Production Of Mortars Research Articles

Rheological behavior of nepheline syenite beneficiation waste-based mortars

The valorization of mining waste through its application as a fine aggregate in mortar production offers significant environmental advantages. However, the rheological properties of this composite system must be thoroughly investigated to evaluate the technical viability of such use. To date, no studies have been reported on the consistency and flowability of mortars incorporating nepheline syenite beneficiation waste (NSW) as a fine aggregate substitute. Therefore, the aim of this study was to examine the rheological behavior of mortars where natural fine aggregate (NFA) was partially or fully replaced by NSW. The results indicated that incorporating NSW leads to a marked increase in mortar viscosity. Notably, when substitution rates exceed 50 %, there is a substantial decline in workability, adversely affecting mortar handling. This trend was evidenced by the consistency index test, where the consistency of mortars D75 (225 mm) and D100 (219 mm) decreased significantly compared to the control mortar D0 (280 mm). Additionally, at the reference rotational speed (190.98 rpm), the measured viscosities were as follows: 4.99 Pa s (D0), 5.96 Pa s (D25), 6.96 Pa s (D50), 8.07 Pa s (D75), and 8.78 Pa s (D100), further confirming the reduction in fluidity as NSW content increased. The key properties of NSW believed to influence these results include particle size distribution, surface area, and the shape, geometry, and surface characteristics of the particles. Based on the findings, it can be concluded that NFA can be replaced by up to 50 % with NSW without significantly compromising the rheological properties of the mortar, thus promoting sustainable development through waste utilization.

Enhancing mortar performance: A comparative study on particle size of recycled concrete powder and metakaolin in binary and ternary blends

The construction industry generates substantial volumes of construction and demolition waste (CDW), including aggregates and fine particles classified as recycled concrete powder (RCP). This study investigates the sustainable reuse of RCP by evaluating its combined use with metakaolin (MK) as supplementary cementitious materials in both binary and ternary mixtures with Portland cement, aiming to reduce environmental impact without compromising mortar performance. The experimental program assessed two particle sizes of RCP, along with MK, and various replacement levels, which were pivotal parameters in the study. A series of binary and ternary mixtures were prepared with different proportions of RCP and MK, considering replacement levels ranging from 10 % to a maximum of 30 %, using RCP alone or in conjunction with MK. The mortars were analyzed in both fresh and hardened states, focusing on critical properties such as consistency index, compressive strength, splitting tensile strength, elastic modulus, water absorption, density, void index, and capillary water absorption. Furthermore, a microstructural analysis was conducted using scanning electron microscopy (SEM), and a cement consumption efficiency index, along with CO₂ emissions data, was calculated to provide a comprehensive evaluation of performance and sustainability. The findings demonstrate that RCP with a particle size comparable to that of cement (RCP1) significantly enhances both physical and mechanical performance, particularly in ternary mixtures with MK due to its pozzolanic activity, where the silica (SiO₂) and alumina (Al₂O₃) components react to form additional hydrated products, thereby improving the properties of mortars. For instance, the ternary mixture comprising 15 % RCP1 and 15 % MK attained compressive and splitting tensile strength of 29.26 MPa and 3.36 MPa at 28 days, respectively, compared to the reference mixture, which yielded 27.96 MPa and 3.33 MPa. Conversely, larger particle sizes (RCP2) and higher replacement levels led to a decline in performance across all evaluated parameters. Ternary mixtures containing RCP1 also exhibited a higher cement consumption efficiency index and lower CO₂ emissions per MPa. Notably, the mixture with 15 % RCP1 and 15 % MK showed the most favorable indicators overall, with cement consumption and CO₂ emissions measured at 12.08 kg/m³·MPa and 10.01 kgCO₂/m³·MPa, respectively. These results suggest that the synergy between RCP1 and MK enhances particle packing and matrix density, which in turn improves the structural properties of the mortar. The incorporation of MK compensates for the limited reactivity of RCP, especially at higher replacement levels, while the utilization of RCP1 offers significant sustainability benefits by reducing Portland cement consumption. This study demonstrates that the combination of RCP and MK in ternary mixtures presents a technically viable and sustainable alternative for mortar production, optimizing cement use and reducing CO₂ emissions. The innovative application of CDW-derived RCP in construction materials represents a practical approach to promoting more sustainable practices within the industry.

