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Concrete floor defects and cracked floor repairs

by Madelein
Concrete floor defects and cracked floor repairs

Prior to applying any resin flooring system, it is necessary to first carry out repairs to any visible damage or cracks in the concrete floor surface, otherwise they will be reflected through the new resin floor finish and become even more visible.

The nature (moving or non-moving) and the cause of any cracks or damaged joints that arise in the concrete floor must also be considered and treated appropriately. This is to ensure that there will be no contamination or adverse future cracking of the resin floor system.

REPAIRS TO SURFACE DEFECTS AND DAMAGE

Repairs to surface damage in concrete floors may be required for many different reasons including:
• Defects in the original concreting work, i.e., honeycombing, voids, unsuitable aggregates such as ‘mudstone’ pop-outs, inadequate surface finishing or curing, etc.
• Damage to concrete floor surfaces caused by impact, wear, abrasion or chemical exposure and attack during service.
With damaged concrete floor surfaces that are to receive a new resin flooring system, the first requirement is to establish the cause and extent of the damage and then to mechanically break out and remove any unsound or weak concrete, always ensuring that any voids in the slab and / or any areas of honeycombing are fully exposed.

The best method of concrete floor repair will depend on:
• The size and depth of repair required.
• The type of resin flooring system to be installed.
• The floor’s future exposure and performance required.
• The time available and the environmental conditions at the time.

Basically, sound concrete floor repairs can be made with cement-based mortars or epoxy resin-based mortars. Larger, thicker areas of damaged floors are usually repaired with cement-based products providing there is sufficient time for them to harden and cure to the acceptable moisture content for the resin flooring system selected. If time is short, then rapid hardening cement-based products or even faster hardening epoxy resin repair mortars can be used.

Epoxy resin repair mortars are much more expensive but generally, installing the new resin flooring system can go ahead the very next day. However, with almost all cement mortars, at least seven days is required before they can be over-coated with the resin floor materials.

“Technically this is because of a combination of reasons – time to dry and harden, time for the mortar to reach an acceptably low moisture content, plus the time required for the mortar’s surface alkalinity to be neutralised by natural atmospheric carbonation,” notes Ian Harrison MD for Technical Finishes.

“We stock and supply a full range of concrete floor repair products including concrete additives to improve the strength and reduce the initial water content of site-batched cement repair mortars. We also carry a range of different concrete repair range of rapid hardening cement-based repair mortars for different thicknesses and areas, plus a full range of epoxy resin/polyurethane -based concrete floor repair product,” adds Chad Tosen, Mapei’s Product Manager for Soft Coverings.

Therefore, whatever surface damage has occurred on the concrete floor, a professional flooring company can provide detailed repair recommendations and method statement instructions, together with all the necessary materials required to do the job.

CRACK REPAIRS IN CONCRETE FLOORS

Cracks in concrete floors can be caused by a number of individual construction problems or a combination of different problems. These include concrete shrinkage, building movement or settlement, machine vibration or excessive loading, plus inadequate or incorrect joint or slab design and construction.

“To successfully repair cracks and effectively seal cracks in concrete floors, it is important to understand the exact reason for the crack and also if any further crack movement will occur. This is obviously a technical issue so a qualified Structural Engineer is normally involved to determine this,” recommends Iain.

On new construction projects, it is especially important to determine the reasons for floor damage as early as possible in order to determine the correct remedial action.

  1. Repairing Moving Cracks in Concrete Floors
    If cracks are likely to be subject to future movement, they are usually treated as joints, cut square, brought through the floor finish and sealed with an appropriate floor joint sealant.
  2. Repairing Non-Moving Cracks in Concrete Floors
    If the Structural Engineer’s assessment is that a crack is non-moving, or at least no longer moving, then it can be repaired and sealed prior to applying the new resin flooring system. The best procedure and materials for doing this will depend on the width, depth and length of the crack. It is likely that the surface will need opening / cutting out to remove any loose materials and then ‘surface sealed’ with a fine epoxy mortar which is pressed into the cracks. Alternatively, where advised by the Structural Engineer, crack repairs can be achieved by structural bonding with low pressure epoxy resin injection products.

CONCRETE FLOOR JOINT AND RISE REPAIRS

Floor movement joints in a new construction are normally sealed with an appropriate joint sealant that will allow the correct movement capability after the floor finish has been applied.

Existing movement joints in concrete floor slabs should also be brought through the new resin flooring system. The nature of the existing sealant will determine if this can be done as bitumen and elastic, polysulphide or silicone sealants cannot be over-coated with resin flooring materials.

If the joint rises are broken or the existing sealant has deteriorated and failed, these joints should be cut out and repaired prior to applying the new resin floor. High-strength epoxy resin mortars are usually the best materials for durable joint arris repairs, because of the high dynamic loads that can be imposed on the joint edges.

The replacement joint sealant is dependent on the type of material that was used for the failed existing joint sealant. Different joint sealant types can be incompatible with certain joint sealing materials, which means that they will not bond with the previous sealant residue on the joint sides. Old bituminous sealants in the joints are a problem and require specialist removal and treatment.

Our sincere thanks and appreciation to the following manufacturers for sharing their expertise allowing us to prepare this article: www.mapei.co.za , www.sika.co.za , www.tal.co.za and www.technicalfinishes.com.

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