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Paving Processes
Street Resurfacing

Micro-resurfacing:
Micro-resurfacing is the application of a Polymer Modified Emulsion Base. The entire road surface is overlaid (the material is placed over top of the existing asphalt surface of the street) with a 1/2 to 3/4 inch of material. The depth of material placed on the street is determined by the condition of the existing road surface. If the road surface is in fair condition a 1/2 inch of material is used. If the surface is in poor condition 3/4 inch of material is used. This process is done by a contractor working for the City of Pittsburgh. $3.09 per square yard.

The City of Pittsburgh has been using this process for two years. Using the Micro-resurfacing process should extend the life of an existing street 2 to 5 years (estimate).

Flexible Base Pavement:
Flexible Base Pavement is the application of a Polymer Modified Latex Asphalt applied at an ambient temperature (100 to 140 degrees Fahrenheit). This is a flexible material, which is mainly used on secondary, tertiary, alleys, and unimproved roads with no base. Use of this material is a very cost effective way of improving a road surface. The life expectancy of a road which uses this material is 10 to 12 years (estimate). Use of this process started in 1993, and is currently performed by contractor for the City of Pittsburgh. The City's goal is to ultimately perform this process in-house. $5.30 a square yard.

Crack Sealing:
Crack Sealing is the process where the street cracks are sealed using a Polymer Modified AC-20 liquid (AC-20 can also contain crumb-rubber recycled tires), and other types of Crack Sealing products. The sealing prevents water infiltration into the road base, thus preventing potholes. This process is performed during the early spring, and late fall months.

The current method used for the crack sealing process is Well Filling. This method fills the void of the crack up to the road surface; little or no material is placed on the actual road surface. A minimum 1 inch depth, and 1/2 inch width is need to use the Well Fill method. This is a cost effective way of extending road life 2 to 3 years. This process is currently done by a contractor for the City of Pittsburgh. $.12 per square yard

Cold Patch:
Cold Patch (Poly Pave is the industry name) is made with a Latex Modified Base Asphalt. It is an emergency cold applied asphalt which is used mainly in the winter months when production of hot mix asphalt is not feasible. It is used for pothole patching only; it cannot be used for paving an entire street. Cold Patch is a pliable material that has enough density to remain in the pothole when applied. In the summer, when exposed to the heat, it forms a solid, permanent patch. Currently, the City of Pittsburgh Asphalt Plant produces over 900 tons of cold patch material a year. This material is used by the Department of Public Works and the Water Department. $7.00 per square yard.

Paver Laid Ultra Thin Hot Mix Asphalt Overlay:
This is a very thin Hot Mix Asphalt overlay. Normally, cannot be accomplished with standard paving applications. A special process is used to essentially glue the thin Asphalt lift to the surface being paved. This process will give the same surface quality as a standard Asphalt overlay, but with cost savings of a thin Asphalt lift. To accomplish this process, an emulsion based Asphalt is sprayed over the entire paver mat width just prior to the lane of the thin hot mix overlay. The physical reaction of the hot overlay mixing with the emulsion based asphalt causes the emulsion based asphalt to glue the thin lift to the surface being paved. This makes the ultra thin lift and the surface being paved one entire pavement thickness. This process can be used on structurally sound pavements of all types. $5.56 per square yard.

The difference between the above process and Micro Surfacing, though they both are thin overlays, Ultra thin hot mix paving gives structure as well as better ride quality and longer life. Micro surfacing is more a sealing type process which extends the life of the surface being covered. This process also has some economic benefits over Ultra thin hot mix overlays.

This method of paving is being performed by contractor for the City of Pittsburgh (Novachip). 1994 was the first year the Department of Public Works was using this process.

Cold-In-Place Recycling:
Cold-In-Place Recycling is the process where four inches or more of the original asphalt street surface is ground up using the cold milling method (four inches of existing asphalt is the minimum requirement to be able to use this process). The ground up material is then mixed with a rejuvenating agent, and then replaced on the road surface using conventional paving methods. The road surface is then covered with 1-1/2 inches of virgin hot mix asphalt (ID2 Wearing) from the City's Asphalt Plant. The benefit to using this process is that it recycles the existing road surface expending its usefulness. This process is currently performed by a contractor working for the City of Pittsburgh.

 

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