We are looking at the value of UHPC facade systems vs pre cast and wondering if anyone else is seeing any progress on the embodied carbon side. We looked into this two years ago and found that UHPC had high cement content, therefor higher embodied carbon. Just doing some research recently I haven’t seen anything new on this, has anyone else found anything more sustainable about UHPC?
While you’re generally correct the UHPC has higher cement content compared to traditional precast, the volumes of concrete are typically significantly different, therefore looking at the comparison on a concrete basis alone is not an apples-to-apples comparison. You need to look at the installed facade area for comparison purposes.
What resources are you using for your comparison?
UHPC covers a fairly broad spectrum of possible mix designs that each may have different requirements for their binder recipe. One thing they all have in common is that they almost always use a higher SCM replacement percentage of OPC (Ordinary Portland Cement) than any of the other mix designs used in the construction of a building, bridge, street and so on. Matt is correct in that they must be compared to other UHPC, and over the last 10 years I believe the embodied carbon has probably gone down in terms of lbs pcy of OPC, but was offset by having to source and transport the SCM from further away, but that is only drawing from personal experience, and observation of the industry, not hard facts from a survey, etc. There are also many more companies producing UHPC now, so that in itself has forced everyone to get creative, and also manage their costs, which will drive down OPC in the mix design. Something else to consider is that 2 years in the construction and concrete industries is like the blink of an eye, because change has happened very slowly for as long as I remember. Consider broadening the time range you evaluate, and contact suppliers from opposite sides of the country and you will have a good idea whether the embodied carbon is up or down.