Toward Field-Ready UHPC for Underwater 3D Printing: Evaluating the Effect of Temperature on Rheological and Mechanical Behavior
Presented By: Masoud Pasbani
Affiliation: Louisiana State University
Description: Underwater 3D printing of ultra-high-performance concrete (UHPC) is one promising solution for rapid construction and repair of marine infrastructure. While all the studies have been reported on traditional printable concrete mixes under submerged environments, the application of UHPC in underwater 3D printing remains largely unexplored. Furthermore, the temperature-dependent rheological behavior of cementitious materials significantly influences their extrudability, printability, and buildability under submerged printing. This research investigates the influence of underwater low-temperature conditions—particularly between 4 to 20°C—on the printability of UHPC by analyzing the relationship between pre-printing rheological properties and printing performance. To evaluate the feasibility of in-situ marine mixing, both tap water and seawater are independently utilized as mixing water. Cubic samples are cast underwater for mechanical performance evaluation at each temperature. To simulate realistic field conditions, all printing operations are performed in seawater.
Impact of Bacterial Encapsulation Techniques on Autonomous Healing of Bioengineered Concrete
Presented By: Izhar Ahmad
Affiliation: Morgan State University
Description: Concrete is prone to cracking, reducing its service life. This study uses microbial-induced calcium carbonate precipitation for self-healing. Spores of Bacillus subtilis, Bacillus sphaericus, and Bacillus megaterium (10? cells/mL) were immobilized in alginate beads. Calcium lactate and yeast extract served as nutrients. Encapsulation was done via oven-drying, freeze-drying, and cement coating. Cracks were induced at 7 days using post-tensioned steel rods. Self-healing was evaluated by ultrasonic pulse velocity (UPV), compressive and flexural strength, strength restoration, and sorptivity. Oven-dried beads with B. megaterium showed up to 95% crack closure and 2.76× healing efficiency over control. While 3% beads slightly reduced compressive strength (3–8%), cement-coated beads improved compatibility. Nutrient addition caused minimal reduction (=1.23%). Strength restoration was highest with oven-dried beads. Ongoing sorptivity tests aim to confirm durability. The results highlight the potential of bacterial encapsulation for developing sustainable, self-healing concrete with reduced maintenance needs.
Chloride Binding and Desorption Mechanisms in Portland and Type 1L Cements Exposed to Carbonation and Chloride Attack
Presented By: Awetehagn Gebremariam
Affiliation: Colorado State University
Description: The U.S. cement industry is shifting from ASTM C150 to the more sustainable ASTM C595 Portland-limestone cement (Type 1L). While ordinary Portland cement (OPC) durability is well understood, adding limestone may alter concrete performance under combined carbonation and chloride exposure. This study investigates and compares the synergistic effect of combined carbonation and exposure to a salt solution on the chloride binding and desorption mechanisms of Type 1L and OPC systems. Cement paste specimens (w/c = 0.4) were cured for 28 days, then sliced into 310 discs (2 in. diameter x 3/16 in. thick), which were exposed to varying salt solutions (0.3 M, 0.7 M, 1 M, and 2 M) and carbonation regimens. Carbonation was performed at 23°C, 70% RH, and 10% CO2. The study evaluated pH, resistivity, phase changes, sorptivity, chloride binding, and desorption. Results show that Type 1L is more susceptible to chloride ingress and carbonation than OPC. This study provides in-depth insights into the durability performance of Type 1L cement, supporting its potential as a greener cement option.
Advancing Sustainable Pavements: Natural Fiber Reinforced Concrete with Glass Fiber Reinforced Polymer (GFRP) Dowels
Presented By: Saugat Dotel
Affiliation: Idaho State University
Description: The construction industry is shifting towards sustainable practices, with Natural Fiber Reinforced Concrete (NFRC) emerging as an eco-friendly alternative to conventional concrete. NFRC offers enhanced mechanical and thermal properties, but its use in pavements is limited due to insufficient research on performance and load transfer behavior. Traditionally, steel dowel bars are used to facilitate the load transfer mechanism between jointed slabs in concrete pavements, but their susceptibility to corrosion often compromises their effectiveness. Glass Fiber Reinforced Polymer (GFRP) bars offer a corrosion-resistant, sustainable alternative while maintaining structural integrity. This study explores the potential of GFRP as an alternative load transfer dowel to enhance joint performance in flax fibers-incorporated pavements. In the first phase, flax fibers partially replaced cement by weight, and fine aggregates by volume, at 0.5% and 1%. The replacement maintained comparable compressive strength and improved flexural strength by up to 8%.
