Editing Road (section)

==Maintenance==
{{See also|Roadworks|Road surface#Surface deterioration}}
[[File:Baustelle.svg|thumb|upright|"Road works ahead" sign, typically used in Europe]]
Like all structures, roads deteriorate over time. Deterioration is primarily due to environmental effects such as [[frost heave]]s, thermal cracking and oxidation often contribute, however accumulated damage from vehicles also contributes.<ref name="frost">{{cite web |author1= S.Kameyama |author2=M. Kato |author3=A. Kawamura |author4=K. Himeno |author5=A. Kasahara |work= ISAP 9th Conference Titles & Abstracts| id=09044 |title= Effects of Frost Heave on the Longitudinal Profile of Asphalt Pavements in Cold Regions |publisher= International Society for Asphalt Pavements |date= August 2002 |url=http://www.asphalt.org/Pubs/9th_conf_abst.html |access-date= 2007-05-13 |url-status=dead |archive-url=https://web.archive.org/web/20070813141736/http://www.asphalt.org/Pubs/9th_conf_abst.html |archive-date= 2007-08-13 }}</ref> According to a series of experiments carried out in the late 1950s, called the [[AASHO Road Test]], it was empirically determined that the effective damage done to the road is roughly proportional to the [[fourth power]] of [[gross axle weight rating|axle weight]].<ref name="Motorway_Achievement_Pg252">{{cite book |author1=Ron Bridle |author2=John Porter |title= The Motorway Achievement: Frontiers of Knowledge and Practice |publisher= Thomas Telford |year= 2002 |page= 252 |url=https://books.google.com/books?id=7Yqxyefv-VAC&q=4th+power+of+axle+weight&pg=PA252 |isbn= 978-0-7277-3197-5 }}</ref> A typical [[semi-trailer truck|tractor-trailer]] weighing 80,000 [[pound (mass)|pounds]] (36.287 [[tonne|t]]) with 8,000 pounds (3.629 t) on the steer axle and 36,000 pounds (16.329 t) on both of the tandem axle groups is expected to do 7,800 times more damage than a passenger vehicle with 2,000 pounds (0.907 t) on each axle. [[Pothole]]s on roads are caused by rain damage and vehicle braking or related construction work.

[[File:Making lines on the road.JPG|thumb|upright|[[Road surface marking|Line marking]] in rural India]]

[[Road surface|Pavements]] are designed for an expected [[service life]] or [[design life]]. In some parts of the United Kingdom the standard design life is 40 years for new [[bitumen]] and concrete pavement. Maintenance is considered in the whole life cost of the road with service at 10, 20 and 30-year milestones.<ref name="Highways_The_Location">{{cite book |last= O'Flaherty |first= Coleman A. |title= Highways: The Location, Design, Construction & Maintenance of Road Pavements |publisher= Elsevier |year= 2002 |page= 252 <!-- different book different fact same page as ref Name="Motorway_Achievement_Pg252" --> |url=https://books.google.com/books?id=Ren4sWQ3jKkC&q=Pavements+are+designed+for+an+expected+service+life&pg=PA252 |isbn= 978-0-7506-5090-8 }}</ref> Roads can be and are designed for a variety of lives (8-, 15-, 30-, and 60-year designs). When pavement lasts longer than its intended life, it may have been overbuilt, and the original costs may have been too high. When a pavement fails before its intended design life, the owner may have excessive repair and rehabilitation costs. Some [[asphalt concrete|asphalt]] pavements are designed as '''perpetual pavements''' with an expected structural life in excess of 50 years.<ref>{{cite book |last1= Newcomb |first1= David E. |last2= Willis |first2= Richard |last3= Timm |first3= David H. |title= Perpetual Asphalt Pavements: A Synthesis |publisher= Asphalt Pavement Alliance |year= 2010 |location= Lanham, Maryland |url=http://asphaltroads.org/images/documents/Perpetual_Pavement_Synthesis.pdf |access-date= 2013-01-22}}</ref>

