Hygrothermal Behaviour of Air Lime Coatings with Mussel Shell Sand

Air lime coating mortars with mussel shells exhibit useful hygrothermal properties related to humidity and temperature regulation. Introducing mussel shell sand produces a significant increase in pore volume, changing mortar’s microstructure and reducing density. This is attributed to the flaky and irregular shape of the shell particles that present also traces of organic matter. In this work, the natural aggregate is replaced by mussel shell sand in increasing percentages of 25%, 50% and 75%. Additionally, a mortar with 0% of sand replacement is used as baseline of reference. These mortars are tested focusing in two main parameters, in first term, thermal conductivity. And also absorption and desorption cycles, at 80 and 50% relative humidity. The results are very positive for mussel shells specimens, it can be concluded that the use of mussel shell aggregates can improve the hygrothermal properties of air lime coating mortars. Another interesting result is a subjective property such as the aesthetic quality of the finishing, the results is pleasing and, combined with the promising hygrothermal properties opens a good opportunity for mussel shell mortars.

Impact of Biobased Surfactants on Hygrothermal Behaviour of Gypsum Foams

Reduce the impact of the building sector has become a key point of sustainable development. The production of lightweight materials for the building industry is therefore a must. To produce such materials, foaming is a process commonly used to trap air bubbles and achieve a range of low densities. A sufficient low thermal conductivity and an acceptable ability to regulate humidity variations in order to limit overall energy consumption are the sought properties. In this study, a direct foaming method is applied to formulate gypsum foams using a commercial Plaster and two biobased foaming agents based on proteins. An anionic surfactant (α-olefin sulphonate sodium salt) is used as a reference surfactant. Varying the mixing time, protein content and water content, gypsum foams were produced. The foam volume is measured continuously during the mixing step and the foam homogeneity is controlled. The densities of fresh foams and of the hardened foams are used to identify the links between formulation and foams properties. Gypsum foam specimens with different densities ranging from 300 to 750 kg/m3 are produced. The thermal conductivity and the Moisture Buffer Value measurements are performed. Such properties appear directly linked to the porosity and pore connection of the foams. The obtained results highlight the contribution of biobased surfactant to the performance of gypsum foams.

Effect of Immersion/Freezing/Drying Cycles on the Hygrothermal and Mechanical Behaviour of Hemp Concrete

Hemp concrete is one of the most used bio-based materials in the construction industry due to its hygrothermal behaviour and its low environmental footprint. This is mainly due to the complexity of the microstructure of these materials and their highly breathable nature. However, their use remains limited due to the lack of databases and guarantees regarding of the evolution of their functional properties over time. In this paper, experimental investigation has been performed to answer this problematic. The aim is to investigate the influence of accelerated aging on the properties of this material through a succession of immersion/freezing/drying cycles. Materials (aged and reference) were characterized at the same relative humidity state in order to be able to compare the results and to highlight the effect of ageing on the properties of hemp concrete. Results revealed a significant change in the microstructure of this material. As a consequence, this induced significant changes in its hygrothermal and mechanical properties. An increase of 40% in water vapour permeability and decrease of 57% in compressive strength were observed after aging (07 cycles of immersion/freezing/drying).

The effect of temperature, humidity and mechanical properties on crack formation on external thin plasters of ETICS

External Thermal Insulation Composite Systems (ETICS) are widely used in the northern hemisphere in retrofitted and new external walls. The outer layer of ETICS is usually a thin layer of plaster. The effects of temperature and humidity on the hygrothermal behaviour and mechanical properties of thin plasters have been quantified by conducting several experiments to determine the possibility of crack formation. Combinations of plasters using four types of binders are tested: mineral, polymer, silicate and silicone. Plasters are tested as four systems consisting of a base coat, a glass-fibre reinforcement mesh and a finishing coat. Sorption curves of the plaster systems are determined to gather data for numerical simulations. The coefficients of thermal and hygroscopic expansion are determined. The modulus of elasticity and tensile strength of four different plasters are measured to allow the calculation of crack formation in ETICS and suggest the distances between the deformation joints. The method demonstrated in this paper makes it possible to calculate the crack formation caused by the temperature and moisture shrinkage in the thin exterior plaster of ETICS.

Hygrothermal Behaviour of Inorganic Binder-Based Board Materials

Currently, the use of board materials as a material intended for the dry construction of building structure cladding in the building industry has become widespread. The most common types of board materials include wood-based boards (particle, fibre, laminated / plywood, oriented strand boards [OSB]), cement-bonded particleboards and gypsum plasterboards or gypsum fibre boards. In the case of board materials based on inorganic binders, these are most often represented by boards in which the fillers used are bonded by plaster or cement. Wood can then be used as filler, which is predominantly an assortment of inferior-quality trees or comes from a short rotation coppice, treated by various technological processes. Microstructure and material composition have the greatest influence on the physical and mechanical properties of the boards. The use of the boards in the internal or external environment is determined by their individual properties. Another indicator for the possible use of boards is the form of moisture with which the board comes into contact after installation into the structure. For the external environment, the boards have to withstand mainly liquid moisture; in contrast, in an internal environment, the boards come into contact mainly with air humidity. The diffusion properties of the individual products are also crucial for the overall design and use of the boards for structure cladding.