Study of Mechanical Properties Using Carbonized Rice Husk and Eggshell to Prepare Sustainable Concrete and its Viability in Civil Construction

Sustainability has become an increasingly present concern in the construction industry, which has led to a search for more ecological and sustainable alternatives in the production of construction materials. In this context, research references have shown promising results in the use of carbonized rice husk and eggshell. The use of rice husk as a partial substitute for cement in concrete has proven to be effective in reducing environmental impact, since this residue has pozzolanic characteristics, providing greater resistance to the concrete. Eggshell, in turn, has been used as an additive in the production of mortars, providing improvements in the mechanical and thermal properties of these materials. These sustainable solutions in civil construction are aligned with the ESG agenda of companies, which are increasingly seeking minimize the environmental impact of its activities. The study verified through axial compression resistance tests that the composites prepared with 1.5 % (w/w) had superior compressive strength by around 20% compared to the composites prepared with 2 % (w/w). In other words, with a lower concentration it achieved a satisfactory reinforcement effect, better preserving the structure. From the analysis of the diametral compression resistance results, the concentration of 1.5% (w/w) showed a specific reinforcing effect, both with the use of crushed eggshells and with the use of carbonized rice husks dispersed in concrete. The concentration of 1.5% (w/w) showed a specific reinforcing effect, both with the use of crushed eggshells and with the use of carbonized rice husks dispersed in concrete. The lowest content of 1% (w/w) was not enough to reinforce the material, presenting the lowest yield strength values of 2.98 and 3.54 MPa for egg and rice, respectively. The values for 1.5% (w/w) reached values of 4.22 and 4.68 MPa, for egg and rice. Around 20% of the compounds prepared with the highest filler levels, both with crushed eggshell and carbonized rice husk.

Recycling and optimum utilization of CRT glass as building materials: An application of low CO2 based circular economy for sustainable construction

The construction industry is the major contributor of CO2 emission around the globe. The rapid advances in the electronics industry have transformed the disposal of cathode ray tube glass waste (CRT-WG) into a prominent environmental concern. Recycling of CRT glasses as building materials can help in the production of sustainable construction. Numerous previous studies have documented that CRT-WG can be utilized either as a component of fine aggregate or binder material as it provides a cleaner solution and reduce carbon emission. Under this cleaner production and low CO2 emission perspective, this paper provides a thorough review of the previous studies on the utilization of CRT glass as a partially and fully substitute of sand and cementitious material in mortar production and propose an application of CO2 based circular economy model for reduce carbon emissions. This paper summarized the fresh, mechanical and durability properties of mortar incorporating treated and un-treated CRT-WG with different mineral additives and w/b ratios. Furthermore, this research explores the optimal proportions of CRT glass that can be use as replacements for sand and cement powder to make eco-friendly and sustainable low carbon mortar suitable for both structural and non-structural applications. More particularly, this review emphasizes the benefits, the need for additional research, and the drawbacks of CRT-WG use in construction building. Overall, this study proposes that incorporating CRT glass into building materials through a low CO2 based circular economy offers significant potential advantages. This study will help in optimization of CRT glass in concrete mix design in combination with waste materials for sustainable construction.

Exploring effects of supplementary cementitious materials on setting time, strength, and microscale properties of mortar

The concept of sustainability has become a crucial concern for safeguarding the planet. The current research has focused on developing affordable and eco-friendly mortar by using industrial wastes. This study explores the use of fly ash (FA) and ground granulated blast furnace slag (GGBFS), byproducts of steelmaking and coal burning, in mortar production. It examines their impacts on the compressive strength and setting times, when utilizing varying proportions of the materials. The study also evaluates water requirements for the workability, thus demonstrating the sustainability of these waste products in construction. The cementitious materials were employed in finely ground form and were replaced with further tertiary mixes including both supplements at 10%, 30%, and 50% of each. The mixtures were allowed to cure for 7, 14, and 28 days by immersion in water. The results showed improvements in the compressive strength of mortar samples incorporating FA and GGBFS at various curing ages. However, the water requirement and workability of mortar samples were altered as a result of utilizing these supplementary cementitious materials (SCMs). These findings will serve as a standard for environmentally responsible mortar using GGBFS and/or FA as SCMs.

