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Durability of Sisal Fibers Reinforced Cement-based Plates
No full textSustainable materials have been gaining increasing attention in the construction sector due to their environmental advantages and the need for cost-effective solutions. An example of this is vegetable fibers, which are recognized as a sustainable and eco-friendly alternative for the reinforcement of cementitious composites in civil engineering applications. To contribute to our knowledge about the durability of these materials, this study investigated the mechanical behavior of cementitious plates reinforced with 5% long aligned sisal fibers materials after being subjected to accelerated aging. To improve the durability of the composite, 50% of the cement in matrix was replaced by 40% metakaolin and 10% fly ash, to avoid fiber degradation by alkaline attack. Two accelerated aging methods were carried out according to the NBR15498 guidelines: (1) hot water immersion and (2) immersion-drying cycles; and compared with the reference samples. Flexural tensile tests were performed after the aging. The average strength of the reference samples was 16.03 ± 1.50 MPa, while the samples subjected to hot water immersion was 17.19 ± 1.93 MPa. The average tensile strength of the samples subjected to accelerated aging through immersion-drying cycles and the reference samples was 18.48 ± 2.56 MPa and 17.82 ± 1.45 MPa, respectively. The results showed that the material preserves its performance after both accelerated aging methods in comparison to reference samples
Fresh and Mechanical Properties of the Ultra-High-Performance Concrete with Cellulose Nanofibers
No full textWater-sensitive cellulose significantly impacts the performance of the ultra-high-performance concrete (UHPC), leading to variations in its fresh and mechanical properties of fresh and hardened concrete materials. In this study, the cellulose nanofibers, a more environmentally friendly class of nanomaterials, are introduced into UHPC. The rheological and mechanical properties of UHPC are investigated, including viscosity, yield stress and compressive strength. The results reveal significant effect of cellulose nanofibers on the properties of UHPC in terms of material performance and sustainability. Advanced characterization techniques, including isothermal calorimetry, thermogravimetric analysis (TGA), and X-ray diffraction (XRD) are employed to study the effect of cellulose nanofibers on the hydration process of UHPC. Furthermore, microstructural characterization techniques, such as scanning electron microscopy (SEM) are utilized to investigate the impact of cellulose nanofibers on the performance of UHPC from micro-scale level of the materials
Engineering Performance of Semi-flowable Concrete with High-Volume Indigenous SCMs
No full textEnhancing clinker efficiency and increasing limestone filler (LF) in binder are essential for engineering applications. This study explores the high-volume substitution of Portland cement, with 50 wt.% LF and up to 30 wt.% traditional SCMs, in semi-flowable concrete (SFC), evaluating properties of SFC. A slump of 200 mm was achieved, with retentions above 130 mm after 70 minutes for SFC mixtures. The 28-day compressive and flexural strengths of SFC exceeded 30 MPa and 3.2 MPa, respectively, meeting structural performance benchmarks (ACI 318, ASTM C94). LF replacement rate in binder exceeding 10% reduces strength of SFC due to LF’s lack of cementitious and pozzolanic properties. The results demonstrate the potential of SFC with 50 wt.% LF and partial SCMs to significantly reduce clinker content while maintaining mechanical properties, supporting sustainable construction practices
Recent Advances in Geopolymer Feedstocks Activation for Sustainable Cement Production
No full textThe growing environmental and safety issues posed by human activities have underlined the importance of Ordinary Portland Cement production, which is a major contributor to carbon dioxide emissions that impede Net Zero goals. The urgent need to produce cement substitutes with reduced carbon footprints has prompted research on geopolymers formed from industrial mineral wastes. These materials provide promising sustainable development solutions, but the selection of appropriate activation methods remains a significant constraint to their widespread industrial and economical application. A systematic review using the PRISMA protocol included 302 recent and relevant papers, identifying four principal activation strategies and their combinations across four major feedstocks. The study investigated energy requirements, compressive strength, and industrial applications. Hybrid activation, particularly when combined with mechanical activation, emerged as the most successful method for creating geopolymers with high compressive strength. Among the methods investigated, mechanochemical activation of slag produced the maximum compressive strength, while microwave-assisted treatment (MAT) activation of clay and ultrasonic activation of fly ash mixed with slag provided the most energy-efficient curing procedure. Hybrid activation represents the most recent innovation in geopolymer research, offering increased efficiency and industrial viability. Future advancements are projected to improve the integration of hybrid approaches with mechanical activation, increasing performance while reducing the impact on the environment
