Asphalt
From CollabLandWiki
New Zealand
Manufacturing / extraction processes
Asphalt or ‘Asphaltic Concrete’ is structurally similar to concrete however cement is replaced with bitumen. Asphalt is the by product of processing crude oils this is called Petroleum Distillation Residue. When everything that is of value is removed the leftovers are then made into asphalt. Man made asphalt consists of hydrogen, carbon and with minor proportions of nitrogen, sulphur and oxygen. Naturally occurring asphalt (Brea) contains mineral deposits.
The Asphalt cement is then added to a combination of approximately 95% stone, aggregate, sand, or gravels to create Hot Mix Asphalt. For hard use areas such as highways, roundabouts, intersections and corners Open grade asphalt is used this provided better skid resistance. For areas such as footpaths, driveways, urban roads and tennis courts Dense grade asphalt is used as it gives a smoother finish. The density of the asphalt depends on the size of stones use these sizes range from 400 microns to 5,10 or 20mm. The Asphalt is mixed at a temperature of 154 to 160°C. This Hot Mix is then packed onto a truck and delivered to the construction site where it is unloaded, spread and pressed all before it cools below 120°C.
Before the asphalt is laid the base is carefully prepared. Usually a few days in advance. Just before the asphalt is laid a tack coat is applied to the base so that the asphalt will sick to the base.
If the asphalt is being laid by hand it spread out and levelled with lutes or rakes and then compacted with rollers and plate compactors. Water is used on the equipment to stop the asphalt sticking to the them.
There are two asphalt manufacturing plants in Wellington. One in Belmont owned and run by Fulton Hogan and one in the Ngauranga Gorge owned by Works Infrastructure.
There is also rubberised asphalt that is made from recycled car tyres. It has been used in America. It isn’t a very common technique as it tends to be most costly than normal asphalt. It also has a higher chance of separating because of the weak interaction between the asphalt and the rubber. Where as normal asphalt has a 2 to 4%.
Material properties
Asphalt was originally sourced from Lake Asphalts in Trinidad where natural deposits of asphalts occur. Though it is now made through artificial processes.
Asphalt is a mixture of hard materials such as rock or aggregate,bitumen (obtained from the distillation of crude oil, acts as a binder of material) sand and gravel.Common aggregate or asphalt particles are sized from 400 microns to 200mm depending on the type of asphalt considered. Asphalt has to be laid at warm temperatures and it is heated to ensure that a good bond is produced by the mix.This is done at asphalt plants and then transported in trucks designed to maintain heat. A variety of aggregate sizes and amounts of sand, binders and air voids are used to create asphalt for a variety of needs and surfaces. These are detailed in the section 'format and finish of materials' below. Different colour finishes can be applied once the asphalt has been laid in several applications of seal.
Asphalt has a smooth surface and produces a low road noise. These main qualities lead to the uses of asphalt being common place in roads, footpaths and intersections producing a smoother surface. However dense asphalt (a particular mixture of materials) has low skid resistance in wet conditions meaning that it is more likely to be used on flat straight roads than winding, frost prone or steep surfaces. Whilst dense graded aggregate is commonly used in intersections, highways, corners and main roads as it offers better skid resistance.
