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This study investigates the prediction of the thermal conductivity of lightweight earth and raw earth blocks incorporating plant aggregates. Given the high variability of raw materials, it is not currently possible to predict the thermal performance of this type of material before sample production. This is a major obstacle to using these eco-materials, although their use is widely encouraged to improve building performance under evolving regulatory frameworks such as The French RE2020 standard. The incorporation of plant aggregates into earth-based materials offers improved insulation properties without compromising their mechanical integrity, positioning them as promising sustainable alternatives. Mean-field homogenization techniques, including the Mori-Tanaka as well as double inclusion models, are used to develop predictive tools for thermal behavior, using rigorously selected experimental data. The selected methods are particularly relevant. The Mori-Tanaka model appears to be better suited when the proportion of aggregates is limited, whereas the double inclusion scheme proves its worth when a higher proportion of aggregates is incorporated. This study emphasizes the influence of aggregate types and processing methods on thermal conductivity, highlighting the need for precise formulation and processing techniques to optimize performance. This paper demonstrates the relevance of the applied homogenization techniques applied. It enables the real morphology of the materials studied, such as aggregate shape and intrinsic cracking, to be taken into account. It contributes to the advancement of eco-material modeling toward predictive digital twins, with the goal of simulating and optimizing complex material behavior under various environmental conditions. [ABSTRACT FROM AUTHOR]

This research focuses on the bonding between calcium phosphate cement (CPC) composites designed as a thin repair overlay material and old ordinary portland cement (OPC) as a concrete substrate. The OPC concrete substrate was prepared to have a 28-day compressive strength of 50 MPa at room temperature. In order to select a suitable surface condition of the substrate to receive the repair material and the age to determine the bond strength, the development of the bond strength of the CPC overlay cast on five different preconditioned old concrete substrates was measured after 7, 14, and 28 days under laboratory conditions. It was found that the prepared saturated surface dry (SSD) substrate surface had the optimum bond strengths with the CPC material after 14 days. Subsequently, the intimate bonding relationships between the in situ cast CPC composites and the precast concrete (conditioned as the prepared SSD substrate surface) were investigated through pull-off, slant shear, and bi-shear bond tests. Results indicate a high bond between the CPC repair material and the OPC concrete substrate at room temperature. It was also found that rubber aggregates and fiber inclusions reduced such bond, with the most significant detrimental effect in composites that contained rubber aggregates and fiber reinforcements. Finally, a high positive correlation was observed among the tensile bond strength, slant shear bond strength, and bi-shear bond strength of the CPC-OPC composite systems, with cohesion and coefficient of friction values ranging from 1.37–2.94 MPa and 0.78–1.07, respectively. [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) is a multifunctional cement whose potential application depends on the reactants used to synthesise it. Just like many inorganic cements, the pure CPCs synthesised in all cases are very brittle and have low toughness values under loading. In this research, the CPC material is formed from the exothermic reaction between phosphoric acid and calcium silicate at controlled room temperature. Three fibre types, namely; macro polypropylene fibres, amorphous metallic fibres and recycled carbon fibres were chosen due to their corrosion resistance in acid to enhance the mechanical performance of this cement as a repair material. 1.5% by volume of each of these fibres were added to the CPC material and autogenously cured for 14 days at room temperature. Mechanical destructive and non-destructive tests were carried out on the resulting composites. The experimental results revealed that each type of fibre contributes to increase flexural strength, compressive strength, fracture energy and dynamic elastic modulus of CPC material. However, for this purpose the recycled carbon fibres have proven to be more efficient.

The energy and environmental transition in the building sector requires the development and use of low-impact materials. Despite the growing interest in bio-based and earth-based building materials, their widespread adoption is still limited due to a lack of hindsight, as their study is relatively recent. This study aims to contribute to the development of these materials by providing an extensive overview of key contributors (authors, countries, journals) in these fields. Then, the keywords of the corresponding publications were analyzed to reveal the main topics covered to date. First, a broad scale is presented, followed by a focus on sub-categories, specifically raw materials for bio-based building materials and implementation techniques for earth-based ones. Finally, a comparative analysis, with the themes covered by composite construction materials as a whole, completes the study. Using statistical analysis coupled with bibliometric network visualization software, this study provides clear, quantifiable, and objective insights into current trends. Furthermore, it facilitates the identification of new, promising research perspectives and highlights the importance of interdisciplinary collaboration. Physics, modeling, durability and microstructure studies emerge as relevant levers for advancing the future development of these eco-friendly building materials. [ABSTRACT FROM AUTHOR]

Due to the environmental protection requirement, fired clay bricks are not only satisfied with mechanical strength but also rising energy utilisation. Based on the analysis of microstructure, it can be found that fired clay bricks are porous composite materials. The research objective of this article is to study the effect of micropores in order to provide a reference to achieve a compromise between mechanical and thermal properties. Firstly, a simplified representative volume element containing solid matrix and pores is presented at a microscale. Next, the homogenisation technology is introduced to build a micro–macro relationship. In this paper, Ponte Castañeda–Willis scheme considering the spatial distribution of micropores is used to predict the effective elastic properties and effective thermal conductivity of fired clay bricks. The results are compared with those by Mori–Tanaka scheme. Walpole's notation is introduced to describe the transversely isotropic elastic tensors. Then, parameter calibration and experimental validation are implemented. Lastly, several conclusions and perspectives are given. Based on our results, porosity, the aspect ratio and the spatial distribution of micropores can affect the elastic and thermal properties, so we can control the macroscopic properties by changing the three factors. [ABSTRACT FROM AUTHOR]