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Una arcilla expansiva es aquella que sufre grandes variaciones de volumen según los cambios de humedad a los que está expuesta, produciendo una expansión con el aumento de humedad y una contracción con la disminución. Este fenómeno genera problemas significativos en las obras que deben cimentarse sobre este tipo de suelo. El diseño experimental consiste en efectuar pruebas de laboratorio para determinar las propiedades físicas y mecánicas de 3 muestras de arcilla expansiva, las que se comparan con muestras de suelo estabilizadas. La estabilización se realiza mediante el reemplazo de suelo por varios porcentajes de ceniza, para controlar su cambio de volumen. Para ello, se usan dos tipos de cenizas, la primera proveniente del volcán Tungurahua y la otra de origen orgánico (ceniza de cascarilla de arroz), combinadas en una proporción de partes iguales (50% - 50% en peso). Los ensayos se aplican sobre muestras de suelo con los reemplazos del 10%, 20% y 30% en peso del suelo arcilloso, por la mezcla estabilizadora de cenizas. La combinación de ceniza en la masa del suelo logra una reducción del efecto de cambio de volumen típico de las arcillas expansivas puras, una disminución del límite líquido, un descenso de la gravedad específica, disminución del índice de expansión e incremento en la resistencia al corte y coeficiente de consolidación.

International audience

International audience; This research evaluates four sustainable cementitious composites with sustainable plant fibers and bio-aggregates: (1) cementitious matrix composite with lechuguilla fibers (LFC) and (2) with flax fibers (FFC); and (3) cementitious matrix composite with wood shavings (WSC) and (4) with hemp shavings (HSC). The fibers are for reinforcement and the shavings act as bio-aggregates as a total replacement for limestone aggregates. The lechuguilla (LF) and flax (FF) fibers were treated; wood (WS) and hemp (HS) bio-aggregates were also processed. Nineteen mixtures were manufactured, and five were used as controls, and the hygrothermal, mechanical, and durability properties were evaluated. The results for LFC and FFC showed that fiber treatment negatively affected flexural–compressive strength; untreated LFC with accelerated deterioration had better mechanical behavior, higher density, and lower porosity than FFC. Strength and density decreased, but porosity increased with increasing fiber volume (Vf). Regarding WSC and HSC, the microstructure of WS and HS had a significant effect on the physical and mechanical properties. The high porosity influenced the results obtained, since it decreased compressive strength and bulk density; however, thermal conductivity, hygroscopicity, and vapor resistance showed better behavior in most cases than the control specimens, i.e., without bio-aggregates.

International audience

This study specifically investigated the influence of the composition of aluminosilicate material i.e. the substitution of metakaolin by rice husk ash and the nature of alkaline activators (Na+/K+) on mineralogical, structural, physical and mechanical properties of geopolymer binders. This influence was evaluated based on X-ray diffraction (XRD), Fourier Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscope (SEM analyses, apparent density, water accessible porosity, compressive strength and thermal properties. Two types of geopolymer binder were synthesized according to the type of alkali activator used, the NaOH-based geopolymer and the KOH-based geopolymer. The results of characterization performed after 14 days of curing of geopolymer samples showed that the activation of the aluminosilicate powder using alkaline solution led to change in their microstructure. The highest compressive strength was obtained with the NaOH-based geopolymer.

In order to increase the durability of concrete in maritime environments, it is often recommended to use supplementary cementing materials such as silica fume or blast furnace slag. Metakaolin, even of low purity, also allows a significant improvement of the chloride diffusion. The aim of this work was to evaluate the characteristics of concretes based on flash metakaolin when exposed to a marine environment. Concretes based on CEM I cement (more than 95% of clinker) or CEM II/A cement and metakaolin were compared to a cement often used in a marine context (SR cement). The results show that a substitution of metakaolin for CEM I or CEM II/A allowed a reduction of the coefficient of chloride migration into the cementitious paste on the one hand and, on the other hand, gave results similar to those of sulfate resistant cements with a low C3A content. Then, tests of accelerated corrosion confirmed the beneficial effect of metakaolin in a marine context. Finally, a predictive model was used to estimate the lifespan of the mixtures exposed to chloride ions. The model showed that the substitution of metakaolin for cement could significantly increase the lifespan of the structures.

Energy performance and thermal comfort in historic and traditional urban environments are important because of the social and cultural requirement to conserve these areas as living entities, but also for the environmental obligation to decrease the impact of existing buildings globally. The objective of ENERPAT approach is to address this global challenge from the local perspective, through the co-creation of efficient solutions that improve the energy performance of historic areas considering local techniques and skills, taking into account the whole life cycle of the solutions, and supporting local economy and business. The objective is to test the efficiency and suitability of eco-renovation strategies that have been co-created with local stakeholders and are based on traditional energy conservation measures, as a way to work with locally-based business models that can safeguard cultural aspects and enable economic development. Two living labs have been established in the cities of Vitoria-Gasteiz (Spain) and Cahors (France) in two representative buildings of the historic urban area of each city. The living labs operate as inclusive multi-agent discussion arenas with a long-term vision, where multi-criteria co-creation processes are implemented to select conservation-friendly solutions based on local materials including criteria such as operational energy, impact on heritage values, quality of life, socio-economic development and easy logistics. The energy behaviour of the buildings and the hygrothermal performance of the external walls have been studied using on-site and laboratory experiments, through an efficient partnership between local authorities and universities. Likewise, local-based refurbishment solutions that were designed in the co-creation processes have been thermally characterised in the laboratory, through thermal conductivity and guarded hot box tests. Finally, the energy improvement of the whole renovation strategy has been simulated showing the enhancement of the two buildings.

