publications: research briefs

Concrete Science Platform

Life Cycle Assessment Platform

Research Profile Letter – April 2013

Clinker Grindability: Microstructure Matters

This multi-scale investigation of fracture properties with the microscratch test highlights the importance of microstructure in clinker grindability. This original approach also provides a means for investigating the effects of microstructural characteristics (e.g. crystal size, porosity, belite clustering) on the grindability of clinkers. more >>

Research Profile Letter – March 2013

Predicting C-S-H aging

This is the first time that rigidity theory has been applied to such a complex material. Importing glass science tools to C-S-H brings new ideas to predict the effect of composition on cement aging. The use of the predicted optimal compositions of cement could lead to more durable concrete. More generally, this highlights the fact that increasing the amount of silica in cement is another means for producing green sustainable concrete. more >>

Research Profile Letter – February 2013

Nucleation Seeding of Alkali Activated Paste

This study examines the rate controlling step that leads to a better understanding of how to use supplementary cementitious materials such as slag and fly ash to produce more sustainable mixes. more >>

Research Profile Letter – January 2013

Properties of Polymorphs of Belite

This research provides new information about polymorphs of belite obtained by atomic scale modeling. Results of impurity defects, which vary reactivity for γ-C2S and β-C2S polymorph, can be used to control reactivity of belite. Information on surface energetics of polymorphs with impurities can shed also light on grinding processes. more >>

Research Profile Letter – December 2012

Mesoscale Modeling of Sorption Hysteresis

The model quantitatively predicts sorption hysteresis in hardened cement paste. By answering the basic question, “Where is the water?” it paves the way for bottom-up descriptions of diverse phenomena, such as shrinkage, creep and corrosion. The model can also be used to predict sorption/desorption isotherms and infer microstructural information. more >>

Research Profile Letter – November 2012

When fracture stems from the atoms

We propose a new approach to study fracture properties by molecular simulation valid for both brittle and ductile materials. This research highlights the possibility to understand and engineer the fracture resistance starting from the smallest scale. For instance, it suggests that a binder-mineral interface with high ductility and a significant stiffness contrast may improve significantly the fracture resistance of concrete. more >>

Research Profile Letter – October 2012

Energy Management: City Texture Matters

The novel approach leverages Statistical Physics to describe the complexity of cities in terms of molecular structures. This provides city planners and developers with innovative texture information, which can be used for effective energy management, including heating, ventilation and air conditioning of buildings in the scale of neighborhood and cities. more >>

Research Profile Letter – August 2012

Induction Period in Alite Hydration

This research provides new information about the mechanisms that control the decrease in reactivity of alite during the induction period. This information can only be obtained by detailed atomic scale modeling, which provides an important piece of a complex puzzle, and brings us closer to a complete mechanistic description of the hydration process. more >>

Research Profile Letter – July 2012

C-S-H Texture From Sorption Isotherms

This unique bottom-up approach developed by the CSHub combines information from atomistic and colloidal simulations with the coarse-grained lattice-gas model allowing validation of the cement model structure at a larger length scale. This facilitates the first composite model of C-S-H at mesoscale, guiding the development of cement microstructures with desired mechanical properties. more >>

Research Profile Letter – June 2012

Validating Effects of Cement Paste Composition on Mechanics

We validate the computational prediction that Ca/Si ~ 1 creates significantly stiffer and harder C-S-H than in OPC pastes, with direct consequences for concrete performance and environmental footprint. This work shows that this Ca/Si is accessible in current, commercially available processing routes and products. more >>

Research Profile Letter – May 2012

Visualizing Hydration Products

These experiments provide direct access to the kinetics associated with hydration mechanisms. Different parameters such as initial clinker composition and initial concentrations of calcium, silica or H+ ions (pH) within the solution can be compared quantitatively to models under development for clinker dissolution and cement setting. more >>

Research Profile Letter – April 2012

Crystallinity of Cement Clinkers: Application of Rietveld Refinement

Using the Rietveld method, we provide evidence that the presence of non-quantified material is significant in the studied samples of industrial clinker. This material likely affects grindability and reactivity, and our strategy allows one to quantify systematically its content, which has the potential to permit more complete characterization and therefore better estimates of performance and grindability. more >>

Research Profile Letter – March 2012

Aluminum and Sulfate Doped Belite

This research highlights the critical role of aluminum and sulfate doping on the reactivity of belite and indicates that by considering relatively simple chemical techniques, the dissolution and precipitation rates of belite can be significantly increased. more >>

Research Profile Letter – February 2012

Gaining strength by splitting water

Besides giving a more refined description of the C‑S‑H gel atomic structure, we have demonstrated that water speciation has a great effect on the strength properties of C‑S‑H nanoparticles. It is important to note that controlling the speciation of water within the C-S-H model through the Ca/Si ratio and temperature, provides a new degree of freedom from which one can master/improve the strength of the solid C‑S‑H phase. more >>

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Research Profile Letter – January 2012

Locking radionuclides in cement

We propose a new approach to investigate environmental and safety issues for the use of cement as a candidate for immobilizing radioactive waste such as strontium. It is based on first-principle statistical physics and allows a quantitative assessment of the impact of locking radionuclides on cement hydrate stability and mechanical properties. more >>

Research Profile Letter – December 2011

Holding It Together: C-S-H Cohesion

Our approach shows that cohesion within cement paste decreases with decreasing water content, specifically at RH<20% and 27°C. This loss of cohesion within the binding phase significantly affects the strength and durability of the material. These calculations help to explain reduced strength and creep resistance of concrete in very dry environments, and also provide insight toward damage mechanisms in concrete at high temperatures (e.g., fire environments) even before heat-induced polymerization of silica chains.
more >>

