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The environmental aspects of sustainable development in the construction industry involve the utilisation of secondary raw materials in the design and construction of new structures. This study aims to conduct a critical review of previous literature on the use of olive waste ash (OWA). The use of OWA in concrete helps create and maintain sustainable and greener development. Published literature has confirmed the huge potential of using olive biomass ash (OBA) as replacement for a small portion of natural fine aggregate as admixture or reinforcement. The main goal of this development is to reduce carbon dioxide emissions, which cause environmental pollution and climate problems, and support the reuse and exploitation of the waste concept. This study also aims to examine the effect of OBA on concrete properties, such as workability, setting times, soundness, compressive strength, flexural strength, shrinkage and durability, as well as its impact on sustainability. Furthermore, information regarding microstructure in terms of scanning electron microscopy is provided in this work. This study is considered the first review paper to investigate the utilisation of olive-stone biomass ash on construction materials. It also contains recommendations and observations for future research in this field. This study is important for international research as it provides a comprehensive overview of the potential of using OWA as a sustainable alternative in the construction industry and can inform future developments in this area.

The possibility of application for lignin, a byproduct of paper and pulp production, as a partial replacement for cement in producing mortars and concretes is presented. Initially, mortars were prepared with substitution rates ranging from 0.0% to 50.0% to determine the best rates for subsequent application in concretes. Statistical analysis showed that the rates with the highest potential for application in concretes were 2.5%, 5.0%, and 10.0%. After preparing the concretes, test specimens were molded and subjected to axial compression, splitting tensile strength, water absorption by immersion, void ratio, and capillary water absorption tests after the curing period. The results showed that lignin, in rates higher than 5.0%, led to decreased mechanical strength; however, all concretes with lignin significantly reduced capillary water absorption, which can lead to greater material durability. [ABSTRACT FROM AUTHOR]

Fly ash (FA) and exhausted bed sands (sands wastes) that are generated in biomass burners for energy production are two of the wastes generated in the pulp and paper industry. The worldwide production of FA biomass is estimated at 10 million tons/year and is expected to increase. In this context, the present work aims to develop one-part alkali-activated materials with biomass FA (0–100 wt.% of the binder) and sands wastes (100 wt.% of the aggregate). FA from two different boilers, CA and CT, was characterized and the mortar's properties, in the fresh and hardened conditions, were evaluated. Overall, the incorporation of FA decreases the compressive strength of the specimens. However, values higher than 30 MPa are reached with 50 wt.% of FA incorporation. For CA and CT, the compressive strength of mortars with 28 days of curing was 59.2 MPa (0 wt.%), 56.9 and 57.0 MPa (25 wt.%), 34.9 and 46.8 MPa (50 wt.%), 20.5 and 13.5 MPa (75 wt.%), and 9.2 and 0.2 MPa (100 wt.%), respectively. The other evaluated characteristics (density, water absorption, leached components and freeze–thaw resistance) showed no significant differences, except for the specimen with 100 wt.% of CA. Therefore, this work proved that one-part geopolymeric materials with up to 90 wt.% of pulp and paper industrial residues (FA and sand) can be produced, thus reducing the carbon footprint associated with the construction sector. [ABSTRACT FROM AUTHOR]

The study aims to increase the efficiency of mortar mixes and improve their necessary qualities such as strength, density, and durability by using wastepaper as a cement substitute in the form of wastepaper sludge ash (WPSA). Mortars with 20, 25, and 30% cement replacement were tested. Due to less use of cement and greater usage of WPSA, CO2 and SO2 emissions can be reduced. The chemical properties of WPSA were compared to those of Ordinary Portland Cement (OPC). Testing showed that WPSA had similar cementitious properties. Results demonstrate the potential applications of this mortar in a variety of settings where increased toughness and equivalent characteristics are needed while still preserving the environment. [ABSTRACT FROM AUTHOR]

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Due to the urgent need for a more sustainable built environment and actions against climate change, this paper presents a literature review about photocatalytic TiO2-based thin layers to be applied on mortars in facades. Photocatalysis may be a potential strategy against current environmental and climate challenges by transforming or eliminating hazardous greenhouse gases from the atmosphere. The main subjects researched were the coatings' efficiency (which encompassed their self-cleaning ability, depolluting effect, and antimicrobial properties), durability, and sustainability. The method was based on the systematic literature review approach. Self-cleaning ability was the most recurrent topic retrieved from published studies, followed by depolluting effect and durability. There are few investigations about antimicrobial properties considering TiO2-coated mortars in facades. However, sustainability studies through Life Cycle Assessment and Life Cycle Costing represented the most significant gap, even requiring broader surveys. The photocatalytic activity of the coatings is well-proven in the literature, although specific evaluations may be needed for each coating composition and testing condition to understand their performance. The type of contamination agents, TiO2 dispersion and characteristics, dopants, nanocomposites, and substrate are among the principal agents influencing the results; therefore, caution must be taken when comparing research. Mainly, adhesion and photocatalytic efficiency after ageing were studied on durability. More field exposures may be recommended. Regarding the trade-offs concerning the environmental impacts of TiO2-based coatings, it is urgent to clarify whether their overall outcome is indeed advantageous and to investigate their resilience regarding climate change scenarios. [ABSTRACT FROM AUTHOR]

Additive manufacturing by 3D printing has emerged as a promising construction method offering numerous advantages, including reduced material usage and construction waste, faster build times, and optimized architectural forms. One area where 3D printing's potential remains largely unexplored is in combination with lightweight materials, especially lightweight gypsum. This research paper explores the potential of combining 3D printing technology with lightweight gypsum-based composites to extend the relatively limited gypsum application possibilities in the construction industry. The study investigates the use of expanded polystyrene (EPS) beads as an aggregate in gypsum composites, focusing on the printability of the mixture and hardened state mechanical properties in various print directions. Mechanical tests reveal that 3D printing can reduce the compressive strength of the EPS–gypsum composite by between 3% and 32%, and the flexural strength by up to 22%, depending on testing direction. However, the technology opens up new production possibilities for applications where such strength can be sufficient. The study describes that a slight increase in the water-to-gypsum (W/G) ratio in 3D-printed mortars enhances homogeneity and reduces porosity, resulting in improved structural uniformity and therefore higher flexural and compressive strength values. Furthermore, the paper discusses the mechanical anisotropy observed in 3D-printed samples. The combination of 3D printing technology and lightweight gypsum offers the potential for sustainable construction practices by reusing waste materials and creating lightweight, thermally and acoustically insulative, as well as architecturally diverse building components. [ABSTRACT FROM AUTHOR]