Due to its scarcity and the detrimental environmental effect of its extraction, leading to governmental restrictions, the good quality natural rounded siliceous sand became less available in Lebanon. This national and international issue affects the construction industry through the cost and the quality of concrete. Currently, this sand, too fine to be used alone as fine aggregate in concrete mixes, is always mixed with an appropriate percentage of crushed limestone sand to meet the standard grading. The objective of the study is to assess the feasibility of total replacement of natural rounded siliceous sand by crushed limestone sand to avoid the dependency of the construction field on the quality and availability of this material in the Lebanese context. The research program consists of proposing various concrete mixes without natural sand and verifying, following a performance-based approach, that their behaviors can be maintained, at different ages of hardened states, compared to those of the reference concrete incorporating natural sand. The resulting comparisons allow identifying the influences on compressive and flexural strengths of natural sand substitution and of the variations of granular size distribution. At this stage of the study, some preliminary conclusions about the applicability of the solution of natural sand total substitution are proposed.

International audience; In order to complete the in situ identification of the "demonstrator" (or model) buildings chosen in the framework of the European Regional Project SUDOE ENERPAT for the eco-renovation of heritage residential habitat in the historic centres of Cahors (France), Porto (Portugal) and Vitoria (Spain), a campaign of characterizations was carried out on the materials constituting the initial envelope. The results of the main measured material properties bricks, stones and lime plaster (taken from the envelope of the building in Cahors) are presented. The emphasis is on hygrothermal characterization. Structural characterizations are addressed as well as data on physicochemical and mechanical aspects. The results on the variations of the properties identified are discussed. The age, mineralogical composition, manufacturing process, moisture content and prevailing environmental conditions are all parameters that cause these variations and contribute to the state of preservation of ancient materials. The identified properties of the materials will serve as inputs to the software and models intended to characterize the behaviour of envelopes of ancient buildings. The first findings can help in the choices of treatment for these ancient materials. The proposed eco-renovation solutions can be appropriate for the preservation, of both the architectural heritage and the historic centres.

International audience; The starting premise of this article is that it is not environmentally consistent to stabilize earth by using more than 4% of mineral binder (cement or lime). Thus, this paper presents a study of the effects of low mineral binder contents (2 and 4%) on the properties of earth bricks. The results obtained on two different soils show that the effects are not observable for dry compressive strengths or for dry thermal conductivities but the addition of small amounts of mineral binders significantly modifies the resistance to water and the Moisture Buffer Value.

International audience; The present study investigates the possibility of developing a self-compacting lightweight mortar (SCLM) using an agricultural by-product, namely the Crushed Olive Kernel (COK) Shell. The valorization of these co-products can certainly make it possible to use them as a substitute for natural aggregates and thus create additional economic, social and environmental value; it also allows a better handling and management of these co-products.COK shells are used in this study as partial replacement of sand, at different rates, i.e. 0, 25, 50, 75 and 100%. The influence of aggregates content on the physical, mechanical and thermal characteristics of the new materials is studied, analyzed and evaluated.Since these new materials have lower thermal conductivities than that of reference mortar, they can successfully be used as substitutes for natural sand in building materials.The results obtained support the possibility of manufacturing SCLM with a 28-day compressive strength of 9.58 MPa at a 100% COK substitution rate and a thermal conductivity of 0.326 W/m.K. The flexural strength, ultrasonic pulse velocity (UPV) and modulus of elasticity (Ed) were reduced by 61%, 51% and 85%, respectively as compared to those of the reference mortar (SCMO). It is also apparent from this study that COKs are light aggregates that allow formulating light self-compacting mortars with a density between 1400 and 1900 kg/m3.

The hygrothermal refurbishment of old building envelopes is becoming a challenge because of the specific behavior of such systems. Common, commercially available solutions do not meet all the requirements, as they could affect the durability of materials but bio-based solutions could be interesting. Bio-based solutions appear to be an appropriate and a sustainable insulation for historical dwellings. In this chapter, we investigate both the laboratory and on-site behavior of some solutions and address their complexity. The on-site measurements also allow summer comfort and phase shift phenomena to be explored.