Advancing Sustainable Concrete: A Review of Microbial Healing Efficiency, Testing Methods, and Deployment Limitations
Presented By: David Owolabi
Affiliation: Morgan State University
Description: Cracks in concrete compromise structural performance and longevity. This review examines microbial-induced calcium carbonate precipitation (MICP) as a self-healing strategy using bacteria such as Bacillus subtilis to autonomously seal cracks up to 1 mm wide. The role of fiber reinforcement including PVA, polypropylene, steel, and natural fibers is discussed for its influence on crack width control and microbial compatibility. While natural fibers retain moisture, they risk degradation over time; synthetic fibers offer durability and healing consistency. Key factors such as bacterial survivability, nutrient availability, and curing conditions are reviewed alongside challenges like cost and healing agent distribution. Performance evaluation methods include UPV, SEM, and mechanical recovery tests. This study identifies knowledge gaps and outlines strategies to optimize microbial–fiber synergy. Findings support the development of durable, low-maintenance, and resilient concrete systems that advance sustainability in modern infrastructure.
Rheological Behavior and Microstructural Investigation of Cellulose Nanofibers Modified Ultra-High-Performance Concrete
Presented By: Xiaoli Xiong
Affiliation: Purdue University - West Lafayette
Description: Cellulose nanofiber (CNF), derived from wood pulp, is a renewable nanomaterial with promising applications in cementitious materials. In this study, CNF was introduced UHPC as a nano-additive. An effective dispersion method through ultra-sonification was first developed to produce a well-dispersed CNF suspension in water, which was then added to the UHPC. The rheological behavior of fresh UHPC with CNF was examined, revealing a pronounced shear-thinning response. This behavior, characterized by high yield stress and reduced viscosity under shear, makes the CNF-modified UHPC particularly suitable for 3D printing. Furthermore, advanced characterization techniques—including isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy—were employed to investigate the effects of CNF on the hydration process of the blended cement binder and the microstructural development of UHPC. Results showed that CNF modified the hydration proecess and densified the UHPC matrix, leading to improved mechanical performance, as confirmed by compressive and flexural strength tests.
The Shear Friction Performance of Varying Surface Conditions in Grouted Precast Beam-Column Connections
Presented By: Allison Ebbert
Affiliation: North Carolina State University
Description: Precast concrete moment frames are commonly designed with beam-column connections. In this arrangement, beam-column joints are oriented in the vertical plane and transfer shear across the grouted interface through shear friction. The current shear friction design methodologies outlined in Chapter 22 of ACI 318-25 and ACI-PCI 319-25 do not clearly cover all of the grouted interface conditions commonly used in precast concrete applications. Critically, the use of indentions (shear keys) in a vertical interface is not covered, nor is use of indentions with intentional roughening. This research explores the shear friction performance of varying surface conditions in grouted precast beam-column connections. Tested surface conditions include monolithic, roughened, roughened and indented, and slip plane. Large 5 foot S-shaped specimens enabled direct loading of the connections in shear. The shear capacities of 12 specimens are presented and compared. In addition, digital image correlation (DIC) data is presented from selected specimens to show strains across the interface.
