In recent years, there has been a growing need to find sustainable solutions in the construction industry that would reduce the environmental burden and consump-tion of natural raw materials. One of the sustainable option is the use of dredged sediments as a substitute for natural aggregates in the production of concrete. Reservoir sediments have significant potential for reuse due to their unique phys-ical and chemical properties, that can contribute to the mechanical properties of the final product.

This study investigates the strength properties of composites prepared using res-ervoir sediments as a partial (20, 60, 100%) replacement of aggregates of fraction either 0/4 mm or 4/8 mm in concrete. The research involves characterizing the physical and chemical properties of the sediments, optimizing their incorporation into composite matrices, and evaluating their mechanical performance through standard compressive strengths tests. The results show that composites contain-ing reservoir sediments showed comparable, even higher strength values depending on the sediment fraction and matrix composition. In the case of 20% replacement of the 4/8mm fraction, the strength properties of the sediment-based composites were higher by about 15-20 % compared to conventional fillers. Even 100% replacement of 4/8 mm aggregate with sediments caused a decrease in the resulting strengths by only 15%. This study provides a foundation for further ex-ploration of sediment-based composites in construction and other industrial appli-cations.

This study delves into the behavior of fly ash-based geopolymer aerated mortar, emphasizing the role of various stabilizing agents in evaluating its potential as a sustainable and lightweight construction material. Fly ash, a byproduct rich in aluminosilicates, is the primary ingredient. The aeration process, aided by hydrogen peroxide (H2O2), improves thermal insulation according to the previous research. To enhance stability and performance, stabilizing agents such as polyvinyl alcohol (PVA), vegetable oil, and sodium lauryl sulfate (SLS) have been strategically integrated. The research rigorously assessed critical physical, mechanical, and thermal properties. At a water-to-binder ratio of 0.40, an increased H2O2 concentration produces a larger pore structure, accompanied by a reduction in strength. Furthermore, using a stabilizing agent minimizes pore sizes and enhances the uniformity of pore distribution, affecting the material's internal structure and bonding mechanisms. The use of PVA results in the formation of isolated pores, whereas the application of vegetable oil and SLS facilitates the creation of connected pore structures. The thermal conductivity measured in this study ranged from 0.04 to 0.3 W/m·K. The results demonstrate that the formation of pore structures significantly influences insulation performance, with a denser pore structure correlating to an increase in thermal conductivity. This research underscores the substantial potential of fly ash-based geopolymer aerated mortar in lightweight construction, providing key insights into the interactions between stabilizing agents and the material’s properties.

The application of biochar-clay composites as internal insulation is very promising, in particular for the energy efficient retrofit of listed buildings in which for conservation reasons external insulation is not viable. These composites can be applied in the form of plates, bricks or plaster as internal layer, directly on the existing plaster or in combination with other insulation materials as, e.g., blown cellulose.

The application of these composites in internal insulation systems suggests great potential, since the starting materials complement each other perfectly. The use of clay brings a high moisture buffering capability to passively regulate indoor relative humidity establishing comfortable and healthy indoor conditions and contributes at reducing the risk of mould germination. The use of biochar leads to a low effective thermal conductivity of the compound (target value 0,06 W/(m K)), which contributes at significantly reducing the wall´s thermal transmittance. Both biochar and clay are ecological and commonly available materials, which correspond to a forward-looking construction method. Biochar-clay compounds have in fact a low primary energy requirement, can be recycled several times and are easy to dispose of.

To assess the hygrothermal performance of the composites, accurate experimental characterization is required. In this paper, most relevant hygrothermal properties (thermal conductivity, sorption and desorption isotherms, vapour diffusion resistance factor, liquid water diffusivity, water uptake coefficient and capillary water content) are reported and discussed. These properties are obtained for composites of different clay types, clay volume ratios and composites densities. It is explored how the material structure and composition affect its hygrothermal properties.

This research investigates the potential of incorporating waste cigarette butts (CBs) into concrete mixtures as a sustainable approach to reducing both construction material environmental impact and CB waste accumulation. CBs, a ubiquitous waste product, persist in landfills for decades, leaching harmful toxins. This study explores the effects of incorporating CBs on the mechanical and physical properties of concrete. CBs were incorporated into concrete mixes at varying concentrations (0.25%, 0.375%, and 0.5% by weight of the total concrete mix). Reference concrete mixes without CBs were also prepared. All concrete specimens were cast and tested according to EVS standards. Five hypotheses were tested: the addition of CBs will reduce compressive strength, thermal conductivity, and self-weight, while increasing ductility and water absorption.

