Membrane separation is an effective method for recovering biomass in biorefineries. Cellulose acetate (CA) membranes exhibit excellent separation capabilities and high selectivity. The use of lignocellulosic materials, such as sisal fiber, for the production of CA membranes represents a unique opportunity in this context. This study aimed to develop sisal fiber-derived CA membranes under optimized synthesis conditions for the efficient removal of furfural from lignocellulosic hydrolysates. The biomass was subjected to chemical treatments (organosolv and dilute acid) to isolate the cellulose. An experimental design approach was used to determine the optimal conditions for cellulose recovery, yielding a product containing 2.4% residual impurities. This cellulose was subsequently acetylated to produce CA, a conversion confirmed by spectroscopic analysis. CA and CA/PEG-400 membranes (incorporating poly-(ethylene glycol) 400 into their composition) were synthesized using the phase inversion method. All membranes exhibited a porous, asymmetric structure. Membranes containing PEG-400 within the polymer matrix displayed a higher porosity percentage, lower permeate flux, and higher furfural recovery. The inclusion of PEG-400 resulted in a membrane with a smoother surface and smaller poresfindings corroborated by scanning electron microscopy data. The experimental condition involving the lowest synthesis temperature (5 °C) and the presence of PEG-400 yielded the highest furfural retention, reaching 92%.

Coral reefs are very important ecosystems for the planet, offering ecological and socio-economic benefits. However, they are under threat due to anthropogenic factors and environmental changes. This study assesses the feasibility of weathered Portland cement concrete as a material for marine artificial reefs by comparing its physicochemical and mechanical properties with those of natural coral skeletons from the coast of Paraíba, Brazil. Analyses included microstructural and physical characterization, compressive strength and ultrasonic pulse velocity tests, as well as pH monitoring. The results indicated that weathered concrete exhibits mineralogical similarity to corals, with the presence of carbonate phases and portlandite absent due to advanced carbonation. The compressive strength of the concrete (27.6 MPa) was significantly higher than that of the coral samples (1–6 MPa), while the porosity of the corals (34–41%) exceeded that of the concrete (14%). The alkaline nature of the concrete (pH 9.7) remained stable. Although differences in physical and mechanical properties are evident, the values are within the ranges reported for cementitious materials in marine applications. Mineralogical similarities between coral skeletons and concrete support its potential as a functional analog in artificial reefs, while adjustments in geometry and porosity are suggested to enhance ecological compatibility.

This study aims to deepen the understanding of the formation of tricalcium silicate (alite) polymorphs in synthetic clinker, produced under controlled conditions that simulate industrial scenarios, with the goal of contributing to more sustainable practices in Portland cement production. The innovation of this research lies in the combined evaluation of the effects of crystallinity and particle size of silica—in the forms of crystalline quartz and amorphous silica gel, across different granulometric ranges—on the nucleation and stabilization of the M1 and M3 monoclinic polymorphs of alite. Using advanced characterization techniques such as laser granulometry, X-ray fluorescence, X-ray diffraction, and optical microscopy, it was demonstrated that increasing the silica particle size, regardless of crystallinity, reduces the alite content and promotes an increase in the content of free lime and belite. Furthermore, the silica particle size directly influences the size of alite crystals, while the interaction between crystallinity and particle size has a significant impact on the stabilization of alite polymorphs. These findings are essential for optimizing the clinker manufacturing process, potentially reducing energy consumption and promoting the production of more reactive forms of cement, thereby contributing to sustainability in the cement industry.

