Joanna Julia Sokołowska

This study presents an extensive investigation on the rheological and mechanical performance of cementitious mortars incorporating fines derived from recycled construction and demolition waste (CDW), including masonry units (bricks and ceiling blocks), autoclaved aerated concrete (AAC) units, and mixed demolition residues obtained during the renovation of a pre-war tenement house located in Warsaw, Poland. The CDW fines were assessed for their potential as secondary cementitious materials, SCMs. The proposed material concept aimed to integrate CDW into sustainable binder systems and reduce Portland clinker consumption, thereby lowering CO₂ emissions of the concrete industry. Binder blends were produced by replacing 25 wt%. of Portland cement with recycled fines, achieving a 33–36% fines/clinker mass ratio. Recycled fines obtained by grinding CDW materials were characterized in terms of morphology, specific gravity, PSD, specific surface area, pozzolanic activity, pH and—in the case of recycled AAC—also carbonation. Mortars mixes were tested for consistency directly after mix preparation, while hardened composites were tested for density, compressive strength and flexural strength after 28 and 90 days of water curing. Statistical analysis showed that the origin of recycled fines affected mortar performance, with pozzolanic activity identified as the key factor. However, all analyzed composites were characterized with good mechanical strength. Overall, the performed investigation confirmed the suitability of analyzed CDW fines for clinker-reduced, low-carbon binders and highlighted their potential (especially in the case of ceramic fines) to support circularity in construction.

The objective of this study was to evaluate the technical properties and assess the durability of a novel high-performance concrete with aggregates composed entirely of reactive powders derived from chalcedonite—a mineral previously not utilized in HPC technology. Since there is insufficient information on chalcedonite-based concretes in the scientific literature, the presented research aims to address these knowledge gaps. The characterization of the chalcedonite powder involved the determination of specific gravity, particle size distribution, specific surface area, and particle morphology through microscopic analysis. The hardened chalcedonite-based and reference quartz-based high-performance concretes were subjected to a comprehensive suite of tests to determine their physical properties (bulk density, water absorption, and capillary absorption) and mechanical properties (flexural and compressive strength). Durability was further assessed based on compressive strength criteria, including frost resistance and carbonation resistance. To simulate long-term performance and better evaluate the durability of the high-performance concretes, specimens were tested following standard water curing and after additional maturation processes, including thermal treatment, which in the extreme case resulted in a seven-day compressive strength of 176.9 MPa, a value higher by 56.7 MPa (corresponding to an increase of 47.1%) compared to the strength of the identical concrete not subjected to thermal treatment. To explore the potential for architectural applications, particularly in outdoor environments, capillary absorption testing was of particular importance, as it provided insight into the material’s resistance to eventual pigment leaching from the mineral matrix.

The present study explores the sustainable potential of volcanic ash sourced from the active Sakurajima volcano (Japan) as an eco-friendly alternative to Portland cement—a binder known for its high carbon emissions—in concrete and mortar production. The abundant pyroclastic material, currently a waste burden for the residents of Sakurajima and the Kagoshima Bay region, presents a unique opportunity for valorization in line with circular economy principles. Rather than treating this ash as a disposal problem, the research investigates its transformation into a valuable supplementary cementitious material (SCM), contributing to more sustainable construction practices. The investigation focused on the material characterization of the ash (including chemical composition, morphology, and PSD) and its pozzolanic activity index, which is a key indicator of its suitability as a cement replacement. Mortars were prepared with 25% of the commercial binder replaced by volcanic ash—both in its raw form and after mechanical activation—and tested for compressive strength after 28 and 90 days of water curing. Additional assessments included workability of the fresh mix (flow table test), apparent density, and flexural strength of the hardened composites. Tests results showed that the applied volcanic ash did not influence the workability of the mix and showed negligible effect on the apparent density (changes of up to 3.3%), although the mechanical strength was deteriorated (decrease by 15–33% after 7 days, and by 25–26% after 28 days). However, further investigation revealed that the simple mechanical grinding significantly enhances the pozzolanic reactivity of Sakurajima ash. The ground ash achieved a 28-day activity index of 81%, surpassing the 75% threshold set by EN 197-1 and EN 450-1 standards for type II mineral additives. These findings underscore the potential for producing low-carbon mortars and concretes using locally sourced volcanic ash, supporting both emissions reduction and sustainable resource management in construction.

