When daytime temperatures fall below 5 degrees C, works involving concrete and mortars for renders, concrete repair and screeds are affected. Hardening of concrete and mortars takes longer and strength gain is much slower. This leaves recently applied materials prone to frost damage. Mortars applied in layers, such as concrete repairs and renders, must be left in place for longer before application of further layers. Concrete/ screeds must be left untrafficked by other trades for longer, often with attendant costs for waiting time and extension of construction programs.
Ronacrete manufactures several ranges of products which are suitable for use at lower temperatures. These products can also be used in normal temperatures for earlier access by operatives or for faster return to traffic. Concrete can be laid at lower temperature by replacing OPC or RHPC with Ronacrete rapid cement. These are supplied as a cement replacement product for site batched concrete. They are then added to a number of factory batched mortars for low temperature use and rapid strength gain.
Concrete
RonaFloor Rapid Cement 1 hour and RonaFloor Rapid Cement 3 hour may be used in site batched concrete mixes and will harden at minus 100C. The typical cement content of mix designs is 400kg/m3 and the minimum cement content is 350kg/m3. The rapid exothermic reaction of these products may produce thermal cracking and use of RonaFloor Rapid Cement 1 hour should be limited to relatively small full depth concrete repairs. This will reduce the risk of thermal cracking. RonaFloor Cement 3 Hour is slower setting and bays up to 12m2 may be laid. Larger areas of concrete should be laid hit and miss, missed sections may be laid the following day.
Bay proportions should ideally be between 1: 1 and 1½: 1 to reduce the risk of stress relief cracking. These products are ideal for time limited highway possession works or applications such as slipways and other works in tidal zones. Care should be taken when bonding RonaFloor Rapid Cement concretes surrounding concrete, to ensure that ice does not form on contact surfaces at very low temperatures.
Screeds
Both RonaScreed Mortar and RonaScreed Concrete are polymer modified fast setting and are suitable for use at 00C for concrete slab repair or screeding. RonaScreed Mortar may be applied from 6mm for light duty use and from 10mm minimum thickness for medium to heavy duty use. RonaScreed Concrete may be applied from 25mm minimum thickness for heavy duty use. Both products are suitable for interior and exterior use and resistant to water ingress and frost damage. Both products achieve high ultimate strength with compressive strength in excess of 45N/mm2. The typical compressive strength of RonaScreed Concrete after 12 hours curing at 200C is 25N/mm2. This makes it ideal for weekend possession works. RonaScreed Mortar and RonaScreed Concrete dry within 2-3 days at 200C and 60-65% humidity. As a result, this allows early application of floorings and waterproof membranes or mastic asphalt.
Concrete Slab Patch Repairs
The RonaFloor 1 Hour range of repair mortars will harden at minus 100C. Care should be taken when bonding RonaFloor 1 Hour products at low temperatures to ensure that ice does not form on the substrate. Repairs larger than 1-2m2 may be at risk of thermal cracking. Slower versions of RonaFloor 1 Hour are suitable for larger patch repairs. RonaFloor Repair 1 Hour 2-6mm is suitable for light duty use. RonaFloor Repair 1 Hour 6-50mm is suitable for medium duty use at minimum 6mm thickness and medium to heavy duty use at minimum 10mm thickness. Finally, RonaFloor Repair 1 Hour 25mm+ is suitable for heavy duty use at minimum 25mm thickness.
All RonaFloor Repair 1 Hour products are suitable for interior and exterior use. They are also resistant to water ingress and frost damage. All RonaFloor Repair 1 Hour products achieve high ultimate strength with compressive strength in excess of 45N/mm2. The typical compressive strength of RonaFloor Repair 1 Hour 25mm+ after 1hour cured at 200C is > 15N/mm2, typical compressive strength after 1hour cured at 50C is 5N/mm2. RonaFloor Repair 1 Hour products are ideal for application of patch repairs at low temperature. They are also used patch repairs in mild or warm temperatures in tidal zones or when limited closure of an area is possible.
Vertical and Overhead Repairs to Concrete Structures
Ronacrete has formulated RonaBond HB40 Ultra Rapid for cold weather application. It is also suitable for application of multiple layers of mortar per day in mild and warm weather. Typical compressive strength after 1 hour cured at 200C is 6N/mm2. Application of two layers in a day is possible at temperatures below 50C. Ultimate compressive strength is ≥ 35N/mm2. Minimum applied thickness is 6mm and typical maximum applied thickness is 50mm vertically and 30mm overhead. Greater layer thickness is achievable in smaller repair pockets. RonaBond HB40 Ultra-Rapid is suitable for use when conditions are too cold for normal setting repairs or for repairs to concrete sea walls, jetties etc. in intertidal and supratidal zones where repair products might otherwise be subject to cement washout.
