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Portable Inspection Technology For Shot Peening As Preventive Maintenance At Steel Bridges
No full textPositron annihilation lifetime spectroscopy (PALS) is a non-destructively technique to study open-volume lattice defects such as vacancies or dislocations, which is used for fatigue, aging and shot peening inspection. In this study, we developed a portable PALS apparatus that has the ability for on-site measurement[1,2]. We developed the light-shielding technique which enable us to do on-site measurement. Furthermore, we downsized the apparatus size using Monte Carlo simulation technique. We validated that the developed portable apparatus has the same measurement capabilities as the conventional system[1]. We concluded that the developed portable apparatus is sufficiently able to capture the change caused by shot-peening time and the aging of rust at actual bridge
Microstructural Changes And Residual Stress Generation On The Periodically Patterned Surface Texture Fabricated By Angled Fine Particle Peening
No full textFocusing on the potential of peening technology as a surface texturing technique, angled fine particle peening (angled-FPP) has been proposed to fabricate a specific periodical surface structure, which possibly provides various surface functions. It is necessary to further characterize the textured surface to earn more advantages from angled-FPP. Thus, in this paper, texture formation phenomena, residual stress, and microstructural changes were investigated on the angled-FPP specimens
Study on hydration kinetics of geopolymer synthesized with recycled concrete and brick powder
No full textConcrete and brick waste accounted for the majority of construction and demolition waste. In recent years, the use of recycled concrete powder (CP) and recycled brick powder (CP) to prepare geopolymer binders gained significant attention. This study investigated the hydration characteristics of geopolymer made from BP and CP using isothermal calorimetry and low-field nuclear magnetic resonance (1H NMR) techniques. The results showed that the incorporation of BP or CP reduced the heat release during geopolymer hydration. The degree of hydration of the geopolymer binder initially decreased and then increased as the addition of BP or CP increased, while the nucleation rate rose with the increasing content of BP or CP. Additionally, the study revealed that the geopolymer reaction process consisted of four distinct stages. The addition of 10% CP increased the rate of gel water production during the acceleration stage of the geopolymer reaction, While the incorporation of 10% BP had a smaller effect on the acceleration stage but prolonged the duration of the deceleration stage. However, when the recycled powder content reached 50%, the four-stage reaction process was no longer evident. The compressive strength test results showed that the compressive strength of the geopolymer increased and then decreased with the increase in BP dosage, with the highest strength observed at a dosage of 10%, reaching 54.1 MPa. In contrast, the compressive strength of the geopolymer doped with CP decreased as the CP replacement increased
Wet-Carbonation of RCAs for Improved Carbonation Efficiency and Mechanical Properties of Carbonated RCAs and RCA Concrete
No full textThe increasing volume of construction and demolition waste (C&DW) poses significant environmental challenges, making its effective management and treatment crucial. Recycled coarse aggregates (RCA), derived from C&DW, often exhibit weak interfacial transition zones (ITZ), high porosity, and micro-cracks due to residual mortar, limiting their structural performance [1] [2]. This study developed a novel wet carbonation process using glycine acid as an inducer to enhance the mechanical and durability properties of RCA and RCA concrete. Glycine acid, with carboxyl and amino functional groups, formed stable complexes with Ca²⁺ ions, increasing calcium solubility and accelerating carbonation[3]. The process promoted the formation of vaterite, a reactive calcium carbonate polymorph, on RCA surfaces, improving ITZ density and bonding strength with the cement matrix [4, 5]. As a result, abrasion loss decreased to 45.71%, compared to 53.82% for untreated RCA, and California Bearing Ratio (CBR) values increased by 28% at 5 mm penetration, indicating enhanced physical property. Leachate analysis showed carbonated RCA exhibited a reduced pH of 8.47 and lower total dissolved solids (0.263 mS), demonstrating environmental benefits. Mechanical tests of recycled concrete with carbonated RCA revealed strength increases of 13% in compression, 15% in tension, and 12% in flexure. Enhanced surface resistivity and Rapid Chloride Permeability Test (RCPT) results further indicated improved durability and resistance to chemical attacks. These results demonstrate that glycine acid-induced carbonation enhances RCA properties and possibly offers a promising pathway for mitigating construction and demolition waste
Upcycling Incineration Ash in Reactive Magnesium Oxide Cement: Effects of Carbonation
No full textOver the past decade, increased economic activity and population growth have led to a rise in global waste generation. Current waste management strategies focus on enhancing waste collection, recycling, and converting waste into energy through incineration. While waste incineration effectively reduces both mass and volume, it generates substantial residuals, including fly ash and bottom ash, which pose significant management challenges. Despite the potential of incineration ash, large-scale utilization remains limited, typically confined to applications such as road sub-base materials, landfill stabilizers, and cement additives. The construction industry’s reliance on concrete has spurred research into using incineration ash, but challenges such as low density, high heterogeneity, and the presence of toxic contaminants hinder its effectiveness. Reactive magnesium oxide cement (RMC) has attracted attention due to its ability to sequester carbon dioxide (CO2). This study investigates the potential of replacing RMC with 10% and 20% by mass of incineration ash in mortar. Six types of fly ash were analyzed for chemical composition and particle size, and the behavior of RMC-ash pastes was studied. Results indicate that limited ash replacement remains beneficial, offering environmental advantages like waste reduction and the production of value-added materials from byproducts
