There is widespread agreement within the scientific community on the urgency for dramatically reducing our carbon footprint to stabilize the climate and mitigate the impact of rising temperatures. The consensus is that any successful course of action must support the dual objectives of stabilizing atmospheric carbon and maintaining economic growth. In the end, addressing climate change is neither a scientific nor even an economic challenge—it is a human challenge.
The current debate is not about the merits of reducing carbon in the atmosphere but rather what goals should be set in reducing carbon emissions. The CEO Climate Dialogue, an initiative of leading U.S. businesses which include LafargeHolcim, is calling for congressional policies on emission reductions of 80% or more by 2050. Twenty-five states have signed the US Climate Alliance Agreement to reduce emissions by 26 to 28 percent by 2025. And 445 US cities have committed to the Mayors National Climate Action Agenda for upholding the emission-reduction goals of the Paris Agreement.
These calls for long-term, affordable actions to reduce carbon emissions—along with increasing demands for carbon reduction in construction—have spurred the rapidly growing green building movement. As a result, industry stakeholders—from government officials with major highway and bridge projects to owners and designers of residential and commercial buildings—are increasingly focused on reducing the embodied carbon content of materials used in their projects
Reducing embodied carbon in concrete
The carbon footprint of the built environment is massive. For building professionals, reducing carbon emissions typically focused on increasing energy efficiency and pushing for renewable energy, thus reducing the amount of carbon generated by the fossil fuels used to operate buildings. While reducing operational carbon is important, it is equally vital to think about the greenhouse gases that are emitted to construct our buildings, as well as our infrastructure, in the first place—the embodied carbon.
Concrete is the most widely used construction material due to significant performance and sustainability advantages. Most of its components are naturally occurring, it can be produced from recycled products, it is recyclable, and it has a long lifespan. These attributes come in addition to unequalled durability, high thermal insulation, and local production, resulting in reduced transport emissions. Beyond these qualities, life-cycle analysis makes concrete a responsible choice for sustainable development.
Compared to other building materials in terms of embodied energy and CO2emissions, concrete is the favorable choice for building and infrastructure expansion. However, the fact remains that concrete has a high carbon footprint due to the energy intensiveness and generation of CO2 in portland cement manufacture. The good news is that ready-mix producers have a variety of options for meeting the increasing demands for lowering embodied carbon in concrete. Below are some approaches to consider for reducing the amount of portland cement clinker in your mix designs without sacrificing performance.
OneCem® Portland Limestone Cement is a blended cement meeting the specification requirements of ASTM C595 and AASHTO M 240 in which the allowable finely ground limestone within the cement ranges from 5% to 15%. OneCem has been designed to perform similarly to ordinary portland cements and has been rigorously tested to verify its concrete strength development, setting time characteristics, durability, and other performance properties.
OneCem can be used with supplementary cementitious materials and is compatible with concrete chemical admixtures. It also provides a sustainable solution by resulting in less CO2 generated per ton than a typical Type I/II portland cement. Over the last 10 years, our plants have produced more than 3 million metric tons of OneCem for concrete infrastructure and building applications throughout the US.
Supplementary cementitious materials (SCMs) are utilized in concrete as a separate component or as a constituent of blended cement. Their partial replacement of portland cement not only results in more durable, high-performance concrete but also lowers energy consumption and greenhouse gas emissions.
SCMs can be natural pozzolans (e.g., pumice) or they can be by-products of industrial processes. The most common SCMs are slag cement (by-product of iron manufacturing), fly ash (by-product of coal-combustion in power plants), and silica fume (by-product of manufacturing silicon metals). The amount of SCM replacement depends on performance requirements and/or project application.
Commercial product offerings from LafargeHolcim include NewCem® Slag Cement, a finely ground, granulated blast furnace slag (GGBFS) for strong durable concrete; MaxCem® Blended Cement, a combination of portland cement and GGBFS that can be blended in any ratio (from 20 to 40 percent) for improved strength and reduced permeability; and Tercem 3000®, a combination of portland cement, silica fume, and GGBFS for dramatically densifying concrete and minimizing its permeability. Talk to your local sales representative to learn more about availability in your local area.
Let’s work together to make a difference
Reducing embodied carbon in construction is an urgent issue because the emissions that our built environment releases over its lifetime are critical to keeping global temperatures at tolerable levels. An industry-wide commitment to reducing our carbon footprint is crucial and we need to act quickly.
LafargeHolcim is committed to providing sustainable construction solutions to make the world around us better. OneCem, SCMs, and blended cements allow you to give your concrete mixes a lower carbon footprint with the same or even better performance as traditional portland cement. Contact your sales representative to learn how our technical experts can assist you with consultative advice on using these products in your concrete. Our technical teams can also provide you with detailed test results, quality control records, and a wide range of additional support services to help you succeed in your on-going sustainability efforts.