Format & finish of materials
The are several ways to finish asphalt
•OPEN GRADED ASPHALT - which has a high percentage of air voids and small amount of fine aggregate for high speed areas not including intersections
•STONE MASTIC ASPHALT - a gap graded course aggregate for low speed areas
•FINE GAP GRADED ASPHALT - which is easily compacted and designed for low speed roads because it is less dense
•TACK COAT - a thin layer of bitumen which is applied to bond the layer of road to the layer beneath
•CHIP SEAL - when chips are stuck to a prepared base with bitumen solution, it is a harder and rougher surface than hot mix asphalt
•SYNTHETIC COLOUR FINISH - there are several ways to apply colour to an asphalt surface; it can be covered with a synthetic in two coats; applying a coloured aggregate during chip sealing; using coloured slurry surfacing; by adding a colour aggregate or coloured pigment to a conventional bitumen in hot mix asphalt
•RESIN - asphalt can be finished with a resin based and fibre reinforced decorative surfacing
Common fixing methods
It is common for extensively used foot paths and roads to develop pot holes. These are fixed by first cleaning of the loose debris and lined with a water barrier sheet and a reinforcing mesh and preferably the mesh is reinforced with reinforcing rods woven through the mess or placed over at forty-five degree angles. The water barrier, reinforcing mesh and reinforcing rods are preferably made from recycled plastic. The hole is then filled with hot asphalt mix.This mix is the same that has been used on the rest of the foot path or road. It is prepared in the same way but just transported in a smaller quantity. The mix is then compacted by a roller which is chilled with a cryogenic substance such as liquid nitrogen. Or the cryogenic substance is poured directly onto the mix.
Durability and maintenance requirements
Asphalt is said to have a life span of 25 years but many asphalted areas deteriorate in as little as 10 years because of poor maintenance. Asphalt should be checked every two years as it is placed in locations where is absorbs maximum abuse, as soon as its placed it begins deteriorating. Forces above and below the surface attack asphalt and slowly degrade it. Water below the surface makes clay expand, washes away the dirt and erodes the rock supporting asphalt so when heavy vechicles come into contact with it, it slowly weakens. When cracks appear they should be filled with a rubberized material to prevent water entering and potholes forming. Another factor is ultra violet rays from the sun which oxidize the organic matter making it turn gray and leaving it to be washed away by water. Sealing coats should be applied every three years to seal hairline cracks, stop the asphalt from drying out and provide protection from decay. To help maintain the life of asphalt you should also avoid oil drips, excessive dirt and grael build up. Asphalt requires maintanance and care to achieve maximum life.
Factors which influence the durability of asphalt are
• Preparation of the area to be asphalted
• Presence of petroleum products, such as oil and petrol, which will break down the asphalt bond
• Asphalt concrete reacts with oxygen which will eventually lead to a break down in the bonding.
After pouring it takes one-two months for for asphalt to be at its maximum strength. Regular resurfacing and repair will help reduce the occurance of these factors and make the asphalt more durable to wear and tear or decay.
Life-cycle / recycling possibilities
Natural elements such as the sun, oxygen and water lead to a breakdown in the bond of asphalt material over time. This occurs because particles in asphalt will reform in extremes of heat. Traffic overload can also limit the life cycle of Asphalt eroding the surface and contributing to cracks and or uneven surfaces. This is known as thermal or fatigue cracking. Without proper maintenance asphalt can have a life cycle of only 10 years. Within areas where surfaces are highly used such as inner city intersections or air port runways asphalt can be cracked and pushed into the ground by heavy traffic, small parts of these areas need constant repair and maintenance in order to achieve a life span of 20 years or more.
Asphalt is reused a number of times as it can be reheated and redistributed. Eighty percent of the asphalt pavement in America is reused in new projects (http://e.wikipedia.org/wiki/Asphalt). This number is not as high in New Zealand however it is recycled and reused in some cases.
In New Zealand trails are being undertaken with a mixture of recycled glass and asphalt called “Glassphalt” (http;//archived.ccc.govt.nz). This combination is thought to prolong erosion rates of asphalt from natural elements, as the glass mixture reflects heat. Trails are also being undertaken in america where recycled tyers are being considered in the design mix. However this has led to higher erosion and lower efficiency levels.
