A study of concrete mortar bars that incorporate reactive aggregates in the presence of airfield pavement deicer chemicals affirms that there is a correlation between the presence of deicers and an accelerated reaction similar to ASR (Reference IPRF Project 01-G-002-03-9, Potential for Acceleration of ASR In the Presence of Pavement Deicing Chemicals). The absence of reactivity in mortar bars prepared using innocuous aggregates has also been confirmed.
A study accomplished by the University of Wisconsin at Madison (Reference IPRF Project 01-G-002-01-4.2, Effects of Coarse Aggregate Clay Coatings on Concrete Performance) provides affirmation that clays disbursed in cement reduce compressive strength and increase shrinkage of concrete. The study also identified that the presence of clays in plastic concrete impacts hydration rates. But, ancillary discovery recognized that during the hydration phase, there were detectable spikes in the formation of Calcium Hydroxide and that dirty aggregates themselves are sources of alkaline chemicals. IPRF Project 03-9 identified that when a pavement deicer (Potassium Acetate) is introduced into a solution of Calcium Hydroxide there is a significant increase in the pore solution pH.
A by product of the work at the University of Wisconsin at Madison is a protocol which can be used in the laboratory to control the volume of the fine materials present on dirty aggregates that is dispersed into the water phase as a result of aggregate mixing and before cement is added. Studies of the dispersed materials in suspension at the concentrations determined from the disbursement protocol allowed for determination of properties of the cement.
Assuming that an excess amount of aggregate dust could result in increased shrinkage and particle swelling, it is possible that micro-fracturing of the concrete surface would also occur. This micro-cracking permits infiltration of airfield pavement deicing chemicals in the near surface of the concrete. The dispersed particles, being high in alkalinity, could possibly react with the deicer chemicals. The dispersed material could therefore be a variable in the early distress of pavement subject to airfield deicers.
This research is intended to investigate the durability of concrete because of the presence of dirty aggregates introduced into concrete mixes as aggregate coatings and establish reasonable limits on the quantity of deleterious materials in concrete mixes that will minimize the potential for durability problems. The following questions must be answered. Is there a relationship between dirty aggregates and the chemical reaction observed in some concretes that are subject to deicer applications? When limits are exceeded because of physical restraints (i.e., no water to wash mined aggregates) are there reasonable mitigation measures that could be implemented? What would the screening protocol be to determine if mitigation was necessary?
The primary objective of the research is to determine if the presence of deleterious materials, dispersed into concrete mortar from dirty aggregates, is a factor in the acceleration of distress observed in some airfield concrete pavement subjected to pavement deicer. For the purpose of this research it will be assumed that the deicer of interest is Potassium Acetate because that deicer is the most common deicer used by the airport.
1.1 Define how the dispersed materials, introduced as aggregate coatings, influence the ASR type of reaction described in the IPRF Report 01-G-002-03-9, Potential for Acceleration of ASR in the Presence of Pavement Deicing Chemicals.
1.2 Quantify the potential for deterioration of concrete with respect to durability when mineral fines are introduced as aggregate coating as compared to that deterioration caused by the same concrete in the presence of deicer, if the latter is true.
1.3 Determine how mineral fines affect micro-structure and hydration products in concrete with materials introduced as coating on dirty aggregates.
A secondary objective is to develop a matrix that defines those variables which impact the durability of concrete (including exposure to pavement deicers) when a reasonable quantity of clay and or mineral fines is present in concrete. The variables are to be assembled in a matrix which: (1) defines those variables that can be quantified and the impact on durability determined based upon empirical knowledge or research findings; (2) can be eliminated as influential in durability issues based upon a sensitivity analysis; and (3) can be defined based upon the resources available through this research.
If a positive association can be made between clays and/or mineral fines introduced to concrete mixes from dirty aggregate, what are reasonable limits on the quantity of deleterious material that can be allowed before mitigation is required. If mitigation is required, will lithium dosage mitigate the potential for durability problems? Are there other mitigation techniques that could be explored?
The final product will be an Innovative Pavement Research Foundation (IPRF) report that reports the results of the research. The report will define the apparent causal effect of distress mechanisms that are the result of a reaction between concrete that contain mineral fines which have been exposed to deicer chemicals. The report will include a recommended screening protocol for determining probable mitigation methods that will minimize the potential for the distress mechanisms related to durability. At the conclusion of the research there should be a document(s) that the engineer or constructor can read and there by gain an understanding of the problem and the probability for successful mitigation of the problem.
