Conference Agenda

The quality of the indoor environment is one of the key characteristics of buildings, and has a significant impact on the health of people and all living organisms. Currently, within EU countries, the problem of poor indoor microclimate quality in buildings is linked to inadequate ventilation. Low or too high relative humidity is also a negative factor.

Stabilisation of the indoor environment can generally be achieved by targeted forced air exchange and air treatment using air conditioning and humidification units, but this process is relatively energy intensive and the environment created in buildings is not always entirely positive for the human body.

One option is the use of building materials/elements in the interior that have the ability to bind and release moisture back into their structure, thereby actively influencing the indoor environment. The ideal relative humidity for a healthy environment is in the range of 40-60 %.

The aim of this paper is to present the results of a research that focuses on the study of the hygroaccumulation effect of natural-based materials and their influence on the moisture stability of the indoor environment of buildings. For the stabilization of the indoor environment of buildings, environmentally friendly, sorptive, natural-based materials were chosen, especially based on various clay materials with natural fibers. This paper presents the results of the study, which mainly focused on the sorption/desorption activity and moisture behaviour of the developed materials, in order to optimise the indoor microclimate.

The construction sector is one of the largest consumers of natural resources and generators of greenhouse gas emissions globally. In 2022, buildings accounted for 30% of final energy demand, a figure that increases to 34% when including material production. Energy-related emissions from buildings represented 27% of globalCO2 emissions, with 7-9% of these stemming from the production of building materials. In response to this impact, sustainable construction strategies promote the use of renewable materials, such as those derived from agricultural biomass, aiming to reduce the carbon footprint and improve energy efficiency.

This study aims to investigate the properties of gypsum reinforced with coconut fiber as a sustainable construction material. The goal is to evaluate its physical, mechanical, and thermal performance to determine its feasibility in construction applications, thus contributing to the sustainability of the sector. An innovative material was developed and assessed for its potential application in construction solutions, with a focus on improving both thermal insulation and mechanical strength.

The results obtained highlight several important conclusions. It was observed that the addition of coconut fiber reduced the material’s apparent density, achieving a reduction of up to 8.7%, confirming the fibers' ability to lighten the compound. Regarding mechanical strength, a 62.32% increase in flexural strength and a 24.35% increase in compressive strength were recorded compared to the reference material.

Moreover, the incorporation of coconut fiber enhanced the material's hydrophobic properties. Reduced capillary water absorption and decreased open porosity contributed to increased resistance to water vapor permeability, making the compound more suitable for applications requiring vapor control. A significant improvement in thermal conductivity was also observed, achieving a 56.3% reduction in thermal transmittance compared to conventional gypsum, favoring the material's energy efficiency.

Integrating coconut fibers into gypsum compounds represents an opportunity to move toward more sustainable and efficient construction practices. The results confirm the technical and regulatory feasibility of this material for prefabricated element applications, distinguished by its lightness, thermal properties, and environmental benefits. The use of coconut fiber aligns with circular economy principles, not only utilizing a renewable resource but also enhancing the thermal properties of the compound, offering a sustainable alternative for ceiling panels and lightweight partitions that can help reduce energy demand in buildings, which is crucial for achieving energy efficiency and decarbonization goals in the sector.

The paper presents preliminary results of research on lightweight composite based on building gypsum. In order to improve the insulating properties of gypsum plasters, researchers often use various additives with thermal insulation properties, primarily aimed at enhancing the thermal performance of such gypsum composites. Examples include expanded cork granules or polystyrene granules. In this study, we decided to explore a different mechanism to increase the porosity of the composite without using such additives. For this purpose, we utilized the phenomenon of starch gelatinization directly in the fresh gypsum slurry. As a result, a material with very high porosity is obtained. The resulting composites exhibit porosity ranging from 60% to 90%, which significantly enhances their thermal insulation properties.

We prepared a total of six types of mixtures, starting with a reference composition without starch, where the water-to-gypsum (W/G) ratio was 0.6. In each subsequent formulation, the amount of gypsum was reduced, allowing for the production of a final material with lower volume density.

The fundamental properties of the gypsum composites obtained through this process were determined, including volume density in a dry state, thermal properties and compressive strength. The sorption properties of the materials were also examined using the dynamic water vapor sorption (DVS) method. This analysis provided sorption and desorption curves for composites of varying densities. Additionally, preliminary qualitative tests of the microstructure were conducted using an scanning electron microscope.

