Concrete Repair Best Practices: A Series of Case Studies

Concrete pavement restoration (CPR) techniques have gained greater national significance as DOT agencies attempt to further extend infrastructure service lives prior to required major rehabilitation or reconstruction.  Various publications have documented design procedures and materials for CPR techniques, but less has been written about best practices for their construction, based on information from contractor and DOT agency practitioners.  This report consolidates best practice case studies for six CPR techniques: cross-stitching, dowel bar retrofit, diamond grinding, full depth repair, partial depth repair and slab stabilization.  Technical briefs for each CPR case study have also been written to accompany the main report. They have been separately published.

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View Technical Brief #1 Cross-Stitching

View Technical Brief #2 Dowel Bar Retrofit

View Technical Brief #3 Diamond Grinding

View Technical Brief #4 Full Depth Repair

View Technical Brief #5 Partial Depth Repair

View Technical Brief #6 Slab Stabilization

Report number: cmr17-013
Published: November 2017
Project number: TR201618
Author: Michael Darter
Performing organization: Applied Research Associates, Inc.

A Report Card from Missourians - 2017

Abstract: Overall statewide satisfaction with MoDOT and additional feedback about MoDOT’s operations was obtained from a representative sample of the general adult public in Missouri. A professional calling center was engaged to obtain a diverse sample across Missouri. Specific minimums were given, such as 500 responses per district, with gender and age-range targets for each county in Missouri. 3,502 completed responses were obtained between June 26, 2017 and July 31, 2017. With the exception of a few questions (e.g., demographics), all statewide results presented in this document are weighted results. The data was weighted in accordance with the true distribution of the regional population in terms of geographic (county), gender, and age distributions using the most recent (2010) US government census information available. Following past practice, all district measures presented in this document are unweighted. With a minimum of 500 responses per district, the district measures have a 95% level of confidence with a precision (margin of error) of +/- 4.4%. The statewide results for the stratified-random sample of 3,502 Missourians have a 95% level of confidence with a precision of +/- 1.66%.

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Report number: cmr17-011
Published: November 2017
Project number: TR201522
Author: Lance Gentry
Performing organization: Heartland Market Research LLC

Cold Temperature Creep Compliance and Strength of Missouri Hot Mix Asphalt (HMA) Mixtures Using Indirect Tensile Test

For the second time in about 10 years, MoDOT has performed the local calibration of the mechanistic-empirical pavement design guide software, now designated as AASHTOWare Pavement ME Design. Cold-temperature creep compliance and tensile strength of hot mix asphalt (HMA) are the two inputs to the thermal cracking module within the software and are required for local calibration. The test protocol used for this work is American Association of State Highway and Transportation Officials (AASHTO) test method T 322, “Standard Method of Test for Determining the Creep Compliance and Strength of Hot Mix Asphalt (HMA) Using the Indirect Tensile Test Device.”

MoDOT-supplied materials were a) 18 different sets of the top lifts (layers) separated from six inch diameter pavement cores, and b) 54 boxes of 150 mm diameter gyratory-compacted specimens (GCSs). The 54 boxes of GCSs were produced from 27 different plant-produced mixes compacted to two levels of air voids per mix. Creep testing was performed at 0, -10, and -20°C (32, 14, and -4°F, respectively) and tensile strength testing was performed at -10°C. Poisson’s ratio was estimated from the creep testing results.

With a few exceptions, expected trends of increasing creep compliance with increasing temperature, and decreasing tensile strength with increasing air voids were confirmed during top-lift core and GCS-derived specimen testing. With a couple of exceptions, GCS-derived specimen testing resulted in the expected trend of increasing creep compliance with increasing air voids, at all temperatures. Although they are not required for local calibration of the thermal cracking module, estimated Poisson’s ratio values were reported but did not always follow expected trends (e.g. maximum value of 0.5), especially during the top-lift core testing.

