93887 research outputs found
Sort by
Efficiency of Microstructural Reinforcement for Concrete in Tension
No full textWhile fiber reinforcement in concrete has been used for more than 60+ years, the adoption of enhanced tensile properties using secondary reinforcement to focus on serviceability and efficiency are still under development. The key role of various fiber reinforcement systems is to improve the design efficiency in concrete. A better understanding of such alternative reinforcement strategies in the development hybrid reinforcing systems such as Ultra-High-Performance Concrete (UHPC), Textile reinforced concrete (TRC), and hybrid applications are needed. Our research activity focuses on an overview of test developments with closed loop control tension, flexure, high-speed, impact, fatigue, full-structural scale, and creep tests. Models based on non-linear fracture, strain energy dissipation using R-Curves, and plasticity- based moment-curvature section properties are used. Design tools are provided to reduce the volume of the section and rebars while improving the durability
Investigation of Corrosion Resistance of Fly ash Self-compacting Mortar
No full textOne of the leading reasons for failure of structural members is corrosion of reinforcement. Structures corresponding to the marine environment like ports, harbours and bridges are more susceptible towards the risk of corrosion. Chlorides are one of the main reasons for the initiation of corrosion which can penetrate from various sources like the marine atmospheric environment or the use of deicing salts in the colder regions. Corrosion is a long-term process, so, in this research, an accelerated corrosion testing of self-compacting mortar has been performed to understand the behaviour of addition of fly ash in the mortar mixes against the chloride induced corrosion. Mix design of self-compacting mortar was done through the effective cement replacement or k-factor theory based on the concept of equivalent 28 days strength. Altogether 12 mixes have been casted, 6 for each effective w/c of 0.44 and 0.5 with variation in the fly ash incorporation in the mixes (0-55%). Accelerated corrosion test using impressed current technique is used for the evaluation of corrosion resistance of mortar for which the centrally embedded reinforced (rebar of diameter 12 mm and length 200mm) mortar sample having diameter of 100mm and height 200 mm is casted. Testing of mortar samples are performed after 28 days of curing
Decalcification of Calcium Silicate Hydrate by Sulfate Attack: Material Degradation by Heterogeneous Charges
No full textSulfate attack is a key factor limiting the durability of concrete in aggressive environments, primarily through the degradation of calcium silicate hydrate (C–S–H), the main binding phase of cement. This study investigates the molecular mechanisms of C–S–H decalcification under sulfate exposure by combining semi-empirical Born–Oppenheimer molecular dynamics (BOMD) with density functional theory (DFT). A C–S–H model with a Ca/Si ratio of 1.5 was simulated in aqueous environments with and without sulfate ions. BOMD trajectories revealed that while C–S–H remained largely stable in pure water, sulfate ions rapidly promoted Ca²⁺ desorption, leading to silicate chain fragmentation and Q²→Q¹ transitions. Electronic structure analyses, including reduced density gradient (RDG), electron localisation function (ELF), and bond critical point (BCP) methods, confirmed stronger Ca²⁺–sulfate interactions compared to Ca²⁺–silicate, driving competitive calcium extraction. DFT calculations showed that sulfate significantly lowers the energy barriers for decalcification and silicate chain fracture, with water amplifying these effects by enhancing polarity and hydrogen bonding. These results reveal how sulfate ions destabilise C–S–H at the molecular level, providing fundamental insights into the mechanisms of concrete deterioration in aggressive environments and guiding strategies for designing more durable cementitious materials
Effect of Carbonation on Rebar Corrosion in MgO-SiO2 Binder Concrete
No full textMgO-SiO2 binders are a promising alternative to Portland cement (PC) offering comparable strength performance to the conventional PC concrete. However, their application in reinforced concrete has been limited due to the inherently low pH of these binders. This study investigated the mechanical, microstructural, and corrosion performance of MgO-SiO2 binder concrete after carbonation. MgO-SiO2 concrete samples were subjected to 14 days of carbonation and subsequently tested after one year. The degree of carbonation was evaluated using thermogravimetric analysis while corrosion assessment was done using Wenner four-probe resistivity meter, half-cell potential and a handled device called Rapicor. The results showed that MgO-SiO2 binder gained a comparable strength to PC after carbonation. Despite exhibiting a lower carbonation degree, higher pore refinement was attained in MgO-SiO2 binder as compared to PC suggested by the surface resistivity assessments. Additionally, a significant reduction in corrosion rate was observed due to the refined pore structure after carbonation. Overall, the findings suggested that carbonation of concrete cover can have beneficial effect on the corrosion performance of MgO-SiO2 binders
Towards the Use of Quarry Wastes in Cementitious Composites for Sustainable Construction
No full textThis study explores the use of quarry waste powders as partial replacements for cement in concrete, aiming to improve the sustainability of construction materials. Three types of powders—granite (GP), limestone (LP), and quartz (QP)—were used to replace 20% of cement by mass in concrete mixes. The research evaluates the impact of these substitutions on fresh properties, mechanical performance, durability under sulphate attack, and overall environmental and economic efficiency. Experimental tests included slump flow, setting time, compressive strength at 28 and 90 days, and resistance to sulphate-induced mass and strength loss. Additionally, carbon dioxide emissions and material costs were calculated based on unit values for each component, and two performance indicators—Effective Cost Ratio (ECR) and Effective Emission Ratio (EER)—were introduced. The results show that GP20 offered the most favourable performance, balancing strength, durability, and sustainability. LP20 improved workability but showed lower strength and reduced durability. QP20 demonstrated moderate strength and improved sulphate resistance but required careful mix design. All quarry waste-modified mixes significantly reduced cost and embodied emissions compared to the reference concrete. The findings highlight the potential of quarry wastes as viable, low-impact supplementary materials in cementitious composites and support their integration into circular economy strategies for the construction industry
