The discharge of contaminated effluents containing organic dyes is a persistent environmental issue due to their toxicity, stability, and resistance to biodegradation. Among these dyes, malachite green (MG) is particularly concerning because of its widespread industrial use and severe ecological and health impacts. To address this problem, SnO2/Zn2-SnO4 heterostructures were synthesized via sol-gel and evaluated for MG degradation under ultraviolet irradiation. The SnO2/Zn2-SnO4 catalyst has been characterized by X-ray diffraction (XRD), photoluminescence (PL), field-emission scanning electron microscopy coupled with energy-dispersive spectroscopy (FE-SEM-EDS), ultraviolet-visible (UV-vis) spectroscopy, Brunauer-Emmett-Teller method, and electrochemical impedance spectroscopy (EIS). Structural properties revealed that the catalyst presents a polycrystalline structure and crystallite sizes in the range of 11-25 nm. The band gap energy of the Sn:Zn (1:2) catalyst was 2.88 eV, which was lower than that of pure SnO2 (3.33 eV), indicating enhanced light absorption. MG photocatalysis degradation tests were conducted under ultraviolet irradiation. The ZnSn 1:2 sample achieved a degradation efficiency of approximately 96% after 100 min, while the pure SnO2, ZnSn 1:4, and ZnSn 1:6 samples reached only 81%, 88%, and 92%, respectively. This could be due to the presence of h+ and •OH species, which were identified as the most active radicals during the photocatalytic process. Furthermore, the 1:2 ZnSn photocatalyst demonstrated good stability and maintained its photocatalytic performance after five successive degradation cycles. These results indicate that the Zn/Sn 1:2 ratio results in the highest photocatalytic efficiency, confirming the superior effect of Zn2-SnO4 structure in enhancing charge separation and accelerating the degradation of malachite green compared with the other compositions.

This study evaluates the influence of three chemical accelerators-potassium sulfate (K2SO4), calcium chloride (CaCl2) and sodium hydroxide (NaOH)-at two dosage levels (1.5% and 3.0% by binder mass) on the performance of limestone calcined clay cement (LC3) mortars for 3D printing applications. CaCl2 and NaOH significantly accelerated setting times, with reductions of up to 66% and 57% in initial setting time, respectively, enhancing early-age workability and buildability. CaCl2 notably improved early mechanical properties, increasing tensile strength from 0 to similar to 1.8 MPa and compressive strength by over 3000% after 6 h, while NaOH primarily enhanced fresh-state stiffness and load-bearing capacity with moderate strength gains at later ages. In contrast, K2SO4 functioned mainly as a hardening accelerator, increasing 1-day tensile and compressive strengths by 82% and 144%, respectively, without substantially affecting setting times or fresh-state properties. Microstructural characterization revealed that CaCl2 and NaOH accelerate hydration kinetics but may compromise long-term durability due to incomplete phase development and heterogeneous pore structures, whereas K2SO4 promotes stable ettringite formation and matrix integrity. These findings provide critical insights for selecting accelerator types and dosages to optimize the rheology, buildability, and mechanical performance of 3D-printed LC3 mortars in sustainable construction.

Silica microspheres doped with epoxy resin and methyl-ethyl-ketone (MEK) catalyst were synthesized using a modified Stöber method. The resulting material is a potential candidate as a self-healing additive for cementing slurries, especially in oilwell applications. Once dispersed in a cementitious matrix, the microspheres with encapsulated material ruptures under the stress caused by cracks or damage formed in the cement sheath, bringing the epoxy resin in contact with the catalyst. The resulting polymerization reaction slows down the growth of the crack. The encapsulation process was carried out using a variation of the Stöber method to obtain micro/nano silica spheres. The resulting material was characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis, energy dispersive spectroscopy (EDS), scanning electronic microscopy (MEV) and BET surface area analysis. The results of the FTIR and thermogravimetric analysis confirm the presence of silica and the full encapsulation of resin and catalyst. MEV - EDS showed that the average size of the synthesized spheres is the range from 50 to 250 μm. BET analysis showed a superficial area of 46.785 m²/g and a pore volume of 0.0983 cm³/g for the doped silica microcapsules with epoxy resin. For the doped microcapsules with MEK, the surface area was 397.349 m²/g and the pore volume was 0.0280 cm³/g. SEM images showed that once added to a cement slurry, the synthesized capsules ruptured in the presence of cracks, releasing the reagents. The results show that the synthesis process was successful for both encapsulated resin and encapsulated catalyst.