List of manufacturers / contractors / suppliers
ASPHALT BITUMEN AND TAR SUPPLY
•FULTON HOGAN ASPHALT PLANT, Hedben Cresent Belmont, PH: (04) 565 0127, FAX: (04) 565 3182, [1]
•GREENSTONE CONCRETE AND ASPHALT LTD, PO BOX 38362 Petone, PH: (04) 566 0890 or 027 443 0791
•HOROKIWI QUARRIES LTD EMULSION DIVISION, PO BOX 38037 Wellington Mail Centre, Horokiwi Road Petone, PH: (04) 569 2839, FAX: (04) 586 3440
•WORKS INFRASTRUCTURE LIMITED, Asphalt Plant, Ngauranga Gorge Ngauranga, PH: (04) 477 5816, FAX: (04) 477 4930
ASPHALTERS
•ACCESS ASPHALT, PH: (04) 972 7704 or 027 421 7741
•AIDAN KELLY DRIVEWAY LANDSCAPING, Aiden and Carol Kelly, PH: (04) 234 8604
•ALEXANDER CONTRACTING CO LTD, 112-116 Whakatiki Street Upper Hutt, PH: (04) 939 9379
•ANGUS ASPHALTS, 6 Bull Ave Wainuiomata, FAX: (04) 564 7033
•AWATERE ASPHALTS LTD, 127B Martin Street Upper Hutt, PH: (04) 971 6699
•CLAMP PAVING AND CONTRACTING LTD, Contractors and Manufacturers, PH: 021 532 699
•CONTOUR ASPHALTS LTD, PO BOX 46-006 Lower Hutt, PH: (04) 567 0285, contourasphalts@paradise.net.nz, [2]
•DRIVEWAY CONSTRUCTIONS, PH: 027 661 2426
•FULTON HOGAN LIMITED WELLINGTON, Marine Parade Petone, PH: (04) 568 5092
•HIGGINS CONTRACTORS WELLINGTON, PH: (04) 472 8460, FAX: (04) 499 1176, contractors.wn@higgins.co.nz, [3]
•HQ ASPHALTS, Kilbirnie, PH: (04) 977 8090 or 021 365 244, FAX: (04) 976 8090, info@hqasphalts.co.nz
•JOHNSONVILLE ASPHALT AND GENERAL CONTRACTORS, PH: 027 446 8683, FAX: (04) 2366230, HOME PH: (04) 236 6230
•KEVIN PURSER ASPHALTS, 9 Gough Street Seaview, PH: (04) 566 6912, FAX: (04) 566 6913, kpursercontracting@paradise.net.nz
•MORGAN CONTRACTORS LTD, PH: (04) 564 7473 or 021 732 511, FAX: (04) 564 7472, morgan.contractors@xtra.co.nz
•OLDFIELDS, 199 Gracefeild Road Seaview, PH: (04) 568 2148
•P AND D ASPHALTERS LTD, 48 Kemp Street Kilbirnie, PH: (04) 387 4012
•POTHOLE PROFESSIONALS LTD, PH: (04) 977 8090
•S AND R ASPHALTS LIMITED, Upper Hutt, PH: 027 440 2405
•WELINGTON ASPHALT CO LTD, PH: (04) 388 9174
For further suppliers in New Zealand see http://www.yellowpages.co.nz
Product information / specifications
Product Information/Specifications
Asphalt has a variety of different finishes and design mixes for small and large areas. These are listed above as well as being widely available in New Zealand. Specialised asphalt companies such as HQ asphalts are available or larger more commercial construction companies such as Works Infrastructure also specialise in asphalt laying and supply.
Asphalt is usually made at a location close to a quarry where aggregate can be easily accessed. It can be laid by machine or by hand. The site visit in which we took the process was done by hand with rakes, lutes (rods similar to rakes but with a solid surface for pushing material into place) and then compacted with rollers using water to prevent material sticking.
There are two types of asphalt which occur most frequently in the New Zealand environment and market; Open graded and dense graded. Open graded asphalts have a number of different design mixes; Friction Course, Macadam and stone mastic asphalt.Open graded asphalts are designed to provide better skid resistance in wet and steep conditions.
Examples of uses in New Zealand for Open Graded Asphalt include:
• Highways, roundabouts intersections and corners
Examples in New Zealand for Dense Graded Asphalt:
• Foot paths, Driveways, urban roads and tennis courts.
