Repairs
Once there are leaks, repairs (or outright replacement) for external waterproofing membranes can be both expensive and complicated. Since they cannot be repaired from the negative side, access can be impossible. Crystalline products, on the other hand, will permanently seal all new cracking. When there are larger cracks, they can be repaired from the negative or dry side. This means this route is cost-effective for future work.
It is important to note this article is specifically discussing below-grade concrete waterproofing, which, once backfilled, does not allow for breaches to be detected (even with traditional waterproofing) without embarking on major excavation around the perimeter of the building.
Sustainability
External membrane materials are landfilled at the end of their life, and they also require resources to install properly, adding to waste. Crystalline waterproofed concrete, in contrast, can be recycled and reused as aggregate on a future concrete projects.
Supplementary cementitious materials
In addition to these two waterproofing strategies, another oft-cited solution to prevent water penetration is through the use of supplementary cementitious materials (SCMs). One common example is silica fume, which is an extremely fine noncrystalline silica often used in concrete structures that need high strength or significantly reduced permeability to water.
An SCM is a material added in conjunction with concrete’s basic form of water, portland cement, and fine and coarse aggregate. These SCMs make up a portion of the cementitious material within a concrete mixture, which means the proportion of cement in a given mixture will lessen as SCMs are added. Engineers and concrete suppliers will sometimes point out they can use silica fume and other SCMs to product a concrete mix that has very low permeability and can be considered ‘watertight.’
SCMs are used for a variety of reasons within a concrete mixture, which includes increasing durability. According to the National Ready Mixed Concrete Association (NRMCA), “these materials modify the microstructure of concrete and reduce its permeability, thereby reducing the penetration of water and water-borne salts into concrete.” Thus, the addition of SCMs can aid in creating a watertight structure, which, in turn, will create a durable end structure.
Silica fume is used to increase the strength and durability of concrete, densifying the mixture to block the flow of water, but it is not itself a waterproofer. Essentially, it makes concrete dense, but not watertight. SCMs can contribute to reducing concrete permeability and be a complementary component in a well-proportioned mixture, but there are drawbacks when the dosage is not optimal. For instance, if an SCM is used at a really high dosage, concrete has a tendency to crack, allowing a pathway for water infiltration.
This does not mean SCMs like silica fume are not increasingly valuable for a concrete mixture. When such materials are used optimally, they can significantly improve a concrete mixture’s lifespan. However, an alternative solution must
be used in order to create a completely watertight structure that will ensure a durable building.
Conclusion
A durable structure will lead to a sustainable building. In order to achieve concrete assembly with this enduring longevity, the permeability of the concrete mix must be as low as possible. This can be achieved with the proper waterproofing method. An externally applied membrane wraps itself around the concrete, protecting it from water ingress with a layer of material. However, if the shell is cracked, repair can be time-consuming, costly, and sometimes impossible. If using an internal admixture, the concrete itself becomes the waterproofing barrier.
Alireza Biparva, B.Sc., M.A.Sc., LEED GA, is a research and development manager/concrete specialist working at Kryton International Inc. He has more than a decade of experience in the field of concrete permeability. Biparva oversees several research projects focusing primarily on concrete permeability studies and the development of innovative products and testing methods for the concrete waterproofing and construction industries. He is an active member with the American Concrete Institute (ACI). Biparva has published several research papers in international journals and conferences on concrete permeability, waterproofing, durability, and sustainability. He can be reached by e-mail at alireza@kryton.com.
That is good that a reliable waterproofing system is required. I’ve been trying to decide if I need to waterproof my basement. After reading about the mechanical failure that could accure during the concrete process, I think I’ll definitely get that done soon.
I like buildings that are made of concrete. The steps for determining if it is durable enough seems really helpful. I imagine that consulting with a structural engineer might be even more helpful.