Carbonation of cement-based materials can lead to corrosion of the steel bars in reinforced concrete, and supplementary cementing materials (SCMs) often increase the carbonation kinetics compared to reference concretes made of cements composed of clinker only. The aim of this work was to assess the consequences, in terms of service life of structures, of a possible increase in the carbonation depth of metakaolin concretes. Experimental testing using accelerated (4% CO2) and natural carbonation conditions showed that increasing the metakaolin content tended to increase the carbonation depth of concretes, due to the consumption of portlandite by the pozzolanic reaction. However, most of the time, the carbonation was within the range of carbonation depths found in commercially available blended cements (including fly ash, GGBS or limestone filler) that had already proved their worth on the market. The combination of MK and limestone filler (in CEM II/A-LL with 15% MK) behaved very well with respect to carbonation, the carbonation depth being almost equivalent to that of CEM I samples. The modelling of CO2 ingress into the concretes showed that, although metakaolin increased the carbonation (except when associated with limestone filler), the carbonation depth did not exceed 30 mm after 50 years, far from the value of 50 mm generally used as concrete cover to protect the steel bars. This means that the formulations including metakaolin would not have deteriorated by the end of the building's service life.

This study presents the durability of mortars made with leftover recycled sand. In order to take the outside storage of this young concrete into consideration, with its ensuing carbonation, two series of recycled sands are studied, one non-carbonated and the other carbonated. First, all the basic characteristics, such as water absorption, density, cement content, and thermogravimetric characteristics of the sands and their fractions are studied. Since the idea of recycling leftover sand is still new and not much studied, an indepth study of its fractions is necessary. The results show that recycled sand presents two layers: an old cement paste layer and a natural sand layer. It is the old cement paste layer that varies with the size and fractions, influencing the characteristics of the sands and the durability of their mortars. Second, many indicators of durability are studied (strength, air permeability, chloride ion migration, capillarity, carbonation and porosity accessible to water) according to the mortar composition, and are compared with those of reference mortars made with natural sand. The results demonstrate that, for both kinds of mixtures, the durability range is very close to the reference. However, a marked increase of durability was observed through the chloride ion migration index of the mortar with carbonated recycled sand. It can also be underlined that the mixture with carbonated recycled sand showed equal or even better performances than non-carbonated sand (better compressive strength index, migration index and carbonation index). Overall, this study demonstrates that the recycling of these kinds of leftover sand is possible.

Historical dwellings make up a significant fraction of the French building stock and require substantial retrofitting to reduce their energy consumption and improve their thermal comfort. In the city center of Cahors, France, the old medieval dwellings are considered as valuable cultural heritage and internal insulation is often the only insulation technique that can be used when the architectural value of the exterior facade is to be preserved. However, internal insulation may have an impact upon the hygrothermal performance of the wall, leading to lowered drying capacity, with possible interstitial condensation and mold growth. Hygrothermal models may be used to assess the risk of failure, but the accuracy of the results depends on how reliable the input data is, including external boundary conditions, which may vary significantly in dense medieval cities such as Cahors. In this study, a Geographical Information System model of Cahors is used to develop EnergyPlus models of individual dwellings. The boundary conditions output by these models are, in turn, used to model the hygrothermal performance of facades with different internal insulations, using the hygrothermal tool Delphin. The Delphin outputs are then analyzed with the VTT model, a mold growth assessment model. Results highlight a quantitative correlation between some urban morphology characteristics and the hygrothermal performance of refurbished walls, with some configurations raising the risk of damage patterns. We find that bio-based insulation presents a better hygrothermal performance than mineral wool in most of the configurations.

International audience; This paper presents an experimental investigation into the use of waste recycled polyvinyl chloride (PVC) as an alternative fine aggregate in eco-friendly mortars. The aim is to improve the brittle behavior of cementitious materials in strong acid environments as well as the improvement of the thermal insulation performance of the developed material. Mortars incorporating 0, 10, 30, 50 and 70% PVC as a replacement for natural sand were studied. Density, compressive and flexural strengths, ultrasonic pulse velocity, and thermal conductivity tests were performed to evaluate the properties of PVC-mortar composites. The resistance of different mixes to strong acids was examined based on 5 weeks’ of immersion in 5% sulfuric acid (H2SO4), 5% hydrochloric acid (HCl), and 5% nitric acid (HNO3) solutions.The results showed that the incorporation of up to 70% PVC into lightweight ductile mortars is possible, though values of compressive and flexural strengths and ultrasonic pulse velocity decreased with increase in PVC content. In addition, the use of PVC aggregates by natural sand replacement caused the resistance of mortars against strong acids to increase considerably.Based on the thermal conductivity results, mortars with higher PVC aggregates rates improved the thermal insulation of composite mortars.

