Extensive research on fiber-reinforced concrete (FRC) has led to a solid understanding of its structural behavior, enabling the development of design codes. Initially dominated by steel fibers, FRC has progressively incorporated macro synthetic fibers, particularly in Latin America, where it is widely used in tunnel linings. More recently, hybrid FRC, combining different fiber types, has attracted increasing attention due to its improved performance throughout the different stages of crack development. Although its short-term behavior is well established, its response under sustained loading (creep) and its influence on post-creep behavior remain insufficiently understood. This paper presents an experimental evaluation of the post-creep behavior of hybrid FRC, conducted in accordance with RILEM recommendations. The results are compared with those obtained for concrete reinforced with steel fibers and macro synthetic fibers.
The aim of this study is to evaluate the mechanical properties of self-compacting concrete (SCC) containing two types of brick aggregate (discarded and demolition brick aggregate) with a 100% replacement of both fine and coarse natural aggregates, besides incorporation of 10% tire crumb rubber as a replacement by volume of fine aggregate. Slump flow was evaluated for fresh state. Density, ultrasonic velocity (UPV), compressive strength, and dynamic modulus of elasticity were measured at 28, 56 and 90 days. The results showed significantly reductions in densities and UPV depending on the aggregate type and presence of rubber. Likewise, the dynamic modulus of elasticity decreased up to 63.2% at 90 days by inclusion of brick aggregate and by 22% with the rubber incorporation. A proposed equation to estimate dynamic modulus of elasticity at late ages was introduced with reasonable error and comparable values with experimental data obtained in this study.
Ultra-high-performance fiber-reinforced concrete (UHPFRC) exhibits outstanding mechanical and durability performance, strongly influenced by fiber orientation. This study evaluates the fiber orientation coefficient considering casting methods, element geometry, and thickness effects. Beams (100×100×500 mm3 and 150×150×600 mm3) and slabs (1000×50×1000 mm3) were analyzed. Beams were cast horizontally (with fixed and moving pouring points) and vertically (at different casting speeds). Slabs were cast using fixed and moving pouring points and later cut into longitudinal and transverse specimens. A total of 84 prisms were tested in flexure to determine tensile properties. Results show that casting procedures, structural typology, and thickness significantly affect fiber distribution and tensile behavior. Horizontal beams displayed lower variability, whereas slabs showed marked differences associated with their bidirectional configuration. Fiber orientation was found to influence constitutive law parameters. A good correlation was found between UNE 83519 results and UHPFRCMat app simulations. Reference orientation coefficients are proposed to support structural design.
This research explores the usability of reactive MgO (RM)-based materials as sustainable, low-carbon alternative binders for 3D concrete printing. Specifically, RM was substituted with 25 wt% of diverse silica sources to assess their potential: micro-silica (MS), metakaolin (MK), fly ash (FA), and basalt powder (Bst). By evaluating rheology, buildability, and 28-day compressive strength under a constant initial consistency, results reveal that the MK blend exhibited optimal rheological behavior. It combined low initial dynamic yield stress for smooth extrusion with substantial time-dependent viscosity build-up, completely preventing filament deformation. All mixtures demonstrated excellent buildability, successfully sustaining 20-layer structures without collapse. Furthermore, XRD analysis confirmed that highly amorphous silica in MS and MK facilitated extensive precipitation of magnesium silicate hydrate (M-S-H) gels. This microstructural improvement yielded the highest compressive strengths of 16.5 MPa and 13.9 MPa, respectively. Ultimately, RM-SiO₂ systems emerge as highly promising, low-carbon materials for digital construction.
The fresh and hardened state performance of conventional and self-compacting concrete (SCC) is affected by multiple factors. Supplementary cementitious materials (SCMs), chemical admixtures, the maximum aggregate size or the grading of aggregates influence how the mix is designed to specified performance requirements. Cohesiveness and workability can influence the hardened state properties of any mix, self-compacting or not. A large dataset compiled from routine industrial testing has been analysed to develop a tool that predicts the workability from the mix design. The dataset includes SCC and conventional mixes, incorporating SCMs and water reducers or superplasticisers at different dosages. Machine learning techniques have been employed to develop a classifier which estimates the slump class of mix designs. This paper describes how the challenges posed by analysing such a broad range of mix designs has been overcome and in what ways the knowledge obtained can be applied.
