A stone driveway is a cheap and lower carbon alternative for sidewalks and driveways.
Due to their durability, moldability, and smooth texture, asphalt and concrete are two of the most used materials in the world. In fact, concrete is the second most consumed substance in the world, second only to water. Unfortunately, the benefits of these materials come at a pretty steep cost. Currently the widespread technologies in place to develop asphalt and concrete result in large amounts of carbon dioxide emissions.
The good news is the asphalt and concrete industries seem committed to finding a solution to develop these materials without creating carbon emissions. The National Asphalt Pavement Association has announced a plan to provide net-zero pavement by 2050 while proposals such as Concrete Action for Climate’s aim for carbon neutrality by 2050 are being suggested for concrete.
2050 is quite a ways away, however, and it is important that we take action now to slow climate change by reducing the amount of carbon emissions being pumped into the atmosphere.
In this article, we will discuss the benefits and downsides to asphalt and concrete and their current best alternatives for driveways and sidewalks. I will also break down the total estimated cost of these options using the estimated life, cost of installation, and routine maintenance required.
Please note these are really just ROUGH estimates. The actual cost will depend on a number of factors such as your location, the size of the project, etc. I have used averages to provide you with a sense of what the cost would look like when using these types of materials in comparison to one another.
A breakdown of the benefits, downsides, lifespan, and estimated cost over lifespan for each material listed follows.
Benefits to Asphalt and Concrete:
Solid
Can be molded into a shape
Durable
Smooth texture
Downsides to Asphalt:
High amounts of embodied carbon as the production of asphalt produces carbon dioxide
Asphalt fumes are toxic and exposure can result in cancer, central nervous system problems, liver damage, respiratory problems and skin irritation according to the EPA
Produces toxic emissions when heated up in warm and sunny areas
Uses bitumen which is a product of crude oil
Contributes to the heat island effect- urbanized areas having higher temperatures than rural areas
Not permeable- which means water can't pass through
Downsides to Concrete:
C02 is emitted from both the energy used in the cement making process and the chemical reaction produced from the mixture when it is exposed to heat
Manufacturer uses large quantities of water
Contributes to the heat island effect in cities but less so than dark asphalt
Not permeable
Dust can cause respiratory issues
Best Current Lower Carbon Options for Driveways and Sidewalks:
Pervious Concrete
Benefits:
Reduces storm water runoff
Reduces contamination in waterways
Allows for renewal of groundwater supply
Reduces heat island effect
Uses less cement per volume than conventional concrete and can reduce a pavement's embodied carbon by almost 40%
Requires less energy to be produced than asphalt which leads to a 56-70% reduction in embodied energy at the time of installation
Downsides:
Longer curing time- 7 days vs 24-48 hours for traditional concrete
Specialized construction practices
Soil type and groundwater level need to be considered in design
Stone
Benefits:
Reduces storm water runoff
Reduces contamination in waterways
Allows for renewal of groundwater supply
Reduces heat island effect
Easy to install
Easy to maintain and repair yourself
Downsides:
Rain and snow can cause ruts and potholes
Produces more dust than other alternatives
Some types of stones can produce toxic dust such as silica
Weeds can grow in gravel driveway
More difficult to remove snow from
Cost Estimates by Material
Asphalt Driveway Cost Estimates:
Average Lifetime for properly maintained asphalt driveways - 25 years
Average Cost of Install - Estimated at $5,000
Routine Maintenance Required:
Crack Filling Once Per Year - Estimate $350 for 100 feet of basic crack filling or $8,750 over lifetime
Seal Coat every 2 years- Estimate $500 or $6,250 over lifetime
