SEAL COATING 101

Seal coating is generally accepted in Texas as the most cost effective way of finishing lower usage roads such as local County roads and Farm to Market roads. Done properly it provides a hard wearing, water tight surface that will typically last 15-20 years on County Roads. Water penetration is a major contributor to road failure leading to cracks and then pot holes. Seal coating protects roads from water and hence pot holes.

Before a road is seal coated it is absolutely essential that it is properly prepared. With the poor state of so many roads in Titus County, preparation is by far the longest part of the process of restoring a road. The base has to be sufficiently deep with any soft spots dug out and replaced with suitable material. In some cases entire stretches of road have to be dug up and new material added. For example fly ash is added to stabilize clay. The base also has to be rolled and graded to get the needed slopes to the sides for water to run off. The ditches also have to be cleared out and in many cases deepened. Often culverts need replacing or their size increasing to better handle floods.

Seal coating involves spreading a hot oil emulsion over the road surface, covering it with crushed rock, rolling the rock into the oil and letting it set up. The process can only be carried out when minimum nighttime temperatures are above 50 f degrees. Below that temperature the oil solidifies too quickly and the crushed rock does not get properly embedded into the surface. This limits seal coating pretty much to May through mid September unless we get a warm spring or fall.

To seal coat a suitably prepared road, all 15 road hands are involved, as well as the Road Engineer and his assistant It is an involved process with lots of equipment and material to manage and absolutely depends on teamwork. The road hands are typically deployed as follows:
1 running the power rotary broom to clean the road base surface.
1 running the oil distributor that spreads the oil on the road
2 driving hot oil trucks from the Ergon plant near Home Depot out to the job site and back in a relay.
2 on the chip spreader with one driving and one hooking up dump trucks to it to refill it.
6 driving and refilling dump trucks with crushed rock again in a relay.
1 driving the 9 wheel pneumatic roller used to embed the crushed rock into the oil.
2 directing traffic, one on each end of the road being worked on.
Many times this past summer the road crew was working 10 hour days to maximize how much road they could seal once everything was set up.

The materials for applying a single layer of seal coat on a Titus County road, 16 feet wide (many are narrower) cost $14,000. Many of the roads seal coated so far have actually had two layers applied, as they are high usage roads and we need to be sure they will last 15-20 years. The double layer runs $28,000 per mile. For comparison to apply a thin 1” layer of cold mix asphalt the material cost is $40,000 per mile based on $77 per ton.

Cold mix was primarily what the Commissioners used to patch up our roads the past 15+ years. Not only is it expensive, it is also not fully waterproof and can quickly deteriorate with substantial pot holes appearing in less than 5 years, which require more patching, a self defeating cycle that we had to break out of. The primary reason why our roads are in such poor shape is because from roughly 2000 to 2016 the Commissioners forgot how to cooperate and run seal coating operations. In the last century they did manage to cooperate and do some seal coating, but never with a plan to get all the Titus County roads seal coated. We now have such a plan.

How long it takes to get all nearly 400 miles rebuilt and seal coated really depends on how much resources we want to provide to the Engineer. Right now his biggest constraint is preparing the roads with the slow and unreliable Bomag road re-claimer now the weakest link. In 2018 there was definitely a learning curve and no roads were finished being seal coated until the end of June. In all about 16 miles were seal coated and another 6-8 miles were repaired with cold mix, before the seal coating process was up and running. In 2019 with a full summer season and a trained road crew ready to roll, we can reasonably expect 30-40 miles to be seal coated. It will take getting over 40 miles seal coated annually to really dig into the backlog of unacceptable roads.