Concrete Crack Repair and Cement Injection
Why is my concrete cracking?
Concrete crack repair: the rigidity and strength of concrete afford structures resistance from deformation. Those same characteristics also prevent flexibility of the concrete structures to move in response to environmental or volume changes.
While concrete cracks are usually the first sign of distress, it is possible for deterioration to exist prior to cracks appearing. The thorough evaluation of concrete cracks is important in determining whether the cracks will compromise the structural integrity, reduce durability or are aesthetically unacceptable. The environmental conditions around concrete cracks influence the extent to which it affects the integrity of the structure.
Concrete cracks that are crossed by steel reinforcement are usually stable (depending on the root cause and the amount of steel reinforcement that cross the cracks) and considered dormant. While dormant concrete cracks don’t threaten the stability of the structure, the durability and aesthetic issues must be addressed. Dormant cracks have stable widths and can usually be repaired with either a rigid or a flexible material.
Active concrete cracks in a slab are usually working joints and therefore should be treated in the same manner as joints. Repairs to active concrete cracks should be from a flexible material that will accommodate future crack movements. Active cracks may require more complex repairs that include eliminating the cause of the cracking so as to ensure a successful long-term repair.
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Types of cracking concrete
Cracks in the concrete as clearly visible, there are types of cracks that require specific techniques for repairs.
In very hot weather concrete will expand as it gets hotter, this puts great stress on the slab. As the concrete expands, it will push against any object in its path, such as an adjacent concrete slab or a brick wall, and if neither of them has the capacity to flex then the subsequent force will cause concrete cracks.
Rapid drying of the concrete slab will also increase the chances of concrete cracks. Concrete goes from a liquid or plastic state to a solid state due to its’ chemical reaction with water; this continues for days and weeks after a concrete pour.
Lack of Control Joints
Control joints in a concrete slab control concrete cracking. If the concrete slab lacks control joints, or the control joints have been installed incorrectly, concrete cracks will occur.
Heaving is caused by soils expanding when they absorb moisture, and as the amount of water in the ground is often uneven, the movement of the concrete slab will be as well. Also, the ground drying out too much due to tree roots, long dry seasons, etc. will also affect the concrete slab movement and cause concrete cracks.
This occurs when the concrete surface is finished prematurely. At the time of curing, the water must bleed to the surface, but if the slab is finished before the bleeding process occurs, the water will be trapped under the surface. Due to expansion and other factors, the water will try to escape through the slab and leave concrete cracks along its way. Usually does not pose a threat to structural integrity.
Poor Design & Construction
Some of the most common causes of concrete cracks is poor design, construction defects, exposure to the elements and inferior materials.
A primary cause of concrete cracks is shrinkage due to excess water in the mix. As the concrete hardens and dries it shrinks; this is due to the evaporation of the excess mixing water. The wetter the concrete mix, the greater the shrinkage.
Concrete is a very strong building material but it does have its limits. Placing excessive amounts of weight on top of a concrete slab may cause concrete cracks and this type of cracking may indicate deep structural damage.
Settlement cracking is caused by movement of the sub-grade or footing. If the ground where the concrete was poured was not compacted adequately, the slab will sink until the ground is compacted enough to support the structure.
Concrete Crack Repair – How to fix it
Concrete cracks may affect appearance only, they may be a sign of durability issues or an indication of structural distress; they may represent the total extent of the damage or they may point to problems that are much greater. The significance of concrete cracks depends on the structure itself and the nature of the cracking. Successful long-term concrete crack repair procedures must address not only the cracks themselves but the cause of the cracks as well, otherwise, the concrete crack repair may end up as a temporary fix only. It’s critical that each situation is individually assessed and that the correct repair technique is determined. Once the cause is established and the type of concrete crack determined, then a suitable concrete repair method is selected; some common methods include:
Epoxy Crack Injection:
This method of repair is used for concrete cracks as narrow as 0.05mm. This technique consists of establishing entry and venting ports at close intervals along the cracks, sealing the cracks on the exposed surfaces and injecting the epoxy under pressure. It’s important to note that unless the cause of the concrete cracks is corrected, it will probably recur near the original crack. If the cause cannot be removed then the crack can be routed and sealed (see below method).
Routing and Sealing:
This method of repair is a common technique used for remedial repairs where structural repairs aren’t necessary. This method involves enlarging the crack along its exposed face and filling and sealing it with a suitable joint sealant. This is used to treat fine pattern cracks and larger isolated cracks.
This method of repair involves drilling holes on both sides of the crack and grouting in U-shaped metal units (staple or stitching dog); with short legs that span the crack. The legs of the metal unit are anchored into the holes with either a non-shrink grout or an epoxy resin-based bonding system.
Drilling and Plugging:
This method of repair consists of drilling down the length of the crack and grouting it to form a key, the grout key will prevent transverse movements of the section of concrete adjacent to the crack. This repair technique is suited to cracks that run in reasonably straight lines and are accessible at one end (i.e. a retaining wall).
This method of repair consists of low viscosity monomers and resin which are used to seal cracks with a surface width of 0.03 to 2 mm, by gravity filling. The lower the viscosity, the finer the cracks that can be filled.
This method of repair involves filling wide cracks with cement grout. While this repair method is very effective in stopping water leaks, it will not provide a structural bond to cracked sections of the concrete.
Will epoxy fill cracks in concrete?
There are different methods and techniques available for concrete crack repairs. Filling a concrete crack with an epoxy is one method that can be used but is dependent on the width, length and depth of the crack. Before completing an epoxy crack injection, the cause of the crack must be resolved and no further movement permitted; if the concrete is still subject to additional movement then an epoxy crack injection is not recommended. Additionally, concrete cracks that are the result of corroded steel should not be repaired with an epoxy injection as the steel will continue to decay and new cracks will likely appear.
Does epoxy bond concrete?
Yes, epoxy bonds concrete, and most other construction materials, firmly and permanently to a hardened concrete surface. The bond strength of the epoxy is greater than the tensile strength of the concrete itself and therefore if there is a failure it will be a failure of the limits of the concrete’s strength and not that of the epoxy.
HOW BUSS CAN HELP WITH CRACKING CONCRETE?
Drawing on our experience and industry best practice, BUSS’ team have been servicing our clients in the commercial, industrial, residential, mining and resources market for more than 20 years. Our concrete crack repair team have been applying their expertise in completing condition assessments, creating action plans to remediate issues, developing repair methodologies, providing product recommendations and undertaking repairs via trusted techniques to eradicate underlying problems and renew assets to their desired state for our clients.
Our proven track record in effective remedial solutions and quality workmanship, supported by our affiliation with leading industry organisations – Australian Institute of Waterproofing, the Australasian Concrete Repair Association and the Strata Community Association, along with our Cert III accredited applicators, offer our clients peace of mind for all their concrete repair needs. Our association with these leading organisations allows us the advantage of being one of the most qualified, trusted and reputable remedial contractors in WA.
BUSS is your ‘go to’ contractor for all your concrete crack repair needs in Perth and the metro area, as well as Regional WA. For more information, please feel free to contact us below. Call us on 08 9444 1732 for more information.
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