Living Materials Laboratory
Srubar Research Group

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Research Statement
Conventional building and construction materials are both resource- and energy-intensive to manufacture, and their production contributes to greenhouse gas emissions, global warming, and climate change. With the ultimate goal of reducing the environmental impact of materials used in construction, our research focuses on the development, durability, and service-life modeling of innovative, sustainable materials for both structural and non-structural applications. By maximizing resource productivity, longevity, and recovery, sustainable materials exhibit a transformative potential to enhance the global sustainability of our built and natural environments.

Current Research Projects
Our current research projects address questions at nexus of materials science, architecture, and chemical, biological, environmental, and structural engineering. Due to the breadth and depth of our materials research endeavors, we actively collaborate with colleagues both within and outside of the Department of Civil, Environmental, and Architectural Engineering in the areas of polymer synthesis, computational mechanics, materials science, sustainability, bioengineering, and architecture. We are always looking to strengthen our research through the multidisciplinary perspectives of our colleagues.

Programmable Resurrection of Materials Engineered to Heal Exponentially Using Switches (PROMETHEUS): The primary objective of this work is to engineer a hybrid living material composed of an inert structural scaffold (i.e., sand) that supports the rapid growth and long-term viability of living cells (i.e., microorganisms) that endow the final material with both biological (i.e., self-repair) and structural (i.e., load-bearing) function. The project team aims to develop a novel material technology that will enable scalable and non-linear, exponential manufacturing of material and structural systems that function as living, regenerative components, thereby attaining a quantum leap in construction technology. Sponsor: Defense Advanced Research Projects Agency.

Experimental Study of Biomimetic Antifreeze Polymers for Improved Durability of Cementitious Binders: Ice is one of the few substances on Earth that expands when it freezes. Consequently, this expansion is destructive to porous materials, like concrete that are exposed to water and experienced freeze-thaw cycling. Conventional methods used to counter freeze-thaw deterioration in cement-based materials include entraining ~5-10% air (by volume), which reduces bulk mechanical properties, or applying deicing salts on the surface, which exacerbates chloride-induced corrosion of steel reinforcement. For more than 70 years, these methods have remained virtually unchanged. Inspired by nature, this work seeks to design and synthesize biomimetic antifreeze polymers (BAPs) that explicitly mimic the activity, function, and structure of antifreeze proteins (AFPs) naturally found in plants, insects, and bacteria and assess their suitability as an admixture biotechnology for cement-based materials. Sponsor: National Science Foundation.

Nanostructural Stability of Alkali-Activated Geopolymer Cements: The manufacture of ordinary portland cement (OPC) is responsible for approximately 8 percent of global carbon dioxide emissions. While preliminary research has shown that low-calcium fly ash- and metakaolin-based alkali-activated geopolymer cements can provide a durable, low-carbon alternative to Portland cement (especially for water infrastructure applications), the actual physical and chemical degradation mechanisms of alkali-activated geopolymer cements are poorly understood. The specific objective of this research is to investigate the time-dependent stability of geopolymer gel nanostructures in the presence of both physical and chemical environmental stressors. Understanding and controlling these degradation mechanisms is a vital next step to ensure both the sustainability and long-term durability of geopolymer-based cementitious materials prior to their widespread use in civil infrastructure applications. Sponsor: National Science Foundation.

Acquisition of a 4D High-Resolution X-Ray Micro-Computed Tomography System for the Rocky Mountain Region: This Major Research Instrumentation award to acquire a high-resolution X-ray microtomography (XRM) imaging system will advance a broad spectrum of fundamental research, potentially leading to novel materials that enhance infrastructure resilience, next-generation medicine, and energy production. The instrumentation, which is not currently available to researchers in the Rocky Mountain region, uniquely combines an X-ray source with an objective turret to attain exceptional spatial resolution and unprecedented image quality. The instrumentation will advance critical research areas, including next-generation civil infrastructure materials, biological tissues and materials for tissue repair and regeneration, natural and archival materials, smart polymers, and energy collection and storage. Sponsor: National Science Foundation.

