KLK580 Concrete Performance in Aggressive Salt and Deicing Environments

ITD Research Project 262; Task Order Number UI-17-02

Principal Investigators

• Ahmed Ibrahim
• Fouad Bayomy
• Somayeh Nassiri (WSU)

ITD Project Manager

• Clint Hoops

FHWA Project Advisor

• Kyle Holman

Student Researchers

• —

Research Problem Statement

Concrete in barrier rails, parapets, barriers, and bridge decks throughout the State of Idaho are exposed to deicing chemicals and salt brine. As such, signs of durability damage have manifested in some of the concrete infrastructure. Recent studies have shown that depending on the concrete mixture, deicing chemicals can chemically react with the paste and produce different forms of salt or Calcium Oxychloride in the concrete. This chemical transformation has been shown to induce micro damage in the concrete. In addition, another deterioration mechanism develops in the concrete (or aggregate) as a result to freeze-thaw (F-T) cycling during the winter season. At a certain level of saturation, freezing of water forms internal osmotic pressure, which tends to damage the paste, initiate cracks and lead to concrete spalling problems.

Damage due to both mechanisms result in the development of durability cracking in the concrete, which increases its permeability and facilitates the migration of damaging chloride ions to the embedded reinforcing steel level,. Moisture and the detrimental ions cause corrosion of the reinforcing steel and ultimately result in the failure of concrete members. Replacement of concrete members in highway applications is not only costly for the highway agencies but can also impose significant delays to the road users., Idaho Transportation Department's (ITD)'s specifications follow industry practices developed years ago. However, concrete technology has evolved and practiced have been developed that produce more durable concrete. This research is aimed at enabling ITD to change or modify the current specifications to improve concrete durability in aggressive environments.

The negative effects of deicers on metals and concrete were investigated both in the laboratory and in the field in various research projects that have been conducted through state DOT's pool funding. Those studies investigated the effect of deicer scaling resistance of concrete mixtures (Taylor et al. 2012), and the evaluation of alternative de-icing and deicing compounds using sodium and magnesium chlorides (Shi et al. 2009, and Caires et al. 2006) and many other reports that can be found in the literature. The goal from the proposed study is to build on the results and recommendations of previous studies trying to increase the durability of ITD concrete mixtures against winter maintenance and deicers applications.

Project Objectives

Deicing chemicals can cause concrete to deteriorate as the result of physical and chemical effects as explained above. The two broad objectives of the proposed work are to:

1. Evaluate current ITD concrete mixtures' durability against F-T and wetting-drying (W-D) exposure conditions. The proposed experimental study will focus on the evaluation of long-term mechanical degradation due to exposure to F-T cycling, W-D cycles (mass loss, scaling) and chemical (new salt formation) properties to determine the performance of existing mixes (paste and concrete) used in the State of Idaho using various deicer chemicals.
2. Recommend strategies for improved durability of ITD mixtures. The study will investigate:

• Whether the addition of certain amounts of Supplementary Cementitious Materials (SCMs) to the current concrete mixture designs is necessary to alleviate the prevalent durability issues.
• Also, the affect of curing and potentially sealing or coating methods on reducing the permeability and hence vulnerability to durability problems will be investigated.
• Other solutions, such as air entraining admixtures; amount and type will also be considered.
• Finally, potential alternative winter maintenance practices in terms of salt brine, and other chemical deicer applications to reduce potential damage to concrete elements will be reviewed.

A detailed description of the project tasks is provided as follows.

Project Tasks

To achieve the aforementioned objectives, the research is planned over the following tasks:

Task 1: Literature Survey and Survey of Practice (U of I)

Identify the extent and location of concrete durability problems caused by various types of deicers, F-T and W-D cycles exposures. The research team will focus on collecting information and data regarding premature durability distresses observed in various regions of the state. The research team already has a knowledge of the concrete pavement mixtures currently in use in all districts  from the active RP253 (Portland Cement Concrete Material Characterization for Pavement ME Design Implementation in Idaho). To complete this knowledge, a survey will be designed to collect concrete mixture design information used for other applications, i.e. bridge decks, barriers, and others,. The districts' winter maintenance practices in terms of salt or chemical deicer applications will also be gathered as a part of the survey. The survey will be conducted in cooperation with the districts' material engineers. At the same time, a survey of literature will also be performed to gather information on how other states have dealt with concrete performance issues in aggressive environments. This task shall enable the team to identify the specifics of the mixtures and the deicer types that lead to premature distresses and durability problems in concrete barriers, bridge decks, and pavements in Idaho.

