Modeling of Entrained Air Dissolution and Long-Term Saturation: Role of Microstructure in Emerging Cementitious Materials
Presented By: Aiqing Xu
Affiliation:
Description: Freeze-thaw deterioration in air-entrained cementitious materials is primarily driven by external moisture ingress and the progressive saturation of pore networks. The resistance of cement-based materials to freeze-thaw damage is strongly influenced by the dissolution of trapped air and water transport within the pore structure. This study extends the single void dissolution kinetics (SVDK) model to simulate long-term saturation behavior across various cementitious systems, including OPC, CSA, LC3, and geopolymers. By incorporating system-specific physical characteristics, the model captures the dissolution behavior of trapped air and water transport in saturated matrices. The influence of physical and geometrical properties on the kinetics of gas dissolution and water diffusion is systematically explored. The results highlight the critical role of microstructural differences in governing gas transport and saturation evolution. This work advances the theoretical understanding of freeze-thaw damage mechanisms and supports the development of more durable cementitious materials.
Can Reactivity Tests Predict Later-Age Compressive Strength in High-Volume SCM Systems?
Presented By: Rahul Mohan
Affiliation: Clarkson University
Description: Reactivity tests (e.g., R3, modified R3) are gaining in popularity as screening tools for supplementary cementitious materials (SCM). These tests are relatively simple and provide results quickly. However, it is not clear if the information provided by these tests (heat release, bound water, calcium hydroxide consumption) corresponds to practical results (i.e., compressive strength), especially for high-volume pozzolanic systems that react slowly. This study uses machine learning (ML) to quickly and accurately estimate early and later-age compressive strength of ternary blended cements and SCM using results from the modified R3 test. Nine ML models were evaluated. The Extra Trees algorithm achieved the highest accuracy (R2= = 0.93) while mitigating overfitting. Bound water showed the strongest correlation with strength. In contrast, heat release is a relatively poor predictor, especially for alumina-rich SCM. This approach offers a practical, scalable pathway to reduce testing burdens and accelerate low-carbon concrete mixture design.
Experimental Investigation of Post-Fire Performance of Concrete Bridges
Presented By: Shubham Sharma Gyawali
Affiliation: The University of Alabama
Description: Fire-induced damage to bridge infrastructure has been a recurring concern, often leading to substantial economic losses and service disruptions. To support informed repair-versus-replacement decisions following such events, an experimental study was conducted to evaluate the post-fire structural performance of concrete bridge decks. A total of seven concrete deck specimens (7 ft 9 in. x 2 ft), with two thicknesses (6 in., 7 in.) were fabricated and subjected to simulated fire loading using ceramic heaters. The study investigated the influence of surface temperature and deck thickness on fire-induced damage. A suite of non-destructive tests was employed before and after fire exposure to detect damage characteristics. Subsequently, destructive flexural load tests were performed to determine the residual load-carrying capacity of each specimen. This presentation will discuss observations and findings from this experimental study. The findings provide critical insights into the structural integrity of fire-damaged concrete decks and offer guidance for post-fire assessment.
Enhancing Kinetics and Strength via Nano-Sized Ettringite Seeds
Presented By: Faisal Qadri
Affiliation: University of Illinois, Urbana Ch
Description: Nano-sized seeds are emerging as a new class of commercially available chemical admixtures that serve as nucleation sites for additional hydration products. Different seeds have been used to enhance hydration such as C-S-H seeds. In this talk, we will share the latest update on synthesizing superfine AFt seeds using one-step co-precipitation method, producing well-dispersed AFt nano-seeds (D50 = 68 nm). Adding 0.5 wt% seeds into Type IL cement paste and mortar accelerates the main hydration peak by 3.6 h and increases the cumulative heat by 20% to 295 J.g-1, causing the compressive strength at day 3 to outperform the control mixtures at day 14. 27Al NMR confirms faster AFt formation and earlier monosulfoaluminate appearance. These seeds have the potential to encourage agencies and contractors using alternative cementitious materials and compensate for the accompanied strength reduction, consequently, reducing the CO2 footprint of the cement production.