The growing concern about environmental pollution and the depletion of resources has led to a focus on the use of more sustainable materials. In light of this, the recycling and use of agricultural wastes is highly advanced and sought-after in the concrete technology field. Yearly, an enormous quantity of date palm waste (DPW) is produced, putting stress on the ecosystem and necessitating an urgent disposing method. For this reason, many researchers are looking into the feasibility of incorporating DPW for cement composites in an effort to improve the performance and sustainability of concrete. The use of DPW in the design of concrete and mortar mixes has a significant effect on both the fresh and hardened properties of the resulting composites. This paper reviews the basic information on the types and characteristics of DPW used in previous studies. In addition, the potential inclusion of DPW and its effect on cementconcrete performance are reviewed. This study further highlights the areas that need additional investigation for adopting these waste materials. This will advance academic research and benefit the sustainability of the construction industry. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue on cement and concrete chemistry, focusing on advances in knowledge, experimental studies, seismic assessment, and the application of artificial intelligence in the field. The article discusses the use of concrete as a widely used construction material and its dependence on cement, which contributes to CO2 emissions. The global Sustainable Development Goals challenge the concrete construction sector to reduce its environmental impact while maintaining structural safety. The article also highlights recent advancements in technology and research in the field of concrete structures, such as the use of recycled materials and the development of alternative cement solutions. It further explores various topics related to concrete structures, including the chemistry of cement, non-destructive testing methods, foundation design, fiber-reinforced cement mortar, retrofitting interventions, seismic design, strengthening interventions, and the use of waste materials in concrete production. The aim is to promote a sustainable future for concrete structures. The research presented highlights the importance of sustainable and environmentally friendly practices in the construction industry and emphasizes the need for ongoing research and innovation in cement and concrete technology. [Extracted from the article]

The importance of compatible restoration of historic masonries cannot be overemphasized, as it helps maintain the historic structures for sustainable development, economic growth, and the representation of a country's history. This paper acknowledges the existence of extensive research work on historic mortar characterization, the proposition of restoration materials, and the awareness raised about the use of incompatible restoration materials. However, the concept of historic mortar characterization still faces some challenges in methodology, material sampling, and mortar decay that need to be confronted. The problem extends further to designing and producing compatible restoration mortars for historical monuments. The work has not been extended to evaluate the compatibility and durability of the designed mortars. This creates uncertainty about the effectiveness of such proposed solutions. These could be overcome by analyzing the physical, chemical, mineralogical, and mechanical properties of the original representative mortar samples collected from historic structures and the proposed repair mortars before executing repairs. It is believed that investigations into the mix designs help achieve successful restoration work. This review presents the recent advances in historic mortar characterization and is intended to be a useful tool for historic restoration teams when tackling conservation activities on historic masonries. [ABSTRACT FROM AUTHOR]

The oyster shell is a residue rich in calcium carbonate, which can be reused as a raw material for creating building materials. For this reason, many researchers focused on the incorporation of oyster shell in the composition of composites, as it is a means of contributing to the economic sustainability by reducing the presence of pollution caused by aquaculture waste in the environment, thus increasing the value chain of the construction sector and reducing its carbon footprint. This paper intends to systematize the scientific production related to oyster shell-based composites in construction, carrying out a search using the Scopus tool and a systematic review based on the PRISMA statement. The results show that research on the incorporation of oyster shell into cementitious mortar mixtures, with a focus on its use in concrete, dominates existing scientific research. There is a lack of studies on the incorporation of the oyster shell that address its application as an aggregate or binder in the composition of coating and laying mortars. Most existing research is from Asia, and there is a lack of research in some parts of Europe. In the Americas, Africa and Oceania, no existing studies were found. Despite the growing understanding of the importance of sustainability and economic issues related to products used in the blue circular economy sector, there are still few studies that consider the incorporation of waste or by-products of aquaculture. Future investigations that cover these practical and contextual gaps can contribute to the better use of oyster shell waste and its insertion in the blue circular economy. [ABSTRACT FROM AUTHOR]

Researchers have been driven to investigate sustainable alternatives to cement production, such as geopolymers, due to the impact of global warming and climate change resulting from greenhouse gas emissions. Currently, they are exploring different methods and waste materials to enhance the mechanical and physical properties of geopolymer and expand its application range. This review paper offers a thorough analysis of the utilization of various waste materials in geopolymer manufacturing and shows the creative contribution of this research to the development of environmentally friendly cement substitutes. The article covers the properties, durability, and practical applications of geopolymer composites made from various waste binders. It includes a microstructure and chemical analysis. The research findings indicate that geopolymers are an effective cementitious binder substitute for cement in various applications. Additionally, the ecological and carbon footprint analysis highlights the sustainability of geopolymers compared to cement. [ABSTRACT FROM AUTHOR]

In the construction industry, cement is the most widely used material. So, to achieve greater sustainability in this industry, it is imperative to improve the sustainability of this material. One way to reduce the ecological footprint of cement is to replace it, even if partially, with other more sustainable materials that can act as binders. This paper analyses the mechanical properties of more sustainable mortars containing recycled cement (RC), fly ash (FA), and magnesium oxide (MgO). Different types of binary, ternary, and quaternary mortars were used: containing recycled cement (5% and 10%), fly ash (10% and 20%), and MgO (7.5% and 15%). An experimental campaign was carried out analysing air content, density, compressive and flexural strengths, modulus of elasticity, and ultrasonic pulse velocity. The ternary mortars showed decreases between 0.4% (M-5RC10FA) and 35.3% (M-10RC15Mg) in terms of compressive strength at 365 days (compared to RM), when the theoretically expected decrease (the sum of the decreases obtained with the individual incorporation of these materials) would be between 16.6% and 41.5%, respectively. The results obtained allow for concluding that the joint use of these materials in ternary mortars improves the mechanical capacity, relative to the individual incorporation of each material in binary mortars. [ABSTRACT FROM AUTHOR]

In the past decades, nanomaterials have become one of the focal points in civil engineering research. When added to cement-based construction materials (e.g., concrete), it results in significant improvements in their strength and other important properties. However, the final mix characteristics depend on many variables that must be taken into account. As such, there is no general consensus regarding the influence upon the original material of certain nano-sized additives, the optimum dosage or the synergistic effect of two or more nano-materials. This is also the case for titanium dioxide (TiO2) and nanoclay (NC). The paper focuses on reporting the existing research data on the use of the above-mentioned materials when added to mortar and concrete. The collected data is summarized and presented in terms of strength and durability properties of cement mortar and concrete containing either TiO2 or NC. Both nano-materials have been proven, by various studies, to increase the strength of the composite, at both room and elevated temperature, when added by themselves in 0.5%~12% for TiO2 and 0.25%~6% for NC. It can be inferred that a combination of the two with the cementitious matrix can be beneficial and may lead to obtaining a new material with improved strength, elastic and durability properties that can be applied in the construction industry, with implications at the economic, social and environmental levels. [ABSTRACT FROM AUTHOR]

