Lime Concrete for Floors, exposed aggregate / tamped finish

Ingredients

400 KGs NHL 5 per cubic metre of aggregates consisting of 1 part sharp sand: 2 parts 12 - 18mm aggregate and approximately 15 - 16 litres of water per bag of NHL 5 (30kg.). Semi dry concrete could have a lesser water addition. It should however be wet enough to show binding when squeezed in the hand.

Mixing

Mix dry to achieve a uniform colour in a pan mixer or roller pan mill, slowly add clean water until semi dry, just sufficient to allow mix to bind when squeezed in hand. Free fall mixers can cause balling.

Substrate

Lime concrete should be laid on a compacted sub base of clean 75-50mm screened aggregate (150mm minimum). The greater the thickness of the sub-base, the better the insulation properties. Damp proof membranes are not necessary. Lime concrete can be laid directly on to sub soils that contain clays that have had a 20mm layer of NHL 5 hydraulic lime rotovated into them and compacted (sub soils should be analysed before proceeding). Damp proof membranes are not necessary.

Laying

The concrete is placed in a single layer of 50mm, or 2 layers of 50mm to make a 100 mm layer depending on purpose. 50 mm will be sufficient for normal foot traffic and 100mm for light vehicular traffic. It should be well rammed either by hand or with a mechanical compaction plate to the desired level. Form mechanical key between layers. Lay green on green (within 24 hours).

Finishing

Exposed aggregate finish: after 24 hours the surface of the compacted and levelled concrete is brushed with a stiff yard broom initially, then a soft brush. On large areas it may be necessary to treat the surface of freshly compacted concrete with an inhibitor to hold back the set.

A trial panel should always be done.

Curing

Light mist with clean water for 72 hours or more depending on conditions.
Never lay on a frosted or exceedingly hot surface. Protect from extreme heat, freezing, excessive wind, strong direct sunlight and rain. Ambient temperature range should be
5oC-30oC with low to average humidity.

Protection

Foot traffic should be avoided for 7 - 10 days depending on the weather. Cover with protective walkways 12 hours after placing. These should remain in place for at least 2-3 weeks or longer if possible.

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For further Guidance, contact your St Astier Distributor.
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