Concrete-Polymer Composites in Circular Economy

In less than a century, concrete has become the most commonly used construction material worldwide. Today, it is difficult to imagine concrete entirely devoid of polymers. The implantation of polymers into concrete has taken effect in the form of Concrete Polymer Composite [C-PC = PMC + PCC + PIC + PC]. Several milestones are recognised in the development of C-PC. They are discussed here with particular emphasis on the innovative milestones that shaped the use of polymers in concrete. As the difference between polymer cement concrete and ordinary concrete diminishes, the question: “What should the paradigm of C-PC development be?” arises.

Closing the loop of materials circulation is certainly the right way to decrease the pressure humans place on the environment. Although many efforts have been made toward effective mitigation of anthropogenic impacts, mostly on the policy dimension, there is still much more to do. The transformation affects every phase of the building’s lifecycle, which therefore requires the engagement of all value chain actors and suppliers, often assigning them new roles and responsibilities. The experiences gained from over a decade of the EU’s journey towards CE clearly indicate that, regardless of how good the legal regulations are and how effective the educational efforts are, achieving the goals of maintaining resources in the economy is not possible without the implementation of innovation and proper business models. Considering that materials and resources marketplaces are among the most common areas of Contech investment, it is worth considering what role polymer concrete composites (CPC) may play in the sector's quest for circularity. This article will try to find an answer to this dilemma by discussing the meaning of CE for the sector, its main drivers, and implications for the supply chain.

The article covers the state of circular economy implementation in Poland. The consumption of raw materials is presented, as well as indicators of monitoring the transformation of the CE in EU and Poland acc. to the COM/EC, OECD and oto-GOZ project. Poland’s priorities within the circular economy are also presented. They include innovations, markets for secondary raw materials as well as ensuring their high quality and service. The main financial, organizational, social and technological barriers defined. There are a few examples presenting technical solutions implementing the CE in Poland (e.g. building materials, hydraulic binders). The public authorities are recognized as leaders in the implementation of the CE also in the construction sector. Introducing the circular business models is also necessary.

Emerging materials and technologies (EMTs) are introduced to improve the sustainability and resilience of infrastructure. Polymer concrete (PC) has been used for the last 80 years in infrastructure applications where extreme environmental conditions and exposures are dominant. We suggest that EMTs can enable the development of next-generation PC that can contribute to infrastructure resilience and sustainability. This paper presents an overview of the latest developments in using innovative PC by incorporating a myriad of EMTs to improve infrastructure resilience and sustainability. These EMTs include nanotechnology, bio-based polymers, 3D printing, and textile reinforcement. Using nanotechnology, we demonstrate the possible production of a PC with superior ductility and self-sensing capabilities. We also show that a bio-based polyurethane PC with appreciable compressive strength of 20 MPa can be produced. We demonstrate rheological testing of polymer concrete leading to innovative 3D printed polymer concrete structures. We finally show the ability to produce superior flexural load capacity and textile-reinforced PC (TRPC) ductility compared with cementitious textile-reinforced concrete (TRC). We conclude by demonstrating the potential production of 3D printed TRPC. We suggest that the EMTs will enable a quantum leap in using PC to produce sustainable and resilient infrastructure.

Polymer-modified cement-based materials are commonly used in engineering applications and have achieved good results. The interactions between polymer and cement have received extensive attention. In this paper, the interaction between them is discussed and summarized by reviewing the existing technologies. Traditional experimental methods do not provide a comprehensive picture of the interaction between polymers and cement-based materials, molecular dynamics (MD) simulations were used recently in the study of inorganic-organic phase interactions. People almost reach a consensus on the modification mechanism of polymers on concrete at micro-scale. But at nano-scale, the interaction between polymers and cement is an ongoing work, researches show that it contains several aspects, i.e., chemical bonding, hydrogen bonding, van der Waals forces, etc. Different polymers may have different types of interactions with cement. Understanding these interactions is important to elucidate the relationship between the microstructure and macroscopic properties of polymer-modified cement-based materials. Molecular dynamics simulation has proved to be an effective method to study the interactions between inorganic-organic composites at this stage but has some limitations.

Concrete curing is an important activity from the point of view of shaping all the properties of concrete, and the way it is carried out depends primarily on the type of binder used. The optimal care effect is a kind of soft method of positive modification. Choosing such an optimal method is not an easy task, especially if the composite contains a complex binder whose components have different care requirements. The article review considerations on the optimal method of polymer-cement concrete curing, as well as the possibility of using various forms of polymers in the curing process of cement concretes.

Circular Economy, which it is among the priorities of the European Commission, is defined as an economy in which the value of products, materials and resources is maintained for as long as possible and the production of waste is reduced to minimum. Keeping in mind the impact on the environment caused on the one hand by post-consumer plastic waste and on the other hand by production processes of concrete, it is possible to find a solution able, at least partly, to mitigate these two issues. Following the principles of the circular economy, in fact, it is possible to reuse post-consumer plastic waste as fine aggregates in concrete: in this way, post-consumer plastic from waste becomes a resource; at the same time, the use of other natural resources is limited, such as the minerals traditionally used as aggregates in concrete. However, this virtuous solution still presents some problems to study and solve: this work aims to illustrate some of these issues, and provides indications on the aspects to be analyzed and solved.

Resin concrete, which has high strength, high early strength development and excellent chemical resistance, has been widely applied for repair and reinforcement of concrete structures, and precast products since the 1950’s. The research and development of resin concrete in Japan have evolved in tandem with various regions and international activities. It is a common and indispensable material for infrastructures in the world at present. On the other hand, there are so many different Acts of God, such as earthquakes, typhoons, and torrential rains, that occur in Japan, and disaster measures are an important issue. In this paper, the current status and practical application of resin concrete mainly applied for sewage products in Japan were investigated and discussed. Based on the regional characteristics of Japan, a resin concrete manhole of high quality to compensate for the defects of cement concrete was developed. Furthermore, the future trends in the research and development of resin concrete including environmental issues such as carbon dioxide emissions reduction, application of recycled materials and bioplastics to replace natural aggregates and petroleum-derived resin for concrete are proposed and discussed. A homogenization analysis method is introduced particularly to bring out the ability of resin concrete as composite materials and to carry out material development efficiently.

The literature extensively examines the utilization of sorted single-type plastic waste from post-consumer waste streams as a sustainable substitute for natural sand in cement concrete. However, severe heterogeneity of plastic waste in municipal solid waste streams, including variations in polymer types, grades, shapes, sizes, and cross-contamination with other commingled waste materials, poses a significant challenge in adopting findings from prior research that necessitates high-purity single-type plastic waste for concrete applications. This paper reports the characterization of cement concrete incorporated with mixed plastic fine aggregate (rMPFA) containing an optimized blend of plastic types produced using a proprietary mixed plastic recycling process. Five concrete mixtures containing 0% (M0), 10% (M10), 20% (M20), 30% (M30), and 40% (M40) rMPFA by volume of natural sand were investigated in this study. The laboratory results show that concrete mixture M20 had comparable compressive strength and water penetration test results when compared to control mixture M0. Additionally, toxicity characterization of concrete mixture M20 demonstrated a reduction of heavy metals in the leachate solution when compared to control mixture M0. Furthermore, microplastic detection analysis results of concrete mixtures M0 and M20 were comparable and stable.

