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ECLIPS WORKSHOP IN BRUSSELS, MARCH 23, 2017

https://www.eventbrite.fr/e/eclips-workshop-innovative-sustainable-concrete-pavements-tickets-29215432144

Enhancing Concrete Life in Infrastructure through Phase-Change Systems (ECLIPS), advances a transformational concept based on incorporating climate, and application-specific phase-change materials (PCMs) into concrete to for increased durability and lifespan of new road infrastructure.

The ability to incorporate PCMs into the concrete matrix has implications on enhancing a range of material-and-structural performance descriptors. The intelligent (i.e., temperature-sensitive) storage or release of thermal energy by PCMs provides an adaptive capability to concrete, when embedded with PCMs, to regulate its internal thermal environment. This proposal, ECLIPS, builds on the ability of custom PCMs to:

  • limit temperature rise and associated early-age deformations in concrete to reduce the risk of thermal cracking
  • restrict the magnitude of diurnal-or-seasonal temperature variations and deformations of restrained concrete elements over long time scales to limit damage due to thermal fatigue
  • provide self-thawing/warming capabilities to concrete thereby rendering concrete more resistant to freeze-thaw action, and related damage

Research

Microencapsulated phase change materials in concrete

 

Phase change materials (PCMs) are combined sensible-and-latent thermal energy storage materials that can be used to store and dissipate energy in the form of heat. Several methods have been advanced to incorporate PCMs in concrete, including direct incorporation and in the form of microencapsulated particles. Microencapsulated PCMs, that are commercially available in a powder form, can be directly added during the mixing process of concrete.

The other common approach is to employ macro encapsulation, which refers to the impregnation of PCMs as a liquid into the pores of lightweight aggregates, which are then used as inclusions in concrete. The influence of microencapsulated PCMs on semi-adiabatic temperature rise and cool-down rates in hydrating cementitious systems, the development of restrained thermal stresses and strains that result in thermal cracking, and on the fracture properties have been elucidated.

PCMs having suitable phase change enthalpy and phase transition temperatures can also:

  • restrict the magnitude of diurnal-or-seasonal temperature variations and deformations of restrained concrete elements over long time scales to limit damage due to thermal fatigue, and
  • help limit the number and/or intensity of freeze-thaw cycles experienced by exposed concrete structures.

The applications described above require concretes to demonstrate adequate thermo-physical and mechanical properties over extended time periods. This necessitates a fundamental characterization of the PCMs and their effects on cementitious systems in order to design:

  • mechanical performance-equivalent systems containing adequate amounts of PCMs as needed to satisfy thermal requirements, and/or
  • microencapsulated PCMs capable of enduring mechanical and chemical stresses produced during mixing and placing concrete, and induced due to the high pH cementitious environment.

Phase change materials in porous inclusions

 

This study develops core knowledge needed to incorporate liquid-PCM into porous lightweight aggregate (LWA) hosts. PCM in liquid state is impregnated into the pores of LWAs. This overcomes one of the main disadvantages of lightweight structures as building envelopes, i.e., their low thermal inertia.

Large temperature fluctuations in such buildings can be reduced through the use of PCM incorporations, in addition to providing increased thermal insulation. Moreover, this approach can also be used in applications such as bridge-decks to limit the number and/or intensity of freeze-thaw cycles experienced by concrete and to reduce the rate of thermal deformation and stress development by controlling the semi-adiabatic temperature rise.

The amount of heat stored and released by PCMs contained within the pores of LWAs depends on the pore structure of the LWA as well as the thermal properties of the PCM (i.e., enthalpy, specific heat, and phase transition temperature). Thus a fundamental characterization of PCMs and LWAs is important in properly understanding their thermal response and the efficient design of LWA-PCM composite mortars.

Thermal efficiency of concrete containing PCM

 

Temperature changes driven by hydration reactions and environmental loading are a leading cause of thermal cracking in restrained concrete elements. This work describes preliminary investigations on the use of microencapsulated phase change materials (PCMs) as a means to mitigate such thermal cracking.

Special attention is paid to quantify aspects of heat absorption and release, the development of unrestrained/restrained thermal stresses, and strains and the mechanical properties including: compressive strength, elastic modulus and fracture behavior.