Deliverable 1

Deliverable of this task will be a summary of the literature review including any work-related from previous state DOTs, and a survey of practice from ITD districts (Deliverable 1 on the Gantt chart). This summary will include a list of different deicing practices and concrete mixtures used in barriers, bridge decks, and pavements in Idaho.

Task 2: Field Program (U of I and WSU)

Based on the results of the survey (Task 1), site visits may be performed by the research team to evaluate the existing problems. Further, the team may request core samples that have apparent signs of distresses to be extracted and sent tot he research team for testing.

Deliverable 2

Deliverable for this task will be a short report identifying the locations of extracted core samples and the associated problems observed from the field visits and discussions with the field engineers. The report will be submitted to ITD (Deliverable 2 on the Gantt chart).

Task 3: Laboratory Experimental Design and Execution (U of I and WSU)

Develop an experimental plan to evaluate durability of ITD's current concrete mixtures under a set of laboratory testing to simulate the prevailing harsh environment. Based on the information gathered in Tasks 1 and 2, the number of mixtures required for the study will be established. This Task is subdivided into three subtasks as shown in the Gantt chart. U of I and WSU already has batched, cast, and tested five ITD mixtures and is in the process of acquiring materials for another two mixtures from ITD districts as part of RP253. These seven mixtures will be included in the durability experiments in this project. Additionally, mixture designs for other applications, such as barriers and bridge decks as identified in Task 1 will be included in the experimental program. A laboratory experimental plan will be designed and finalized in consultation with ITD project manager and Technical Advisory Committee (TAC). The plan will include various deicing types, and solutions concentrations, to be used with all the concrete mixtures through F-T and W-D cycling exposures.

WSU will mix and cast the extra required specimens from all the identified mixtures for the durability tests. This experiment will focus on evaluating the ITD mixtures in the current state. As part of these experiments, the mixtures that shoe signs of durability issues will be identified for further testing and modification in a second set of experiments. It is expected that the first round of tests will at minimum include the following:

• Freeze-thaw durability, combined with mass loss and relative dynamic modulus of elasticity at N cycles (ASTM C666) (WSU): a minimum of three 3 by 3 by 11 inch prisms for each mix.
• Entrained air, slump, and 28-day compressive strength: these tests have already been conducted on ITD paving mixtures as part of RP253. Any new mixtures added in this project will be tested for fresh properties as well as 28-day compressive strength (WSU)
• Super Air Meter (ASTM C231) will be used to determine both total air content and air void spacing of fresh concrete specimens for all mixtures (WSU)
• Resistance against deicing scaling (ASTM C672) (U of I), a minimum of one 72 in 2- and 3-inch depth slabs for mixture design and for different deicing agents and concentrations. 
• Concrete wetting-drying (W-D) and temperature change (U of I). A minimum of three mortar cubes 2" by 2" by 2" and three concrete prisms 3 by 3 by 11 inch for each mix. Samples will be used to evaluate internal frost damage under low and high concentrations of deicer solutions, surface scaling and moisture uptake of all concrete mixes on duplicate specimens to each deicer type.
• Concrete surface resistivity will be measured on 4 by 8 in cylinders 28, 90, 150-day age. The surface resistivity measurement will be used to evaluate the ion penetrability of the ITD mixtures based on the criteria in ASTM 1202. Formation factor (FF) will also be estimated and will be evaluated for use as a quality control index (U of I).

Table 1 describes the anticipated number of specimens per mixture associated with each test for with each deicer. The number of mixtures depends on the number of durability issues in each district across the state.

Deliverable 3

Deliverable for this task will be a detailed laboratory experimental plan submitted to ITD in the form of a report (Deliverable 3 on the Gantt chart).

Deliverable 4

Deliverable for this task will be a short report on the mixing procedure and sample preparations submitted to ITD (Deliverable 4 on the Gantt chart).

Deliverable 5

Deliverable for this task will be a detailed report submitted to ITD with all testing results from Task 3 (Deliverable 5 on Gantt chart).

Task 4: Testing of Alternative Mixes and Development of Recommendations (U of I and WSU)

The mixture designs identified as problematic will be further tested under this task. Various factors that may have caused the durability issues will be investigated. The mixtures will be reproduced in a try and error basis to produce new mixtures with reduced durability issues. The modified mixtures will be tested for (F-T, W-D, and compressive strength as described in Task 3.

