93887 research outputs found
Sort by
Using Fluid Absorption Modeling to Determine the Intrinsic Permeability of Cement-Based Materials
No full textNeutron radiography (NR) is used during unidirectional fluid absorption experiments to obtain moisture profiles through the height of mortar specimens. The moisture profiles are compared to the results of an established fluid absorption modeling technique, and linear interpolation is used to accurately determine the intrinsic permeability (Kl) of all samples
Cold-Compacted Concrete Waste Composites – Sustainable Low-Carbon Materials: Effect of Original Concrete Quality
No full textA compacted concrete waste composite material (CWC) is developed using a cold compaction approach with recycled concrete waste particles, without the use of cement. This study aims to investigate the effects of carbonation and the original quality of the concrete waste (CW) particles on the properties of composite material, with the goal of proposing a pretreatment of concrete waste particles which proposed for CO2 sequestered for producing CWC with attained strength. This study found that the original quality of the CW strongly affects the properties of the CWC
Predicting the Chloride Penetration of Sustainable Marine Concrete Using Data-driven and Multiphysics Frameworks
No full textChloride penetration in sustainable reinforced concrete (RC) is a critical parameter for predicting and preventing infrastructure failure, particularly for marine applications. However, replicating natural environments and testing in actual infrastructure is challenging, making it difficult to accurately measure chloride concentration in RC. Additionally, the complexity of concrete mixture designs and environmental parameters hinders the development of a universal model to predict chloride concentration at various concrete depths. This study develops a data-driven approach to predict chloride concentrations at different depths and chloride diffusion coefficients in marine RC made with common supplementary cementitious materials (e.g. fly ash, slag, etc.) under varied environmental conditions and exposure times (including both short- and long-term). Furthermore, the study leverages porosity obtained from thermodynamic simulations as a bridge to establish correlations between compressive strength and chloride diffusion coefficients. This approach enables a practical estimation of chloride diffusion coefficients in marine concrete based on simple compressive strength measurements
Comparative Analysis of the Corrosion Resistance Epoxy-Coated, Textured Epoxy-Coated, and uncoated Reinforcement Bars
No full textThe corrosion of steel reinforcement inside concrete remains a significant challenge for the construction industry. In the United States alone, an estimated annual cost of $240 billion is incurred from corrosion-related damage, with about 20% attributed to the corrosion of reinforced concrete [1]. Among various corrosion prevention techniques for reinforced concrete, epoxy coating of rebars (EC), has been widely adopted. However, due to the smooth surface of epoxy coating, its bond strength with concrete is reduced significantly, which has become a barrier for its large-scale adoption [2]. To tackle this, Sherwin Williams developed textured epoxy coated rebars (TEC) (figure 1a) with feature enhanced surface roughness and enhanced bond strength [3], [4]. The purpose of this study is to investigate how the texturizing coating (figure 1b) impacts their corrosion resistance. While the additional texturizing layer may increase overall coating thickness, potentially improving corrosion resistance, existing literature indicates that corrosion in EC rebars typically initiates and propagates through coating defects (holidays), rendering additional layers ineffective [5], [6]. Additionally, the hydrophobicity induced at the steel concrete interface by the increased roughness of the TEC might also affect the progression of cathodic and anodic areas at the coating boundary with the holidays. To answer these questions, this study investigates the corrosion resistance of undamaged and damaged (holiday induced) EC and TEC bars along with uncoated steel bars using ASTM G-109 macrocell tests. The comparison of damaged and undamaged rebars addresses longstanding questions related to the corrosion mechanisms of coated rebars as well
LEaPP Basic and Advanced Spelling Inventories
No full textThe LEaPP Basic and Advanced Spelling Inventories are educational tools to systematically map and track a learner’s ability to encode words containing spelling features along a progression. The Basic screener starts with single graphemes and closed syllable words and moves through additional concepts such as digraphs, blends, VCe, vocalic r, basic vowel teams, and basic roots and affixes. The Advanced screener starts with beginning advanced code such as blends and moves through additional advanced concepts such as vocalic r, vowel teams, diphthongs, complex consonants, roots, affixes, and syllable junctures. The screeners can be used in part or whole and can be repeated as needed for progress monitoring. This document contains directions for use, basic and advanced screening inventories with data analysis tables, learner response form, and a class composite form. The class composite form allows the educator to track performance of the entire class. Data from the spelling inventories can be mapped to the scope and sequence progress monitoring form to help determine point of instruction
Book Review of Koan Khmer: A Novel