Planet Earth is facing real challenges that require urgent and significant measures. It is necessary to give a new direction to the construction sector, making it essential to change the way that raw material is selected, giving preference to industrial by-products. The utilization of industrial wastes allows minimize the high consumption of natural raw materials, energy consumption and waste deposition in landfills. It is important to note that the use of waste in the construction industry is a great opportunity, however, the heterogeneity of these materials and sometimes their contamination can compromise the durability. The lost-wax process in foundry industry is currently an expanding area, so more and more manufacturing industries have serious problems related to their waste management. During its production process, wastes of ceramic mold shells and paraffinic wax are generated and until now any practical application is known. The main objective of this study was the correlation between the physical, mechanical behavior and durability of cement mortars with incorporation of paraffin wax and ceramic mold shells. The main results revealed a decrease in water absorption, flexural strength, and compressive strength of the mortars, along with a slight increase in degradation during freeze-thaw cycles. Additionally, a correlation was observed between the physical, mechanical performance, and durability of the mortars. This included factors such as water absorption through immersion and capillarity, as well as the relationship between compressive strength and the mass loss suffered during freeze-thaw tests.

With the aim of implementing a circular economy in all manufacturing processes, by reducing the use of raw materials, while minimizing the use of natural resources and valuing several industrial wastes, efforts are focused on the development of new techniques that allow the use of wastes in the construction sector, in order to turn them into raw materials for the development of new materials, thus achieving all the processes towards a sustainable environment.With this purpose, different precast cement cobble has been manufactured using recovered polyurethane waste from complete vehicle roofs generated in the automotive industry, turning them into a raw material. Depending on the amount of waste used, with progressive substitutions of sand of 20%, 40% and 60% of polymer waste, the final properties are achieved according to the application requirements, both in the fresh and hardened state, reaching the values required by current standards.As well as water properties and microstructure, accelerated aging tests in freeze-thaw cycles and crystallization of salts have been tested, stablishing the compressive strength before and after, guaranteeing the properties in outdoor environments in which these materials can be placed.The characterization has been completed with tests on the generation of volatile organic compounds (VOCs), fire resistance and Life Cycle Assessment (LCA).In this way, the development of innovating solutions is achieved, valorizing waste that is generated in significant quantities, being able to be used in prefabricated products to be used in the building sector.

The inclusion of polyurethane wastes as recycled and reusable materials to replace variable amounts of aggregates is interesting in the production of new construction materials due to their final properties. In this research, the effects of waste polymer replace by sand (25%) and graphene oxide on mortars (0.5, 1, 1.5, 2, 2.5 y 3% with respect to the cement) have been investigated. To maintain and even improve the final properties, graphene oxide modify aspect as thermal conductivity and electrical properties, water behavior, mechanical properties and final contribution to fire.

Implementing tire rubber-concrete mixtures to produce sandwich-structured cementitious composites can represent an attractive route in the perspective of lightweight design, energy efficiency, and sustainability for the building and construction industry. This work deals with a DOE multi-response optimization study on rubber-concrete mixes designed with different proportions of fine and coarse rubber aggregates to achieve the best formulation to be applied in the manufacturing of cementitious sandwich composites. The “sand-free” concrete mixture made up of 70% of rubber powder and 30% of rubber granules was optimal in terms of mechanical properties, physical characteristics, and thermo-acoustic insulation behavior. Sandwich-structured composite incorporating the optimum mix as a core layer showed significant improvement in terms of flexural performance over the monolithic rubberized materials and strength value in the range of RILEM “class II” lightweight construction materials.

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.

Tacit knowledge management among employees with long scientific seniority within research institutions in Poland and the European Union is being discussed. The key question under analysis is: How should the tacit knowledge of employees with long scientific seniority be managed to preserve their legacy and facilitate its transfer to younger generations? As a part of a doctoral thesis, this study aims to verify and develop methods to support the management of tacit knowledge of employees with long scientific seniority in construction institutions. To achieve this, research comprising surveys and in-depth interviews will be conducted among employees of research institutions. The anticipated outcome of this study is a comprehensive method for tacit knowledge management, which includes elements such as an environment supporting knowledge transfer, cooperation techniques, and age diversity management. The insights from this research could provide a foundation for further investigation in other regions and disciplines, ultimately leading to a deeper understanding of the process of transferring tacit knowledge of senior researchers.

In order to realize sustainable development, new types of cements were paid more attention. Calcium sulfoaluminate (CSA) cement is a kind of eco-friendly cement that has the characteristics of low carbon emission, low energy consumption, fast setting and hardening, and so on. But the main hydration product ettringite (AFt) is quite sensitive to curing conditions that makes CSA cement-based materials sensitive to temperature and ageing. Polymer plays a key role in improving the properties of CSA cement mortar. Our researches showed that styrene-butadiene copolymer (SB) could result in a big reduction of zeta potential and conductivity of the CSA cement paste, retard the very initial hydration of CSA cement but not after 3 h, and lead to the generation of more AFt and aluminium hydroxide (AH3). With SB addition increasing, the yield stress, viscosity, thixotropy, fluidity and thus workability of CSA cement mortar were significantly improved. The mechanical strength of CSA cement mortar showed a reduction after a certain age, but when SB was added there was no reduction anymore under various curing conditions. SEM observation of the morphology accounts well for the changes in mechanical properties. The shrinkage, water capillary adsorption, and durability such as resistance to freezing and thawing cycle, carbonization and sulfate attack were also investigated. This paper reviewed the role of polymer in CSA cement-based materials taking SB as an example based on recent research work of our group.

The proposed research studies the properties of gypsum mortars made with polymeric waste from the manufacturing process of high pressure laminated (HPL) thermosetting decorative panels, composed of cellulose paper layers impregnated with phenolic resins and melamine resins. The waste generated in the cutting, profiling and milling of the decorative panels is discarded and sent to landfill without a defined use. This research aims to contribute to the Circular Economy of Waste by recovering it as a raw material. Gypsum mortars are designed by adding different amounts of melamine waste. Subsequently, the properties of the mortars are studied following the technical prescriptions established in the European regulations. Firstly, the properties of the mortars in their fresh state are studied, such as the water/gypsum ratio, consistency, apparent density of the fresh mortar and setting time. Then, the properties of the hardened mortars are determined, such as the apparent density of the hardened mortar, mechanical resistance to bending and compression, adhesion, Shore C surface hardness and capillary absorption. Based on the results obtained in the tests, the viability of this type of waste is assessed for its use as a mineral aggregate to replace traditional aggregates, in order to obtain commercial gypsum mortars for use in masonry work, cladding, walls, or as a raw material for the manufacture of prefabricated materials. The results obtained show that the limit of gypsum substitution by melamine waste could be a maximum of 25%. New mortar formulations with lower substitutions would provide significant advantages in this type of ecological materials, in accordance with the technical requirements established by the applicable European regulations.

