Asphalt leveling course is defined as a layer of asphaltic concrete pavement of varying thickness spread on an existing pavement to compensate for irregularities prior to placing the surface or wearing course. Due to the low amount of sand used, the microroughness of stone mastic asphalt wearing course surfaces is almost completely achieved by the roughness of the chippings surface. Highway agencies and asphalt industry groups have different. While a wearing course of surface dressing has been known for its durability all over the world on. The work under this specification consists of the supply and application of dense graded and open graded hotmixed or warm mixed asphalt for pavement wearing courses, except for stone mastic asphalt which is addressed in specification 502 stone mastic asphalt. A waterproofing membrane shall be used below all asphalt wearing surfaces. Overlays either structural or nonstructural make up a large portion of the roadway paving done today. The new products evaluation program for lower volume local roads and municipal requirements are bound by all applicable sections of publication 408. Bridges and other spans, on the other hand, require light weight solutions with antislip properties, in which wearing courses provide. Asphalt concrete commonly called asphalt, blacktop, or pavement in north america, and tarmac, bitumen macadam, or rolled asphalt in the united kingdom and the republic of ireland is a composite material commonly used to surface roads, parking lots, airports, as well as the core of embankment dams.
Densegraded mixtures utilized for thin lift overlays are often called no. The purpose of tack coat is to form a bond between awc and abc or concrete slab. The structural concrete deck in a two course deck system uses epoxycoated or galvanized reinforcement. The bonded wearing course consists of a warm polymer modified asphalt emulsion bond coat followed immediately with an ultrathin hot mix asphalt wearing course. The costs and benefits of wearing courses differ per application. The mastic asphalt industry a global perspective march 20 page 3 of 30 the mastic asphalt industry a global perspective 1. These are dense graded asphalt, stone mastic asphalt and open graded asphalt. Resurfacing is the placing of one or more courses of hot mix asphalt over an existing hard surface pavement. Pdf performance of asphalt concrete wearing course acwc. Bishara the alabama highway department does not permit the use of limestone coarse aggregate in asphalt wearing courses because of potential longterm skid resistance problems.
A number of technical manuals have been produced by sabita, covering the selection, handling and use of bituminous materials in a wide range of applications. The wearing course transfers and distributes traffic loads to the base course. From the operational standpoint, the asphalt surface provides a wearing course to prevent material loss or dislodging e. Spread the hot asphalt mix over the surface of tack coat by automatic asphalt paver as per the necessary profile and thickness. Asphalt concrete wearing course acwc is a continuously graded mixture with small maximum particle sizes.
Pdf demands on natural aggregate materials for road pavement can be reduced by utilizing reclaimed asphalt pavement rap. Basics of prime coat and tack coat in road construction. According to 1, a poroelastic road surface is a wearing course for roads with a. The supply and laying of textured high stress resistant type asphalts, such as. Optimizing gradation design for ultrathin wearing course asphalt. During the first 24 months after the actual completion date. The need for an asphalt layer is mainly dictated by operational and structural considerations. Method statement for asphalt paving works civil engineering. The hot mix asphalt concrete material shall not be accepted unless it is covered with tarpaulins until unloaded. The wearing course shall consist of 10 mm nominal size asphalt to provide a finished compacted surface course of 30 mm minimum thickness. Asphalt concrete receiving inspection wearing and binder course. Powersweep the surface and dispose of asphalt millings offsite. Section 5 covers issues involved in the selection of wearing course materials for longlife roads.
It is similar to full depth asphalt except that a layer of granular material is placed on the subgrade first. Ultra thin bonded wearing course the maryland asphalt. Evaluation of alabama limestone aggregates for asphalt wearing courses prithvi s. The mastic asphalt industry a global perspective final. The two most common asphalt wearing courses have a nominal maximum aggregate size of 9.
Wearing course shall be placed in one layer above the bituninous base course and one coat of tack coat shall be applied between bituminous base course and wearing course. Ogfc, stone matrix asphalt sma, and ultrathin bonded wearing course utbwc. Ideally, existing nonstructural wearing courses should be removed and, if needed, underlying pavement repaired prior to placing a new asphalt wearing course. Wearing courses must not deviate below a 3m straight edge by more than 6mm where traffic speed. The supply and laying of open graded porous asphalt ogpa. Loose asphalt wearing course should be removed and replaced, and potholes and localized failures repaired. Hma pavement mix type selection guide introduction background our nations roadway system is critical to our economy.
