Concrete forms the foundation for our infrastructure and plays a key role in building our communities. It is also is one of the most sustainable choices for construction. Lehigh Hanson is committed to further enhancing concrete’s inherent sustainability and doing our part to promote environmentally responsible manufacturing. The introduction of portland-limestone cement (PLC) by the industry in the last few years represents a significant step forward, especially when used in conjunction with supplementary cementitious materials (SCM) such as slag cement.
Portland-limestone cements are specially formulated cements that provide comparable performance to ordinary portland cements (OPC) while delivering a more environmentally sustainable product. While OPCs may contain up to 5% limestone, PLCs are manufactured with up to 15% micro-sized limestone. By diverting a portion of the limestone past the pyro-processing stage, we can avoid that release of CO2 from both combustion and calcination by incorporating it into the cement. Additionally, the inclusion of optimally sized limestone enhances the cement’s properties due to improved particle packing, the creation of nucleation sites which enhance hydration, and the formation of carbo-aluminates which help to stabilize and densify the reaction products.
PLCs are accepted in the United States and Canada and have been adopted by CSA A3000 (Cementitious Materials Compendium), CSA A23.1 (Concrete Materials and Methods of Concrete Construction), and the National Building Code of Canada. In the United States, the ACI 318-14 building code references ASTM C595 and C1157 and AASHTO M240 specifications for PLCs and concrete made with PLC are similar to those of regular portland cements in that they must both meet the same performance requirements.
The use of both PLCs and SCMs results in an enhanced product performance and a significant reduction to greenhouse gas emissions, energy consumption, and quarried material consumption. Concrete finishability and pumpability are generally improved, as are the hardened concrete’s durability and late age strength.
Lehigh Hanson’s operations in Canada are leading the charge in sustainable concrete products with Lehigh Cement, Ocean Concrete and Hanson Ready Mix. “The sustainability of our products and ability to offer long-term solutions for the construction industry are a significant part of our strategy to meet our responsibilities to the industry and our communities,” said Lino Dinis, Sales Manager for Lehigh Cement.
In 2018, the Hanson Ready Mix operations in Ontario were able to run a mix portfolio with approximately 66% PLC, 14% OPC, and 20% slag achieving more than a 26% reduction in greenhouse gas emissions, or a savings of more than 24,000 tonnes of CO2. With amendments made to CSA mid-2018, Hanson Ready Mix has been able to convert entirely to PLC cement and is anticipated to now achieve an approximate 30% reduction in CO2 emissions.
“The materials have definitely demonstrated their performance, and incorporating both PLC and slag into our mixes has become the operating norm. Our customers win with a better product and better finishability, while the environment wins with reduced CO2 emissions,” said Kevin Chevrier and Laura Mammoliti, QC Managers at Hanson Ready Mix in Ottawa and Cambridge.
“Using PLC and Slag may not sound as exotic as some of the other technologies out there, but by far and away it gives you the biggest bang for the buck when it comes to making an actual improvement on your environmental footprint,” said Mike Stanzel, Lehigh Cement Technical Services Manager for Ontario and Quebec. “As part of the concrete industry, we continue to educate and work with agencies, designers and contractors on the advantages of adapting these sustainable products.