CO2 reduction in tunnel construction from a material technology point of view

Abstract

AbstractTunnelling and underground construction is a material‐intensive undertaking that involves the use of large quantities of concrete. Analyses of the life‐cycle assessment of a new tunnel show that the carbon footprint is largely determined by cement and concrete consumption. Optimising the quantity used, composition and properties of this construction material is thus crucial to reducing ‘'grey'' emissions – CO2 emissions arising from the construction phase. While strength and durability requirements along with exposure classes are clearly set out in directives and tender specifications, CO2 emissions per cubic metre of concrete are not currently considered a relevant criterion when it comes to project design, award and implementation. And this, despite the fact that the current state of knowledge and research shows that substantially lower‐carbon concretes could be used than is generally the case today. A paradigm shift is required to achieve the goal of carbon neutrality in the construction industry.This paper shows how CO2 emissions per cubic metre of concrete can be declared and reduced in tunnel construction, and how concrete recipes can be formulated using climate‐friendly materials, while maintaining the required strengths and durability properties. Using the design approaches outlined here, it is possible to increase clinker efficiency and reduce CO2 intensity without adversely affecting the structure and its functionality.