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The recycling of organic wastes in the field of civil engineering is a very important process as long as the products to be obtained are not subjected to stringent quality standards. This research is a part of the general policy of saving energy and protecting the environment. Its aim is to study the possibility of developing a new insulating building material by recycling vegetable waste from the olive processing industry (olive core) that discarded in nature. After having been sorted, dried and then extruded in the form of grains, these wastes are incorporated as fine aggregate (sand) in the manufacturing of self-compacting mortar (SCM) by substituting the mass of sand with different percentages (10, 20, 30 40 and 50%). The physico-mechanical and thermal properties of the obtained SCMs are analyzed and compared to the control. The results of this study show a decrease in density and compressive strength of SCM by increasing the content of olive core wastes. However, the thermal properties of SCM are improved through replacing sand by such wastes, which could allow using olive waste core based SCM in various types of nonstructural components with intriguing insulating properties.

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Buildings are responsible for a large portion of the total energy consumption, and have a heavy environmental impact. Wood is one of the most used bio-based building materials, as it helps reducing the environmental footprint of the construction sector. Spruce wood is widely available in France and therefore massively used in buildings. It has interesting thermal and acoustic insulation performances and a good hydric regulation property. Spruce wood microstructure is highly heterogeneous and multiphasic, which makes it harder to apprehend. On the other hand, sorption hysteresis phenomenon is responsible for the moisture accumulation in porous building materials. It is often neglected in hygrothermal transfers modelling, which leads to incorrect water content values. The aim of this work is to investigate the influence of the sorption hysteresis phenomenon on the hydric transfers of spruce wood. The heterogeneity of the microstructure is also considered through 3D tomographic reconstructions included in the modelling.

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The stability of ettringite under sorption and the conversion into metaettringite are studied using hybrid Grand Canonical Monte Carlo (GCMC) and (classical) Molecular Dynamics (MD) simulations sampling the osmotic ensemble. The desorption branch obtained from simulation and the associated volume changes are in agreement with the experimental evidence. We pay special attention to the structural changes at low RH, which is associated with metaettringite conversion, which is recognized as a disordered polymorph of ettringite with an unknown structure to date. We show that the conversion of ettringite into metaettringite is associated with an increase in entropy. The adsorption branch obtained from simulations is reversible in the ettringite domain in agreement with experiments. The reversibility in the conversion of metaettringite into ettringite, which is observed experimentally, is not captured by the simulation approach adopted. The large deformations associated with ettringite desorption make it difficult to capture reversibility with a direct sampling of the osmotic ensemble. Further, we discuss the role of hydrogen bonds on the hysteresis observed in sorption cycles in ettringite.

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Hemp concrete has been widely recommended as bio-based material to limit carbon emissions and energy consumption of buildings. This material presents interesting hygrothermal and acoustic performances. It is produced of hemp particles embedded in a natural cement that forms a very heterogeneous and porous component. Few works have studied the evolution of the properties of hemp and flax concrete, over time. This research aims to study the evolution of the compressive strength, the microstructure and porosity of hemp concrete over the time. Thus, three accelerated aging protocols were conducted on the formulated hemp concrete before undertaken properties tracking experimentations. Results shows that compressive strength increases up to 58 days for hemp concrete. The hemp shiv deformation depending on the accelerated aging in hemp concrete is calculated by 2D image analysis. Optical investigation was used for this experimentation. Microscopic results confirm the high degradation of such heterogeneous materials which is confirmed by the porosity results.

The response of ettringite under sorption is critical for the utilization of this mineral as an energy storage material and to understand the concrete durability problems associated with ettringite formation. We report molecular simulations directly sampling the osmotic ensemble to understand the sorption processes and structural changes in ettringite-metaettringite transition. Desorption branch and sorption-induced volume changes from simulations agree with the experiments. The structural changes at low relative humidity are analyzed, revealing for the first time details of metaettringite structure. The reversibility under sorption observed experimentally is captured by simulation in the ettringite domain. The reversibility in the conversion of metaettringite into ettringite is not captured by the direct simulations in the osmotic ensemble due to the large volume changes associated with ettringite desorption. Finally, we discuss the role of hydrogen bonds on the hysteresis in ettringite.

