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South Dakota Department of Transportation
Project Synopsis
SD2002-01


Title: Investigation of the Long Term Effects of Magnesium Chloride and other Concentrated Salt Solutions on Pavement and Structural Portland Cement Concrete
Project Researcher: Lawrence Sutter,
Project Manager: Dan Johnston
Research Period: 9/24/2002 - 5/31/2008
Status: Approved
Cost: $600,000.00

Problem Statement: Winter maintenance throughout the United States has undergone a tremendous change during the last decade with a strong shift in materials away from solid chemicals and salt-sand mixtures towards the use of liquid deicing chemicals. This move has been prompted by many factors including increasing public demand for serviceable, even bare pavements, environmental concerns with dust and a concerted effort to find ways to maintain acceptable road conditions while reducing the quantity of chemical being applied. The new emphasis on deicing/anti-icing as a primary strategy has resulted in a substantial increase in the use of concentrated chloride salt solutions both for prewetting and direct application to pavement surfaces. As familiarity and experience grow, more and more liquid chemical is being used with the assumption that there is no fundamental difference in effect using these liquids as there was with the prior use of solid sodium chloride. This may not be the case.

Magnesium chloride solution has gained wide acceptance as an important tool in numerous states' winter maintenance programs. Currently, it is being used for deicing, prewetting and anti-icing with great success. The volume of this material being applied annually is rapidly increasing as more maintenance units expand their capabilities. At the same time, the American Concrete Institute states in ACI 515.1R-79 "Magnesium chloride disintegrates concrete slowly" and F.M.Lea, in The Chemistry of Cement and Concrete (third edition, Chemical Publishing Company, New York, page 673), states "Solutions of magnesium chloride of 2% concentration and upwards produce a gradual diminution in the strength of portland cement mortars" and goes on to say "Very strong [about 30%] solutions destroy portland cement concrete." These views raise questions about the long term effects of applying 28-30 % solution of this chemical, or, indeed, any chemical deicer to bridge decks and PCC pavements, as well as the potential impact to highly permeable new concrete.

Calcium and sodium chloride are also being used as concentrated deicing brines, with unknown potential effects on concrete properties. Typical existing research involves testing 2%-4% solutions of deicer for scaling or other adverse effects. These tests assume rapid dilution of these chemicals, which may not be valid, especially where anti-icing is being employed. There is a need to conduct field investigations on concrete treated with liquid deicers over a number of years as well as laboratory research to determine the potential impact of various liquid deicers over the expected duration of treatment. There is also a need to determine whether strategies such as modified concrete mix design or application of sealants can offset any deleterious results.

This project is being conducted as Pooled Fund Study TPF-5(042) through the cooperation of the Federal Highway Administration and the financial support of California, Colorado, Idaho, Illinois, Iowa, Montana, Texas and Wyoming.



Findings:

Research Objectives:
1  To determine the long-term effects of concentrated solutions of magnesium, sodium and calcium chloride as well as CMA or other alternative liquid deicers on durable portland cement concrete.
2  To estimate the potential for reduction in performance and service life for pavements (jointed plain, reinforced and continuously reinforced) and structures subjected to various concentrated deicing brines.
3  To identify alternative protective or deicing/anti-icing strategies which minimize potential impacts to durable portland cement concrete while providing acceptable winter maintenance results.

Research Tasks:
1  Perform a literature search on the effects of chemical deicers on concrete as well as various winter maintenance strategies currently being employed using these materials.
2  Conduct a survey of states and Canadian provinces to determine current deicing/anti-icing practices, application strategies and concrete performance issues, after a panel review of the draft survey, to obtain suitable information for use in conductin
3  Select suitable locations for coring and extensive concrete analysis. Each participating state will provide a list of at least four potential experimental sites, including a control, for consideration at the meeting outlined in Task 4. Documentation
4  Meet with the technical panel two months after initiation of the project to discuss the project scope and finalize the list of coring locations and develop a sampling plan for each.
5  Examine field samples that will be obtained by the state DOT’s using appropriate test methods to determine concrete quality, permeability and any effects due to various deicers (estimated 108 cores).
6  Perform statistically valid laboratory testing designed to simulate the consequences of the gradual accumulation of various liquid deicers (concrete deterioration, corrosion) in concrete of various quality and composition (which may include cement ty
7  Assess the potential for modifying concrete construction practices and mix designs or else applying surface treatments to existing concrete to minimize any impact from the use of liquid deicers.
8  Estimate effects on concrete life and performance characteristics based on the utilization of different deicers and proposed mechanisms of deterioration with various concrete types using available deicer application strategies.
9  Develop life cycle cost analyses comparing current deicing/anti-icing procedures using each liquid deicer with any recommended alternative approaches.
10  Develop general guidelines for current practices which will insure minimal damage to concrete pavements and structures while allowing the ongoing application of appropriate liquid deicers.
11  Submit an interim report no later than twelve months after commencement of the research providing preliminary findings and recommendations.
12  Meet with the technical panel at the researcher’s facility to review the interim report and scope of work.
13  Prepare a final report and executive summary of the literature review, research methodology, findings, conclusions, guidelines and recommendations
14  Make an executive presentation to the research panel and provide each panel member with an MS PowerPoint version of the presentation after submission of the final report.
15  Make an executive presentation to the SDDOT Research Review Board summarizing the findings and conclusions.

Documents Available:
SD2002-01_Executive_Summary_Final.pdf
SD2002-01_Final_Report_Final.pdf
SD2002-01_Implementation_Guide_Final.pdf

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