ABSTRACT The rational use of materials in construction, particularly cementitious materials, is crucial for environmental preservation. One way to optimize this consumption, especially in mortar production, is to study the packing of fine aggregates and their interactions with the cementitious phase. Several factors influence the rheology of such composites, including void ratio and packing density. This study investigates the role of particle size distribution in packing density by applying classical models and a modified approach. Twenty granular sets were analyzed using these theoretical models, considering different numbers of grain size distribution classes. In this work, packing densities were determined using the CPM (Compressible Packing Model) and a proposed alternative method, while natural sand was used to experimentally validate the theoretical results, reproducing nine of the twenty developed sets. From the analyzed grain size distributions, theoretical models were found to fit natural four-class sands, but their accuracy declined when the number of classes exceeded five classes. The results indicated that increasing the number of grain classes enhances packing density up to 7,5% in natural sands, with this effect being more pronounced in sets derived from theoretical models, ranging up to 13%. The correlation between packing density and the uniformity coefficient followed a sigmoidal fit, suggesting that less uniform sands have higher void ratios. Experimental validation of the theoretical results revealed that the packing density values obtained using the CPM model were 11% to 16% lower than the experimental values. The proposed modified model yielded better results, demonstrating less sensitivity to increases in the fineness modulus.

This paper describes the first ever reported case in Brazil where delayed ettringite formation (DEF) has been confirmed as the sole cause of deterioration in field concrete. Still under construction and less than 2 years old, numerous cracks were observed in the foundation structures of a building located in Recife, a city known for its history of alkali–aggregate reaction (AAR) cases. In addition to a field survey of cracks, microstructural analyses, tests for residual expansion and compressive strength, a review of the structural design, determination of sulfate content in the groundwater and simplified thermal analysis were carried out. The results confirmed that DEF was the sole cause of the damage present in cast-in-place concrete structures, with no evidence of AAR or any other deterioration process. This work corroborates previously published studies on the high risk of the occurrence of DEF in the region, demonstrating the urgent need for a preventive technical standard in the country, considering the chemical composition of cements and prior thermal analyses to adopt possible preventive measures to limit the maximum internal temperature of concrete.

Ceramic detachment is a serious problem that persists in modern building constructions despite technological advances and updated regulatory documents. Most of these detachments occur at the interface between the adhesive mortar and the ceramic tile, due to the action of simultaneous tensile and shearing efforts. However, despite this understanding, experimental studies that evaluate the integrity of the adhesion of façades covering materials subjected to simultaneous stress are scarce. In this sense, this study proposes to evaluate the integrity of adhesive mortar joints using the mixed-mode flexure (MMF) crack propagation test. Force and elastic and dissipated energy data were used in this analysis. Prismatic specimens, with a size of 160 × 40 mm2 and a thickness of 6 mm, were produced consisting of two ceramic plates joined by a layer of adhesive mortar at 5 ± 0.5 mm. An acetate film was inserted into one of the mortar–ceramic interfaces in order to simulate the presence of a previous crack, and different crack sizes were used. The results showed the high stress-concentrating effect that the existence of flaws in the interface region has on fracture resistance, as well as the importance of effective contact between the materials. The energy parameters confirmed the analyses carried out based on the load values. The elastic energy of the system fell in the cracked samples, showing that there is a close relationship between the interface energy and the adhesive strength of the material. An energy release of the order of 0.053 ± 0.031 J was required for a 15 mm crack to propagate, creating a fracture surface.

Abstract Energy storage is essential for advancing green energy solutions, with the lead-acid battery market expected to grow by 4.4 percent a year until 2029, reaching USD 58.65 billion. Lithium-ion batteries, although predominant, face challenges such as cost, stability, safety, and environmental impacts, including a lack of efficient recycling. On the other hand, lead-acid batteries, with a 99 percent recycling rate in the US, offer a more sustainable option. Hybrid Electric Vehicles (HEVs) play a crucial role in fuel economy and pollutant reduction, requiring batteries with good dynamic charge acceptance. Problems such as sulphation in lead batteries are mitigated with additives such as carbon and sodium lignosulphonate, which improve performance. This study focuses on optimizing the composition of battery pastes, maximizing charge acceptance by analyzing the interaction between carbon and sodium lignosulphonate, to improve the efficiency and competitiveness of lead-acid batteries by evaluating their electrochemical and electrical properties.