Early-Age Cracking in Concrete Bridge Decks: Correlation of Laboratory Data to Field Performance
Presented By: Collins Omindeh
Affiliation:
Description: Early age cracking in concrete bridge decks remains to be a significant challenge facing state DOTs all over the country. They contribute to premature deterioration of decks, reducing their overall service lives. Among the major factors associated with increased cracking risk include high cementitious contents often used on bridge deck mix designs. To minimize cracking, DOTs have been working to reduce the total cementitious contents and extend the durations of moist curing. While laboratory experiments have been conducted in an effort to investigate and minimize bridge deck cracking, there has not been a correlation between laboratory results and field performance of mix designs already in use. This study involves an experimental program to assess mix designs commonly used on bridge decks in Delaware. The main objective is to compare laboratory data to actual field cracking performance. The testing program involves conducting both restrained and unrestrained shrinkage tests to determine the shrinkage potential and cracking tendencies of concrete mixes. In addition, compressive strength, splitting tensile strength, and modulus of elasticity tests are conducted on concrete specimens to characterize their mechanical properties. The laboratory results will then be compared with observed field behavior, and a correlation will be determined. This will enable an understanding of how well the laboratory measured data correlates with actual cracking observed in the field. In addition, the study will identify an optimal mix design with the lowest shrinkage and cracking potential suitable for bridge decks in Delaware.
Application of Glass Fiber-Reinforced Concrete in Local Roadways: Assessing Mechanical Properties, Durability Performance, and Practicality
Presented By: Srinivas Allena
Affiliation: Cleveland State University
Description: Glass fiber-reinforced concrete (GFRC) improves mechanical and durability properties of concrete, yet its use in pavements remains limited due to insufficient research. This study investigates the potential of recycled glass fibers (RGF) from post-industrial sources as a sustainable alternative to virgin glass fibers (VGF) for use in local roadways. The objective was to assess whether RGF can enhance the flexural behavior of concrete to mimic asphalt-like performance while reducing material costs and promoting recycling. Concrete mixtures were designed with increased aggregate content and reduced cement, favoring supplementary cementitious materials. Glass fibers and polyolefin (PO) fibers were added by replacing fine aggregate by volume. Mechanical tests included compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity. Durability tests evaluated freeze–thaw resistance, drying shrinkage, and chloride ion penetrability. At 14 days, mixtures with VGF, RGF, and PO improved the modulus of rupture by 20.6%, 14.1%, and 29.8%, respectively. Chloride ion penetration was very low, with charges passed at 359, 166, 635, and 480 coulombs for control, VGF, RGF, and PO, respectively. Drying shrinkage in the control mixture was 433 µe, while VGF and RGF reduced it to 347 µe and 376 µe. PO exhibited the greatest shrinkage at 617 µe. Scanning electron microscopy imaging was used to characterize fiber morphology. The findings suggest that RGF offers a cost-effective, environmentally friendly alternative to VGF, with promising implications for sustainable pavement-grade concrete applications.
A Novel Ternary Blend: Enhancing Hydration and Strength with Biochar and Calcined Clay
Presented By: Adriana de los Angeles Alvarado Ramirez
Affiliation: Louisiana State University
Description: "The use of calcined clays as Supplementary Cementitious Materials (SCMs) is expanding due to their global availability and their potential to enhance durability while lowering the carbon footprint of concrete. This in-progress research investigates the synergistic potential of a novel ternary blend combining pre-soaked biochar and calcined clay in cement mortars. The study evaluates several mixtures against a plain cement control mortar: binary blends with 20% and 30% biochar replacement (B20, B30) and ternary blends combining 30% calcined clay with 20% or 30% biochar (C30-B20, C30-B30). These combinations result in total cement replacement levels of up to 60%.
Early results show that the C30-B20 ternary blend mortar exhibits a significantly higher compressive strength (56.2 MPa) compared to both the control (45 MPa) and the biochar-only mixtures. This performance enhancement is hypothesized to be attributed to a dual mechanism: improved hydration via internal curing from the water-releasing biochar and boosted pozzolanic activity from both the calcined clay and amorphous silica in the biochar. Ongoing microstructural characterization and thermogravimetric analysis are being performed to validate these mechanisms. "
Tailoring Ultra-High Performance Seawater Concrete: Property Optimization and Additive Manufacturing
Presented By: Muhammad Mustafa
Affiliation: University of Massachusetts Lowell
Description: Seawater concrete offers a promising solution by alleviating pressure on dwindling freshwater resources, particularly in regions facing acute water scarcity. However, developing ultra-high-performance seawater concrete (UHPSC) and tailoring it into a suitable material for additive manufacturing introduces significant challenges and requires a delicate balance between workability, printability, and mechanical performance to meet the stringent demands of structural applications. This study explores the design and performance optimization of UHPSC mixtures tailored for additive manufacturing, focusing on hydration kinetics, phase evolution, and evolution of rheological and setting properties critical for printing. Key fresh-state properties, including flowability, extrudability, water retention, shape retention, and setting time, were evaluated to assess material printability. In addition, buildability and deformation during the printing process were investigated to determine the feasibility of using this new concrete material in layer-by-layer construction. The optimized UHPSC demonstrated robust buildability, successfully achieving up to 146 printed layers in continuous printing. Post-printing evaluations, including interfacial bonding, mechanical strength, and permeability, were also conducted to provide comprehensive insights into the performance of printed UHPSC. The findings underscore the potential of UHPSC as a viable ink material for sustainable, resource-efficient, and structurally sound additive construction.
