View source for Chipseal

{{Short description|Pavement surface treatment}}
{{globalize|date=February 2020}}
[[File:Chipnseal.jpg|thumb|A chipseal road near Kempton, Indiana in the United States]]

'''Chipseal''' (also '''chip seal''' or '''chip and seal''' or '''spray seal''') is a [[pavement (material)|pavement]] surface treatment that combines one or more layers of [[Bitumen|asphalt]] with one or more layers of fine [[Construction aggregate|aggregate]]. In the United States, chipseals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as '''asphaltic surface treatment'''. This type of surface has a variety of other names including '''tar-seal'''<ref>{{cite book |last1=Orsman |first1=H. W. |title=Heinemann New Zealand Dictionary |date=1979 |publisher=Heinemann Educational Books (NZ) Ltd |location=Auckland |isbn=0-86863-373-9 |page=1131 |edition=First}}</ref> or '''tarseal''',<ref>{{cite book |last1=Orsman |first1=Harry W. |title=The Dictionary of New Zealand English |date=1997 |publisher=Oxford University Press |location=Auckland |isbn=0-19-558347-7 |page=818 |edition=First}}</ref> '''tar and chip''', '''sprayed seal'''<ref>[http://www.lgam.info/sprayed-seal Sprayed Seal], Local Government & Municipal Knowledge Base, accessed January 29, 2010</ref> '''surface dressing''',<ref>{{cite book |last1= Gransberg |first1=Douglas D. |first2= David M. B. |last2=James |others=National Cooperative Highway |title=Chip Seal Best Practices |url=https://books.google.com/books?id=gTCHtuGENwQC&q=Chip+Seal+Best+Practices   |year=2005 |publisher=Transportation Research Board |isbn= 9780309097444 |pages=13–20 }}</ref> or simply '''seal'''.<ref>{{Cite web|url=https://www.nzherald.co.nz/nz/more-than-100-motorists-lodge-damage-claims-after-road-seal-peels-off-at-dome-valley/X755QMIUAJBZNJX4C4PDXFX3SE/|title = More than 100 motorists lodge damage claims after road seal peels off at Dome Valley| date=25 February 2024 }}</ref>

In Australia as well as New Zealand, chipseal roads are common, including usage on major highways.

==Uses==
Chipsealing is cheaper than resurfacing an [[asphalt concrete]] or a [[Portland cement]] concrete pavement, but not as long-lasting.

[[File:Surface dressing - geograph.org.uk - 887341.jpg|thumb|A chipseal road in the United Kingdom]]

==Installation==
[[File:Fresh_oil_and_chips.jpg|thumb|right|Advisory sign to alert people that not all gravel have been pressed into the surface]]
Chipseals are constructed by evenly distributing a thin base of hot tar, [[bitumen]] or asphalt onto an existing pavement and then embedding finely graded aggregate into it. The aggregate is evenly distributed over the hot seal spray, then rolled into the bitumen using heavy rubber tired rollers creating a paved surface. A chip-seal-surfaced pavement can optionally be sealed with a top layer, which is referred to as a fog seal or enrichment.

The introduction of polymer-modified bitumen and emulsion binder has increased chipseal's ability to prevent [[Reflective crack|crack reflection]] and improve stone retention by improving the properties of the bitumen binder. Newer techniques use asphalt [[emulsion]] (a mixture of liquid asphalt, [[surfactant]], and water) instead of asphalt. This has been shown to help reduce aggregate loss and reduce cost of installation, but can increase stripping (separation of the binder from the aggregate). It reduces emissions of [[volatile organic compound]]s (VOCs) due to the lower solvent content. New methods also utilize cross linking styrene acrylic polymers which also provide quality water resistance. Chips precoated with about one percent bitumen have been used successfully to minimize aggregate loss and to give the surface a black look.
 
It can keep good pavement in good condition by sealing out water, but provides no structural strength and will repair only minor cracks. While the small stones used as surface yield a relatively even surface without the edges of patches, it also results in a very rough surface that leads to louder [[Roadway noise|rolling noise]] from automobile wheels.

Although chipseal is an effective low-cost way to repair roads, it has some drawbacks. Loose [[crushed stone]] is often left on the surface, owing to underapplication of bitumen or overapplication of stone. If not removed, this can cause safety and environmental problems such as cracked windshields, chipped paint, loss-of-control crashes (especially for motorcyclists, bicyclists and small trucks), and deposition of foreign material into drainage courses. Therefore, it is very important to sweep the road after the emulsion sets. As mentioned earlier, this problem can be minimized by using chips precoated with bitumen. Overapplication of emulsion can lead to [[bleeding (roads)|bleeding]], a condition where the excess asphalt rises to the surface, creating a very smooth surface that is very [[road slipperiness|slippery when wet]] and bubbling in the hotter summer months. As cars drive over it the tires kick up this tarry substance on to the side of the car. It can only be cleaned off with a solvent remover or diesel fuel.

===Chip seal installation over gravel roads===
Chip seal products can be installed over gravel roads to eliminate the cost of grading, road roughness, dust, mud, and the cost of adding gravel lost from grading.  Adding chip seal over gravel is about 25% of the price of resurfacing with [[Asphalt concrete|asphalt]], $170,000 for a 4-mile project done in Minnesota<ref>[https://www.mnltap.umn.edu/opera/projects/2013/documents/silvercreek.pdf Silver Creek] umn.edu</ref> compared to $760,000 had it been redone with asphalt.  The surface lasts for 5–7 years.  Patch work can be done with a bucket of tar sealer and more chip seal over the top.  The chip seal matt surface handles thermal variation well and doesn't crack like asphalt roads. A thin penetrating emulsion primer (PEP) coat is usually applied over the gravel before the chip seal matt is applied.

== Noise and vibrational effects ==
[[File:Chipseal_surface_close-up_view.jpg|thumb|right|A close-up view of chipseal surface]]
The rough wearing surface of the chipseal generates more [[roadway noise]] at any operating speed than do typical asphalt or concrete surfaces. These sound intensities increase with higher vehicle speeds.<ref>{{cite journal |first= C. Michael |last= Hogan |title= Analysis of highway noise |journal= Journal of Water, Air, & Soil Pollution |volume= 2 |issue= 3<!--Biomedical and Life Sciences and Earth and Environmental Science Issue-->|pages= 387–392 |date=September 1973 |publisher= Springer Verlag, Netherlands |doi= 10.1007/BF00159677 |bibcode= 1973WASP....2..387H |s2cid= 109914430 |issn= 0049-6979}}</ref> There is a considerable range in acoustical intensities produced depending upon the specific tire tread design and its interaction with the roadway surface type.

The rough surface causes noticeable increases in vibration and rolling resistance for bicyclists, and increased tire wear in all types of tires.

Vehicle speed can affect the set up time with chipseal. Shortly after construction (depending on weather conditions) the set speed for chipseal is {{convert|10|-|15|mph}} for the first 24–48&nbsp;hours after construction.{{Citation needed|date=November 2008}}

==See also==
*[[Macadam]]
*[[Asphalt concrete|Asphalt]]
*[[Road surface#Bituminous surface|Bituminous surface]]

==References==
{{reflist}}

==External links==
*[http://www.gjcity.org/residents/street-systems/chipseal-program/ City of Grand Junction, CO page on Chipseal]
*[https://trl.co.uk/reports/RN039 TRL Design Guide for Surface Dressing (Road Note 39)]

{{Road types}}

[[Category:Pavements]]
[[Category:Building materials]]
[[Category:Stone (material)]]
[[Category:New Zealand inventions]]