Effectiveness of Using Recycled Coarse Aggregate in Concrete (original) (raw)
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Use of plant aggregates in building ecomaterials
European Journal of Environmental and Civil Engineering, 2012
The aim of this paper is to compare hemp shiv and sunflower pith properties when they are used as plant aggregates incorporated into a pozzolanic matrix. Scanning electron microscope observation of these aggregates showed distinct microstructures, which could be responsible for the differences in mechanical and thermal behaviour observed between composites including these two types of plant aggregates. The long-term behaviour of composites revealed the mineralization of plant aggregates, in particular hemp shiv, by calcium compounds. L'objectif de cet article est de comparer les propriétés de la chènevotte du chanvre et de la moelle de tournesol dans le cadre de leur valorisation en tant que granulats végétaux associés à une matrice pouzzolanique. L'observation par microscopie électronique à balayage de ces granulats a permis de mettre en évidence leurs microstructures distinctes. Ceci expliquerait les écarts de comportement mécanique et thermique des composites incorporant ces granulats végétaux. Concernant le comportement a long terme des composites, les résultats mettent en évidence la minéralisation des particules et en particulier de la chènevotte par des composés de nature calcique.
The growing concern for the environment all over the world, as well as the high cost of Portland cement has placed limitation on its use as the sole binding material in concrete. This work has shown that ashes from some agricultural or other biogenic wastes when mixed with appropriate amounts of ordinary Portland cement (OPC) can be used as low-cost, environmentally, more friendly binders for concrete production, than using OPC alone. Experimental determination of requisite properties of the ashes of rice husk, coconut husk, palm leaf, bamboo leaf and peanut shell revealed that they satisfy the essential requirements for pozzolans. Further experimental work was carried out on OPC/rice husk ash (RHA) and OPC/coconut husk ash (CHA) concretes to determine their essential properties in fresh and hardened states. Although the initial and final setting times of OPC/RHA and OPC/CHA pastes were longer than the setting times of 100% OPC paste, they are all within the limits specified by relevant standards. The workability of fresh concrete produced by partially replacing OPC with either of RHA and CHA was found to be better than with 100% OPC. It was also shown that the porosity of OPC/RHA and OPC/CHA concretes was less than the porosity of OPC concrete. Strength tests using very finely ground RHA and CHA to partially replace Portland cement in concrete production showed that at up to 15% replacement the strength activity index of each of them is greater than 100%, which indicating that they are excellent pozzolans. 527 sieve size 45 µm had compressive strength higher than its control which had 100% Portland cement as the binder.
A Review of Agro-waste Materials as Partial Replacement of Fine Aggregate in Concrete
An immense amount of agricultural waste is produced while growing, harvesting and processing goods; which should be treated as a resource for its prevalence and renewability. While developed countries are concerned with utilization and environmental issues, developing countries are focusing on the economic factors of social housing, especially in rural areas. Fortunately, environmental awareness has been raised in the construction industry by using agricultural waste as partial replacement for fine aggregate, coarse aggregate, reinforcing materials, cement and binders. This review is an attempt to collect world-wide data with references for future estimation possibilities of agro waste application focused on fine aggregate replacement in concrete.
Journal of Agricultural and Environmental Ethics, 2019
In an increasingly urbanized world, construction industry is called upon to serve the needs of human society, such as environmental protection and safety in terms of infrastructure. In this context, a sustainable and ethical development means a close connection between buildings and environment. This connection can be achieved through, for example, the concept of ecological concrete or green concrete, as it is often called. The conventional process of obtaining cement and mineral aggregates from the concrete composition generates pollution, especially through greenhouse gas emissions. Also, one should not ignore the fact that extraction of the raw materials affects the habitats of the sites and of the neighboring areas. When construction materials are questioned, the ethical issues lay not in the means of expression, but mainly in the means of production. More to the point, the present contribution aimed to find solutions for enhancing the adhesion of vegetal aggregates with the cement matrix, in order to obtain a material with optimal mechanical properties, which is valued as an ethical approach of building industry. Results showed that plant aggregates can be used to obtain a building material which can be improved by using partial substitution of cement by silica fume, fly ash, or by using additives (sodium silicate and air entraining additive) and that green concrete as an environmentally friendly material offers the alternative for lower energy use and fewer CO 2 emissions. Marketers must understand not only the advantages of these green materials, but also that they have an ethical commitment to provide consumers with environmentally friendly materials.