The study of the behaviour of polymeric waste in building materials is of great interest. Both sectors are important and have a significant impact on the environment, so more sustainable alternatives that drive the circular economy are needed. A multi-criteria assessment on gypsum mortar with polyurethane waste from eight different industries has been carried out to analyse in depth the influence of this polymer on building materials. The methodology used studies the physico-mechanical properties of the mixtures. A “cradle to gate” Life Cycle Assessment at laboratory level is also included to evaluate and compare their environmental performance. The dosage evaluated is the one that recovers the greatest amount of waste possible while maintaining its performance above the values established in the regulation. The results of the study show that the incorporation of polyurethane waste in gypsum mortars decreases their bulk density by 2–22% in the fresh state and 7–24% in the hardened state, while flexural and compressive strengths are reduced by about one third. The environmental impact assessment of the innovative materials shows that some samples are 15–22% more environmentally friendly than the conventional one. It is concluded that the incorporation of polyurethane waste in gypsum mortar products is a viable alternative to landfill disposal or incineration, given its good technical and environmental performance.

The construction industry today produces huge quantities of wastes, especially during the deconstruction and demolition of buildings. Ceramics and bricks represent a significant part of this inert waste in Belgium and Northern France. The recycling of bricks is already carried out in the form of aggregates used in road embankments. But this constitutes what is called a “downcycling” operation. The investigated way is here a valorization with higher added value in alkali-activated materials through substitution of blast furnace slag (GGBFS) by brick fines with a grain size D50 = 20 µm. It is shown that brick fines can be a precursor equivalent to GGBFS and thus lead to mechanical performances equivalent to control even up to 50% substitution rate in brick fines. Under certain conditions of alkali-activated solution concentration, the addition of 30% brick fines can greatly improve workability time. But this leads to a decrease in mechanical performances, which is still in accordance with specific construction needs.

Over the years, the development of sustainable and ecofriendly concrete has been found in the reuse of construction and demolition materials. One such waste is recycled aggregate from cement concrete structure demolition process. This paper analyzes the effect of substitution of natural stone aggregate with recycled aggregate in polymer composites. An experimental plan for the mixtures was prepared. Technological characteristics (setting course, consistency) and strength characteristics (flexural strength and compressive strength) were analyzed. The obtained results were statistically analyzed. A generalized utility function has been established. Based on it, the maximum dosage of recycled aggregate was determined without significant deterioration of technological and strength characteristics. The average compressive strength results obtained were in the range of 88.5 to 96.5 MPa. The highest compressive strength value (96.5 MPa) was obtained for the samples with the composition with the highest proportion of recycled aggregate.

The application of geopolymers as an alternative to cement concretes is becoming increasingly important. The significant advantage of this composites is that, the basic ingredient is not a cement, but pozzolans such as waste materials—fly ash, fly ash slag mix, red ceramic fines, recycling cement mortar—which makes building materials more environmentally friendly. Currently the availability of blast furnace slag and high-quality fly ash is limited in Europe. At the same time, the ways for management of the concrete rubble and the construction waste are being sought, because the volume of waste materials is constantly increasing.Therefore, the application of secondary binders extracted from the recycling of various construction waste (recycled cement mortar, red ceramic fines, fly ash-slag mix) in geopolymers was proposed. The recycled binders were introduced into geopolymer composites as a replacement of 25% by mass of primary binder (fly ash) and the 65, 75 and 85ºC was the curing temperature. The process of manufacturing the recycled binders has been described and basic parameters of new binders. The tests of physical and mechanical properties of the composites such as compressive strength, flexural strength, volume density in dry state and saturated one and water absorption were performed. The microstructure of geopolymers was examined using scanning electron microscopy (SEM). The results obtained show that recycled binders obtained from the treatment of construction waste could be a valuable component of geopolymers.

Geopolymer concrete is an environment-friendly material and is presently accepted as an alternative to conventional concrete. It utilizes industrial by-products like fly ash and slag to reduce CO2 emissions associated with cement production. Despite being investigated over the decades, the application of geopolymers in construction is still very limited. Most of the research data refer to geopolymer pastes and mortars and their properties, performances, and durability. Although geopolymer concretes are well-accepted in the research community owing to their comparable or even better performances as a cement substitution.In this paper, the precursors for geopolymer concrete preparations are blends of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) in three slag proportions: 5%, 20%, and 35% expressed as a percent of FA mass. The concretes were denominated AAC5, AAC20, and AAC35, respectively. Their basic physical and mechanical characteristics were investigated, as were their transport properties of chloride ions. The ASTM C1556 test was applied to determine the chloride ions’ penetration of the geopolymers. The measurements revealed a strong dependence between chloride penetration through the concrete and the precursor composition.

Phosphorus and calcium compounds are present in the chemical composition of byproducts from coal and biomass combustion. They may have an influence on the microstructure and the mechanical properties through the specific bonds in polymeric aluminosilicates - geopolymers. Results proved that the 5% of CaO added to high-silica fly ash geopolymer increases material density and mechanical properties. Phosphate compounds available in the biomass fly ash have a negative effect on geopolymer mortars by increasing porosity and decreasing their compressive strength.

The construction sector should have much to offer in terms of helping to achieve circular economy goals, among others the use of waste materials. The example of such materials is biochar, a black porous and carbon-rich matter that could be converted from various waste biomass. A biochar could be utilized as microfiller in polymer concretes. This application of biochar is promising due to good interfacial bonding with polymer, no reactivity between surrounding polymer matrix and filler particles and fact that even fillers with irregular particles and large specific surface area could be utilized in polymer matrix. These create real opportunity to effectively dispose waste materials as a replacement of natural aggregates in polymer concrete technology. The presented paper is a second part of the research concerning the utilization of ecofriendly biochar in polymer composites conducted by authors. To better understand the impact of modification by biochar, already performed tests were supplemented by measurements of ultrasonic pulse velocity and quantitative analysis of microstructure.

In this paper, the volume fraction of polymer as a solid in the polymer cement mortar (PCM) is defined as the polymer content. The effect of the polymer content on the properties such as the flexural and compressive strengths, water permeability, carbonation and chloride ion penetration of PCM is discussed. As a result, the equation of the effective factor (F) for the properties of the PCM by using the water-cement ratio (W/C), polymer content (Vp), and volume fractions of air (Va) and sand (Vs) is established as “F = (1-W/C)(1 + AVp)(1-Va)(1 + 5Vs)”. The empirical constant (A) is the 4, -6, -8, -6 and -4 for the flexural strength, compressive strength, water permeability, carbonation depth and chloride ion penetration depth of PCM, respectively. The equation for estimating the properties of PCM by using the effective factor and the properties of cement mortar (Plain) is established as “PP = B(FP0) + C”. Where, PP, F, and P0 are the properties of PCM, the effective factor and the properties of Plain with the same W/C, sand-cement ratio and curing condition as the PCM. The empirical constants B and C in this equation are depending on the type of polymer used and curing condition.