Torsional Behavior of Hollow Precast Concrete Bent Caps Using Laser-Based Measurement Techniques
Presented By: Eleanor Garrett
Affiliation: Texas A&M University College Station
Description: Design of precast/prestressed concrete cap beams relies on understanding both the demands and structural response when subject to torque. Torque can be unintentionally induced by different bearing seat elevations between abutments. These demands lead to diagonal cracking and may affect the load-carrying capacity. Current routines rely on manual bridge inspection readings, which are time consuming and lack the precision needed to capture torsional effects in the form of angle of twist measurements. This research investigates torsional behavior of hollow precast/prestressed sections through high-resolution laser scanning. Laser-based scanning approaches enable detection of bearing pad misalignment, structural cracking, and improve the quantification of in-situ torsional demands. Field and laboratory testing demonstrated that these techniques offer a practical path forward. Results support integrating laser-based measurements in construction and design phases, which can reduce inspection uncertainty and extend service life and safety of hollow precast/prestressed sections.
Mitigating plastic shrinkage of 3D printed concrete using Super Absorbent Polymers
Presented By: Micah Stark
Affiliation: Texas A&M University College Station
Description: 3D printed concrete is highly prone to plastic shrinkage. In a previous ACI Research-in-Progress session, Super Absorbent Polymers (SAP) were shown to reduce plastic shrinkage in analog 3D printed concrete filaments. This was attributed to SAP’s potential to retain water and slow evaporation; however, mass loss was not measured. The present study investigates the mechanisms behind SAP-induced shrinkage reduction by simultaneously tracking specimen mass and shrinkage strains. This work extends prior research by measuring deformation along both vertical and horizontal surfaces, enabling analysis of vertical, lateral, and longitudinal strain for approximation of total volumetric strain alongside mass loss. Results show that SAP additive specimens with increased water content experienced greater mass loss yet reduced volumetric shrinkage by up to 40%. This suggests that mechanisms beyond simple water retention, such as delayed capillary pressure development or pore structure alteration, may be contributing to the observed shrinkage mitigation.
Integrated Mechanical-Thermal Activation for High-Performance Supplementary Cementitious Material Synthesis
Presented By: Oluwadamilare Adesina
Affiliation: Arizona State University
Description: Emerging aluminosilicates from unconventional sources offer promising potential as supplementary cementitious materials, yet their activation typically requires energy-intensive thermal processing. This study explores a hybrid mechanochemical-thermal activation route that combines high-energy milling with subsequent low-temperature calcination, to enhance the reactivity of pure kaolinite and montmorillonite, using KGa-2 and SWy-3 as model clay minerals. Structural transformation in the mechanically activated materials - including induced amorphization and crystallographic disorder - are characterized via FTIR, XRD, and NMR, giving insights into maximizing reactivity through further tailored treatments. For the first time, isoconversional kinetic analysis reveals significantly reduced activation energy and modified dehydroxylation pathway compared to the untreated samples, enabling more efficient calcination protocols. Ongoing work examines the pozzolanic reactivity and hydration behavior of the mechanothermally activated products, investigating their viability for high clinker replacement levels (>30%). The hybrid strategy not only lowers thermal demand but also supports carbon-neutral and electrified pathways for sustainable cement production.
Lap Splices of Longitudinal Bars under Pure Torsion
Presented By: Sung-Chul Chun
Affiliation: Incheon National University
Description: Development length provisions are primarily based on splice specimens simulating flexural members. Longitudinal bars in torsion-dominant members also experience tension and require splicing. This study experimentally evaluates lap splice performance under pure torsion to assess the adequacy of splice lengths specified in ACI 318-25. For the test setup used the central region was subjected to pure torsion, and longitudinal bars were spliced within this region. Eleven specimens were tested with variables including splice length and transverse reinforcement spacing. Test results show that splice strength was only about two-thirds of ACI 408 predictions. Unlike flexural cracks in flexure-dominant members, diagonal cracks from torsion may cause early spalling of cover concrete, reducing splice performance. An additional seven specimens will be tested in August. The ongoing evaluation of lap splice behavior under torsion will be presented in the Research in Progress session.