete filled steel tubular columns

2017 ◽  
Vol 8 (1) ◽  
pp. 17 ◽  
Author(s):  
Boshra Eltaly ◽  
Ahmed Bembawy ◽  
Nageh Meleka ◽  
Kameel Kandil
Keyword(s):  
Finite Element ◽  
Steel Tube ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Experimental Program ◽  
Element Analysis ◽  
Finite Element Program ◽  
Tubular Columns ◽  
Coarse Aggregates ◽  
Element Program

This paper presents an experimental and numerical investigation to determine the behavior of steel tubular columns filled with recycled aggregates concrete up to failure under constant axial compression loads. The experimental program included two steel tube columns, four recycled concrete columns and eight composite columns filled with different types of recycled coarse aggregates (granite and ceramic). Different percentages of recycled coarse aggregates: 0, 25 and 50 of the percentage of the coarse aggregates (dolomite) were used. The results of the numerical model that was employed by the finite element program, ANSYS, were compared with the experimental results. The results of the experimental study and the finite element analysis were compared with the design equations using different national building codes: AISC1999, AISC2005 and EC4. The results indicated that the recycled aggregates concrete infill columns have slightly lower but comparable ultimate capacities compared with the specimens filled with normal concrete.

The Southern Ocean Sanctuary and the Evolution of International Environmental Law

2000 ◽  
Vol 15 (3) ◽  
pp. 293-316 ◽  
Author(s):  
Alexander Gillespie
Keyword(s):  
Southern Ocean ◽  
Environmental Concern ◽  
Environmental Law ◽  
International Community ◽  
Vienna Convention ◽  
Statutory Interpretation ◽  
International Environmental Law ◽  
International Whaling Commission ◽  
Global Environmental ◽  
Global Environmental Concern

AbstractThe legality of the Southern Ocean Sanctuary has been a matter of debate. This paper seeks to explain the Sanctuary as being both legal and illustrative of the development of international environmental law within a new, evolutionary framework. A teleological approach to statutory interpretation could construe the Convention in ways that are supportive of the non-lethal utilisation of cetaceans. Such an interpretation may be supported under the Vienna Convention, whereby if examples of previous practice demonstrating different interpretations of the language in question can be shown, then this practice is evidence that a different interpretation of the convention in question is legitimate. This has been the case with the International Whaling Commission. The paper concludes that the Southern Ocean Sanctuary may be regarded as being both a legal and authoritative example of the way in which the majority of the international community has viewed one area of global environmental concern.

New Concrete with Recycled Aggregates from Leftover Concrete

2015 ◽  
Vol 754-755 ◽  
pp. 389-394
Author(s):  
Ofelia Corbu ◽  
Attila Puskás ◽  
Andrei Victor Sandu ◽  
Adrian M. Ioani ◽  
Kamarudin Hussin ◽  
...  
Keyword(s):  
Concrete Strength ◽  
Ecological Impact ◽  
Experimental Tests ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
River Sand ◽  
Coarse Aggregates ◽  
Concrete Type ◽  
Natural Aggregates

We live in an era where people should be more aware of pollution and its consequences. The present paper reveals a way protecting the environment while producing high quality concrete. What make this type of concrete environmentally friendly are the recycled aggregates in the concrete composition amongst with eliminating the ecological impact by saving large amounts of natural aggregates resources. Recycling concrete comes with many other advantages that lead to waste reduction, economy in waste transportation and storage taxes, which are becoming increasingly expensive. This research is based on mix design and experimental tests carried out on C20/25 strength class concrete with uncontaminated leftover concrete aggregates (LCAgg). It reveals favorable results in order to militate for recycled concrete aggregate uses in regular concrete strength classes respectively for common structural elements, mainly for slabs. River sand (0/4 mm) and coarse aggregates (4/8 mm and 8/16 mm): natural sources or recycled concrete type-alternatively used in several mixes-were utilized in concrete mixes.

scholarly journals A Systematic Review On Consumer Behavior toward Plastic Consumption In Asian Countries

2021 ◽  
Vol 7 (1) ◽  
pp. 150
Author(s):  
Nur Syafiqah Khalisah Jallaludin ◽  
Nor Shafieqa Sukarno ◽  
Siti Nur Baiyah Md Nasir ◽  
Nur Ain Ismail ◽  
Nur Aishah Amir Shah ◽  
...  
Keyword(s):  
Environmental Concern ◽  
Environmental Conservation ◽  
The Body ◽  
Asian Countries ◽  
Consumption Behavior ◽  
Conservation Policies ◽  
Body Of Knowledge ◽  
Global Environmental ◽  
Research Designs ◽  
Global Environmental Concern

The consumer’s consumption of plastic continues to increase and has contributed to the global environmental concern, even though certain new environmental conservation policies or laws have been adopted and enforced. However, there were still insufficient studies that systematically review the existing literature on consumers in Asian Countries. Hence the present article conducted a systematic literature review on the plastic consumption behavior and the effect of plastic use by the customers. The present study joined multiple research designs and the review was based on the publication standard. (Reporting standards for systematic evidence syntheses).  This study selected articles using two leading databases namely Scopus and Science Direct. Based on the thematic analysis, this review has three main themes namely 1) action to reduce plastic consumption; 2) waste management 3) impact of plastic on the ecosystem. The three main themes have further produced 11 sub-themes. The study offered several significant contributions for practical purposes and the body of knowledge. The findings explained the importance of integrating consumer awareness and knowledge into consumer plastic consumption, 1) to encourage respect for knowledge and the role played by the consumer on the usage of plastic consumption policy; 2) to strategize an adaptation plan that is in line with the needs, abilities, and intention to use plastic; and 3) to inform on effect on the ecosystem to the specific areas and content of researches that should be the focus of the future studies.

Overcoming the limitations of recycled concrete aggregates in Belgium

2021 ◽  
Author(s):  
Talina Zeidan ◽  
Xavier Farina
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Structural Concrete ◽  
Environmental Aspect ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Walloon Region ◽  
Ready Mix Concrete

<p>In Belgium, the presence of numerous quarries in the Walloon region makes recycled concrete aggregates (RCA) less attractive for structural concrete applications: since the natural aggregates are at reach, it is unprofitable from both a financial and an environmental aspect to use RCA. In addition, the supply of recycled aggregates on the Belgian market is lacking. Only a few recyclers produce type A+ RCA, which could be used in ready-mix concrete, but tend to keep them for their own productions. Furthermore, although the revised Belgian national concrete standard (NBN B 15- 001) allows cast-in-situ concrete to contain higher fractions of recycled aggregates, there is presently no concrete supplier yet certified to produce concrete with recycled aggregates. One should finally note the lack of stimulation or even mandatory incentives by the Authorities to promote the use of RCA. The aim of this paper is to identify the various reasons behind RCA limitations in Belgium and to suggest solutions to overcome them.</p>

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