No full textOn rare occasions, I come across a book that truly resonates with me, with storylines and narrator enquiries that echo my own, and characters whose dispositions harken back to my own family members, friends, and myself. As the U.S.-born daughter of a Khmer (Cambodian) father, this is a rare occurrence. This is not to say that I do not enjoy reading works of fiction that transport me to other worlds or allow me to see things through the eyes of someone whose experiences are vastly different than mine—I do. Yet I long for narratives that offer familiarity, understanding, and a sense of belonging. I found these in Bunkong Tuon’s recent novel, Koan Khmer. Tuon deftly weaves more universal emotions—anger, grief, hope—with the main character’s (Samnang’s) intimate thoughts to represent the enigmatic space occupied by 1.5 and 2.0 generation Cambodian Americans. As such, it is a welcome addition to Southeast Asian American literature, a coming-of-age story complicated by the disruption of war and the refugee experience
Surface Morphology, Bond Strength and Failure Behaviour of Steel vs Basalt Rebars in Alkali Activated Concrete
No full textThis microscopic characteristics of basalt bars after exposure to alkaline solutions and pullout performance of steel and basalt rebars embedded in conventional and alkali-activated concrete were studied. The overarching goal is to assess the potential of basalt rebars as an alternative to conventional steel reinforcement in alkali activated concrete elements. To understand their durability in alkaline environments, especially within alkali-activated concrete (AAC), steel and basalt rebars were subjected to an accelerated exposure test in high-pH simulated concrete pore solutions, for 24hrs. This aimed to replicate the aggressive internal environment typically found in AAC and mixes with supplementary cementitious materials. Post-exposure microscopic inspection revealed morphological changes, but the changes were limited to the adhesives and did not influence the basalt fibre bundles. Pullout tests were conducted in reference to BS EN 1881:2006, using a 50:50 blend of CEM I and GGBS. AAC mixes used 6% and 8% alkali dosages. Both steel and basalt rebars exceeded the 75kN standard threshold. Steel rebars reached up to 115kN, while basalt rebars recorded 100–120kN. Predominant failure mode was midsection concrete splitting. Slightly higher bond strength in basalt-reinforced AAC samples may result from interface roughening caused by the initial high alkaline exposure(i.e., to activator solution). These findings highlight the viability of basalt rebars as a low-carbon, structurally reliable alternative to steel in AAC systems
Evaluation of Ionic Behaviours under Electric Field with Integrated Chemo-electric Numerical Platform
No full textChloride ion plays a critical role in terms of steel corrosion for reinforced concrete structures, which leads to structural degradation. To investigate the macro-cell corrosion and mechanical deterioration, an integrated chemo-electric numerical platform has been developed with spatial-averaged modelling of steel and concrete. The verification of macro-cell circuit in structural concrete induced by applied charge has been achieved, while the ionic behaviors under impressed charge evaluated by this platform remains unverified. This study numerically investigates the ionic behavior of chloride under both ponding and electrophoresis conditions with the integrated platform. Comparison between numerical simulation and available experimental data shows the capability of this platform on predicting the time-dependent profiles of chloride ion under external charge. The acceleration effect of an applied electric field is obtained through simulation, and a sensitivity analysis is performed on peak radius of capillary pores and constricitivity parameter for electrical interaction of the matrix. The results indicate that while the previous constrictivity model successfully reproduces chloride profiles for the ponding test, it should be modified to account for the effect of applied charge on ionic migration through micro-pores under electrophoresis conditions
Structural Behaviour of Preflex Beams in Bridges during Concrete Repair and Maintenance
No full textPreflex beams are composite structural members that combine a steel universal beam with reinforced concrete, enabling longer spans with reduced deflection. Their strength and stiffness rely on a preflexion process, where the bottom flange is initially placed in tension and later compressed by the surrounding concrete. Despite their advantages, repairing preflex beams, particularly the bottom flange concrete, presents challenges due to its role in load distribution and deflection control. This study investigates the structural behaviour of preflex beams when the bottom flange concrete, an integral component of the load distribution mechanism, is altered during concrete repairs, addressing the need for a reliable repair methodology that ensures structural integrity. The research primarily aims to develop a robust repair methodology, specifically addressing the bottom flange concrete in preflex beams. Through a comprehensive literature review, this study examines the historical development, key attributes, and existing repair strategies for these beams. The findings reveal that while the bottom flange concrete plays a crucial role in limiting excessive deflection, its contribution to the ultimate strength of the beam is relatively minor. Consequently, the repair approach must consider the interaction of the bottom flange with other structural elements. Based on these insights, this research proposes a structured repair philosophy adaptable to various bridge configurations, facilitating the long-term maintenance and durability of preflex beam structures