This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were prepared; two of them with a water–binder ratio of 0.45 and two of them with a water–binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanisms; one is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded.

Rapid population growth and urbanisation has entailed a strong motivation to develop more sustainable construction solutions in line with the 7th basic requirement for construction works - sustainable use of natural resources. One of the strategies is to use materials available in abundant quantities as partial replacement for cement, or to create alternative binders for concrete. The aim of the paper is to provide an overview of the current state of the art in the field of alternative binders for concrete, and to point to the opportunities and challenges for their more systematic application in engineering practice. The state of the art review is connected to scientific projects currently undertaken at the Department of Materials, Faculty of Civil Engineering University of Zagreb, Croatia.

In order to maintain the quality of construction for nearly zero energy buildings and to reduce the pressure on construction workers with the addition of the need for faster and simpler structures, the use of cavity-insulated LSF (lightweight steel frame) panels is increasing. Requirements for performance quality, quality of life, and low energy consumption have led to the need for closer examination of heat transfer through building elements. Due to the impact on increased heat losses, thermal bridges can cause structural damage due to the increased risk of water vapor condensation on the interior surface. In this paper, numerical heat transfer analysis with the optimization of thermal bridges for LSF cavity insulated walls was made in order to reduce the overall transmission heat losses. The effects of different cavity insulation materials (mineral wool and polyurethane foam) on overall heat transferred through the building elements were analyzed. Additionally, in order to reduce the effect of thermal bridges caused by the steel frame structure, the PVC spacers between the steel and sheathing panels are introduced into calculation models. Lastly, additional layers of insulation were added on the internal and external sides of the LFS panels in order to minimize the effect of thermal bridges and maximize air tightness. Combinations of all three setups were made for wall–window, ceiling–wall, wall–floor joints for the numerical calculation. For each setup, the temperature distribution and overall heat transferred through the building elements were calculated. Different thermal bridge designs have a significant influence on the overall heat transfer, and by choosing the optimal design, the transmission heat losses can be reduced by up to 67%.

This study investigates the influence of mechanically recycled EPS on the mechanical and thermal properties of EPS composites for use in thermal insulation. Composites containing 5%, 10%, 25%, and 50% recycled EPS were produced using two recycled sources (construction EPS and packaging EPS). The tested properties included density, compressive strength at 10% deformation, bending strength, and thermal conductivity. Results show that increasing recycled content leads to a decline in density, with a more pronounced drop at higher recycled levels, particularly above 10% recycled content in the S1–25 series and 25% in the other series. Compressive strength correlates closely with density regardless of recycled content or origin and the behavior largely aligns with EN 13163 predictive models for virgin EPS. Thermal conductivity remains unchanged at lower recycled contents, with minor increases (up to 6%) observed at 50% recycled content. Bending strength decreases with increasing recycled content with greater losses noted in specimens containing packaging EPS. However, despite containing recycled materials, the empirical equations stated in EN 13163:2016 for predicting thermal conductivity and compressive stress at 10% deformation remain closely correlated regardless of recycled material content, indicating that density remains the main parameter for predicting the tested properties. These findings suggest that EPS with moderate recycled content can meet performance expectations, though further research on microstructure is recommended to understand property degradation mechanisms at higher recycled levels.

The study explores the hypothesis that crystalline hydrophilic additives (CA) can enhance concrete’s resistance to freeze/thaw cycles, crucial for assessing building durability. Employing EU standards, the research evaluates concrete resistance through standardized European freeze/thaw procedures. Monitoring concrete slabs exposed to freezing in the presence of deionized water and in the presence of 3% sodium chloride solution, the study measures surface damage and relative dynamic modulus of elasticity. Additionally, it assesses internal damage through monitoring of relative dynamic modulus of elasticity on cubes and prisms submerged in water and exposed to freezing/thawing. The pore spacing factor measured here aids in predicting concrete behavior in freeze/thaw conditions. Results suggest that the standard air-entraining agent offers effective protection against surface and internal damage due to freeze/thaw cycles. However, the CA displays potential in enhancing resistance to freeze/thaw cycles, primarily in reducing internal damage at a 1% cement weight dosage. Notably, a 3% replacement of cement with CA adversely affects concrete resistance, leading to increased surface and internal damage. The findings contribute to understanding materials that can bolster concrete durability against freeze–thaw cycles, crucial for ensuring the longevity of buildings and infrastructure.

Socialist modernist architecture in the Balkan has left a valuable legacy of remarkable buildings from this century, which brought a mixture of new experiences and local traditions. Unfortunately, after the 1990s, many of these buildings have been neglected, improperly treated, or abandoned. This paper focuses on the iconic socialist modernist office building “Rilindja” in Prishtina, Kosovo, which was built in 1979. In 2010, the building envelope was changed in the name of revitalization, without considering the energy aspect. The study aims to present energy performance analysis through cost-optimal renovation measures of the building envelope while restoring the architectural values before the last renovation. Using Archicad and EcoDesigner STAR, a BIM model was created, and energy analysis was conducted. The findings indicate that eighteen proposed energy efficiency measures can achieve a reduction in energy consumption for heating and cooling of more than 80% over the life cycle period of 20 years. The comparison before and after renovation considering restoring and preserving the inherent values, while integrating energy efficiency measures was necessary, as there is a lack of such studies in the general literature. Finally, the potential of restoring the collective memory through cost-optimal analysis is emphasized as an approach for similar cases.