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Report number: cmr17-014
Published: October 2017
Project number: TR201713
Author(s): Stephen Michael Lusher
Performing organization: Missouri University of Science and Technology

Performance of Fiber-Reinforced Self-Consolidating Concrete for Repair of Bridge Sub-Structures and Fiber-Reinforced Super-Workable Concrete for Infrastructure Construction

The proposed research investigates the combined use of self-consolidating concrete (SCC) and fibers reinforcements to develop a novel repair material, fiber-reinforced self-consolidating concrete (FR-SCC) that can be used for the rehabilitation and strengthening of existing structures. Furthermore, the feasibility of using super workable concrete (SWC) reinforced with different types of fibers for new structural cast-in-place applications is investigated. The use of SCC matrix can greatly enhance the workability of fibrous mixtures along with incorporation of greater volume of fibers. SWC is a new type of flowable concrete with lower workability than SCC. Containing lower binder content can be more cost effective than SCC. SWC requires some mechanical consolidation energy to ensure proper filling of the formwork. Eight types of fibers, including a propylene synthetic fiber, five steel fibers and a hybrid steel and polypropylene synthetic fiber were investigated. Fibers were incorporated at a volume of 0.5% in FR-SCC and at 0.5% and 0.75% in FR-SWC. Two types of expansive agents (EA), Type G and Type K, were added to both concrete types to reduce shrinkage and enhance resistance to restrained shrinkage cracking. The optimized mixtures exhibited high workability, mechanical properties, and freeze/thaw durability.  The incorporation of fibers with 4% Type-G EA in FR-SCC increased the 56-day flexural strength by up to 32%, and flexural toughness up to 23 times. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers (ST1) in FR-SCC made with 4% Type-G EA increased the elapsed time to cracking determined from restrained shrinkage ring test from 16 to 20 days compared to FR-SCC made with 0.5% ST1 fibers without EA. The use of ST1 steel fibers and 4% Type-G EA decreased the 1-year drying shrinkage by 48% compared to the reference SCC mixture without any fibers and expansive agent. In case of FR-SWC, the decrease in shrinkage was 37% compared to SWC.

In addition, 20 monolithic full-scale beams were cast using different types of concrete, including conventional vibrated concrete (CVC), fiber-reinforced conventional vibrated concrete (FR-CVC), SCC, FR-SCC, SWC and FR-SWC. Twelve reinforced concrete beams were cast using CVC to fill two thirds of the beam height. They were then filled with five different types of FR-SCC and SCC to simulate beam repair in the tension zone. Findings indicated that macro fibers can be used with FR-SCC designated for repair with fiber length ≤ 2 in. (50 mm) up to 0.5% fiber volume. Macro fibers can be used with FR-SWC designated for construction with fiber length ≤ 2.6 in. (65 mm) up to 0.75% fiber volume. Fibers had great impact on structural performance of the full-scale monolithic beams. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers combined with 0.5 in. (13-mm) straight steel fibers at ratio 4 to1 (STST) with 4% Type-G EA increased toughness of FR-SWC beams by 95% compared to SWC beams and by 86% in case of 0.75% 5D fibers. Repair using FR-SCC increased the flexural capacity of the beam by 6% and the toughness by 110% in case of using 0.5% ST1 fibers with 4% Type-G EA.

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Report number: cmr17-012
Published: September 2017
Project number: TR201505
Author(s): Kamal H. Khayat and Ahmed Abdelrazik
Performing organization: Missouri University of Science and Technology

Evaluation of Automated Flagger Assistance Devices

Flagger safety is an important issue in work zones due to the proximity of the flagger to traffic. Some strategies for improving flagger safety include slowing down approaching vehicles or removing flaggers from the immediate vicinity of traffic. The Automated Flagger Assistance Device (AFAD) is a system that can potentially accomplish both of the aforementioned strategies. In order to validate the effectiveness of AFADs in highway work zones, field testing was performed using an AFAD with a Changeable Message Sign (CMS) on a 2-lane work zone in Missouri. The field study found that AFADs helped to lower approach speeds and encouraged vehicles to stop farther behind the AFAD than a traditional flagger. In addition, a driver intercept survey found that the AFAD was viewed favorably by the general public. These field results found that AFADs are more effective than human flaggers, and drivers prefer AFADs over human flaggers.