An End-to-End Automated Framework for Smartphone-Based Digital Image Correlation in Contactless Concrete Property and Fracture Analysis
Presented By: Tohid Asheghimehmandari
Affiliation: Morgan State University
Description: "Accurate measurement of deformation in concrete elements is essential for understanding their behavior and fracture mechanisms under various loading conditions. Traditional tools such as strain gauges and LVDTs are limited to localized data acquisition and often interfere with specimen integrity. In contrast, Digital Image Correlation (DIC) provides full-field, high-resolution strain mapping without physical contact, making it particularly effective for capturing cracking and deformation in concrete. Despite these advantages, video-based DIC remains underutilized in concrete research due to fragmented preprocessing workflows, limited automation, and the complexity of existing software tools and setup procedures.
To address these limitations, this study introduces a novel, end-to-end automated framework—the DIC Frame Extractor—specifically developed for smartphone-recorded videos.
The Python-based system is fully compatible with cloud platforms and offers a lightweight, low-cost solution designed for researchers using minimal equipment. Unlike prior approaches that require manual intervention or specialized hardware, the DIC Frame Extractor integrates preprocessing and tracking within a unified, automated workflow optimized for smartphone video input.
It performs precise tracking of speckle movement to extract key parameters—including deflection and strain distribution—while also providing clear visualizations of crack initiation, propagation, and fracture mode evolution through high-resolution outputs.
This innovation significantly simplifies and standardizes the input preparation process for DIC, lowering technical barriers and accelerating the experimental workflow. By enabling accurate, contactless deformation analysis using only smartphone footage, this framework represents a major step toward expanding the accessibility, reproducibility, and practicality of DIC in experimental concrete research and education."
Printing Meets Precast: 3D-Printed Ductile Concrete Covers for Durable Bridge Girder Ends
Presented By: Pranay Singh
Affiliation: SUNY University of Buffalo
Description: Prestressed bridge girders with thinner and deeper webs are vulnerable to cracking in their end zones at prestress release. These cracks primarily result from the limited tensile strain capacity of conventional concrete and the concentration of high prestressing forces over short transfer lengths. Such cracking raises significant durability concerns by enabling the ingress of chlorides and moisture, which can accelerate reinforcement corrosion. Traditional mitigation strategies that rely on additional reinforcement detailing at the end zones have proven insufficient on their own, prompting the need for alternative solutions. This study proposes a novel, integrated approach that combines performance-based material tailoring with advanced fabrication techniques to develop a 3D-printed ductile concrete cover for the girder end zones. The cover is designed to promote distributed micro-cracking rather than localized macro-cracks, thereby enhancing durability by limiting surface crack widths. A performance-based framework was established to define the required fresh and hardened-state properties of the material. The development followed an iterative process, beginning with a non-printable ductile concrete mix, eventually optimized for 3D printing. Proof-of-concept trials included testing reinforced concrete beams with 3D-printed ductile covers applied at the mid-span to validate mechanical performance. Ongoing studies include bond strength and durability testing of the composite system comprising of conventional concrete core with 3D printed ductile concrete covers. The study also outlines a methodology for integrating these 3D-printed concrete covers into the existing precast workflow, paving the way for more durable and resilient bridge infrastructure.