The solution presented in this paper offers the advantage of producing a gypsum-based material with high porosity (>60%). Utilizing the starch gelatinization process directly within the slurry allows for the creation of a highly homogeneous material. In this process, the initial, temporary structure is formed by the starch gel, which serves as a framework around which the final gypsum-based structure develops after the gypsum's setting time is reached.

The innovativeness of the tested material concerns a group of materials with very good thermal properties, with the use of an easily available, relatively cheap admixture in the form of starch. It can be used for the production of e.g. lightweight plasterboards, internal thermal insulation, blocks and partition wall panels. Due to its lightness and the possibility of incorporating natural-based additives such as starch, gypsum composites align with the concept of sustainable construction, reducing resource consumption and CO₂ emissions.

The utilization of natural building materials presents significant untapped potential across various aspects, including environmental friendliness (ecology), human health (well-being), and accessibility (availability, cost-effectiveness). Substantial reserves of raw materials required for architecture based on natural resource utilization are still available. The integration of these traditionally used building materials into the modern construction industry is a relevant consideration in light of current global challenges such as climate change and energy supply.

The economic performance of the construction industry has shown a consistently growing trend over the years. Contemporary trends in the construction sector, assuming the continued viability of the current civilization model, are clearly moving towards mechanization and minimizing manual labour. Similar to other fields, 3D printing technology is beginning to emerge in the construction industry. This method is equally suitable for printing cement-based concrete mixtures as it is for clay-based earth mixtures. In this paper, considering the construction requirements of a clay-based 3D-printed wall, we examine the vapor absorption and thermal properties of mixtures based on different material compositions. We investigate how the performance of pure clay-based earth mixtures, lime-stabilized earth mixtures, cement-stabilized earth mixtures, and mixtures stabilized with both cement and lime compare in terms of vapor absorption capacity and thermal conductivity. We expect the results obtained to support the building physics dimensioning and feasibility of experimental clay-based 3D-printed wall structures.

Moist curing, i.e., hydration of Portland cement, increases strength, reduces porosity, and improves the overall quality of concrete. The literature reports changes in spectral reflectance caused by the moist curing process that have not been thoroughly explored. Previous research has focused on gray cement-based materials, such as concrete and cement paste samples, but has lacked reports of their effects on coated samples. This paper investigates the effects of moist curing on the solar reflectance of mortars coated with white pigments. Spectral reflectance measurements were conducted on samples (60x60x11mm) coated with titanium dioxide rutile, zinc oxide, and a commercial white pigment (white 6) at 1%, 5%, 10%, and 20% concentrations. The solar reflectance increased with the moist curing process and varied in function of pigment type and concentration. The highest increases observed for titanium dioxide and white 6 were 0.02 and 0.16, respectively, at 1% pigment concentration. In contrast, zinc oxide achieved the greatest increase (0.17) at 20% pigment concentration and its solar reflectance improved from 0.64 to 0.81, thus being comparable to that of titanium dioxide (0.80) and white 6 (0.80) at the same pigment concentration. The moist curing process affected the solar reflectance of white pigment-coated mortar samples and can significantly enhance the solar reflectance of cement-based materials coated with low covering power pigment, such as zinc oxide. Economic impacts should be investigated and weathering tests are required towards the understanding of the long-term effects of moist curing.

Traditional construction methods based on locally sourced and environmentally friendly materials, made a significant contribution to sustainable building practices while preserving cultural heritage. This study investigates the enhancement of cob as a traditional earth-based technique by incorporating straw fibers to improve thermal and mechanical properties. Heavy (2% straw) and lightweight (10% straw) mixtures, were tested alongside a reference mixture (without fibers). The lightweight configuration (LW) reduced thermal conductivity from 0.398 W/m·K to 0.209 W/m·K (47.4% reduction), while the heavy configuration achieved 0.227 W/m·K in thermal conductivity (43% reduction). Mechanical properties improved significantly, with compressive strength increasing from 1.7 MPa to 3.08 MPa in the LW mixture (81% improvement) and 2.46 MPa in the Heavy one (45% improvement). These results underline the potential of using straw fibers as reinforcement to improve traditional construction techniques, confirming better performance while conserving sustainability and cultural heritage.