Integrated Techno-Environmental Analysis of Finely Ground Silica Sand in Sustainable Mortar Production

The environmental impacts of cement production are becoming more urgent concerns. This study examined the mechanical characteristics of cement when it is partially replaced with finely crushed sand. The experimental program consisted of three different levels of sand fineness of 459 m2/kg, 497 m2/kg, and 543 m2/kg, as well as four substitution ratios of 10%, 20%, 30%, and 40%. A total of thirteen combinations were formulated and then evaluated. The results demonstrated that increasing sand fineness from 459 m2/kg to 543 m2/kg substantially impacted the compressive strength (CS), increasing it by up to 30%, and increasing the substitution ratio from 10% to 40% reduced the mechanical strength by roughly 40%. An extensive techno-environmental evaluation showed that replacing cement with finely crushed sand is technically feasible and environmentally advantageous. This technique can decrease carbon dioxide (CO2) emissions by around 40%, emphasizing its ecological benefits and coinciding with worldwide initiatives to decrease the environmental impact of construction materials. In summary, this study demonstrates the advantages of improving the mechanical characteristics of cement while minimizing its ecological footprint. It suggests that finely crushed sand can be used as a sustainable alternative in cement manufacturing, promoting the use of more environmentally friendly construction methods.

Mechanical properties of a mortar with aluminum fibers waste of drink cans

The aim of this study is to utilize drink cans as fibers to reinforce mortars production. for this purpose, we cut the cans into various sizes to investigate how the width and length of the fibers affect the mechanical properties of the mortar (2x10, 4x10 and 2x20)mm, as well as using different percentages 0,5%,1%, 1,5%, 2%, and 2,5% by the weight of the cement. The results of this study showed improvement of mechanical strength of the mortar especially the flexural strength. The comperessive strength increased by 14% compared to the control mortar, whereas the flexural strength increased by 14% and 20% compared to the control mortar of the fiber MF1 and MF2, while the addition of 2% of aluminium in fiber MF3 incresed the flexural strength by more than 39% compered to mortar not reinforced. The addition of alimunium fiber have helped in reducing the cracking of the mortar . Consequently, incorporating aluminum fibers from drink cans into the mortar mix will significantly impact the indirect tensile strength, flexural strength, ductility, and post-cracking behavior.

The Use of Waste Synthetic Hair Fibre in Cement Mortar

Cement mortar has low tensile strength and fracture strain; therefore, fibres are used to reinforce cement mortar. Synthetic hair is one of the most neglected of all the residual wastes that cause environmental problems in many developing countries. Therefore, this study used waste synthetic hair fibre in cement mortar production as a way to reduce the environmental effect generated by waste, and also to enhance the strength of the mortar for construction application. The study aimed to investigate the properties of cement mortar reinforced with waste synthetic hair fibres. 0, 2.5, 5, and 7.5% of synthetic hair fibre were used as a replacement for cement by weight in mortar. 100 × 100 × 100 mm cube, and 100mm diameter and 200mm length cylinder specimens were prepared, cured, and tested at ages 7, 14, and 28 days for tensile and compressive strengths, density, and water absorption. The highest compressive strength for the synthetic waste hair fibre reinforced mortar was 8.57N/mm2 as compared to 10.84N/mm2 achieved for the control at 28 days of curing. The synthetic waste hair fibre reinforced mortar achieved the highest tensile strength of 1.80N/mm2 as compared to 1.67N/mm2 achieved by the control at 28 days of curing, representing an increase of about 11% in tensile strength of the synthetic hair fibre reinforced mortar over the control. The highest density for the synthetic hair fibre reinforced mortar was 2114 kg/m3 as compared to the control of 2144 kg/m3. The lowest water absorption for the synthetic hair fibre reinforced mortar was 2.48% as compared to the control of 2.04%, respectively. It is concluded that the properties of cement mortar reinforced with waste synthetic hair fibres are acceptable for construction application and recommended that practitioners use 2.5% waste synthetic hair as a partial replacement for cement in producing mortar.

