Developing Low CO2 Concretes: Is Clinker Replacement Sufficient? The Need of Cement Use Efficiency Improvement

Abstract

Cement industry is under stress for mitigating CO2 emissions: it is responsible for around 5-7% of total global emissions due to the production that went over 2x109 tones in 2006. And this prospect will aggravate since it is expected, for 2050, an increase of 2.5 times, which will make cement industry guilty for more than 30% of CO2 emissions. Main actions for decreasing emissions are: energy efficiency in kilns, use of alternative fuels and clinker substitution. These, however, are not capable to decrease emissions in a satisfactory way. CO2 capture is expensive and could increase cement costs. The pressure, which is increasing all over the world, will certainly strike concrete producers. The optimization of cement use in concrete is an undeveloped strategy that can provide a huge contribution. For its development an international and cooperative effort is crucial. This paper proposes to change the focus from the cement production optimization to optimization of concrete production industry, responsible for most of cement consumption. It is discussed the limits of clinker substitution by mineral admixtures, comparing the expected cement demand increase versus the availability of these alternative materials, concluding that, despite the importance of this strategy, it is actually not capable for mitigating cement CO2 emissions in a satisfactory way. It is discussed and assessed technical possibilities and limits of optimization of cement content in concrete, based on literature data analysis using two new environmental indicators Binder Intensity and CO2 Intensity. There is a potential to reduce significantly the cement content on concrete, being possible to increase concrete production without increasing cement production and CO2 generation. This can impact significantly on concrete environmental load to global warming and also in its cost, making possible to increase popular habitations construction mainly in some developing countries which have a lack of different sort of infrastructure where concrete technology is still dominant.