How Heat Affects Parking Lots in Houston
When Houston makes weather headlines, it is typically due to heat, flooding or hurricanes. This past summer, the heat was front and center with one record after another getting smashed. 2023 will officially go down as the hottest Houston summer of all time, and while relief is finally arriving (to some extent) for the city, the situation is about to get worse for its asphalt and concrete pavement.
Shrinking, Swelling, Subsidence: What Lies Beneath Houston Pavement
Harris County has withered under drought for months, and that means profoundly dry soil in and around the city. That’s bad news for asphalt and concrete.
During an extreme drought, trees, bushes, grasses, and other vegetation work harder to pull moisture out of the ground. This accelerates soil dehydration further. As soils dry out, they shrink and subside, opening up internal voids that weaken the ground’s load bearing capacity.
Most Houston parking lots are adjacent to vegetation of some kind. For months, that vegetation has been pulling moisture out of the ground that those parking lots sit on top of. As a result, the ground is shrinking, shifting, and subsiding under Houston’s pavement, opening up cracks and potholes that are bad enough as is. But as we’ll see, this surface-level damage is only the first stage in a weather cycle that will quickly damage the pavement.
How Rain Affects Houston Parking Lots During a Drought
Houston’s climate is closer to a swamp than a desert, but the summer of 2023 didn’t seem that way. However, the weather eventually turns, and rains are back in the forecast for Houston. With those rains following extreme heat, pavement damage will follow.
Following high temperatures and soil shrinkage, surface defects will quickly appear on parking lots all over the city. When the rain returns, water immediately enters those cracks and penetrates deep into subsurface pavement layers, and when water contacts concrete or asphalt in this way, rapid deterioration sets in. Here’s how:
- Asphalt – Asphalt is held together by binders that act like glue. The binders promote adhesion between asphalt layers and between the aggregate itself. If this binder fails, the asphalt will embrittle and lose its flexibility. Its load bearing capacity comes next, and surface-level flaws will soon penetrate through the pavement’s entire vertical structure. Soil shrinkage and shifting exacerbate this effect.
There’s no simple way to repair asphalt damage to this degree. The most realistic solution, and most expensive, is full depth reclamation or replacement.
- Concrete – Water doesn’t chemically attack concrete as aggressively as it does asphalt, but it will still cause ongoing deterioration on a chemical level. Reinforced concrete, however, is susceptible to corrosion via water intrusion, and this can lead to a dangerous situation if the rebar inside the concrete fails.
Most Houston parking lots are not constructed with reinforced concrete, but water intrusion is still a problem. On its own, water will erode away the cement and aggregate inside the concrete, resulting in structural issues. However, water rarely flows on its own, as it carries plenty of small aggregates with it. If these incompressible materials are washed into cracks and potholes, they will affect the parking lot’s ability to expand and withstand thermal stresses – resulting in yet more cracking.
What’s even worse is if water soaks the base beneath the concrete, it will cause it to expand and shift. This can fracture the concrete and cause uneven spots to form.
The important point is this – when areas undergo rapid drought/rain cycles, concrete and asphalt parking lots are threatened, but there is a solution.
Protect Pavement from Water Damage Now with Preventative Maintenance
The best course of action property owners can take with their pavement is to inspect it regularly. At the least, the pavement should be inspected following heavy precipitation, especially if it follows an extended period of dry and hot weather. Ideally, property owners should have a trusted pavement contractor inspect their concrete or asphalt in the wake of extreme weather. Pavement professionals are best equipped to identify potential sources of parking lot damage and can recommend a pavement preserving course of action.
When inspecting asphalt or concrete, pay close attention to the parking lot’s edges. It’s along the pavement’s perimeter where signs of weather-related damage are most common. For example, when soils dehydrate and shrink, they often pull away from pavement and leave a void between the pavement’s edge and adjacent vegetation. This is just one potential weak spot in the parking lot’s structure.
Cracks, potholes, uneven pavement, surface aggregate loss, raveling, spalling – these are all common when extreme temperatures and precipitation come into play.
Aside from inspections and consultations, what can be done to rescue a stressed parking lot?
- Crack and joint sealing – Once large cracks open up in the pavement, chances are they will widen and spread with time. Prompt crack sealing services can protect these gaps from water intrusion, using a formulated sealant that consists of asphalt, rubber particles, polymers, and fillers. Once applied to the crack, the sealant will cure and flex like asphalt, preserving the pavement’s ability to flex without reopening the seal.
A similar approach can be taken with exposed pavement joints. A polyurethane compound is typically used to seal up joints, which can also fail due to excessive heat and soil shrinkage.
- Sealcoating – Pavement sealing is an inexpensive, simple way to protect an asphalt or concrete surface. Surface sealants can be spray-applied using a skid, so the process can often be handled in less than a day. Once applied, pavement sealants act like a protective membrane, defending the surface from UV radiation, weather and wear.
Sealcoating is particularly important for asphalt because the tacky substances in sealcoat help bind asphalt aggregates together and provide additional resistance to wear and impact. As such, asphalt sealcoating is recommended at least every other year.
- Overlaying – Overlaying isn’t always an option, but if the parking lot’s base remains in good shape, then overlaying can be a cost-effective way to restore the pavement’s appearance and surface integrity.
During an overlay, the existing pavement’s surface is milled down an inch or two. If any base defects are identified at this point, they are repaired and the underlying soils stabilized.
Once the underlying pavement is ready, a new layer of asphalt is applied to its surface. This can be done whether the existing pavement is made from asphalt or concrete. In both cases, an overlay can extend the parking lot’s life by a decade or more, while restoring its performance and appearance. Better yet, total pavement replacement, and its associated expense, is pushed down the road.
The goal with preventative maintenance or prompt repairs is to minimize the cost of pavement work. It’s been proven time and again – using data from state transportation agencies – that every dollar spent on pavement maintenance will save several dollars’ worth of repairs in the medium to long term. It’s tempting to put repairs off as long as possible, but it’s a gamble that property owners can’t go back on if severe parking lot damage quickly emerges.
Don’t Let the Houston Heat and Rain Ruin Your Pavement and its Value
A damaged parking lot is a liability for property owners. It can damage vehicles, impede traffic, cause downtime, pose an injury risk, ruin a property’s appearance, and generally make life difficult for facility managers and owners.
Stemming off any parking lot damage is worth the investment, and this damage tends to be more widespread and severe in the wake of severe weather events. Houston is no stranger to weather events, and recent heat waves are putting parking lots all over the city at risk.
If your organization owns or operates parking facilities (or any large pavement structures), consider bringing in a proven Houston pavement contractor to inspect your concrete or asphalt. A proper inspection of the pavement ensures that any weaknesses in your parking lot can be resolved before more expensive repairs are required.
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