APPENDIX A
Case Study on Cementitious Materials
A.1 Definition and Timeline
The Exploratory Advanced Research (EAR) Program at the Federal Highway Administration (FHWA) has funded multiple projects researching topics related to cementitious materials (CM). Broadly speaking, CM research examines methods and materials to extend, enhance, or replace construction materials including cement and concrete. The EAR Program supported several projects in CM research during the period from 2008 through 2018 (discussed in Section A.2.2). Subtopics explored under the EAR Program include modeling and simulation of the chemical processes in cement and Portland cement, research on additives to reduce production costs or add durability (called supplementary cementitious materials or SCMs), and developing alternatives to conventional cement.
Despite their widespread use, the chemical and physical processes that form cementitious compounds are not well understood. One area of active research relates to the use of fly ash (a by-product of coal-fired electricity plants) as an additive in cement. As coal power plants are being decommissioned, the supply of fly ash is dwindling. Substitute materials are needed and may offer opportunities to improve the performance of concrete. Other research in this area focuses on decreasing the environmental impact of cement and concrete production. Those processes involve high heat, resulting in the release of substantial volumes of carbon dioxide, contributing to the problem of global climate change. Underlying these research thrusts is the need for a more complete understanding of the fundamental chemical processes that give cement its physical properties.
A.2 CM Research: Initiation and Evolution
Reflecting the overall research approach for the EAR Program, the projects in CM research reflect two broad thrusts. Several efforts investigated new types of materials that could be used as additives or components in concrete, similar to traditional cement. More fundamentally, the EAR Program supported work that could change how new CMs could be discovered by modeling cement hydration from first principles using known chemical and physical processes and through the use of machine learning to identify and select candidate materials for use in CMs.
A.2.1 Rationale for CM as an EAR Topic
A substantial breakthrough in the production of CM would create widespread benefits for the highway construction industry because of the ubiquity of concrete in infrastructure. The development of new SCMs or alternate CMs could provide road construction companies with a broader range of materials. At the same time, the EAR Program sought to improve the ability
of industry to predict improvements in the performance of concrete using CMs. The prevalence of these materials also means that developing a marginally cheaper form of CM could generate enormous economic benefit. CM research offered potential breakthroughs to improve highway efficiency, reliability, durability, and cost.
The EAR Program first funded CM research from its original 2007 Broad Agency Announcement (BAA). Subsequently, the program sponsored two scanning workshops to identify key gaps in current research, focused on cement hydration kinetics and nanoscale dynamics. This led to a focus on nanoscale research in the 2009 BAA, with two subtopics focused on CM. This was followed in 2011 by a BAA topic on the modeling of cement hydration kinetics, particularly for new simulations beyond the CEMHYD3D modeling package. In 2012, the program turned to research on binders (materials enabling the integrity of concrete) and alternatives to traditional CMs, and funded further research on those two topics in 2018. A workshop on multiscale materials modeling in 2013 helped FHWA and EAR-funded principal investigators (PIs) understand the practical and applied issues that modeling efforts must consider.
A.2.2 CM Project Selection
Given the range of subtopics within CM research, the EAR Program recruited a wide variety of experts to serve on the proposal review panels for these topics. For the initial EAR Program BAA in 2007, topics were broadly defined, requiring over 60 reviewers drawn from FHWA, TRB, several state departments of transportation (DOTs), and a number of universities. Later proposal selection panels on CM research topics involved experts from universities, other federal agencies such as the National Institute of Standards and Technology (NIST), the Army Corps of Engineers, industry groups such as the Asphalt Institute, private consultants, and some National Research Council (NRC) Research Associates. Most of the panels were chaired by Richard Meininger, head of the Office of Infrastructure R&D at FHWA, helping to ensure that proposals aligned with FHWA R&T’s needs and priorities.
Across all panel reports, the role of partnerships distinguished many successful proposals from unsuccessful ones. Because the EAR Program’s interest in CMs emphasized the potential to deploy new materials in construction, several projects involved collaborations with state DOTs and industrial firms, as well as FHWA. Projects that addressed performance analysis and standardization issues were viewed as particularly valuable. For example, a proposal on inorganic polymers for use as binders in cement promised to produce a “virtual toolkit” to help engineers decide how to employ those polymers in production. Industry partners were especially important for sourcing materials used in research.
The topic on modeling cement hydration kinetics in the 2011 BAA illustrates how the EAR Program itself leveraged partnerships. The topic definition was motivated by the desire to leverage more fully the capabilities developed at NIST in materials modeling, particularly through the Virtual Cement and Concrete Testing Laboratory. The fundamental work on modeling pioneered by Jeffrey Bullard and his colleagues at NIST offered an opportunity to revolutionize the development of new simulation models for materials. The funded proposal led by Princeton University integrated the expertise of four academic partners with the NIST work and included an industry partner (W.R. Grace & Co.) to help understand the use of such models in practice. The EAR Program needed to orchestrate the involvement of NIST through a separate interagency agreement, which was then linked to the activities of the Princeton team.
Throughout the project selection reviews, experts noted that EAR projects needed to include practical considerations such as cost realism, the management expertise of PIs, and access to facilities and materials. Still, the panels often rewarded proposals deemed especially “ambitious”
or “pioneering.” The overall investment in CM research increased over time, from a single project in 2008 budgeted below $200,000 to projects totaling between $1 million and $2 million per year in 2010, 2012, 2013, and 2014 and three projects with funding in 2019 totaling over $4.5 million. The funded projects related to CM are listed in Table A-1.