An Implementable Machine Learning-Based Evaluation Tool for Cracked Prestressed Concrete Bridges
Presented By: mohamed hassan lasheen
Affiliation: SUNY University of Buffalo
Description: Bridge owners face difficult decisions on whether a bridge should be posted, repaired or replaced when prestressed concrete members have shear cracks due to overloading. The decisions are currently made based on costly load-testing or time consuming modeling. This presentation focuses on a new method that utilizes machine learning algorithms to relate crack widths with beam condition indicators such as shear load and stiffness. Machine learning algorithms are trained using shear test data of prestressed concrete beams from the literature with crack widths documented. Material and geometric properties in addition to crack widths are used as input for a Gaussian Process Regression algorithm to predict shear capacity, load and stiffness. The results show that machine learning can provide a rapid and reasonable predictions of shear load and the accuracy of the predictions depend on the size and quality of the available training data.
Feasibility of Using Calcined Clays as Precursors in One-Part Alkali-Activated Materials
Presented By: Chaitanya Nath
Affiliation: Clarkson University
Description: Alkali-activated materials (AAMs) offer a promising low-carbon alternative to ordinary portland cement by eliminating the need for energy-intensive clinker production. However, the practical application of traditional two-part AAMs is limited due to the handling and storage challenges associated with corrosive alkaline solutions. This study focuses on the development of one-part alkali-activated binders, “just-add-water” systems, using solid sodium metasilicate as the activator to enhance field applicability. Three calcined clays with distinct physicochemical properties were used as the primary aluminosilicate precursors. To reduce the high activator demand associated with calcined clays, ground granulated blast furnace slag (GGBFS) was incorporated as a calcium source and reactivity enhancer. The optimized formulations resulted in producing compressive strength up to 4500 psi while exhibiting lower cumulative heat release compared to conventional cements. Additionally, the use of nanomaterials to enhance the strength and reactivity is also explored. A comprehensive assessment, including compressive strength, rheology, and hydration behavior guided the optimization of precursor-activator synergy. This work underscores the viability of calcined clays as precursors in making alkali-activated cement, paving the way for practical, scalable, and climate-resilient construction materials with a significantly reduced carbon footprint.
Modeling Crack Evolution in Concrete Due to the Oxidation of Sulfide-Bearing Aggregates
Presented By: Osamah Dehwah
Affiliation: Johns Hopkins University
Description: "Damage in concrete containing sulfide-bearing aggregates has become a critical issue in the northeastern United States, particularly in Connecticut and Massachusetts. This deterioration, driven by pyrrhotite oxidation, has prompted extensive research aimed at understanding the underlying chemical and mechanical mechanisms. To date, approximately five thousand homes in Connecticut have been confirmed to suffer from pyrrhotite-induced damage, and the number continues to rise.
Pyrrhotite oxidation is a gradual process that unfolds over decades, leading to progressive cracking and a marked reduction in concrete stiffness. To investigate the formation and propagation of cracks due to this oxidation, a quasi-static two-dimensional finite element model was developed to simulate crack network evolution in cement-based materials. While inherently limited in capturing three-dimensional behavior, the two-dimensional model offers valuable insights into the influence of microstructural characteristics on crack growth and the role of internal expansion in the degradation of concrete’s elastic properties i.e., Young’s modulus, bulk modulus, and shear modulus. Furthermore, a sensitivity analysis was conducted to enhance model precision and computational efficiency, focusing on mesh resolution and convergence criteria. The developed model serves as a practical tool for understanding damage mechanisms associated with internal phase expansion and provides a foundation for future efforts aimed at mitigating deterioration in affected structures."
Freeze–Thaw Effects on Phase Change Materials-Incorporated Cementitious Mortars: Meso-Structural and Mechanical Evolution
Presented By: Nausad Miyan
Affiliation: University of Rhode Island
Description: This study investigates the effects of microencapsulated phase change materials (MPCMs) on the mechanical performance and meso-structural degradation of cementitious mortars subjected to extended freeze–thaw cycling. Thermal behavior was characterized using Differential Scanning Calorimetry (DSC), while mechanical properties and internal damage were evaluated through strength testing and high-resolution X-ray tomography (XRT), respectively. The DSC analysis confirmed the thermal buffering capacity of MPCMs, contributing to improved freeze–thaw resistance. Despite a reduction in initial compressive strength, MPCM-modified mortars exhibited markedly lower strength loss and less internal damage after extended cycling, compared to control specimens. XRT imaging revealed diminished meso-structural cracking in MPCM-enhanced mortars, particularly at higher MPCM dosages. These findings demonstrate that MPCM incorporation can significantly improve the freeze–thaw durability of cementitious systems, offering a promising pathway for developing thermally adaptive and resilient construction materials.