3D printing has been incorporated into civil construction as an innovative technology, which uses cementitious composites to produce objects in layered structures. However, studies still point to challenges regarding the complexity of the parameters involved, especially when the material exhibits partially developed strength and stiffness, that is, during printing. A critical issue lies in understanding and predicting the specific types of structural failures that can occur during the printing process. This study proposes an analytical model to verify the structural element failure type during printing: plastic collapse or elastic buckling. The model is based on material physical nonlinearity, since it considers its properties evolving over time, according to the printing speed, meeting the need for models that can simulate the structure’s behavior in their fresh state during printing. The results indicated that the analytical model correctly reveals the failure type, with a difference of 3.7

The interest in the development of 3D printing of concrete (3DCP) and its mixtures has significantly increased in recent years. In particular, lightweight mixtures, capable of optimizing the printing process and the thermal comfort of printed structures, still need to be studied. However, it is known that the addition of lightweight aggregates reduces density, providing better resistance to both buckling and plastic collapse during printing. In this sense, the present study aimed at evaluating the influence of the replacement of natural sand by lightweight expanded clay aggregate (LECA) on the fresh state properties of 3DCP mixtures. A 22 factorial design was used, with the replacement content of sand by LECA and the aggregate to binder ratio as independent factors. The squeeze-flow technique, together with the flow-table test, were used to evaluate the rheological behavior of the 3DCP mixtures containing aggregates up to 1.2 mm in maximum diameter. The results showed that replacing sand with LECA increased the flow tension and viscosity of the mix, which resulted in increased constructability preserving the extrudability of to the reference mix. In addition, the mixes with LECA showed up to a 13 % decrease in density in the fresh state, improving the resistance to both local buckling and preventing the plastic collapse during printing.

Nickel alloys and composites are interesting engineering materials as a result of a combination of mechanical, corrosion and wear resistance at service temperatures that exceed those of steels and steel-based materials. The present study aimed at sintering Ni-graphite composites from NiO-SiC mixtures and investigate the in-situ formation of graphite. NiO powders were mixed with SiC (0, 3, 5 and 10 wt.%) and attrition-milled during 1 h. The mixtures were then granulated using 1.5 wt.% paraffin in hexane solution and uniaxially pressed under 400 MPa. The cylindrical pellets were then sintered at 1200 ºC. The sintered materials were characterized by density measurements, dilatometric and microstructural analyses, as well as Vickers microhardness. The results showed that Ni-graphite composites were successfully produced from NiO-SiC mixtures with full reduction of NiO and dissociation of SiC to form a Ni-Si matrix and graphite nodules.

The application of insulating materials in the construction industry is an intelligent strategy that promotes energy efficiency by reducing energy consumption through enhanced thermal retention in indoor spaces, resulting in improved comfort and resource savings. The focus on enhancing thermal performance has led to the utilization of techniques involving cementitious materials and additives to impart insulation properties. In this study, we investigate the influence of Hydroxypropyl Methyl Cellulose (HPMC) on the thermal and mechanical properties of rendering mortars. Four different concentrations of HPMC (0.015%, 0.030%, 0.045%, and 0.060%) were analyzed and compared with a reference mixture. Various tests were conducted to determine the fresh and hardened state properties of the mortars, including consistency index, bulk density, water loss through evaporation, compressive strength, flexural tensile strength, adhesive flexural strength, water absorption by immersion, and modulus of elasticity. The thermal performance was evaluated using a prototype that simulated heat incidence on a cementitious panel. The results indicate that the incorporation of HPMC allows for the production of lighter materials with a weight reduction of 11.76% due to the high porosity induced by the additive. This high void content contributes to thermal insulation by reducing the material's conductivity by up to 30% while maintaining a fixed heat flux of approximately 49 W when subjected to the same heat flux. The resistance to heat transfer through the panel varies with the addition of HPMC, with the highest incorporation of the additive resulting in a 32.6% increase in thermal resistance compared to the reference mixture. These findings highlight the potential of HPMC as an effective additive for improving the thermal and mechanical performance of rendering mortars, thereby contributing to enhanced energy efficiency in building construction. The results have implications for the development of sustainable building materials that optimize thermal insulation and reduce energy consumption, thereby promoting environmentally friendly practices in the construction industry.

