Guillaume Habert

Flow properties of MK-based geopolymer pastes. A comparative study with standard Portland cement pastes

Geopolymers are presented in many studies as alternatives to ordinary Portland cement. Previous studies have focused on their chemical and mechanical properties, their microstructures and their potential applications, but very few have focussed on their rheological behaviour. Our work highlights the fundamental differences in the flow properties, which exist between geopolymers made from metakaolin and Ordinary Portland Cement (OPC). We show that colloidal interactions between metakaolin particles are negligible and that hydrodynamic effects control the rheological behaviour. Metakaolin-based geopolymers can then be described as Newtonian fluids with the viscosity controlled mainly by the high viscosity of the suspending alkaline silicate solution and not by the contribution of direct contacts between metakaolin grains. This fundamental difference between geopolymers and OPC implies that developments made in cement technology to improve rheological behaviour such as plasticizers will not be efficient for geopolymers and that new research directions need to be explored.

A method for allocation according to the economic behaviour in the EU-ETS for by-products used in cement industry

PurposeThe most efficient way to reduce the environmental impact of cement production is to replace Portland cement with alternative cementitious materials. These are most often industrial waste such as blast-furnace slags (GBFS) and coal combustion fly ashes (FA). However, a recent European directive no longer considers these products as waste but as by-products. Therefore, the impact of their production has to be considered. Within this new framework, this study develops an evaluation method of their environmental impacts.MethodThis paper presents pre-existing methods and underlines their limits. Through our evaluation of these methods, it has become clear that the allocation procedure is necessary; however, results depend highly on the chosen allocation procedure. This study presents a new allocation method, based on the fact that both cement and the alternative materials, GBFS and FA, are produced by energy-intensive industries (cement iron and coal) which are all subjected to the European Union Greenhouse Gas Emission Trading System. In this carbon trading system, it is economically beneficial for industries to reduce their environmental impact, like for when, by example, by-products from one industry are used as alternative ‘green’ material by another industry. Our allocation coefficient is calculated so that the economic gains and losses are the same for all of the industries involved in these exchanges and provides the overall environmental benefit of the exchanges.Results and discussionThe discussion shows that whilst this method has much in common with other allocation methods, it is more accurate as it allocates the environmental costs fairly over the industries involved and is more robust because of its constant value. One of its limits is that it cannot be used for life cycle inventories; however, we test the possibility of choosing a coefficient from one impact category and applying it to all the others.ConclusionLastly, the technical term of the equation this paper presents could be employed for consequential life cycle assessment, to calculate the most environmental uses by-products could be put to.

Adaptation of environmental data to national and sectorial context: Application for reinforcing steel sold on the French market

PurposeEnvironmental data for steel products are generally proposed at a continental or a global scale. The question we are tackling here is: does the fact that steel as a global market necessarily reduces the need for national data?MethodsIn this study, the environmental impact of reinforcing steel sold in France is evaluated. To do so, a specific environmental inventory is adapted from Ecoinvent database. CML method is used for impact calculation and both methods “recycled content” as well as “end of life recycling approach” are tested.Results and discussionThis study shows that there is a specificity of reinforcing steel products sold in France compared to European value. It is due to the fact that reinforcing steel is mainly made with recycled steel as the market growth for construction product in France is limited allowing a very high recycled content. This result is not sensitive neither to the allocation method used for recycling (cut-off approach or system expansion) nor to transport distance and electricity country mix used.ConclusionsThe result of this study can be used with confidence in every construction site work located on the French territory. Furthermore, the present study advocates for an adaptation of global database to local context defined by a specific industrial sector and a geographic region even for product such as steel that may be considered as a first approximation as a global product.

The Maya blue nanostructured material concept applied to colouring geopolymers

Maya blue is an ancient nanostructured pigment synthetized by assembling indigo, a natural dye, with palygorskite, a microfibrous clay mineral. The novelty of our approach is to mimic “pre-Columbian nanotechnology” and to functionalize geopolymers with a sepiolite-based hybrid organic–inorganic nanocomposite inspired from the Maya blue. It is acid- and UV-resistant, as confirmed by the stability of Maya mural paintings over time. We synthesized analogous pigments, using methylene blue (MB) and methyl red (MR) as organic dyes and sepiolite as fibrous clay mineral. We used an aqueous and a solid-state method, both leading to encapsulation of dye monomers into the clay micropores, as confirmed by UV-vis spectroscopy. This nanostructured pigment was then included into a geopolymer matrix at room temperature. The stability of the new material to UV and acid was tested. It was confirmed that it is the prior encapsulation of the dye into sepiolite that leads to the stability of the pigment in the geopolymer matrix. This first study opens the way to numerous possibilities for functionalizing inorganic binder materials with organic elements that would be otherwise sensitive to thermal treatment in conventional ceramic processing.

Lime as an Anti-Plasticizer for Self-Compacting Clay Concrete

This paper focuses on the modification of clay properties with inorganic additives to deflocculate and flocculate inorganic soil for the development of a material that would be as easy to use as the current concrete products, but with a much lower environmental impact. Considering that the rheological behaviour of clays is controlled by their surface charge, we first introduce potential determining ions to deflocculate the clay particles and to reduce the yield stress of the earth material. Their efficiency is characterized using zeta potential measurements and rheological tests. We then achieve the flocculation of clay particles by using natural minerals that slowly dissolve in the interstitial liquid and ultimately precipitate calcium silicate hydrate (C–S–H). The precipitation products are identified by X-ray diffraction and the consequences of this delayed precipitation are followed by oscillatory rheometric measurements. Finally, it is suggested that in this process, C–S–H precipitation is not used as a binding vector but as an anti-plasticizer that removes the inorganic dispersant additives.

