Increasing the life of concrete for sustainable built environments

Over the years, built-environment professionals have increasingly turned their efforts towards improving the durability traits of concrete to construct longer lasting structures for sustainable built environments.

Fire resistant and durable, concrete enables the construction of buildings and infrastructure that can sometimes last for about 100 years. Increasing its durability will, therefore, further reduce the amount of energy, time and resources that would otherwise have been required for maintenance, repair or rebuilding.

“The global ‘green’ building movement has transcended merely using recycled materials to construct sustainable structures. Built environment professionals are taking a longer-term view of sustainability by, importantly, also focusing on raising the expected lifecycle of service-delivery infrastructure and buildings. By building concrete structures that last two to three times longer than current designs, we can reduce the need to rebuild them as often and, in so doing, alleviating the burden on existing resources,” Carl White, Managing Director of SprayLock Africa, says.

SprayLock Africa is the African distributor of United States-based Spray-Lock Concrete Protection’s (SCP’s) cutting-edge technologies, which have been designed and developed to provide enhanced concrete durability, protection and performance.

Factors that influence concrete durability include water to cementitious ratio; aggregate packing; reinforcement and type; curing methods; the environment in which it is placed; and finishing practices.

All concrete is susceptible to contaminant ingress, considering its porous nature and bleed-water channel. This is especially true for reinforced concrete, where the corrosion potential of reinforcing steel is directly related to the water, oxygen and chloride movement into the building material. It disrupts the protective layer around the reinforcement which leads to corrosion/rusting of the rebar.

White says that SCP helps reduce the corrosion potential of concrete by reducing the pathways of water and contaminate ingress.

“SCP is a colloidal silica product that enters the concrete through capillary voids. Once inside, the colloidal silica reacts with calcium hydroxide to form more Calcium Silicate Hydrate, or ‘C-S-H’, essentially filling the capillary and pore structure with more concrete. This action dramatically reduces permeability for the lifetime of the concrete,” he explains, adding that SCP penetrates a minimum of 38 mm into the concrete effectively enhancing and creating a more durable concrete cover.

Using life cycle modeling software, such as Life 365, laboratory-derived permeability parameters can be set to reflect the improvements to permeability gained with SCP products. Comparisons can also be made between untreated concrete and that which has been treated with SCP technology. These comparisons can estimate a percentage in life cycle expectancy gained with the use of SCP products.

The assessments have demonstrated that SCP can enhance the life expectancy of concrete by as much as two to three times. For example, the permeability of the concrete of a bridge in a marine environment can be reduced to elevate its life expectancy to between 60 and 90 years or more after treatment with SCP technology. This is opposed to only 30 years with the current mix design.

White says that this focus on improving the durability of concrete complements an array of other existing characteristics that make concrete a very suitable choice for sustainable construction.

“Among these is concrete’s thermal mass which absorbs and retains heat, reducing the need for heating and cooling. This is complemented by its reflectivity, which minimises the effects that produce urban heat islands. Moreover, concrete can be produced in the quantities needed for each project, reducing waste. It is also encouraging to note the work that is being undertaken in South Africa into recycling concrete for use in various applications, such as road layers. These traits position concrete, which is used more than twice as much every year, than all other building materials combined, as a champion of sustainability,” he concludes.