More resilient and compatible repair Another way internally cured concrete can improve concrete bridge and pavement construction is to improve the efficacy of repairs and reworks. Just as conventionally cured concrete can shrink and crack leading to degradation, it can do the same when used to patch existing concrete. Because internally cured concrete reduces the strain caused by shrinkage, it reduces, both in number and width, the cracking typi- cally seen in high early strength concrete. The improved performance of internally cured patching or full depth panel replacement permits the repair to last longer than the few year lifespan commonly seen. As noted in a 2016 report by the U.S. Depart - ment of Transportation’s Federal Highway Association, the benefits of internally cured concrete indicate its performance, in both initial building and repair, “should be superior to conventional concrete pave- ments, resulting in improved life-cycle cost.”
Example from the field Along the shores of Lake Erie, the Buffalo, NY metropolitan area has its share of winter weather. Its highways see some of the greatest uses of deicing chemicals in the country. To help to reduce chloride attack and increase service life of their highway bridges, the New York State Department of Transportation (NYSDOT) chose to utilize internal cur - ing high performance concrete to construct the bridge decks on the ramps between Interstate 190 and Interstate 290. Mixes were developed to meet the design requirements on the project. The natural sand was reduced by 30 percent by volume and replaced with saturated ESCS fines. The non-internally cured concrete was used on the approach slabs to have an area of comparison exposed to the same conditions. The mix proportions both with and without internal curing are shown in Table 1. The 244 pounds of ESCS lightweight aggregate provided an extra 6.4 gallons of water to hydrate the cementitious materials per yard of con- crete. This internal curing water is held in the pores of the lightweight aggregate until the concrete set, therefore it does not contribute to the water cementitious ratio of the mix. To evaluate the effectiveness of internal curing, the bridge decks were inspected 6 months after concrete placement and no cracks were found. This structure was part of a study that the NYSDOT conducted to evaluate internal curing. The agency has since made internal curing a requirement on all multi-span bridges in the state.
COREY COFFELT joined Buildex Lightweight Aggregates in Kansas City 4.5 years ago for business development and sales. He is active in the lightweight industry promotions committees through the Expanded Shale, Clay & Slate Institute. Prior to Buildex, Corey assisted public and private organizations develop envi- ronmentally advantageous cost-saving waste and recycle programs utilizing his 33-year background in the waste and recycling industry. Given the relative ease with which internally cured concrete can be incorporated into bridge construction and the significant improve - ments it can facilitate, using lightweight aggregate made from ESCS to bolster bridge resilience is both feasible and recommended. Realizing concrete’s full potential Internally curing concrete results in stronger, more durable structures. When it comes to bridge construction, this translates to safer passage for vehicles and pedestrians. It also helps departments of transportation at the state level maximize their investments by reducing the amount of maintenance and repair a bridge would need over its service life. And if a bridge needs repair or updating, internally cured concrete can help ensure a more compatible and longer-lasting patch.
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