Contractors, Project Owners Working to Find Cure for Concrete Cracking
To the dismay of materials suppliers, production and mix crews, contractors and project owners – concrete in bridge decks and overlays crack.
This fact is disheartening to all involved, especially Shelly & Sands Inc. Chief Engineer Robert Hunt, who has served the Zanesville company for 20 years. “Concrete cracks, period. It just does; it will always crack … Every bridge deck will have cracks in it,” he said. That is a difficult statement for Hunt, as it has been a priority for him, serving as the company’s bridge engineer the past 15 years, to eliminate or at least decrease the amount of concrete cracking on projects.
Talk to enough people who work around concrete and Hunt’s story of frustration is familiar. Concrete cracking is becoming more and more of an issue, and while the cause stirs debate, Hunt said many agree it deals with the amount of sand, gravel, crushed stone, cement powder and water used to produce the mix. “What is different now than 20 years ago, when we didn’t have as much cracking, has to do with mix designs,” Hunt said. Saying the concrete’s curing process hasn’t changed over the years, he adds, “there is something in the mix designs that is causing cracking that did not appear in the past …”
“Certainly, the past 10 years or more, it has been a concern,” said OCA Director of Public Agencies Chris Engle, regarding the increased cracking on Ohio’s bridge decks.
While there are several types of cracking in concrete, shrinkage is a main cause. Shrinkage cracking occurs when the mixture’s water evaporates and the concrete – as it cures or hardens – shrinks. “It’s not a danger to drive on them,” Engle said of traveling over the fine surface cracks resulting in concrete shrinkage. “It’s really more the longevity of the bridge.”
Reconfirming what Engle said about shrinkage cracking, Hunt said, “This is not structural cracking. It’s a durability and maintenance issue.”
Hunt said contractors realize even minimal concrete cracking – if ignored – can result in long-term issues for bridge structures. “ODOT would like to get 50-75 years from the bridge decks, and if you have the cracks and they’re not treated, they’re probably not going to be getting the design life that they’re hoping.”
This mutual frustration by contractors and DOTs about increased concrete cracking and the resulting decreased design life of bridges has resulted in contentious encounters. “Several disputes have reached Step 1 and Step 2 with ODOT,” Engle said. “… Our members feel like they’re following all the ODOT guidelines; they’re getting approved mix designs; they’re getting approved materials; they’re following the temperature requirements; they’re curing the concrete in the timeframe that they’re supposed to be cured in – and yet, the bridges are still cracking.”
Engle said the disputes over concrete cracking “usually come down to whether or not ODOT agrees that everything was done exactly right (by the contractor).” While Engle said the Spearin Doctrine has proved amicably for contractors – which he explains as: “If you give the owner what they asked for in the plans, you shouldn’t be liable for a result that isn’t satisfactory to the owner.” (Editor’s note: Ohio Contractor featured a twopart series on the Spearin Doctrine in its January-February 2022 and March-April 2022 issues.) “What we would like to do, “Engle added, “is find a way to keep these cracks from happening in the first place.”
Doing what’s asked, then being blamed when issues arise is a point of argument for contractors when it comes to concrete shrinkage and ensuing cracking. “I have fought this battle every year on some deck somewhere, and I’m tired of fighting it,” said Hunt of following the project’s prescriptive specifications and then told to remedy ensuing issues. The longtime member of the ODOT Structures Specifications Committee is hopeful, however, of recent changes to the committee’s mindset and innovations within the concrete industry.
“A couple of years ago, we started pushing really hard about the issues with the new concrete mixes, and in the Spec Committee we’re getting around to addressing it,” said Hunt. Speaking about the convening of a task force among select contractors and ODOT staff regarding bridge concrete shrinkage, Hunt said, “They (ODOT) have come to the point where I really think they finally believe there is something wrong with what the industry has been dealing with.
“Before, the bucket of water was being dumped on the contractor when there were issues regarding cracking,” Hunt added. “Now, they are climbing under the shower with us … (Concrete shrinkage) is something that we all have to deal with.”
Concrete shrinkage is not just an Ohio-based issue.
“There has always been some amount of cracking on some of our bridge decks over the time I have been in the industry – some is acceptable, and some is not,” said Indiana Department of Transportation (INDOT) Chief Engineer of Construction Greg Pankow. “It has been my experience that pretty much all cracking has some effect on the overall longevity of our structures …,” he added.
Hearing of the success Indiana concrete suppliers were having in the reduction of cracking on commercial projects, Pankow said INDOT began researching a concrete mixture shown to provide “significant benefits” during material placement and in the overall quality of in-place concrete. “Some of the benefits,” he said, “include improved water retention, workability, pumpability and higher pozzolanic activity, which can create higher strength and reduced permeability.”
The product Indiana contractors are utilizing commercially with success, and INDOT is testing on its bridge decks and overlays, is Element 5 (E5). E5 was developed by Joe Shetterley, whose family has been working as concrete finishers for three generations in Indiana.
Shetterley, the president of Specification Products, has been working with and developing E5 since 2015. It has been a whirlwind seven years. In 2017, E5 was used on one of the state’s largest parking facilities; in 2018, further testing of E5 at Purdue University began; in late-2019, INDOT contacted Specification Products about E5, and within six months it was tested on a bridge in Fort Wayne.
“INDOT placed the first full-depth bridge deck with E5 Internal Cure and no water curing in June 2020,” Pankow said. “Since that time, INDOT has made over 130 deck pours including both partial and whole structures with E5 admixtures …”
The use of E5 on INDOT projects has thus far been only through construction memorandums. “We’re allowing contractors to utilize the product in concrete mixes …,” Pankow added. “We are encouraged by the results so far and are constantly working with industry to improve the end product and the requirements in our memos.”
Ohio contractors are closely monitoring E5’s testing and development. “What E5 does is it keeps the water in the mix; it prevents it from evaporating,” Hunt said. He explained that oftentimes prior to the use of admixtures, like E5, evaporation occurs before the concrete mix is fully hydrated. “What happens, is that the water is not perfectly distributed through the mix. So, what occurs to the concrete is that if there is not enough water, and when it dries it starts to shrink and develop cracks.”
E5 Consultant Jim Render, who has 45 years of experience as a civil engineer working with ready mix and mixture companies, said in three years’ time he has seen E5 grow from being used by no DOTs “to virtually every DOT in the United States calling and asking … They want to test it and find out more information.”
E5’s initial use on Ohio road projects was by E.S. Wagner Co. on a bridge approach near Toledo. Shelly & Sands first used E5 in 2021 on a Franklin County Engineers’ bridge and overlay project. Following that initial effort, Shelly & Sands obtained permission to utilize E5 on an ODOT District 5 bridge deck in Zanesville, and is currently in the first phase of an Interstate 70 project featuring 16 bridge decks in which one third will be performed with E5. Other OCA members, like Complete General Construction Co., are also conducting projects with E5.
“We love it,” Hunt said of Shelly & Sands’ early experience with E5. “We love that there is a potential of alleviating much of the shrink cracking problem … It’s too soon in our experience to make a determination … but the potential is there.”