Many asphalt pavements built over 35 years ago, despite not being specifically designed as a perpetual pavement, have remained in good condition long past their design life.<ref>{{cite web |url=http://asphaltroads.org/perpetual-pavement/award-winners.html |title= Perpetual Pavement Award Winners |access-date= 2013-01-22 |author= Asphalt Pavement Association}}</ref> Many concrete pavements built since the 1950s have significantly outlived their intended design lives.<ref name="Map_Future">{{cite web |author1= Theodore R. Ferragut |author2= Dale Harrington |author3= Marcia Brink |name-list-style= amp |title= Road Map to the Future |publisher= United States Department of Transportation – Federal Highway Administration |date= July–August 2002 |url=http://www.tfhrc.gov/pubrds/02jul/10.htm |access-date= 2007-05-13 |archive-url=https://web.archive.org/web/20070814113422/http://www.tfhrc.gov/pubrds/02jul/10.htm |archive-date= 2007-08-14 |url-status= dead }}</ref> Some roads like [[Chicago]]'s [[Wacker Drive]], a major two-level (and at one point, three-level) roadway in the downtown area, are being rebuilt with a designed service life of 100 years.<ref name="Fly_Ash">{{cite web |last= ISG Resources, Inc |title= Fly Ash Concrete Design for Chicago's 100-Year Road Structure |work= Case Study |publisher= U.S. Environmental Protection Agency |date= December 2003 |url=http://www.epa.gov/epaoswer/osw/conserve/c2p2/cases/wacker-dr.pdf |access-date= 2007-05-13 }}</ref>

Virtually all roads require some form of maintenance before they come to the end of their service life. Pro-active agencies use [[pavement management]] techniques to continually monitor road conditions and schedule [[preventive maintenance]] treatments as needed to prolong the lifespan of their roads. Technically advanced agencies monitor the road network surface condition with sophisticated equipment such as laser/inertial [[profilometer]]s. These measurements include road [[curvature]], [[cross slope]], [[Asperity (material science)|asperity]], [[surface roughness|roughness]], [[rut (roads)|rutting]] and [[texture (roads)|texture]]. Software algorithms use this data to recommend maintenance or new construction.

Maintenance treatments for asphalt concrete generally include thin asphalt overlays, crack sealing, surface rejuvenating, fog sealing, [[pavement milling|micro milling]] or [[diamond grinding of pavement|diamond grinding]] and [[Chipseal|surface treatments]]. Thin surfacing preserves, protects and improves the functional condition of the road while reducing the need for routing maintenance, leading to extended service life without increasing structural capacity.<ref name="Thin_Surfacing">{{cite web |first1=Ludomir |last1=Uzarowski |first2=Michael |last2=Maher |first3=Gary |last3=Farrington |author4= Golder Associates Ltd. |title= Thin Surfacing – Effective Way of Improving Road Safety within Scarce Road Maintenance Budget |work= Paper for presentation at the 2005 Annual Conference of the Transportation Association of Canada in Calgary, Alberta |publisher= Transportation Association of Canada |year= 2005 |url=http://www.tac-atc.ca/english/pdf/conf2005/s16/uzarowski2.pdf |access-date= 2007-05-14 |archive-url=https://web.archive.org/web/20080407011631/http://www.tac-atc.ca/english/pdf/conf2005/s16/uzarowski2.pdf <!-- Bot retrieved archive --> |archive-date= 2008-04-07}}</ref>

Older concrete pavements that develop faults can be repaired with a [[dowel bar retrofit]], in which slots are cut in the pavement at each joint, and dowel bars are placed in the slots, which are then filled with concrete patching material. This can extend the life of the concrete pavement for 15 years.<ref>{{cite web|title=Dowel Bars for New and Existing Concrete Pavements|url=http://www.wsdot.wa.gov/NR/rdonlyres/0137787C-4E9A-408C-A9CA-ECC02878D623/0/DowelBarsfolio_March2013.pdf|publisher=Washington State Department of Transportation|access-date=24 March 2014|date=February 2013}}</ref>

Failure to maintain roads properly can create significant costs to society. A 2009 report released by the American Association of State Highway and Transportation Officials estimated that about 50% of the roads in the US are in bad condition, with urban areas worse. The report estimates that urban drivers pay an average of $746/year on vehicle repairs while the average US motorist pays about $335/year. In contrast, the average motorist pays about $171/year in road maintenance taxes (based on 600 gallons/year and $0.285/gallon tax).

===Slab stabilization===
Distress and serviceability loss on concrete roads can be caused by loss of support due to voids beneath the concrete pavement slabs. The voids usually occur near cracks or joints due to surface water [[infiltration (hydrology)|infiltration]]. The most common causes of voids are pumping, consolidation, subgrade failure and bridge approach failure. Slab stabilization is a non-destructive method of solving this problem and is usually employed with other [[concrete pavement restoration]] methods including patching and diamond grinding. The technique restores support to concrete slabs by filing small voids that develop underneath the concrete slab at joints, cracks or the pavement edge.

