Asphalt has excellent waterproofing, flexibility, and adhesive properties to bind and hold the aggregates in the pavement, asphalt has been used extensively for paving and road construction. Prior to the advent of asphalt as a paving material, roads were constructed by spreading graded aggregates over a road bed. These roads worked well as long as the stones remained in place and stayed dry.
The primary reason to sealcoat an asphalt pavement is to protect the pavement from the deteriorating effects of sun and water. When an asphalt pavement is exposed to sun, wind and water, the asphalt hardens, or oxidizes. This causes the pavement to become more brittle. As a result, the pavement will crack because it is unable to bend and flex when exposed to traffic and temperature. Sealcoat combats this situation by providing a waterproof membrane which not only slows down the oxidation process but also helps the pavement to shed water, preventing it from entering the base material.A secondary benefit of seal coating is an increase in the surface friction it provides. This is accomplished by the additional texture the cover aggregate adds to the pavement. With time, traffic begins to wear the fine material from an asphalt pavement surface. This result in a condition referred to as raveling. When enough of the fine material is worn off the pavement surface, traffic is driving mostly on the course aggregate. As these aggregate particles begin to become smooth and polished, the roadway may become slippery, making it difficult to stop quickly. Asphalt sealcoat increases the pavement texture and increases the surface friction properties.
What sealcoating will not do: Compensate for pavement defects. They are intended as a protective coat; not as crack filler or leveling material. Sealer is only as good as the asphalt pavement to which it is applied. Prevent the cracking of bituminous pavements, which are caused by excessive voids, poor mix stability, insufficient compaction, poor drainage, or low use areas.
What Sealcoat will do: By applying asphalt sealer to sound pavements, constructed with proper designs and materials that meet the climate and usage requirements of the pavement and are properly constructed over a sound and well-drained base. When the sealer is applied over anything less, any cracks that will occur will be magnified by the sealer's uniform textured appearance. Asphalt pavements should be on a good maintenance program.
Spraying Method vs. Brush Applied Method: Spraying on of sealcoat is general reserved by Vitale Asphalt Maintenance for extremely long driveways and for commercial properties that would be too big to brush on. Using a brush to apply the sealcoat leaves more sealcoat on the surface this allows for uniform application, (no shadows, puddles, or missed areas), no chance of sealcoat ending up on house or landscaping, grass, or street. Brushing fills in hairline, stone pock marks, and smaller cracks not filled by crack sealer more efficiently that spraying can.
How long should I stay off my driveway? The manufacturer recommends 24 to 36 hours for the coal-tar sealcoat to cure. Sealcoat will dry on most driveways within a few hours and can be walked on, but it is recommended that they not be driven on until after 24 to 36 hours.
How many coats of sealer do I need, one or two?
We reserve two coats of sealer for porous unsealed areas, high traffic commercial areas or driveways with unraveling problems. It is not necessary to apply two coats of sealer to most residential driveways that have been sealed before or that the asphalt is not porous or unraveling. Sealing is similar to painting a build up of material can create a flaking problem. Often we suggest if it is the first time the asphalt has been sealed, do one coat one year and do the second coat the next year. After that consider sealing as needed.
Naturally, these roads needed constant repair. Stone would shift under the traffic and the road’s load carrying capacity was severely damaged when it rained. The stone would absorb water, swell and lose its strength. But spraying asphalt on the surface overcame this problem somewhat. Asphalt paving technology gradually evolved and today the vast majority of all roads are constructed using asphalt as the binding material for the aggregates. Due to its waterproofing properties, asphalt protects the aggregates from absorbing water, thus preserving their strength and load-carrying capacities.
Types of Asphalt Sealcoat
Refined Coat Tar Emulsion: The most commonly used seal coats are based on refined coat tar. Coal tar is made up of very stable chemicals that are closed ring aromatic compounds. They are not affected by the destructive elements of weather.
Asphalt Emulsion Seal coats: Asphalt emulsion based coatings have gained considerable acceptance because of ease of application and lower odor and less skin irritation than coat tar sealers. We choose not to use them because they do not have the resistance to gasoline, oils fats, etc.
Our Sealcoat Mixture: We purchase our sealcoat in a concentrated form that has to be diluted 25% to 30% by volume with water and mixed with sand for proper textured appearance and non-slip properties. 2-2.5 lbs. of sand per gallon is added to all sealcoat. We purchase our sand locally from Best Sand and Gravel. The sand is clean, hard, angular and falls within a specified range of particle size gradation. Too many fine or coarse particles will detract from performance. The relative quantities of binder (asphalt emulsion or refined coal tar), clay, and fillers are crucial to the performance of the sealer. Excessive amounts of clay and fillers in the sealer formulation will produce porous cured films due to insufficient binder, and thus poor performance. Such sealcoat films tend to lack flexibility and wear prematurely. WE DO NOT OFFER EXTRA SAND FOR THIS REASON. Excessive amounts of sand or aggregate in the mix design degrade the performance in the same manner. Conversely, an excessive amount of binder (asphalt or refined coal tar) might produce tackiness under hot climatic conditions, even after the full cure.
Conditions Conducive to Longer Lasting Sealcoat:
Sealcoat is affected greatly by weather conditions, especially during construction. The ideal conditions are a warm, sunny day with low humidity. Humidity and cool weather will delay the curing time and cause the seal coat to be tender for a longer period of time making it more susceptible to damage by traffic. Rain can cause major problems when seal coating. If the asphalt binder has not cured, it can become diluted and rise above the top of the cover aggregate. After the water evaporates, asphalt may cover the entire surface causing tires to pick up aggregate or track the binder across the surface. Seal coating should never be done when showers are threatening. Asphalt to be sealcoated should also be in relatively good condition. This means that there should be little, if any, load related distress such as alligator cracking, rutting and potholes. If these conditions exist, the driveway should not be sealed unless it is repaired first.
In summary, seal coating is a good maintenance technique for pavements with the following:
What is Asphalt: Today’s asphalt pavement is a mixture of stone aggregate and mineral filler combined with 4.5% to 12% (average of 6%) asphaltic binder (asphalt cement). The strength of an asphalt pavement is directly related to the pavement design from the ground up. The asphalt pavement people see is only the "roof," so to speak, of the entire pavement. This "roof" covers a bed of graded stone aggregates of varying depths according to ground conditions as well as traffic requirements. This base of aggregate is what really carries the load of the traffic. The same theory applies to off-street parking lots or driveways. A firm resilient surface that provides a roof over the stone base will keep the pavement bed dry. It is important to have an elastic characteristic in this pavement so that it can expand and contract and still remain intact.In spite of its excellent adhesive and waterproofing properties, asphalt has some serious drawbacks that relate to its chemical makeup.
Asphalt is a very complex mixture of thousands of chemicals which are predominantly open chain (aliphatic) in structure with a considerable degree of unsaturation within their molecular structure. The open chain provides easy access to weather, salts, and chemicals to attack and disintegrate the asphaltic molecules. As the asphaltic molecules disintegrate, the asphalt in the pavement loses much of its original properties, such as binding and waterproofing.