Guidelines for the use of thin layer hotmix asphalt wearing course on low volume roads preface the purpose of this manual is to present a set of general guidelines to assist clients, consultants, paving contractors and asphalt manufacturers to design, construct and manage the quality of thin wearing course layers of hotmix. In some cases it may be more practical to overlay over the existing layer. Generally, the existing pavement should be structurally sound, level, clean and capable of bonding to the overlay. Consideration should be given to an sma, oga or a smaller stone sized dense graded asphalt as the wearing course. Contact your district municipal services representative when you have a. Stone mastic asphalt sma is a stoneonstone like skeletal structure of gap graded aggregate, bonded together by mastic, which actually is higher binder content, filler and fiber to. The tack coat is spray applied immediately prior to the application of the wearing course to produce a durable wearing surface that can be opened to traffic. The scope of work of this method statement is to describe the responsibilities of personnel involved, execution procedure, safety factors and documents to be recorded for asphalt paving works. Among the requirements of stone aggregates used to produce asphalt. In order to use a product or process in publication 447 an approved ms329 project approval form is required. Chapter 11bonded wearing course november 21, 2007 11. Cost comparison between stone mastic asphalt and asphalt.
This specification sets out the performance requirements for the following types of asphalt as wearing courses. A good wearing course is necessary for the protection of flexible pavement to make it durable. Asphalt rubber applications asphalt rubber is the process of adding recycled, crumb rubber to hot mix asphalt called dry process or the asphalt binder called wet process to modify the final mixture difficult to use in densegraded mixtures due to residual crumb rubber best used in gapgraded type mixtures sma and ogfc. Asphalt paving method statement method statement hq. Scope this specification sets out the performance requirements for the following types of asphalt as wearing courses.
The composition of the old wearing course has first to be determined, so that the added virgin material. Evaluation of alabama limestone aggregates for asphalt. Guidelines on construction and maintenance of porous. The wearing course serves several functions and no material is ideal for all situations.
The degree of surface preparation for an overlay is dependent on the condition and type of the existing pavement. Description this work shall consist of providing and placing item 415. A proposal for asphalt wearing course specification in palestine. Hot mix asphalt hma pavements constitute a large part of our nations surfaced roads.
For example, wearing courses are relatively more expensive than asphalt. A bonded wearing course bwc is a gap graded, ultra thin hotmix asphalt hma mixture applied over a thick polymer modified asphalt emulsion membrane. Notes to the performance based specification for hotmix. For roads in the construction categories sv, i and ii and for roads in the construction category iii with special. Pdf durable wearing course for bituminous pavements.
Its mixture of mineral aggregate, filler and bituminous binder forms an interlocking structure that contributes to pdf 3455303 design guide. Performance based specification for hotmix asphalt wearing. Mastic asphalt is a mixture of bitumen, limestone, sand and coarse aggregate which are heated together in a sequential manner to form a homogeneous suspended composite material and laid on as desired. Asphalt mixtures have been used in pavement construction since the. Design of longlife flexible pavements for heavy traffic. Porous or permeable friction courses pfc are hot mix asphalt mixtures placed at the surface of a pavement structure in a thin layer to produce several benefits for the traveling public in terms of safety, economy, and the environment. Tandem roller shall follow the laying operation to carry out breakdown rolling up to a temperature of 110 120. Specification 504 asphalt wearing course 0410112 issued 22052017. Which tmr projects have warranty agreements that require the contractor to warrant the asphalt paving work for longer than 90 days. Dense graded asphalt 20 mm is not to be used as a wearing course as it has a higher probability of deformation and permeability. Paver placed surface treatment consists of a polymer modified asphalt emulsion coat followed immediately with a thin hot mix asphalt wearing course. It is a sacrificial wearing course consisting of an aggregate with relatively.
The amount of recycling of reclaimed asphalt ra in new asphalt pavements has grown up to the point that it is no longer. The wearing course shall be evenly placed by mechanical spreader on a clean base in a manner that it does not become segregated. Asphalt can be mixed with cork, sponge or rubber to create more resilient surfaces or with crushed stone to produce a hard or more porous surface. As you may or may not know, an asphalt pavement section or structure is made up of multiple and different asphalt layers lifts or courses. Mix design considerations for asphalt wearing courses with high reclaimed asphalt content conference paper pdf available june 2015 with 2,036 reads how we measure reads. Bonded wearing courses are constructed using polymermodified or rubber binders and gapgraded or opengraded aggregates.
The layer between asphalt base course abc and asphalt wearing course awc is called tack coat. Method statement for asphalt paving works are given below. Did the asphalt supplied to those projects cost more. Compact the mix as soon as possible after spreading the material. Asphalt pavement is composed of the following two layers, the wearing course and the base course. Existing wearing courses that have deformed or become brittle may, within limits, be modified to overcome these deficiences. The high binder content seals the underlying road thereby protecting it from water infiltration and slows down the aging process. Hot mix asphalt pavement design guide the maryland asphalt association,inc. Description of the product mastic asphalt ma is a dense mixture consisting of coarse aggregate, andor sand, and or limestone fine aggregate, andor filler and bitumen, which may contain additives for example. Tack coat is also applied between the concrete deck slab of bridges and awc laid over it, or concrete slab of rigid pavement on which awc is to be laid. Initial field validation of poroelastic pavement made with.