The potential factors investigated in the new set of experiments are expected to include:

• Entrained air content
• Various content and types of SCM
• Reduced w/cm
• Potential application of sealant/coating on concrete surface  
• Concrete strength

Deliverable 6

The recommendations from Task 4 will be submitted to ITD as a report with a detailed development plan for ITD modified concrete mixtures.

Deliverable 7

A report with the new mixtures, testing, and results will be submitted to ITD.

Task 5: Final Report (U of I & WSU)

This task is sub-divided into five subtasks as detailed in the Gantt chart. A draft report will be edited by a professional editor and reviewed by an external expert. The edited and reviewed draft report will be submitted to TAC for comments before submission of the final report. WSU and U of I will cooperate on this task.

Deliverable 8:

Deliverable for this task is the draft of the final report as described tasks in the schedule (Deliverables 6 & 7 on the Gantt chart). A draft report will be edited by a professional editor and reviewed by an external expert. The edited and reviewed draft report will be submitted to ITD for comments before submission of the final report as described in steps (a though g) in the Gantt chart.

Deliverable 9

A final report will be submitted to ITD after receiving all the comments from the external reviewer and from the TAC members.

Project Communication Schedule

Monthly progress reports as well as the deliverables will be submitted to ITD. Frequent conference calls - at least quarterly - will be arranged between the PIs and the project technical committee. Meeting minutes will be submitted to the ITD Project Manager and Research Program Manager.

Needs and Requirements

Upon the start of the project, ITD will assist the research team in identifying the locations of durability problems, mixes and type of deicers used at these locations. Additional mixtures for testing, if identified will be provided to the team fir mixing and testing. ITD will deliver the supplies and materials to WSU laboratory. ITD will lend a SAM and a surface resistivity meter to the research team for the period of the project.

Required Outputs/Deliverables

A final report including all the test results, analysis of the obtained data, and recommendations to be implemented in the ITD material design manual will be developed as a result of this project. A presentation to ITD summarizing the findings of the study is another output of this project. Deliverables for this study are:

• Deliverable 1: A summary of the literature review and a survey of practice from ITD districts and that will be with the coordination of the project manager.
• Deliverable 2: A report identifying the locations of extracted core samples and the associated problems observed from the field visits.
• Deliverable 3: Detailed laboratory experimental plan and material procurement.
• Deliverable 4: A report on mixing and sample preparations
• Deliverable 5: A report with the detailed results from Task 3.
• Deliverable 6: Recommendations for ITD modified concrete mixtures.
• Deliverable 7: A report and data files of the obtained results.
• Deliverable 8: Draft final report for ITD review.
• Deliverable 9: Final Report
• The final report shall address the ITD comments on the draft report as well as comments from the external reviewer.

Implementation

Implementation will be facilitated through a presentation to ITD concrete material engineers. The research results will fill in the gaps in deterioration of concrete rails/elements under deicer applications during winter time. Recommended strategies for more durable concrete mixes will be submitted to ITD for implementation. The Project Sponsor, Project Manager, and TAC members will meet with the researchers to discuss the study recommendations as part of the report review process. The researchers will assist the ITD Project Sponsor, Project Manager, and Technical Advisory Committee in developing a plan to implement study recommendations as appropriate. The plan will identify the steps needed to implement recommendations requiring action, a schedule for implementation activities, and the individuals responsible for specific implementation steps.

Expected Outcomes/Savings to ITD

The main outcome of this project is the development of concrete mixes with new ingredients for chemical attack protection and provide savings to ITD as follows:

• The results of the proposed project will demonstrate better performing concrete mixes or curing/coating procedures that could be specified to assure ITD gets the expected life from concrete members in aggressive salt environment reducing costs and impacts to the traveling public.
• The outcomes of this project are anticipated to improve the economics of bridge deck and concrete rails/barriers construction, which in turn will improve the safety and mobility of the traveling public through reduced cost to ITD. The recommendations from this project are expected to be practical, innovative, and efficient. 
• Cost savings — longer life will produce lower equivalent uniform annual cost. Mobility will also be increased as delays associated with repair and replacement of the concrete barriers, parapets, and bridge decks are reduced.

Monthly Progress Reports (ITD 771) and Task Progress Charts

Project status

Active

Draft report

Due September 15, 2018

Final report

Due December 31, 2018

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