Research Profile Letter – November 2011

Predicting Setting Times Bottom-Up

This model of setting couples hydration kinetics and development of mechanical properties, a combination that allows the prediction of setting times in a bottom-up fashion. Our setting model brings information from atomistic and colloidal simulations to larger length and time scales, suggesting opportunities to link atomic structures of hydration products with engineering properties. more >>

Research Profile Letter – October 2011

Why Wet C-S-H is Weak

These results provide new understanding of how C-S-H structure and properties vary with water content. The proposed mechanisms governing increased stiffness and strength of C-S-H with low water content, particularly the humidity-dependent silica connectivity and resistance to shear deformation, can now be validated experimentally. more >>

Research Profile Letter – September 2011

When Concrete Takes (part of) the Heat

This research highlights the impact of chemical modifications, namely the calcium-to-silicon ratio, on specific heat capacity of C-S-H. It also highlights the power of the bottom-up approach being developed at MIT. Specifically, the derived functional relations between thermal properties and molecular structures provide a molecular baseline for nanoengineering the thermal performance of cement-based materials that will eventually contribute to increasing the energy efficiency of buildings. more >>

Research Profile Letter – July 2011

ReaxFF Hydration of Clinker Surfaces

This research highlights that the difference in reactivity of alite and belite is inherent to their crystalline structure. This means, from a dissolution kinetics perspective, that a shift from an alite to belite dominated system can be achieved by crystal modifications and surface engineering. The insight thus gained with ReaxFF can enable R&D of clinker phases with higher reaction rates and early strength development. more >>

Research Profile Letter – June 2011

Setting from Statistical Principles

A new approach to quantitatively model the formation of cement hydration products, including their mechanical properties is proposed based on basic statistical mechanics. With the bottom-up philosophy, the input comes directly from the atomistic composition of solution and precipitates. Captured by cement-specific inter-particle potentials, investigation and control of microstructure and property evolution during setting become possible. more >>

Research Profile Letter – May 2011

Clinker Grinding at Breaking Point

This research highlights that the grinding technology currently in use in the cement industry has significant reserves for substantial energy efficiency improvements. The atomistic approach provides a baseline for the optimization of cement grindability. This optimization will also be most critical for the implementation of lower green-house gas components, such as belite, slag, fly ash and so on. more >>

Research Profile Letter – April 2011

What’s in Your Concrete? (Part 2)

This research combines nanoindentation and multivariate statistics to characterize quantitatively the mechanical response and volume fractions of phases in hardened cement paste. The comparable size of voxels in this mechanical analysis and our chemical characterization provides a formidable tool to relate mechanical performance to cement and concrete chemistry. more >>

Research Profile Letter - March 2011

Clinker: When Impurities Matter

This research highlights the critical role of guest ions on available reactive sites in alite and belite. The novel understanding of the role of impurities on reactivity opens the possibility for designing new doped clinker phases with a higher reaction rate, and hence, earlier strength development. Engineering the reactivity of belitic cements could thus become a reality through an appropriate choice of impurities. more >>

Research Profile Letter - February  2011

What’s in Your Concrete? (Part 1)

Concrete is defined by its properties in the hardened state. However, these are known to depend strongly on the chemical make-up created by the tens of chemical hydration reactions that take place when cement clinker phases react to form this cohesive liquid stone. This research combines in situ X-ray spectra and multivariate statistics to characterize quantitatively the chemical signature and volume fraction of phases in hardened cement paste. more >>

Research Profile Letter - January 2011

Toughness Simply by Scratching

Scratching a weaker material with a tougher one is no doubt the most elemental conceptualization of a materials test ever conceived by mankind. This research highlights the relevance of the scratch test for assessing fracture properties of cement-based materials at multiple scales. This research makes it possible to identify reserves in concrete design that could enhance the crack resistance of concrete materials. Moreover, the test can be conducted over a period of time on the same sample that provides a benefit of evaluating the evolution of properties with time. All this makes the scratch test most appealing for innovative concrete applications. more >>

Research Profile Letter - December 2010

C-S-H: Water, Water Everywhere

This research highlights the importance of the water content within C-S-H on the properties of this nanoscale phase. As water content decreases, the stiffness and strength of the individual particles increases. Water content may be varied by environment, or controlled by C-S-H composition. This model can now be extended to predict how chemical composition, temperature, and humidity can affect the density and mechanical behavior of the aggregated C-S-H nanogranular phase that forms the “liquid stone” of concrete. more >>

Research Profile Letter - November 2010

The Hidden Forces of Setting

This research highlights the importance of the
interaction forces between the liquid and solid components of cement hydration (clinker, CH, C-S-H, pore solution etc). The approach holds the promise to become a quantitative bottom-up engineering tool for a science-driven engineering design of the next generation of setting agents including chemical admixtures. more >>

Research Profile Letter - October 2010

Quantum Clinker Engineering

This research highlights the critical role of the crystal structure of alite and belite on the dissolution energetics. This novel understanding of the dissolution chemistry eventually holds the key to designing potential dissolution accelerators and retarders for the activation of lower greenhouse components such as belite so that they can be used in demanding construction schedules. more >>

Special Research Brief – October 2010

Locking Mercury into Concrete

This research suggests that C-S-H can safely host mercury while maintaining full chemical stability and mechanical performance, when less than 2% of calcium sites are exchanged for mercury. To fully recap the benefits of higher strength and durability of concrete with high fly ash concentrations, it may turn out beneficial to limit the mercury content in fly ashes for concrete. more >>

Research Profile Letter - September 2010

Fly Ash is Critical For C-A-S-H

This research highlights the beneficial role of aluminum substituting for calcium on chemical stability and performance of C-A-S-H. It suggests that a high amount of aluminum provided by a larger fly ash concentration than currently in use can enhance properties in a "bottom-up" fashion. more >>