Making stronger / better FC is the topic of most Foam Concrete R&D work. So it will be yours if you make FC for whatever reason. Knowing the basics will help a lot in avoiding expensive time consuming mistakes.
Below is an overview of the aspects.
The conclusion I have come to so far is that the following steps and ingredients are a reasonable “beginners guide”. I left all the references to studies out to make this easier to read. this page is just to give an overview of the topics. If you serious about making FC learn all you can about it. It is possible to make FC with a density of 1200 Kg/m3 and a MPa of 18, but is requires selecting the right ingredients and following a strict procedure.
Foaming agent: must make a stable and small bubble size between 0.5 and 2 mm with the average bubble size distribution over a narrow range for the best results.
Foaming machine and method:
The dry method seems to produce “better” foam to make FC.
The machine needs to produce foam of consistent density.
Mixing the foam into the mortar: This need to be done in such a way that the bubbles do not collapse, are evenly distributed, the shape is a “perfect” ball, and are separated from each other.
Adding ingredients to the mortar
So far I have found the following relevant topics
- Adding Silica fume and or Fly-ash
- Adding super-plasticisers
- Water cement ratios and Mpa relationship
- adding fibers
- adding nanocarbon material
Addition of Fibers
These can be classified in two types, one that reduces the micro cracking during curing and those providing tensile strength when cured.
Adding PE and other synthetic fibers are used to reduce cracking during curing
AR Glass fibers and steel to increase tensile strength.
The addition of fibers can also weaken the tensile strength, if the fiber strength is lower than the FC tensile strength!
Adding steel fibers is problematic as they sink to the bottom of the FC mix
Focusing on making a good foam to make FC
Use agents that create a foam that does not collapse before the FC is set
Keep the bubble size small, between 0.5 and 2 mm.
Make the average bubble size distribution as small as possible.
Type of foaming method and equipment used.
Use of Three phase foams can help to make a ‘better” FC
Making the mortar
Use certified Portland cement
Use clean water
Pay attention to the water cement ratio, this is critical!
Use fine sand, sand less than 2 mm, optimum, 0.5 mm gives a better result than coarse sand.
Use additives such as fly-Ash, silica fume, and plasticisers to make FC.
As the curing process is a chemical reaction needing water, do not let your creation dry out.
Best to take it out of the mould after 10 to 12 hours, if you use one, and wrap it in plastic for 28 days!
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