The process consists of pumping a cementitious [[grout]] or [[polyurethane]] mixture through holes drilled through the slab. The grout can fill small voids beneath the slab and/or sub-base. The grout also displaces free water and helps keep water from saturating and weakening support under the joints and slab edge after stabilization is complete. The three steps for this method after finding the voids are locating and drilling holes, grout injection and post-testing the stabilized slabs.

Slab stabilization does not correct depressions, increase the design structural capacity, stop erosion or eliminate faulting. It does, however, restore the slab support, therefore, decreasing deflections under the load. Stabilization should only be performed at joints and cracks where the loss of support exists. Visual inspection is the simplest manner to find voids. Signs that repair is needed are transverse joint faulting, corner breaks and shoulder drop off and lines at or near joints and cracks. Deflection testing is another common procedure used to locate voids. It is recommended to do this testing at night as during cooler temperatures, joints open, aggregate interlock diminishes and load deflections are at their highest.

===Testing===
Ground penetrating [[radar]] pulses electromagnetic waves into the pavement and measures and graphically displays the reflected signal. This can reveal voids and other defects.

The epoxy/core test, detects voids by visual and mechanical methods. It consists of drilling a 25 to 50 millimeter hole through the pavement into the sub-base with a dry-bit [[roto-hammer]]. Next, a two-part [[epoxy]] is poured into the hole – dyed for visual clarity. Once the epoxy hardens, technicians drill through the hole. If a void is present, the epoxy will stick to the core and provide physical evidence.

Common stabilization materials include [[pozzolan]]-cement grout and polyurethane. The requirements for slab stabilization are strength and the ability to flow into or expand to fill small voids. Colloidal mixing equipment is necessary to use the pozzolan-cement grouts. The contractor must place the grout using a positive-displacement injection pump or a non-pulsing progressive cavity pump. A drill is also necessary but it must produce a clean hole with no surface [[spalling]] or breakouts. The injection devices must include a grout packer capable of sealing the hole. The injection device must also have a return hose or a fast-control reverse switch, in case workers detect slab movement on the uplift gauge. The uplift beam helps to monitor the slab deflection and has to have sensitive dial gauges.<ref name="igga">{{cite web|url=http://www.igga.net/File/Minnesota-State-Aid-Concrete-Pavement-Rehabilitation-CPR-Best-Practices-Manual-_2006.pdf |title=State Aid Concrete Pavement Rehabilitation Best Practices Manual 2006 |access-date=2013-05-13 |url-status=dead |archive-url=https://web.archive.org/web/20130809234355/http://www.igga.net/File/Minnesota-State-Aid-Concrete-Pavement-Rehabilitation-CPR-Best-Practices-Manual-_2006.pdf |archive-date=2013-08-09}} Minnesota DOT</ref><ref>"Practical guidelines for CPR of Urban Roads: A compelling need for preserving city concrete streets led to the development of a methodology for scoping repairs and the undertaking of a comprehensive concrete pavement repair program in Grand Rapids, Michigan". June 2005. ''Better Roads''.</ref>

===Joint sealing===
Also called joint and crack repair, this method's purpose is to minimize infiltration of surface water and incompressible material into the joint system. Joint sealants are also used to reduce dowel bar corrosion in concrete pavement restoration techniques. Successful resealing consists of old sealant removal, shaping and cleaning the reservoir, installing the backer rod and installing the sealant. Sawing, manual removal, plowing and cutting are methods used to remove the old sealant. Saws are used to shape the reservoir. When cleaning the reservoir, no dust, [[dirt]] or traces of old sealant should remain. Thus, it is recommended to water wash, sand-blast and then air blow to remove any sand, dirt or dust. The backer rod installation requires a double-wheeled, steel roller to insert the rod to the desired depth. After inserting the backer rod, the sealant is placed into the joint. There are various materials to choose for this method including hot pour bituminous liquid, silicone and preformed compression seals.<ref name="igga" /><ref>{{cite web |url=http://www.igga.net/File/Minimize-Wheel-Slap-Keep-Your-Joints-Narrow-_2004.pdf |title=Minimize Wheel-Slap: Keep Your Joints Narrow |access-date=2010-01-06 |url-status=dead |archive-url=https://web.archive.org/web/20110723154515/http://www.igga.net/File/Minimize-Wheel-Slap-Keep-Your-Joints-Narrow-_2004.pdf |archive-date=2011-07-23 }} IGGA</ref><ref>How States Preserve Concrete Pavements: CPR pays off in extra pavement life. Better Roads. August 2005.</ref><ref>CPR brings dying pavement back to life: Georgia continues to be the leader in concrete pavement restoration, but as the word spreads other states are beginning to use this system to restore deteriorating pavements. April 1997, Roads & Bridges Magazine</ref>