New research project report: “Extended Life Concrete Bridge Decks Utilizing Internal Curing to Reduce Cracking”: The report was prepared by National Concrete Pavement Technology Center (CP Tech Center) and InTrans researchers Xuhao Wang, Peter Taylor, Katelyn Freeseman, and Payam Vosoughi, for the Ohio Department of Transportation (ODOT). This project addresses the ongoing concern about premature cracking (that reduces the service life of bridges, resulting in increased maintenance and replacement costs) of concrete bridge decks by looking into the benefits of using lightweight fine aggregate (LWFA) in concrete mixtures to provide internal curing (IC). It includes a suggested specification for IC concrete with LFWA to increase the probability of achieving crack-free, long-lasting bridge decks. This research project is intended to help the ODOT prepare a specification that will increase the probability of achieving crack free, long-lasting concrete bridge decks. The research will develop a state-of-the-art bridge concrete that will give a unique consideration to coming up with the best mix characteristics that will ultimately extend bridge life and delay (or eliminate) the need to replace decks prior to superstructure replacement. Aimed at assessing the benefits of this technology in Ohio, the two main objectives of this study are that the bridge deck:
- Will be crack-free immediately after construction
- Will have the strength and serviceability characteristics that will allow it to perform for up to 75 years of active service
The following can be concluded from the work conducted:
• All of the mixtures tested in the laboratory provided adequate strength
• All of the mixtures were sufficiently impermeable
• As the amount of slag in the mixture increased, shrinkage and cracking risk decreased
• Mixtures containing LWFA exhibited lower shrinkage and cracking risk than mixtures without LWFA
• Mixtures containing SRA exhibited lower shrinkage and cracking risk than mixtures without SRA
• There was no significant difference in structural response between the two bridges
• In terms of cracking after one year, the bridge deck with the internal curing mix design outperformed that of the normal concrete mix in all areas observed by the inspection team
• Life cycle cost assessment of the recommended approach demonstrated that internal curing will provide long term savings, despite higher costs at the time of construction
For more information on this project, please go to: https://cptechcenter.org/research/in-progress/extended-life-concrete-bridge-decks-utilizing-improved-internal-curing-to-reduce-cracking/
For the Ohio LTAP Center video recording of the research results presentation from January 25, 2019, please go to: https://www.youtube.com/watch?v=n_yoQaEUKUU
FOUR ADDITIONAL CP TECH CENTER PROJECTS ON INTERNAL CURING—2017 and 1 in progress:
1 – “Guide Specification for Internally Curing Concrete”: IC is a practical way of supplying additional curing water throughout the concrete mixture. This water can improve the hydration of cement, reduce autogenous shrinkage, and improve durability.
• The purpose of this document is to provide guidance for the development of project specifications for IC concrete projects.
• The guidance is designed to supplement the agency’s standard specifications for concrete pavement.
• This document contains:
- IC specification language
- References to IC resources
- References to IC instructional videos
- References to tools that can be used for IC of concrete or providing quality control
For more information, please go to: https://intrans.iastate.edu/research/completed/guide-specification-for-internally-curing-concrete/
For the PDF of this Guide, please click on image to the right, or go to: https://intrans.iastate.edu/app/uploads/2018/09/IC_guide_spec_w_cvr.pdf
2 – “Lifecycle Cost Analysis of Internally Cured Jointed Plain Concrete Pavement”: This analysis was based on a pavement designed for use in Dubuque, Iowa. IC is a technique that has been developed to prolong cement hydration by providing internal water reservoirs in a concrete mixture that do not adversely affect the concrete mixture’s fresh or hardened physical properties. IC grew out of the need for more durable structural concretes that were resistant to shrinkage cracking.
This report covers an investigation into the relative costs and benefits of IC using a lifecycle cost analysis (LCCA) that compares IC jointed plain concrete pavement to conventionally cured (CC) pavement. According to the analysis, IC concrete makes it possible to design pavement with decreased thickness or increased joint spacing or to reduce the required maintenance over the analysis period, which results in savings in initial construction cost. Even if the thickness does not change, IC pavement requires less maintenance than a comparable CC pavement to provide satisfactory performance over its service life. However, the initial construction cost of IC pavement is about 3.2% higher than that of CC pavement with the same thickness. Considering all of the evidence, the net present value of IC pavement is less than that of CC pavement. For more information on this document, please go to: https://intrans.iastate.edu/s=Lifecycle+Cost+Analysis+of+Internally+Cured+Jointed+Plain+Concrete+Pavement. For the PDF of this document, please click on image to the right, or go to: https://intrans.iastate.edu/app/uploads/2018/07/lifecycle_cost_analysis_of_IC_JPCP_w_cvr.pdf
3 – “Impacts of Internal Curing on the Performance of Concrete Materials in the Laboratory and the Field”: IC is a technique to prolong cement hydration by providing internal water reservoirs in a concrete mixture. These reservoirs do not affect the initial water-to-cementitious materials (w/cm) ratio, but do provide water for curing throughout the thickness of the element.
Benefits of this approach include improved mechanical properties as well as reduced risk of moisture gradients, thus reducing the potential for warping. The aim of this work was to assess whether joint spacings could be increased in slabs containing lightweight fine aggregate (LWFA) as a source of IC. For the PDF of this report, please click on image to the right, or go to: https://intrans.iastate.edu/app/uploads/2018/07/impacts_of_IC_on_contraction_joint_spacing_w_cvr.pdf
4 – Project in progress: Start Date: 3-22-18 End Date slated: 9-30-20 titled:
“Impacts of Internally Cured Concrete Paving on Contraction Joint Spacing, Phase II”:
IC is a practical way of supplying additional curing water dispersed throughout a concrete mixture that can improve the hydration of cement, reduce autogenous shrinkage, and improve durability. The fundamental concept is to provide reservoirs of water within the matrix such that the water does not increase the initial water/cementitious materials ratio of the mixture, but becomes available for helping continue hydration once the system has begun to dry out. Numerous studies have reported premature transverse cracking resulting from insufficient curing of concrete pavements—represents a safety issue and a cost issue in terms of transportation agencies’ time and money required to implement repair solutions. There has been considerable work conducted both in the laboratory and in the field to confirm that IC concrete is fundamentally sound and practical for construction purposes.
The primary objective of this research study is to perform a full-scale field demonstration of the IC technology and its efficient performance benefits for Iowa’s city and county roadways and state highways. In consultation with the project Technical Advisory Committee, two upcoming construction projects conducted by the city, county, or Iowa Department of Transportation (IDOT) will be identified for IC concrete field demonstration. This type of technology is suitable for use in a variety of transportation infrastructure components, including roads, bridges, sidewalks, rest areas, etc. For this ongoing project, please go to: https://intrans.iastate.edu/research/in-progress/impacts-of-internally-cured-concrete-paving-on-contraction-joint-spacing-phase-2/
For the January 2018 ISCP article titled “CP Tech Center Publishes Trio of New Reports: ‘Internal Curing of Concrete'”, please go to: https://www.concretepavements.org/2018/01/11/cp-tech-center-publishes-trio-of-new-reports-internal-curing-of-concrete/