Putting the Multichoice decline in context
Lindsey Schutters
New standards pave way for green cement
10 Sep 2024
The construction industry is one of the biggest handbrakes in South Africa’s energy transition, but new standards introduced by the Department of Trade, Industry and Competition go a long way to speed decarbonisation along. SANS 8615:2024 is a two-part standard that sets specifications for the use of pozzolanic materials with Portland cement. These materials offer significant environmental benefits, particularly in reducing CO₂ emissions, making concrete more durable, and enhancing sustainability in construction projects.
Pozzolanic materials can replace up to 30% of cement clinker and reduce energy consumption in cement production.
One of the main benefits of pozzolanic materials (derived from the volcanic ash the Romans used in their cement mixes) is its potential to significantly lower CO₂ emissions in cement production.
Calcined clay pozzolans can replace up to 30% of cement clinker, which is the primary component responsible for the carbon emissions associated with cement manufacturing because of the extreme heat needed for calcination.
By using pozzolanic materials such as natural calcined pozzolana, the need for clinker is reduced.
This not only cuts emissions from the calcination process but also reduces the energy required to heat the cement kilns, contributing to a greener, more energy efficient production process.
Add durability, reduce maintenance
Pozzolanic materials are not just about sustainability; they also enhance the durability of concrete.
When pozzolana is mixed with Portland cement, it reacts with lime – a byproduct of the cement hydration process or added as hydrated lime – to form additional compounds that strengthen the concrete.
This reaction increases the concrete's resistance to moisture, chemicals, and temperature fluctuations, making structures more resilient.
More durable concrete means longer-lasting buildings with reduced maintenance needs, leading to further environmental benefits.
Fewer repairs and renovations translate to less material consumption over the lifetime of a building, making pozzolanic materials a smart choice for both sustainability and cost-efficiency.
New standard
SANS 8615:2024 is divided into two types of pozzolanic materials used with Portland cement
Natural pozzolana and natural calcined pozzolana is used in combination with Portland cement (class 42.5 N or greater) and can be applied in concrete, mortar, or grout.
While high reactivity calcined pozzolana – which offers even greater performance when used with Portland cement – enhances the cement's reactivity, providing improved strength and durability for high-demand construction projects.
Both parts of the standard include guidelines based on the British Standard BS EN 197-1:2011, ensuring that South Africa's construction materials align with international standards.
More than just carbon reduction
Pozzolanic materials contribute to broader sustainability goals by reducing the demand for natural resources such as limestone and clay, as well as the amount of solid waste generated during the manufacturing process, leading to a cleaner, more efficient industry overall.
By adhering to SANS 8615, local construction companies can ensure that their materials meet both national and international standards for quality and sustainability, positioning themselves as leaders in green construction.
