Trade Journals for the Concrete Industry

The spotlight on the global concrete industry with respect to carbon dioxide (CO2) emissions basically started gain- ing momentum after the Protocol to the United Nations Framework Convention on Climate Change, the ‘Kyoto Protocol,’ was adopted at the third session of the Conference of the Parties (COP 3) in Kyoto, Japan on December 11, 1997. Globally, it is estimated that the concrete industry, and specifically the cement industry, contributes about 7 to 8% of CO2 emissions. The need to lower CO2 emissions in response to regulatory pressures, in addition to commitments by major cement producers to be good stewards of the environment by advancing the use of low-carbon building materials, has led to a significant transformation in the North American cement industry. In 2021, the major cement producers announced that they were stopping production of ASTM C150 cements and switching to ASTM C595 Type IL cement (portland-limestone cement, PLC), which permits up to 15% replacement of clinker by finely ground limestone in lieu of the 5% maximum replacement limit for ASTM C150 cements. The switch to PLC undoubt- edly helps to reduce the embodied carbon of concrete by up to an additional 10%, which is a step in the right direction. Various research studies prior to the increasingly widespread use of PLC indicated concrete performance similar to that obtained with ASTM C150 cements. However, issues have been reported including increased water demand and, more importantly, lower strengths. Therefore, it is imperative that concrete producers conduct laboratory/ truck trials and, if needed, modify, or preferably optimize, their concrete mixtures when they switch to PLC.