Abstract Alkali-silica reaction (ASR) is a deleterious expansion phenomenon affecting concrete structures worldwide. It occurs when a susceptible chemical composition of concrete components is present, and it is particularly rampant in inherently humid environments. This phenomenon is exacerbated when found in mass concrete structures such as dams and foundations. The amount of volumetric ASR strain used to be deemed as nearly constant, however, recent advances have shown that it is actually affected by the distribution of volumetric stresses. Therefore, this behavior demands an update in the numerical models that have been devised to simulate the anisotropic ASR-driven expansion. This paper deals with Saouma & Perotti’s thermo-chemo-mechanical coupled model, which has been applied in a solely mechanical manner, and updated to account for a varying volumetric strain. A simulation of the experiment that shed new light on the variation of ASR volumetric strain was then carried out with the finite element method package COMSOL. As a result, significantly smaller errors in predicted strains were attained by the updated model in comparison to the original one, and consequently, the new model poses a promising tool for a more accurate simulation of ASR expansion.

Polylactic acid/chitosan (PLA/CS) and poly(vinyl alcohol)/chitosan (PVA/CS) are considered potential blends for use in tissue engineering, since when obtained in the form of 3D fibers they can form structures with high porosity, biocompatibility, antimicrobial activity and morphology similar to tissues and organs. However, there is a scarce number of reports in the literature addressing the production of systems based on 3D fibrous mixtures of PVA or PLA with high chitosan amount because of the difficulty in spinning CS into stable structures using acidic solutions, and without further employment of cross-linking agents. Therefore, this work focused on a novel procedure to prepare 3D fibrous structures of PVA and PLA with high chitosan content, combining the solution blow spinning technique, a heated air environment and the use of eco-friendly solvents, without using crosslinking agents. The influence of CS incorporation on the as-prepared structures was assessed by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, contact angle measurement, porosity, swelling and degradation tests. Rheological tests evidenced that an increase in the CS content implies a greater viscosity of the spinning solutions, hindering the fibrillar structures formation. Fibers produced showed a randomly interconnected and highly porous fibrous cotton-wool-like structure, with fiber diameters ranging from 481 to 637 nm for PVA/CS systems, and from 1276 to 2050 nm for PLA/CS systems. A decrease in the thermal stability of the blend-based fibers and an increase in hydrophilicity, porosity, swelling and in vitro biodegradation were observed in the blend systems. Results indicate that the obtained fibrillar structures possess morphological and physical characteristics that may be interesting for application as 3D fibrous scaffolds in tissue engineering.

Solar energy presents the greatest potential by which to produce heat energy with reduced carbon emissions for power generation. To increase its harvesting and conversion, it is necessary to understand fundamental concepts and develop new materials. Although many processes can obtain selective absorbing surfaces (SAS) for application in solar energy exploitation, including electroplating methods, those processes have not sufficiently investigated the substrate’s treatment impact. The present work investigates 304 stainless steel (SS304) substrates treatment influence on the film’s (coatings) optical properties of SAS based on CrO3 electroplating. For this purpose, three main steps featured in the methodology: substrates treatment, coatings deposition, and physical-chemical characterization. The former was performed by detergent cleaning (DC), acid treatment (AT), and electropolishing (EP). Then, coatings were electroplated towards chromium deposition on the substrates with different deposition times. Finally, films were characterized by Profilometry, UV-Vis-NIR, and IR regions Spectroscopy and Scanning Electron Microscopy (SEM). The results indicated that, in terms of surface treatments on the substrate, the electropolished (EP) substrates presented average roughness values of 35 nm, reflectivity of 5.09%, and clear morphological difference (SEM) when compared to other treatments in this study (DC and AT). A SAS was successfully obtained, and the electropolished substrates (EP) presented coatings with better optical performance than other samples (DC and AT), with absorptivity values around 98% and emissivity of approximately 7%. A relationship between substrate treatment, its roughness, and the impacts on the optical selectivity of SASs was observed. Therefore, electropolishing is presented as a promising treatment for the SASs substrates.