International audience; In recent decades, much work has been done to facilitate the technical aspect of building renovation. However, the efforts made in housing renovation, especially in condominiums, are not sufficient to meet energy transition targets. In this specific type of building, the decision-making process is complex and is influenced by multiple factors. This study attempts to highlight the determining criteria that influence the renovation of a condominium. Obviously, technical and economic factors are important, but many sociological criteria also come into play. These criteria will be integrated into an analyzing tool which will be able to propose, in addition to the proper technical solution for renovation, the best accompaniment in the decision-making process.

cited By 10; International audience; Geopolymer binders constitute an environmental friendly alternative of Portland cement, wellknown for its contribution to the emission of greenhouse gases. In this article, we study the possibility of valorizing local materials in Burkina Faso, namely metakaolin and rice husk ash, in geopolymer binders synthesis using sodium hydroxide solution. The study focused on the influence of the addition of rice husk ash and the curing temperature on the mineralogical, microstructural, physical and mechanical properties of geopolymer binders, through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, weight loss, apparent density, porosity accessible to water and compressive strength. Three types of geopolymer binders were synthesized in this study: geopolymer binders based on metakaolin alone (AN) and two other binders containing 5% (BN) and 10% (CN) of rice husk ash respectively. The results obtained show the formation of new mineral phases and an improvement of the mechanical strength with the addition of rice husk ash and with curing temperature. There is also a high porosity for all synthesized geopolymer binders. These results are presented and discussed in terms of SiO2/Al2O3 ratio and degree of polymerization. © 2016 Elsevier Ltd

WOS:000385319300080; International audience; The building construction sector has a major impact on sustainable development, mainly in terms of raw material use, greenhouse gas emissions and waste production. Studies on alternative materials are nowadays clearly a priority to improve energy consumption and optimize waste management. Bio-based construction materials could take up this environmental challenge. Bio-based aggregates are renewable, they are mainly produced locally and they constitute an important way to store carbon dioxide. Most of the time, these bio-based aggregates are sub-products from local industries located near the factories producing building materials. Their use thus contributes largely to a decrease in the waste produced. Moreover, many studies have underlined the very interesting hygrothermal properties of bio-based materials, although some interactions of the bioaggregates with their surrounding environment have to be considered. Various authors have shown that cement (e.g. Portland cement), used as a mineral binder sometimes presents compatibility problems with bio-based aggregates, which can impact the setting and hardening processes of the binder. Among the several bioaggregates that can be considered, the waste derived from the production of essential oils is becoming an important issue. Essential oils are increasingly used in industrial countries today, mainly in medicinal or beauty products for their aromatic, medicinal and biological properties. These oils are primarily obtained by distillation of aromatic and medicinal plants. The effectiveness of these industrial and traditional transformations is very low, about 1% by mass, and this leads to large amounts of solid and liquid waste. The processing of these waste materials is inexistent in some countries like France, so waste constitutes a real obstacle to the development of this industrial sector. The objectives of this work are to determine the physical characteristics of a specific aromatic and medicinal plant residue (lavender straw) and the performances of a composite including this straw in the form of bioaggregates within a pozzolanic matrix previously designed by combining metakaolin with slaked lime. The characterization of lavender aggregates was conducted through Scanning Electron Microscope observations and their bulk density, water absorption capacity, bulk thermal conductivity and particle size distribution were assessed by an image analysis method. The thermal conductivity, water vapour permeability, moisture buffer value and mechanical properties of the composite were assessed. Finally, a study was conducted in order to understand the impact of lavender aggregates on the hydration mechanisms of the pozzolanic binder. Model pastes were elaborated with a solution obtained by soaking lavender particles in demineralized water for 72 h and then filtering. The properties of the pastes were compared with those of neat pozzolanic paste. The setting time, hardening mechanisms (followed by X-ray diffraction and thermogravimetric analysis) and mechanical performance of the pozzolanic matrix were clearly influenced by the lavender extractives. (C) 2016 Elsevier Ltd. All rights reserved.

Supplementary cementitious materials (SCMs) prove to be effective to meet most of the requirements of durable concrete and leads to a significant reduction in CO 2 emissions. This research studies the effect different SCMs (natural pozzolan (PN) / limestone fine (FC) at various replacement levels) on the physical and mechano-chemical resistance of blended mortar. The paper primarily deals with the characteristics of these materials, including heat of hydration, strength and effects of aggressive chemical environments (using sulphuric acid and nitric acid). Over 6 mixes were made and compared to the control mix. Tests were conducted at different ages up to 360 days. The experimental results in general showed that Algerian mineral admixtures (PN/FC) were less vulnerable to nitric and sulphuric acid attack and improved the properties of mortars, but at different rates depending on the quantity of binder. Keywords: natural pozzolan; portlandite; limestone fine; durability; blended cements

WOS:000411524000006; International audience; Environmental issues have led to new research into the development of eco-friendly materials. For building materials, plant fibre reinforced matrix is one of the rising innovative solutions. In this paper, the benefits of reinforcing a pozzolanic matrix with flax and hemp fibres and the impact of time and environmental conditions are presented. The mechanical behaviour of the composites was studied in a bending test over 1year. Two exposure conditions were studied: controlled conditions and natural outdoor weathering. SEM observation coupled with EDS analysis was used to complete the results with the physicochemical interaction between plant fibres and the mineral matrix.

