Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/258673
Better Roads February 2014 25 The moisture challenge Another challenge is moisture in the shingles. A problem can arise when moisture in the shingles is inconsistent throughout a stockpile. For moisture testing, samples are small, but the plant must run tons of RAS. Moisture tests in shingles can produce satisfactory results in the laboratory, but the stockpile can still present problems, says Chuck Fuller of Ramming Paving Co. Ltd., Austin, Texas. "If you're at 7- to 8-percent moisture in the RAS, it can produce a failure in the field," Fuller says. "The fundamental problem is that shingles tend to hold a lot of water," Swanson continues. "And the water can be quite var- ied within a given quantity of shingles, so it's kind of hard to keep up with. That means it's important to keep materials dry. But with shingles, it's more important because shingles can hold upwards of 20 percent moisture. "So all of a sudden, you can be putting proportionately a very large amount of water into the system," Swanson says. "And if you don't know what that percentage of water is with a fair degree of accuracy, and it all weighs as shingles, then yes, you're going to throw your binder content off." For example, if the shingles contain 5-percent water, a producer will subtract that from the weight of materials that is used to calculate liquid AC content. "If it's 5-percent water, then it's 95-percent liquid asphalt and aggregate," he says. "So that's the mass that you calcu- late your asphalt on." Swanson says producers running RAS need to check mois- tures often in the stockpile. "And more than that, you really need to keep the shingles dry," he says. "Another problem is that shingles tend to be delivered pretty wet. Most of the contractors are not processing the shingles themselves. They're buying them pre-processed. And processing the shingles is typically a wet process. The water doesn't drain out too well. So I don't know to what degree the shingle pro- cessor has control over the amount of water that is residual in the shingles, but that is a factor in the water content of the shingles going into the plant." Shingles need to be covered to keep them dry, Swanson says. A cover over the RAS will also provide shade from the hot sun and prevent the RAS from binding together. Daniel C. Brown is the owner of TechniComm, a firm that specializes in communications for the construction industry. ÊnääÎÈΣÇÇ£ÊUÊÜÜÜ°}Ü>ÞiµÕ«iÌ°VÊÊUÊ^ÊÓä£ÎÊ}Ü>ÞʵիiÌÊ «>Þ°ÊÊÊÀ}ÌÃÊÀiÃiÀÛi`°Ê Improved Deicing: UÊiÃÃÊ>ÌiÀ>ÊLÕViÊ>`Ê«ÀÛi`ÊÀ>`Ê>`ið UÊiÃÃÊyÕiViÊvÀÊÜ`° UÊVViiÀ>Ìi`ÊiÌ}Ê«ÀViÃð ,PSURYHG(IÀFLHQFLHV UÊ À>`V>ÃÌÊÊi]ÊÌÜ]ÊÀÊÌÀiiÊ>ið UÊ}iÀÊ>««V>ÌÊëii`ÃÊ>`ÊÜ`iÀÊëÀi>`ÊÜ`Ì° UÊ,i`ÕVi`Ê>ÌiÀ>ÊÕÃ>}iÊ>`Ê}iÀÊÀÕÌið UÊ"i«iÀÃÊÃÌ>>ÌÊÀÊÀiÛ>ÊÊ ÊÊÊÕ`iÀÊxÊÕÌiÃ. 7iÊ>ÊÜÌiÀÊÃÌÀÊÌÃ]ÊÞÕÀÊ}>ÊÃÊÌÊi>ÌiÊÃÜÊ>`Ê ViÊÊÀ>`ÃÊ>ÃʵÕVÞÊ>ÃÊ«ÃÃLi°Ê/iÊ7>ÞÊ8â>ÌÊ>iÃÊ ÞÕÀÊÃÌÀiiÌÃÊÃ>viÀ]ÊÃiÀ]ÊLÞÊ>««Þ}Ê>ÊÇä\ÎäÊÝÌÕÀiÊvÊ Ã>ÌɵÕ`ÊÜÌÊ«ÀiVÃÊ>««V>ÌÊÌiV}Þ°Ê 7H[W,1)2WRRUYLVLWZZZEHWWHUURDGVFRPLQIR