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Report number: cmr17-010
Published: August 2017
Project number: TR201717
Author(s): Henry Brown, Carlos Sun, Siyang Zhang and Zhu Qing
Performing organization: University of Missouri-Columbia

Evaluation of Work Zone Split Traffic Symbol Sign

Effective signage that is easy to understand facilitates safe driving through a work zone. While the guidance for work zone signage in the Manual on Uniform Traffic Control Devices (MUTCD) is suitable for many conditions, there may be instances where alternative signage may be more effective at enhancing safety. This project evaluated the use of alternative signage for closure of a middle lane in a freeway work zone on a bridge rehabilitation project on I-170 in St. Louis, Missouri. The alternative signage displays the lane arrangement in a single sign while the MUTCD signage shows the movements to the left and the right sides of the work area on separate signs. The evaluation of the alternative signage included stakeholder and driver surveys, operational and safety analyses, and the collection and analysis of field videos to assess driver behavior. The analysis of field videos showed that drivers may have adapted to the alternative signs as the rate of lane changes decreased between the early and late periods of construction. Stakeholder interviews found that personnel from MoDOT and the contractor generally thought that the alternative sign communicated information more clearly but had mixed opinions on whether the use of the sign improved safety. Drivers did not express any concerns regarding the use of the alternative sign through a website that collects feedback on MoDOT work zones. A review of crash data found that crash patterns during the work zone period were similar to the crash patterns before the work zone was in place, and the use of the alternative sign did not appear to be a contributing factor in any work zone crashes. Analysis of RITIS traffic data found that the use of the alternative sign did not have an impact on travel times in the vicinity of the work zone. Overall, the evaluation found that the alternative sign communicates information clearly and does not cause any adverse impacts to work zone safety and operations.

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Report number: cmr17-009
Published: August 2017
Project number: TR201613
Author(s): Praveen Edara (PI), Carlos Sun (co-PI), Henry Brown (co-PI), University of Missouri-Columbia and Shawn Leight, CBB

Performing organization: University of Missouri-Columbia

Economical and Crack-Free High-Performance Concrete for Pavement and Transportation Infrastructure Construction

The main objective of this research is to develop and validate the behavior of a new class of environmentally friendly and cost-effective high-performance concrete (HPC) referred to herein as Eco-HPC. The proposed project aimed at developing two classes of Eco-HPC for the following applications: (i) HPC for pavement construction (Eco-Pave-Crete); and (ii) HPC for bridge infrastructure construction (Eco-Bridge-Crete). The binder contents for these construction materials were limited to 320 kg/m³ (540 lb/yd³) and 350 kg/m³ (590 lb/yd³), respectively, in order to reduce paste content, cost, CO2 emissions, and shrinkage. Both Eco-HPC types were optimized to develop high resistance to shrinkage cracking as well as to secure high durability. Given the relatively low binder content, the binder composition and aggregate proportion were optimized based on the packing density approach to reduce the paste required to the fill the voids among aggregate particles. The optimized concrete mixtures exhibited low autogenous and drying shrinkage given the low paste content and use of various shrinkage mitigating strategies. Such strategies included the use of CaO-based expansive agent (EX), saturated lightweight sand (LWS), as well as synthetic or recycled steel fibers. Proper substitution of cement by supplementary cementitious materials (SCMs) resulted in greater packing density of solid particles, lower water/superplasticizer demand, and improved rheological and hardened properties of cement-based materials. A statistical mix design method was proposed and was shown to be effective in optimizing the aggregate proportioning to achieve maximum packing density. The synergistic effect between EX with LWS resulted in lower autogenous and drying shrinkage. For a given fiber content, the use of steel fibers recovered from waste tires had twice the flexural toughness of similar mixture with synthetic fibers. The optimized Eco-HPC mixtures had lower drying shrinkage of 300 μstrain after 250 days. The risk of restrained shrinkage cracking was found to be low for the optimized concrete mixtures (no cracking even after 55 days of testing). The results of structural performance of large-scale reinforced concrete beams indicated that the optimized Eco-Bridge-Crete containing ternary combination of 35% fly ash and 20% slag replacements and recycled steel fibers developed significantly higher flexural toughness compared to the MoDOT reference mixture used for bridge infrastructure applications.