Drying Shrinkage Properties of Fly Ash Concrete
No full textShrinkage of concrete is a prime aspect affecting the durability and long-term performance of structures. IS 456 specifies the minimum cement content required to control shrinkage, which is of utmost importance in high-strength concrete (M75, M60) and lower strength concrete (M30), to be 450 kg/m³. IS456 mentions that shrinkage testing should be conducted to assess the possible decrease in volume due to moisture loss since excessive shrinkage can lead to cracking and the loss of structural integrity. However, codal provision or requirement is mentioned in the code. The literature available about shrinkage with change with fly ash is extremely limited. This study utilises a mix design approach based on the k-factor theory in which the effective water-to-cement ratio is defined as Ratio w to (c + k*f), thus ensuring optimum performance while incorporating fly ash as a partial cement replacement. The k-factor approach considers fly ash efficiency in concrete while its 28 days compressive strength is maintained equal. Drying shrinkage is measured using IS1199 and ASTMC157, and initial comparative study is presented for varying fly ash% for M15 (0,25%,45%), M35 (0,25%,35%), and M50(0,25%) concrete with effective water cement of 0.6,0.4 and 0.33
Thermo-Mechanical Behaviour of Preloaded Low Cement Concrete under Heating and Cooling Phase of Fire Exposure
No full textUnderstanding the structural performance of concrete under fire, particularly during the cooling phase, is critical to ensuring post-fire safety. Concrete columns, as primary load-bearing elements, are especially vulnerable under such conditions. While Ordinary Portland Cement (OPC) concrete has been widely studied in fire, limited research has addressed the behaviour of sustainable alternatives such as Ground Granulated Blast Furnace Slag (GGBS) concrete, particularly under realistic thermal decay scenarios. GGBS, a by-product of steel production, offers a low-carbon alternative to OPC, reducing embodied CO₂ while enhancing long-term durability. This study investigates the fire response of 100 mm × 200 mm cylindrical specimens made with OPC (CS1) and 50% GGBS replacement (CS2). All specimens were preloaded to 30% of their 90-day compressive strength, heated to 600 °C at a rate of 10 °C/min, and cooled to ambient, 200 °C, or 400 °C under sustained loading. Digital Image Correlation (DIC) was used to monitor axial strain, and post-fire residual strength was measured. Results show that staged cooling improved strength retention in both mixes. CS1 retained 65–78% of its original strength, while CS2 retained 57–70%. CS2 exhibited slightly lower residual strength but showed stable behaviour and consistent failure patterns, likely due to its denser microstructure and lower thermal conductivity. DIC analysis revealed typical expansion followed by contraction, with reduced strain recovery in CS2, suggesting altered post-fire stiffness characteristics. These findings confirm the potential of GGBS concrete as a reliable, lower-carbon alternative in fire-exposed structural applications without compromising safety performance
Supporting Personal, Familial, Academic, and Community Assets in Latino Youth through Connectedness
No full textDuring adolescence, many families begin preparing for their child’s transition to adulthood by focusing on their academic success. Families from Latino backgrounds who live in rural counties often lack the resources and have limited access to community supports to help their child successfully navigate this developmental period. Community-based organizations can support Latino families by building their students’ academic skills and awareness in a learning environment designed to foster belongingness at school, at home and in their community. To understand how programs strive to build these assets, eleven program leaders from an academic success program, who were primarily female (n = 11) and from Latino backgrounds (n = 7), were invited to participate in a focus group about their experiences supporting Latino students, and the degree that programs can foster desirable outcomes at the student, familial, program and community levels. Drawing from the perspectives of developmental systems theory and community capacity development, focus groups were analyzed using the lens of constructivism. Participants communicated that the program helped build a supportive network of caring adults and peers, offered an avenue to deliver quality academic programming for youth, and enabled families to build skills to support their child’s academic success. The program also created a space for participants to build a sense of community and a place for outside organizations to contribute to their shared aims. Leaders indicated that as a member of the local Latino community, the opportunity to serve youth was personally beneficial as it supported their own growth and wellbeing. This project demonstrates the value of a multidisciplinary team that creates opportunities for collaboration among researchers, practitioners, and community members to understand how to better support Latino youth and families to promote academic social justice
“It Would Literally Take the World to End for Us to Do This”: Writing Center Consultants’ Affective Responses to Consulting Modalities
No full textThis article discusses findings from semi-structured interviews with writing consultants about their affective experiences working across three different consulting modalities: in person, asynchronous, and synchronous. This study offers affect as a lens for understanding consultants’ responses to and strategies for consulting in multiple modalities and argues that by attending to affect, emotion, and disposition in consulting we can better support our consultants when they’re consulting in different modalities