Tuesday, 16th November → New business opportunities (2)

CO2 neutral construction with concrete

The CO2 emission associated with cement and concrete are receiving increasing attention. Although the intrinsic emission of cement and concrete are low, the enormous volumes used – more than all other materials put together – mean they account for around 6-8% of global emissions. Cement cannot be replaced by other materials – even to replace on quarter of concrete with timber would require new sustainable forest one and a half times the size of India.  The composition of the earth also severely limits alternative chemistries.  This means that the most realistic option to reduce CO2 is to replace part of clinker in blended cements with SCMs (Supplementary Cementitious Materials). However, the availability of the most widely used SCMs, blast furnace slag and fly ash from coal burning is quite modest (~15%) compared to the demand for cement.

In this context kaolinite clays, which become very reactive pozzolans when calcined at 800°C are a game changer as they are super abundant worldwide.  Moreover, the coupled substitution of calcined clays with limestone can give similar mechanical properties to plain Portland cement with only 50% clinker.  These LC3 cement have CO2 emission up to 40% lower than Portland cement.  Furthermore, calcined clays are much more reactive than other SCMs, so equivalent strengths can be obtained at earlier ages.

The precast industry should be an excellent opportunity to produce more ecological materials, due to the ability to better control mix design, surface finish, cover depths, etc.  However, this potential has not really been realized, to date, due to the demand for high early strengths. This means that cement contents and final strengths are usually much higher than required for the structural performance, effectivity representing wasted materials and CO2.

In this presentation I will build on these observations to discuss future directions for more sustainable concrete, both in general and in the context of the precast industry.


Related articles:

Issue 12/2023 CARSTORCON

5,000 m³ of climate concrete realized using negative-emission-technology

CarStorCon Technologies has realized 5,000 m³ of climate concrete, impressively demonstrating that active climate protection and pioneering material innovation are already a reality. By combining raw...

Issue 05/2014

Comparative life cycle assessment of various pipe materials

1. Introduction Many industrial products are increasingly assessed on the basis of their carbon dioxide emissions. For sewer construction, pipelines consisting of various base materials such as...

Issue 07/2014

Concrete products based on a binder matrix produced with low CO2 emissions

Cement production is characterized by process temperatures in excess of 1.300?°C and substantial CO2 emissions; about 60?% of these emissions are attributable to limestone neutralization [1]. These...

Issue 07/2012

The future of building materials in research and practice

For the 18th time building material experts from all over the world will meet in Weimar/Germany for the international building materials conference “ibausil”. This year also the team of the F.?A....

Issue 07/2023 IAB WEIMAR/RILEM

International Conference on Construction Materials Recycling

The 5th International Conference on Construction Materials Recycling (V.PRE = V International Conference Progress of Recycling in the Built Environment) takes place from 10 to 12 October 2023, for the...