This study investigates the effect of polymer paste content on the porosity and strength of pervious polymer concrete made of unsaturated polyester resin, fly ash filler, and crushed coarse aggregate. The porosity (total porosity and connected porosity) and strength (compressive and flexural strengths) for different polymer paste contents were investigated. The polymer paste content was chosen as an experimental variable because it determines the cost-effectiveness and has a significant impact on various material properties. The results showed that the total and connected porosity fell between 37.5–8.8% and 34.2–7.2%, respectively, when the polymer paste content increased from 7 to 19.5 wt.%. The porosity tended to decrease as the polymer paste content increased. The compressive and flexural strengths ranged from 14.5 to 41.5 MPa and 4.3 to 16.1 MPa, and the strengths increased as the paste content increased. In particular, the strengths were much higher than those of many existing studies on conventional portland cement concrete due to the enhanced adhesion of the polymer binder upon the addition of the cross-linking agent.

This investigation is focused on the observation of changes in the properties of polymer-modified cement mortars caused by the addition of recycled glass. The current requirements for reducing CO2 emissions in the production of cement composites, are also forcing the producers of polymer-modified mortars (PMMs) to use alternative materials, such as silica-rich supplementary materials. Selected types of recycled glass with pozzolanic behavior were specifically ground (particle size below 63 μm) and used as a partial cement substitute (10 wt.%, 20 wt.% and 30 wt.% substitution of Portland cement). In order to explain the obtained results and garner new knowledge of the microstructure of the mixtures being studied, the following tests were performed: scanning electron microscopy (SEM) observation, differential thermal analysis (DTA) and high-pressure mercury intrusion porosimetry. The findings show that the finely ground recycled glass has high potential to be used as an effective cement replacement for PMM materials, that are currently used in large amounts, mainly in the rehabilitation of concrete structures.

In the repair of the reinforced concrete structures deteriorated due to the chloride corrosion of rebars, it is desirable that the electrical resistivity of the patching repair mortar is equal to or lower than that of the existing concrete, considering the case of adopting the cathodic protection in the future. In general, cementitious patching repair mortars contain polymer components, which are thought to increase the resistivity, but there are also components other than polymer components that affect the resistivity. Such components without polymer include admixture components such as ground granulated blast furnace slag and fly ash, cement components such as ultra rapid hardening cement, and corrosion inhibitor components such as lithium nitrite. In this study, the effects of those components on the resistivity of cementitious patching repair mortars up to the age of 26 weeks are clarified. As a result, the electrical resistivity of cementitious patching repair mortar depends greatly on the types and amounts of their components.

Cellulose ether (CE) is widely used in cement-based materials because of its good water retention capacity that can improve the workability of the fresh mortars significantly. However, in the high temperature conditions, the CE modified cement mortars sometimes are easy to lose their good workability, which may be due to the change of the water-retention capacity of CE. This work investigates the changes in the water loss rate (WLR) of the CE modified calcium sulphoaluminate cement (CSAC) mortars at 20 ℃, 40 ℃, 60 ℃ and 80 ℃ respectively, and the effect of the types and contents of the CE was also considered. Additionally, isothermal calorimeter and 1H low-field NMR were carried out to monitor the changes of chemically bound water and CE adsorbed water content during the reaction. The results show that the WLRs of the CE modified CSAC mortars changes with temperature and the types and contents of the CE. These changes are mainly based on the fact that CE affects the state and relative contents of water molecules in mortar, and the microstructure of the CSAC mortars.

The paper discusses the possibilities of hydrophobization of cement screeds intended primarily for external thermal insulation composite systems. The hydrophobic character of the mixtures both with and without the addition of hydrophobic agents was investigated. The following hydrophobic agents were used: zinc and magnesium stearate, sodium oleate, two types of mixed product of stearates and oleates, micronized wax and a silane hydrophobic agent. The mixture containing 0.6% zinc stearate and 0.6% silane showed the lowest water absorption and high flexural and compressive strength. The microstructure of the selected mixtures was also monitored using a scanning electron microscope, where the pores covered with the layer of polymer admixture were observed.

Effect of aging conditions on the hydration and setting performance of cement paste with the addition of TEA were investigated through the combined techniques of calorimetry, Vicat test, XRD and TGA. It is found that, along with the increased aging time and RH, an obvious formation of AFt, AFm and CH can be found due to the pre-hydration of clinker. Besides, under the RH of 90%, the pre-hydration within the first day was significantly improved, and this process was continuously developed in the next 7 days through the strong carbonation of CH. Further analysis indicates that the pre-hydration can retard the cement hydration and increase the setting time of cement paste. Compared to the reference, a prolonged induction period and an increased setting time were observed for the aged samples with the addition of TEA. Besides, the commonly observed flash setting performance under the TEA dosage of 0.5 wt.-% was eliminated when the samples were pre-hydrated under 90% RH, which indicates the pre-hydration can alleviate the strongly accelerated aluminate phase hydration caused by TEA.

This study aims to overview the current state of concrete-polymer composite (CPC) applications and proposes ways to develop and generalize the use of CPC in practical applications. According to the literature, polymer-modified concrete (PMC) is mainly formulated using SBR or epoxy-based latex and used for repair and overlays. Polymer concrete (PC) uses unsaturated polyester resin as a polymer binder and is mainly used for precast products. Polymer-impregnated concrete (PIC) research was actively conducted in the 1970s and 1980s, but currently, it is not easy to find except for a few applied studies. This study also presents the challenges and suggestions for developing and generaling CPC use in real-world practice.

Recently, the deterioration and renovation of the aged bridges are urgent issue. Approximately 30% of more than 700,000 highway and road bridges in Japan have been in service for more than 50 years. The performance and function of them are required equal to be better than those at the beginning of construction and extend the service life. In addition to above, Japan is also a highly seismic country and there have been frequent damages of the bridges due to earthquakes. Therefore, securing the resilience of the bridges corresponding to robustness, redundancy, resourcefulness and rapidity is strongly demanded. In this study, the current status and practical countermeasures for the bridges to ensure the required performance and function, and to enhance the resilience using concrete polymer materials were investigated and discussed. Concrete polymer materials, which have high strength, high early strength development and high durability, are effective for repair and strengthening to sustain the current performance of structures. The main construction contents are as follows; It is a construction to replace the damaged reinforced concrete floor slab with a more durable floor slab. Treatment of joints of precast prestressed concrete slab is included. It is a construction to install high-performance floor slab waterproofing on the waterproof layer. In order to improve the durability of the bridge, it is a construction to attach reinforcing members to the girder. Seismic retrofit of concrete piers such as steel jacketing is one of main reinforcement technologies.

Sensors based on ion-conducting polymers are a reliable alternative to conventional metallic sensors. Formulated as 2K resin, they are quick and easy to install and cost-effective, so that larger sensor arrays with improved accuracy are affordable. The present systems are based on poly(ethylene oxide) or poly(propylene oxide) containing unsaturated polyesters doped with lithium perchlorate and are cross-linked on site with styrene. The curing reaction proceeds even at 0 ℃ and tolerates the presence of water. The best system in this series exhibits a resistivity of 194 Ω·m, which is several orders of magnitude lower than conventional polymers, but also several orders of magnitude higher than metals. The values are sufficient to accurately reproduce the progress of corrosion currents measured with conventional sensors and to detect changes in the humidity of concrete specimen.

