14.sustainable materials for a living world isbn 978-958-59544-0-3

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Materiales Sostenibles para un Mundo Viviente

Sustainable Materials for a Living World

Literature Review of Life Cycle Assessment Applied to GreenConcretes

Lucas Rosse Caldas, Matheus Leoni Martins Nascimento, Divino Gabriel Lima Pinheiro and

Rosa Maria Sposto, University of Brasília, Department of Civil Engineering, Brasília, DF. e-mail:[email protected], [email protected], [email protected] [email protected]

Abst ract: This paper aims to present a literature review of Life Cycle Assessment (LCA) appliedto green concretes. It proposes to study the different green concretes studied in the world by themeans of LCA. Different studies were researched in the Brazilian post-graduate programs andonline “Portal de Periódico da Capes” platform by the specific keywords: “LCA” , “life cycle”, “greenconcretes” , “waste concrete” , “fibre concrete” , “fiber concrete” and “CO2 emissions”. The data fromthe papers was tabulated in an electronic spreadsheet, organized by: authors, year of publication,

journal, kind of green concrete (industrial by-products, i. e. steel slag, rice husk ash, fly ash, etc.,

recycled aggregates and fibers), the environmental categories analyzed (kind of LCA evaluated),the scope and system boundary of studies, different kind of binders used, material propertiesanalyzed, and the software used. The results indicate that most of the studies have found that theuse of alternative and recycled materials is beneficial in the concrete production industry. Themajority research is focused on the evaluation of concrete with industrial by-products, coveringthe system boundary just from “cradle to gate”. The Global Warming Potential (GWP) was themainly environmental impact evaluated. From this literature review, it was observed that there isa need for more LCA studies applied to green concretes, mainly in Brazil, and the studies need toinvolve different kinds of fiber s. The system boundary must be extended to the “cradle to grave”or “cradle to cradle”, contemplating the use, maintenance and the end-of-life (specially reuse andrecycling scenarios) phases of concrete structures life cycle.

Keywords: LCA, green concretes, literature review.

1. Introduction

Concrete is responsible for enormous environmental impacts. Because of the great production ofthis material, vast amounts of natural resources are needed. The main component of concrete iscement and it is known that the production of cement releases great quantity of carbon dioxide(CO2) into the atmosphere. Another impact is the large amounts of water required for theproduction of concrete. Finally, the demolition and need of disposal of concrete pavements,structures and etc. generate one more environmental burden (Meyer, 2009).

For these reasons it is necessary to develop new kinds of concretes, called “green concretes”. Among the possible alternatives for the reduction of environmental impacts of conventionalconcrete is a synergistic merging of the concrete and waste sector (Turk et al., 2015). Constructionand demolition waste (C&D) can be used for the substitution of raw materials (Van den Heede &De Belle, 2012), by-products from industrial process like rice husk ash (RHA), fly ash, steel blast-furnace slag, etc. (Meyer, 2009), synthetic fibers, natural fibers like sisal fibers (Silva et al., 2010),limestone powder and other types of waste.


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However, it is necessary to evaluate these new materials in terms of performance, quality,economy, social and environmental aspects. In the existing literature there is a vast amount ofstudies concerned about the performance and properties of new or alternative materials. On theother hand, there are just few studies related to environmental aspects and ways to assessmentthe real environmental benefits of these new materials.

In this context, according to Yin et al. (2016), the Life Cycle Assessment (LCA) is an importantmethodology to quantify and compare the environmental performance of alternative products, likegreen concretes. It is the most comprehensive among the available tools and has been widelyadopted in construction and building sector (Cabeza et al., 2014). LCA evaluates all the resourcesinputs, including energy, water and materials consumption, and environmental loadings, includingCO2 emissions, liquid and solid wastes of a product or a process (International Organization forStandardization, 2006). The LCA process in ISO standard (ISO 14040 and ISO 14044) is dividedon four steps: the definition of goal and scope, the inventory analysis, the impact analysis and theinterpretation.

