Grantee Research Project Results
Final Report: Alkali-Activated Cement (AAC) as a Sustainable Building Material
EPA Grant Number: SU834759Title: Alkali-Activated Cement (AAC) as a Sustainable Building Material
Investigators: Barsoum, Michel , Moseson, Alexander J. , Crook, Abraham , Spencer, CJ
Institution: Drexel University
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2010 through August 14, 2012 (Extended to August 14, 2013)
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2010) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety , P3 Awards , Sustainable and Healthy Communities
Objective:
The purpose of this project is to research, develop, and apply AACs to actualize their potential benefits to people, prosperity, and the planet. This is pursued through three specific aims:
Aim 1: Research: Determine the relationships between chemical, microstructural, and performance properties of AACs
This is accomplished using various analytical techniques including microscopy, spectroscopy, mechanical testing, and statistical design of experiment. This aim is central to solving the challenges facing AACs.
Aim 2: Development: Investigate performance using key ASTM tests
Examples of such tests include time of set, strength, autogenous and drying shrinkage, freeze-thaw resistance, and three-point concrete beam bending. This aim is central to understanding the practical benefits and barriers to applications of AACs.
Aim 3: Application: Develop low-cost AACs for use in developing countries
AACs have been developed in response to the unique challenges and opportunities of Mumbai, India, as a high-quality yet affordable building material for to benefit slum dwellers.
Summary/Accomplishments (Outputs/Outcomes):
To summarize the effort over the entire project period required for the above, the project was the research focus of a postdoc, two full-time PhD students, two full-time masters students, and over a dozen part-time undergraduate students. It involved hundreds of design iterations, thousands of tests, samples from four continents, and literally tonnes of raw materials.
The data, findings, and outputs/outcomes of each specific aim are discussed in turn below, with respect to the measurable results and project schedule in our Phase II proposal.
Aim 1: Determine the relationships between chemical, microstructural, and performanceproperties of AACs
We have continued to advance publications that we believe prove beyond a reasonable doubt that: i) granular limestone is an active component in the alkali-activated system studied and ii) formulae with up to 68% limestone content and no OPC are competitive in performance with OPC, while reducing CO2and energy by up to 97%.
Progress has also been made on a detailed parametric life cycle assessment of alternative cements. Preliminary results show that the estimate of 97% CO2and energy savings for AACs is accurate under some circumstances, while factors such as transportation could eliminate any gains. The resulting publication should help to inform academic and industry on the claims made by alternative cement manufacturers, and the importance of life-cycle perspective in this field.
(http://hdl.handle.net/1860/3680) for example outcomes for this aim.
Aim 2: Investigate performance using key ASTM tests
Progress has been made towards passing the requirements of ASTM C1157, in part through the systematic testing of scores of formulations. It remains, however, to find a reliable way to simultaneously pass the requirements both for initial set-time and 1-day strength. The relocation of our lab space contributed to limiting the progress made.
We submitted a promising formulation for 3rd-party ASTM testing. The results showed both compressive strength and time-of-set lower than expected. It was determined that this was due in part to improper mixing on the part of the 3rd-party, but mostly because of an error in standard test procedure on the part of the researchers. Too little water was being used for mortar cube compression tests, which increased strength substantially, but was not within the requirements of the standard.
Shrinkage, time of set, and elastic modulus studies did not reach a stage of completion sufficient to warrant a refereed publication. This is because the co-investigator at Villanova University is no longer at that institution and did not continue the work; the budget balance allocated to Villanova was de-obligated, and the funds returned to Drexel University. A no-cost extension was issued by the EPA in part due to this.
Aim 3: Develop low-cost AACs for use in developing countries
This was the focus of the first reporting period, and there is thus little new to report in this period. One of the student leads, Alexander Moseson, was a Visiting Scholar for 6 months in 2010 at the Indian Institute of Technology (IIT), Mumbai. He remains in contact with his host there, professor D.N. Singh.
In 2010 - 2011, the research team was retained by the Mennonite Central Committee (MCC) of Bangladesh to investigate two types of alternative cementitious material: Sorel Cement and soilbased geopolymers. Both theoretical and empirical investigation was conducted, and a comprehensive report delivered.
Conclusions:
Our driving goal throughout has been to develop a commercially viable low-cost, low-CO2cement that passes ASTM C1157 and could be used as a direct replacement for OPC. This has proven more difficult than expected. Some of the reasons are technical, for example the need to accommodate feedstocks that change with source and time. Some are business, for example the reluctance of established companies to invest in technology that cannot be patented, requires regulatory approval that could take years, and the need to sell thousands of tons of the material in order to be attractive.
Other reasons cross both fields, centering on the difficulty of passing ASTM C1157. For example, the set-time requirement is on cement paste, which is almost never used as a final product (in contract with mortar, concrete, etc.). Similarly, the water requirement for mortar compression tests is determined by a drop table which measures "flow,"but this has little correlation to concrete workability. In fact, reduced water demand would be considered a positive as long as workability is maintained. These examples demonstrate the challenges of passing a standard which, while strictly on performance and not composition, is modeled very closely on Ordinary Portland Cement (OPC).
We remain convinced that AACs in general, and the high-limestone variety that we have developed in particular, hold great technical and commercial promise. It will take an order of magnitude more resources, and perhaps a more favorable commercial environment (such as created by a robust carbon market or tax) to realize their benefits. Until such time, the work will be put on hold.
Regardless, this grant has yielded substantial academic and broader impacts, and the researchers remain grateful for the support of the EPA.
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this projectSupplemental Keywords:
Alkali activated cement, Granulated blast-furnace slag, Mixture proportioning, Mechanical properties, Limestone, Design of experimentProgress and Final Reports:
Original AbstractP3 Phase I:
Alkali-Activated Slag Cements as a Sustainable Building Material | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.