Feasebility of using waste hydrated cement paste and luminescent glass as aggregates for the production of mortar

This study examines feasibility of incorporating waste hydrated cement paste (WHCP) and luminescent glass (LG) as sand replacements in conventional mortars. Luminescent glass aggregates (LG) were produced by initially mixing luminescent powder with adhesive resin and subsequently adding glass pellets with size smaller than 2 cm. WHCP was produced by mixing cement and water and then cured at room temperature prior to be ground into aggregate with size smaller than 2 mm. Luminescent composite mortars (WLM) were produced by replacing 50–70% of sand by WHCP and LG in which LG replaced 40% of the sand content while WHCP replaced the remaining 10–30%. The feasibility of WLM samples were assessed by their physical and luminescent properties. As results, WLM samples met requirements for constructive mortar such as flowability, drying skrinkage and porosity. At 28d, all WLM samples achieved a strength of around 45 MPa at 28 days, satisfying the strength requirements for constructive mortar. Regarding luminescence properties, all WLM samples exhibited luminescent intensity higher than the threshold of human eyes up to 8h. Luminescent decay curves followed the trend observed in luminescent powders. As such, WLM can be utilized in building projects, particularly for the auxiliary tasks related to road and bridge structures.

Use of Milled Acanthocardia tuberculate Seashell as Fine Aggregate in Self-Compacting Mortars.

This study focuses on the feasibility of using ground Acanthocardia tuberculate seashells as fine aggregates for self-compacting mortar production. The obtained results show a promising future for coastal industries as their use eliminates waste products and improves the durability of these materials. The use of Acanthocardia tuberculate recycled aggregate, in terms of durability, improves the performance of all mixes made with seashells compared to those made with natural sand, although it decreases workability and slightly reduces mechanical strength. Proper mix design has beneficial effects, as it improves compressive strength, especially when the powder/sand ratio is 0.7. Three replacement ratios based on the volume (0%, 50%, and 100%) of natural limestone sand with recycled fine aggregate from Acanthocardia tuberculate seashells, and three different dosages modifying the powder/sand ratio (0.6, 0.7, and 0.8), were tested. The fresh-state properties of each self-compacting mixture were evaluated based on workability. The mineralogical phases of the hardened mixtures were characterised using X-ray diffraction, thermogravimetry, and differential analyses. Subsequently, the mechanical and durability properties were evaluated based on the compressive and flexural strengths, dry bulk density, accessible porosity for water and water absorption, drying shrinkage, mercury intrusion porosimetry, and water absorption by capillarity. Therefore, the use of Acanthocardia tuberculate seashells in cement-based systems contributes to circular economy.

Radiation and mechanical performance of cementitious materials containing ecofriendly nano laboratory waste glass

This study helps in managing waste glass and greening the environment by incorporating laboratory waste glass into mortar production to make an eco-friendly shielding material against gamma rays. The efficiency of using waste glass powder as a cement replacement or addition in mortar production was studied by using two waste glass sizes: micro glass (particle size range from 10.09 to 24.73 μm) and nano glass (particle size range from 10.57 to 26.42 nm) to design different mortar specimens with varying percentages of fine glass powder from 0 to 30%. Compressive strength and flexure strength were evaluated to determine mechanical properties. The results indicated that adding WGP to mortar positively affects the characteristics of cementitious composites. The linear and mass attenuation coefficients of the samples were experimentally determined using a NaI detector and various radioactive sources (Am-241, Ba-133, Eu-152, Cs-137, and Co-60) with gamma energies ranging from 59.53 to 1332 keV. The obtained coefficients were then compared to the theoretical values of the composites using XCOM software to verify their accuracy. Additionally, the half-value layer, tenth-value layer, mean free path, and effective atomic number were computed. Furthermore, the results revealed that the mortar sample with 30% nano additive glass was the most effective in reducing gamma radiation.

