3.7. Resistance to Water and Weathering

Properly cured and dense concrete is water-resistant and can be made watertight with additives or surface treatments.

Concrete, when mixed and cured correctly, becomes dense enough to prevent water from passing through it. This quality makes concrete useful in building structures that need to resist water, such as buildings in rainy areas or structures that must contain water, like swimming pools. To enhance its watertight properties, various additives can be included in the concrete mix or applied as surface treatments. These additives help fill the tiny pores in the concrete, making it less permeable.

Think of concrete like a sponge. When it's well-prepared and dense, it can resist water absorption much like a sealed sponge that doesn't soak up water. If you’ve ever used a waterproof phone case, that case protects your phone from water damage similar to how waterproof additives protect concrete.

Enhancement through additives: • Silica fume, fly ash, and superplasticizers improve impermeability. • Waterproofing admixtures or membranes used in underground tanks and basements.

To make concrete even more resistant to water, engineers can use special materials in the mix. Silica fume and fly ash, for instance, help create a denser microstructure, which blocks water paths. Superplasticizers help maintain workability while reducing water content, leading to a stronger mix. Additionally, waterproofing admixtures can be added directly to the concrete or applied later in the form of membranes for places it’s critical to keep dry, like underground tanks and basements.

Imagine you’re baking a cake. If you want a moist and delicious cake, you need to add ingredients that enhance its texture and moisture retention, such as pudding mix or sour cream. Similarly, in concrete, using additives is like adding those ingredients; they make the concrete more resistant to water.

This makes concrete suitable for hydraulic structures like dams, reservoirs, canals, and marine works.

Because of its water-resistant properties, concrete is the material of choice for many hydraulic structures that must hold large quantities of water or face challenges from the marine environment. Examples of these applications include dams, which require a strong and impermeable material to prevent leakage and ensure structural integrity. Reservoirs store drinking water and need to be made watertight to avoid water loss, and marine works like piers and wharves must endure the corrosive nature of saltwater.

Think about a large aquarium. The walls must be strong and watertight so that the fish and water stay contained without leaking. Just like those strong walls, structures like dams and reservoirs need concrete that protects against water escape and withstands environmental challenges.

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