New types of highly chemically resistant coating systems, mainly developed for concrete and metal substrates were subject to experimental testing and evaluation within the project. Secondary raw materials, including solidified hazardous waste (neutralization sludge (NS)), were used as microfillers. The three-layer polymer coating systems, applied using spray technology, were tested at two quality levels – one with a high content of solidification products, and the other with a low content. The microstructure of the epoxy coatings, including an observation of the degree of contamination of the polymer matrix, was investigated using scanning electron microscopy (SEM). It was demonstrated that the substitution of some of the primary filler with a solidification product does not result in the deterioration of the properties of the coating system, such as its adhesion to concrete or chemical resistance.

This paper presents an analysis of the mechanical properties of modified epoxy coatings used as epoxy floors. Waste mineral powder (limestone powder) was used as filler for the epoxy coating. Epoxy resin mixtures were made with waste limestone powder in amounts ranging from 0% to 29% of the mixture mass. Then, four mechanical properties were tested: hardness with the Shore D durometer, tensile and flexural strength with a standard testing machine, and pull-off strength by the pull-off method. The use of waste limestone powder as filler for epoxy coatings resulted in an improvement in hardness by 5%, does not significantly change the pull-off strength, but a deterioration of tensile strength by 6–27% and flexural strength by 18–38%. However, the modified epoxy coating still meets the standard requirements for epoxy floors. Therefore, waste limestone powder can be used in practice as filler for epoxy floor coatings. This solution allows the recycling of mineral powders, reduces the consumption of harmful epoxy resin and lowers the cost of the coating.

The most important factor for the protection of steel reinforcement in cementitious materials such as concrete is the alkalinity. As well as slowing down the penetration of atmospheric carbon dioxide, it delays to a certain extent the action of chloride ions. Both act at the molecular level in the form of discrete, individually mobile objects that can trigger steel corrosion. Therefore, maintenance materials designed to address these problems at the molecular level benefit from their own high pH value.To accomplish this an alkaline hydrogel based on diallyldimethylammonium hydroxide was developed which proved to be a multitool for modern building maintenance. The gel structure can be modified in order to tune macroscopic properties such as viscosity and stickiness relevant for applications. These are e. g. the restoration of the alkaline buffer of carbonated concrete, coupling material for the electrochemical chloride extraction, and crack injection, where the gel performs three functions simultaneously.

The paper describes an investigating into the application of a polymer concrete using a recyclable material such as polypropylene and chopped tire rubber as aggregate material to provide a durable and cost-effective alternative to the existing cold mix asphalt (CMA) pothole repair material. Three different aggregate mix designs, including traditional crusher- sand and -stone, rubber crumbs, and plastic chips, in combination with Vinyl Ester, Polyester, Polyurethane and Furan resin were combined to create 12 possible polymer concrete mixes to be used as a rapid pothole repair material. These polymer concrete mix designs were tested for common properties and characteristics typically experienced on road surfaces. These include characteristics such as compressive strength, flexural strength, and abrasion resistance. All results obtained from the various tests performed indicated that the polymer concrete mix designs exhibit enhanced physical properties compared with CMA and would thereby increase the durability and lifespan of repaired potholes when using this material.

The service life of corrosion-damaged reinforced concrete (RC) infrastructure can be improved through patch repairs and structural strengthening. However, the effect of varying corrosion damage and patch repair extent has not yet been clearly pronounced. The fatigue performance of corrosion-damaged RC beams that have been patch repaired to varying lengths and subsequently strengthened with carbon fibre-reinforced polymer (CFRP) laminates was evaluated by conducting four-point bending tests and cyclic load tests on simply supported beams. Three criteria were identified to evaluate performance: fatigue life, crack development and stiffness degradation. Various data acquisition techniques, such as neutral axis DEMEC strain targets, strain gauges, linear variable differential transducers (LVDT) and digital image correlation (DIC) were employed to investigate these performance criteria. The experimental results indicated that an increase in corrosion damage and patch repair extent lowered the ultimate static failure load and increased fatigue life. An increase in specimen stiffness was observed for the specimens with the longer damage extent compared to the specimens with the shorter damage extent, where stiffness was gauged in terms of midspan deflection, composite material strain and neutral axis shift. Moreover, the results yielded through the DIC process showed potential to identify potential failure locations, quite early in the specimen fatigue life by comparison of tangential strain, peak vertical deflection and the eventual failure location.

Carbon fibre reinforced polymers (CFRP) have emerged as an effective material for strengthening reinforced concrete structures. While many studies have been reported on CFRP strengthening of reinforced concrete elements subject to corrosion, there is a dearth of information on strengthening patch-repaired concrete elements. This paper reports on the experimental and numerical investigation of the behaviour of corrosion-damaged RC beams that have been patch repaired and strengthened with CFRP. Fifteen beams were cast; twelve of these were subjected to simulated corrosion of 5%, and the remaining three were used as control beams. The damage length was varied from 450 mm, 800 mm, 1300 mm and 1800 mm while keeping the depth of patch repair at 105 mm. All the CFRP-strengthened beams failed by intermidiate crack (IC) debonding. The control beams had a lower average crack density than the retrofitted beams. There was an increase in the average crack density for increasing damage lengths. Patch repair combined with CFRP strengthening retrofit method restored the damaged beams load carrying capacity but reduced the beams’ ductility compared to the control beams. The yield loads for patch repaired and strengthened (RS) results increased by 10%, 17% and 20% for beams with 450 mm, 800 mm and 1800 mm damage lengths, respectively. It was also observed that for increasing damage lengths; 450 mm, 800 mm and 1800 mm the peak loads increased by 13%, 20%, 20%, respectively. The experimental results correlated well with the finite element modelling (FEM) results.

This article presents a comparative analysis of the bond behavior of steel bars in concrete and bars made of basalt fiber-reinforced polymer (BFRP) and glass fiber-reinforced polymer (GFRP) in modified concrete. While steel bars have been the conventional choice for reinforcement in concrete structures, their bonding properties are well established. In contrast, FRP bars possess distinct mechanical and physical properties, which can lead to different bonding behavior in concrete. The study investigated the effects of concrete properties and bar characteristics on the bond behavior of GFRP and BFRP bars. Specifically, the study analyzed the relationships between bond stress-slip, modes and mechanisms of failure, and changes in bond strength of concrete with the addition of zeolite and metakaolin, with the presence of GFRP, BFRP, and steel bars. The findings of the study reveal that the adhesion of composite bars to modified concrete is enhanced to varying degrees. The bond stress of GFRP bars to concrete with metakaolin addition was found to be 50% higher than to normal concrete, while the bond stress to concrete with zeolite was similar. On the other hand, BFRP bars exhibited an increase in bond stress of 7% in the presence of concrete with metakaolin. Moreover, BFRP bars displayed a greater bond to steel reinforcement that underwent plasticization or rupture. The study also noted that the change in bond strength of GFRP and BFRP bars due to their linear deformability was gradual, characterized by a several times greater slip range compared to steel bars.

