Concrete and Weather Exposure

10 Jul 2021, Posted by F.A. in Tips
Concrete and Weather Exposure

Concrete is known for being a durable and long-lasting material, but the truth of this perception will vary based on the skill used when laying the concrete initially. In extreme climates, concrete can be negatively impacted even after it has dried and construction workers must take precautions to prevent weather-based problems in the future. Just like Symons forms are used to ensure the proper shape of a concrete structure, the proper ingredients and methods must be used to ensure the proper durability. In concrete, durability can be defined by the ability to resist external forces, including weathering action and other climate-related factors.

Is Concrete Waterproof?

Many weather-related concerns have to do with humidity and precipitation that may cause the concrete to get wet over time. While you may assume concrete is waterproof, that is not true- think about the musty smell after a basement floods, or the image of a footpath with broken pieces visible. While you won’t see water leak through a slab of concrete, water is able to get through the spaces between particles in the concrete. Over time, this can break the concrete down and lead to it chipping off or leaking through, which allows more water in that will cause damage more quickly in the future.

In order to be waterproof, a substance must completely prevent water from entering the material. As concrete is made of cement, sand, and gravel mixed with water, there are spaces left filled with air in between the aggregates. This makes the final product porous, with as much as 20% of fully hardened concrete being composed of air where water used to be. The more water in a mixture, the more porous it will be and the weaker.

Weather Concerns for Concrete

One major consideration for weather exposure in concrete is the humidity of a location. Rather than the short bursts of something like rain or snow, humidity tends to imply long-term moisture that is ubiquitous throughout the environment. This can have an impact on the pH levels in concrete, with high humidity increasing the pH levels and ultimately compromising the integrity of the concrete. This leads to decreased strength of concrete. Additionally, this also raises the risk of microbial growth such as mold or mildew, which can not only weaken the concrete but cause health concerns amongst occupants of the structure.

High temperatures can also have a negative impact on concrete, leading to a decline in strength over time. This is primarily an issue in artificially high temperatures, such as certain plants where the concrete may be exposed to extremely high heat. However, the rate that a temperature rises and exposure over time can still be a consideration for concrete.

Extended exposure to any extreme condition, such as rain or snow, can also be bad for a concrete structure.

Factors to Consider

When planning a project using concrete, there are a number of preparations that you must make. In addition to gathering requirements and supplies, renting concrete forms, and properly planning dimensions, climate should be taken into account.

Porosity is the reason that concrete is not waterproof and can be represented in two ways in concrete. Gel pores are small pores that are part of the glue used to hold together aggregates in your concrete mixture. These pores are tiny and do not typically present an issue when it comes to water protection. Conversely, capillary pores are more of a problem, as they are larger and formed when there is too much water in the original mixture. These pores may also be interconnected.

Another factor is the permeability of your concrete, which represents how easy or difficult it is for liquids to get into or flow through a porous material. While all concrete is permeable, the level of permeability can impact the ability of concrete to withstand weather extremes. A high-quality concrete will have low permeability.

Over time, concrete is always vulnerable to weak points. For example, any time a hole is created in concrete, this creates another entry point for water and moisture. Joints between two concrete components can also lead to weak points.

To counteract these concerns, concrete can be waterproofed to prevent severe weather exposure. The best way to do this is to observe good mixing practices, including the right water to cement ratio, and to use high-quality aggregates and high-strength concrete.