International audience; The main objective of this study is to evaluate the feasibility of stabilizing compressed earth blocks with a geopolymer binder that is less polluting than Portland cement. Thus, a performance evaluation of these materials compared to non-stabilized or Portland cement-stabilized earth blocks was the main aim this study. The geopolymer was synthesized from a mixture of metakaolin and sodium hydroxide solution. Laterite formed the principal matrix of the bricks. Compressed Earth Bricks (CEBs) stabilized with 5, 10, 15 and 20% of geopolymer were produced and compared to both CEBs containing 8% of Portland cement and CEBs without stabilizer. After a cure of 14 days for the specimens without stabilizer and geopolymerized CEBs and 21 days for Portland cement-stabilized CEBs, the blocks were subjected to several characterization tests in order to evaluate their properties (physical mechanical and thermal properties). The results showed that geopolymerization of CEBs significantly improved their mechanical performance and gave them thermal properties that were very similar to those of non-stabilized blocks. For a 15% geopolymer content, these materials displayed properties comparable to those of Portland cement-stabilized CEBs, in particular with regard to their stability in water. (C) 2018 Elsevier Ltd. All rights reserved.

WOS:000350502900004; International audience; The standard European building specifications, grouped in a nine-volume Eurocode, describe different approaches for determining the properties of commonly used building materials such as steel, aluminium, concrete, etc. The American Concrete Institute (ACI) also offers different reports concerning concrete structures (ACI 318R), lightweight concrete (ACI 213R) and the long-term mechanical behaviour (ACI 209R) of concrete. Those reports, used as building codes, are applicable when the properties and composition of the material respect various criteria. All those materials that do not meet the scope criteria of Eurocode 2 or ACI reports because of their composition, property values or application cannot be used in the design of structures with those building codes. Regarding cement-based materials, concretes and mortars whose compressive strength is lower than the minima might not be useful for structures; however, they present an interesting potential for applications such as infrastructure materials, slabs-on-ground, etc. When designing structures and infrastructures in those materials, the accuracy of any formula offered by those building codes should be checked before being used. This article compares experimental measurements and predictive formulas for the engineering properties (compressive and tensile strengths, modulus of elasticity). The results show that the addition of specific aggregates with low stiffness and strength modifies the relation between those engineering properties, thus reducing the accuracy of some of the predictive formulas suggested in ACI reports or Eurocodes.

WOS:000414758300011; International audience; The city centre of Cahors (southwest of France) is recognized as a historical heritage site and, like other city centres in Europe, it faces the complex challenge of the thermal retrofitting of old dwellings. This complexity is partly explained by the relative incompatibility of the French energy performance certificate with the retrofitting of old buildings, and by the frequent conflicts between heritage conservation policies and energy efficiency improvements. Today, the level of deterioration and the high vacancy rate of the dwellings, combined with the fuel poverty of their occupants has created an urgent need for an energy retrofit. In order to respond to this set of problems, the city council of Cahors has initiated the "Living Lab" approach, an original idea. The methodology, participants, objectives and obstacles of which are presented in this paper. Living Labs have emerged as a new research concept in which users, traditionally considered as observed subjects and end clients, become co-creators of the innovation process. As opposed to classical approaches, which may fail due to the contradictions among political, ecological, socioeconomic and technological interests, the user centred approach allows the emergence of a sustainable answer in a complex eco-system in a real life context. The first result of this study was the success associated with involving many participants - craftsmen, students, end-users, local authorities, material producers which enabled an efficient and acceptable solution to be found for refurbishment. Another issue was the improvement of both energy efficiency and hydrothermal indoor comfort for the end-users. Longer term results will be the reduction of fuel poverty for occupants, and a city centre that is alive and enjoyable to live in again. (C) 2017 Elsevier Ltd. All rights reserved.

This chapter gives the state of the art on the chemical composition of bio-aggregates and their interactions with mineral binders from the standpoint of bio-aggregate based building materials. The chemical composition of various bioresources included in bio-aggregate based building materials has been reviewed by comparing the results of 24 published references. This comparison highlights a large dispersion among the results of different references for the same bioresource, reflecting not only the effective variability of chemical composition due to agronomic, environmental and processing parameters but also the strong disparities in the results of common indirect gravimetric methods of biomass compositional analysis. However, the chemical composition of lignocellulosic particles can strongly impact their properties as bio-aggregates included in a mineral matrix. At early age, they can disturb the setting and hardening mechanisms of mineral binders; in the hardened state, they can modify the properties of the composite; and, finally, in the long term, they can influence durability.

International audience; The effects of the type of mineral addition on the behavior of SCCs in sodium sulfate environments were studied. Three strength classes (30 MPa, 50 MPa and 70 MPa) and three different mineral additions were investigated: limestone filler, fly ash and natural pozzolan. The results were compared to those of vibrated concretes. Compressive strength, mass and dimensional changes dues to sodium sulfate attack were determined. The microstructure was studied using SEM-EDS and XRD analysis. For 720 days of immersion in 5% Na2SO 4 solution, the penetration depth of sulfate in different samples was quantified using SEM-EDS. The results were consistent with those of XRD analysis. This study shows the benefic effect of the incorporation of a natural pozzolan as a mineral admixture in SCC on the resistance of these concretes in sodium sulfate medium. SCCs with natural pozzolan present characteristics very comparable with those of SCC mixtures with fly ash. It appears that the use of vibrated concretes or SCC with limestone filler, especially with low compressive strength, in a rich sodium sulfate environment is not recommended.

