Concrete repairs – Where do I start?
Whether you're repairing an ageing asset or rectifying defects in a new construction, there is a concrete repair solution for every purpose. To help contractors get repairs done right the first time, Fosroc is on hand with product selection and application advice.
"Depending on the defect and the age of the structure, every repair is different. Using the right products and applying them correctly is crucial to avoiding a cycle of repairing the repair," says Hamid Khan, Fosroc's ANZ Specification Manager for Concrete Repairs and Grouts.
Here are Hamid's top solutions for five common concrete defects.
Non-moving structural cracks
“Cracks provide easier access to oxygen, moisture, chlorides and other corrosive agents that create conditions suitable for accelerating the electrochemical corrosion process,” says Hamid.
Example of a non-moving structural crack
Solution
Non-moving structural cracks in critical elements can be treated with low viscosity epoxy injection or gravity feed methods. Fosroc Nitofill LV is injected into concrete cracks to consolidate the structure and protect the reinforcement. While Conbextra EP10 is ideal for gravity feed repairs in concrete slabs.
Honeycombing
The extent and depth of honeycombing will determine the best solution, says Hamid, “Honeycombing is often revealed when the formwork is removed. If it is not treated properly, it creates an ingress risk from moisture and corrosive agents.”
Example of honeycombing
Solution
Fosroc's market-leading Renderoc range is ideal for replacing the damaged concrete.
- For patch repairs, Renderoc HB40 Plus and Renderoc HB70 Plus are extra high build mortars that can be applied by hand.
- For large volume repairs where recasting is required, Renderoc LA55 Plus is a fluid micro-concrete used for the form and pour technique. Guncrete E is recommended for large vertical and overhead repairs, with a dry-spray application.
Low cover, corrosion & spalling
Low cover is an inadequate distance between the reinforcement and the outer surface of the concrete, exposing the steel to corrosive elements. As steel rusts, the expansive pressure results in concrete spalling. Spalling symptoms range from rust stains to flakes or chunks of concrete breaking off.
Example of low concrete cover
Solution
Fosroc Renderoc ST 06 is suitable for precast and in-situ reinforced concrete, making it an ideal solution for rectifying low concrete cover. Used from 0.5mm to 5mm deep, it conforms to the requirements of EN1504-3 Class R3.
If corrosion and spalling have already initiated, follow these steps:
- Step 1: Control the corrosion. Fosroc's Nitoprime Zincrich is an anti-corrosion primer formulated for use with Renderoc mortars.
- Step 2: Once the barrier protection is applied, Renderoc and Guncrete E repair mortars can be used to increase concrete cover or replace the damaged concrete. Fosroc's Paveroc and Patchroc offer fast-setting mortars for floors and pavements.
Chemical attack
This common concrete problem relates to the water and waste industries, as well as chemical plants and food and beverage producers. Aggressive chemicals can weaken and crack the cement matrix. For new and existing structures, Fosroc has solutions to protect and repair concrete in these aggressive environments.
Example of chemical attack
Solution
The following mortars offer excellent surface protection.
- Renderoc G is a geopolymer acid-resistant repair mortar and lining for use in highly corrosive environments. It offers long term protection for potable water structures, sewer assets, acid bunds, and concrete within the sugar, dairy and wine industries.
- Renderoc CAC is used to rehabilitate sewer infrastructure damaged by biogenic corrosion or protect new infrastructure. It is available in a wet or dry spray application.
- For patch repairs in aggressive environments, Fosroc recommends Nitomortar 903 with F4 Fillers.
Water leakage
Water leakage is the final problem in Fosroc's top 5 most common concrete defects. "Filling cracks and pores quickly is the best strategy to keep concrete dry and reduce the risk of early onset corrosion," says Hamid
Fixing water leakage
Solution
Fosroc offers two polyurethane injection resins that can eliminate leaks in reinforced concrete structures. Nitofill PU150 is a hydrophilic flexible polyurethane grout for sealing leaks in cracks and joints. For larger cracks and voids, Hamid recommends Nitofill PU130 – a hydrophobic polyurethane semi-flexible grout.
Find out more
- Download our Guide to Concrete Defects, and Guide to Concrete Defects for potable water applications.
- Download the Fosroc Concrete Repair Solutions brochure.
- Try our product selector here.
- To request a site visit or specification assistance contact us via the form at the bottom of this page.