Results confirmed the hypotheses regarding compressive strength, thermal conductivity, and self-weight. Specifically, the addition of 0.25% CBs resulted in a reduction of compressive strength by 10.6% and flexural strength by 5.7% in 28-day specimens, compared to the reference concrete. The addition of 0.5% CBs resulted in a reduction of compressive strength by 29% and flexural strength by 27.9%. Regarding thermal conductivity, the addition of 0.25% CBs reduced it by 27%, 0.375% CBs by 24.5%, and 0.5% CBs by 37.5% compared to the reference concrete. While the absolute values of thermal conductivity may not be typical for concrete, the relative changes demonstrate a clear reduction due to the inclusion of CBs. Self-weight also decreased with increasing CB content. While water absorption increased as hypothesized, the effect on ductility was inconclusive, with high variability observed in the data, possibly due to limitations in the three-point bending test method employed. The incorporation of CBs influenced the magnitude of property changes. Given that unreinforced concrete is generally not used in flexural applications, the reduction in flexural strength observed with the inclusion of CBs may not be a significant concern.

The findings of this study suggest that utilizing CBs in concrete offers a promising avenue for sustainable construction in certain applications, particularly for non-structural elements. For example, the observed reduction in thermal conductivity could be beneficial in applications requiring improved insulation, contributing to improved building energy efficiency. Further research is recommended to investigate the long-term durability of the CB-concrete composites (including freeze-thaw resistance and chemical durability), and explore alternative testing methods for ductility to obtain more reliable results. Additionally, life-cycle assessment studies should be conducted to fully evaluate the environmental benefits of this approach.

The development of advanced materials for additive manufacturing has evolved significantly in recent years, driven by the growing demand for lightweight, cost-effective, and sustainable solutions across various industries. Among these, polymer-based foam materials have gained considerable attention due to their unique combination of low density, customizable mechanical properties, and excellent thermal and acoustic insulation capabilities. In the realm of construction and architectural applications, the emergence of printable cementless foam materials offers a versatile and environmentally friendly alternative to traditional cement-based formulations. This study used four industrial by-products, including fly ash, co-fired fly ash, slag, and ultra-fine fly ash, and mixed them as binders to form binary cementless materials. Two polymers (sodium lauryl sulfate and polyvinyl alcohol) were used as foaming agents. Test results revealed that the optimal binary binder was produced by blending 50% ultrafine fly ash with 50% co-fired fly ash. The corresponding water-to-binder ratio was 0.35; the foaming agent combination was 2% sodium lauryl sulfate mixed with 0.3% polyvinyl alcohol (the foaming agent content was 20 wt. % of water). The dry density of the specimens was less than 700 g/cm3, and the thermal conductivity was less than 0.07 W/m•K. The water-to-binder ratio of the specimens was corrected to 0.50 to meet printability requirements. The increase in ultrafine fly ash from 50% to 80% increased the printable height of the specimens from 8 to 20 layers. Besides, the compressive strength was controlled below 1 MPa and the thermal conductivity coefficient was kept below 0.09 W/m•K. In conclusion, this innovative printable binary foam material is suitable for thermal and sound insulation.

The circular economy in the construction sector presents significant opportunities to support sustainable infrastructure development, as outlined in the 2030 Sustainable Development Goals and in achieving Taiwan's 2050 Net-Zero Emissions ambition. In this study, local ternary cementless materials consisting of ground granulated blast-furnace slag, reactive ultrafine fly ash, and co-fired fly ash are proposed to support these opportunities, with propylene fiber used as an additive. Tests were conducted on fresh mixture properties, compressive strength, absorption, thermal conductivity, and life cycle assessment. The results showed that workability of the fresh mixture decreased with increasing fiber content. The highest compressive strength was observed in D3 specimen, with a value of 18.44 MPa at 91 days. Absorption tests exhibited an inconsistent relationship with fiber content. The lowest thermal conductivity was recorded in D3 specimens of 0.126 W/m⋅K. Finally, the impact assessment results from the life cycle assessment indicated that the proposed ternary materials had the potential to reduce greenhouse gases emissions compared to conventional cement.