The FRP (Fiber Reinforced Polymer) bars are increasingly used as the main reinforcement of concrete structures, replacing traditional steel reinforcement. In this paper results of Basalt Fiber Reinforced Polymer bars (BFRP) modification by partial replacement of basalt fibers with carbon fibers were presented. The analysis of an effect of hybridization on a microstructure and mechanical properties of BFRP bars were performed. This analysis was thought out based on tests performed: tensile strength and shear strength and a microstructure observation with scanning electron microscope. The results obtained indicate that the hybridization effectively increases elasticity modulus compared to unmodified BFRP and the tensile strength and shear strength increase in lower extant. The nonhomogeneous distribution of carbon fiber in the cross-section of HFRP bars has relatively small effect of mechanical properties and their scattering.

Available studies on concrete structural parts with FRP reinforcement bars concern mostly investigations on bent elements (beams, slabs) [1, 2]. There are also available a few theoretical analyses on columns [3–5]. Though, there is still little experimental data concerning concrete columns with FRP bars [6–8], especially subjected to eccentric load, as also underlined in the review article [9]. This research aims to fulfill this research gap. Also, basalt FRP bars were chosen as relatively new type of non-metallic bars with low ecological impact [1].A total of eight columns with the height of either 750 mm or 1500 mm having 150 mm x 150 mm rectangular cross section were examined under axial or eccentric mechanical load up to 290 kN. Columns were reinforced with four BFRP main bars with the diameter of either 8 or 10 mm, and 8 mm steel stirrups in each case. The results on the thermal and mechanical properties’ investigations on BFRP bars were presented in [10]; the compressive strength values of the used BFRP bars were in the range of 441.2–466.8 MPa and elasticity modulus at compression values were equal to 31.0–38.4 GPa. Tested compressive strength of concrete, from which all columns were made (in one concrete pouring) were equal to 33.8 MPa. Each column was loaded in three cycles of loading-unloading, increasing the eccentricity, from 0 to 2 cm, and finally to 4 cm. DIC (Digital Image Correlation) method was used for the analysis of crack propagation (as in earlier research of bent elements [11]), but also unexpectedly there were visualised intensification areas of compression micro-damages. Failure was noted for two elements - B075_8_2 at the eccentricity of 4 cm (failure load – 290 kN after 60 s of sustained load) and B150_10_2 at the eccentricity of 4 cm (280 kN). Other specimens did not fail under load up to 290 kN. Maps from DIC method were also compared with results from numerical modelling (in Abaqus software) with good resemblance.

The work analyzes the serviceability ultimate limit state of 4.5 m long fiber-reinforced concrete beams with basalt bars and stirrups (BFRP). On the basis of previous tests, deformations in beams with composite reinforcement are above acceptable values. Beams were made of concrete with basalt fibers to improve deformability, cracks resistance and deflection. The tests showed that the load capacity of beams reinforced with BFRP bars was lower than that of beams with steel reinforcement, resulting from different failure mechanisms of both beams. The failure of beams with BFRP reinforcement was rapid. Deformations in the concrete were reduced by using basalt fibers in the concrete. Increasing the stiffness of the structure with reinforcement with BFRP bars and stirrups using concrete with basalt fibers can meet the SLS requirements for limiting the deflection and cracking of concrete elements reinforced with them.

The article presents the results of experimental studies of reinforced concrete beams on the shear without transverse reinforcement strengthened by the FRCM system. For the implementation of the research, four experimental samples were designed and manufactured, with cross-sectional dimensions of 200x100 mm and a length of 2100 mm. The beams are designed in such a way that even after strengthening the support areas, the failure occurs due to the shear force. None of the samples is destroyed by the bending moment. The tests were carried out according to the authors’ improved methodology, by testing each sample twice. The samples were strengthened by the FRCM composite system at load levels of 0, 0.3, and 0.5 of the bearing capacity of the control samples. Reinforced concrete beams were strengthened by gluing P.B.O. fabrics in the form of vertical strips with a width of 70 mm, for the possibility of fixing the concrete strains in the support areas. Samples strengthened by the FRCM system are destroyed more smoothly and plastically than unstrengthened beams, and there is no mass fallout of concrete particles. According to the obtained data, graphs of the strain distribution in support area and the isofield of their distribution were constructed. In accordance with the results of the research, the maximum effect of the composite system use for the shear reinforcement was established by 26…57%. With increasing the load level at which the sample is strengthened, the effect of the strengthening decreased.

In cementitious composites, an application of various fibers can contribute to endow a controlled crack propagation, moderated brittle failure, superior tensile strength and higher energy absorption capacity. Fiber-matrix bonding properties play a key role in fiber strengthening efficiency and the final mechanical performances of the reinforced matrices. This is true specifically for high-performance polyethylene (PE) fibers which yield very high tensile strength and modulus of elasticity, but do not interact properly with cementitious matrix due to their inert hydrophobic surface lacking functional groups.In the presented work, PE fibers are functionalized by using fast tannic acid modification technique to enhance the bonding properties between a cementitious matrix and the fibers. Environmental scanning electron microscopy (ESEM) confirmed the presence of polymer coating layers on the fiber surfaces. Micromechanical tests indicated that the modified fibers considerably improved the maximum fiber pullout force, interfacial shear strength and pullout work in comparison with the reference fibers. This enhancement in bonding properties could be traced back to the created functional layer on the PE surface triggering a better interaction with cement hydrates as well as a rougher surface enhancing fiber-matrix mechanical interlocking at interfaces. Overall, the introduced approach can be applied for different fibers to promote their bonding behavior with cementitious matrices resulting in an enhanced fiber reinforcing effect in composites.

Foamed concrete is known as lightweight or cellular concrete. It is commonly defined as a cementitious material with a minimum of 20% (by volume) mechanically entrained foam in the mortar mix where air-pores are entrapped in the matrix by means of a suitable foaming agent. Although the foamed concrete has been patented in 1923, it is mainly used as a filling or leveling material. The use of foamed concrete has been limited e.g. for backfilling retaining walls. As a material used in contact with the ground, it is a relatively new material. In order to use foamed concrete in road construction as a replacement for hydraulically bound mixtures, the improvement of foamed concrete was considered. The article presents the two different type of polypropylene reinforced of foamed concrete. Polypropylene fibers with content of 0.3 kg/m3 and 6.37 kg/m3 were used. For foamed concrete samples with addition of 6.37 kg/m3 PP fibers, the splitting tensile strength increased. In second case, the polypropylene geotextiles with weight 150 g/m2, 200 g/m2 and 500 g/m2 were used. It can be observed that flexural strength for foamed concrete reinforced with geotextile samples was higher compared to the base (unreinforced) foamed concrete sample. On this basis, the suitability of using reinforced foamed concrete in the road pavement-subsoil system was determined.

The paper discusses the use of Polypropylene Fiber Reinforced - Latex Modified Mortar (PFR-LMM) for installation of granite paving blocks (GPBs) on various road sections in Slovenia. The following four examples are considered: two inner rings of roundabouts on both sides of the bridge over the Sava River on the bypass near Krško, a roundabout in front of the entrance to the Šoštanj thermal power plant and one part of a street in Ljubljana. GPBs were installed on a slab made with Steel Fiber Reinforced Concrete (SFRC). The workability of the fresh PFR-LMM had to be such that it filled the joints between the GPBs. Hardened PFR-LMM, however, must provide a good bond between the GPBs to ensure resistance to traffic loads and resistance to constantly changing weather and temperature influences. The age of the subject applications is between 5 and 11 years.

