All civil engineers will be aware of CEM1 concrete. It’s a standard concrete mixture using cement to cure and harden. CEMFree has been created by the David Ball Group to entirely replace the cement requirement in concrete.
What’s wrong with using cement?
Portland cement (OPC) is a mined material. It is therefore a finite resource, and has an environmental impact in its creation. During the curing process of cement / concrete large quantities of carbon dioxide is released into the atmosphere (0.95 tonnes / tonne concrete) which has a knock on effect on global warming and climate change.
What is CEMFree?
CEMFree is high performing cementicious binder that can entirely replace the need for cement. It consists of ground granulated blast-furnace slag (GGBS) and pulverised fuel ash (PFA) plus an admixture (kept very secret!?) so uses a large quantity of waste products in its creation.
CEMFree technical comparison to CEM1
- Better chloride protection
- 0% permeability
- Lower embodied energy (<1.5GJ/tonne vs. 5GJ/tonne)
- 95% less CO2 emissions (0.09tonne/tonne vs. 0.95 tonne/tonne)
- Reduction in thermal expansion so no expansion gap requirements
- No requirement for crack control so reduction in steel usage
- Equal strength at 28 days with a greater strength from then onwards
Publicly available specification is available: PAS 8820:2016
All in all it seems to be a miracle product to help revolutionise the industry into a climate friendly industry. This could presumably also use recycled aggregate to further reduce its environmental impact. It does make you wonder what the admixture is though?
I had heard of Passivhaus prior to attending the conference, but not many details in what it was and how it affected structural engineering. Put simply Passivhaus is design focussed on minimising energy use during it’s lifetime. (This links quite nicely with Peter Head’s talk focussing on performance focussed, rather than financially focussed tenders written about here.) Passivhaus, as a basis, tends to ensure the following in its design:
- good levels of insulation with minimal thermal bridges
- passive solar gains and internal heat sources
- excellent level of airtightness
- good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery (more info)
There is also a very similar set of standards for retrofitting properties called EnerPHit, since we obviously can’t solve poor building design by simply starting again. The EnerPHit standard is a slightly more relaxed version to Passivhaus due to the difficulties in renovating properties and because there needs to be an element of value for money. I live in a draughty, Victorian terrace, solid wall construction. Making it anywhere close to Passivhaus standards would be incredibly difficult.
Why follow Passivhaus design?
In an average building there is a 60-80% increase on heating costs compared to its design expectations.
78% of homes do not achieve the required air change rate rising high humidity levels, condensation, mould growth and associated health issues.
How does it affect structural engineering?
Thermal bridging: Make sure the structural framework of a building is enveloped within a thermal, insulating layer (and preferably a thick one). In professional work ensure a masonry column supporting a steel beam doesn’t penetrate through the cavity, ensure appropriate construction notes ensure all displace insulation is re-inserted.
Airtightness: During construction a building should have continuous plastic sheeting within the external structure. How do you fix this without using nails or staples? How do you ensure a building’s structure doesn’t penetrate through this?
Communication: Both of the above topics cannot be resolved without considerable communication between architects and engineers. Personally I have a great interest in sustainable design. Unusually I also have a degree in Architecture, as well as currently studying in Civil / Structural engineering. I hope in the future I am able to work on projects that combine both my personal interests, and also combine my skill sets.
Sorry for the massive delay in writing my next Sustainability Conference blog post. Life, hockey, youth group running and Christmas preparations have got in the way.
Angela Brady’s talk, of Brady Mallalieu Architects, was two fold. Firstly she spoke of true ecological and sustainable design, but this wasn’t the part that truly inspired me.
The second part of the talk was what really excited me! It was all about the collaboration required with education and it inspired the following teaching activities:
– Use big balloons to visualise how much CO2 on average we currently use in the UK, and compare it to the amount we need to reduce it down to. You could easily use smaller balloons to show what common activities produce too, such as a 10 mile commute.
– Adopt a school is a world-wide initiative that encourages professionals within STEM to adopt a school, and participate in STEM related activities and careers education. This is not a cohesive campaign world-wide campaign, but as with many other simple, yet great ideas it has been picked up in many countries keeping the same principle aim of developing STEM education. Watch out Woodlesford Primary School, I’ll be coming to you in the new year!
– The last idea made me realise exactly where I went wrong in my Architecture degree. Although I gained a 2.1 I was always engineering spaces, rather than creating them. Simply get a pack of straws and some sellotape and instruct the students to create a space. Leave the rest up to them. Some will create rigid structure, some might sellotape a series of straws together to create walls (potentially sloped and curved walls too) A space needn’t have a roof, or even be enclosed, but should simply be created. This activity will help explore the creativity and engineering minds of a youngster and may help differentiate between minds geared more towards architecture and those more scientific or engineering minded.
Let me know if you complete any of these STEM activities. I’ll keep posted about how my adoption of Woodlesford Primary School goes too!
“Peter Head is cited by Time magazine as one of 30 global eco-heroes.” That’s quite an accolade, and not undeserved.
The Sustainable Development Goals are targets that hundreds of countries around the world have agreed to (more info about these and implications in civil engineering in a future blog post). Peter Head was greatly involved in creating Goal 11: Make cities and human settlements inclusive, safe, resilient and sustainable and much of his work focuses on achieving this goal.
Peter believes that all design should take into account the environment in which it is placed. Within building work there are many systems which we interrupt, alter, and change: environmental, social, political, physical, psychological … the list goes on. Without considering the affects of all of these systems we cannot create truly sustainable design. He has set up a charity, The Ecological Sequestration Trust, which is collating every data set available (Europe wide!) that measures these factors. Right down to predicting future health or economic implications of a design. Not only that, but it will be available for FREE.
Read more… (it’s worth it!)