Concrete is a testament to modern construction’s achievements, playing a pivotal role in structures worldwide. Renowned for its remarkable strength and adaptability, it has shaped skylines and been the backbone of infrastructural marvels.

Yet, for all its prowess, concrete isn’t without its vulnerabilities. Its porous character can often be its undoing, allowing moisture to seep in and compromise its integrity. Recognising this, the construction industry has long sought solutions to counteract this flaw. Among the most effective measures are waterproofing admixtures.

In this post, we’ll explore these admixtures, providing insight into their scientific underpinnings and their invaluable role in preserving concrete’s robustness.

What are Waterproofing Admixtures?

At their essence, waterproofing admixtures are integral components added to the concrete mix to reduce its inherent permeability. Their operation is twofold: they either act as blockades for the concrete’s microscopic pores or impart a hydrophobic characteristic to the mix, making it actively repel water.

Examples of these admixtures include crystalline waterproofing agents, hydrophobic pore-blocking ingredients, and various polymers. All these elements work synergistically to enhance concrete’s durability. The ultimate goal of employing these admixtures is to fortify concrete against the erosive effects of moisture, guard against water-induced decay, and ensure that structures retain their strength and purpose for a more extended period.

How do they work?

Waterproofing admixtures operate with a precision that hinges on microscopic interactions within the concrete matrix. Their primary action can be categorised into two distinct mechanisms.

  1. The first involves the meticulous filling of capillaries inherent in concrete, effectively reducing its permeability. This process ensures that these channels, which could otherwise allow water ingress, become sealed off, maintaining the structure’s integrity.
  2. The second mechanism involves a chemical interaction with the byproducts formed during cement hydration. This interaction leads to the formation of insoluble crystalline structures that stop the concrete’s pores and capillaries forming. The presence of these crystals significantly diminishes the potential for water penetration.

Through these actions, waterproofing admixtures collectively equip concrete to resist water ingress. This is vital for preserving the material’s structural qualities and ensuring its longevity, even when subjected to environments with high moisture levels or direct water pressure.

What are Permeability-Reducing Admixtures (PRAs)?

Permeability-Reducing Admixtures, often abbreviated as PRAs, stand as essential tools in concrete construction. While they’re part of the larger family of waterproofing admixtures, their main objective is to reduce the permeability inherent in concrete.

They effectively counter water movement inside the concrete matrix, whether caused by capillary action or external hydrostatic pressures. Through this action, PRAs help ensure that structures maintain their durability and strength over extended periods, lessening the chances of water-related deterioration and subsequent repair costs.

Using PRAs strengthens concrete, promoting the lifespan of buildings and infrastructures. There are two significant categories of PRAs: PRANs (for Non-Hydrostatic conditions) and PRAHs (for Hydrostatic conditions).

PRANs: The Guardians against Capillary Absorption

PRANs, or Permeability-Reducing Admixtures for Non-Hydrostatic Conditions, are specially formulated for environments where concrete is not subjected to hydrostatic pressure. These admixtures work at a microscopic level, addressing the intricate dynamics of water movement in concrete.

Specifically, PRANs target the challenges posed by capillary absorption and diffusion, which can subtly erode the concrete’s integrity over time. These specific qualities make PRANs invaluable for a range of applications where the presence of standing or pressurised water isn’t a primary concern but where the durability and longevity of the concrete against ambient moisture and water vapour are crucial. Understanding when and where to use PRANs is vital for optimal construction outcomes.

PRANs are best used in the following applications.

  • Above-ground structures: Offering protection against dampness due to humidity or rain.
  • Rooftops: Ensuring that the top of buildings remains impermeable, safeguarding the interiors.
  • External walls: Especially crucial in regions prone to heavy rainfall, guarding against water seepage.

PRAHs: The Protection against Hydrostatic Pressure

PRAHs, short for Permeability-Reducing Admixtures for Hydrostatic Conditions, are the unsung champions in concrete construction, particularly for deep-set structures. Their design and functionality cater specifically to persistently submerged environments or frequently interfacing with water. Whether underground tunnels, basements, or water treatment facilities, PRAHs are integral in ensuring that these structures remain resilient against the relentless push of hydrostatic pressure.

The constant battle against such pressures necessitates the use of these specialised admixtures. Their presence aids in maintaining the integrity, durability, and longevity of structures, making them indispensable for projects located deep into the earth or in recurrent contact with large bodies of water.

PRAHs are best used in the following applications.

  • Basements: Protecting against groundwater infiltration.
  • Tunnels and culverts: Ensuring longevity amidst constant moisture exposure.
  • Swimming pools: Keeping the structure watertight for the safety of users.
  • Foundation slabs: Acting as a shield against moisture from the ground.

PRANs vs PRAHs: Drawing the Line

While PRANs and PRAHs are PRAs, their distinct differences lie in their designed applications. PRANs are tailored for environments without significant water pressure, making them ideal for structures exposed to external moisture. On the other hand, PRAHs are engineered to withstand sustained water pressure, making them indispensable for submerged or ground-adjacent structures. The formulation differences are also notable, with PRANs leaning on densifiers, while PRAHs might employ hydrophilic materials or crystalline technologies.

Real-World Applications

Consider a coastal region with high rainfall. An apartment complex would need PRANs for its external walls and rooftops, ensuring the residents remain dry. However, its basement car park, lying below ground level and constantly threatened by hydrostatic pressure, would demand the robust protection of PRAHs.

Another example is a major city near a river prone to seasonal flooding. For a new riverside commercial complex in such an environment, the ground-level promenades and outdoor spaces would be ideal candidates for PRANs. Though not continuously submerged, these areas are exposed to occasional floodwaters and regular moisture, necessitating protection from water infiltration.

In contrast, the complex’s underground utilities and service tunnels, perpetually at risk from the river’s hydrostatic pressure and potential groundwater intrusion, would significantly benefit from the enhanced protection offered by PRAHs. This ensures that the foundational and subterranean components of the complex remain unaffected by the surrounding water threats.

Concluding Thoughts

Waterproofing is not just a construction afterthought; it’s imperative. Whether a skyscraper or a humble home, the right waterproofing admixture ensures longevity and safety. At SPG Go Green, our commitment is unwavering with our VaporLock products: to offer superior solutions tailored to Australian conditions, ensuring each structure, irrespective of its purpose, stands resilient against the test of time and elements.