The final report will be provided to the IPRF in the form of two originals, in a camera ready format, including any artwork, graphics or photos. An electronic version of the final report in a format compatible with off-the-shelf desktop computer publication software will also be provided. The investigator will not be responsible for the reproduction and printing of the final document(s) but will assist with minor editing requirements generated by the printing and reproduction process.
The investigator is expected to develop sub-tasks that when completed will result in completion of the project within the time and budget available. It is not necessary that the proposal reflect the exact budget or the planned time. However, any deviation from the designated resources must be justified and clearly explained in the proposal. The following are the minimum tasks that are considered necessary to complete the project.
Task 1 – Literature Review and Information Gathering. Review existing literature. Provide a summary of any exacerbating variables or outstanding questions identified in previous research or any reported durability problems with concrete used as pavement that incorporated dirty aggregates or clays introduced as aggregate coatings. Identify any perceived shortfalls between the results of the literature search and the objectives of this project. The literature search will result in the development of a matrix that describes the variables identified that impact durability. The matrix will summarize the nature of the variables for which there is no conclusive evidence relative to the impact of clay on the durability of concrete. The matrix will be a submittal for review by the Technical Panel.
Task 2 – Document a Research Plan and Schedule. Develop a plan for doing the research. The anticipated protocol to be employed in the research will be identified. The plan must include a petrographic evaluation of concrete cores, extracted and provided by the IPRF, from a minimum of two airports. There will be approximately three cores from each airport. The research plan will include a description of the protocols that will be used to document the material properties used in the concrete from which cores were extracted. The submittal of the research plan to the IPRF Technical Panel is designated as the 20% review point of the research.
A 20% on-board review will be accomplished. The investigator will not proceed to Task 3 without the written approval of the IPRF. An on-board review must be scheduled at least 30 days prior to the actual meeting. Documents that are prepared for technical panel review must be provided at least 30 days prior to the meeting. The location of the meeting will be coordinated with the IPRF. The Principal Investigator will be responsible for documenting the comments of IPRF Technical Panel members and the disposition of their comments.
Task 3 –Validate and Refine the Protocol Described in Task 2. The research team will accomplish the petrographic evaluation of the concrete cores provided by the IPRF and describe the materials used for the mix. The IPRF will work with the research team to obtain samples of aggregates representative of those used to construct the concretes. If dirty aggregates are present, attempt to correlate the concentrations of deleterious materials that would be present in the water phase with the amount of mineral fines coating on aggregates. Determine which concentrations of micro-fines present in the concretes.
Task 4 –Durability Study. Prepare test specimens using dirty aggregates of different origins. Determine if there is a unique difference between introducing mineral fines as coatings on aggregates and mineral fines only in the water phase for mortar mixing. Perform durability studies using Potassium Acetate. Determine the nature of any adverse reaction that results in excessive expansion or deterioration of the mortars. Develop correlations of mortar cube (or bars) distress development as a result of exposure to Potassium Acetate. Accomplish that testing that will complete the matrix defined from Task 1.
As a part of the proposal, the Principal Investigator (PI) will designate the approximate time after Task 4 begins that a report of the initial findings will be available. The summary of initial findings is defined as the 40% review point of the research. The report will include the summary of observations of the initial research and the lessons learned through the date of the report. The report should be prepared and submitted at a time in the laboratory process that corrections to the test plan or modifications of test protocols would be deemed appropriate.
A 40% on-board review will be accomplished. The review will be a meeting between the PI and the IPRF Technical Panel. The initial findings report will be provided to the technical panel at least 30 days prior to the meeting. The investigator is expected to present to the technical panel discussion items that will result in policy decisions for critical elements that impact the future of the research. Additional research may be needed to respond to questions that are developed as a result of the on-board review. The Technical Panel will determine, based upon the results presented if the primary research will go forward. The work on Task 7 will not begin without approval from the IPRF. The location of the meeting will be coordinated with the IPRF. The investigator is responsible for documenting the comments of IPRF technical panel members and the disposition of each comment.
Task 5 – Perform Analysis of Data. Define a hypothesis as to the impact that dirty aggregates have with respect to the durability of concrete in the presence of airfield pavement deicer. Establish concepts for “safe” limits of deleterious materials and define when mitigation is required. Define what form of mitigation might be appropriate. Define a roadmap that could be used to define future research to explore the effectiveness of different mitigation strategies.
Task 6 – Provide a Written Summary to the IPRF on the results of Tasks 4 and 5. Prepare a brief report that provides a summary of the results of Task 4 and 5. Explain any significant deviation from expected results. Make a statement as to the deleterious materials content limits described in ASTM C-33 with respect to clays.
