Life Cycle Assessment Of Concrete Research Articles

Life Cycle Assessment of Concrete Using Copper Slag as a Partial Cement Substitute in Reinforced Concrete Buildings

Cement, one of the main components of concrete, poses environmental risks, accounting for 7% of total global carbon emissions. To alleviate the environmental hazards related to cement manufacturing, supplementary cementitious materials (SCM) are employed to reduce the usage of cement in concrete. One SCM used is copper slag (CS). In this study, a life cycle assessment (LCA) is conducted by investigating the environmental impacts of concrete replacing different percentage of cement with CS. As a case study, the LCA was performed for low-rise and mid-rise structures designed with varying concrete strengths, and a cost analysis was performed for these structures when replacing different percentages of cement with CS. Based on the results, the usage of CS was established as being beneficial to the impact categories ADP (Abiotic Depletion Potential (Fossil)) and GWP (Global Warming Potential), but exerted damaging effects on ADP (Abiotic Depletion Potential) and HTP (Human Toxicity Potential). On the basis of the cost analysis, the use of CS as a partial cement replacement was found to reduce building costs by a maximum of 1.4%, which is statistically significant. When evaluating the risk in comparison to the benefit of using CS in buildings, it was found that the negative environmental influence outweighed the favorable influence and cost savings resulting from the use of CS as a cement alternative. However, when only considering GWP, which is the standard procedure for environmental assessment in buildings, the use of CS as a partial cement substitute in buildings was regarded as being beneficial, yielding a 12.80% reduction in carbon emissions.

Production of concrete using reclaimed water from a ready-mix concrete batching plant: Life cycle assessment (LCA), mechanical and durability properties

This study investigates novel methods and more sustainable techniques that have been developed to minimize the environmental damage of concrete production. The use of reclaimed water and supplementary cementitious materials in concrete can be a solution to the problems of water scarcity and excessive CO2 emissions. In this context LCA, mechanical and durability properties of concrete containing silica fume as a supplementary cementitious material (SCM) and reclaimed water as an alternative source of fresh water are studied. First several properties of concrete such as consistency, compressive strength, electrical resistance, chloride ion penetration and water penetration under pressure were measured. Then, the LCA of concrete using LCA web tool was evaluated and the global warming potential (GWP) emission rates along with air pollutants such as lead, volatile organic compounds, CO, NOX, PM10 and SO2 were determined. The results show that adding a certain level of silica fume is desirable in terms of environmental issues, cost and mechanical and durability properties of concrete. In concrete containing 5, 8 and 11% of silica fume, GWP emissions decreased by 4.9, 8 and 11.2%, respectively. On the other hand, the production of lead, volatile organic compounds (VOCs), CO, NOX and PM10 decreased by 2–12%, while SO2 production increased by 4–10%. According to the obtained results, the manufacture of concrete with the mixing ratios presented in this research in a large-scale ready-mix concrete batching plant that produces 576 tonnes concrete per year (240,000 m3/year) will lead to a reduction of GWP about 3900–8700 tonnes CO2-eq per year.

Evaluation of Chloride Intrusion along Concrete–Grout Interfaces for Post-Tensioned Concrete Durability

A pour-back is a critical component of a post-tensioned concrete system, affecting its durability by protecting anchorages and vents from corrosion. However, the material interface between the grout pour-back and the concrete member may serve as an accelerated pathway for chloride ion intrusion and may lead to premature corrosion of post-tensioning components. This study evaluates the vulnerability of concrete–grout interfaces through two experimental protocols: a novel electrical migration test and the standard electrical resistivity test. The results are used to predict the service life of pour-back systems using a concrete life-cycle assessment model. This research serves as a first step toward defining the chloride permeability of concrete–grout interfaces.