This study presents a self-cleaning cement incorporating zinc oxide and titanium dioxide nanoparticles, used alone or in combination. The objective is to develop high-performance materials suitable for different environments, inhibiting fungal growth while providing self-cleaning properties. In parallel, the impact of these nanoparticles on the mineralogy and structure of C-S-H was examined. Used as partial cement substitutes (0–3% by weight), the pastes were characterized after 28 days of hydration by XRD, XRF, DSC and TG to evaluate reactivity and Ca/Si ratios of the formed C-S-H. Next, a new alternative method for the indirect determination of the Ca/Si ratio of the C-S-H gel in cements is also proposed using three methods. The antimicrobial surfaces were assessed for antifungal activity against Penicillium brevicompactum, Trichoderma reesei and Aspergillus niger on Czapek-Dox agar. Results show that the addition of TiO₂ and ZnO yields fungal-resistant surfaces, promoting hygiene, sustainability and innovation in construction.
With the aim of manufacturing a clinker that reduces the energy consumption in its grinding, without substantially modifying the behavior of the cement manufactured with it, a characterization methodology based on the Rietveld method has been developed. From this study we have deduced that one of the most influential factors in the specific consumption of the cement mill is the C3S_M1 phase. Therefore, efforts will be focused on promoting its formation in the clinker by controlling the MgO content in the kiln feed and the alumina modulus in the clinker.
Geopolymer mortar from fly ash (FA) and field Para rubber latex (FPRL) with alkaline activators was exposed to 5% magnesium sulfate and sulfuric acid for 90 days with compressive strength. Key parameters assessed include compressive strength, expansion, degradation products, and microstructural changes, analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The study focused on heat-curing time and FPRL content. Samples were cured at 80°C for 0.5, 1, 2, or 4 hours, with FPRL added at 0%, 1%, 2.5%, and 5% by the weight of fly ash. The optimal mixture 1% FPRL with heat curing for 4 hours not only yielded the highest compressive strength but also effectively mitigated the loss of compressive strength caused by exposure to magnesium sulfate and sulfuric acid. Expansion decreased with higher FPRL content and longer curing times. SEM revealed diverse textures based on composition and a porous matrix caused by sulfuric acid erosion.
This paper investigates the use of sandy silt in 3D printing by stabilizing it with Portland cement and chemical additives (metakaolin and limestone filler). The goal is to make the soil compatible with the 3D printing process and ensure pumpability. The experimental program began with a reference mixture of soil to cement in a 1:1 mass ratio to achieve a consistency suitable for the extrusion method. The study also examined the content of chemical additives, the water-to-dry material ratio, printing speed, and nozzle height conditions. The analysis included the reduction of cement in two mixtures, T15%C and T20%C, with mass proportions of 0.15:0.85:1 and 0.2:0.80:1. It was confirmed that soil-cement blocks could be successfully produced with compressive strengths of 3.1 MPa and 3.0 MPa for the T15%C and T20%C compositions, respectively, indicating a cement reduction of 87% and 82% compared to the reference mixture (REFT100).
Concrete batching plants generate various types of waste, including residual slurry from the washing of ready-mix concrete trucks. This study aimed to analyze the mechanical properties of concrete produced with partial substitution (10%, 20%, and 30%) of the binder by the solid waste generated from washing ready-mix concrete trucks. Waste was physically and chemically characterized, and its pozzolanic activity was evaluated. Tests were conducted to analyze the concrete for slump and specific gravity in the fresh state, and compressive strength, water absorption by immersion, void index, and specific gravity in the hardened state. It was concluded that substituting up to 20% of the binder with waste did not significantly compromise the mechanical properties, highlighting the reduction in cement consumption, which brought sustainability advantages. Furthermore, the chemical analysis indicated that the presence of phases such as C-S-H and Portlandite in waste could positively influence the properties of the concrete.
