WWW.ACPA.ORG 11 FALL // 2022 continues on page 12 » began adopting internal curing methods for bridge decks. Pavements have been constructed in Texas and by the Illinois Tollway, said Dr. Weiss. “There are now numerous states allowing internal curing of concrete pavement, and more state Departments of Transportation are open to the technology. “Porous, lightweight aggregate is plentiful in most regions of the country, so supply is not a challenge,” says Weiss. “The greatest challenge is controlling the moisture of the aggregate. While the Illinois Tollway was a mainline pavement, some of the most common uses for internal curing include patching, bridge decks, and continuously reinforced concrete pavement (CRCP).” According to a Federal Highway Administration Tech Brief, “The water that is absorbed in the lightweight aggregate does not contribute to the classic definition of the water-to-cement ratio. The water-to-cement ratio is a descriptor of the structure of the matrix and pores that develop in the fluid concrete system. Once the concrete sets, the structure and pore network have been established, and water can only aid in hydration. The water in the lightweight aggregate will desorb (leave) the pores of the lightweight aggregate as the negative pressure in the pore fluid develops with setting and increases thereafter.”2 “Studies by Rao and Darter also suggested several benefits of using internal curing in pavements,” said Weiss. One of the benefits includes a reduction in curl in CRCP.3 Field tests of internal curing on two test sections containing lightweight fine aggregate (LWFA) performed by the National Concrete Pavement Technology Center4 found: • Internal curing improved the degree of hydration over time. • The inclusion of LWFA did not affect maturity. • The internal curing reduced temperature and moisture differentials in the system. • Hence, warping and curling were reduced significantly. This is a benefit, as ride is improved, and the risk of corner breaks is reduced. Based on this observation, it is likely that slab sizes can be extended for thinner sections, thus keeping saw-cuts out of the wheel path. • The permeability of the mixture containing LWFA was found to be improved— potentially increasing the pavement’s longevity. • Structural design modeling did not reflect any changes for traffic loadings on these pavements. • A life-cycle cost analysis indicated a longterm financial benefit to the technique based on reduced frequency of rehabilitation work and extended predicted life. • Reports from construction sites indicated that storing and preconditioning the LWFA would be a challenge in larger applications; otherwise, no significant changes were observed. Battery Powered Equipment: Green Alternative on Horizon The automotive industry’s push to increase the number of electrified vehicles in their portfolios raises the question: What pavement construction equipment can be electrified? The question was answered with GOMACO’s introduction of the first battery-powered curb machine. “We started with the curb and gutter slipform paver due to the size and power rating,” says Kevin Klein, Vice President of Engineering/ Research and Development. “Initially, our main objective for a smaller machine was achieving a full day of paving with a single charge in the most cost-effective way possible. Now that battery technology is increasing, we’re looking at the possibility of electrifying the rest of the GOMACO lineup.” At this time, the battery-powered curb and gutter slipform paver is still being used for research and testing but have been used on several job sites as part of the testing phase. One of those job sites was a 15,000-linear foot job which included a The automotive industry’s push to increase the number of electrified vehicles in their portfolios raises the question: What pavement construction equipment can be electrified? The question was answered with GOMACO’s introduction of the first battery-powered curb machine.
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