A Critical Review on the Influence of Fine Recycled Aggregates on Technical Performance, Environmental Impact and Cost of Concrete

The aim of this critical review is to show the applicability of recycled fine aggregates (RFA) in concrete regarding technical performance, environmental impact, energy consumption and cost. It is not possible to judge the performance of concrete by considering one dimension. Thus, this study focussed on the fresh and hardened (e.g., mechanical and durability) properties and environmental and economic life cycle assessment of concrete. Most literature investigated showed that any addition of recycled fine aggregates from construction and demolition waste as a replacement for natural fine aggregates proves detrimental to the functional properties (quality) of the resulting concrete. However, the incorporation of recycled fine aggregates in concrete was proven to enhance the environmental and economic performance. In this study, an extensive literature review based multi criteria decision making analysis framework was made to evaluate the effect of RFA on functional, environmental, and economic parameters of concrete. The results show that sustainability of RFA based concrete is very sensitive to transportation distances. Several scenarios for the transportation distances of natural and recycled fine aggregates and their results show that only if the transportation distance of the natural aggregates is more than double that of RFA, e the RFA based concrete alternatives would be considered as more sustainable.

A Systematic Review of the Discrepancies in Life Cycle Assessments of Green Concrete

It is challenging to measure the environmental impact of concrete with the absence of a consensus on a standardized methodology for life cycle assessment (LCA). Consequently, the values communicated in the literature for “green” concrete alternatives vary widely between 84 and 612 kg eq CO2/m3. This does not provide enough evidence regarding the acclaimed environmental benefits compared to ordinary Portland cement concrete knowing that the average for the latter was concluded in this study to be around 370 kg eq CO2/m3. Thus, the purpose of this study was to survey the literature on concrete LCAs in an attempt to identify the potential sources of discrepancies and propose a potential solution. This was done through examining 146 papers systematically and attributing the sources of error to the four stages of an LCA: scope definition, inventory data, impact assessment and results interpretations. The main findings showed that there are 13 main sources of discrepancies in a concrete LCA that contribute to the incompatibility between the results. These sources varied between (i) user-based choices such as depending on a cradle-to-gate scope, selecting a basic volume-based functional unit and ignoring the impact allocation and (ii) intrinsic uncertainty in some of the elements, such as the means of transportation, the expected service life and fluctuations in market prices. The former affects the reliability of a study, and hence, a concrete LCA methodology should not allow for any of the uncertainties. On the other hand, the latter affects the degree of uncertainty of the final outcome, and hence, we recommended conducting scenario analyses and communicating the aggregated uncertainty through the selected indicators.

Development of the CO2 Emission Evaluation Tool for the Life Cycle Assessment of Concrete

With the goal of reducing greenhouse gas (GHG) emissions by 26.9% below business-as-usual by 2020, the construction industry is recognized as an environmentally harmful industry because of the large quantity of consumption and waste with which it is associated, and the industry has therefore been requested to become more environmentally friendly. Concrete, a common construction material, is known to emit large amounts of environmentally hazardous waste during the processes related to its production, construction, maintenance, and demolition. To aid the concrete industry’s efforts to reduce its GHG emissions, this study developed a software program that can assess GHG emissions incurred over the life cycle of a concrete product, and a case study was conducted to determine the impact of the proposed concrete assessment program on a construction project.

Impact of Singapore's importers on life-cycle assessment of concrete

Singapore consumes large volumes of concrete to sustain its growth in construction. To comply with its Green Mark Scheme, it is necessary for Singapore to take action in consuming concrete products with lower carbon footprint. This study quantifies and suggests alternatives for reducing the embodied energy and environmental impacts of cement and aggregate consumption in concrete products being utilized in Singapore. A cradle-to-gate life-cycle assessment methodology is considered to quantify the life-cycle inventory of cement and aggregates based on the current trading volumes of these concrete materials imported to Singapore. The cradle-to-gate system boundary includes raw materials extraction, production processes, and transportation of raw materials to production facilities as well as transportation of end-products (cement and aggregates) from the production facility in the importing country to the Port of Singapore. Geographical system boundary covers the neighboring countries that export cement and aggregates to Singapore. Life-cycle inventory results include an inventory of environmental exchanges (energy as input and major air emissions as output) for the functional unit within the defined product system. In this study, results are first demonstrated as per unit weight of cement and aggregate imported to Singapore. Following the calculation of life-cycle inventory results per unit weight of cement and aggregates, embodied energy and global warming potential of a concrete mix normalized with respect to strength are compared for two scenarios. The first scenario represents the Singapore's current trading volumes while the second one is based on cement and aggregate imports from Malaysia which due to its close proximity to Singapore and efficient production technologies and greener fuel mixes results in a reduction in both global and regional impacts compared to the Singapore's current trading conditions. By importing cement and aggregates from Malaysia instead of the current trading conditions global warming potential and embodied energy of a high-strength concrete mix can be reduced by 11% and 31%, respectively.