In Brazil, reasearches on alternative concretes related with LCA has been developed, specially,in Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia (COPPE) of

Federal University of Rio de Janeiro (UFRJ). Different kinds of green concretes have been studied,with C&D wastes, sewage waste, ashes from urban waste incineration, sugar cane ashes andconcrete with fibers; including natural fibers, like sisal, and synthetic, like Polyvinyl alcohol (PVA)and basalt.

Van den Heede & De Belle (2012) presented a literature review about LCA, comparing traditionalconcretes with “green concretes”. An important conclusion of this study is when comparingdifferent concrete compositions, the functional unit should incorporate differences in strength,durability and service life, principally when boundaries involve a cradle to grave or cradle to cradlescope. However the authors focus only in concretes with by-products as cement replacingmaterial, like blast-furnace and fly ash. Gursel et al. (2014) studied the strengths and weaknessesof concrete life-cycle inventories (LCI) in different researches. This paper shows an important

research roadmap to improve the quality of future LCA research about cement and concrete.

So it is necessary to know what kind of green concretes have been studied in the world. In thiscontext, this paper aims to present a critical literature review of LCA applied to “green concretes”.It proposes to study the different “green concretes” studied in Brazil and in the world by the meansof LCA. The scope of literature review was divided in wastes used in concrete like C&D andSupplementary Cementitious Materials (SCMs) and fibers as an alternative to steel used inreinforced concrete. It was also evaluated the methodology, scope, boundaries, softwares andproperties of green concretes in LCA studies.

2. Green Concretes

According to Scrivener & Kirkpatrick (2008), the urgency need to minimize the environmentalimpacts of cementitious materials is, and will continue to be, a major driver for innovation. Themost commonly used SCMs, blast furnace slag, fly ash, limestone, and silica fume, are industrialby-products that can be obtained in large and regular amounts, with a consistent composition.

Another material is the C&D waste. The use of by-products in concrete admixtures has threeprincipal benefits: economy of natural resources, it gives a target to the large amount of wastegenerated in industries and it extends the life cycle of landfills.


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4. Methodology

Different studies were researched in the Brazilian post-graduate programs and online Brazilianresearch platform, called “Portal de Periódico da Capes”. This platform provides, for free, severalpapers published in international periodicals such as those related to ScienceDirect, Springer, etc.

The survey was conducted by the specific keywords: “LCA” , “life cycle”, “green concretes” , “wasteconcrete” , “fibre concrete”, “fiber concrete” and “CO2 emissions”. The data from the papers wastabulated in an electronic spreadsheet, organized by: authors, year of publication, journal, kind ofgreen concrete (industrial by-products, i. e. steel slag, rice husk ash, fly ash, etc., recycledaggregates and fibres), the environmental categories analyzed, the scope and system boundaryof studies, different kind of binders used, material properties analyzed, and the software used.The information collected was turned into graphics for the quantification.

5. Related Topics – Green Concrete x LCA

LCA of “green concretes” is still a limited research field despite the expanding number of studiesin recent years. It was found in researches just few papers relating LCA and “green concretes”, a

total of 31 international papers and 1 Brazilian thesis, Silva (2015), who evaluated theenvironmental impacts of sugar cane and rice husk ashes in concretes.Figs. 1 and 2 present the number of studies found and the countries where the researchers belong,respectively. It can be seen a trend of growth in publications after 2015. In Brazil, most of studiesrelated with LCA are focused in alternative cement as verified in Faibairn et al. (2012) andPassuelo et al. (2014).

Figure 1 – Quantification of kinds of green concretes evaluated. Source: Authors (2016).


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Figure 2 – Countries where LCA and green concretes have been studied in international studies. Source: Authors (2016).