The work presented in this paper studies the leaching of heat-cured mortars affected by delayed ettringite formation (DEF). For this, the expansion and the leaching of various elements (OH−, Ca2+, Na+ and K+) were monitored for more than 5 years in three mortars: a reference mortar and two compositions in which 3·11% of Na2SO4 (sodium sulfate) and 1·75% of NaOH (sodium hydroxide) were added to the mixture. The four mortars expanded but with different kinetics. pH, conductivity and leaching of calcium had the same global variation: a fast decrease during the first few days of curing, a strong increase after the beginning of the expansions and, lastly, a plateau of several months followed, or not (depending on the mixtures and the progress of the reaction), by a strong decrease in leaching. Finally, the results suggest that the reasons for DEF are not only related to the leaching of alkalis.

International audience; In order to evaluate the risk of the source and quantity of cement SO3 on the expansion properties of mortars, this paper studied the influence of Gypsum, Bassanite and clinker sulfate on the cement paste expansion and the formation of delayed ettringite. The investigation covers the mortar cured at 20 °C and 80 °C and stored in water. In contradiction to many studies, the results showed that the cement produced with high sulfur clinker had lower expansion than that produced with classical gypsum or high soluble Bassanite. In addition to that, we have detected that the percentage of SO3, in the cement, could increase the risk of DEF if it surpasses the level of 3.5%. Also, the curing temperature at 80 °C affects the microstructure of concrete by generating cracks in the cement paste.

WOS:000373963700024; International audience; The objective of this study is to develop testing methods of asphalt release agent (ARA) performance and the degree to which they may damage the asphalt. The testing of ARA performance demonstrated their ability to reduce the adhesion between the asphalt and the surface of steel (asphalt tools, truck bedsaEuro broken vertical bar) by the asphalt slide test, which provided two indicators for quantifying performance. The testing of the their damage to asphalt consisted of the measurement of the degree to which the compacted asphalt is damaged by the ARA including CBR resistance, indirect-tensile strength and bitumen degradation testing, the latter also serving as a test to find the most effective bitumen remover (BR). For asphalt degradation, the indirect tensile strength test provided more consistent results than CBR resistance.

The focus of this study is on statistical analysis of hemp concrete properties. The main objective is to determine statistically the variability of the three main properties, which are: material density, compressive strength and Young’s modulus. The analysis is done with respect to four main parameters, namely: the testing laboratory equipment and procedure, the hemp shiv type, the batch elaboration and finally the specimen sizeTwo types of hemp shiv have been used with two batches for each type. Two cylindrical specimen sizes have been considered: 11x22 cm and 16x32 cm. All the specimens were manufactured and dried in the same laboratory in order to ensure the repeatability and homogeneity of studied material. After 90 days of drying under the same conditions, the specimens were transported to ten different laboratories for compressive testing. Before testing, a drying protocol during 48 hours was applied by all laboratories for all specimens. Then, a unique protocol for compressive testing has been applied using the compressive testing machine in each laboratory. Finally, all data have been collected for statistical analysis. In this study, the results obtained by different laboratories show low variability for compressive strength and dry density; which is not the case for Young's modulus. Three probability distributions, namely: normal, log-normal and Weibull, have been proposed to fit the experimental results.

WOS:000367483000036; International audience; The development of a new test method for evaluating the resistance of manufactured cementitious products to biogenic acid attack, labeled BAC-Test for Biogenic Acid Concrete Test, was reported in Part I of this paper. The performance of the test in terms of sulfur-oxidizing bacteria selection and acid and sulfate production has been validated previously. In this second part, the representativeness of the degradation mechanisms of the cementitious materials is explored. Two segments of industrial pipes - ductile cast iron coated with cementitious linings (blast furnace slag cement (BFSC) and calcium aluminate cement (CAC) mortars) - were exposed to the test for 107 days. Then linings were analyzed by SEM coupled with EDS, EPMA, and XRD. Significant differences between BFSC and CAC linings were highlighted. Abundant cracking of the BFSC lining was observed, caused by precipitation of secondary ettringite, while no cracking was observed in the CAC lining. The CAC outer layer was composed mainly of AH(3) gel. The decalcification front was deeper in the BFSC matrix than in the CAC one. (C) 2015 Elsevier Ltd. All rights reserved.