This experimental study aims to present the behavior of cement composites containing rice husk ash over time previously undergone high thermal curing. A specific initial thermal curing up to 85 degrees C was designed to trigger delayed ettringite formation (DEF) as well as a specific exposure environment, by water immersion at 38 degrees C, over one year. Expansion measurements and microstructural analyses were performed to evaluate the level of attack and the integrity of mortars and concretes. To complement the study, mechanical properties of concretes were assessed to detect the level of damages by delayed ettringite formation expansion. Mortar performed differently from concrete, bringing risks of mistaken conclusions about admixture performance. Anyway, concrete tests have indicated that rice husk ash was able just to reduce the level of expansions, nonetheless, the contents were not enough to mitigate completely the generated expansions and avoid delayed ettringite formation and, consequently, damage.

The behaviour of concretes with and without rice husk ash was experimentally investigated with respect to the susceptibility to delayed ettringite formation. Concrete specimens have previously undergone a specific initial thermal curing up to 85°C, which was designed to trigger delayed ettringite formation. Specimens were subsequently exposed to a specific exposure environment by water immersion at 38°C, over 1 year. Expansion measurements and microstructural analyses were performed to evaluate the level of attack, as well as the integrity of concretes and chemical characteristics of compounds by means of SEM-EDS. Mechanical properties were also assessed over one year to detect the level of damage from delayed ettringite formation. The data has indicated that the incorporation of 8% of rice husk ash could partially reduce the level of DEF expansion and damage. The microstructure of cement matrices from both the reference and RHA concrete indicated different features, sulfate phase compositions and degradation stages. The reference concrete contained radial cracking from filled pores and nearby interfacial transition zone, whereas RHA concrete presented denser features, with microcracking scattered at random across cement matrix and minor neoformations.

Motivated by their low cost, lignosulfonate-based water reducers are the most used type of admixture in the concrete industry worldwide. Due to the plurality of types of lignosulfonates (LSs) and the recent update to the Brazilian standard for admixtures for concrete, the objective of this work was to investigate the impact of sodium (Na-LS) and magnesium (Mg-LS) lignosulfonates, raw materials present in the Brazilian market, in pastes and concretes produced with cement type CP II F 40 under different dosages (0.40% and 0.80%). For this, the following tests were performed: adsorption curves, isothermal calorimetry, microanalytical tests (TGA/DTG and DRX), and application in the concrete according to NBR 11768-1 standard. The results showed different hydration evolutions among the pastes produced with these lignosulfonates. As a consequence, despite the similarity in water reduction, it was verified that Mg-LS was more suitable for RA1-R (water reducer-retarder, setting time 120-360 min), while Na-LS was more suitable for RA1 (water reducer, setting time 30-160 min).

Despite technological advances in the production processes of the materials for ceramic façade coatings, the problems of detachments are still frequent. Therefore, this work aims to investigate, through a literature review, the existing gaps related to the adhesion ability of adhesive mortars, identifying new research needs that can better explain the behavior of the material. In addition, an experimental procedure was developed to evaluate the mechanical capacity of adhesive mortars when subjected to cyclic stresses. Dynamic stress measurements are presented for several blocks of mortar and on similar blocks but with a slot drilled prior to measurements (intended to represent failure). From these data we calculated values of stress energy, elastic energy, and dissipated energy. The experimental results showed that the energy involved in the test process accompanied the load values and current stress values. The mortar samples with the previous failure absorbed and dissipated less energy than mortars without failure, showing that materials that have less energy to dissipate, are materials that have developed less capacity to adhere, that is, to keep their parts together.

The kaolin mining waste (KW) is a residue generated during the purification process of extracting high purity kaolin used in different industries. KW is mainly constituted by kaolinite-rich clay and other secondary minerals such as anatase and quartz. With the appropriated and controlled process, calcined kaolin mining waste (CKW). It can be thermally activated by calcination to obtain a highly reactive metakaolinite rich material, which exhibits interesting pozzolanic properties. According to its chemical composition and high reactivity, this material is used as an aluminosilicate precursor in the production of geopolymers. One of the negative effects may be the formation of efflorescence. This paper evaluated geopolymer produced with CKW at different activation conditions (alkali concentration and sodium silicate content). The leaching of alkalis was studied through the development of efflorescence on the surface of hardened samples exposed to efflorescence formation conditions (contact with air and water). The results indicated that a larger activator provided a higher compressive strength and reduced the capillary absorption and the efflorescence formation. The data showed that the efflorescence formation can be appropriately controlled by adjusting the mix design parameters, especially the sodium silicate content.

