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Technical & General

General Tips
The following tips should help you keep your paving looking at its best for longer. Please note that although sometimes unsightly, blemishes or stains are unlikely to affect the performance of the paving in any way. Always follow manufacturer’s instructions when using cleaning equipment or materials.

  • Test a small area before cleaning the patio.
  • Do not use salt to die-icer your patio.
  • Dark patches are due to different weathering and exaggerated by efflorescence. As with efflorescence, the dark patches will generally disappear in time.
  • Pressure washers can be used to clean the patio. Do not pressure wash too strongly as you may damage the surface of the paving.
  • Fungal and algae growths can be cleared by spraying with fungicide.
  • Regular washing and brushing should be adequate to maintain your patio.
  • If using patio cleaner, use sparingly (once or twice during the lifetime of the patio) as this my affect durability.
  • Sealants can be used, but they can affect the colour of the paving.

Colour
Due to the phenomenon of differential curing, slight colour and shade variations do occur in individual coloured concrete products. Site conditions, seasonal manufacture, or naturally occurring variations in the aggregates used can also cause variations. This is generally considered to enhance the natural stone effect and the colours will invariably weather together in time.

Ordering
In respect of this it is suggested that when laying paving the flagstones are ordered as a total batch and drawn from several packs at the same time to enhance any colour variation. Choice of colours should be made from actual materials rather than the colour photographs herein.

Weathering
Just as natural stone the appearance of concrete products will weather and change, especially after a period of time exposed to the elements.

Sizes
Concrete paving is manufactured to capture the authenticity of natural slabs and as such they do vary in thickness. All sizes are nominal and customers should check with their supplier. Fissures can occur on larger individual slabs as natural results of shrinkage, this does not alter the durability of the product.

Efflorescence is a Natural Phenomenon. It is the name given to crystalline or powdery deposits, normally white, which form on the surface of in-situ concrete. Precast concrete, concrete blockwork and brickwork.

Primary Efflorescence
Occurs in the time from when the product is in the saturated state to when it is dry, and normally immediately after the product has set.

Secondary Efflorescence
Occurs at a later stage, when the product is in service and has been exposed to wet humid conditions.

Conditions where condensation or rising ground water can permeate the concrete over an extended period, followed by slow drying, this could promote the formation of efflorescence.

Prevention
It is not possible to predict precisely when, or if, efflorescence will occur as relatively minor changes in the quality of the concrete, the curing conditions and the environment can cause its formation.

Mechanism
Concrete products are made from natural occurring materials, mixed with water. Once a concrete product is made and subjected to weathering, moisture penetrates into the pores of the product and dissolves an element of lime contained within. Under damp conditions this solution, calcium carbonate crystals which are white in appearance, migrates to the surface and usually forms an extremely thin layer giving the effect of efflorescence.

Efflorescence will be eroded by rain, which is slightly acidic. As nature causes the problem, nature and time hold the cure.

Removal
It can be removed mechanically by dry brushing or shotblasting the surface or by washing with dilute phosphoric acid, dilute hydrochloric acid or a commercially available masonry cleaner. With acid treatment it is recommended that the surface is first soaked with water to prevent acid penetration and is thoroughly washed after treatment.

However, both techniques can alter the appearance of the concrete by changing the surface texture and may also damage the concrete surface.

Before attempting to remove efflorescence by these techniques it is recommended that trials should be carried out on samples, or a limited area, in order to assess the effect on the appearance.

Efflorescence is a natural phenomenon and one that does not affect the durability and performance of the concrete in question.

 

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