Design Optimization of Sustainable and Resilient Concrete Mixtures: Worldwide, concrete is the most prevalent building material and the second-most consumed material on Earth after water. Given the environmental implications of its increased use, structural engineers are now faced with critical decisions regarding the design and specification of concrete mixtures that meet environmental, economic, structural, and durability performance criteria. Conventional mix design methods employ time-intensive, trial-and-error approaches, which ultimately yield acceptable (but non-optimal) designs of concrete mixtures. The goal of this work is to create, validate, and test a new paradigm for the design of concrete mixtures using a many-objective optimization approach. This work will define, formulate, and link mathematical models that relate concrete mixture proportions to fresh- and hardened-state properties. These properties, along with expected in-situ exposure conditions, will be used to quantify in-service performance as it relates to sustainability (e.g., environmental impact) and chronic-hazard resilience (e.g., corrosion resistance, freeze-thaw resistance). Significant effort will be placed on improving optimization approaches, quantifying uncertainty, and conducting sensitivity analyses to identify the most influential parameters for the design of sustainable and resilient mixtures. Sponsor: National Science Foundation.

Characterization and Valorization of Recycled Polycarbonate: The University of Colorado Boulder is working closely with our partners, Revision Solutions, LLC and the leading optical lens manufacturers in the nation, to reuse the non-biodegradable waste (sward) created from making eyeglass lenses (swarf) and divert it from local landfills. Over 6,000 tons of swarf contaminated with bisphenol-A (BPA) is generated each year by the eyeglass industry alone. BPA and other contaminates in eyeglass swarf may leach into groundwater and impact the ecosystem. Our scientific team is researching safe and environmentally friendly reprocessing pathways for safe and efficient extraction of impurities, remanufacturing, and valorization of the polycarbonate-based material. Sponsor: ReVision Solutions, LLC.

Mechanics-based Service-Life Prediction of Natural Fiber Composites: Natural-fiber composites (NFCs) have gained in relevance over the past few decades as sustainable alternatives to synthetic-fiber composite materials. However, widespread application of NFCs remains limited due to concerns regarding their durability in high-humidity and wet environments. Previous moisture-related durability research has been empirical in nature. The objective of this research is to use micromechanics to predict moisture- and frost-induced damage in both short- and continuous-fiber NFCs that are exposed to fluctuating hygrothermal conditions. Experimental work includes meso- and nano-scale mechanical testing to correlate moisture content and temperature with reductions in mechanical properties of fibers, matrices, and composites thereof. Computational work includes formulation of diffusion-based moisture transport and micromechanical damage models to account for fiber softening and expansion. Validated models will then be used to predict in-situ degradation and to estimate functional obsolescence (end of life) in a variety of applications and geographic locations. These estimates will be integrated into a probabilistic lifecycle assessment framework to calculate true environmental impacts across variable spatial and temporal domains. Sponsor: National Science Foundation.

Sustainable Synthesis of Gelatin Foams and Bioaerogels: Polymer foams are ubiquitous – applications exist in several fields from packaging to construction to tissue engineering. However, their manufacture often utilizes inorganic (i.e., silicon) or non-renewable, petroleum-based materials, extreme high/low temperatures, and/or aggressive chemical solvents. Leveraging a recent discovery in our lab, this work seeks to elucidate and leverage a novel mechanism for the environmentally benign synthesis of gelatin-based foams and bioaergoels – a class of ultra-light, ultra-porous materials made from a renewable, sustainable, and biocompatible source – for a variety of potential applications. While the main objective of this research is to understand the fundamental process-structure-property relationships, the long-term goal of this work is to use this new knowledge as a springboard for the design and synthesis of other protein- and polysaccharide-based bioaerogel materials. Sponsor: University of Colorado Boulder.

Other projects include investigations in Superabsorbent Biopolymers for mitigating autogenous shrinkage in portland cement-based materials, Hygrothermal Durability of Engineered Wood Products, Transparent Wood, and Carbon Sequestration Potential of Ordinary Portland Cement (OPC) Concrete.

For more information or to get involved in these efforts, please contact Dr. Wil Srubar:

Suni Suni Suni University of Colorado at Boulder / Department of Civil, Environmental, and Architectural Engineering
© 2013 W Srubar III