HYPERCON: Prediction and Optimization of Concrete Performance

Objective:

To develop and implement computational and experimental materials science-based techniques that will enable the prediction and optimization of the initial cost and service life performance and minimize the environmental impact of concrete in the built infrastructure.

Problem:

The most important overall problem in the U.S. and world-wide concrete industry, which drives HYPERCON research, has been neatly summarized by the National Ready-Mixed Concrete Association (NRMCA) in their bold P2P initiative. P2P stands for “Prescription to Performance” and indicates the desire of the NRMCA to change all concrete specifications from a prescriptive form, which does not allow innovation and proprietary formulation, to a performance form, which will drive innovation and research for proprietary advantage in the marketplace. The key problem for the industry and thus the key driver for the HYPERCON program is this: supporting workable performance specifications requires a much higher level of materials science understanding and performance prediction in the standard tests used by industry. This problem is hard to solve since concrete is a random, complex, multi-scale, time-dependent composite material. The P2P initiative carries significant weight in the industry, since ready-mixed concrete manufacturers use 75 % of all cement produced in the U.S. The key standard concrete tests involve component material analysis, workability, curing, mechanical properties, and transport and reaction mechanisms and rates (durability). This is exactly the technical core of the HYPERCON program and the reason behind its organization. The HYPERCON program, and its major product, the Virtual Cement and Concrete Testing Laboratory (VCCTL), are well positioned to help the concrete industry achieve the goal of transforming a prescriptive craft-based industry to a performance science-based industry by giving a materials-science based performance prediction capability to the cement and concrete industry. This concept can then be used in areas of the world like China and India, where there is an enormous and still-growing use of concrete almost totally without performance-based standards.

Guiding Documents: Various national and industry-wide documents have served to guide the HYPERCON research program from its beginnings in the early 1990’s. These include:

• The Status of Cement and Concrete R&D in the US – National Material Advisory Board, NRC (1980) NMAB-361
• The Nation’s Public Works: Defining the Issues – National Council of Public Works Improvement (1986)
• Concrete Durability: A Multibillion-Dollar Opportunity - National Material Advisory Board, NRC (1987) NMAB-437
• Infrastructure for the 21st Century: Framework for a Research Agency – NRC Committee on Infrastructure Innovation (1987)
• High-Performance Construction Materials and Systems: An Essential Program for America and Its Infrastructure, ASCE Technical Report 93-5011 (1993)
• National Construction Sector Goals: Industry Strategies for Implementation – Subcommittee on Construction and Building, NSTC, CERF, NISTIR-GCR-95-680
• Vision 2030: A Vision for the U.S. Concrete Industry – ACI Strategic Development Council (2001)
• Roadmap 2030: The U.S. Concrete Industry Technology Roadmap (v1.0) – ACI Strategic Development Council (2002)

Approach:

The heart of the HYPERCON program is the experimental and computational materials science fundamental research core, which supports the applied areas of durability, property prediction, and cement and concrete standards and measurement science. An approach using a synergistic combination of experimental and computational materials science, in the world of cement and concrete, is unique to NIST, and is the only way to make headway in this complex, amorphous material. A former VCCTL consortium member has stated, “we can do empirical research. We need you (NIST) to do the fundamental research that we can’t do” (Mr. Al Innis, Vice-President for Quality Assurance and Research, Holcim). The various projects that make up HYPERCON are strongly inter-linked, each supporting the effort in other projects.

Recent Results:

• HYPERCON researcher Dale Bentz has received the American Concrete Institute’s (ACI) Wason Medal for Materials Research for the paper entitled “Mixture Proportioning for Internal Curing.” The Wason Medal for Materials Research was established by ACI in 1917 for “original research work on concrete materials and their use, or a discovery that advances the state of knowledge of materials used in the construction industry.” He was also selected as the recipient of the Frank G. Erskine award by the Expanded Shale, Clay, and Slate Institute for his research on internal curing using lightweight aggregates.

• HYPERCON program manager Edward Garboczi has been elected an ACI Fellow “in recognition of outstanding contributions to the American Concrete Institute and to concrete technology”. The position of ACI Fellow was established by ACI in 1973: “A Fellow shall be a person who has made outstanding contributions to the production or use of concrete materials, products, and structures in the areas of education, research, development, design, construction, or management.”

• Very good progress has been made on concrete rheology modeling using the NASA award of 1,000,000 cpu hours on Columbia, NASA’s 10,000 processor supercomputer. The rheology algorithm has successfully scaled to 1,000 processors and shows promise of being able to utilize even more processors. Realistic particle size distributions are able to be handled using the many processors available.

• The VCCTL software was upgraded from Version 6.0 to Version 7.0. The functionality has been greatly improved and the software has been made much easier to work with, more powerful, and much more like a real physical testing laboratory.

• Work on diffusion algorithms in HydratiCA has led to a derivation of approximate expressions for the forward and reverse rate constants of nonideal diffusion. These expressions provide a foundation, rooted in transition state theory, for calculating random walk probabilities in stochastic models of diffusion of ions in moderately dilute solutions. This work was published in the Journal of Physical Chemistry in 2007. (J.W. Bullard, “Approximate Rate Constants for Nonideal Diffusion and Their Application in a Stochastic Model,” J. Phys. Chem. A 111 (11): 2084-2092 (2007)). HydratiCA is by far the most advanced model of its kind in the world.

• Analytical procedures for tracking hydration kinetics using a new position-sensitive X-ray diffraction detector and sealed specimen cells was developed and shown to at least equal and in most cases exceed the quality of data taken at the synchrotron beam line at Brookhaven National Laboratory. This allows tracking of cement hydration in the lab, supplementing and eventually supplanting data gathered at Brookhaven on the synchrotron.

• An average of about 13,000+ users from 90+ countries accessed the Electronic Monograph per month, and several hundred pages of text and figures were added to the Monograph in FY07.

• The 18th annual ACBM/NIST Computer Modeling Workshop was held June 25-27, 2007. 34 people attended, from academia, government, and industry, with four guest lecturers from Northwestern University, Princeton, Texas A&M, and FHWA.

Related Projects

- Estimate economic impacts resulting from BFRL’s research in support of its Virtual Cement and Concrete Testing Laboratory (VCCTL).

- Processing of High-Performance Concrete: Mixing and Flow Properties

- VCCTL Cement Hydration Modeling

- Micro- and Macrostructural Characterization of High-Performance Concrete

- Simulation of the Performance and Service Life of High Performance Concrete

- Adaptive Concrete Technologies

- Doubling the Service Life of Concrete