The aim of the present research was to empirically prove that the non-destructive ultrasonic direct method is an effective scientific tool for measuring the maturity of polymer concretes (PC). Maturity is understood as obtaining a stabilised, maximally homogeneous, and dense microstructure of the composite, which is closely related to its mechanical strength. The direct ultrasonic method was used to assess the homogeneity, and thus the quality, of the microstructure of the composites shortly (14 days) after production and after 9 and/or 9.5 years. Different values of the ultrasonic pulse velocity were computed for "young" and several-year-old composites of identical compositions. This study confirmed the authors’ thesis that particular types of PC (with vinyl-ester matrix saturated with finely ground rocks and fossil fuel combustion by-products) show maturation extended up to several years and an additional increase in mechanical strength, despite the long-standing widespread view that polymer concretes obtain their full potential within several days. This indicates the necessity of a thorough examination of the microfiller morphology before its application in PC because it may affect the curing process and strength development. This leads to the second conclusion, that the design rules for PC with microfillers with more developed specific surface areas should be revised because the designed values may be underestimated in relation to the actual values but obtained after a longer time. Graphical abstract

This paper concerns the assessment of the lunar regolith ability to consolidate in the presence of liquid water and develop and sustain cohesion after drying. This type of cohesion originates from interparticle adhesion and can be potentially improved through grading modification. The research was conducted using the lunar regolith simulant (EAC-1A) reproducing the PSD of real lunar soil delivered from the Moon. LRS was subjected to water and elevated temperature (equal to the highest temperature on the Moon) to produce specimens of consolidated material, CCR (Capillary-Consolidated Regolith) and to test flexural strength. In order to adapt to potentially small stresses, tests were performed according to the modified EN 196-1 procedure intended for Portland cement testing: specimens scaled to 20 mm × 20 mm × 80 mm (new molds with Polytetrafluoroethylene/Teflon^® coatings reducing adhesion were created), supports spacing in the three-point flexural test reduced to 50 mm and apparatus adjusted to precisely apply small loads. CCR developed flexural strength exceeding 0.025 MPa. Then, analogous tests were performed using LRS subjected to grinding in a disc mill prior to consolidation. It was shown that simple mechanical grinding enabled the improvement of interparticle adhesion with capillary forces, resulting in improved flexural strength of the consolidated material (0.123 MPa).

In the building materials industry, similarly to other industry sectors, the quantification of greenhouse gas emissions is undertaken, enabling the identification of GHG sources both for individual production processes and in total – for specific material solutions and products. While recently a lot of attention is paid to analyze carbon footprint of ordinary concrete and development of low-emission cements with significantly reduced Portland clinker content, the issue of GHG quantification in the context of concrete-like polymer composites (including concretes with polymer binders e.g. PCC or PC and concretes with significant amounts of polymer modifiers) is not recognized. This article attempts to make a preliminary assessment of the impact of the presence of polymers on the carbon footprint of such composites.

The article presents the results of the assessment of the durability of polyester concretes containing waste microfiller (obtained from the dedusting of road aggregate) made after many years of exposure of the elements to the sulfuric acid environment. Concretes with different quantitative compositions (waste dust partially or completely replaced the commercial quartz microfiller) were exposed to the H2SO4 environment with a concentration of 0.5 M for a period of 1 month and 8 years. The measure of concrete’s acid resistance were changes in compressive strength compared to reference concretes tested immediately after obtaining technical efficiency. Additionally, 8-year-old concretes were subjected to NDT tests – the velocity of the ultrasonic wave passing through the composite was determined. It was experimentally confirmed that dust from road aggregate dedusting is a good partial substitute for commercial microfillers in polyester concretes in the context of their durability. After 8 years of exposure to H2SO4, the differences in the strength of concrete compared to analogous compositions exposed for 1 month amounted to an average of 4.9%, and compared to compositions not exposed to chemicals – an average of 9.5%. It was also shown that there is a clear relation between the ultrasonic wave velocity and the compressive strength of concrete, and any changes after exposure to acid (matrix discoloration and deposits) were only on the surface.

