Hyson Cells with concrete
Comparison with industrial block paving
Summary of advantages
- Cost saving on initial construction
- No maintenance. Hyson Cells does NOT have to be lifted and replaced after 8 years as would conventional block paving.
- Less deflection than conventional industrial block paving.
At the Kaserne trials the Hyson-Cells exhibited a deflection of 1.65 mm (test 9) against 2.76 mm (test 11) for the standard design block paving which was constructed according to CSIR standards.
- Better resistance to "punching through" into the underlying material than conventional industrial block paving
- Better resistance to slew than conventional industrial block paving
- No pumping of fines at Hyson-Cells joints
- Less layerwork needed or superior performance to conventional block paving on the same layerwork
In some areas such as in Namibia the presence of chlorides is a major errosive factor. The Hyson-Cells method eliminates the need for reinforcing steel and so the presence of chlorides is less important than is the case with conventional reinforced concrete.
The Hyson-Cells method allows the use of up to 30% Fly Ash. Industrial blocks made in South Africa utilising steam and high pressure can only utilise 20% Fly Ash.
The higher Fly Ash content in Hyson Cells will exhibit improved properties such as compactability and reduced bleeding in the green state whilst it will impart increased durability characteristics such as lower permeabilities, reduced chloride ingress and diffusion, sulphate resistant in moderate sulphate environments, resistant against Alkali Aggregate Reaction and improved long term strengths. The use of 30% Fly Ash can reduce the amount of free chloride by as much as 50%.
Fosroc recommend the use of 2% SP430 super plasticiser to increase the density of the concrete and to reduce water demand.
Possible use of "Grouted Concrete"
The Hyson-Cells may be filled with grouted concrete. This allows construction where stone is available that is not suitable as conventional concrete aggregate. Again Namibia comes to mind. However it is important to understand the differences in principle of grouted concrete as compared to conventional concrete and the need for supervision of grout penentration. (See Fills Topic)
No need to lift the Hyson-Cells
Unlike conventional block paving it is not expected that the Hyson Cells will have to be lifted for maintenance1. The extra durability results because the gap between Hyson Cells blocks is only 10 to 20 micron as compared to 2 mm to 6 mm with conventional blocks. Fines cannot therefore be pumped to the surface of the Hyson-Cells paving. At the comparative Kaserne trials the conventional paving was observed to move under concentrated loading and with wheel slewing. The Hyson-Cells paving did not move under the same conditions.
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