Existing buildings are often in need of strengthening interventions, and several technical solutions have been recently developed for this purpose. Among them, the use of textile-reinforced mortar (TRM) composites has gained consensus as a technically viable and economically convenient option. Moreover, TRM has the potential to be employed as a reversible and sustainable strengthening technique for masonry buildings. In this context, the present paper aims to investigate the mechanical properties of TRM systems consisting of sustainable phases, such as lime-based matrices and natural fabrics produced by waiving fibers obtained from plants, such as Jute or Flax. This class composite system can be referred to as natural TRM and is denoted by the acronym NTRM. The present study moves from the geometric and mechanical characterisation of fibres and fabrics and, after having also investigated the properties of the mortar, it reports the results of tensile tests carried out on specimens of the NTRM systems under consideration, with the main aim of providing the empirical bases of the relationships between the geometric and physical properties of the constituents and the resulting mechanical response of the composite system. The obtained results show that the considered Flax-TRM system has an apparent composite behavior, as its response to tension is clearly characterised by the well-known three stages corresponding to the elastic response, the formation of cracks, and the reinforcement response up to rupture. Conversely, the Jute-TRM system needs to be further improved in terms of balance between the properties of the matrix and the internal reinforcement. Further studies will be devoted to this specific aspect and, more generally, to investigating the relationships between constituents' properties and the NTRM behavior. [ABSTRACT FROM AUTHOR]

Bentonite, a supplementary cementitious material for Portland cement, has greatly contributed to environmental sustainability. However, few studies have investigated mortar samples produced by substituting bentonite for cement, and cement strength may be adversely affected when cement is replaced with bentonite in larger proportions. Therefore, this paper investigates and discusses the effect of microbially induced calcium carbonate precipitation (MICP) on improving the strength of bentonite-amended cement. The bio-mineralization process of MICP was characterized by SEM-EDS, while the biominerals formed in bentonite-amended mortar were identified by FIIR and XRD analysis. The results showed that: at bentonite concentrations of 0%, 10%, 20%, 30%, and 40% in cement, the bacterial suspension and reaction solution enhanced the compressive strength of bentonite-amended cement by 17%, 20%, 79%, 78%, and 38%, respectively, after 28 days, compared to control specimens; With the increased bacterial concentration in the presence of the reaction solution, the strength of the bentonite-amended cement (20% bentonite) increased remarkably compared to the control specimen (without bacteria). When the bacterial concentration was OD600 2.0, the compressive strength of bentonite-amended cement (20% bentonite) increased by 80% after 28 days; MICP process has a great effect on improving the strength of bentonite-amended cement. It is a green and economical choice to use MICP to improve the strength of bentonite-amended cement. [ABSTRACT FROM AUTHOR]

Building envelopes coated with TiO2-based mortars benefit from depolluting, antibiological and self-cleaning effects. Therefore, photocatalytic renders are allies in the quest for sustainability in the built environment, potentially combatting atmospheric pollution, enhancing durability and reducing maintenance needs. Surface finishing characteristics of the renders influence their photocatalytic efficiency and esthetic and functional properties. In this context, this study reviews the existing literature, focusing on proven surface-affecting parameters, the surface and color of TiO2-based mortars, to explore their impacts on photoactive behavior. The incorporation of TiO2 within an additional surface layer and its mixture into the mortar in bulk were observed for surface roughness. Mainly the addition of TiO2 during casting was identified in colored mortars. Generally, a moderate surface roughness led to better photoactivity; microroughness affected self-cleaning by facilitating dirt deposition. The interaction between the surface roughness and the photocatalytic layer affected the water contact angle, regarding superhydrophilicity or superhydrophobicity. The photoactivity of colored mortars with TiO2 depended on the color and amount of the added pigments, which influenced electron–hole recombination, physically occupied active sites or, on the other hand, led to a higher formation of reactive radicals. Surface finishing can thus be designed to enhance the photoactivity of TiO2-based mortars, which is fundamental for current climate concerns and emphasizes the need for life cycle assessments and environmental protection. [ABSTRACT FROM AUTHOR]

Alkali-activated binder (AAB) is a product with lower carbon footprint and has great potential to be an alternative to Portland cement in civil construction. In this study, one-part AAB has been synthesized by mixing alternative sodium silicate powder, obtained from rice husk ash (RHA) and metakaolin (MK). The main objective was to verify the effect of MK (two types were used with different reactivity characteristics) and water content on the mechanical properties of pastes and mortars produced with the one-part AAB. Some tests were conducted (e.g. setting times, flexural and compressive strengths, elastic modulus) and the results indicated that the MK type and the water content directly affect different properties. As expected, the decrease in water content decreased the workability of the mortars and improved the mechanical strength. A more reactive MK provided an increase in compressive strength higher than 60%. The results confirm the possibility of producing an alternative sodium silicate powder from RHA dissolution, that when mixed with MK, results in AAB with acceptable compressive strength. This paper reveals that with the correct materials and a good mix design, the properties of this eco-friendly AAB can be considerably improved. [ABSTRACT FROM AUTHOR]

By 2050, approximately 43 million tons of wind-turbine blade (WTB) waste materials will have accumulated, emphasizing the critical importance of effective waste management strategies for WTBs at the end of their life cycle to ensure sustainability. Comparing current WTB waste management methods, reuse emerges as a highly-sustainable method that can also serve as a sustainable solution to environmental challenges, including global warming and natural resource depletion associated with civil engineering activities. This paper presents a comprehensive review of sustainable solutions for reusing WTB waste materials in civil engineering applications. Repurposing WTB waste materials as structural elements in housing, urban furniture, recreational facilities, and slow-traffic infrastructure can be a viable option. WTB waste can also be utilized in powder, fiber, and aggregate forms as an eco-friendly material for construction and pavement (e.g., mortar, concrete, asphalt) to replace cement and natural resource aggregates while meeting necessary strength and performance standards. Through a detailed analysis of reusing WTB waste materials, economic and environmental challenges are also discussed. According to the findings, the properties of mortar, concrete, and asphalt can be affected by the type, shape, and content of fibers, polymers, and impurities present in the blades, as well as the cutting direction. Furthermore, while reuse is considered a sustainable end-of-life (EoL) option for WTB waste management from both economic and environmental perspectives, further research is required to fully understand the environmental consequences of this method. • Innovative sustainable solutions in wind turbine blade waste materials utilization in civil engineering applications. • Exploration of economic and environmental considerations. • Exploring challenges in wind turbine blade waste materials utilization. [ABSTRACT FROM AUTHOR]

This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability. [ABSTRACT FROM AUTHOR]