Among the used articles, Australia was the country that had the largest number of researchers(10). Followed by France (6), USA (5), Sweden (2) and Greece (2). South Korea, Portugal,Malasya, Japan, Italy, United Kingdom, Spain and Austria had just one researcher.5.1 Supplementary Cementitious Materials (SCMs), Wastes and Types of Binders Used inGreen Concretes

Fig. 3 shows the green concretes evaluated. The type of materials used were principally by-products (73%), followed by C&D (14%), other kind of waste (8%), and fibers (5%).

Figure 3 – Quantification of kinds of green concretes evaluated. Source: Authors (2016).

Related with the use of fibers in “green concretes”, it was observed that there are just few studieswhere LCA were applied in these materials. And the fibers used are synthetic like steel,polypropylene and textile. So there is a lack of studies that focused in evaluating the potentialenvironmental gains by the use of natural fibers, like vegetal fibers.

In Fig. 4 can be seen that Portland Cement was the most used type of binder (69% of the cases),and alternative binders represented 31%.


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Figure 4 – Type of binder used. Source: Authors (2016).

Some studies evaluated different kinds of binders, to substitute Portland cement. All of thenfocused in the geopolymers with alkali-activators. Geopolymers are inorganic materials rich in

Silicon and Aluminium that react with alkaline activators to become a cementitious materials.Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are usually used as alkaline activators(Turner & Collins, 2013).

Habert et al. (2011) presented a literature review analyzing OPC and geopolymers concretes andconcluded that the production of most standard types of geopolymer concrete has a slightly lowerimpact on global warming than OPC concrete. However, in the others environmental impacts, theproduction of geopolymer concrete was higher. These impacts can be reduced with the use of flyashes or granulated blast furnace slags in concrete mixtures.

For the Geopolymers binders the production and treatment of alkali activators expendituresignificant energy and CO2 emissions (Turner & Collins; 2013). According to the same authors

different values, of reduction in CO2 emissions, have been found in literature, between concreteswith geopolymers compared to concretes with OPC. These values are about, 26, 45 and 80%.These authors found a small difference, approximately 9%. The key factors that have led to thedifferences include the expenditure of significant energy during the production of alkali activatorsand the energy consumed due to elevated temperature curing.

A more recently study, Jamieson et al. (2015), evaluated a new class of geopolymer, namelyBayer-derived geopolymers. This material uses concentrated sodium aluminate solutions, calledBayer liquor, with fly ash and other aluminosilicates to form this geopolymer. The authorsconcluded that this combination of industrial by-products can reduce the energy consumption ofBayer-derived geopolymer.

So, there is a divergence of environmental values presented between conventional andgeopolymer concretes, probably because of different assumptions in scope and boundaries, asalso different technologies and energy resources. Finally, there is a need to study new class ofgeopolymers, focusing on substitutes of alkali activators, making this material more competitivethan the OPC.

The effect of the use of other alternative binders in concretes can be studied in future researches,like cement based on magnesium and sulfoaluminate cements.


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5.2 LCA Methodology, Scope and Boundaries

Among the types of LCA methodology used Fig. 5 show that LCCO2 A was the main (representing52%). LCA and LCEA represented 39% and 9%, respectively.

Figure 5 – Kind of LCA used. Source: Authors (2016).

It was verified different impact assessment methods in LCA studies. Serres et al. (2016) used mid-point methods, like EPD, CML, EDIP and BEES, with the indicators: consumption of energeticresources, abiotic depletion, water consumption, Global Warming Potential (GWP), acidificationpotential (AP), eutrophication potential (EP), ozone layer depletion (OP) and photochemicaloxidation (PO). Randl et al. (2014) evaluated GWP, AP and EP environmental indicators. Knoeriet al. (2013) evaluated two-end-point methods, the Ecoindicator 99 and Ecological Scarcity. Soeach study used different methods and environmental indicator to evaluate the green concretes.However, the environmental indicator that has been most used was GWP, related to LCCO2 Astudies. The justification for this interest in CO2 emissions is the great importance of global

warming in most of countries and after the Conference of Parties (COP21), which took place in2015, in Paris, it is expected that the number of LCCO2 A studies increase in most of countries.