Agricultural wastes as aggregate in concrete mixtures – A review
Construction and Building Materials, 2014
Concrete is the most widely used construction material. With the ever-increasing industrialization and urbanization, huge amounts of natural resources are required to make concrete. This, in turn, means that large volumes of natural resources and raw materials are being used for concrete production around the world. To eliminate or minimize the negative environmental impact of the concrete industry and promote environmental sustainability of the industry, the use of wastes from industry as materials for concrete making is considered as an alternative solution for preventing the excessive usage of raw materials. The wide availability of agricultural wastes make them a suitable and dependable alternative for aggregate in concrete, wherever available. This paper reviews the possible use of agricultural wastes as aggregate in the concrete industry. It aims to promote the idea of using these wastes by elaborating upon their engineering properties. This summary of existing knowledge about the successful use of agricultural wastes in the concrete industry helps to identify other existing waste products for use in concrete making. From this identification by agricultural and civil engineers, significant achievements can be attained. © 2013 Elsevier Ltd. All rights reserved. http://www.sciencedirect.com/science/article/pii/S0950061813011070
Comparative LCA of concrete with natural and recycled coarse aggregate in the New York City area
The International Journal of Life Cycle Assessment
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Journal of Advanced Concrete Technology
Plant concretes were developed and are currently used as filling material in a timber frame. Their properties are strongly related to the bio-aggregates characteristics. In addition, since hemp shiv, the reference bio-based aggregate, has a limited availability, it is necessary to consider alternative bio-aggregates largely and locally available. Thus, this paper focused on identifying and understanding mechanisms of interaction between different bio-aggregates and mineral binders. To address this issue, the first objective was to determine the properties of five hemp shives and two alternative bioaggregates for vegetal lightweight concrete: corn and sunflower bark particles. The study of the chemical interactions between bio-aggregates and a pozzolanic binder was conducted on model pastes mixed with filtered solutions containing bio-aggregates extractives. The mechanical properties of the paste, as well as their hydration and their mineralogical evolution were studied. In the last part, the mechanical behavior of vegetal concretes was assessed. The results highlight a strong relation between the mechanical behavior of pastes and concretes and the extractive content of the different tested bio-aggregates. Finally, pastes appeared as a relatively good model to predict the behavior of concretes by following their early age performances: setting delay and 3-day mechanical strength.
Using recycled aggregates in green roof substrates for plant diversity
Ecological Engineering, 2015
A B S T R A C T Extensive green roofs are becoming a popular tool for restoring green infrastructure in urban areas, particularly biodiverse habitats such as post-industrial/brownfield sites. This study investigated the use of six recycled lightweight aggregates and combinations of them in green roof growing substrate, to determine their effectiveness for enhancing plant abundance and species diversity. In two separate experiments, we examined the roles of substrate type and depth on the establishment of a perennial wildflower mix over a 15-month period. We found that some of the alternative substrates are comparable to the widely used crushed red brick aggregate (predominantly found in commercial green roof growing substrate) for supporting plant establishment. For some materials such as clay pellets, there was increased plant coverage and a higher number of plant species than in any other substrate. Substrates that were produced from a blend of two or three aggregate types also supported higher plant abundance and diversity. Generally, increasing substrate depth improved plant establishment, however this effect was not consistent across substrates. We conclude that recycled materials may be viable constituents of growing substrate for green roofs and they may improve green roof resilience, through increased plant cover and diversity. The results could provide evidence to support the construction of mosaic habitat types on single roofs using various substrate blends.
Cost and Quality Analysis of Bio-Deposited Recycled Aggregates Concrete
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
Internationally, the utilization of concrete particularly high-strength concrete has been increasing day-by-day due to rapid industrialization and infrastructural developments. An enormous quantity of natural coarse aggregate is required for making concrete to meet the huge demand. Construction activities mainly depend on natural resources as a source of raw materials, leading to ecological imbalance & the natural resources of coarse aggregate are depleting rapidly all over the world and urgently need to be conserved. On the other hand, millions of tonnes of construction and demolition (C&D) wastes are being generated from different sources. So far the disposal of these huge quantity of (C&D) waste is posing a big problem to the local administration & environment. In this study, recycled aggregates were collected from a 20-30 year old demolished building at the university and recycled into fractions of 1.20 mm~2.45mm and 10 mm~20 mm and replaced for both fine aggregates and coarse aggregates. In this study, by surface treatments on coarse fractions of recycled aggregates were treated by microbes, and the properties of the RAC were studied with the combination of both surface-treated recycled coarse aggregates and untreated recycled fine aggregates.