Recycling fly ash (FA) and furnace bottom ash (FBA) help with reducing greenhouse gas emissions, conserving natural resources, and minimizing waste accumulation. However, research on recycling FBA is progressing more slowly compared to FA. This research aims to investigate the combined use of FBA as a replacement for both fine aggregate and cement and its influence on the performance of mortar. The findings indicated that incorporating 25% FBA as a fine aggregate replacement and 10% or 20% ground FBA (GFBA) as a cement replacement significantly enhanced compressive strength after 28 and 56 days. Flexural strength was comparable to control mortar at 28 days and superior at 56 days. However, increasing the FBA content beyond 25% as a fine aggregate replacement reduced workability and increased porosity, which negatively affected mechanical performance and water absorption. Microstructural analyses revealed denser and more compact structures in the mortar with combined FBA replacement for both fine aggregate and cement, specifically 25% as a fine aggregate replacement and 10% and 20% as cement replacements. Optimal performance was noted in mixtures with Ca/Si and Ca/Al ratios within the ranges of 1.8–1.5 and 0.24–0.19, respectively. Trace element leaching analysis has not shown significant differences between GFBA, FA, and OPC. Regarding environmental impact assessment, using FBA as a fine aggregate replacement did not show a significant reduction in CO2 emissions, but replacing cement with FBA reduced emissions remarkably. Generally, using FBA as a replacement for both fine aggregate and cement in mortar enhances compressive and flexural strengths at optimal levels, promotes sustainability by reducing landfill waste and CO2 emissions, and supports cleaner production practices despite some workability challenges. [ABSTRACT FROM AUTHOR]

From past decades since Joseph Davidovits introduced geopolymer, this innovative green technology as alternative for cement mortar have been studied and proven its strength, effectiveness, and potential to many applications. Likewise, crack proneness due to lack of reinforcement, occurrence of efflorescence and curing methods are issues on geopolymer. This paper focused on the effects of treated banana fibres (BF) using 4 % sodium hydroxide (NaOH) soaked within 2, 4 and 6 h which served as reinforcement on the geopolymer mortar with different parameters to eliminate macro cracks and two curing methods were used to address efflorescence. Fiber reinforced geopolymer mortar (FRGM) can lessen the massive utilization of conventional construction materials due to sustainability of geopolymer and provide crack bridging in the matrix. Compressive and split tensile strength test of geopolymer cube and cylinder samples for burlap and saran wrapped method of ambient curing were determined using universal testing machine (UTM). The flowability, weight loss of samples during curing period and the occurrence of efflorescence were observed as well. In Design Mixture - 1 (DM1), there are 13-design mixtures (DM) with 5 - 50x50x50 mm cubes and 5 -100x200 mm cylinder specimens each reinforced with BF while 8 DMs for DM1 are plain geopolymer mortar (PGM) to obtain the mixture with the highest compressive and split tensile strength for both FRGM and PGM. FRGM and PGM with the highest mechanical strength are further explored reinforcing with treated and untreated BFs. Mechanical strengths, flowability, efflorescence and weight loss of samples were recorded. The optimum FRGM shows that there is no significant difference in compressive and split tensile strength when reinforced with 4 % NaOH treated within 2 and 6 h compared to 4 h of treatment which has the highest strengths. Finally, the governing BF with 4 % NAOH treated within 4 h was used to reinforce the PGM to investigate the strength variation provided by BFs which gave up to 22.43 % increment in terms of compressive strength. [ABSTRACT FROM AUTHOR]

This study presents an innovative approach for the utilization of industrial by-products and municipal waste in the production of sustainable and environmentally friendly cement mortar. We explored stabilized stainless-steel reduced slag (SSRS) and polyethylene (PE) plastic waste as partial replacements for aggregates. Various engineering properties of the resulting cement mortar specimens, including the slump, slump flow, compressive strength, flexural strength, tensile strength, water absorption, and ultrasonic pulse velocity (UPV), were investigated through comprehensive experimental tests. The influence of different water–cement (w/c) or water–binder (w/b) ratios and substitution amounts on the engineering properties of the cement mortar samples was thoroughly examined. The findings revealed that an increase in PE substitution adversely affected the overall workability of the cement mortar mixtures, whereas an increase in the SSRS amount contributed to enhanced workability. As for the hardened properties, a consistent trend was observed in both cases, with higher w/c or w/b ratios and substitution amounts leading to reduced mechanical properties. Water absorption and UPV test results validated the increased formation of porosity with higher w/c or w/b ratios and substitution amounts. This study proposes a promising method to effectively repurpose industrial by-products and municipal waste, transforming them into sustainable construction and building materials. Additionally, a comparative analysis of the transportation costs and carbon footprint emissions between SSRS–cement mortar and PE–cement mortar was conducted to assess their environmental impact and sustainability. Generally, higher w/c or w/b ratios and replacement levels corresponded with a reduced carbon footprint. The geographical location of the source of SSRS and PE remains a challenge and studies to overcome this challenge must be further explored. [ABSTRACT FROM AUTHOR]

The construction industry strives for sustainable solutions to tackle environmental challenges and optimize resource use. One such focus area is the management of industrial byproducts and waste materials, including fugitive dust control through wheel washers. While wheel washers play a pivotal role in dust management, they generate a challenging byproduct known as wheel washer sludge (WWS). The disposal of WWS is complicated due to its composition and potential hazards. Recent research explores reusing WWS in construction materials, particularly in repair mortar, aiming for sustainability and circular economy principles. This study investigates the incorporation of WWS into repair mortar formulations, evaluating mechanical properties, durability, and environmental implications. Results show that WWS enhances workability but prolongs setting time. Mechanical strength tests reveal improvements with WWS addition, especially when pretreated. Water absorption rates decrease with pretreated WWS, indicating enhanced durability. Chemical attack tests demonstrate resistance to carbonation and chloride penetration, especially with modified WWS. Freeze–thaw tests reveal improved resistance with WWS addition, particularly modified. Microstructure analysis confirms hydration products and denser matrices with WWS inclusion. Environmental hazard analysis shows WWS contains no harmful heavy metals, indicating its suitability for use in repairs. Overall, this study highlights the technical feasibility and environmental benefits of incorporating WWS into repair mortar, contributing to sustainable construction practices. [ABSTRACT FROM AUTHOR]