Concrete Water Footprint Assessment Methodologies

Concrete is the single most widely used material in the world and is only surpassed by water in terms of consumption. By 2013, 4 billion tonnes of Portland cement were produced worldwide, enough to produce about 32 billion tonnes of concrete, which represents more than 4.6 tonnes of concrete per person per year. The high water consumption and large amount of wastewater generated in the concrete industry has become a very important environmental issue. Due to the large global use of concrete, it is essential to correctly assess the environmental impacts of this material including impacts related to water consumption. Life cycle perspective is important because it allows identifying and reducing water related potential environmental impacts associated with products. In concrete life cycle assessment, these impacts are not considered mostly because of lack of data. There are several methodologies for water footprint assessment, as The Water Footprint Assessment Tool and the ISO 14046:2014 standard -that is based on life cycle assessment (ISO 14044)-, as well as sustainable reporting guidelines, which include water assessment for organizations. The aim of this paper is to evaluate existing water footprint methodologies based on life-cycle assessment, their concepts and difficulties, and link them to concrete industry. Out of at least eighteen existing water footprint methodologies, it was found that four of them are feasible for cement based materials industry, however there are differences between the definitions and criteria adopted by each methodology.

The Development of Concrete Life Cycle Assessment System

In the present study, a concrete life-cycle assessment system (CLAS) is developed that can easily and quantitatively assess green-house gas emissions during the production of concrete by applying life-cycle assessment techniques. The CLAS is divided into simple and detailed assessment methods; a database (DB) of a standard mix design and energy consumption amount, and basic green-house units applicable to each method, was constructed. A case assessment using the developed system showed that the green-house gas emission determined by the detailed assessment method differed from that by the simple assessment method by approximately 10%. These results show that the proposed method is suitable for estimating green-house gas emissions related to concrete.

The importance of use and end-of-life phases to the life cycle greenhouse gas (GHG) emissions of concrete – A review

Global climate change is one of the most significant environmental impacts at the moment. One central issue for the building and construction industry to address global climate change is the development of credible carbon labelling schemes for building materials. Various carbon labelling schemes have been developed for concrete due to its high contribution to global greenhouse gas (GHG) emissions. However, as most carbon labelling schemes adopt cradle-to-gate as system boundary, the credibility of the eco-label information may not be satisfactory because recent studies show that the use and end-of-life phases can have a significant impact on the life cycle GHG emissions of concrete in terms of carbonation, maintenance and rehabilitation, other indirect emissions, and recycling activities. A comprehensive review on the life cycle assessment of concrete is presented to holistically examine the importance of use and end-of-life phases to the life cycle GHG quantification of concrete. The recent published ISO 14067: Carbon footprint of products – requirements and guidelines for quantification and communication also mandates the use of cradle-to-grave to provide publicly available eco-label information when the use and end-of-life phases of concrete can be appropriately simulated. With the support of Building Information Modelling (BIM) and other simulation technologies, the contribution of use and end-of-life phases to the life cycle GHG emissions of concrete should not be overlooked in future studies.

Environmental impact and life cycle assessment (LCA) of traditional and ‘green’ concretes: Literature review and theoretical calculations

With the current focus on sustainability, it is necessary to evaluate concrete’s environmental impact properly, especially when developing new ‘green’ concrete types. Therefore, we investigated the available literature on every step in the LCA of concrete. The adopted functional unit for which the environmental impact is calculated, influences the outcome significantly. When comparing different concrete compositions, this unit should incorporate differences in strength, durability and service life. Hence, a cradle-to-grave or modified cradle-to-gate approach is advised as system boundary. When using industrial by-products as cement replacing material in ‘green’ concrete, an economical allocation of impacts is recommended. Inventory data on energy use, CO2, PM10, SOx and NOx emissions were collected and assigned to the impact categories of the problem oriented CML 2002 and the damage oriented Eco-indicator 99 impact method. Compared to Portland cement, the impact of blast-furnace slag and fly ash is about an order of a magnitude lower.