The presented research’s main objective was to evaluate the possibility of improving the adhesion between polypropylene fibers and mineral matrices in cementitious composites by modifying the fibers’ surface with tannic acid (TA). This modifier was previously used for polyethylene fibers only. Cement mortar containing modified polypropylene fibers and mortar containing unmodified fibers were tested. The physical and mechanical properties (apparent density, compressive strength, flexural strength and modulus of elasticity) were determined, and the fibers’ morphology after the specimens’ destruction was observed. No adverse effect of the modification was found. The elastic modulus was 6% lower after 28 days, enabling the formation of a less stiff composite material. The integrity of the specimens after mechanical damage was improved, confirming the increased adhesion between the polypropylene fibers and the hardened cement paste. The results of the introductory tests are promising; however, further research is needed in the field.

The paper concerns destructive and non-destructive (NDT) evaluation of the effect of the addition of superabsorbent polymer (SAP) used as a carrier of mixing water and a means of internal curing on the durability of concrete. The research concerns testing of five concretes—an ordinary reference concrete and four concretes differing in the content of mixing water introduced into the concrete mix in the form of pre-saturated SAP particles (25%, two variants of 50% and 75% of the total mixing water in the form of SAP hydrogel). The research consisted of 4 stages of tests. The subsequent stages involved the analysis of the effect of using SAP as a carrier of mixing water on the particular characteristics of concrete mix and hardened concrete, i.e., consistency and density of concrete mix (1st stage), carbonation tested using two indicators—phenolphthalein and thymol phenolphthalein (2nd stage), and finally: the homogeneity of the concretes’ structure by means of ultrasonic method (determination of ultrasonic pulse velocity) 28 days after production (3rd stage) and 3 years after production (4th stage). The ultrasonic pulse (or wave) velocity was then correlated with the content of water applied in the form of SAP hydrogel. The statistical analysis of results showed that the method of introducing the mixing water into the concrete mix in the form of pre-absorbed superabsorbent polymer, although it changed the concrete mix consistency, did not significantly affect the concrete ability to resist carbonation. Meanwhile, after 3 years, the densification of the microstructure of concrete with SAP has been observed.

NASA has revealed that they plan to resume manned missions and ensure the permanent presence of people in the so-called habitats on the Moon by 2024. Moon habitats are expected to be built using local resources—it is planned to use lunar regolith as aggregate in lunar concrete. Lunar concrete design requires a new approach in terms of both the production technology and the operating conditions significantly different from the Earth. Considering that more and more often it is assumed that the water present on the Moon in the form of ice might be used to maintain the base, but also to construct the base structure, the authors decided to investigate slightly more traditional composites than the recently promoted sulfur and polymer composites thermally hardened and cured. Numerous compositions of cement “lunar micro-mortars” and “lunar mortars” were made and tested to study rheological properties, namely, the consistency, which largely depend on the morphology of the fine-grained filler, i.e., regolith. For obvious reasons, the lunar regolith simulant (LRS) was used in place of the original Moon regolith. The used LRS mapped the grain size distribution and morphology of the real lunar regolith. It was created for the purpose of studying the erosive effect of dusty regolith fractions on the moving parts of lunar landers and other mechanical equipment; therefore, it simulated well the behavior of regolith particles in relation to cement paste. The obtained results made it possible to develop preliminary compositions for “lunar mortars” (possible to apply in, e.g., 3D concrete printing) and to prepare, test, and evaluate mortar properties in comparison to traditional quartz mortars (under the conditions of the Earth laboratory).