A 60% on-board review is an option. The review will be a meeting between the PI and the IPRF Technical Panel. The initial findings report will be provided to the technical panel at least 30 days prior to the meeting. The investigator is expected to present to the technical panel discussion items that will result in policy decisions for critical elements that impact the future of the research. Additional research may be needed to respond to questions that are developed as a result of the on-board review. The Technical Panel will determine, based upon the results presented if the primary research will go forward. The work on Task 7 will not begin without approval from the IPRF. The location of the meeting will be coordinated with the IPRF. The investigator is responsible for documenting the comments of IPRF technical panel members and the disposition of each comment.
Task 7 – Prepare Draft Final Report. Make corrections to the 60% report review and perform additional validation testing as directed by the IPRF based upon the results observed in Task 5. Include in the report all artwork, graphical presentations, format, etc. The document shall be in a form that for all intent is complete with the exception of final comments made by the Technical Panel. The submittal of the advanced final report is designated as the 90% review point of the research project.
A 90% desk top review will be accomplished. The advanced final report will be submitted to the IPRF Technical Panel for review. The Technical Panel will have 30-days to perform a desk top review and comment on the report. The report will include a summary of the results of testing and recommendations for the research plan that should be followed for mitigation of problems that are discovered as a result of the research. The investigator is responsible for documenting the comments of IPRF Technical Panel members and the disposition of comments made on the report.
Task 8 – Final Report. Make corrections to the 90% document and submit the final documents to the IPRF. Assist the IPRF with publication related editing.
- A brief summary of the literature search, the matrix of durability issues related to clay in concrete, the research plan and the time schedule for doing the work. Submit 8 copies. This is defined as the 20% level of completion.
- The 40% on-board review will be accomplished approximately 30-days after submittal of an interim report. The draft report (8 copies) will include a summary of all research completed to date.
- The 60% on-board review will be an option to be exercised by the Technical Panel and accomplished approximately 30-days after submittal of an interim report. The report (8 copies) will include a summary of all research completed to date.
- Advanced final report submittal (8 copies) for 90% review.
- A final report (an IPRF Report), that includes recommendations for the research and study of probable mitigating methods, with all artwork, graphics, tables, pictures, documentation, etc. ready for reproduction and distribution. The report will be submitted in two original documents and one on electronic media.
- Provide a brief summary of the qualifications of the laboratory and the equipment intended to be used for this research. Include this in the qualifications portion of the proposal.
- Research Team Members and Qualifications.
2.1 The Principal Investigator (PI) will have a working knowledge of concrete mixture proportioning for use in airport pavements and has demonstrated experience in the differentiation of construction related and material distress.
2.2 The research team will include a petrographer qualified with relevant experience. The petrographer, as a part of the proposal, will describe the approach to be used to catalog the materials that can be identified from the concrete cores.
2.3 The research team will include having access to an individual experienced in clay minerology who understands cement chemistry and has specific expertise in the chemical and engineering properties of concrete.
- The research team will use a Potassium Acetate as supplied by a manufacturer for use on an airfield pavement as the “pavement deicer.”
- The PI will be responsible for the preparation of quarterly reports that describe the progress of the research effort. Reports are due in the offices of the IPRF on the last day of the fiscal year quarter. The reports will be limited to two pages in a format specified by the IPRF. The first page will be a word document describing the progress of the work. The second page will provide a summary of the estimated costs versus the costs incurred to the report date.
After the technical panel completes the evaluation of proposals, each of the proposals will be rank ordered. The organization, group, or individual that is ranked as the first and second choice for the recommendation to award may be asked to participate in a telephone interview. The Principal Investigator, and one other person, representing the entity ranked first and second choice by the technical panel may be asked to participate in the interview to discuss the project details, goals, and objectives. The interview will occur within a 45-day window subsequent to the proposal submittal deadline.
IPRF PROCEDURAL GUIDANCE:
Persons preparing proposals are urged to review the following documents to be sure that there is a full understanding of IPRF procedures and requirements. Proposals must be prepared in the format specified in the instruction documents. The proposal will be submitted as one (1) original and 8 copies.
documents required to aide in the preparation of the proposal
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AVAILABLE: Not to Exceed $315,000
TIME: Not to exceed 28 Months
DIRECTOR: Mr. Jim Lafrenz, P.E., (785) 742-6900, (firstname.lastname@example.org)
NOTICE TO PROCEED DATE: February 12, 2007
DUE DATE: December 15, 2006 not later than 4:00 P.M. (Central Time)
Proposals will be delivered to:
Innovative Pavement Research Foundation
Cooperative Programs Office, Attn: Jim Lafrenz
201 Shawnee Street
Hiawatha, KS 66434
FAX: (785) 742-6908