In this paper, we present and discuss the initial results of a large-scale research project involving laboratory and field investigations of abrasion resistance of different types of concrete. The decision to study in more detail the abrasion resistance of fibre-reinforced concrete with granulated rubber was based on the results of previous research projects, as well as on observations on the behaviour of concretes placed in the spillways of hydro power plants loaded with water and water-borne particles. Gravel aggregate, steel, polypropylene fibres, and granulated rubber were used to prepare the concrete. In the fibre-reinforced concretes without granulated rubber, the binding component consisted of cement and silica fume, but when granulated rubber was added, the binding component consisted of cement and a dry proportion of SBR latex. The results obtained by now, at an age of 90 days show that fibre-reinforced concretes with granulated rubber have an improved resistance to underwater abrasion, compared to fibre-reinforced concretes without granulated rubber.

This study introduces the design and realization of a fast-setting technology for an efficient industrial production of a novel mineral-impregnated carbon-fiber (MCF) reinforcements for the building sector. By employing mineral-based matrices for carbon fiber (CF) reinforcements, numerous advantages can be achieved, including high temperature resistance, cost-effectiveness, reliable bonding with concrete substrates, and enhanced flexibility in automated processing.This study focuses on the impact of different thermal curing regimes for the forming process of the MCF composite. The fabrication process involves commercially available raw materials and the utilization of a continuous pultrusion line, followed by oven heating at temperatures of 50 ℃ and 75 ℃ for short durations. The purposefully designed impregnation suspension allowed a sufficient long-lasting processing window at the early age. Extensive experimental investigations have been conducted to examine the development of the resulting MCF performance and the implementation of the MCF as reinforcement in GP concrete at varying temperature levels.

In the present paper the results of uniaxial compression tests conducted on textile reinforced concrete (TRC)—confined reinforced concrete (RC) columns are reported. By confining the column with TRC, the lateral expansion of the concrete can be impeded. The resulting multiaxial compressive stress state allows to enhance the components axial capacity. Due to the corrosion-resistant textile, the usual concrete cover in reinforced concrete construction is reduced, which allows slender but at the same time highly load-bearing components to be created. Consequently TRC provides a sustainable, environmentally friendly and lighter option for column reinforcement due to the material savings. The aim of this study is the investigation of various influences on the achievable strengthening effect. The impact of ratio of textile reinforcement and the applied fine grain concrete jacket is evaluated. In addition, the influence of the concrete strength of the strengthened component on the overall increase in load-bearing capacity was investigated. With the help of experiments on TRC reinforced RC columns with a circular cross-section mechanical property and constraint mechanism under uniaxial compression were documented and analyzed. Based on the test results, stress distribution and failure mechanisms of the reinforced specimens is studied. Furthermore, stress-strain relationship of strengthened members is investigated. The results show an increasing in both strength and ductility related to the unstrengthened reference columns. The specimens with a lower compressive strength can achieve a higher degree of reinforcement. A high ductility of the reinforced columns could also be observed.

Polymer-modified cement mortars (PCM) and concretes (PCC) are mainly used in concrete repair and restoration exhibiting improved durability, suitable chemical resistance, and beneficial adhesion strength compared to unmodified cementitious materials. Due to these favorable properties, the material is increasingly implemented in construction. Commonly, the modifiers applied to cementitious binders consist of thermoplastic polymers, which feature a change in the deformation behavior under the influence of different temperatures. Despite the distinct temperature-dependent properties of the polymers, the load-dependent deformation behavior of PCM and PCC was barely investigated within a service temperature range. To make statements about the effect of polymers on the load bearing and elastic deformation behavior of PCM and PCC, the engineering properties of the material have to be experimentally assessed under thermal conditioning. Accordingly, the compressive and flexural strength as well as dynamic and static modulus of elasticity of seven different PCM mixtures were characterized while the specimens were exposed to service temperatures of −20 ℃, 20 ℃, and 60 ℃. After the specimens were thermally conditioned in a climate chamber, the samples were transferred to the equally conditioned test machine and tested in the proposed temperature scope. The experimental results reveal influential changes in all tested mechanical attributes for the modified system within the applied service temperature range compared to an unmodified reference. This knowledge is essential to further investigate the temperature impact on the material and develop appropriate prediction models for the application of polymer-modified cementitious materials in construction and the integration in design guidelines.

For the purpose of developing a repair material that contributes to decarbonization, a basic study is conducted on an alkali activated material that does not require an alkaline solution. Thin study is characterized by the use of sodium orthosilicate as an alkaline source in order to achieve powder premixing, be ultra rapid hardening. Specifically, a basic study on ultra rapid hardening property and an improvement of the length change performance of the material using only ground granulated blast furnace slag were carried out. As a result, it was clarified that sufficient compressive strength at 3 h can be achieved by increasing the alkaline usage rate, and that the length change performance can be improved by using shrinkage reducing agents and expansive agents.

The building sector faces a challenge to find innovative and sustainable ways to increment the energy-efficiency of buildings and reduce their environmental impact. Recently, the incorporation of phase change material (PCM), based on a polymeric active phase (PEG-1000) in waste stone aggregates, has proven to be a promising option to be used for building restoration. Mortars that include PCM aggregates demonstrated to have favorable thermal properties, that would lead to a reduction of energy requirement for heating/cooling needs. However, the inclusion of aggregates impregnated by PEG causes a reduction in the mechanical properties of the mortars possibly due to (i) a lack of compatibility between aggregate and binder, or (ii) a problem with the confinement of the PEG, causing its dispersion in the mortar. Therefore, the aim of this study was to investigate the causes associated to the reduction of the mechanical properties and propose a method to prevent it. Preliminary results showed that, given its high water solubility, the PEG 1000 included in the stone aggregates tends to be washed away when these aggregates are incorporated in the mortar mixture. This hypothesis was confirmed by FTIR spectroscopy. Therefore, an additional confinement method using a layer to coat the stone aggregates impregnated by PEG 1000 was proposed in this study. Different materials were tested as coating layer: powder calcium hydroxide, milk of lime (suspension of Ca(OH)2 in water), pozzolana, and cocciopesto. Carbonated mortar samples using the proposed coated aggregates were, then, analyzed using FTIR to evaluate the efficiency of this encapsulation methodology. Preliminary results suggested a relevant improvement in terms of PEG confinement.

The exposure of polymer concrete to artificially designed environmental conditions of high-and low-temperatures, and moisture levels allowed for the assessment of strength performance and aesthetic value. Strength performance indicated the maximum capability of the product to carry a load successfully, whereas the aesthetics assessed the appearance of the product, that can be measured using spectrophotometry. In this study, materials such as water and Portland cement typically used to form traditional concrete were replaced by two polymer resins namely - vinyl ester and polyester, thus making it polymer concrete. As such, compressive strengths of cube samples were tested, the change in cubes’ masses was measured using a balance - prior and post exposure to the artificially induced environments, the colour change tests (spectroscopy analysis) were performed using the spectrophotometer tests. Compressive strengths of over 75MPa were achieved, thereby justifying promising concrete strengths. Mass losses recorded were almost negligible, thereby showing toughness to conditions presented in the artificially induced environments. Minor colour changes were noticed- thereby showing a good resistance to harsh weather conditions on the surface properties. Therefore, the assessed products displayed desired characteristics for strength performance and aesthetic value, subsequently, creating a product that promotes sustainability.