The use of recycled polyethylene terephthalate (PET) with pine wood shavings was analyzed in the particleboard manufacture using hot-pressing. 160 °C was considered to avoid moisture build-up in the resin structure and polymer degradation and, property losses. 50% Pine with 40% PET and 10% polyurethane resin (PUR) and 50% Pine with 50% PET and 0% PUR were studied traits. Density, thickness swelling, water absorption, modulus of rupture, modulus of elasticity, perpendicular tensile properties and scanning electron microscopy (SEM) were studied. Density was close to 1 g/cm³, classifying both traits as high-density panels according to the standard code. SEM showed that 160 °C provided an effective envelopment of wood shavings. Physical and mechanical panel properties were superior to the minimum values of standard codes in 10% PUR trait, while they were lower with 0% PUR.
In response to the global trend towards achieving net zero emissions, various industries are actively promoting the circular economy. Central to this goal is the strategic utilization of alternative materials to replace virgin materials, thereby reducing carbon emissions during the production and manufacturing processes. This study uses the maximum density line in the FHWA 0.45 power curve to determine the oyster shell powder (OSP) as a substitute for 6% of the fine aggregate and filler in dense-graded asphalt concrete (DGAC). With properties similar to calcium carbonate (CaCO3) and hydrated lime, the inclusion of OSP was expected to enhance the performance of DGAC. For the Experimental Group, 6% of the fine aggregate and filler were replaced with OSP in the DGAC. The control groups used natural aggregate without hydrated lime anti-strip additive (Control Group A) and with hydrated lime anti-strip additive (Control Group B) in the DGAC. The aim was to assess the impact of replacing partial fine aggregate and filler with OSP on the performance of AC. The results indicated that while the Marshall stability, Marshall flow, and indirect tensile strength test values of the Experimental Group were lower than those of Control Group B, they were consistent with the results of Control Group A and complied with AI MS-2 7th. Subsequent evaluations, including the boil test, immersion-compression test, and tensile strength ratio, were conducted to assess moisture damage resistance. This revealed that the Experimental Group and Control Group B exhibited comparable and superior moisture damage resistance compared to Control Group A. Additionally, the Experimental Group outperforms the Control Groups in the Cantabro abrasion test. In summary, the OSP as a substitute for 6% of the fine aggregate and filler enhances the performance of AC, providing effects similar to hydrated lime anti-strip additives and increases moisture damage resistance. This study confirms that using recycled materials such as OSP to replace aggregates in AC, contributing to the goals of energy-saving and carbon reduction in road engineering.
The present study aims to expand the understanding of cementitious mixtures with low cement content and high levels of mineral additions and aggregates in order to assess their influence on the constructive characteristics of printing elements representative of structural masonry. The printing parameters and geometry of the pieces were defined to create a structure that can stand without internal bracing, with the goal of making the masonry construction process faster and simpler to print. In the hardened state, water absorption, the compressive and flexural strength of small pieces, as well as the compressive strength of 3DCP blocks and layer bonding, were evaluated. The results demonstrate that, for the parameters adopted in the printing system used, it is possible to construct volumetric masonry elements with mixtures that have higher aggregate content and partial cement replacement with limestone filler and metakaolin, achieving satisfactory results in buildability, mechanical strength, and efficiency.
The present study evaluated the mechanical performance of a warm-mix asphalt (WMA) by partially replacing the coarse fraction of natural aggregates (NA) with recycled concrete aggregates – RCA. To manufacture the WMA, a sodium silicate (SS) was used to modify and foam the asphalt cement (AC). SS is presented as a novel additive that has not been investigated by the technical and academic community. Based on penetration and softening point tests carried out on modified AC in different proportions (SS/AC=0.25, 0.50, 0.75, 1.0, 1.25, 1.50% by mass), a content of SS/AC=1% was defined as optimum. Viscosity tests, rheological characterization, and Scanning Electron Microscope (SEM) observations were performed on the modified and unmodified AC. Marshall, Indirect Tensile Strength – ITS, resilient modulus, permanent deformation, fatigue, and Cantabro tests were carried out on the asphalt mixtures. The SS allows a 20°C reduction in the mixing temperature, generating WMA mixes that exhibit similar or even better performance compared to the Control HMA. The mixes with RCA exhibited higher resistance in the Marshall test and similar resistance to permanent deformation with respect to the Control mix, but lower resistance to indirect tension, raveling, fatigue and moisture damage.