Some aggregates are potentially reactive and can be used because of a pessimum effect that allows reducing expansion. However some potentially reactive aggregates do not have this property and therefore cannot be employed. Thus, to valorise these potentially reactive aggregates, Supplementary Cementitious Materials (SCMs) can be added such as burnt oil shale which has been demonstrated to improve mechanical properties and inhibit ASR. This study proposed to employ burnt oil shale (BOS) from Germany and reports data on concrete based on a potentially reactive flint with a pessimum effect and two potentially reactive siliceous limestones. The action of burnt oil shale was observed in concrete expansions and aggregate degradation by SEM. At a microstructural scale, without burnt oil shale, aggregates are altered by ASR, i.e. the microcrystalline quartz for flint aggregate and finely dispersed micro-quartz for siliceous limestone aggregates present alkalis thanks to EDS analyses, which result in concrete expansion. The addition of burnt oil shale allows the reduction of aggregate degradation and modifies gel products with a lower C/S and a mix of C S H and ettringite for the flint concrete. Therefore, concrete expansion decreases approximately 90% from 17 wt% BOS with flint aggregate because of exploitation of the pessimum effect and with 30 wt% BOS for siliceous limestones. The burnt oil shale addition generates a competition between ASR and the pozzolanic reaction. The presence of micro-quartz in burnt oil shale would play a significant role in the pozzolanic reaction by fixing alkalis and thus inhibiting ASR.

There is no consensus on the physical origin of alkali-silica reaction (ASR) damage in concrete. Atomic-level detail on the intermolecular interactions of ASR products with water is critical to understand the development and to propose solutions to mitigate ASR. We combine molecular dynamics and Monte Carlo simulations to model ASR products under sorption. The hydration of shlykovite, a naturally occurring phyllosilicate structurally similar to ASR products, is analyzed with atomic-level detail. Sodium and potassium, the most relevant alkali in ASR, are considered as charge balancing cations in shlykovite. Intra- and inter-layer water content and volume remain stable under sorption at ambient pressure, which corroborates that swelling of crystalline products cannot be at the origin of ASR damage. Also, we provide the effective interactions of Na- and K-shlykovite under water-saturated conditions. These potentials of mean force can be used in mesoscale simulations to test other mechanisms of ASR damage.

The present study was conducted to provide a better understanding of the alkali-silica reactivity (ASR) of siliceous limestones in concrete applications. A Swiss siliceous limestone, which is potentially reactive, was subjected to a series of tests. Microbar tests were first conducted to classify the limestones reactivity with respect to ASR. Two other methods were then used to characterize the amount of SiO2 present. First, an analysis of the chemical composition with petrographic and mineralogical characterizations was carried out, and second, a model reactor was used to characterize the silica reactivity. The results showed a siliceous reactive limestone. In petrography, three main types of carbonate lithology were outlined according to their SiO2 and glauconitic content. The emphasis was placed on the types of SiO2 and their sizes: a finely dispersed micro- to crypto-quartz has been highlighted by SEM and TEM, and analysed as quartz. The reactive free SiO2 content, obtained by a mineralogical calculating method, completes the petrographic results. The proportion of reactive free SiO2 could be essentially attributed to the presence of finely dispersed micro- to crypto-quartz from TEM observations which is probably very reactive towards the ASR due to its small-size. The presence of finely dispersed micro- to crypto-quartz is important to consider, due to its potential effects on the concrete mixture. The grain size of SiO2 seems to be a supplementary key parameter, in addition to crystallinity and strain, since it can promote ASR development with some siliceous aggregates.