The Portland cement production, in most studies, was appointed as the principal contributor forenvironmental impacts, principally the GWP, in the calcinations of calcium carbonate (CaCO3).

Most of the studies concluded that the mainly part related with GWP, CO 2 emissions, and otherenvironmental impacts is due to the Portland cement content. So, with the decrease on cementpercentage in concretes mixtures, there is a gain of environmental performance. This conclusionwas already known, the difference, is that with the application of LCA or LCCO2 A, it is possible toquantify these potential gains, changing from qualitative to quantitative data and information.

Fine and coarse aggregates presented low participation in the environmental impacts in the mostof the studies. Although they have great mass participation, the impacts related with the extractionand processing are very low. Admixtures and water in most of studies were not took intoconsideration. In studies where admixtures were accounted, they showed a low participation inenvironmental impacts, because of smaller quantities of admixtures in concrete, less than 1% bymass of concrete. The concrete mixing and batching showed a very low participation in most ofthe studies. The transport phase showed values ranging between low and average values, as aresult of the availability of raw materials and factories locations in different countries. Finally, the


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by-products showed low environmental impacts and these impacts are associated with thetreatment of by-products, like grinding and drying.

All the analyzed studies that compared the environmental impacts and concrete strengthconcluded that the substitution of cement with by-products in concrete mixes reducedenvironmental impacts, principally the GWP, without considerable reduction in compressive

strength. Some of them, like Gursel et al. (2016), also concluded an improvement in durability,related with the reduction of chloride penetration in “green concretes” analyzed.

As can be seen in Fig. 6, the main system boundary studied was cradle to gate (67%). Used andMaintenance and End-of life represented 18% and 15% of the studies, respectively.

Figure 6 – Scope and boundaries evaluated. Source: Authors (2016).

It was observed that most of the studies, like Deventer el al. (2010), Yoshioka et al. (2013), Islamet al. (2015), Gursel et al. (2016), Serres et al. (2016), Teixeira et al. (2016) and Yin et al. (2016)focused in cradle to gate phases, acounting from extraction of raw materials, production of cement,

concrete prodcution in factories, transport to building site and some case the construction ofstructures. Because of the specialty of transport distances in some studies they are estimated.Other studies evaluated a cradle to gate (contemplating use, maintenance and end-of-life phases),as verified in Collins (2010), Habert el al. (2013), Gursel et al. (2014), and Anastasiou et al. (2015).

An interesting study was done by Turk et al. (2015), who conducted a sensitivity analysis of theimpact of transport distances in different scenarios of end-of-life, and in some cases the recyclingscenario only pays off if the transport distances is not too long. So the end-of-life scenarios mustbe evaluated in combination with these waste transport distances, to choose the lowestenvironmental impact option. According with Wu et al. (2014), the end-of-life phase have aconsiderable impact on the GWP in concrete structures, specially in recycle and reuse scenarios.

5.3 Software

In the world there are some LCA software. It can be cited GaBi, SimaPro, Umberto, openLCA,BEES. GaBi, SimaPro and Umberto are the main tools used in Europe and Brazil (IBICT, 2015).Fig. 7 shows the software used in the analyzed studies.


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Figure 7 – LCA software used. Source: Authors (2016).

In the studies, 90% used SimaPro, and just 10% opted for GaBi. The SimaPro is developed byPre Consultants. Licenses range from business and educational licenses, existing standaloneversions and multi-user. The company frequently updates the software with updates including new

and existing databases as well as new features or bug fixes.There are some justifications for the adoption of SimaPro (ILCD, 2015):

The Pre Consultants has an extensive network of partners globally, as service providers,which include, for example, 2.-0 LCA Consultants (Denmark), the GreenDelta (Germany),the ESU-services Ltd. (Switzerland) and LCA Brazil (Brazil).