Fly ash admixture originating from lignite combustion in construction mortars – Time evolution of technical parameters and heavy metals leachability

The production of cement, the predominant construction binder, is associated with high energy consumption, enormous raw material depletion, and a large volume of CO2 emissions, making cement one of the most polluting materials. This study aims to contribute to the sustainability of the construction industry by significantly reducing the proportion of Portland cement (PC) in the composition of mortars. The binder content reduction was achieved by the addition of large amounts of fly ash admixture (FA) from lignite combustion while studying the effectiveness of the immobilization of heavy metals (HMs), which are present in FA, in the PC/FA matrix. Along with the analysis of the FA admixture amount on the properties of the prepared mortars, emphasis was put on the study of the influence of prolonged curing on the development of the physical parameters of the mortars and the immobilization efficiency of the HMs. It was revealed that FA can be added to PC by up to 20 wt%, enabling the production of construction mortars with high strength and low porosity, while confining hazardous substances such as HMs in the matrix. Prolonged curing at elevated relative humidity led to the continuous evolution and solidification of the mortar structure, improving its engineering properties and HMs immobilization efficiency.

Evaluation of the effect of curing conditions on compressive strength and microstructure of alkali-activated binders

Alkali-activated binders (AABs) are increasingly researched as sustainable alternatives to ordinary Portland cement (OPC), providing comparable strength. In recent years there has been a growing interest in studies focusing on the development of suitable composites and their fabrication methods. Composites' properties are significantly affected by temperature, humidity, formulations, and constituent types. Therefore, it is essential to understand these factors comprehensively to obtain the desired adequacy to use. This article aims to assess the impact of (i) temperature through ambient curing (25°C) and thermal curing (50°C for 24 hours), (ii) exposure to air (isolated or exposed to the air atmosphere), and (iii) susceptible to external humidity (air contacted or submerged) as curing conditions. The evaluation encompassed compressive strength tests at 1, 28, 63, and 91 days, along with microstructural evaluation through morphology analysis and incidence of voids. Digital image processing (DIP) through ImageJ software was employed. The AAB proposed consisted of fly ash (FA) and steel slag from the Basic Oxygen Furnace (BOF) process as precursors, with sodium hydroxide (NaOH) and sodium silicate (NaSi2O3) as alkali activators, applied in mortar production. Compressive strength results revealed that mortar subjected to thermal curing, isolated from air contact and external humidity, exhibited the highest strength outcome, with 46.05 MPa. Microstructural analysis indicated the formation of hydrated aluminosilicate gels and the presence of voids, including partially reacted particles and microcracks. The DIP analysis of the sectional area demonstrated that void incidence under 50 µm2 predominantly did not affect compressive strength.

Boosting mortar performance: use of recycled brick sand for enhanced mechanical properties

The construction industry is constantly seeking ways to become more sustainable. One area of exploration is mortar technology, where researchers are looking at replacing traditional components with alternative materials and adding a superplasticizer to improve mechanical strength and reduce the use of natural resources. The present study focuses on substituting brick waste sand in mortar at different replacement ratios of 0%, 10%, 30%, and 50%. The main objective is to investigate the effect of this substitution material on the properties of the mortar. The researchers have conducted compression and flexural tensile tests on prismatic specimens (4 x 4 x 16 cm³) at various curing periods (2, 7, and 28 days). The results showed that replacing 50% of sand with brick wastes significantly improved mortar properties. However, replacing more than 50% of the sand hurt the workability of the mortar. This study highlights the potential of using brick waste sand as an alternative to sand in mortar production, promoting resource conservation and sustainable construction. The findings suggest that while a 50% replacement ratio is beneficial, it is essential to carefully consider the mix design to maintain workability and overall performance.