This paper presents a study of eco-aggregates produced by a new Accelerated Carbonation Technology (ACT) in a sustainable approach. These eco-aggregates, obtained by mixing industrial by-products or wastes such as ashes with carbon dioxide (CO 2 ), have some characteristics which make them useful in the field of construction materials such as natural aggregates replacement in concrete or mortar. Hygric and thermal characterizations were performed on carbonated aggregates with adapted methods. The results have been compared to that obtained with two reference aggregates: natural gravel and expanded clay. Then thermal and hygric behaviors of concretes-based on carbonated aggregates were analyzed and discussed in the field of construction. These results proved that carbonated aggregates can be valorized through the manufacturing of concrete building blocks with several advantages: mechanical strength, thermal and hygric inertias. Experimental properties allowed a numerical/digital simulation in dynamic conditions for a simple and multilayered wall using the SPARK object-oriented simulation environment that is adapted to complex problems. Their performances were compared to those of concretes based on two reference aggregates in order to highlight the feasibility of manufacturing building blocks.

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Energy efficiency and the reduction of greenhouse gas emissions are actual key issues in all the economic sectors and, in particular, in buildings which is acknowledged worldwide as one of the most energy-consuming. In this context, it would be desirable to duly address those issues by searching for and assessing proper solutions and strategies: the usage of eco-friendly construction materials can be considered as one of those. This paper reports upon the performance of three facades containing sustainable products that are manufactured using natural resources and, alternatively, post-consumer waste based materials; those are: hemp-concrete; and Recycled PolyEthylene Terephthalate (R-PET), respectively. The energy performance of each facade was assessed in terms of cooling and heating demands, electrical consumptions and indoor thermal comfort including indoor temperature and relative humidity. Additionally, a Carbon Footprint (CF) assessment was carried out considering both the estimated energy demands and the life-cycle emission factors associated with the energy mix of the countries where the facades were located, i.e. France and Italy. Based upon the findings of the study, the R-PET facade represented the most performing solution between the three facades in all the scenarios considered and, moreover, the humidity-sensitive flow rate ventilation system came out as a solution able to reduce the electricity consumptions. Finally, considering the Carbon Footprint results, the energy country mix emerged as a key issue, making the Italian case study the worst one, though the total electrical energy consumption were comparable with those of the other case studies.

This paper aims at valorise oyster shell co-products in mortars. Oyster shell are calcareous porous materials. Consequently, their use could improve the thermal insulation properties of the concrete. In order to qualify the impact of oyster shell on mortar properties, the influence of the incorporation of oyster shell powder (OS) as a substitution of sand was studied. Mortars made by replacing a part of the sand (0 – 30 – 60 %wt) by shell powder were characterized in terms of mechanical properties and microstructure. The study revealed that the substitution of sand with OS induce a decrease of their mechanical properties. This effect can be explain by higher porosity of 56% increase with 60% OS substitution compared to the reference. Open porosity measurements are confirmed by the reduction of the wave velocity by ultrasonic measurement and microscopic observations revealing smaller pores for shell based materials., Academic Journal of Civil Engineering, Vol 38 No 1 (2020): Special Issue - RUGC 2020 Marrakech

The reuse of waste materials in concrete has been a major research concern in the past decades. This process has an interesting ecological and economical impact. In this paper, the recycling of shell waste into a filling material in mortars is investigated. Shell-based products have the advantage of being porous; therefore, their use could improve the thermal insulation properties of the concrete. In this paper, The influence of the incorporation of oyster shell powder as a substitution of cement on the mechanical behavior of the mortars is determined. Mortars were made by replacing a part of the Portland cement by shell powder and characterized in terms of mechanical properties. The study revealed that the substitution of cement with oyster shell powder causes a decrease of their mechanical properties. However, it increases the open porosity of the mortars, reducing their thermal conductivity and giving them good insulation properties., Academic Journal of Civil Engineering, Vol 38 No 1 (2020): Special Issue - RUGC 2020 Marrakech

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