Long-Life Surfaces for Busy Roads
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Contents:
- VIACOURSE® Single Layer Asphalt;
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- Long-life surfaces for busy roads.;
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Resistant to Deformation. High Stiffness. Offers higher stiffness and resistance due to larger aggregate size. Better Heat Retention. Rapid Replacement. Excellent Durability. Due to ease of application Viacourse offers reduced contract time and cost. Reduced Disruption. Reduced Carbon Footprint. Helps to reduce carbon footprint due to lower fuel requirements during paving. Conserves Resource. Find out more about the applications Viacourse asphalt can be used for. Rural Roads. Urban Streets. Perfect for village, town and city streets due to high durability.
Housing Estate Roads. Blasting is not frequently used to excavate the roadbed as the intact rock structure forms an ideal road base. When a depression must be filled to come up to the road grade the native bed is compacted after the topsoil has been removed. The fill is made by the "compacted layer method" where a layer of fill is spread then compacted to specifications, under saturated conditions.
The process is repeated until the desired grade is reached. General fill material should be free of organics , meet minimum California bearing ratio CBR results and have a low plasticity index. The lower fill generally comprises sand or a sand-rich mixture with fine gravel, which acts as an inhibitor to the growth of plants or other vegetable matter. The compacted fill also serves as lower-stratum drainage. Select second fill sieved should be composed of gravel , decomposed rock or broken rock below a specified particle size and be free of large lumps of clay.
Sand clay fill may also be used. The roadbed must be "proof rolled" after each layer of fill is compacted. If a roller passes over an area without creating visible deformation or spring the section is deemed to comply. Geosynthetics such as geotextiles , geogrids and geocells are frequently used in the various pavement layers to improve road quality. These materials and methods are used in low-traffic private roadways as well as public roads and highways. The completed road way is finished by paving or left with a gravel or other natural surface.
The type of road surface is dependent on economic factors and expected usage. Safety improvements such as traffic signs , crash barriers , raised pavement markers and other forms of road surface marking are installed. When a single carriageway road is converted into dual carriageway by building a second separate carriageway alongside the first, it is usually referred to as duplication , [42] twinning or doubling.
The original carriageway is changed from two-way to become one-way, while the new carriageway is one-way in the opposite direction.
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In the same way as converting railway lines from single track to double track , the new carriageway is not always constructed directly alongside the existing carriageway. Like all structures, roads deteriorate over time.
Long-life surfaces could substantially cut the costs of road works, including the delays they cause, especially on congested routes with heavy. The issue of prolonged service life of road pavements has been a key concern The Long Life surfaces for Busy Roads report is the result of over two years of.
Deterioration is primarily due to accumulated damage from vehicles, however environmental effects such as frost heaves , thermal cracking and oxidation often contribute. Potholes on roads are caused by rain damage and vehicle braking or related construction works.
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. 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 pavements are designed as perpetual pavements with an expected structural life in excess of 50 years. 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. 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. These measurements include road curvature , cross slope , asperity , roughness , rutting and 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 sealingfo, micro milling or diamond grinding and 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.
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.
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. 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 CPR methods including patching and diamond grinding.
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- References.
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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 cementitous grout or polyurethane mixture through holes drilled through the slab. 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 loss of support exists. Visual inspection is the simplest manner to find voids.
The Porous Road Less Traveled
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 utilized 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. Ground penetrating radar pulses electromagnetic waves into the pavement and measures and graphically displays the reflected signal. This can reveal voids and other defects.
Introduction
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.
Long-Life Surfaces for Busy Roads
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.
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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. Also called joint and crack repair, this method's purpose is to minimize infiltration of surface water and incompressible material into the joint system. 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.