The floors made of epoxy resin coating that are exposed to the thermal loads are usually not durable enough to be used in industrial facilities. To enhance thermal properties of the coating recycled fine aggregate was used to reduce thermal expansions in the interphase zone in between the coating and substrate. Three different types of coating were analyzed: pure epoxy, specially homogenous, and functionally graded material. The top floor was loaded with temperature to obtain heat flux and strain results. Finite element method was used to simulate the heat transfer and heat load. Simulations show that sedimentation of the aggregate reduces heat flow to the substrate during loading. It means that properly designed aggregate can improve durability of the industrial floor which can be more resistance to thermal gradient.

Cracking in engineering concrete structures poses a significant problem as it not only accelerates the rate of deterioration but also diminishes the structural strength. The current repair materials being used are capable of short-term repairs only and may result in destroying the concrete structure due to additional damage. In this study, Carbon nanotube (CNT)-Epoxy concrete is proposed as a sensing repair material to address this problem. The authors assess the electrical properties of samples based on the CNT content and aggregates and report on the optimal mixing ratio of CNT-Epoxy concrete. The electro-mechanical characterization of CNT-Epoxy concrete was evaluated through a series of experiments such as static and cyclic loadings. CNT-Epoxy concrete exhibits accurate sensing response under compression and maintains a consistent cyclic response. The findings from the study demonstrate that CNT-Epoxy concrete is an effective material for repairing concrete cracks, offering favorable compressive strength, and showing reliable sensing ability.

In the current era, sustainability has gained significant importance within the field of civil engineering. The promising technology of 3D printing for cementitious materials addresses the mentioned challenges. This study provides a briefly overview of the sustainable approach to 3D printed concrete, covering both technological and material aspects. The paper presents a thorough analysis of the essential properties of 3D printed concrete from a sustainable perspective. Specifically, the composition of binders and aggregates is examined in relation to sustainable development. In case of technological aspects various research studies have demonstrated that the mentioned aspects of 3D concrete printing have the potential to achieve a minimum reduction of 50% in CO2 emissions. Furthermore, modifying materials can help protect natural resources from depletion, and the use of alternative binders can further reduce CO2 emissions. The findings presented in this work pave the way for new directions in future research endeavors.

The increasing interest in 3d printing of concrete for infrastructure applications necessitates having a design for this process. Previous research has mostly focused on 3D printable cement-based concrete mixes, with less attention given to 3D printed polymer concrete (PC). PC is a concrete type that uses polymer instead of cement as a binder. It offers improved compressive and tensile strengths, crack resistance and bond strengths, and superior durability than traditional Portland cement concrete, making it an excellent material for 3D printing. This study aims to understand the evolution of the early-age mechanical properties of fresh polymer concrete and its potential failure during printing. Unconfined uniaxial compression and direct shear tests were performed on fresh polymer concrete for the first 110 min after mixing to determine the evolution of mechanical and failure characteristics with time. Such characteristics include compressive strength, modulus of elasticity, cohesive strength, and friction angle. A time-dependent early-age Mohr-Coulomb failure envelope is established to describe the mechanical and failure behavior of 3D printed polymer concrete.

Currently it is necessary to give a new direction to the construction sector, making it essential to change the way that buildings are constructed and rehabilitated, with the aim of obtaining a construction with greater sustainability value. To minimize energy consumption, it is important to take advantage of renewable energy sources like solar power. Phase change materials (PCM) can help reduce building energy consumption due to their energy storage capacity. PCM has been studied in different solutions for walls, ceilings, and floors, essentially using encapsulation techniques. The use of PCM in building materials has social, environmental, and economic benefits, including increased thermal comfort, decreased energy consumption from non-renewable sources, and reduced air conditioning needs and costs. The development of cement boards incorporating PCM brings a new option for the thermal improvement of buildings, which can be used in new buildings and rehabilitation operations. The main objective of this study was the development of cement boards with the incorporation of pure and free PCM, through direct incorporation, consisting of a simple, low-cost, and very promising incorporation technique. The results showed that the technique was easy to use in manufacturing cement boards for interior coatings of building walls and ceilings. It was also possible to observe a decrease in the water/cement ratio with the incorporation of PCM and a consequent decrease in the porosity, which resulted in a slight reduction in its mechanical strengths, without ever compromising the necessary performance for its function.

A possible solution to reduce the consumption of fossil fuel and energy demand to power heating and cooling devices is represented by Phase Change Materials (PCMs). They can absorb, store and release energy according to their physical state that changes with the environmental temperature. In this work, novel eco-sustainable PCMs were developed through the form-stable method. Through this process, it was possible to create composite PCMs consisting of a natural inert matrix (i.e., a very porous stone obtained from processing waste) and an eco-friendly polymer, i.e., Poly-Ethylene Glycol (PEG). The composite PCMs were used to replace aggregates in mortars based on different binders (i.e., hydraulic lime, and cement). A complete characterization was performed on the new PCMs assessing their thermal stability and thermal efficiency. The study of the properties of the PCM-based mortars, in their fresh and hardened states, allowed to identify those with suitable mechanical properties. These latter were, then, subjected to a further investigation to assess their thermal behavior in response to different climatic loads. Encouraging results were achieved that allowed to establish the effectiveness of the novel PCMs in thermo-regulating an indoor environment.

Heavy-weight concretes are known for their high unit weight inherited from the aggregates and developed mainly for radiation shielding. Therefore, minimal porosity besides the high unit weight is a desired property. Numerous particle-packing theories were put forward to decrease the porosity by an ideal reference curve; modified Andreassen model based on the size distribution of ingredients to adjust the fineness. This research investigates the effect of the mentioned method on heavy-weight mortars. Cement, micro and nano silica combinations, and their polymer additive mixtures were used as binders in the specimens, along with barite and finely ground magnetite aggregates. In this work, the aggregate size limit selected 3 mm and the fineness factor of q was chosen as 0.22 and 0.25, depending on the mixture. To achieve a self-levelling consistency, the w/c ratio was kept constant at 0.40, and a superplasticizer was added to maintain the workability. Consecutively, the specimens were examined for unit weight, compressive strength, and capillary water absorption. The collected results were analyzed, and the difference between groups was compared according to their composition.

The aim of the paper is to evaluate neutron shielding efficiency of ordinary concrete, heavy-weight concrete and geopolymer concrete modified with epoxy additive. Evaluation was based on neutron shielding efficiency calculations. Since the commonly used fast neutron effective removal cross-section calculation does not take into account thermal neutron absorption reactions, a method adopted from the fast neutron effective removal cross-section calculation based on the macroscopic cross-section calculation for compositions is therefore applied. The results confirmed that an efficient neutron shield requires a balanced mixture of light and heavy nuclei and polymer modification is a proper way for increasing neutron shielding efficiency.