This study investigates the alkali-silica reaction (ASR) and mechanical properties of mortars containing crumb and powder rubber instead of river sand. In this regard, mortars were produced using waste rubber whose ratios in the mixture are 0%, 3%, 6%, 9%, 12%, 15%, 18%, and 21%. ASR expansion, compressive and flexural strength tests were conducted on the samples. ASR measurements were performed on days 3, 7, 14, 21, and 28. Besides, at the end of the ASR experiment, the microstructures of the mortars were examined using scanning electron microscope (SEM) images. Examining the results of this study reveals that the use of waste rubber in rising portions in the mortars led to an increase in the ASR expansions of the mortars. The study shows that the ASR expansions of the mortar samples that have 9% and 15% waste rubber replacement are comparatively higher than the other mortar samples. Furthermore, the results of the SEM analysis verified this finding. The study demonstrates that 3% of waste rubber mortar samples have the highest compressive and flexural strengths. On the other side, the ASR expansion of the mortars with 3% substituted waste rubber was considerably low compared to other mortars containing waste rubber. These findings (ASR, compressive and flexural strength tests results) show that using 3% waste rubber is ideal for producing mortars and supports a sustainable production approach in the sector. [ABSTRACT FROM AUTHOR]

Innovation in construction plays a fundamental role in helping us face current challenges, namely the reduction in energy consumption, the mitigation of the effects of climate change, the depletion of resources, and the generation of waste. Regarding the built environment, improving the thermal properties of the building envelope is one of the growing needs to reduce energy consumption in the building sector. In this context, thermal mortars have been a trend in the construction industry in recent years due to their ability in reducing heat transfer through the building envelope. On the other hand, the addition of waste has been studied as an alternative to improve the thermal properties of mortars and reduce the consumption of primary materials in the construction sector. This work aims to carry out a detailed review regarding the incorporation of waste in thermal mortars through the application of scientometric data analysis and a systematic literature review. To this end, the different residues incorporated into thermal mortars and the various percentages and forms of incorporation were identified throughout the publications gathered in this review. The most studied properties regarding the thermal mortars with the addition of waste were also the subject of study. A comprehensive database of thermal mortars with the incorporation of waste is presented, in which the objectives of the studies, the wastes and forms of incorporation and the measured properties are highlighted. The main results of the analysed researches are deeply discussed and the gaps in this area of the knowledge are identified to point out new directions and possible perspectives for future studies in the field of thermal mortars incorporating waste. [ABSTRACT FROM AUTHOR]

This research presented, for the first time, the results of the successful application of the waste press sludges, WSLP (plant for lacquer and paint) and WSEP (powdery enamel plant), from a wastewater treatment plant generated during heating device production in the construction industry. The results of WSEP characterization and its influence on cement paste, mortar, and concrete properties showed that this material could be used as a cement replacement (with a maximum replacement amount of 20%) in producing mortar and concrete. Although waste WSLP sludge does not possess pozzolanic properties and does not meet the criteria prescribed by the standards for application in mortar and concrete due to its chemical inertness and fineness, as well as its extended setting time, it can be used as a replacement for stone filler or other powdered mineral admixture in the production of self-compacting concrete (SCC) in amounts up to 100%, with a maximum quantity of up to 100 kg/m3. The obtained results indicate that with the appropriate conversion, waste sludges, despite representing hazardous waste, can be used as safe products in the construction industry; i.e., the waste material can become a useful and valuable raw material by applying (respecting) all of the principles of the green economy. [ABSTRACT FROM AUTHOR]

Over the past two decades, extensive research has been conducted to explore alternative supplementary cementitious materials (SCMs) in order to address the environmental concerns associated with the cement industry. Bricks, which are frequently preferred in the construction sector, generate a lot of waste during the production and demolition of existing buildings, requiring environmentally sustainable recycling practices. Therefore, many studies have been carried out in recent years on the use of brick waste as supplementary cementitious materials (SCMs) in cement mortar and concrete production. This critical review evaluates the impact of waste brick powder (WBP) on the mechanical and durability properties of mortar and concrete when used as a partial replacement for cement. It was observed that the properties of WBP-blended cement mortar or concrete depend on several factors, including WBP particle size, replacement ratio, pozzolanic activity, and mineralogical structure. The findings indicate that WBP with a particle size range of 100 µm to 25 µm, with a maximum cement replacement level of 10–20%, exhibits a positive impact on the compressive strength of both mortars and concretes. However, it is crucial to emphasize that a minimum curing duration of 28 days is imperative to facilitate the development of a pozzolanic reaction. This temporal requirement plays a vital role in realizing the optimal benefits of utilizing waste brick powder as a supplementary cementitious material in mortars and concretes. [ABSTRACT FROM AUTHOR]

This document discusses the use of waste and recycled materials in civil engineering applications, specifically in the production of mortar, concrete, ceramic, and other building materials. The research presented in this special issue covers various aspects of construction and the environment, including the properties of materials produced from waste and recycled materials, methods for removing excess fluorine from waste, and the influence of different additives on the physical and mechanical properties of concrete. The articles in this issue include research conducted in multiple countries around the world, highlighting the global interest in sustainable construction practices. The document concludes by expressing gratitude to the authors and reviewers for their contributions to the field of building materials engineering. [Extracted from the article]

Mineral geopolymer binders can be an attractive and more sustainable alternative to traditional Portland cement materials for special applications. In geopolymer technology the precursor is a source of silicon and aluminium oxides, the second component is an alkaline solution. In the synthesis of geopolymer binders the most commonly used alkaline solution is a mixture of sodium or potassium water glass with sodium or potassium hydroxide or silicate solution with a low molar ratio, which is more convenient and much safer in use. In this paper, we present the influence of sodium or potassium silicate solution on the physical and mechanical properties of fly ash and ground granulated blast furnace slag-based geopolymer mortars. Mercury intrusion porosimetry and microstructural observation allowed for comparing the structure of materials with a different type of alkaline solution. The evolution of compressive and flexural tensile strength with time determined for composites using 10%, 30% and 50% slag contents (referring to fly ash mass) was analysed. The tests were performed after 3, 7, 14 and 28 days. It was observed that, as the amount of slag used increases in the precursor, the strength of the material grows. Mortars with the sodium alkaline solution were characterised by a higher strength at a young age. However, the values of strength 28 days were higher for geopolymers with potassium alkaline solution reaching 75 MPa in compression. Geopolymer mortar microstructure observation indicates a high matrix heterogeneity with numerous microcracks. Matrix defects may be caused by the rapid kinetics of the material binding reaction or shrinkage associated with the drying of the material. [ABSTRACT FROM AUTHOR]

