Optimization of cement and fly ash particle sizes to produce sustainable concretes

Dale P. Bentz, Andrew S. Hansen, John M. Guynn
Cement and Concrete Composites, Volume 33, Issue 8, September 2011

Abstract

In the drive to produce more sustainable concretes, considerable emphasis has been placed on replacing cement in concrete mixtures with more sustainable materials, both from a raw materials cost and a CO2 footprint perspective. High volume fly ash concretes have been proposed as one potential approach for achieving substantial reductions in cement usage, but their usage is sometimes hampered by reduced early age strengths and dramatically increased setting times. One limitation of the current industry practice is that Portland cements are generally only optimized for their performance in a pure cement, as opposed to a blended cement, system. In this paper, a new approach of optimizing the particle sizes of the cement and fly ash for achieving desired performance in a blended product will be presented. By appropriately selecting the particle size distributions of cement and fly ash, equivalent 1 d and 28 d strengths may be achieved with about a 35% volumetric replacement of cement with fly ash, while maintaining the same volume fraction of water in the mixture, thus providing an actual 35% reduction in cement content.

Additional Information:

ENGINEERED CEMENT WITH HIGH SCM CONTENT

Background

Roman Cement, LLC has developed and patented a range of engineered cements that take the place of ordinary Portland cement (OPC) with the following benefits:

  • Lower material and energy costs

  • Green (reduced CO2 footprint)

  • Sustainable (lower energy consumption; greater use of waste materials)
  • More resistant to chemical degradation (e.g., ASR, sulfate attack, carbonation)

OPC is energy intensive and responsible for 5-7% of man-made CO2.  There is intense pressure to reduce energy consumed and CO2 emitted by cement manufacturers.

Roman Cement has developed patented engineered cements with high SCM content that can be used in place of OPC with the same or better performance.  It is “plug and play” because it can replace OPC one for one with little or no change in concrete mix design.  While fly ash is used, about 50% of concrete in the U.S. includes no fly ash though millions of tons continue to be discarded each year.  Roman Cement optimizes the Portland cement and SCM fractions to make them more compatible for use with each other, increasing SCM usage, reducing Portland cement usage, saving energy, cleaning up the environment, and yielding better concrete.


Validation of Roman Cement Technology

As described in the article, The National Institute of Standards and Technology (NIST) conducted rigorous testing of various engineered cements and identified several that equaled or exceeded the strength of 100% OPC at the same w/cm.  Some blends had essentially the same strength at 1-28 days as 100% OPC, while others exceeded the strength of 100% OPC at all ages, which provides flexibility to add additional fly ash or inert fillers and still maintain similar strength as 100% OPC.

Intellectual Property

Roman Cement owns U.S. Pat. Nos. 7,799,128 and 7,972,432, which were fast-tracked by the USPTO under the Green Technology Pilot Program, with equivalent patents pending in Australia, Brazil, Canada, China, Europe, India, Japan, South Korea, South Africa and Russia and other patents pending for improvements in cement chemistry, particle size optimization, blending techniques, and business methodologies.  The patent application for “second generation” Roman Cement, which improves upon the technology tested by NIST, was also fast-tracked under the Green Technology Pilot Program.

Who Invented “Roman Cement”?

“Roman Cement” engineered cement with high SCM content was jointly invented by John Guynn (B.A., M.S. Chemistry, JD) and Andrew Hansen (B.S. Chemistry, JD), chemists and patent attorneys with more than 25 combined years of technical and legal experience.  They invented Roman Cement to satisfy market need and fill glaring gaps in technology and IP that persist due to conservative thinking, stifled innovation, and market inertia.  Recent publications show that others have begun researching similar materials, but Roman Cement leads in IP development.

Cost Savings of Roman Cement

OPC costs substantially more than fly ash and other SCMs such as limestone.  Replacing Portland cement with less expensive SCMs reduces marginal cost of production.  Alternatively, blending Portland cement with SCM can greatly expand capacity of an existing cement plant with reduced capital expenditures (e.g., eliminating the need to build new kilns to increase clinker production).

Go to Journal

Check Also

Effective and accurate stiffness modeling of welded steel joints using metamodels based on mode shapes