Innovative post-initial set applied colloidal silica (P3) is being deployed to construct more durable factory floors and enabling contractors to hard schedule their projects.  

A case in point is the treatment of a new factory’s 1 400m² tooling area with this unique technology. Specified by Celtis Architects, United States-based SprayLock Concrete Protection’s colloidal silica P3 was applied by one of Spraylock Africa’s approved applicators, RCR Flooring.  

The company has an impeccable track record working with SCP technologies to permanently waterproof, densify, harden and seal concrete after a single spray-applied application.  

Spraylock Africa supplied the post-initial set applied colloidal silica and provided technical support wherever necessary. RCR Flooring was subcontracted to H Kampman BK, the principal contractor, who worked alongside structural engineer, M Coetzee Consulting Engineers.  

Porosity issues 

As a durable construction material, concrete can handle the weight of heavy equipment and machinery and regular foot and material handling equipment traffic. Therefore it is an ideal material for this application. 

However, concrete does have its limitations as it is porous. Created as bleed water exits during curing, pores make up between 12% to 18% of concrete.  

They are not visible to the naked eye because they have a smaller diameter than that of human hair, but they are larger than a water molecule. This enables water containing deleterious agents to enter concrete, eventually destroying it from the inside out.  

Water is drawn by the lower pressure inside buildings. It is initially held back by its surface tension inside the dry microscopic pores.  

Once the pores become wet, water starts making its way through the material. These voids also start to actively draw water from the ground by capillary action.  

Considering that cement paste used to bind concrete contains calcium, which is soluble in water, these pore structures also become larger when wet. This, in turn, enables more water to enter floor slabs. 

A single spray-applied application to the horizontal concrete elements after they have been cast was done by Spraylock Africa’s approved applicators, RCR Flooring.

Oil contamination 

A further concern for factory floors is the occasional unforeseen oil spillage. Recent research shows that petroleum products eventually damage concrete floors over time. They contain sulphur, which combines with other molecules in the foundation to create acids. These destabilise the concrete matrix. 

To remove oil stains, factory floors are usually cleaned with extremely hot water or, in some instances, steam. Factory floors in environments with ambient temperatures undergo thermal shock when this occurs, leading to cracks that weaken them. 

Why colloidal silica P3? 

Sheldon White, national sales manager of Spraylock Africa, explains: “Post-initial set applied colloidal silica P3, ‘colloidal nano silica’ or ‘nano silica’ has been used for more than two decades throughout the world, including in South Africa, to make the oldest commodity-based material more durable and, therefore, longer lasting. 

“More than 100 academic papers have already been authored by over 15 research teams to demonstrate the improved properties of concrete containing colloidal silica. Moreover, two American Society for Testing and Materials (ASTM) working groups have been assigned to just work on post-initial set applied colloidal silica P3 specifications.  

“Notably, representatives of our principal, SprayLock Concrete Protection, serve on two of these committees. ASTM develops and publishes voluntary consensus technical international standards for a wide range of materials, products, systems and services.”  

More than 100 academic papers have been authored demonstrating the improved properties of concrete containing colloidal silica.

Mechanism of action 

White explains that these amorphous silicon dioxide particles are less than 100 nanometres in size and suspended in water. They are spray-applied to the horizontal concrete elements after they have been cast.  

Post-initial set applied colloidal silica P3’s small size provides a tremendous amount of reactivity and pozzolanic potential – even greater than that of undensified silica fume. This reaction takes place in the capillary voids and pore space. In this way, they are filled with more calcium-silicate hydrate (C-S-H).  

C-S-H is the same reaction product that provides concrete with its strength and durability traits. Even under hydrostatic pressure, the movement of water through concrete is restricted. This waterproofing action considerably reduces water-borne contaminant ingress through concrete. 

Beyond waterproofing 

Post-initial set applied colloidal silica P3 addresses the known limitations of traditional waterproofing methods. Acrylic and epoxy sealers require regular maintenance because of their high wear potential, especially in industrial flooring applications.  

“Certainly, polyurethane sealers are thicker and, therefore, provide a durable abrasion-resistant finish. However, they cannot be applied to the surface of concrete while it is still wet, delaying construction. Meanwhile, penetrating sealers, such as silanes, silicates, siliconates and siloxanes, only enter the top surface of concrete.  

These are, therefore, also not a permanent solution, again adding to maintenance costs over the lifecycle of the factory in the same way that acrylic and epoxy systems do,” White says. 

The technology is proven to permanently waterproof, densify, harden and seal concrete.

Dry-shrinkage cracks 

Another concern for industrial flooring is dry-shrinkage cracks. In its plastic state, concrete gains volume due to the exothermic hydration reaction of cement, calcium sulphate and calcium aluminate to form calcium sulfoaluminate.. This gain in volume occurs within the first few hours after mixing with water.  

As concrete loses moisture and starts to harden, it experiences losses in volume and starts acting like a wet sponge as it dries. When shrinkage is restrained by contact with the subbase surrounding structural components, tensile stress is developed within the concrete.  

Although strong in compressive strength, concrete is weak in tensile strength. This weakness is significantly tested as concrete shrinks literally pulling itself apart. The outcome is cracking at the weakest points. 

Closing the pores 

White says: “By making the pore structure less continuous and significantly reducing the transport of water through the concrete, post-initial set applied colloidal silica P3 retains water that normally would evaporate, slowing the rate of drying significantly.”  

Changing the chemistry of the pore solution and then shutting down liquid transport greatly reduce drying shrinkage of concrete. Testing has demonstrated a typical decrease of between 40% and 60% of drying shrinkage at 28 days of post-initial set applied colloidal silica P3-treated concrete compared to controls. “There have even been instances where colloidal silica P3 has provided 100% guarantee against drying shrinkage,” reveals White. 

Optimised curing 

With optimised curing, the construction programme can be fast-tracked. The floor slabs can be accessed within an hour after the concrete is placed and treated with SCP P3 Industrial. It also eliminates the need for cumbersome traditional curing methods, such as plastic, water and curing compounds. 

Concrete curing provides adequate moisture, temperature and time to allow concrete to achieve the desired properties for its intended use. Without proper curing, concrete will often not be able to perform as expected.  

Conventional concrete that has not been treated with post-initial set applied colloidal silica P3 technology needs to maintain a relative humidity greater than 80% – a temperature that exceeds 10°C – for a period that typically ranges between three to 14 days, depending on the application.  

Abrasion resistance 

Post-initial set applied colloidal silica P3 also increases the abrasion resistance of industrial flooring. This is the ability of the surface of the flooring to resist loss due to actions that dislodge particles. Most loss of surface in factories is as a result of scraping, such as pushing or dragging pallets with protruding nails.  

Industrial floors also incur damage when dust is ground into the surface by forklift trucks. Then there are extenuating circumstances, such as the action of front-end loaders at waste-transfer stations, that also need to be considered. 

Generally, concrete abrasion resistance is proportional to its compressive strength. Therefore, concrete with a high compressive strength can better resist abrasive forces. When curing and finishing are inadequate, abrasion resistance may only be a very small percentage of concrete’s compressive strength.  

“This technology is a significantly more efficient way of managing abrasion resistance compared to dry-shake hardeners with their specialised processes that rely on skilled personnel. Often concrete mix designs must also be modified to accommodate these methods. This is because modern cements are finer and, therefore, produce less bleed water, which dry-shake hardeners need to function effectively,” White concludes. 

A technical review of concrete floors and the use of post-initial set applied colloidal silica (P3) to construct durable factory floors.  

Full acknowledgement and thanks go to Spraylock Africa for the information in this editorial.