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We study the diffusion of chloride ions in hardened cement paste (HCP) under steady-state conditions and accounting for the highly heterogenous nature of the material. The HCP microstructures are obtained through segmentation of X-ray images of real
Qinang Hu, Mohammed Aboustait, Taehwan Kim, Tyler Ley, Jeffrey W. Bullard, Jay C. Hanan, Volker Rose, Robert Winarski
The reasons for the start and end of the induction period remain a mystery in cement hydration. One long-standing hypothesis is the importance of early hydration products on the surface of cement particles. However, because this material is not widely
Qinang Hu, Mohammed Aboustait, Taehwan Kim, Tyler Ley, Jay C. Hanan, Jeffrey W. Bullard, Robert Winarski, Volker Rose
While portland cement has been widely studied for over 100 years, there are still widespread disagreements on the mechanisms of hydration. One reason for this is that direct observation of the change in microstructure and chemistry are challenging for many
The Reclamation-NIST Exploratory Research Symposium was held on August 4-5, 2015, at the Reclamation Denver Federal Center facility in Lakewood, CO, and the NIST facility in Boulder, CO. Staff from the Bureau of Reclamation and the National Institute of
The equilibrium phase assemblages that have been predicted in previous studies for the Ca-Al-S-O-H system at 25 C are revisited by calculating boundaries between equilibrium solubility surfaces among gibbsite, hydrogarnet, portlandite, calcium
The importance of particle shape in affecting the behaviour of powders and other particulate systems has long been recognised, but until fairly recently particle shape information has been rather difficult to obtain and use compared to its more well-known
Previous research has demonstrated a linear relationship between compressive strength (mortar cubes and concrete cylinders) and cumulative heat release normalized per unit volume of (mixing) water for a wide variety of cement-based mixtures at ages of 1 d
Tandre Oey, Aditya Kumar, Gabriel Falzone, Jian Huang, Sierra Kennison, Mathieu Bauchy, Narayanan Neithalath, Jeffrey W. Bullard, Gaurav Sant
Tricalcium silicate stops hydrating at relative humidities (RH) less than 80 %. But the rate at which its hydration rate decreases as a function of the RH has not yet been elucidated. By invoking correspondence between RH and water activity (aH, unitless)
Igor de la Varga, Jose Munoz, Dale P. Bentz, Benjamin Graybeal
Prefabricated Bridge Element and System (PBES) construction commonly relies on field-cast grout-type materials to complete the connections between precast concrete elements. The interface bond between the grout and the substrate concrete can be a key
Alejandro Duran-Herrera, Joana K. Campos-Dimas, P Valdez, Dale P. Bentz
In this study, a copolymer composed of hollow spherical particles with an average particle size of 90 µm was evaluated as a lightweight aggregate in Portland cement-fly ash mortars to improve the thermal conductivity (k) of the composite. Mortars were
Emilio Hernandez-Bautista, Dale P. Bentz, Sadoth Sandoval-Torres, Prisciiano Cano Barrita
The mass and heat transport during steam curing of concrete has a bearing on both the mechanical and durability properties. Therefore, it is essential to take into account the temperature evolution and the moisture distribution to prevent premature damage
Pan Feng, Edward Garboczi, Pan Feng, Jeffrey W. Bullard
A microstructure model has been applied to simulate near-surface degradation of portland cement paste in contact with a sodium sulfate solution. This new model uses thermodynamic equilibrium calculations to guide both compositional and microstructure
Yaghoob Farnam, Sarah Dick, Andrew Wiese, Jeffrey M. Davis, Dale P. Bentz, Jason Weiss
The conventional CaCl2-H2O phase diagram is often used to describe how a calcium chloride behaves when it is used on a concrete pavement undergoing freezing and thawing damage. However, the existence of additional chemical compounds in concrete can alter
Chiara Villani, Catherine Lucero, Dale P. Bentz, Daniel S. Hussey, David L. Jacobson, Jason Weiss
Shrinkage Reducing Admixtures (SRAs) are increasingly being used in concrete as a method to minimize shrinkage and restrained shrinkage cracking. SRAs reduce shrinkage by decreasing the surface tension of the pore solution; however, SRAs also impact the
Catherine Lucero, Dale P. Bentz, Daniel S. Hussey, David L. Jacobson, Jason Weiss
Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and
Myoungsung Choi, Chiara C. Ferraris, Nicos Martys, Didier Lootens, Van Bui, Trey Hamilton
With the increasing use of pumping to place concrete, the development and refinement of the industry practice to ensure successful concrete pumping is becoming an important need for the concrete construction industry. To date, research on concrete pumping
Yaghoob Farnam, Andrew Wiese, Dale P. Bentz, Jeffrey M. Davis, Jason Weiss
MgCl2 is used in deicing applications due to its capability to depress freezing temperatures to a lower point than other salts like NaCl. The constituents of concrete (i.e., pores solution, calcium hydroxide, aluminate phases, and calcium silicate hydrate
Yaghoob Farnam, Hadi S. Esmaeeli, Dale P. Bentz, Pablo Zavattieri, Jason Weiss
In North America, some concrete pavements and sidewalks have shown severe damage during freezing. Research has been performed to better understand the cause of damage. A test method (called longitudinal guarded comparative calorimeter (LGCC)) has been
Yaghoob Farnam, M R. Geiker, Dale P. Bentz, Jason Weiss
Different constituents of concrete can have cracking behavior that varies in terms of the acoustic waveform that is generated. Understanding the waveform may provide insight into the source and behavior of a crack that occurs in a cementitious composite
William Ha, Dale P. Bentz, Wyatt Kahler, Laurence Walsh
Introduction: The setting times of commercial mineral trioxide aggregate (MTA) and Portland cements vary. It was hypothesized that much of this variation was due to differences in particle size distribution. Methods: Two gram samples from 11 MTA-type
Ana Trapote-Barreira, Lionel Porcar, Jordi Cama, J. M. Soler, Andrew J. Allen
Flow-through experiments were conducted to study the calcium-silicate-hydrate (C-S-H) gel dissolution kinetics under a CO2-free atmosphere at room temperature (22 ± 2) ºC in the pH range from 10 to 13 relevant to cement media. During C-S-H gel dissolution
Li xiodan, Zachary Grasley, Jeffrey W. Bullard, Edward Garboczi
A computational model has been developed that combines finite element methods with microstructure development simulations to quantitatively predict the viscoelastic/viscoplastic relaxation of cement paste due to intrinsic calcium silicate hydrate
Xiaodan Li, Zachary Grasley, Edward Garboczi, Jeffrey W. Bullard
Finite element procedures combined with microstructure development modeling are integrated to quantitatively predict the viscoelastic/viscoplastic relaxation of cement paste due to intrinsic calcium silicate hydrate viscoelasticity and microstructure
Julyan Stoian, Tandre Oey, Jeffrey W. Bullard, Jian Huang, Aditya Kumar, Magdalena Balonis, Judith E. Terrill, Narayanan Neithalath, Gaurav Sant
Ordinary Portland cement (OPC) prehydrates during storage or handling in moist environments, forming hydration products on or near its particles' surfaces. Prehydration is known to reduce OPC reactivity, but the extent of prehydration has not yet been
Julyan Stoian, Tandre Oey, Jeffrey W. Bullard, Jian Huang, Aditya Kumar, Magdalena Balonis, Narayanan Neithalath, Gaurav Sant
Ordinary portland cement (OPC) prehydrates during storage or handling in moist environments, forming hydration products on or near its particles' surfaces. Prehydration is known to reduce OPC reactivity, but the extent of prehydration has not yet been