Robert J. Flatt

1 INTRODUCTION On the microscopic level, fresh cement paste forms a dense, flocculated network of grains suspended in water.

Unbelievably huge amounts of concrete, a major contributor to our contemporary world, are produced every year, and this continues to increase exponentially. ETH Zurich researchers Timothy Wangler, Yamini Patankar and Robert J Flatt explain the pros and cons of the digital fabrication of concrete, and the research still to be done in this relatively young and experimental subset of the construction industry and material science.

The restoration of fire-damaged historical monuments entails a wide range of scientific questions. Taking as a starting point the case of Notre-Dame de Paris, this Comment defines the materials science challenges of post-fire restoration, and also briefly outlines the issues of structural integrity, fire safety and preservation ethics. Fig. 1: Notre-Dame de Paris, 22 July 2019. Patrick Zachmann/Magnum Photos/Keystone Fig. 2: Notre-Dame de Paris, 25 June 2019.