Geopolymer concrete is an eco-friendly alternative to cement concrete that reduces carbon emissions through the utilisation of industrial waste. This study enhances its sustainability by incorporating recycled asphalt pavement (RAP) aggregates as partial replacements for natural coarse aggregate at 0%, 20%, 40%, 60%, 80%, and 100%, using fly ash and dolomite as binders. The analysis revealed improvements within a specific RAP threshold, with 40% identified as the optimum proportion. Strong correlations (R2 > 0.90) were observed among compressive, flexural, split tensile strength and ultrasonic pulse velocity at 28 and 56 days. SEM-EDS analyses indicated a denser matrix, while XRD and FTIR confirmed the formation of C(N)–A–S–H type gels. These findings demonstrate the potential of RAP in geopolymer concrete, promoting sustainable construction through efficient material reuse.
This study employs Electrical Resistivity Tomography (ERT) to analyze moisture dynamics in an adobe wall of Casa Ter & aacute;n, a historic building in Aguascalientes, Mexico. By modifying the ERT technique with medical electrostimulators, the study identifies the causes and propagation patterns of moisture based on material properties. Previous interventions are also reviewed to determine the materials used. By integrating geotechnical and geoelectrical data, the study evaluates subsurface saturation levels, moisture propagation zones, and potentially weak areas in the wall. The correlation of ERT derived models with intervention images helps interpret the influence of construction materials on moisture propagation. This research is crucial for conserving historic structures and mitigating moisture-induced damages.
This study proposed thermal activation to activate copper tailings and investigated the effects of the temperature of thermal activation on the hydration properties, pore structure, and compressive strength of thermally activated CT (TCT) pastes. The results indicate that thermal activation slightly refines the particle size of CT and induces the decomposition of CaCO3, leading to the formation of highly reactive CaO. Compared to raw CT, the addition of calcined CT in the pastes resulted in a greater quantity of early hydration products, with increases of 0.34%—5.6% in C-S-H and ettringite, and approximately 0.9%—15.7% in Ca(OH)2. These changes facilitated a reduction in paste porosity, resulting in a more densified structure. Consequently, the compressive strength of TCT pastes increased by 6.8%—20.6% at 3d, by 5%—16.9% at 7d, and by 1.2%—13.5% at 28d. Therefore, the proposed thermal activation CT can be a promising cement substitution.
Superabsorbent polymers (SAP) are powdered chemical mixtures with the potential to significantly impact of cement-based materials in both fresh and hardened states. SAP's ability to absorb and release water makes it suitable for internal curing, preventing unhydrated cement, and influencing the hydration process. This study aimed to evaluate the SAP as an internal curing medium in low water-to-cement ratio cement based materials using X-Ray mu CT for image processing. SAP increased the compressive strength by 17.4% due to densification within the capillary pores, evidenced by a decrease in pore peak thickness and no increase in percolated voids. In swollen state, SAP particle appears as complete circle at close to the surface and ring-like shape in the center. Furthermore, an assessment of durability was performed through capillary absorption within crack pathways. Specimen without SAP displayed a 2.7 times greater penetration than specimen with SAP, indicating a significant impact on the durability.
Coating mortars must have properties that guarantee good performance in construction. Expanded vermiculite, as a substitute for fine aggregate, reduces thermal conductivity, specific mass and mechanical strength, which requires studying the levels of substitution. This study evaluated 1:1:6 mortars (cement:lime:aggregate) with a vermiculite replacement between 25% and 100%. Tests were carried out to evaluate energy efficiency, thermal conductivity, diffusivity, density, porosity and compressive and tensile strength. The results showed that mortars with a vermiculite replacement of 25% and 50% offered the best balance between thermal and mechanical properties, being suitable as coatings to improve thermal performance without compromising mechanical strength.
Waste from one industry can often serve as raw material for another. Previous research has shown that sewage sludge stabilized with biomass ash can form a construction composite with “Controlled Low-Strength Material” properties. This study focuses on the microstructural properties of such composites over time, investigating changes in phase composition and pore size distribution, as well as susceptibility to carbonation. Techniques such as X-ray powder diffraction, Fourier transformation infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, mercury porosimetry, and nitrogen gas sorption were employed. Results indicated that ash, a fine-grained, calcium-rich material, promotes new phase formation when combined with sewage sludge. Over time, common hydration phases like C-A-H and C-(A-)S-H were identified. The research demonstrated a direct correlation between microstructure development and phase evolution in the construction composite.