The natural aggregate crisis is an alarming concern for the construction industry worldwide. This study provides a detailed investigation of coal mine overburden (OB) from opencast mine dumps, to evaluate its potential as a sustainable alternative to natural aggregate. The microproperties, including mineralogy, morphology, and chemistry, were evaluated, and the macroproperties, including alkali–aggregate reaction, soundness, durability, flow value, ultrasonic pulse velocity, and other mechanical properties of crushed OB, OB-based mortar, and concrete, were determined. OB was found to be mineralogically more stable (55%–77% SiO2), mechanically comparable, and durable (volume change 3%–8%) than other alternatives of natural aggregate. The toxicity characteristic due to leaching was found to have no hazardous effects on local and regional soil and water quality. The cement mortar prepared using OB had similar performance in terms of fresh and hardened density, flowability (>0.6 w/c), and durability [slake durability index (SDI) >95% ] as other industrial by-products. The compressive strength of the mortar with OB was found to be comparable to that of mortar with river sand. OB-based mortar and concrete were found to have good corrosion resistance. For bulk utilization of OB, a pilot-scale study is recommended to assess its performance under real-world exposure conditions. [ABSTRACT FROM AUTHOR]

A sustainable future is required for precast concrete structures, and the reuse of concrete elements will be an essential part of the solution. Design for disassembly is currently conducted with costly and time-consuming mechanical joints. Now, mortar joints with much weaker mortar types are proposed for new buildings, enabling easier disassembly by new methods: removal by direct pulling and removal by use of a system of flat jacks. Different weak mortar types were tested in the lab to achieve the properties required to check the transfer of wind loads and the level of resistance to separation during disassembly. Using a modelled case study building, the results showed that weak lime cement-based mortars had the required properties to substitute regular cement-based mortar in joints between slabs and a stabilising wall during a critical wind load. Regarding disassembly, pulling concrete slabs out with a mobile crane would be possible if hydro demolition systems could be implemented to remove parts of the mortar joint beforehand. Using a system of flat jacks to push the slab apart showed that the method's weakness was the punching failure of the thin wall to the hollow cores. Solutions were proposed to overcome the challenge. [ABSTRACT FROM AUTHOR]

Due to the COVID-19 epidemic, biomedical waste management has overwhelmed both developed and developing nations. It is now a critical issue that has to be addressed with minimal possible adverse impact on the environment. This study introduced a technique of recycling face masks into polypropylene fibers for use in concrete. This proposed recycling process provides complete disinfection of contaminated clinical waste and offers the opportunity to transform the characteristics of an end product. Microfibers manufactured from recycled medical masks were subjected to testing. According to the results, polypropylene is the primary component of this research program. Two batches of concrete were made, one with the inclusion of masks as polypropylene fibers and another that performed as a control mix. The modified mortar was compared to the control mix in split tensile, flexure, compressive strength, and water absorption. Compressive strength was found to be improved by about 17%, and tensile strength to be increased by around 22% when mask fibers were incorporated. This research introduced a novel approach for disposing of waste masks and established the preliminary viability of upcycling trash face masks towards mortar concrete production. [ABSTRACT FROM AUTHOR]

This study investigated the impact of using cow dung ash (CDA) as a partial replacement for ordinary Portland cement (OPC) in mortar. Mortar mixes are prepared by replacing OPC with CDA at varying levels: 5%, 10%, 15%, 20%, 25%, and 30%. The chemical composition of CDA shows that it is composed primarily of SiO2, Al2O3, and Fe2O3, with a significant amount of loss of ignition. The workability, hardened properties, and microstructure of CDA-containing mortars are also analyzed. The increasing CDA content in mortar reduces workability and, beyond 5%, it causes high water absorption due to CDA's porous nature and unremoved organic compounds. This impacts the density and compressive strength of the hardened mortar as well as compromising its homogeneous characteristics. When using 5% CDA, the bulk density and compressive strength of the mortar are comparable to those of the control mixes. Nonetheless, as the proportion of CDA increases, both the bulk density and compressive strength of the mortar diminish. The thermal stability of mortar mixes with 10%, 20%, and 30% CDA is unaffected at temperatures between 500 °C and 600 °C. The Fourier-transform infrared spectroscopy (FTIR) analysis reveals the presence of unreacted particles and wide stretched C–S–H gels in the mortar samples. In general, the results suggest that CDA can be utilized as a substitute for OPC at a ratio of up to 10% in the manufacturing of mortar and can serve as a feasible alternative cementitious material. [ABSTRACT FROM AUTHOR]

This work presents a technical and economic study using sugar cane bagasse ash (SCBA) to partially replace Portland cement clinker. To evaluate the technical viability, the replacement rates of 10, 20, and 30% of Portland cement were used in the experiments. The ashes used were in the following conditions: (i) as collected (AC), (ii) ground (G), and (iii) re-burnt and ground (RG). Three composition parameters were used in the mortar mix procedures: (i) mix with water factor/fixed binder in volume, (ii) mix with water factor/fixed binder in weight, and (iii) mix with the fixed flow. After the technical feasibility analysis, the benefit of the substitutions and an analysis of the relationship between cement consumption and the acquired compressive strength, correlating with possible economic costs, were discussed. SCBA AC was not suitable for the partial replacement of Portland cement clinker. SCBA G presented a satisfactory performance and SCBA RG was the ash that presented the best performance in the partial replacement of Portland cement clinker. For the same levels of compressive strength, the consumption of Portland cement per cubic meter of concrete reduced; from this, the cost of concrete and mortar could be reduced by 8%, with the ash having the same value as cement. Furthermore, the use of SCBA RG at 30% inhibited the alkali–silica reaction (ASR) in concretes with a reactive basalt and quartzite aggregate. SCBA G (20 and 30%) and SCBA RG (10 and 20%) inhibited the ASR in concretes with a reactive basalt aggregate and reduced the expandability in concretes with a reactive quartzite aggregate. Another point to highlight was the durability shown by the cements with SCBA, which, 900 days after the accelerated test of expansion by the alkali–aggregate reaction, maintained high levels of flexural strength when compared to the results obtained before the accelerated test of expansion. The present work concluded that using sugar cane bagasse ash to replace Portland cement is feasible from a technical, environmental, and economic perspective. [ABSTRACT FROM AUTHOR]

In order to study the mechanical and microstructural properties of masonry mortar, combined particles of cockle and scallop seashell wastes were incorporated and analysed through destructive and non-destructive tests. River sand was replaced with the combined seashell particles (SPs) at seven mixes, viz., 0, 5, 10, 15, 20, 25, and 30% with a 0.5 constant water-to-cement ratio (W/C). A mortar mix design of M4-type of BS EN 1996-1-1 was adopted with a target compressive strength of 5.17 MPa at 28 days. The physical, chemical and mineralogy properties of the SPs were analysed through BS standard sieving, X-ray fluorescence (XRF), scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods. The hardened SP-based mortars were subjected to direct compressive strength, rebound hammer, ultrasonic pulse velocity tests, and nonevaporable degree of hydration analysis. The XRF, SEM, and XRD analysis results of the SPs showed over 86% calcium oxide content, irregular and needle-like particles, and hydroxyapatite/calcium silicates, respectively. The direct compressive strength and the non-destructive test results revealed that up to 30% sand replacement with SP in masonry mortar, an improvement of 45% compressive strength could be attained over the control sample. The nonevaporable water method of the degree of hydration analysis showed that after 28 days, hydration increased considerably for the SP-blended mortars over the control, especially the SPM-30 with 30% sand replacement. Therefore, the study concludes that the investigated SPs in blended masonry mortar could benefit an eco-friendly environment and conservation of natural resources. [ABSTRACT FROM AUTHOR]

