In this paper, the results of laboratory investigations into the time development of the shrinkage of polypropylene fiber-reinforced high-performance concrete have been analyzed. The volumetric content of polypropylene fibers contained in the investigated concretes varied from 0 to 0.75%. Within this context, the influence of both dry and previously moistened polypropylene fibers added to the concrete on the shrinkage of the composites was examined. Electronic measurements conducted from the beginning of the hardening of the concrete also covered the early stage of autogenous shrinkage that, in high-performance composites, accounts for a significant part of total shrinkage. To compare the shrinkage of fiber-reinforced concrete with that of a comparable concrete without polypropylene fibers, the shrinkage of such a comparable concrete without fibers was also included in the measurements. The measurement results of the shrinkage of polypropylene fiber-reinforced concrete and of a comparable concrete without...

Temperature control is the primary concern during the design and construction process of mass concrete structures. As the concrete production has an enormous negative environmental impact, the development of green mass concretes will eventually become as important as the thermal characteristics. Therefore, this paper investigates the use of Electric Arc Furnace (EAF) steel slag aggregate for the partial replacement of the natural aggregate in the production of mass concrete. The impact of EAF steel aggregate on mass concrete workability, strength, and thermal behaviour was analysed. In addition, a cradle-to-gate LCA study was conducted to evaluate the environmental footprint and sustainability potential of the tested mass concrete mixtures. The study results suggest that the use of EAF steel slag aggregate in combination with a low-heat cement with a high content of blast furnace slag can significantly lower the temperature, reduce the environmental impact, and increase the sustainability potential of mass concrete, while at the same time providing sufficient workability and compressive strength. The study results indicate that EAF steel slag can be upcycled into an aggregate for the production of green mass concrete mixtures.

The paper presents and analyzes the results of the underwater abrasion tests of Cementitious Acrylic Coating (CAC), which was used to protect the repaired surface of concrete dam and stilling basin of power-plant Moste on river Sava in Slovenia. Behavior of the CAC obtained with laboratory tests is rather similar to the behavior obtained after 1 year of application on the power-plant. Relatively good underwater abrasion resistance of CAC was obtained. Results of bond strength show that pressure of capillary water decreases bond between CAC and concrete surface. If such coating is additional loaded with abrasion forces, bond between those two layers becomes worse. Similar conclusions can be made on the basis of the obtained results of surface resistance to freeze-thaw test of CAC has been carried out. The resistance is rather good, but CAC separated from concrete surface, when water is present in the interface between the CAC and concrete surface during freeze-thaw loading.

This paper presents a laboratory study on the physical properties of mortar incorporating expanded vermiculite. The basic cement-lime mortar matrix remained unchanged, while the proportions of vermiculite were varied at 10%, 20%, and 30%. The research results demonstrated a significant improvement in physical properties, including compressive and flexural strength, as well as the static modulus of elasticity. This study establishes relationships between these properties and examines the impact of expanded vermiculite on characteristics such as air void content, capillary suction of hardened mortar, total porosity (according to SIA 262, Appendix A), gas and air permeability, and capillary water absorption. Additionally, the water permeability of the mortar was tested, along with its internal resistance to freeze-thaw cycles, up to 200 cycles. The findings of this laboratory research contribute to filling an existing scientific gap, demonstrating that the physical properties of mortar with the addition of expanded vermiculite at 10%, 20%, and 30% are significantly improved compared to mortar without vermiculite.

This study presents the outcomes of a comprehensive experimental investigation focused on the bond behavior between reinforcing steel bars and tremie concrete, assessed through standardized pull-out tests. The objective was to evaluate the influence of some key parameters: reinforcement bar diameter, concrete age (and associated compressive strength), steel fiber content, and a bentonite coating on rebar surfaces. Experiments were conducted under laboratory conditions according to relevant standards. Slip between the reinforcement and tremie concrete was measured using a sophisticated high-precision optical laser device, enabling accurate assessment of bond characteristics. A large, i.e., a statistically sufficient, number of specimens was tested, allowing the results to be analyzed using the ANOVA technique to determine the statistical significance of each parameter. The results show that, under most test conditions, the influence of the bentonite suspension coating on the bond strength was not statistically significant. Similarly, variations in the bar diameter and fiber content showed no statistically significant impact within the tested ranges. In contrast, concrete age (compressive strength) exhibited a statistically significant influence, confirming that concrete maturity is a dominant factor in bond development. The results contribute to a better understanding of the bond mechanisms in reinforced concrete and can assist in optimizing design strategies where bond performance is critical.

Construction and demolition waste (C&DW) has been investigated both for radionuclide sorption and as a precursor for geopolymer materials. However, research on C&DW-derived geopolymers has primarily focused on synthesis and characterization, while their role in radionuclide immobilization remains insufficiently explored. This review evaluates C&DW-derived geopolymers as promising matrices for radionuclide immobilization, focusing on retention capabilities and factors influencing immobilization performance. Available studies indicate that waste-derived geopolymer systems can limit radionuclide mobility and leaching, but their performance strongly depends on precursor composition, phase assemblage, and matrix structure. The mineral complexity of C&DW-derived matrices may provide diverse retention pathways, supporting their consideration as immobilization materials. Linking the documented sorption capacity of C&DW materials with the immobilization potential and favorable characteristics of C&DW-derived geopolymer matrices represents a promising approach for developing advanced systems for radionuclide solidification. Due to the limited number of studies directly addressing radionuclide immobilization in C&DW-derived geopolymer systems, evidence from related studies is considered to support assessment of their immobilization capacity. Nevertheless, further clarification is required regarding the integration of existing research findings, precursor heterogeneity, multi-ion interactions, and long-term performance under realistic conditions. Addressing these limitations through systematic investigations is essential to support their application in radioactive waste (RW) management.