Precedent 1
User:Sally Bishop Asphalt in Landscape Architecture, Wellington Area.
Asphalt in the urban landscape, a smooth surface on which to travel. Some examples:
The Duck Pond Pavilion in the Wellington Botanical Gardens displays a use of asphalt providing contrast in texture and colour. The smooth surface of the asphalt laid with textured concrete provides a traditional break and detailing in the surface surrounding the pavilion.
The asphalt surface which moves from the dense planting of native forest to street level segregates the viewer from the material which is intended to be experienced. Asphalt may have been chosen for its ability to provide a utilitarian surface for all users i.e. pedestrians with strollers and a suitable surface for wheelchairs as well as being easy to lay in small areas.
Oriental bay is a central recreational area for the city of Wellington. The space between the sea wall and road provides a corridor or promenade for pedestrians to enjoy scenery, commute and exercise between various waterfront attractions, i.e Waitangi park to the Ice cream shop!
Oriental bay was designed with the intention of creating 3 “smaller beaches” (http://www.nzila.co.nz/awards2004/supreme_isthmus.doc) within one. Asphalt was chosen as its material qualities give a “simple sweep”(http://www.nzila.co.nz/awards2004/supreme_isthmus.doc) of smooth surface from the edge of the sea wall to the kerb. This allows pedestrian traffic to go about different purposes of recreation on an uncluttered, uninterrupted surface.
The detailing by The Isthmus group for Oriental bay was chosen for its “restraint” (http://www.nzila.co.nz/awards2004/supreme_isthmus.doc). A light gravel was chosen for underneath lighting features to illuminate the contrasting colour of ground surfaces without glare. The surrounding asphalt has also been chosen for its ability to absorb light rather than reflect.
300092502
Precedent 2
175-185, Main Road, Tawa
Along the main retail end of Main Road in Tawa the foot path has been up graded. It has been an effort of the Wellington city council to make the stretch of street more appearing to the everyday shopper and also to unify it with the shopping centre in Linden. 175-185, Main Road combines the same asphalt, paving and street furniture that has been used all over Tawa.
The asphalted foot path has had pavers pressed into it to create a repetitive crossing pattern all the way along the street.
I feel that the use of the pavers with the asphalt is a good way of turning what would otherwise be a dull footpath like that was like every other footpath into something simple but spectacular. Also as the pavers can tend to get slippery when they get wet like what can happen in Cuba Street then it makes it safer only having a few pavers in selected areas especially since a lot of the population in Tawa is reasonably old.
Precedent 3
Asphalt is a quiet versatile material as it can be used in many different places and can be used in a way that it can add detail mto a landscape. Commonly used on pavements it is a simple material that can blend into the landscape. Asphalt can be found everywhere around wellington.
See also
References
http://e.wikipedia.org/wiki/Asphalt
http://inventors.about.com/library/inventors/blasphalt.htm
http://www.hotmix.org/qna/about_asphalt.html
http://www.amrl.net/Portal/publicdocs/pspdatasheets/INST%20HMG%2021-22.doc
http://www.p2pays.org/ref/11/10504/html/usa/asphalt.htm
http://www.freepatentsonline.com/5829914.html
http://www.nzila.co.nz/awards2004/supreme_isthmus.doc
http://www.findarticles.com/p/articles/mi_m1154/is_n11_v85/ai_19969627
http://www.landlord.com/asphalt_maintenance_frame.htm
Landscape Construction: A comprehensive guide to building construction within the landscape; Trevor Pringle, 2004
HQ Asphalts, PO Box 14842, Kilbirnie, Wellington (04) 9778090
Landscape Constuction, Volume 2. Roads, Paving and Drainage. C A Fortlage and E T Phillips Copy Right C. A Fortlage and E. T Phillips 1996 Gower Publishing Limited Gower House Aldershot Hampshire, England.