The main focus of this research was the bio-stimulated healing of cracks in lime mortar samples (historical and newly designed). The investigation started from comprehensive characterisation of historical mortars, while in the next stage a compatible conservation mortar was designed and characterised, with special attention given to the contact zone formation between original and conservation mortars. The next step was the design of a bio-stimulating crack-sealing agent, a two-component liquid system: bacteria culture Sporosarcina pasteurii DSM 33 and nutrients. Both historical and conservation mortar samples were used in order to study their potentials for bio-stimulated surface-crack repair. The experiment lasted for 150 days, allowing the ureolytic bacteria Sporosarcina pasteurii DSM 33 to induce the precipitation of calcium carbonate into cracks and heal the damaged surface of the tested materials. The healing phenomenon was continuously monitored during a period of 150 days. Special attention was given to the evaluation of the morphology, chemical and structural characteristics of the deposits created in/on the surface cracks, monitored by optical microscopy, SEM, XRF and XRD analyses. The obtained results present valuable input for the application of the developed system in real environmental conditions as a solution for the future sustainable architectural conservation of traditionally prepared mortars. [ABSTRACT FROM AUTHOR]

In this study, the production of a mortar was proposed in which plastic waste replaced sand by 0%, 50%, and 100% in order to create a sustainable alternative for construction. The performance of the mortars was tested with two types of activators, one with NaOH, as a simple activator, and the other with NaOH and Na2SiO3, as a compound activator. The effects of the LDPE plastic bag waste and the activators on compressive strength, porosity, microstructure analysis, and efflorescence formation were correlated and discussed. The results showed that the replacement of sand with plastic waste at 50% and 100% proportionally reduced the compressive strength due to the increase in porosity caused by the waste, especially in the group of mortars with the simple activator, and included the formation of efflorescence. On the other hand, the compound activator increased the packing of the particles in the mortar, as observed in the images of the microstructure. This reduced porosity inhibited efflorescence and resulted in higher resistances that reached a maximum value of 22.68 MPa at 28 days in the group of 50% mortars with the compound activator. Therefore, the study showed that there is potential for the replacement of sand with plastic waste for the production of mortars, which can be considered a more sustainable building material. [ABSTRACT FROM AUTHOR]

This work proposes sustainability criteria for the selection or design of restoration mortars based on their physical and mechanical properties, durability, price in the French market, and the environmental impact estimated by the global warming potential. A score is assigned to the mortars based on normalized values of their physical and mechanical properties. A total of 24 formulations of restoration mortars were characterized, and their scores were compared. A case study showing the application of the proposed selection method is presented, focused on the restoration of historical monuments in Paris, France, built with Lutetian and Euville stones. In this case, hydraulic lime mortars were the most sustainable options. The application of the method is also projected for global application, as showcased for the restoration of Mayan stones in Southern Mexico. [ABSTRACT FROM AUTHOR]

The oyster shell is a residue rich in calcium carbonate, which can be reused as a raw material for creating building materials. For this reason, many researchers focused on the incorporation of oyster shell in the composition of composites, as it is a means of contributing to the economic sustainability by reducing the presence of pollution caused by aquaculture waste in the environment, thus increasing the value chain of the construction sector and reducing its carbon footprint. This paper intends to systematize the scientific production related to oyster shell-based composites in construction, carrying out a search using the Scopus tool and a systematic review based on the PRISMA statement. The results show that research on the incorporation of oyster shell into cementitious mortar mixtures, with a focus on its use in concrete, dominates existing scientific research. There is a lack of studies on the incorporation of the oyster shell that address its application as an aggregate or binder in the composition of coating and laying mortars. Most existing research is from Asia, and there is a lack of research in some parts of Europe. In the Americas, Africa and Oceania, no existing studies were found. Despite the growing understanding of the importance of sustainability and economic issues related to products used in the blue circular economy sector, there are still few studies that consider the incorporation of waste or by-products of aquaculture. Future investigations that cover these practical and contextual gaps can contribute to the better use of oyster shell waste and its insertion in the blue circular economy.

This study assesses the effect of mix design parameters on the fresh and hardened properties, cost, and carbon footprint of geopolymer mortar made with desert dune fines (DDF) and blast furnace slag (BFS). Taguchi method was employed in designing the experiments. Four factors were considered, each having three levels, leading to a total of nine geopolymer mortar mixes. The factors comprised the DDF replacement percentage, alkali-activator solution to binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), and sodium hydroxide (SH) molarity. Ten performance criteria were evaluated, including the flowability, final setting time, hardened density, 1, 7, and 28-day compressive strengths, water absorption, sorptivity, cost, and carbon footprint. ANOVA was carried out to estimate the contribution of each factor towards the response criteria. Further, TOPSIS analysis was utilized to optimize the mixture proportions of DDF-BFS blended geopolymer mortar. Experimental results showed that up to 25% DDF replacement enhanced the density, strength, and durability of the geopolymers with minor impact on the flowability and setting time. Higher replacement percentages had a detrimental impact on the performance but could still be utilized in specific mortar construction applications. The other factors had more limited contributions to the performance, evidenced by the ANOVA. TOPSIS method revealed the optimum mix to be made with DDF replacement of 25%, AAS/B of 0.5, SS/SH of 1.5, and SH molarity of 10 M. Different multivariable regression models were also developed to predict the fresh and hardened properties of the DDF-BFS geopolymer mortars using the mix design parameters. [ABSTRACT FROM AUTHOR]

Renders should have an adequate resistance to impacts, since they must protect the substrate. The use of fibres may enhance the energy absorbed when the mortars are submitted to an impact load, which contributes to postpone the first crack, and control its propagation and width. In this study, the impact strength was measured by a falling mass from different heights. The cracking pattern and the impact energy for the appearance of the first crack and until failure were evaluated. An artificial accelerated ageing test was also performed, and the impact resistance was analysed before and after ageing. In order to analyse the effects of recycled fibres, wool, coir, flax and textile-acrylic waste fibres were used as reinforcement in cement and cement-lime mortars. The results indicated that the fibres' addition significantly improved the impact energy of the rendering mortars in comparison with the reference mortars. Concerning the crack patterns, the recycled fibres prevented the opening or the growth of the cracks, before and after ageing. This effect is mainly due to the fibre's bridge mechanism, due to crossing the open cracks and hindering their propagation. The fibres' type, length and volume fraction have influenced the mortars' performance in terms of impact resistance. Textile-acrylic fibres waste presented the best performance by comparison with the natural fibres used. [ABSTRACT FROM AUTHOR]