A.2.3 CM Project Oversight and Management
The Agreement Officer’s Technical Representatives (AOTRs) who provided project oversight on behalf of FHWA played a significant role in CM research projects. PIs reported in survey responses that FHWA involvement in their projects was either “effective” or “very effective.” During interviews and in open-text responses to the survey, PIs mentioned specifically that their FHWA oversight officer would suggest conferences for presenting their research results, arrange briefings to FHWA research and policy offices, connect the researchers with standards organizations such as American Association of State Highway and Transportation Officials (AASHTO) and the American Society for Testing and Materials, and recommend materials for experimental use that helped to lower project costs. Several individuals interviewed noted that the CM research community in the United States is fairly small and that FHWA staff are very well connected within the field. Therefore, the oversight staff could connect PIs with experts on any topic needed.
The EAR Program has performed formal Technology Readiness Level (TRL) assessments for the more recent CM research projects but apparently not for earlier projects. The Program generated TRL reports for the 2012 project on modeling cement hydration kinetics at Princeton
Table A-1. CM-related projects funded by the EAR Program.
| Project Title | Project Dates | Team |
|---|---|---|
| Crack Resistant Concrete | 2008 | Texas A&M, Texas Transportation Institute |
| Increased Use of Fly Ash in Hydraulic Cement | 2011–2015 | Purdue with Auburn, NIST, NRMC Association |
| Paving the Way – Extending the Life of Concrete | 2011–2015 | UC Berkeley |
| Mechanisms of Hydration and Setting of OPC | 2013–2015 | Princeton with NIST, Oklahoma State, Rice, UC Santa Barbara, W.R. Grace & Co. |
| Novel Alternative Cementitious Materials for Development of the Next Generation of Sustainable Transportation Infrastructure | 2012–2017 | Georgia Tech with Oklahoma State, Tourney Consulting Group, U.S. Army Corps of Engineers |
| Inorganic Polymers – OPC-Free Binders | 2013–2015 | UCLA with UCSB, UT-Austin, Boral Materials |
| Machine Learning to Predict Use of SCMs | 2019–2022 | UCLA with Missouri Univ. of Science & Tech, Arizona State University, Boral Materials |
| Performance-Based Classification for Fly Ash | 2019–2022 | Oklahoma State with Georgia Tech., Ohio State, Diversified Engineering Services, Boral Materials, Minnesota DOT, Oklahoma DOT, Southern Company |
| Nontraditional and Natural Pozzolan Based SCMs or Inorganic Polymers for Transportation Infrastructure | 2019–2022 | Purdue with Penn State, Clarkson University |
and a 2014 project on alternative CMs at Georgia Tech. This is reflected in the survey responses; of seven PIs who led CM projects, only two seemed aware of these assessments. The EAR Program also sponsored the development of information technology (IT) assessments for modeling software, especially through outside partners such as the Volpe National Transportation Systems Center or Oak Ridge National Laboratory (ORNL). The impact of these assessments on the researchers themselves is unclear. One researcher felt that the EAR Program helps to focus projects on technology transition by encouraging TRL analysis, while another felt that the assessment process was too abstract to be useful.
A.3 CM Research Outcomes
CM research produces a variety of research outputs and outcomes in a manner that is different from most fundamental academic research. The EAR Program has developed a draft logic model for its CM research investments, shown in Figure A-1. Although some CM research produces traditional scientific journal articles, the focus on both materials and modeling generates other types of research products:
- Software and software toolkits for computational modeling of materials
- Sample materials for further experimentation
- Data on the performance of materials tested in research
- Inputs to materials and construction standards
- Recommendations on materials suitable for deployment
PIs responding to the survey offered a wide array of examples of their research results, including code for modeling contributed to the open-source community, new applications of testing methods, new standards or research protocols, and potential new materials. The uptake of these outputs is difficult to trace. Researchers believed that these outputs would be most helpful to other academic researchers and to FHWA, but they also directed their research results to benefit state DOTs and to a lesser extent private firms.
FHWA has been a key beneficiary of the CM research funded by the EAR Program. Staff at FHWA R&T Offices noted that bio-based alternative CMs had been considered a promising area for in-house research, but that topic had been set aside because of other priorities. The EAR Program’s project on that topic provided FHWA with the evidence to assess the feasibility of such research, concluding that further research was not warranted.
PIs and FHWA staff pointed out that standards bodies provided a venue for disseminating research results in a manner that is unlikely to be documented. Consensus standards committees frequently include private-sector representatives, so presentations to these groups convey EAR-generated knowledge from academia to industry, even if the results are not yet feasible for deployment.
EAR Program support for CM research also benefits other federal agencies. In particular, the Army Corps of Engineers has worked with PIs on EAR-funded projects to help with their specialized construction needs. One researcher reported that his research has been funded by the Corps to help determine if they can produce cement from different types of soil and minerals found in terrain where the military operates (such as deserts or mountainous regions). Using local materials in cement would reduce the volume of supplies that would need to be transported over long distances for military construction. Some of the EAR-funded CM research is also being applied by NASA to determine whether lunar dust can be used in cement for building permanent human-habitable structures on the Moon. There appears to be nascent interest in the work at the University of California, Los Angeles (UCLA) using computational methods from artificial intelligence to identify SCMs.
CM research did produce a substantial body of literature, totaling at least 79 articles and conference presentations identified through literature searches. Over half of those publications are attributed to two projects: the Princeton project on modeling cement hydration kinetics and the UCLA project on inorganic polymer compounds as binders. These two projects seem fairly fundamental in nature. A researcher with the Princeton project readily admitted that the work with NIST on developing a new computational model for cement hydration has not yet produced a new model that can be used in the field, but it has developed other insights into the topic that are being applied in research.
