Foamed Concrete Unit
The unit is a foamed concrete mixer and pumping system which in its current form can produce a 1000kg/m3 plastic density foamed concrete at an output of 20 cubic metres per hour.
COLLOIDAL MIXERS AND 3M3 BASE MATERIAL CENTRAL
The unit was designed to allow the base material (sand, cement and water) to be either loaded by hand directly into one of the two cycloidal mixers or to accept deliveries of pre-mixed base material that can be tipped straight from the truck mixer into the base material holding tank.
This dual system enables small amounts of foamed concrete (1 or 2 cubic metres) to be produced when required, whilst at the same time allowing the system to cope should larger amounts of foamed concrete be required.
When batching material by hand the cement, sand and water is tipped into the colloidal mixers in the correct ratio. This usually done by bags, so a 2:1 one mix would be two bags of sand to one bag of cement etc.
The water is then added via the flow meter until the correct base material has been achieved. Once mixed, a lever is pulled and the mixer empties the base materials into the central holding tank. Each mixer will mix upto 150 litres of base material, with the central holding tank, holding 3000 litres of base material.
The two colloidal mixers allow for two mixing crews to operate at the same time for maximum output or the system can be operated using just one mixer when small outputs are required. Each mixer will mix approximately 5 cubic metres of material per hour (dependant on mix design) to give a total output of 10 cubic metres per hour of base mix.
When accepting loads of base materials in a ready mixed form, the mixed base materials can be simply tipped straight into the 3 cubic metre central holding tank from the Readymix truck, without the need for further mixing. Once the holding tank is full of mixed base materials (or as full as is required) the base material can be drawn off from the holding tank and used to make the foamed concrete.
The base materials are drawn from the tank by a 2 stage mono type pump where they are pumped to the foam generating system. The foam system draws up water, foaming agent and air in the correct ratios and processed them into a thick stable foam (similar in appearance to shaving foam) and it is this foam that is mixed with the base materials to produce foamed concrete.
Once the foam is produced, it is pumped to the Mono pump outlet where it is injected into the base materials via a static inline mixing chamber. The foam and base materials are forced through a series of mixer blades where the two are mixed together to produce the foamed concrete. By varying the speed of the foam and the speed of the base materials entering the mixing the density of the foamed concrete can be altered to suit the requirements of the project. This adjustment of the ratio between foam and base material is extremely important as it is this ratio that dictates the final properties of the foamed concrete, such as strength, fluidity, durability etc. So it is vital that this ratio once set is maintained. On this unit this is done by way of a computer controlled system that tracks the speed of the mono pump and then adjusts the speed of the foam generator so that the ratio between foam and base mix is maintained and hence the foamed concrete density is also maintained.
In its current design the system has a mono pump with an output of up to 10 cubic metres per hour of base material, and a foam generator with an output of 10 cubic metres of foam, to give a maximum output of 20 cubic metres per hour of an 1000kg/m3 plastic density foamed concrete.
Obviously by adjusting the ratio between base materials output and the foam generator output, densities between 500kg/m3 and 1500kg/m3 can be achieved, but this will effect the foamed concrete output of the system.