Anticipated Lifetime Cost of Asphalt Driveway - $20,000 - $5,000 for installation and $15,000 in maintenance
Concrete Driveway Cost Estimates:
Average Lifetime for properly maintained concrete driveways - 25 years
Average Cost of Install - Estimated at $6,500
Routine Maintenance Required:
Crack Filling Once Per Year - Estimate $300 or $7,500 over lifetime
Seal With Water-Based Sealer Every 2 years- Estimate $700 or $8,750 over lifetime
Anticipated Lifetime Cost of Concrete Driveway - $22,750 - $6,500 for installation and $16,250 in maintenance
Pervious Concrete Cost Estimates:
Average Lifetime for properly maintained pervious concrete - 30 years
Average Cost of Install - Estimated at $6,900
Routine Maintenance Required:
At least annually dry vacuuming and power washing to reduce clogging- Estimate $125 for shop vac and $33 to rent electric power washer for 4-hours or $1,115 over lifetime
Repair areas of surface raveling. It was very difficult to find information on how often these types of repairs will have to be made. It seems very dependent on how good the initial installation was. I have estimated that an area of 25 sq ft will ravel enough that it needs to be milled and reinstalled every two years -$300 or $4,500 over lifetime
Anticipated Lifetime Cost of Pervious Driveway - $12,515 - $6,900 for installation and $5,615 in maintenance
Stone Cost Estimates:
Average Lifetime for properly maintained stone driveways - 100 years
Average Cost of Install - Estimated at $1,500
Routine Maintenance Required:
Rake out periodically to keep the stones evenly dispersed - a sturdy gravel rake- $50 or $150 over lifetime assuming your rake wears out and you have to replace it a few times
Fix Potholes - Rent a compactor for $96/day- or $4,800 over lifetime. A lot of factors go into what causes potholes so the frequency could vary greatly. I am just estimating you will need to make some repairs every 2 years when you add new gravel
Add a few inches of gravel every 2 years- $700 or $35,000 over lifetime
Anticipated Lifetime Cost of Stone Driveway - $41,450 - $1,500 for installation and $39,950 in maintenance.
**Keep in mind this is over a much longer time horizon. If compared to the life expectancy of concrete and asphalt the total cost would be $11,550 as opposed to $20,000 for asphalt and $22,750 for concrete- a little over half the expense. **
Until the concrete and asphalt industries are able to provide more sustainable products at a commercial scale, I think it’s great that there are affordable alternatives you can choose. There are certainly benefits and downsides to weigh with each alternative, but for both pervious concrete and gravel, the benefits seem to greatly outweigh the downsides at this point. Knowing what you now know, if you were to install a new driveway or sidewalk or replace an old one, would you consider one of these alternatives?
Sources:
“Concrete Driveway Cost - How Much Is a Driveway? (2022) - Concrete Network.” ConcreteNetwork.com, www.concretenetwork.com/concrete/concrete_driveways/cost.html.
grupa, tom. “2021 Permeable Pavers Cost | Pervious Concrete & Asphalt Pavement Cost.” HomeGuide, 22 Feb. 2021, homeguide.com/costs/permeable-pavers-cost.
“How Much Does a Gravel Driveway Cost?” Bob Vila, 11 June 2021, www.bobvila.com/articles/gravel-driveway-cost/.
Kurt D. Smith and James Krstulovich. Pervious Concrete (TechBrief). 2012.
“Maintenance_and_Repair_Options_for_Pervious_Concrete.” Https://Www.researchgate.net/Publication/269125796_Maintenance_and_Repair_Options_for_Pervious_Concrete.
nature. “Concrete Needs to Lose Its Colossal Carbon Footprint.” Nature, vol. 597, no. 7878, 28 Sept. 2021, pp. 593–594, www.nature.com/articles/d41586-021-02612-5, https://doi.org/10.1038/d41586-021-02612-5.
Pervious Concrete Pavement Maintenance and Operations Guide.
“Pervious Concrete, the Basics.” Bay Area Pervious Concrete, www.bayareaperviousconcrete.com/pervious-concrete#:~:text=Reduce%20Embodied%20Energy%20and%20Carbon&text=Pervious%20concrete%20uses%20less%20portland. Accessed 7 Mar. 2023.
“StackPath.” Www.forconstructionpros.com, www.forconstructionpros.com/asphalt/article/21940578/asphalt-industry-commits-to-netzero-pavements-by-2050. Accessed 7 Mar. 2023.
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