Why is concrete cleaning required?
In order to prepare concrete structures for repair their surface will often need cleaned for various reasons such as to remove contamination or allow repair materials to strongly bond to the surface.
How do you clean concrete?
There are five common cleaning methods used for concrete.
Chemical cleaning
Chemical cleaning compounds are most often used when concrete has been contaminated with oil grease or dirt. Specific chemical compounds are used based on the stain: pH-neutral cleaners for mild dirt, acids like muriatic or oxalic for efflorescence and grime, alkaline degreasers like sodium or potassium hydroxide for oil/grease, and biological agents like enzymatic cleaners for organic stains.
Solvents should not be used to clean concrete.
Appropriate chemical agents, water, protective gear, and tools like brushes or power washers are required to carry out the test. After the right cleaner is selected for your stain, it is applied following manufacturer instructions, possibly scrubbing for deep stains, and rinsed thoroughly to clear residue and dirt, repeating if necessary for stubborn stains.
Mechanical cleaning
Mechanical cleaning of concrete surfaces involves using equipment like scabblers, scarifiers, grinders, and impact tools to remove a thin layer of concrete or to roughen the surface for better adhesion of new material with the degree of surface cleaning achieved, depending on the tool used and the abrasive material's nature.
While mechanical preparation is efficient for achieving the required surface texture, it's crucial to monitor the amount of concrete removed to avoid excessive material loss.
In some cases, this method may not achieve the final surface cleanliness desired, necessitating an additional cleaning method to prepare the surface fully for repair or coating applications.
Shot blasting
Shot blasting is a highly efficient technique for concrete surface preparation, ideal for creating a uniform profile suitable for thin overlay repairs. It employs a wheel to project steel shots at high velocity, cleaning and profiling the surface simultaneously.
This process strips away dirt, coatings, and produces a roughened texture that enhances the adhesion of subsequent applications, leaving the concrete surface dry, allowing immediate application of bonding agents, coatings, or overlays.
Water jetting and sand blasting
Water jetting and sandblasting are two similar concrete surface preparation methods.
Water jetting, using pressures between 40 to 70 MPa, can include heated water or additives for enhanced cleaning, and is effective for final surface preparation but requires skilled operators and is not suitable with epoxy mortars.
Sandblasting adds wet sand to help remove dirt and deteriorated concrete, creating minimal dust. It's a slower method and requires an effective oil trap on the air source to prevent surface contamination.
Acid etching
Acid etching of concrete involves applying muriatic or phosphoric acid to the surface to remove the cement paste, creating a roughened surface ideal for coatings or overlays and eliminating laitance and dirt.
Before acid application, it's essential to clean the surface of grease and oil. Once the acid reaction stops, it should be thoroughly rinsed off, using brooms to clear reaction products. Post-etching, the surface must be checked with pH paper to ensure all acid has been removed.