LC3 coating mortars have been developed by replacing 45 - 60 % of Portland cement with metakaolin and limestone (2:1) and using a 1:4.5 binder-to-sand ratio to create an energy-saving and environmentally friendly alternative. Their thermal conductivity was reduced by up to 51 %, and the thermal insulation was improved by up to 4 degrees C with just a 2 cm layer application compared to a mortar with 100 % cement. By increasing the water content by just 12 %, the consistency index of the mortar was maintained without using any additives. LC3 coating mortars with less cement and more sand still resemble traditional mortars, complying with all regulations.

The construction industry has incorporated 3D printing as an innovative technology. However, there are still challenges involving the complexity of the necessary parameters, such as the geometric characteristics, strength, and rigidity of the printed objects, depending on the studied material. Therefore, this study proposes a new tridimensional computational modeling for dimensioning 3D-printed structures. The model is based on the physical non-linearity of the material and the geometric non-linearity of the structure. It consists of a numerical reproduction of an experimental test using frame finite elements and considers the material properties’ evolution over time by construction phases. The printing speed used is 60 mm/s, and the time interval between layers is 11 s. The results obtained revealed good agreement with those from experimental tests and validated the theoretical formulation. The differences between computational and theoretical methods varied from 0.58 to 3.38% for different building rates. In terms of vertical normal stress at the base of the walls, the maximum percentage variation between the models is of 5.22% and less than 1 mm in absolute values for vertical displacements. The model successfully predicted the failure moment of the structure. The parametric analyses showed that the proposed model is an accessible, effective, and accurate tool to reveal the effects of printing speed on the construction process.

The continuous search for improved thermal confort and energy efficient buildings has driving forward the study of construction materials with low heat transfer. The present work evaluated the thermal characteristics of coating mortars containing partial replacements of sand by expanded vermiculite, as well as the understanding of the temperature flow through masonry samples constituted by ceramic bricks coated with alternative mortars 1:1:6 (cement: lime: sand). A lab apparatus was assembled to simulate the heat incidence and transfer through mansory samples by registering the temperature at different points of the mansory surfaces. In addition, the thermal performance of the mortars was characterized in the fresh and hardened states using the KD -2 Pro device. The results showed that replacing sand by expanded vermiculite increased the void index and reduced the thermal conductivity of the mortars. The temperature gradient between the opposite faces of the mansory increased from 25 C-degrees to 34 C-degrees after 3 hours of testing, by replacing 45% of sand by expanded vermiculite. No significantly effect on the mechanical properties of the materials was observed.

3D concrete printing (3DCP) is a construction technique based on the deposition of successive layers of a cementitious composite without the need for conventional formwork. For the technique to be applied it is necessary that the cementitious composite used allows the passage in continuous flow in a 3D printing nozzle (extrusion capacity) and presents low deformation of the printed layers (buildability). In this perspective, the aim of this study was to understand the influence of Metakaolin (MK), sand and water incorporation on the extrusion capabilities and buildability of cementitious composites for 3D printing. The analysis was designed in a simplex lattice mixture statistical experimental planning. Extrusion ability was evaluated using an experimental flow rate by extruder mill and slump flow. Buildability was analyzed by the maximum number of printed layers, shape retention index, layer thickness variation, and squareness deviation in printed blocks. The squeeze flow test was carried out as a parameter for both printing properties. The water/binder ratio was the most determinant variable in extrusion capacity for its responsibility to fluidize the mixture. Increasing the sand content improves buildability but reduces the application time. On the other hand, MK presented the advantage of controlling viscosity and maintaining good fluidity over time, due to a slower setting. There was a significant interaction between sand and MK in the packing of grains, increasing the properties related to extrusion. It was possible to print with a 30% MK content by adjusting the water. The yield stress was directly related to the flow rate, validating the experimental methodology created. Thus, it was possible to understand the effect of each component, as well as their interactions.