  • First, PCMs incorporated in cementitious systems absorb and release heat, which scales as a function of their dosage and enthalpy of phase change.
  • Second, for restrained and unrestrained conditions and for equal temperature change, the thermal deformation and stresses developed are noted to be similar to a plain cement system independent of the PCM dosage. However, PCM additions are noted to reduce the rate of deformation and stress development so long as the phase transition is active.
  • Third, while the presence of PCMs depresses the compressive strength and elastic modulus (in increasing proportion with dosage), the fracture toughness is impacted to a lesser degree.

 

Modeling of concrete properties at early and later ages

 

Schematic of the heat transfer model for simulation of early age properties

 

Transient temperature evolutions within pavement sections composed of (a) plain concrete, and (b) concrete containing PCM (ϕc+s = 0.1). The pavements were poured at 6:00 am and exposed to outdoor temperature and solar radiation corresponding to a hot September day in Los Angeles, CA.

Crack control using PCMs

 

Schematic of the heat transfer model for simulation of early age properties

Designing novel means of encapsulation

 

Encapsulating PCMs in more resilient capsules so as to prevent damage is a novel idea that is being forwarded. We are researching a synthetic route for the silica microencapsulation of the mentioned PCMs by combining sol-gel reaction and emulsion technique. By the sol-gel method silica materials can be synthesized under very mild solution conditions and by applying emulsion techniques, encapsulation by that silica material can be obtained. We are exploring different synthetic routes and different reaction parameters in order to obtain the best path for the synthesis of silica microencapsulated PCMs.

 

Microcapsules through the novel encapsulation route

Research Publications and Quarterly Reports

 

Research Publications

  1. Das, S., Maroli, A., and Neithalath, N., “Finite element-based micromechanical modeling of the influence of phase properties on the elastic response of cementitious systems”, Construction and Building Materials, Construction and Building Materials, Vol. 127, 153-166
  2. Aguayo, M., Das, S., Maroli, A., Kabay, N., Mertens, J., Rajan, S.D., Sant, G., Chawla, N., and Neithalath, N., “The influence of microencapsulated Phase Change Material (PCM) characteristics on the microstructure and strength of cementitious composites: Experiments and finite element simulations”, Cement and Concrete Composites, Vol. 73, pp. 29-41
  3. Falzone, G., Puerta-Falla, G., Wei, Z., Zhao, M., Kumar, A., Neithalath, N., Pilon, L., and Sant, G., “The influence of soft and stiff inclusions on the mechanical properties of cementitious composites”, Cement and Concrete Composites, 10.1016/j.cemconcomp.2016.05.008
  4. Thiele, A.M., Falzone, G., Wei, Z., Young, B., Neithalath, N., Sant, G., and Pilon, L., “Figure of merit for the thermal performance of cementitious composites containing phase change materials”, Cement and Concrete Composites, Vol. 65, 214-226
  5. Wei, Z., Falzone, G., Wang, B., Thiele, A., Puerta-Falla, G., Pilon, L., Neithalath, N., Sant, G. “The Durability of Cementitious Composites Containing Microencapsulated Phase Change Materials”, Under review in Cement and Concrete Composites
  6. Savija, B., and Schlangen, E., “Use of phase change materials (PCMs) to mitigate early age thermal cracking in concretes: Theoretical considerations”, Construction and Building Materials, Vol. 126, 332-344
  7. Aguayo, M., Das, S., Castro, C., Kabay, N., Sant, G., and Neithalath, N., “Porous materials as hosts for phase change materials in cementitious systems: Characterization, thermal performance and analytical models”, Construction and Building Materials, Vol. 134, pp. 574-584

Collaborators

Narayanan Neithalath is a Professor in the School of Sustainable Engineering and the Built Environment at Arizona State University. His research interests include development and multi-scale characterization of novel binder systems, carbonation of waste metallic powder from several industrial operations and municipal waste streams to provide a ceramic-like binder material with multi-functional applications (EM shielding, blast/impact resistance, high strength), use of phase change material embedment to provide energy-related benefits to building envelope systems and crack control to concrete structural elements, and its quantification, microstructure characterization and performance, microstructure-guided finite element modeling to aid in material design of novel engineering materials with enhanced properties.

Gaurav Sant is an Associate Professor & Henry Samueli Fellow in the Department of Civil & Environmental Engineering at University of California, Los Angeles. Research Interests include cementitious materials and porous media with a focus on chemistry-microstructure-engineering property relationships, electronic structure calculations, geochemical phase equilibria and their simulation, damage and cracking in concrete at early ages, thermodynamics of inclusion-matrix and solid-liquid-vapor interfaces, durability prediction and service-life extension of civil engineering infrastructure, carbon footprint minimization of construction materials.

