Objective - To develop and deploy measurement science to reliably assess the current and future performance of engineered materials in support of resilient civil and social infrastructure given exposure to chronic (e.g., materials degradation) and episodic (e.g., earthquakes) hazards.
What is the Problem?
Infrastructure is essential for commerce (e.g. bridges, communication lines, water, and energy) and to protect the population (e.g. buildings, hospitals). Ideally, all infrastructure should be resilient and constructed with economically efficient materials for which the remaining service life is predictable with a plan for maintenance. Although the American Society of Civil Engineers (ASCE) advocates that “Bridge owners should consider the costs across a bridge’s entire lifecycle to make smart design decisions and prioritize maintenance and rehabilitation” [ASCE 2017], an accurate life cycle cost is not yet possible due to crucial materials durability data. Moreover, while progress has been made to characterize the performance of construction materials, it is yet not possible to ensure the appropriate selection of materials using realistic predictive methodologies to forecast the performance of materials under actual operating conditions for most materials and systems used in construction [Watson et al., Dec 2016].
It should be further determined which type of structures (buildings, roads, bridges, energy, communication, water, etc.) would benefit the most from the ability to select and assess engineered materials with known performance and resilience. Per Dr. T.D Marcotte, CVM engineering, ACI 318, the Building Code adopted by most American municipalities, does not contain provisions for durability requirements for construction, stating that models are needed to predict durability and include them in a specification. This is considered a major issue by the construction industry - for example, in 2017, both the ACI- SDC (Strategic Development Council) and the American Composites Manufacturing Association (ACMA) held workshops dedicated to advancing the science of durability of concrete and polymeric composite materials, respectively. In this Program, a resilient infrastructure is defined as constructed in a way such that the functionality is retained during and after an episodic or chronic hazard. For example, a building would not be very useful if water pipes, electricity and/or gas, sewage and communication (e.g. telephone, internet) were deficient; thus, they are part of the building functionalities. Presidential Policy Directive 21 (PPD21, 2013) defines community resilience as the ability of a community to prepare for anticipated hazards, adapt to changing conditions, and withstand and recover rapidly from disruptions. Therefore, a community cannot recover unless the infrastructure is viable and operational. This would imply that buildings, roads, and utilities are both structurally intact and operational. As a chain is only as strong as its weakest link; for a structure to be operational, sustainable, and resilient, all essential components must have the required. The common denominator of any infrastructure components are the materials selected to construct them. A great design, with incorrectly selected materials, would lead to materials failing prematurely and may require that the structure either be repaired or closed. When the material selection is adapted to the environment and the usage of the structure, then the whole element is resilient.
What is the technical idea?
To ensure that materials perform as needed for the expected service life of the infrastructure, knowledge and prediction of the service life of the materials are necessary. Today, the selection of materials for new construction and the estimate of the remaining service life of materials already in place is left to the engineer and the inspector, respectively. They generally do not have all the knowledge needed to choose the best materials for a most resilient structure. The technical idea is to address two main aspects that would ensure a resilient infrastructure: 1) materials selection, by providing tools and methodologies using realistic predictive methodologies; and 2) materials assessment by developing tools or tests to assess the condition of the material at the time of the measurement at any age. These two thrusts will allow prediction of service life and remaining service life and potentially determine possible maintenance needed to extend the service life of the material. It will allow development of tools for engineers, inspectors, and owners to make decisions on materials based on an accurate projection of the time and exposure dependent conditions of the structure.
If the information is known for each material in a structure, the next stage would be to determine the status of the entire structure by combining all the material service curves for the structure and working directly with other programs (structures, etc.) to conduct validation studies. It could be assumed that the structure would fail (no longer functional) if the most critical component fails or is sufficiently deteriorated. This information could then be integrated with other programs in the resilience goal to ensure that models have the materials parameters needed to inform a community for planning resilience.
What is the research plan?
The Program plan consists of two phases. In the first phase, the Program will have two near-term objectives: 1) develop a strategic plan that identifies the most important measurement science challenges for achieving resilient buildings and infrastructure by material selection and assessment; and 2) complete the legacy activities from the preceding 7-year sustainability programmatic thrust. In the second phase of the Program, as the legacy activities are completed, the resources will be redirected towards the resilience measurement science challenges identified in the strategic plan. It is anticipated that the strategic plan will identify impactful measurement science needs to address two main thrusts:
Materials Selection: To maintain resilience, it is necessary to build or repair infrastructure with the appropriate materials to achieve the desired level of performance for the anticipated hazards. Thus, tools are needed to ensure that the selection of materials is done using science-based predictive methodologies that forecast the performance of materials under actual operating conditions both in new 2
construction and in repair. NIST will develop tools and methodologies to predict the performance of materials needed for new construction and for repair.
Materials Assessment: To have a resilient community, it is necessary that the infrastructure is operational at all times. Operational infrastructure implies that all the parts of a structure (from roads to schools, hospitals, power/energy generation & distribution, communication) operates as designed. Thus, tools and methodologies are needed to assess an existing structure’s current performance. NIST will develop tools and methodologies to assess the performance of materials used in an existing structure and predict its remaining service life.
The legacy projects within the Program will take up to three-years to realize their objectives. Outputs from several projects will go into a polymeric and cementitious materials database, comparable to the MML Materials Data Curation System framework, and will consist of materials properties as a function of a variety of environmental stressors or other variables so that stakeholders can use the data to develop predictive models for their products. Another legacy project output is the commercialization of a NIST-traceable weathering device and development of complementary standard test methods to improve accuracy of accelerated aging for our stakeholders. To ensure that future projects within the Program are the most impactful for the new resilience focus, milestones in two projects will be included to complete a rigorous analysis of the resilience community sectors to map out research space. All the proposed legacy sustainability projects contribute to one or both thrusts; therefore, the legacy activities achieve planned impacts and can contribute to future program impacts. The projects objectives are listed here:
Direct Assessment of Concrete-Making Materials for Standards and Specification: To develop and promote new standard test methods and specifications for cement and concrete materials based upon a comprehensive assessment of mineralogical, chemical and textural properties.
Hydration Reactions in Microstructures: Generate and publish reaction rate data and enhanced computer modeling tools to better understand and predict the rates of microstructure development and phase interactions in portland cement concrete binders.
Additive Manufacturing with Cement-based Materials: Develop measurement science tools (metrologies, standards, and guidance documents) for quantitatively evaluating the critical material properties and ensuring the desired field performance of cement-based additive manufacturing.
Accelerated Weathering and Service Life Prediction of Engineered Polymer Materials: Develop indoor accelerated and outdoor weathering property-performance database, traceable measurements, validated statistical models for service life prediction models of engineered polymer materials for resilient infrastructure.
NIST Accelerated Weathering Laboratory: Metrology and Technology Transfer: To maintain, improve and expand capabilities at the NIST Accelerated Weathering Laboratory (AWL) to conduct safe, accurate and traceable aging experiments and to enable transfer of the SPHERE technology to industrial stakeholders.