International audience; This paper is a part of a large study aimed at identifying the physical and chemical properties of limestone fillers (LF) that govern their behaviour towards self-consolidating flow. Five LF were studied, complying with the standards and selected for their significant differences in properties on the basis of the supplier's database. Despite their specific manufacturing, a thorough characterization showed that the selected LFs had very different properties in terms of surface charges, morphology, wettability and size distribution. Then, relationships were sought between these properties and the flow of LF in powder form and suspended in water, or water + polycarboxylate type High Range Water Reducer Admixture (HRWRA), or water + HRWRA + cement (OPC or slag blended cement). The flow measurements concerned flowability, floodability and shear under consolidation in the dry state, and static yield stress and apparent viscosity in the suspension state. The main results show that the LFs act in the same way on the flow as long as cement is not incorporated into the suspension. From the dry state to the water + HRWRA suspensions, the flow is dependent on the fineness of the LF. The significant relationships between the surface charges, wettability and fineness of LFs show that impurities like clays are key factors in the flow of LF suspensions. When cement was incorporated into the suspension, the flow was dependent on the interactions existing among all the constituents. Then, with a view to self-consolidating applications, it becomes possible to identify how best to incorporate LF in a cement-based matrix through the measurement of the arrangement of cement and filler particles in suspension.

This paper presents preliminary study results on the use of local natural pozzolan (NP) as a mineral addition. The natural pozzolan was obtained from a source in north-western Algeria and was composed of zeolite and plagioclase, which are mineralogical materials containing large quantities of SiO2 and Al2O3. A number of cements were prepared in which portland cement (OPC) was replaced by NP in the range of 0–25%. The parameters investigated included pozzolanic activity, setting times, heat of hydration, compressive strength, and the crystalline hydration products (by XRD).The pozzolanic activity index was evaluated on the basis of physical and mechanical parameters (standards ASTM C618 and ASTM C311) and through a chemical analysis (European standard NF EN 196-5). The performance of natural pozzolan cement exposed to aggressive solutions (sulphuric and nitric acids) and their resistance to chloride permeability were also analysed. Cet article presente des resultats d’etudes preliminaires sur l’utilisation...

International audience; This article deals with the degradation of NO present in the air by means of a photocatalytic oxidation process based on TiO2 nanoparticles incorporated in a polymer-matrix-based coating. The experimental set-up consisted of a flow type reactor adapted from the ISO 22197-1 standard. NO2 in the gas phase, and nitrate ions adsorbed on the photocatalytic surface were detected as finals products. Various parameters influencing the NO degradation efficiency were studied: the coating composition, the substrate nature, the initial concentration of NO, the polluted air flow rate and the humidity. Compared to glass, the use of mortar as the substrate enhanced the photocatalytic performance of coatings by reducing the generation of gaseous NO2 as a by-product.

The pozzolanic activity of four heated powders containing different clays has been tested. Mineral transformations during calcination from 20 to 900 °C have been followed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Compressive strength tests were performed at 1, 7 and 28 days on cement–clay mortars using 30% of pozzolanic material as a replacement by mass for cement. Calcination temperatures corresponded to the stages of potentially high reactivity identified by XRD. Results indicated that there exists incompatibility between clay minerals which can not be activated at the same temperatures. Products of recrystallisation of the earlier activated clay were already formed when the second clay type was activated. Concerning the type and the abundance of clay minerals in the raw material, this study evidences that the compressive strength is, at first approximation, correlated with the percentage of activated clay and less with the nature of the clay assemblage.

The paper presents the results of a hydration study performed in order to explain the significant increase in compressive strength at one day of age observed on steam cured mortars when 25% by mass of cement was replaced with a metakaolin. Two CEM I 52.5R cements, differing in reactivity, and a metakaolin (MK) were used. By means of XRD and thermal analysis carried out on cement pastes, blended or not with MK, the main results showed that the improvement in strength at one day of age could be explained by the occurrence of a pozzolanic reaction due to MK, thermo-activated by the high curing temperature (55 °C). The pozzolanic reaction was observed through the consumption of calcium hydroxide and an increase in the amount of C–S–H and C–S–A–H hydrated phases. This change in the hydration product nature and amount was more pronounced when MK was combined with the less reactive cement, in agreement with the mechanical results on mortars. These results are of great importance for the concrete industry where the current trend is to decrease the clinker content in cements (1 ton of clinker = 1 ton of CO 2 released). In particular, the interesting mechanical performance at early ages can be helpful for precast concrete manufacturing.