Environmental impact of Portland cement production

Abstract: With the current focus on sustainability, it is necessary to evaluate cement’s environmental impact properly, especially when developing new ‘green’ concrete types. Therefore, this chapter investigates the available literature on every process concerned during the production of cement. Inventory data on energy use, CO2, PM10, SOx and NOx emissions are collected. Alternatives and improvement are briefly described regarding energy performance and mineralogy changes that it induces for clinker.

Linking research activities and their implementation in practice in the construction sector: the LCA Construction 2012 experience

1 Introduction1.1 BackgroundNumerous research activities about life cycle assessment (LCA)appliedtobuildings,andmorerecentlytocivilengineering,haverisenoverthepastdecades.Environmentalstakesareparticularlyimportantinconstructionbecauseanyinitialdecisionhasalwayslong-termconsequences.Inadditi on,theconstructionsectorbothgenerates and recycles huge amounts of waste; it is generallyconsidered as an important contributor to climate change andinducesirreversiblechangesinlocalenvironments.Tofacethesestakes, industries invest into so-called “green innovations”,andnational or local public authorities are demanding scientificallybased decision support such as LCA. For the time being, LCAresearch appears to be fragmented between LCA practitioners invarious construction fields and LCA methodologists. However,LCApractitionersintheconstructionsectorshareidenticalmeth-odological questions. For example, drastic variations, whichinevitably occur between the early and operational stages ofconstruction projects, have led many research institutions todevelop their own dedicated LCA software tools. These toolsare, however, seldom comparable, since they generally use dif-ferent databases and assumptions. Only close cooperation be-tween LCA methodologists and construction scientists can leadto appropriate methodological developments.To better link LCA research activities and their implemen-tation in practice in the construction sector, the idea of orga-nizing a forum of discussions of recent developments andresearch results was launched in 2011 by IFSTTAR (theFrench Institute for Transport, Development and Networks)on the topics of LCA, recycling, and civil engineering. It wasthenexpandedtoLCAandbuildingswhenCSTB(theFrenchScientific and Technical Centre for Buildings) joined theinitiative. This idea leads to the organization of the firstinternational conference on LCA and Construction with afocus on civil engineering and buildings.1.2 LCA and construction activitiesUsing LCA in the construction activities has different goalsand scopes due to the different scales of the assessment

Environmental Savings Potential from the use of bahareque (mortar cement plastered bamboo) in Switzerland

The urgency for energy and material efficiency in the building sector increases every day. In the case of Switzerland, a buildings main energy demand occurs during its use/operation phase and is mainly related to heating demands during the winter season. As a means of reducing these demands, current building practice in Switzerland is to insulate with 30cm of foam and to mechanically control indoor environments. Recent research has shown, however, that alternatives to current practice are readily available. With these alternative techniques, natural materials with low embodied energy are used to produce high efficiency building envelopes. The bahareque construction method (bamboo plastered with mortar cement) studied in this paper has been identified as a promising technology both in terms of producing energy efficient building envelopes and also with regards to reducing the environmental impact associated with the construction of buildings in Switzerland. The main objective of the research presented here was to identify the Environmental Savings Potential (ESP) of bahareque in comparison with state of the art technologies in Switzerland. The calculations were geographically limited to Switzerland and the main data sets used for the life cycle assessment models corresponded to this region. Specific datasets were developed for bamboo and bahareque to account for transoceanic transportation. The results showed that bahareque achieves an ESP of 32% compared with clay brick construction and 40% when compared with concrete block construction. It was shown that it is feasible to develop highly efficient building envelopes with low embodied energy that can be used within the Swiss context.

Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs

This data article presents the life cycle inventories of 20 transitional shelter solutions. The data was gathered from the reports 8 shelter designs [1]; 10 post-disaster shelter designs [2]; the environmental impact of brick production outside of Europe [3]; and the optimization of bamboo-based post-disaster housing units for tropical and subtropical regions using LCA methodologies [4]. These reports include bill of quantities, plans, performance analysis, and lifespan of the studied shelters. The data from these reports was used to develop the Life Cycle Inventories (LCI). All the amounts were converted from their original units (length, volume and amount) into mass (kg) units and the transport distance into ton×km. These LCIs represent the production phases of each shelter and the transportation distances for the construction materials. Two types of distances were included, local (road) and international (freight ship), which were estimated based on the area of the country of study. Furthermore, the digital visualization of the shelters is presented for each of the 20 designs. Moreover, this data article presents a summary of the results for the categories Environment, Cost and Risk and the contribution to the environmental impact from the different building components of each shelter. These results are related to the article “Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs”[5]

Assessment of Sustainability of Low Carbon Cement in Cuba. Cement Pilot Production and Prospective Case

This study combines two techniques for the assessment of sustainability in cement and concrete production: Life Cycle Analysis and Eco-efficiency. The first technique is used to assess the environmental impact of Low Carbon Cement (LC3) production from quarrying to the factory´s gate. The LCA is developed in order to compare three Cuban cements and its associated impacts: OPC, PPC and LC3. For that purpose, an inventory is developed using official statistics of the cement sector, calculated productive and economic indexes and emission factors. Global warming and energy use, are the main identified impacts. The second method is employed for the calculation of the improvement potential derived from the substitution of OPC by LC3 in a model house built with LC3 in Santa Clara city. A considerable improvement of 54 percent in the eco-efficiency indicator has been achieved as a result of using blended cement that is a proper combination of clinker, metakaolin, gypsum and limestone. The results become a challenge for Cuban construction sector in order to generalize the technology as a sustainable product from the economic, social and environmental point of view.