Surface treatments are applied to restore texture and weatherproofing (including protection from oxidation), but do not contribute to improvement in ride or increased structural capacity. They have become an essential part of the pavement preservation program in Texas, particularly for lower volume highways.
What are the different types of surface treatments?
Relative performance of several traditional surface treatments (asphalt rubber chip seal, polymer modified emulsion chip seal, latex modified AC chip seal, unmodified chip seal, and microsurfacing) were evaluated in the TTI study 4040, Supplemental Maintenance Effectiveness Research Program (SMERP) (TTI-4040-3).
What is the “seal coat and surface treatment manual?
The “Seal Coat and Surface Treatment Manual” covers in detail the design and construction of seal coats. For new or reconstructed pavements, the seal coat can be placed on a crushed stone or chemically treated base to provide a roadway with the least expensive permanent type of bituminous surface.
What is the Texas Department of Transportation disclaimer for sulfates?
Chapter 1 — Introduction Section 1 — Disclaimer Section 1 Disclaimer The Texas Department of Transportation, in conjunction with the Texas Transportation Institute, has developed this document to serve as guidance for TxDOT personnel for soil and base treatment in sulfate-rich areas.
What is a 1 course surface treatment?
(2) One Course Surface Treatments or First Course of a Multiple Surface Treatment. Asphaltic material shall be applied by an approved distributor so operated as to distribute the material under a pressure necessary for uniform distribution.
What is surface treatment pavement?
Asphalt surface treatment is a broad term embracing several types of asphalt and as- phalt-aggregate applications, usually less than 25 millimeters (1 in.) thick and applied to any kind of road surface. The road surface may be a primed granular base, or an existing asphalt or Portland cement concrete (pcc) pavement.
What is chip seal aggregate?
Chip Seal is an application of a bituminous binder covered with an application of clean graded aggregate to an existing asphalt surface. It is also known as bituminous surface treatment or seal coat.
What is surface dressing in road construction?
What is surface dressing? Surface dressing involves spraying bitumen binder (a sticky tar-like substance) on a clean, dry road surface, over which stone chippings are spread (small, consistently-sized aggregate).
How many layers does chip and seal have?
Chip seal is an application of asphalt followed with an aggregate cover. This type of surface treatment can consist of single or multiple layers in thicknesses from 9.5 to 37 mm (3/8 to 1 1/2 in.). Two layers are referred to as a double and three as a triple chip seal coat.
When to apply seal coat in Texas?
In most parts of Texas, these conditions are most likely to occur from June through September.
What temperature should asphalt be applied?
If a polymer-modified asphalt cement is used, it shall be applied when the air temperature is above 70°F and rising and not when the air temperature is below 80°F and falling. Surface temperature must not be below 70°F. When wintertime work is allowed, the Engineer will approve the air and surface temperature for the asphalt application.
Does wind blow asphalt?
Wind also tends to blow asphalt onto passing vehicles. It is particularly important to be careful of wind direction when applying modified asphalt cements. Small “cobwebs” of asphalt are blown around and are almost invisible until they land on a light-colored vehicle.
Can you use asphalt binders in rain?
No asphalt binders should be applied during rain. If rain is in the vicinity and predicted for the area, suspension of operations should be considered. If an unexpected shower arises during operations, shut off the asphalt distributor immediately and continue placement of aggregate until all asphalt has been covered.
What is the trimming technique?
The trimming technique uses the subgrade trimmer to finish the base. Excess base is used to compact the base 1-2 inches above the blue-top level, and then the trimmer is used to cut it down to the required finish level. Then the trimmed surface is rolled. This eliminates the need to do slush rolling.
What causes streaks on asphalt?
Streaking results when alternate longitudinal strips of a surface treatment or seal coat contain different quantities of binder, due to lack of uniformity of application of the binder inch by inch across the surface. The dark streaks which exist in this condition occur when there is not enough asphalt binder to hold the cover aggregate in place, and part of the cover stone has been torn out by traffic. These dark streaks are points of weakness at which the complete seal coat or surface treatment will wear away first under traffic. Streaking can reduce skid resistance, cause vehicle steering problems, and lead to a serious reduction in the normal life expectancy.
Can binder soak into surface treatment?
Sometimes the surface on which a seal coat or surface treatment is applied is so open or porous that a large portion of the binder soaks into it. Not enough binder remains on top to hold the aggregate, and it can be easily dislodged by traffic.
What is pavement overlay?
Generally, pavement overlays are used to restore surface course functional characteristics (smoothness, friction, and aesthetics) or add structural support to an existing pavement. However, even a structural overlay should be placed on a structurally sound base.
What is underseal on asphalt?
Preparation of a primed soil/aggregate base surface or an existing asphalt-surfaced pavement for an overlay typically includes an underseal which is a sprayed application of asphalt binder (asphalt emulsion or hot applied asphalt binder) immediately covered by a layer of single-sized aggregate. The underseal provides several benefits, such as waterproofing the surface, sealing small cracks, and protecting the underlying surface from solar radiation. The application of an underseal should be strongly considered when placing a thin ACP layer on top of a flexible base. The “Seal Coat and Surface Treatment Manual” covers in detail the design and construction of seal coats.
Can tack coat be applied to damp pavement?
The pavement surface receiving the tack coat should be clean and dry to promote maximum bonding. Emulsified tack coat materials may be applied to cool and/or damp pavement ; however, the length of time needed for the set to occur may increase.
