Waterproofness of concrete

Concrete is a material that is used extensively in construction because of its strength and durability. However, its vulnerability to water penetration is a crucial feature that is frequently disregarded. In order to guarantee the longevity and structural integrity of buildings exposed to moisture, it is crucial to comprehend the waterproofness of concrete.

The process of waterproofing concrete entails stopping water from soaking into its pores and through its surface. Concrete is porous, allowing water to seep through capillary action even though it looks solid. This infiltration can result in a number of problems, including the deterioration of embedded steel reinforcements, the growth of mold, and structural damage.

Concrete’s ability to withstand water is influenced by various factors. Important factors include the caliber of the components used in its mixture, the water-to-cement ratio, and the curing procedure. In general, properly mixed concrete with a lower cement-to-water ratio is less permeable and denser, making it more resistant to water penetration.

Concrete’s waterproofing is also influenced by outside variables. Over time, the environment, temperature swings, and exposure to freeze-thaw cycles can all have an impact on its performance. For example, water that seeps into concrete in cold climates may freeze and expand, creating cracks and weakening the structure.

Using coatings, ensuring adequate joint sealing, and utilizing water-repellent admixtures are all effective waterproofing techniques. Admixtures that are water-repellent change the surface tension of water, making it harder for it to seep through concrete. Water intrusion is stopped on the surface by coatings like sealants or membranes. Another essential component in preserving the waterproofing integrity of concrete is properly sealed joints and fractures.

Knowing and using efficient waterproofing techniques is crucial for any construction project, whether it’s a residential driveway, a bridge deck, or a basement foundation. Concrete structures can continue to be durable and structurally sound for the duration of their intended life by addressing possible water penetration early on and implementing the necessary preventive measures.

Here at "All about concrete," we delve into these important facets of concrete building so that experts and amateurs alike can construct sturdy, long-lasting structures.

Designation and method for determining water resistance

To identify a particular brand of building material’s water resistance, follow GOST 12730.5-84 "Concrete. Methods for determining water resistance"; the letter "W" and even numbers 2,4,6,8….20 indicate the water resistance. The number that appears after the letter "W" represents the excess water pressure in kilograms per square centimeter at which the test sample becomes impermeable to water for a predetermined amount of time. Concrete w6 has a water resistance of 6 kgf/cm2 or 0.6 MPa, whereas concrete w4 has a water resistance of 4 kgf/cm2 or 0.4 MPa, and so on.

In accordance with the requirements of GOST, the determination of concrete water resistance is carried out on a series of samples with a diameter of 150 mm and a height of: 150, 100, 50 and 30 mm. Samples in the amount of 6 pcs. each standard size is placed in a special “six-shot” device for determining the water resistance of concrete, and gradually increasing the water pressure, using the “wet” spot that appears, it is determined at what water pressure the concrete begins to let moisture through. The total testing time for a series of samples of each size is 4, 6, 12 and 16 hours, depending on the height (30, 50, 100 and 150, respectively).

The concrete water resistance class is derived from the following table, and the water resistance of a set of samples is evaluated using the highest water pressure at which no moisture infiltration occurred on four samples:

Factors affecting the water resistance of concrete

The porous structure of the building material influences and determines the moisture permeability value.

As a result, the following variables have an impact on a given batch of concrete’s water resistance:

• Density. There is a direct relationship here – the higher the density, the higher coefficient of water resistance of concrete.
• Concrete shrinkage. Harmful factor leading to increased permeability of the structure to moisture.
• Excessive amount of sealer. Exceeding the optimal water-cement ratio leads to significant formation of pores, which in turn leads to a decrease in the water resistance coefficient.
• Presence or absence of special additives. Polymer, plasticizing, colmatizing or water-repellent agents significantly increase the structure’s ability to withstand water pressure.
• Type of cement. Aluminous, pozzolanic or high-strength cement binds more cement during hydration. Therefore, concrete prepared on their basis has a more dense structure, therefore, a higher degree of water resistance.
• Age of structure. In the process of gaining strength in the thickness of concrete, the number of hydrate new formations filling the pores and capillaries increases – water resistance increases.
• Concrete grade. There is a direct relationship here – the higher the grade of the material, the higher the ability to withstand moisture. This dependence is clearly illustrated by the table of concrete water resistance:

Methods for increasing concrete water resistance

In light of the aforementioned, the following methods of reducing the amount of pores and capillaries in concrete constitute the technology for improving its water resistance:

• Maximum shrinkage reduction using the following measures: introduction of special additives ("Mapecure SRA", "Bisil SRA", "ASOPLAST-MZ"), use of aluminous, expanding and high-strength cements, maintaining the optimal "water-cement" ratio, care for the freshly poured structure (covering with polyethylene film, spraying with water for 72 hours after pouring).
• Thorough vibration (compaction) using special equipment: deep and external vibrators.
• Making special waterproofing additives. Effective concrete additives for water resistance: “Penetron”, “Crystal”, “Tiprom K”, “Disom-Hidrofugo”, “Plionitis Asset”, “Aquasil”, “Polyfluid”, “Penta 811”, etc.
• Vacuuming freshly laid concrete using special installations. This method allows you to effectively remove excess water and “parasitic” air from the thickness of the structure.

Conclusion

For private developers, raising the water resistance of concrete structures is important because it can reduce the cost of waterproofing the cellar, basement, or foundation. You can either completely give up on waterproofing or go with the least expensive option, depending on the strategy you decide to employ to increase water resistance.

In order to guarantee concrete’s longevity and durability in a variety of construction projects, it is essential to understand how waterproof concrete is. Because of its inherent porosity, water can permeate the surface of concrete. However, if left unchecked, this can eventually result in structural problems.

There are a number of efficient ways to improve the water resistance of concrete. Water seepage can be prevented in concrete by adding waterproofing admixtures during the mixing process, which will greatly reduce the permeability of the material. By filling the concrete’s capillary pores, these admixtures give it a denser, less permeable texture.

Surface treatments, like sealants or coatings, are an additional strategy. These products coat the surface of the concrete in a protective layer that keeps water molecules out while allowing the material to breathe. For these coatings to remain effective, regular upkeep and reapplication are required.

Achieving waterproof concrete structures also heavily depends on using proper construction practices. Paying close attention to details during the placement, consolidation, and curing of concrete reduces the likelihood of cracks and voids forming where water could potentially seep in. Additionally, water can be diverted away from susceptible areas by using appropriate slope design and jointing.

In conclusion, careful construction methods, suitable materials, and well-thought-out design are all necessary to produce waterproof concrete. Builders and engineers can guarantee that concrete structures retain their integrity and functionality for the duration of their intended lifespan, even in difficult environments where water exposure is a concern, by comprehending these factors and putting appropriate strategies into place.

We examine concrete’s ability to withstand water and examine how important it is for improving longevity and durability in building. In addition to keeping out water, waterproof concrete protects buildings from rust and other damage, which eventually lowers maintenance costs. For both engineers and builders, it is crucial to comprehend the variables that affect waterproofness, such as mix design, additives, and appropriate construction methods. In order to ensure that concrete structures are weather-resistant for many years to come, this article looks at doable tactics for waterproofing concrete.

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