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Report number: cmr17-007
Published: May 2017
Project number: TR201503
Author(s): Dr. Kamal H. Khayat (principal investigator) and Iman Mehdipour (PhD Candidate student)
Performing organization: Missouri University of Science and Technology

High-Volume Recycled Materials for Sustainable Pavement Construction

The main objective of this research is to evaluate the feasibility of using high-volume recycled materials for concrete production in rigid pavement. The goal was to replace 50% of the solids with recycled materials and industrial by-products. The performance of concrete mixtures made with different fine and coarse recycled concrete aggregate (RCA) contents and binder types was investigated. Both single-layer rigid pavement and two-lift concrete pavement (2LCP) were considered. The optimized mixtures developed 91-d compressive strength results from 5,900 to 8,600 psi. Flexural strength was mostly higher than 600 psi at 28 d. The modulus of elasticity ranged from 4.7 to 6.7 ksi at 56 d. Using the optimized binder incorporating 35% Class C fly ash and 15% slag reduced the 150-d drying shrinkage to values less than 350 to 500 με. However, an increase in fine RCA content from 15% to 40% resulted in increased shrinkage values (up to 650 με). The optimized mixtures exhibited frost durability factor higher than 88%. De-icing salt scaling ratings were limited to 3 for all mixtures, except the mixture with 15% GP and 35% FA-C. All mixtures exhibited comparable coefficient of thermal expansion (CTE) values, ranging from 4.8 to 5.2 E-6 in/in/°F. Incorporation of RCA did not have a significant effect on CTE values. Based on the obtained data, it was concluded that concrete mixtures incorporating high volume recycled aggregate and SCMs can present viable choices for sustainable pavement construction. The following four mixtures exhibited satisfactory performance and can be used for construction of the single layer pavement: (1) MoDOT PCCP as the reference concrete; (2) concrete incorporating the optimized binder (15% slag and 35% Class C fly ash replacements), 0.40 w/cm, without any RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C); concrete incorporating the optimized binder, 0.37 w/cm, and 50% coarse RCA (50C-37). The following three mixtures can be incorporated for construction of the top layer of the 2LCP systems: (1) MoDOT PCCP as reference; (2) concrete incorporating the optimized binder, 0.40 w/cm, without any RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C). The following two mixtures can be employed for construction of the bottom layer of the 2LCP systems: (1) concrete incorporating the optimized binder, 0.37 w/cm, 50% coarse RCA, and 15% fine RCA (50C15F-37); (2) concrete incorporating the optimized binder, 0.37 w/cm, and 70% coarse RCA (70C-37).

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Report number: cmr17-006
Published: May 2017
Project number: TR201502
Author(s): Dr. Kamal H. Khayat (principal investigator) and Seyedhamed Sadati (PhD Candidate student)
Performing organization: Missouri University of Science and Technology

Public Satisfaction Survey of High Friction Surface Treatment

Missouri adults in Callaway County were surveyed to capture their satisfaction with a local high friction surface treatment on westbound US 54.  This treatment was implemented in Project J5P3012.  The results are weighted proportionally to the county’s distribution in terms of geographic, gender, and age distributions.  Overall, local Missourians were very satisfied with the treatment and agreed that it made the road safer and easier to travel.  Questions pertaining to the best ways to communicate with Missourians were also asked and evaluated.

