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| Concrete should be placed as near to its final position as possible. It
can then be roughly levelled off, leaving it a little proud of the forms to allow for
compaction. Full compaction of concrete is vitally important to remove the entrapped air,
leaving it dense and durable. Concrete of medium workability can be readily compacted
using a compacting beam in an up-and-down motion. This action should result in a surface
where all the voids are ‘closed’. Slabs can be finished by simply tamping with
the compacting beam, by brushing, or by using a wooden or steel float. The timing of the
final brushed, tamped or trowelled finish is very important. Premature finishing draws
excess water and cement to the surface and this invariably leads to rapid surface
deterioration and poor resistance to wear. |
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1. Brush finish. |
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2. Steel float finish |
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3. Wood float finish |
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| Concrete needs to be protected to prevent moisture loss especially for the
first week after placing. The interval between final finishing and the start of curing
should be kept to a minimum to avoid damage to the surface. The more usual methods for
curing include covering with damp sacking, damp sand or polythene sheet or spraying with
water. In cold weather polythene sheet covered with straw, tarpaulins or other
insulation material provides protection against frost. |
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| 7 bags of Irish Cement, together with 2 tonnes of damp gravel will produce
just over 1 cubic metre of concrete. This is sufficient material for 10 square metres of
100mm thick slab. |
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| 6 Bags of Irish Cement, together with approx. 2 tonnes of damp gravel will
produce approx. 1 cubic metre of concrete. |
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| 5 bags of Irish Cement, together with approx. 2 tonnes of damp gravel will
produce just under 1 cubic metre of concrete. |
