Simplistically, concrete is made of aggregate or filler, held together by a matrix of cement. The cement is a binder that sets and hardens independently. It can be used as a mortar, or more commonly, in the production of concrete, by the addition of aggregate. Cements come in two broad categories, non-hydraulic and hydraulic. Hydraulic cements can set in and under water and are the more important. Typically, they are made up of a mixture of oxides and silicates, which bind together giving off heat. The most common cement is Ordinary Portland Cement, colloquially abbreviated to OPC in the industry.
As approximately 3 tons of concrete are produced annually per person and it contributes to about 5% of the global CO2 footprint. This is due to the way cement is manufactured: It requires heat to convert limestone, in the presence of silicates, to a product that is then ground to produce the cement. CO2 is also emitted chemically during the process. Roughly 40% of the CO2 comes from the heating process and 60% from the chemical reaction. Furthermore, concrete production utilises a lot of water. Heat is generated on setting and the thermal expansion means that concrete is generally cast with construction joints.
Understandably, the industry is under pressure to reduce its CO2 production and find alternatives for OPC. Existing solutions include Energetically Modified Cement. BRE is currently also coming to the end of Project Aether this year, aiming to find more carbon friendly solutions.
A recent high profile project in London demonstrates progress in the right direction. The Shard has a basement slab comprising 5,600m3 of concrete containing 80% GGBS (ground-granulated blast-furnace slag) cement replacement. It was cast over a weekend on a continuous delivery program with NO construction joints. Removing construction joint makes for a more stable product requiring less steel.
So where does David Ball come in? Since starting the David Ball Group in 1970, he has been a serial entrepreneur, retaining a central core of expertise in cement and concrete. David is Director of the Concrete Society and actively involved in BRE and the industry’s BSI technical committee for BS8102:2009.
When such an active and informed mind turned to the problem of reducing concrete’s carbon foot print and increasing its performance, it resulted in action. David’s in-depth knowledge around the subject led him to begin experimenting in the kitchen, and later in the lab. He was looking at combinations of materials that might be used to create a better OPC free cement.
The trials bore fruit and the company took on expanding and developing the new material that is to become known as CemFree.
Due to IP protection, the finer details of CemFree production are still not public. However, detailed property measurements are in the public domain and CemFree can be seen in construction and use at the David Ball Group premises.
The key features of CemFree include:
- A 95% reduction in Carbon emissions during production of CemFree
- Low heat generation during curing
- Low shrinkage (c. 0.5mm/m)
- High compressive strength (10 MPa at 1 day, 30 MPa at 7 days, 44 MPa at 28 days)
- Low water demand
As a result of his work, David Ball and his group were Regional Winners at the annual Shell Springboard event in April 2013, for their novel low carbon cement based concrete.
Because of David’s research, extensive testing and comparison of his new material to equivalent conventional cements for concrete, the David Ball Group is now open to interest in applying this innovative product.
Contact: http://www.davidballgroup.co.uk/site/
Ref: http://www.cipremier.com/e107_files/downloads/Papers/100/37/100037004.pdf