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Report number: cmr17-005
Published: April 2017
Project number: TR201620
Author(s): Lance C. Gentry
Performing organization: Heartland Market Research LLC

Right Transportation Solutions (RTS) Facebook Pilot

MoDOT explored an alternative public survey mechanism as a way to gauge the percent of customers who think that completed projects were the "Right Transportation Solution." Instead of having a consultant conduct a mailed survey, the department created an online survey in-house using SurveyMonkey and used social media (namely a Facebook targeted ad) to promote it. The pilot included an urban and a rural project (the recently completed I-64 Daniel Boone Missouri River Bridge project in the St. Louis District and an ADA project in Buffalo, MO from the Southwest District). The District created a communications and marketing plan to complement the Facebook ad, which targeted people within a certain radius of the project. For the Daniel Boone project, 612 responses were obtained, 314 coming from the Facebook ad (the rest resulting from the Division's marketing efforts). The survey results were overwhelmingly positive with 95% of respondents indicating that the project was the Right Transportation Solution. The benefits of this new survey mechanism included reduced cost, improved response rate, real-time feedback, real-time results, survey customization, demographic information and repeatability. The pilot survey demonstrated an innovative method of gauging public feedback which satisfied the concerns of the Executive Team and continues to validate MoDOT’s planning process. This new survey methodology is being deployed statewide with each District able to select relevant projects. MoDOT's Executive Team is excited by the real-time results and real-time dialogue of this innovative approach and wants to explore the use of this mechanism for future outreach efforts.

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Report number: cmr17-004 (summary only)
Published: March 2017
Project number: TR201706
Author(s): Missouri Dept. of Transportation (internal staff) 
Performing organization: Facebook

Transportation Research Methods Training: A Guide to Searching for Funding Opportunities

This project developed a training methodology focused on external funding. This hands-on training presented the basics of external funding identification, teambuilding and collaborative partners, and proposal element design. Real-time searches and tutorials were presented as part of the project. In addition, actual proposals were “red teamed”, or reviewed for completeness/readability, and a research methods handbook summarizing all of these activities was prepared as the deliverable for the final report.

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Report number: cmr17-003
Published: March 2017
Project number: TR201615
Author(s): Suzanna Long and Genda Chen
Performing organization: Missouri University of Science and Technology

Work Zone Simulator Analysis: Driver Performance and Acceptance of Missouri Alternate Lane Shift Configurations

The objective of this project is to evaluate MoDOT’s alternate lane shift sign configuration for work zones. The single sign proposed by MoDOT provides the traveler with enough information to let them know that all lanes are available to shift around the work zone, whereas the MUTCD signs require drivers to see two signs. This research simulation project evaluates the drivers’ lane shifting performance and acceptance of the alternate lane shift sign proposed by MoDOT to be used on work zones as compared to the MUTCD lane shift signs.  Based on the study results, no difference was observed between MUTCD lane shift sign and MoDOT lane shift sign lane shift patterns with respect to driving patterns. In summary, statistical data analysis clearly demonstrated that there was not a noticeable, statistical difference between lane change patterns of drivers in the MoDOT alternate signs with MUTCD signs in the work zone.

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Report number: cmr17-002
Published: February 2017
Project number: TR201612
Author(s): Suzanna Long
Performing organization: Missouri University of Science and Technology

St. Louis Inlaid Pavement Marker Survey

This report presents results from a survey of a diverse group of motorists perceptions and opinions of inlaid pavement markers.  Respondents participated in one of three ways: They (a) experienced the markers first-hand by driving a designated route with researchers and then completed a questionnaire, (b) were approached at a highway rest stop outside of St. Louis and asked to complete a questionnaire, or (c) were solicited via e-mail and asked to complete an online questionnaire.  Results indicate that motorists overwhelmingly reported favorable perceptions and opinions of inlaid pavement markers.  They reported that the markers enhance visibility of lane delineations, particularly while driving in rain and fog, thus making them feel safer while driving.  Roughly two thirds of all respondents reported that it would be “extremely useful” to have inlaid pavement markers on all roadways, with another 15% of respondents reporting that such omnipresence would be “very useful.” No differences in responding were observed between age, gender, or occupation groups.

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Report number: cmr 17-001
Published: February 2017
Project number: TR201611
Author(s): Drew Leins and Carmine Dwyer

Performing organization: Applied Research Associates, Inc. Transportation Infrastructure Division