Fractal Characterisation of Crack Tortuosity and Its Correlation with Permeability in Concrete
No full textThis study investigated fracture behaviour in four concrete grades (C40-C70) through controlled splitting tests. Using high-resolution 3D profilometry, we quantitatively characterised crack surface morphology and proposed a novel fractal dimension metric for tortuosity D_T. Post-repair permeability tests on 12 specimens (24 fracture surfaces) revealed: (1) conventional tortuosity showed weak permeability correlation (R²\u3c0.350), while (2) D_T demonstrated superior predictive capability (R²=0.430). The developed fractal tortuosity index provides a robust multiscale quantification method for crack flow mechanism analysis
Influence of Superabsorbent Polymer on Workability, Strength, and Shrinkage of Mortars with Plain and Slag-Cement Binders
No full textAs the global construction industry moves toward more environmentally responsible solutions, achieving both durability and sustainability goals in cement-based materials has become increasingly important. One of the main challenges in this effort is to effectively and economically achieve the desired levels of workability and strength of sustainably designed mixtures, controlling their early-age shrinkage, which can reduce long-term performance and service life. This study explores the integration of superabsorbent polymers (SAPs), a promising internal curing agent, into plain and slag-cement mortar systems made with Type IL cement to enhance their dimensional stability while promoting sustainability. The experimental program evaluates mortars modified with 0.2% SAP by weight of binder and colloidal nanosilica in both plain Type IL and slag-blended binder systems at constant water -binder (w/b) ratio of 0.44. The scope of the study included evaluation of fresh properties (workability and air content), strength development (flexural and compressive), changes in stiffness (using ultrasonic pulse velocity measurements) and shrinkage (autogenous and drying). Results indicate that the incorporation of SAP significantly improved the strength and stiffness of mortar mixtures. The incorporation of SAP also mitigated drying shrinkage, particularly in slag-modified mixes, which are typically more susceptible to volumetric changes due to their finer pore structure and lower early-age rate of strength development. Autogenous shrinkage measurements show that the initial phase of shrinking, the SAP-modified mixtures displayed rapid stabilisation of deformations, reflecting the onset of water release. This implies that SAP effectively fulfils its internal curing function by providing additional water during the critical period of autogenous strain development. The overall findings reinforce the viability of using SAPs to balance performance and sustainability objectives, especially in mixtures using supplementary cementitious materials
Enhancing Concrete Circularity in Construction: the RecycleBIM Framework in Closing Material Loops
No full textDespite significant progress in digitalisation across various sectors, the development of data-driven applications in the built environment remains ongoing, with a focus on improving labour productivity and addressing global sustainability challenges. The circular economy framework for reusing and recycling construction materials is still underexplored. Metrics on the amount and impact of construction and demolition waste (CDW) highlight the need for more effective circularity strategies. Although the circular economy seeks to minimise waste, maximise material reuse, and reduce environmental impacts, practical implementation within the construction sector requires further development—an area where digital technologies can offer substantial support. This study introduces the RecycleBIM framework, an integrated approach designed to enhance the circularity of construction materials by capitalising on the data-rich environment of BIM. The framework utilises several key enabling technologies, including cost-effective scan-to-BIM, open data formats for interoperability, model-based optimisation and decision-making, circular business models, and 3D printing, to identify, assess, and reuse materials sourced from the buildings at the end of life. By integrating BIM data representing the assets containing potential CDW and the amount of reusable and recyclable components, e.g., concrete, and linking it with regional marketplaces, RecycleBIM aims to