Computer Vision-Driven Sorptivity Tests for Cementitious Materials
No full textAssessing water absorption, or \u27sorptivity,\u27 in cement-based materials is a crucial method for evaluating durability. The ASTM C1585 standard provides a straightforward approach for measuring sorptivity, yet it is often labor-intensive and time-consuming. This study presents two innovative strategies to accelerate and automate sorptivity measurements through computer vision. The first method involves a droplet test, demonstrating that the initial dynamics of a water droplet\u27s contact angle, characterized by CNNs, strongly predict the initial sorptivity of paste samples. By analyzing data from 63 different paste systems, this method estimates the 6-hour initial sorptivity in mere seconds. The second method utilizes a vision-based algorithm to monitor the advancing waterfront in a sample, leveraging the wetted area ratio to predict sorptivity and streamline the measurement process. By training the algorithm on a dataset of over 6,000 images and 1,400 data points, the system achieves real-time predictions of initial and secondary sorptivities with an R² exceeding 0.9, closely aligning with ASTM standards. These cost-effective solutions, using cameras priced at around $30, provide laboratories worldwide with an accessible and automated method to enhance sorptivity testing, especially for assessing the durability of new low-carbon cementitious materials
REBEL Sensor for Real-Time Concrete Strength: Eliminating Calibration and Reducing Carbon Footprint
No full textConcrete strength is a key factor influencing construction quality, cost, schedule, and durability. However, current testing methods—such as cylinder and beam breaks—are time-consuming, costly, and carbon-intensive, often delaying construction and generating unnecessary waste. Existing maturity methods (e.g., ASTM C1074) also require pre-established, mix-specific curves that take weeks and thousands of dollars to develop.To address these challenges, we developed the REBEL Sensor—an IoT-enabled technology that enables direct, real-time, and wireless monitoring of in-place concrete strength without the need for pre-determined calibration curves. By accurately predicting final strength at 28 or 56 days from the initial mix, our sensor empowers engineers to optimize curing schedules and validate new low-carbon mixes more efficiently. Importantly, our field data show that concrete strength often exceeds specified targets by 20–25%, revealing significant potential for cement reduction. By avoiding “over cementing,” the sensor directly supports carbon footprint reduction without compromising strength or durability. Furthermore, minimizing or eliminating destructive testing reduces material waste and associated emissions
Harnessing Waste Cellulose Fibers for Developing Highly Resilient and Durable Cementitious Composites
No full textThe construction industry continually seeks innovative materials to improve the performance and durability of cementitious composites. Waste cellulose fibers (WCF) derived from agricultural residues present an advanced underutilized source for reinforcing cementitious materials. These fibers exhibit exceptional properties, including high tensile strength and a remarkable water retention capacity (~10x their weight). Our research on WCF derived from wheat straw demonstrates their ability to mitigate autogenous shrinkage by up to 75% during early hydration and significantly improve mechanical properties at early ages. However, the long-term performance of WCF in cementitious matrices is affected by the harsh alkaline environment, which can cause hydrolysis and fiber disintegration. To overcome this challenge, an optimized carbonation curing process was developed, where WCF-reinforced cementitious mixtures are exposed to controlled conditions. This process enhances the formation of calcium carbonate preferentially at the fiber-matrix interface, improving fiber durability, adhesion, and reinforcing efficiency. The findings highlight the potential of WCF to develop highly resilient and durable cementitious composites, offering substantial performance improvements over conventional materials
Impact of Additive-Based Frost Protection on CO2, Cost, and Rheology on Cold-Weather Self-Consolidating Concrete
No full textCold weather concreting (CWC) generally refers to practices used to place concrete during cold weather. Traditionally, concrete placement in cold weather is accomplished by one or more precautions and procedures, such as pre-heating water and/or aggregates, insulating the concrete with protective blankets during curing, or heating the concrete or the surrounding concrete. However, these procedures can be energy-intensive, resulting in a shortened construction season in cold regions. Additive-based freeze protection (ABFP) is an alternative approach to casting and curing concrete at cold temperatures that reduces energy costs compared to traditional CWC techniques and potentially extends the construction season. Cold-weather self-consolidating concrete (CWSCC) is highly flowable without segregation and can be cast and cured at freezing temperatures, particularly at -5 °C. The adverse effects of freezing temperatures on the properties of CWSCC are mitigated by incorporating an ABFP system using an accelerator and a corrosion inhibitor. The ABFP system shall decrease the freezing point of CWSCC and hasten the hydration process. Three types of cementitious materials are considered: portland cement (PC) only, PC with granulated ground blast furnace slag, and PC with fly ash. Four building sizes and four heating sources are considered: diesel, electricity, propane, and natural gas. The average cost of CWSCC is 37% and 30% lower compared to vibrated concrete (VC) and conventionally heated self-consolidating concrete (SCC), respectively. The embodied CO2 in CWSCC is also lower than cold-weather vibrated concrete and SCC. The average CO2 in CWSCC is 3% and 8% lower compared to cold weather VC and SCC
