Lime concrete

for floors with exposed aggregates/tamped finish

350-400 kg of Saint-Astier® NHL 5 or 300-350 kg of HL 5 (Hourdex® or Tradiblanc®) cubic metre of aggregates consisting of a ratio sand/aggregates 1:2 (12–18 mm aggregate and approximately 15–16 litres of water per bag of  Saint-Astier® NHL 5). Semi dry concrete requires less water but should be wet enough to show binding when squeezed in the hand.

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. Mixing time: at least 10 min, should not exceed 15 minutes.

Lime concrete should be laid on a compacted, 75-50 mm sub-base of clean screened aggregate (150 mm minimum). The greater the thickness of the sub-base, the better the insulation. Damp proof membranes are not necessary. Lime concrete can be laid directly on to sub soils containing clays if they have had a 20 mm layer of Saint-Astier® NHL 5 or HL 5 (Hourdex® or Tradiblanc®) rotovated into them and have been compacted. Subsoils should be analysed before proceeding. Damp proof membranes are not necessary (though Geotextile or similar can be used).

The concrete is placed in a single layer of 50 mm, or 2 layers of 50 mm to make a 100 mm layer depending on purpose. 50 mm will be sufficient for normal foot traffic and 100 mm 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).

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 first.

Mist lightly with clean water for 72 hours or more depending on conditions (twice a day at least during the first 48 hours and once a day the following 7 days). 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 8oC-30oC with low to average humidity.

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.