Effect of accelerated carbonation on fine cement paste aggregates

Accelerated carbonation is suggested as a potential alternative for carbon dioxide sequestration, which also improves the microstructure of recycled concrete aggregates. In this study, the carbonation parameters of model aggregates derived from cement pastes with two different water/cement ratios (i.e., 0.5 and 0.7) were evaluated in order to maximize the benefits of the carbonation process on their density and absorption. For this purpose, in a first phase, the initial moisture content of the model aggregates and the reaction time were evaluated. Furthermore, in a second phase of mortar production, the fraction of fine natural aggregates was replaced, considering each type of unprocessed and carbonated model aggregate at volumetric replacement percentages of 50% and 100%, varying the amount of water in the mortar mix to maintain a similar workability in all the series. In this way, the properties of the eight series of mortars are evaluated in comparison with the control series made only with natural aggregates. The results indicate that the accelerated carbonation process positively influences density and absorption in the model aggregate. Regarding the parameters of the accelerated carbonation environment analyzed, for a higher w/c ratio in the original model aggregate, higher initial water content was necessary for the carbonation process to be efficient. As for the mechanical performance of the mortars with model aggregate, the series that incorporated model aggregate aggregates with a w/c ratio of 0.5 achieved better mechanical behavior compared to the series replacing model aggregate with a w/c ratio of 0.7; this was related to the formation of a more compact matrix in the mortar with model aggregate of cementitious pastes.

Towards sustainable construction: Strength and microstructural assessment of Dillenia suffruticosa and Acacia auriculiformis leaf ash as novel supplementary cementitious materials

Researchers are exploring local, recycled, and waste materials for construction to address environmental concerns. Concrete heavily depends on cement, contributing to energy consumption and greenhouse gas emissions. Substituting cement with alternatives like recycled materials can cut energy use and minimize the environmental impact on concrete production. This research represents the first investigation into using Dillenia Suffruticosa (DS) and Acacia Auriculiformis (AA) leaf ash as sustainable alternatives to cement in producing eco-friendly mortar, an area that other researchers have not previously explored. The study aims to investigate using DS and AA leaf ash as sustainable alternatives to cement in mortar production. In this study, the incorporation of DS and AA leaf ash as a partial replacement for cement was systematically varied in increments of 5 %, ranging from 5 % to 40 % of the total mortar volume. The ash was systematically incorporated into the mortar in increments of 5 %, ranging from 5 % to 40 % of the total mortar volume. The study further conducted a comprehensive investigation into the physical properties of the mortar, including consistency, bulk density, dry density, water absorption, and flow characteristics, alongside an analysis of its compressive strength. Microstructural behaviour was assessed using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis to provide a comprehensive analysis. Results indicate that the enhancement in compressive strength of DS ash specimens, relative to AA ash, ranged from 1.32 % to 24.49 % at 7 days, 5.81 %–16.86 % at 14 days, and 1.87 %–11.91 % at 28 days. Furthermore, the highest enhancement in compressive strength is observed with a composition containing 10 % DS ash and 5 % AA ash content, underscoring the superior performance of DS ash compared to AA ash. The mineralogical characteristics of DS and AA leaf ashes illustrate their effectiveness as supplementary cementitious materials in sustainable construction. The significant advantages of using DS and AA leaf ash as a cement substitute are environmental sustainability, innovative materials use, and contribution to sustainable construction.

Life-Cycle Assessment and Environmental Costs of Cement-Based Materials Manufactured with Mixed Recycled Aggregate and Biomass Ash.

The development of new building elements, such as concrete and mortar with sustainable materials, which produce a lower carbon footprint, is an achievable milestone in the short term. The need to reduce the environmental impact of the production of cement-based materials is of vital importance. This work focuses on the evaluation of the life-cycle assessment, production costs, mechanical performance, and durability of three mortars and three concrete mixtures in which mixed recycled aggregates (MRAs) and biomass bottom ash from olive waste (oBBA) were included to replace cement and aggregates. Powdered MRA and oBBA were also applied as complementary cementitious materials with a reduced environmental footprint. Chemical and physical tests were performed on the materials, and mechanical performance properties, life-cycle assessment, and life-cycle cost analysis were applied to demonstrate the technical and environmental benefits of using these materials in mortar and concrete mixtures. This research showed that the application of MRA and oBBA produced a small reduction in mechanical strength but a significant benefit in terms of life-cycle population and environmental costs. The results demonstrated that finding long-term mechanical strength decreases between 2.7% and 14% for mortar mixes and between 1.7% and 10.4% for concrete mixes. Although there were small reductions in mechanical performance, the savings in environmental and monetary terms make the feasibility of manufacturing these cement-based materials feasible and interesting for both society and the business world. CO2 emissions are reduced by 25% for mortar mixes and 12% for concrete mixes with recycled materials, and it is possible to reduce the cost per cubic meter of mortar production by 20%, and the savings in the cost of production of a cubic meter of concrete is 13.8%.