Pietro Lura is the Head of the Concrete and Construction Chemistry Laboratory at EMPA since 2008 and professor at ETH Zurich, Institute of Building Materials, since 2011. His research interests include hydration and early-age properties of concrete, in particular microstructure development, shrinkage, setting, early-age cracking and internal curing. In these fields he has done important contributions to both understanding of the fundamental mechanisms and to advancement in the state of the art.

Erik Schlangen is Professor in the chair of "Experimental Micromechanics” at the faculty of Civil Engineering and Geosciences at Delft University of Technology in the Netherlands. He is also the director of the Microlab for micromechanical and material research which is part of the same University. Prior to joining Delft University he was a senior materials engineer at the materials research institute Intron in the Netherlands. He is specialized in fracture mechanics of quasi-brittle materials like concrete, durability mechanics, finite element modeling, design of experimental techniques and self-healing of concrete and asphalt. He is the inventor of the Delft lattice model for simulation of fracture. He owns a patent on healable concrete. He initiated the self-healing bacterial concrete and is the inventor of the self-healing asphalt with steel-wool and induction heating that is applied in several applications.

Edurne Erkizia

Edurne Erkizia is a research scientist in the Materials team within the Sustainable Construction Division of Tecnalia, a research center located in the Basque Country in northern Spain. She is part of the Green Concrete Design Group within the Materials area led by Dr. Jorge S. Dolado. This group aims to develop innovative and sustainable materials (mainly cement-based) for the construction field. She has participated in a number of different research projects related to the improvement of cementitious based materials at an international as well as national level and she has taken part as an inventor in several patents. In recent years she has been working in the field of silica microencapsulation using sol-gel chemistry to encapsulate materials that, when added to the cementitious matrix, might provide it with novel properties such as self-healing or new thermal capacities. She is the author of several scientific papers and presentations.

TECNALIA (http://www.tecnalia.com) is a private, independent, non-profit research organization. Legally a non-profit foundation, TECNALIA is the leading private and independent research and technology organization in Spain and one of the largest in Europe, employing more than 1,300 people. The group involved in this project is the Green Concrete Design Group, which is part of the Sustainable Construction Division of TECNALIA, whose activities comprise innovative and sustainable materials, restoration, building, and the energy efficiency and safety of buildings and infrastructures. The Construction Division of TECNALIA works to promote the transformation and sustainability of the construction industry through a comprehensive vision of the technology and the market that generates new business opportunities for our clients. TECNALIA deploys a great part of its scientific and technological activity to the study and improvement of cementitious materials.

Partners

ASU is the largest public university in the United States with over 82,000 students spread across its four campuses. Its research enterprise is among the largest in the US. ASU is home to the Global Institute of Sustainability and the School of Sustainability, which are the first of its kind in the US. The Schools of Engineering at ASU is also among the largest in the U.S in terms of enrollment in undergraduate and graduate programs. ASU is the overall coordinator of the ECLIPS effort. In addition to the technical tasks listed in the proposal, ASU is also be responsible for the coordination between the technical and industrial partners, and dissemination efforts. The School of Sustainable Engineering and Built Environment (SSEBE) at ASU has an active ongoing research program on the materials science of cementitious materials.

UCLA is the largest campus of the University of California system, hosting over 41,000 students. UCLA is consistently ranked amongst the top universities in the world. UCLA Engineering is currently ranked as the top-public engineering school in the United States. The UCLA team has extensive experience in addressing strategic infrastructure research goals. Activities will be carried out within the Laboratory for the Chemistry of Construction Materials (LC2)

Delft University of Technology (TUD) is the oldest, largest, and most comprehensive technical university in the Netherlands. The group involved in the project at Delft University of Technology, the Microlab is part of the Faculty of Civil Engineering and Geosciences. The Microlab is a fundamental research lab in which the projects have strong links with experimenting and modeling. Cement-based systems (e.g. concrete) are the primary area of research. Interest and experience in Microlab research is driven by predicting material behaviour through understanding microstructure formation. Both the HYMOSTRUC-3D and Delft Lattice Model have been developed by this group.

Empa is an interdisciplinary research and services institution for material science and technology development within the Swiss ETH Domain (together with ETH Zurich and EPF Lausanne). The Concrete / Construction Chemistry Laboratory (26 researchers and technicians) is one of the leading laboratories worldwide in the fields of concrete technology and cement chemistry.