Role of Biochar on the Durability Performance of Cementitious Composites
Presented By: Dhrubajouti Karmakar
Affiliation: University of Texas Arlington
Description: The use of biochar has emerged as a promising pathway to achieve carbon neutrality of cementitious composites. However, its effects on the durability of cementitious composites are not well explored. To address this knowledge gap, this study investigates the alkali silica reaction (ASR) and leaching behavior of cementitious composites containing ground and functionalized biochar as a partial replacement of cement. Raw biochar was chemo-mechanically modified using biomimicking molecules to produce the functionalized biochar. Ordinary Portland cement (OPC) was then partially replaced by 20% and 30% by weight dosages using ground or functionalized biochar. Cement hydration kinetics and microstructural properties were assessed with paste samples, while mortar samples were used to evaluate the mechanical performance and length expansion due to ASR. Additionally, alkali ion adsorption by functionalized biochar and its effects on the pore solution were monitored. The results showed that ground biochar increased ASR vulnerability, evidenced by higher expansion. However, functionalized biochar significantly improves the ASR resistance, reducing expansion upto 74% compared to the control (without biochar). Furthermore, these composites successfully met the Strength Activity Index requirements for SCMs, achieving compressive strength upto 102% of control. This superior performance of the functionalized biochar can be attributed to the biomimicking molecules’ ability to densify the matrix and enhance binder-biochar adhesion. Consequently, this system improves the durability and mechanical performance of cementitious materials. On top of that, Life Cycle Assessment (LCA) showed that this system can reduce Global Warming Potential (GWP) upto 103% compared to OPC, highlighting its environmental benefits as well.
Behavior of Concrete Under Combined Cyclical and Environmental Stressors
Presented By: Joshan Gajurel
Affiliation: Youngstown State University
Description: The deterioration mechanisms of concrete under combined environmental stressors alkali-silica reaction (ASR), freeze-thaw (F/T), and wet-dry (W/D) conditions were investigated. While each of these is well researched individually, there is limited knowledge regarding interactions between the mechanisms and their impact on microstructure, transport properties, and concrete performance. Concrete prisms were exposed to combinations of ASR, F/T, and W/D for 15 months, with regular determination of expansion, microstructural changes, and transport properties. Compared with baseline conditions of individual ASR, F/T or W/D, the combined conditions (ASR + F/T, ASR + W/D, F/T + W/D) indicate a strong synergistic interaction with greater deterioration than expected from the baseline conditions alone. These findings will enhance our understanding of deterioration mechanism interactions in real-world conditions and allow for more reliable predictive models of concrete durability.
Dissolution Kinetics and Phase Evolution of Pseudowollastonite-Rich Slag for use in Low-Carbon Concrete
Presented By: Kimmie Cerna
Affiliation: University of Virginia
Description: Understanding the early-stage dissolution behavior of alternative cementitious materials is essential to improving its performance. This study focuses on phosphorus slag rich in pseudowollastonite, a monocalcium silicate that has been shown to form both crystalline calcium silicate hydrates (CCSH) and carbonates in CO2-rich environments. Ground slag was reacted in deionized water with either NaOH to adjust pH or Na2CO‚ÇÉ to introduce carbonation. Reactions proceeded for up to 3 days under continuous mixing, with supernatants analyzed by ICP-OES and solid residues with XRD, TGA, Raman, and FTIR. Under NaOH activation, pseudowollastonite and calcite initially present in the slag start to dissolve, and amorphous CSH forms by 3 days. In contrast, Na2CO3 carbonation promotes the formation of Ca(OH)2 and amorphous CSH within 1 day, followed by further CSH crystallization by day 3. These findings suggest that unlike NaOH activation, Na2CO3 carbonation alters the dissolution-precipitation pathway of pseudowollastonite, possibly accelerating CCSH formation.