Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/348335
Better Roads July 2014 15 loose layer of material on top. When more fi ll is spread, the top lift will be fl uffed and the previous layer will be compacted. A sheepsfoot compactor truly compacts from the bottom up. Using a sheepsfoot compactor has one defi nite benefi t. Be- cause the top lift of soil is always being fl uffed, the process helps aerate and dry out wet clays and silts. But the disadvantages of sheepsfoot compactors are nu- merous. The loose top-lift material can act as a sponge when it rains and slow the compaction process. The loose material also slows hauling units that deposit fi ll material, so haul cycle times are increased. Plus, sheepsfoot compactors can work only at speeds from 6 to 10 km/h (4 to 6 mph), which cancels any benefi t from impact and vibration. Pressure and manipulation are the only compactive forces exerted on the soil. Usually, 6-10 cycles (12-20 machine passes) are needed to reach target density on 200-mm (8-in.) lifts. Sheepsfoot compactors are no longer widely used. Pneumatic Compactors Pneumatic compactors are used on small-to-medium size soil compaction jobs, primarily on bladed, granular base materials. Often, they are used as a fi nishing compactor after a vibratory drum compactor completes compaction of the lift. Pneumatic compactors are best suited for sealing the sur- face, special applications such as compaction of thin lifts, or special requirements dictated by the job. The compactive forces (pressure and manipulation) gener- ated by the rubber tires work from the top of the lift down to produce density. The amount of compactive force can be varied by altering the tire pressure (the normal method) or by changing the weight of the ballast (done less frequently). The kneading action caused by the staggered tire pattern helps seal and smooth the surface. Pneumatic compactors can be used on soil and asphalt, an advantage that allows a road- building contractor to use one compactor for multiple stages of construction. For an image gallery of photos for this article, please go to BetterRoads.com This article and photos are courtesy of Cat Paving. -\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 HighwayContractor