close material loops and provide the inputs for new construction. Furthermore, the framework explores the use of recycled aggregates in 3D concrete printing and BIM-to-print workflows, presenting new opportunities for sustainable construction. The research combines developed methodologies with case study reviews to illustrate how BIM-driven collaboration can support a transition to more sustainable business models. By translating circular economy principles into actionable strategies, the study identifies opportunities for industry stakeholders and bridges digital technologies with real-world applications. This paper is a collaborative effort between the RecycleBIM (recyclebim.eu) and R2U (r2utechnologies.pt) projects. The findings contribute to the broader adoption of BIM for material recovery and reuse, thereby advancing sustainable construction and deconstruction practices
Toward Durable 3D Printed Structures
No full textDurability of 3-D printable concrete begins with control of flow and consolidation of the fresh material. 3D printed concrete needs to be fluid-like for pumping and extrusion but solid-like during placement to support the printed structure. High quality 3D printed materials must have excellent consolidation and a low volume of trapped voids. In practice, achieving this balance is challenging. This research addresses these challenges by leveraging machine learning and numerical simulation to model the fresh behavior of cement-based materials for 3-D printing. It begins with rheological characterisation to understand how mixture design factors influence rheological properties, laying the foundation for subsequent studies. A multilayer perception (MLP) model is developed to predict the yield stress of cement-based materials, achieving a desired overall accuracy while demonstrating performance variations on some subsets of data. Additionally, both Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPH) are utilised to model the flow behavior of cement-based materials in common flow scenarios. These 3-D printing simulations help us understand real-life issues such as jamming and plastic collapse. Vibration of the material in the printer nozzle was shown to be effective for improving extrusion and consistency during deposition. Machine learning and numerical simulation provided insights into design of 3-D printing materials and construction processes. This study found that computer modeling was able to capture behaviour, and thus serve as a design tool for new 3-D printable mixtures
In-situ Tests of Transport Properties of Near-surface Concrete
No full textDetermining the water permeability of concrete in structures remains a conundrum because of difficulties in removing the influences of moisture. This study describes the extended flow-net theory developed on the basis of the two-pressure head concept, which provides a means of measuring permeability under the partially saturated condition. Surface mounted tests and the standard laboratory water penetration tests were carried out to verify this approach. Before determining the water permeability, steady state flow rates at two different pressure levels were evaluated and the effects of initial moisture conditions on flow behaviour were investigated. The results indicate that the proposed approach does offer a useful means of determining the water permeability of structural concrete, although it cannot be claimed to be universally applicable for all moisture conditions likely to be encountered in practice
Simple Probabilistic Method for Chloride Transport in Concrete
No full textIt is a well-known fact that reinforced concrete structures exposed to marine environments suffer from reinforcement corrosion due to chloride ingress, which degrades the performance of the structure. To address this issue, reinforced concrete structures are designed and constructed to have a service life of more than 100 years, but to ensure safety or durability, it is necessary to accurately predict the onset of reinforcement corrosion. Various prediction models have been developed for chloride transport in concrete, including physically based models, with Fick\u27s 2nd law being the most commonly used empirically based model for chloride penetration in concrete. However, the results presented by these deterministic methods have obvious limitations in considering concrete with inhomogeneous material properties and different exposure environments. These limitations can be addressed by probabilistic methods, but their applicability is still challenging. In this study, a simplified probabilistic method is used to predict the onset of reinforcement corrosion in concrete exposed to the marine environment. The main probability distributions of diffusion coefficient, cover thickness, and surface chloride amount, which are the main coefficients of Fick\u27s 2nd law, are presented to predict the time of rebar corrosion initiation, and the probability of rebar corrosion