This paper deals with the use of a weathered basic oxygen furnace (BOF) slag as a main constituent in hydraulic road binder. The original idea of this study was to associate the BOF slag with ground granulated blast furnace slag (GGBFS). The free lime contained in BOF slag activated the GGBFS. Small amounts of catalyst were added to the mixtures in order to accelerate the setting of this ternary blended binder. Before studying the characteristics and the influence of the proportion of each constituent, the chemical, mineralogical and physical characteristics of BOF slag were analyzed. X-ray diffraction showed that the main minerals present were calcium silicates (βC 2 S and C 3 S), dicalcium ferrite (C 2 F), lime (CaO), a solid solution of magnesium iron oxide (MgO x FeO y ), an alumino ferrite calcium phase (C 4 AF) and, due to the weathering, calcite (CaCO 3 ) and portlandite (Ca(OH) 2 ). The activity of BOF slag in cement-based mortars was evaluated and the results show that BOF slag has little hydraulic activity and apparently no pozzolanic properties. These results were confirmed by XRD on hydrated BOF slag. Only CaO, C 3 S and C 4 AF react with water and, as the C 3 S and C 4 AF contents were relatively low, the hydraulicity of the BOF slag under study was low. However, BOF slag contains 7% of Ca(OH) 2 and, in spite of the weathering, still 5% of CaO. The production of a ternary blended binder containing a mixture of BOF slag, GGBFS and catalyst was a success. The optimization of the binder composition showed that it was possible to produce an HRB10 (the compressive strength of standardized mortars higher than 10 MPa at 56 days) by mixing 52.5% of GGBFS, 42.5% of BOF slag and 5% of catalyst. Moreover, the stability study showed that there was no problem of expansion with such a binder.

Joint density is studied in relation to petrographic and petrophysical parameters in two sedimentary carbonate formations characterized by different diagenetic histories: the Kimmeridgian limestones of the Chay Peninsula (western France) with a mean joint density of 6.37 fractures per meter (fr/m) (1.94 fr/ft), and the Bathonian limestones of the Bouye outcrop (western France) with a mean joint density of 1.9 fr/m (0.58 fr/ft). The Chay carbonates are characterized by a lower CaCO3 content, a higher average porosity, and a lower sound velocity than values recorded in the Bouye limestones. The compressive strength and Young's modulus of the Bouye carbonates are, respectively, 10 and 3 times higher than in the Chay carbonates. A statistical analysis was used to identify relationships between joint density and carbonate rock properties. When facies variations are marked, the joint density at outcrop scale is related to the mean bed thickness, the facies descriptors, and the Young's modulus. When textural variations are more limited, the joint density is controlled by the porosity. At the scale of a sedimentary basin, 63.8% of the variation in joint density may be accounted for by Young's modulus and the sparite/micrite ratio. The decrease in the sparite/micrite ratio reflects an increased number of grain boundaries in the carbonate rock, which limits grain deformation and enhances joint density. The variations in Young's modulus depend essentially on the porosity and mineralogy of the studied rocks. Any increase in CaCO3 content or decrease in porosity is associated with an increase in the elastic properties of the rock and a reduction of joint density.

Aesthetics of external concrete walls can be altered in various constructions by fast developing algae and it is useful to propose technical solutions to prevent this problem. Laboratory tests are thus necessary, on the one hand to accelerate the growth of algae on concrete and, on the other, to quantify such growths. The first part of this article was dedicated to the description of two growth tests. This second part presents the advantages and drawbacks of three complementary techniques used to analyze the colonized areas. Two methods are non-destructive and estimate either the area covered, using image analysis, or the density of algae, which directly influences the stain intensity, by spectrophotometry. The third method is destructive and is based on the measurement of chlorophyll a. It is used to obtain information on the state of vitality of the algae on the colonized surface.

The building industry is progressively trying to use self-compacting concrete (SCC) in order to improve many aspects of construction, principally reinforced concrete. However, the problem of its durability still exists, particularly in terms of physicochemical properties which are essential to avoid corrosion of rebars. The purpose of this project was to qualify the ‘potential’ durability of self-compacting concrete and reference vibrated concrete (VC) with similar compressive strength according to French recommendations. To do this, general indicators of durability (water porosity, chloride diffusion, oxygen permeability) and additional properties necessary for a better understanding (mercury porosity, water absorption by capillarity, carbonation and ammonium nitrate leaching) were examined. Various mixes of SCC and VC were therefore made with the same raw materials in identical proportions (except for the high-performance concrete). The tests conducted on the concretes studied revealed that the durability of both concretes could be regarded as equivalent. So, at the same level of compressive strength, self-compacting concrete can be considered to be as durable as vibrated concrete.

Although more than 10 years of studies on delayed ettringite formation (DEF) have led to consensus in numerous areas of past disagreements, some questions remain experimental work is needed to complete the knowledge of this pathology. Following this objective, this paper studies the influence of pre-existing microcracking, wetting/drying cycles and the type of sulfated addition on DEF in steam cured mortars. The mortar specimens were prepared using an Ordinary Portland Cement and two types of sulfate were added to the mixtures: calcium sulfate (CaSO 4 ) or sodium sulfate (Na 2 SO 4 ). The results confirm the well-known effect of temperature: no expansion was observed in any of the mixtures cured at room temperature. Moreover, no expansion was observed after 800 days for the reference mortar or for the mortar containing calcium sulfate but all the specimens of heat-cured mortars containing sodium sulfate expanded markedly after about 50 days whatever the supplementary treatments applied (thermal shrinkage or wetting/drying cycles). These results show the significant role played by alkalis in the occurrence of delayed ettringite. The supplementary treatments intended to cause prelimiray microcracking of the specimens did not promote expansion but contributed to a slight acceleration of the reaction. The ultimate values of expansion were similar to those obtained with sound mortars.