Lehigh Hanson has indicated that concrete forms the foundation of our infrastructure and plays a key role in building our communities. According to the company, it is also one of the most sustainable choices for construction. The company has stated that it is committed to further enhancing concrete’s inherent sustainability and doing its part to promote environmentally responsible manufacturing. The introduction of portland limestone cement (PLC) by the industry in the last few years is thought to represent a significant step forward, especially when used in conjunction with supplementary cementitious materials, such as slag cement.
PLCs 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 pyroprocessing stage, it is possible to avoid the release of CO2 from both combustion and calcination by incorporating it into cement. Additionally, the inclusion of optimally sized limestone enhances the cement’s properties, due to improved particle packing, the creation of nucleation sites that enhance hydration, and the formation of carbo-aluminates that help to stabilise and densify the reaction products.
PLCs are accepted in the US 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 US, 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 OPCs, in the 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.
In 2018, Hanson Ready Mix operations in Ontario were able to run a mix portfolio with approximately 66% PLC, 14% OPC, and 20% slag, achieving a more than 26% reduction in greenhouse gas emissisons, or savings of more than 24 000 t of CO2. With amendments made to CSA in mid-2018, Hanson Ready Mix has been able to convert entirely to PLC cement and is anticipated to achieve an approximate 30% reduction in CO2 emissions.
“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.
“The materials have demonstrated their performance, and incorporating both PLC and slag into our mixes has become the operating norm,” said Kevin Chevrier and Laura Mammoliti, Quality Control 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.”
Read the article online at: https://www.worldcement.com/the-americas/20052019/lehigh-hanson-commits-to-enhancing-concrete-sustainability/