Building durable structures

The most used man-made material on the planet is concrete. Construction projects small, medium and large have all used concrete in one way or another.

However, as evidenced from crumbling infrastructure and structures the world over, the quality of the concrete can determine whether a project is truly viable or not. For instance, building a bridge with a lifespan of 50 years is not economically viable considering the cost of initial construction, eventual repairs, and the likelihood of early replacement.

Thus, the lifespan of a concrete structure is vital. With population growth and density of a city intensifying, constructing replacements of key infrastructure and buildings can be a costly and sometimes impossible process. Where possible, it creates huge disruption to the local population. The longer these structures can last the better.

Concrete can deteriorate under certain circumstances, such as:

• Chloride attack/corrosion of steel reinforcement;
• Sulphate attack;
• Alkali aggregate reaction (AAR); and
• Freeze/thaw cycles.

That being said, the most adverse influence of concrete durability involves the transport of fluids through the concrete. Water continues to damage or completely destroy more buildings and structures than war or natural disasters. Of course, concrete does have water resistant capabilities, but is at risk to water penetration. Thus, a waterproofing barrier is a must to lower the permeability and increase the durability of concrete.

To do so there are a few options in creating a concrete waterproof barrier, including:

• Crystalline admixtures;
• Water repelling admixtures;
• Densifying admixtures;
• Densifying admixtures and water reducers; and
• Surface-applied membranes.

More times than not, the selection is narrowed down to the surface or externally applied membrane and the Internal membrane using crystalline technology. The external membrane is a material that provides a barrier around the concrete structure in order to prevent the passage of water. Externally applied membranes are the traditional waterproofing method, but have limitations that include tears, punctures, deterioration over time, and installation errors. If any of these situations take place, repair can be impossible because the membrane is not accessible through the concrete and it is hard to find the failed area that needs to be fixed. This ends in replacement which takes a great deal of time and costs considerable money, if it is at all possible.

An internal or integral waterproofing membrane is one that performs its function within the concrete as opposed to on the surface. This is the technology behind Permeability Reducing Admixtures (PRA). The admixture becomes a permanent solution as it is part of the concrete mix and lays dormant in the matrix until it comes in contact with moisture where it develops needle-like microstructure to stop the flow of moisture.

Furthermore, in North America the concrete waterproofing industry redefined their terminology a short time ago in a way which helps to clearly understand the differences between admixtures. In fact, American Concrete Institute’s (ACI) 212.3R-10 Report on Chemical Admixture document devoted Chapter 15 to Permeability Reducing Admixtures that outlines PRAH and PRAN classifications. Permeability Reducing Admixture – Hydrostatic Conditions or PRAH products are sufficiently able to resist water under hydrostatic pressure penetration and are suitable for watertight construction.

Conversely, damproofing admixtures are now referred to as Permeability Reducing Admixture – Non-Hydrostatic Conditions or PRAN. PRAN admixtures reduce water absorption by repellent chemicals (soap, oils) or partial pore blocking (densifiers). These admixtures are not suitable for concrete exposed to water under pressure and cannot protect in the presence of hydrostatic pressure. Waterproofing against hydrostatic pressure is an important distinction that sets PRAHs apart from PRANs.

Crystalline Waterproofing is the durable concrete waterproofing solution worldwide. With sustainable building practices increasing in importance, and the lifespan of a structure intrinsically connected to this movement, a reliable waterproofing solution that will last for the intended life of the concrete structures becomes paramount.

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