It has considerable database, which include ecoinvent 3.0, Agri- Footprint 1.0, ELCD 3.0,European Life Cycle Data and etc.

It presents several life-cycle impact assessment (LCIA), like ILCD 2011 midpoint, ReCiPe(midpoint), ReCiPe (Endpoint), USEtox, IPCC 2007, CML IA, Traci 2, BEES, EDIP 2003,Ecological scarcity 2006, Greenhouse Gas Protocol, Ecological footprint, Eco-indicator 99,Impact 2002+, EPS 2000 and several methods for calculate the water footprint.

Allows import and export EcoSpold 1 format.

A disadvantage that this software is not free.

5.4 Properties Evaluated in Green Concretes

It was studied two properties of concrete in hardness state, strength (62%) and durability (29%);and one property in fresh concrete, workability (11%). The results are presented in Fig. 8.


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Figure 8 – Evaluated green concrete properties. Source: Authors (2016).

These properties must be taken into consideration in functional unit of studies, to compare differentconcretes but with similar properties. Gursel et al. (2014) defend that concrete properties should

be defined transparently for an equivalent, functional unit based comparison of concrete mixturesanalyzed in different studies.

The strength was evaluated by the compressive strength stress and elastic modulus. Thedurability was evaluated by water absorption, chloride migration and chloride permeability. Theworkability was evaluated in most studies by slump flow test. So it is important to do experimentalprocedures to help the definition of the functional studies in LCA studies applied to “greenconcretes”.

It would be interesting to define some of the required or recommended tests, related to concreteproperties, for each type of green concrete studied, results in a pattern to be followed in the studiesof green concrete and LCA.

6. Conclusions

The Literature Review of LCA applied to green concretes allowed some conclusions:

Among the used articles, Australia was the country that had the largest number ofresearchers (10). Followed by France (6), USA (5), and others;

By-products were the most used SCMs (73%). Moreover, fibers and other kind of waste,and C&D represented 14%, 8% and 5%, respectively;

Portland Cement represents the mainly type of binder used (69%), against 31% ofalternative binders (geopolymers with alkali-activators);

LCCO2 A was the most used form to evaluate the environmental impacts, by GWP

potential, representing 52% of the researches. LCA and LCEA represented 39% and 9%,respectively;

The main scope and system boundary studied was cradle to gate (67%). Use andMaintenance (18%), and end-of-life (15%) were also evaluated;

SimaPro was the most used LCA software (90%). Some justifications are: the preconsultants extensive network, the considerable database and others;

Some properties of green concretes were evaluated. In hardness state 62% used strengthand 27% durability. Just 11% used workability as the evaluation of fresh concrete;


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It was observed that there is a need for more LCA studies applied to green concretes, inBrazil.

With conclusions some future needs can be considerer to improve the studies on LCA applied togreen concretes:

More studies about the use of fibers in reinforced concrete, specially natural fibers; Evaluation of alternative binders in concretes, like cement based on magnesium and

sulfoaluminate cements;

Evaluation of alternatives SCMs, like sugar cane bagasse ash, municipal waste incineratorash;

Expanding the scope and boundaries of LCA studies, covering the use, maintenance andend-of-life phases, principally reuse and recycling scenarios;

Special attention in the carbonation effect of CO2 sequestration from atmosphere anddurability of structures;

Defining some pattern to be followed in the studies of green concrete and LCA about theproperties of concrete;

Evaluation of environmental impacts of the application of green concretes in realstructures.

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Cabeza, L. F.; Rincón, L., Vilariño, V., Pérez, G., Castell, A. (2014) Life cycle assessment(LCA) and life cycle energy analysis (LCEA) of buildings and the building sector: A review.Renewable and Sustainable Energy Reviews [Online] 29 p. 394-416. Available fromhttp://www.sciencedirect.com/. [Accessed: 20/12/2015]

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14.sustainable materials for a living world isbn 978-958-59544-0-3

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