This work aimed to evaluate the influence conventional fine aggregate substitution by LECA (light expanded clay aggregate) evaluating the physical and mechanical properties of lightweight cement-based composites for 3D printing. The mixtures were formulated using a 22 central composite rotatable design (CCRD). The independent factors were the substitution content of sand and the aggregate-to-binder ratio. The results showed that the replacement of sand by LECA increased the thermal insulation without compromising important structural properties such as mechanical strength and porosity. The thermal behavior of the composites was modeled and an equation dependent only on the substitution content was found.

Resumo No cenário da Construção Civil, o desempenho dos elementos construtivos constitui uma temática pertinente para a pesquisa científica. Sob esse viés, o objetivo do trabalho consistiu em analisar o comportamento mecânico e térmico de argamassas de revestimento, utilizando diferentes teores - 10%, 20%, 30%, 40% e 50% - de uma fração fina de argila expandida como substituta parcial do agregado convencional, a fim de compará-las a uma argamassa de referência sem argila expandida. Para isso, foram determinadas importantes propriedades mecânicas das argamassas, tanto no estado fresco como no estado endurecido. Além disso, foi determinada a condutividade térmica das argamassas e realizados testes laboratoriais com o auxílio de simuladores de incidência e transferência de calor nas amostras. Os resultados apontam que as argamassas com incorporação de argila expandida não apresentaram impactos negativos nas suas propriedades mecânicas. Em contrapartida, observou-se que o aumento do teor de argila expandida na composição dos traços reduziu a condutividade térmica e aumentou o isolamento térmico das amostras. Desse modo, fica evidente a influência do agregado leve no comportamento térmico das argamassas em estudo, sem comprometer o seu comportamento mecânico.

Waste from mineral extraction and the manufacturing industry can be used to produce lightweight concrete. Moreover, fiber-reinforcing lightweight concrete is capable of reducing structural weight and piece sections, resulting in a variety of applications such as flooring, shotcrete and precast concrete. This work aimed at studying fiber-reinforced lightweight concrete mixtures prepared with the combined addition of multiple residues, i.e., rubber, limestone and porcelain dust residues along with expanded clay. 0.2% to 0.6 vol% steel, polypropylene, glass and carbon fibers, were studied. A reference fiber-free lightweight mixture with compressive strength of 32 MPa was also produced. The physical characteristics of the mixtures were evaluated by consistency tests, void indices, water absorption and density measurements. The mechanical characterization was carried out by compressive, flexural and fracture strength in addition to toughness tests. The results indicated that the addition of fibers decreased the workability of the concrete, but improved flexural and fracture strength along with toughness. The effects of fiber volume and properties, such as shape factor, tensile stress and elastic modulus on the properties of the resulting materials were evaluated. Steel and carbon fibers resulted in the best fracture strength properties, due to their high modulus of elasticity and tensile strength.

Self-leveling mortar (SLM) is a special mortar that can flow and fill under its own weight without the need for any compaction energy. To meet these characteristics and to ensure their stability (no segregation and exudation) these mortars require, in addition to proper mixing design and the use of water reducing assets, a large quantity of fines or viscosity modifying additives, which raises the cost for the production. The use of industrial by products such as sugar-cane bagasse ash (SCBA) is an interesting alternative because they are lower cost materials and act as viscosity modifying agent, providing improvements in the rheological, physical and mechanical properties for SLM. Thus, the influence of SCBA on the rheological, physical and mechanical properties of cement-based and limestone filler (LF) mortars will be investigate in this research. The mortars were produced with a water/binder (cement + LF + SCBA) volumetric ratio of 0.85 and 15%, 20%, 25% and 30% Portland cement (PC) replacement by SCBA. An experimental study was conducted to evaluate the effects of SCBA incorporation on the properties of fresh (viscosity, flowability and filling ability) and hardened mortars (flexural strength, compressive strength, dynamic modulus of elasticity, bond strength and water absorption by capillarity). The results show that the rheological, physical and mechanical behavior of mortars was improved, especially for contents of up to 25% replacement of PC by SCBA. For higher contents, the performance of SLM was reduced.