Bound by Binders: Multicraft Organisation and Industrial Interdependence of Lime Production for Mortar in the Eastern Mediterranean during Late Antiquity

In the late antique period (fourth-seventh centuries AD), lime was produced and consumed in great quantities for use in building, medicine, tanning, fulling, mortuary practices, and as an agricultural fertiliser. As a result, lime kilns (and associated slaking pits) are common features of late antique contexts – both in urban and rural environments and involving public institutions and private enterprise. In this paper we consider the archaeological remains of lime production and use in the eastern Mediterranean, a region in which dozens of lime production sites have been recorded. Focusing on the example of lime mortar production specifically, and following evidence for the associated chaîne opératoire, we demonstrate the versatility of the lime production process and how it frequently involved and even relied upon multiple industries.

The Application of Converter Sludge and Slag to Produce Ecological Cement Mortars.

The paper presents an analysis of the effective use of a mixture of steel sludge (S1) and slag (S2) from the converter process of steel production for the production of cement mortars. Metallurgical waste used in the research, which is currently deposited in waste landfills and heaps near plants, posing a threat to groundwater (possibility of leaching metal ions present in the waste), was used as a substitute for natural sand in the range of 0-20% by weight of cement (each). The obtained test results and their numerical analysis made it possible to determine the conditions for replacing part of the sand in cement mortars with a mixture of sludge and slag from a basic oxygen furnace (BOF) and to determine the effects of such modification. For the numerical analysis, a full quadratic Response Surface Model (RSM) was utilized for two controlled factors. This model was subsequently optimized through backward stepwise regression, ensuring the inclusion of only statistically significant components and verifying the consistency of residual distribution with the normal distribution (tested via Ryan-Joiner's test, p > 0.1). The designated material models are helpful in designing ecological cement mortars using difficult-to-recycle waste (i.e., sludge and converter slag), which is important for a circular economy. Mortars modified with a mixture of metallurgical waste (up to 20% each) are characterized by a slightly lower consistency, compressive and flexural strength, and water absorption. However, they show a lower decrease in mechanical strength after the freezing-thawing process (frost resistance) compared to control mortars. Mortars modified with metallurgical waste do not have a negative impact on the environment in terms of leaching heavy metal ions. The use of a mixture of sludge and steel slag in the amount of 40% (slag/sludge in a 20/20 ratio) allows you to save 200 kg of sand when producing 1 m3 of cement mortar (cost reduction by approx. EUR 5.1/Mg) and will also reduce the costs of the environmental fee for depositing waste.

Carbon nanofibers encapsulated by polyethylene glycol increase the mechanical properties and durability of OPC mortars

Carbon nanofibers (CNF) are promising additives for the reinforcement of cementitious materials. However, due to their high specific surface and hydrophobic nature, CNF are difficult to disperse in ordinary Portland cement (OPC) mortars when using conventional plasticizers. In this work, we evaluate the production of mortars with CNF encapsulated by a thin layer of polyethylene glycol (PEG) covalently grafted at their surface (CNF@PEG). CNF@PEGs were chemically prepared using two methods with PEG of various molecular weights. In all cases, the dispersion of the CNF@PEG in water as well as in a simulated cement pore solution was improved. Remarkably, mortars fabricated with CNF@PEG4k (PEG of molecular weight 4000 g/mol) exhibited a 20 % increase in compressive strength, 10 % increase in flexural strength and 25 % increase of the Young's modulus measured after 7 days, in comparison to a reference mortar. Finally, electrochemical impedance spectroscopy (EIS) was used to assess the ionic resistivity of the mortar. Mortars containing CNF@PEG4K had an ionic resistivity 43 % higher than the reference sample at 28 days leading to better durability. These results demonstrate that encapsulation of CNF by PEG is a successful strategy to improve the mechanical performance and durability of CNF-containing OPC mortars.