Technical note: GGBS: a sustainable solution for concrete

It is a pleasure to be here tonight to talk with my fellow structural engineers and their guests. I think that I was last at an IStructE event in 1963 while working here for Ove Arup and Partners, when it was a ‘small’ firm of only 500 in London. My talk is somewhat out of what we normally consider the main stream of engineering, but I would like to put forth the argument that we need to divert this main stream so that it picks up tributaries from the humanities as well. My theme tonight is ethics as it relates to technology and to sustainability in particular. We get so caught up with the technical considerations of our profession that we either claim to have no time for reflection or simply do not realise that we need to step back every once in a while and cast a cold, objective eye on our daily professional activities. About 20 years ago I had an epiphany. A client asked me the usual question that I had heard so many times before in my practice, ‘Can I do such and such a thing?’ Previously I used to reply that I would consider his request and after due consideration, which often included making some calculations, let him know the answer. But on this particular occasion I answered immediately, ‘Yes’. I realised that in our profession we could now do practically anything. Computers had allowed us to analyse even the most complex of structures and materials were approaching a zenith in their capacities. It became clear to me that the issue was no longer ‘Can I’ but was now rather ‘Ought I.’ The issue had shifted from the technological to the philosophical. Robert Silman, BA, BCE, MCE, PE Robert Silman Associates, Structural Engineers, New York and Washington