The valorization of industrial waste is a hot topic toward circular economy and sustainability. Several wastes have been proposed as resources for different production processes; however, others are still disposed to landfill or waste-to-energy plants. For the first time, this work suggests a sustainable alternative to managing cork waste from bottle caps manufacturing; this is generated by a local company at about 220,000 m3/year. The powder waste has a 0.063–1 mm particle size and is mainly composed of cork, polyurethane adhesive, and paraffin. Its valorization is proposed as filler in construction materials such as lime-based mortar (1–4 wt%) and polyurethane (5–15 wt%). Thermal, spectroscopic, and physical characterizations are performed on the cork waste, and mainly result in a low apparent density (340 kg/m3) and high-water absorption (177%). Cork properties allow consideration of extra water in the mortar mix and improve lightness without significantly affecting compressive, bending strength, and thermal insulation. Cork waste in polyurethanes promotes a color change, slightly increases the density (up to 12.5%), and still results in producing a thermally insulating material (<0.06 W/mK). Considering the promising results, this study demonstrates the feasibility of using the manufacturing waste from cork bottle caps to produce green construction materials, thus upgrading it from waste to secondary raw material. [ABSTRACT FROM AUTHOR]

Traditional precast reinforced concrete structures are characterised by joints of individual components executed with the use of cement grouts or mortars, or by welding reinforcement. The joints produced in this way cannot be demounted in the case of need without damaging the precast components. Demountable precast structures with a long life cycle enable repeated assembly and demounting thus contributing to the saving of the basic input resources and the environment. The main feature of demountable precast structures are patent-protected joints which allow the assembly of the precast components without the necessity of using "wet" processes. The article addresses the characteristics of a demountable girder - column joint. It presents the results of static load tests carried out within extensive experimental research. To conclude, the article specifies the benefits and the applications of demountable structures. [ABSTRACT FROM AUTHOR]

Due to the urgent need for a more sustainable built environment and actions against climate change, this paper presents a literature review about photocatalytic TiO2-based thin layers to be applied on mortars in facades. Photocatalysis may be a potential strategy against current environmental and climate challenges by transforming or eliminating hazardous greenhouse gases from the atmosphere. The main subjects researched were the coatings’ efficiency (which encompassed their self-cleaning ability, depolluting effect, and antimicrobial properties), durability, and sustainability. The method was based on the systematic literature review approach. Self-cleaning ability was the most recurrent topic retrieved from published studies, followed by depolluting effect and durability. There are few investigations about antimicrobial properties considering TiO2-coated mortars in facades. However, sustainability studies through Life Cycle Assessment and Life Cycle Costing represented the most significant gap, even requiring broader surveys. The photocatalytic activity of the coatings is well-proven in the literature, although specific evaluations may be needed for each coating composition and testing condition to understand their performance. The type of contamination agents, TiO2 dispersion and characteristics, dopants, nanocomposites, and substrate are among the principal agents influencing the results; therefore, caution must be taken when comparing research. Mainly, adhesion and photocatalytic efficiency after ageing were studied on durability. More field exposures may be recommended. Regarding the trade-offs concerning the environmental impacts of TiO2-based coatings, it is urgent to clarify whether their overall outcome is indeed advantageous and to investigate their resilience regarding climate change scenarios.

Featured Application: Substitution of 17 wt.% of Ordinary Portland Cement by biomass fly ash in the formulation of a commercial screed mortar. Substitute Ordinary Portland Cement (OPC) by biomass fly ash (BFA) reduce the environmental impact produced by cement-based materials, and at the same time, decreased the economic and environmental burden associated with the landfilling of this waste. This study aims to evaluate the recycling of BFA as supplementary cementitious materials (SCMs) in a commercial screed mortar formulation. Two BFA varieties, both resulting from fluidized bed combustion of forest residues, were used to replace 17, 50, and 67 wt.% of OPC. The influence of simple pre-treatment processes of the BFA, such as sieving and grinding, in the fresh and hardened state properties of the mortars, was evaluated. The BFAs were characterized in terms of chemical (XRF) and mineralogical (XRD) composition, particle size distribution (laser diffraction-COULTER) and morphology (SEM). The prepared formulations were characterized in terms of workability, mass loss upon curing, bulk density, sorptivity (by immersion and capillary), flexural and compressive strength and durability to 25 freeze–thaw cycles. Both of the BFAs are potential SCMs. Substitution of 17 wt.% OPC with BFA complied with the product technical requirements for compressive and flexural strength (10 and 3 MPa, respectively), with the ground and sieved and just sieved BFAs perform slightly better than the as-received BFA. [ABSTRACT FROM AUTHOR]

The present work aims to define the mechanical behavior of a new composite material for the preservation and enhancement of the vast historical and architectural heritage particularly vulnerable to environmental and seismic actions. The new composite represents a novelty in the landscape of the fibrous mortars and consists of natural hydraulic lime (NHL)-based mortar, strengthened by Sisal short fibers randomly oriented in the mortar matrix. The developed mortar ensures the chemical-physical compatibility with the original features of the historical masonry structures (especially in stone and clay) aiming to pursue the effectiveness and durability of the intervention. The use of vegetal fibers (i.e., the Sisal one) is an exciting challenge for the construction industry considering that they require a lower level of industrialization for their processing, and therefore, their costs are considerably lower, as compared to the most common synthetic/metal fibers. Samples of Sisal-composite are tested in three-point bending, aiming to estimate both their bending stress and fracture energy. Tensile and compressive tests were also performed on the composite samples, while water retention and slump test were performed on the fresh mix. At last, the tensile tests on the Sisal strand were performed to evaluate the tensile stress of both strand and wire. An original mechanical interpretation is proposed to explain two interesting phenomena that arose from the analysis of experimental data. The comparison among the performances of unreinforced and reinforced mortar suggests that the use of short fibers is recommendable as coating in the retrofitting interventions alternatively to the long uni or bi-directional fiber strands adopted in the classic fibrous reinforcement (i.e., FRCM). The proposed composite also ensures mix-independent great workability, excellent ductility, and strength, and it can be considered a promising alternative to the classic fiber-reinforcing systems. As final remarks, the use of fiber F1 (length of 24 mm) with respect to fiber F2 (length of 13 mm) is more recommendable in the retrofitting interventions of historical buildings, ensuring higher strength and/or ductility for the composite. [ABSTRACT FROM AUTHOR]