Better Roads

March 2014

Better Roads Digital Magazine

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HighwayContractor 18 March 2014 Better Roads notable. This is being worked on nationally, with many people involved. "It's a change to traditional specifi cation require- ments concerning the dynamic shear rheometer and how that is utilized," he says. John D'Angelo, formerly a high-ranking offi cial with the Federal Highway Administration (FHWA) and now the chief operating offi cer of D'Angelo Consulting LLC, has written a white paper that describes testing procedures needed to evaluate the performance characteristics of rubberized bind- ers. "Without a well-defi ned binder specifi cation, adoption of the use of crumb rubber modifi ed (CRM) binders will be almost impossible to achieve," D'Angelo writes. "Now with AASHTO [Association of American State Highway and Transportation Offi cials], we're trying to develop a regular PG spec for rubber so that more states will feel comfortable in switching over and using it," says D'Angelo. "There are still a few issues to work out with it, but it is just about fi nished and ready to be approved by AASHTO. There are a lot of states that are interested and are looking at the spec." New testing equipment geometries are required to test CRM binders with rubber particles on the order of 1 mm in size, D'Angelo points out in his paper. "One approach that has been used in the food industries has been testing with concentric cylinder geometries," he writes. "Dynamic Shear Rheometers currently used for asphalt testing can be adapted to use a Searle (cup and bob) system. This type of system can perform all the same type of testing that is currently used for asphalt binder grading. The advantage is that the cup-and-bob geometry can easily handle larger gaps up to 4 to 7 mm, and therefore larger crumb rubber particles." (The cup and bob uses a center cylin- der, or bob, that rotates inside the cup, which holds the binder and is stationary.) "Initial comparisons of new testing geometry to the existing …geometry has shown that equivalent results can be ob- tained," writes D'Angelo in his paper. "The testing was done on both neat and CRM binders. Preliminary testing with the new testing geometry has shown that it will provide the same results as the standard parallel plate geometry in the dynamic shear rheometer. Both coarse and fi ne-ground CRM binders -\SSZLY]PJL IYHUJOVMÄJLZ ([SHU[H *OHYSV[[L +HSSHZ +LU]LY +LZ4VPULZ 0UKPHUHWVSPZ 2HUZHZ*P[` 3P[[SL9VJR 4PS^H\RLL 5HZO]PSSL 5L^6YSLHUZ 6RSHOVTH*P[` 7P[[ZI\YNO :[3V\PZ :HU(U[VUPV As a contractor, one of the most critical things is to protect your business with the right insurance. You can count on Bituminous for rock-solid protection. >P[OV]LY`LHYZVML_WLYPLUJLZWLJPHSPaPUNPUPUZ\YHUJLMVYJVU[YHJ[VYZ^LRUV^HUK\UKLYZ[HUK`V\Y I\ZPULZZHUKULLKZIL[[LY[OHUHU`VUL )`PUZ\YPUN^P[O)P[\TPUV\Z`V\»SSNL[THQVYHK]HU[HNLZPUJS\KPUN[OLYPNO[JV]LYHNLPUK\Z[Y`RUV^SLKNL `V\JHU[Y\Z[HUKZVSPKÄUHUJPHSZLJ\YP[`@V\»SSHSZVNL[JVUZPZ[LU[HUKJVUZ[Y\J[P]LYPZRJVU[YVSH[[LU[PVU WS\ZL_WLY[HUK[PTLS`YLZWVUZLZ[VHU`JSHPTZ>OLUP[JVTLZ[VNL[[PUN[OLYPNO[PUZ\YHUJL^L»YLTVYL [OHUHIP[IL[[LY¶^L»YLHSV[IL[[LY *HSS`V\YHNLU[[VKH`HUKHZRHIV\[\Z@V\»SSZLL^L»YL[VWVM[OLSPULH[WYV[LJ[PUN`V\YIV[[VTSPUL /VTL6MÄJL!9VJR0ZSHUK0SSPUVPZ + + ^^^IP[\TPUV\ZPUZ\YHUJLJVT What YOU do is what WE protect. ™ 7H[W,1)2WRRUYLVLWZZZEHWWHUURDGVFRPLQIR

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