This research studied the hydration of C3S-C3A-calcium sulfate systems made of combinations of two C3S (pure triclinic and Al-doped monoclinic), two C3A (pure cubic C3A and Na-doped orthorhombic), and two calcium sulfates (gypsum and hemihydrate). For each system, the hydration of four different SO3 contents (0.25-2.0 wt%) was assessed by calorimetry. The optimum SO3 content was fixed from calorimetry results, and the mixtures were evaluated by in-situ XRD and TGA. The type of C3S was the factor that most affected the sulfate balance of the systems. The mixes with Al-C3S produced a higher amount of ettringite in the first hours, resulting in much earlier sulfate depletions when compared to the mixes with pure C3S. The mixes with ort-C3A also showed faster sulfate depletion due to its higher reactivity compared with cb-C3A. Finally, the replacement of gypsum by hemihydrate resulted in faster sulfate depletion caused by the faster hemihydrate dissolution.

ZnO/bentonite hybrids were obtained by the microwave-assisted hydrothermal method, in order to change the bentonite surface and improve its activity for biodiesel production. No previous treatment of the clay was used and in situ crystallization of ZnO was done by a fast single step method. A factorial design was used to optimize synthesis conditions (e.g., reaction time, solution pH, and ZnO amount). The hybrids were fully characterized to determine its structural, chemical, and morphological properties. The results demonstrated the positive contribution of the microwave-assisted hydrothermal method to the formation of ZnO/bentonite hybrids, in addition to showing that the pH was the most important parameter influencing the formation of ZnO. A pH value of 8 favored the incorporation of approximately 19.6% of ZnO onto the smectite particles even after 5 min of microwave irradiation. The ZnO/bentonite hybrid with the biggest amount of ZnO was applied as a catalyst in the transesterification reaction of soybean oil. As such, our results demonstrated an ethyl ester conversion rate higher than 73% with better performance than that of natural bentonite (44%), which represents approximately 66% of the improvement of the catalytic activity.

Abstract The Alkali-Aggregate Reaction (AAR) phenomenon in concrete structures is perceived via expansion and cracking, swelling of gel like material, causing damage and disruption in structural elements. Despite extensive standardization, AAR cases are still persistently occurring worldwide. The literature on susceptibility of concrete to AAR reported examples of false negative and positive results. Hence, long-term prediction is a problem still posing great challenge to engineers. The severity of AAR on the structural integrity can be mostly elucidated by the assessment of the historic of elastic properties. There is consensus that AAR causes decrease in the load capacity concrete, reflected by reduction of elasticity modulus due damage progresses. Non-destructive techniques are often used as first approach, as they can provide relatively fast assessment in situ as well as in large structural elements. Its data interpretation carries certain degree of complexity due intrinsic characteristic of many of these methods. This is the case of Ultrasonic Pulse Velocity (UPV), which have been considered to present several limitations for such purpose. This paper deals the potential use of the Longitudinal Resonance Frequency (LRF) method as tool to evaluate the elastic historic of AAR prone elements. The LRF possesses higher energy than UPV. Also, using modulation of frequency in input signal combined the test geometry, the LRF allow application to larger samples as well as to extract complementary information alongside the dynamic elastic modulus. This way, the LRF was applied to study concrete beams tested under controlled conditions for about 1.5 year. The independent variables to the tests are: time, frequency, aggregate type, cement content, alkali content and water to cement ratio. The dependent variables are: damping, loss factor and elasticity modulus. The analysis associate damage with vibration damping, confirming reduction of elasticity through damage with experimental validation and prediction of AAR under rheological model.