Sun Joe SPX3000 2030 Max PSI 1.76 GPM 14.5-Amp Electric High Pressure Washer, Cleans Cars/Fences/Patios

 Sun Joe SPX3000 2030 Max PSI 1.76 GPM 14.5-Amp Electric High Pressure Washer, Cleans Cars/Fences/Patios

Brand     Sun Joe
Power Source     Corded-electric
Color     Cleans Cars/Fences/Patios
Item Dimensions LxWxH     15.6 x 13.5 x 33.9 inches
Maximum Pressure     1450 Pound per Square Inch
Item Weight     31 Pounds
Hose Length     20 Feet

 About this item

•     Power Source Type: Corded-Electric

HOW TO CLEAN CONCRETE SURFACES OF GREASE, OIL AND DIRT

In Concrete Surface Preparation - Part I , we discussed the detection, removal, and repair of unsound concrete. The next step is to remove the contaminants from the concrete. However, we cannot proceed directly to sandblasting, for the same reasons that steel sandblasting does not start immediately.
Dirt, dust,  and other  loose contaminants  will inhibit build-up and can be removed by first sweeping, vacuuming, blowing with air, or spraying with water.

Hydrophobic materials, such as  oil, grease,  and  stripping lubricants  also inhibit adhesion and must be removed. It's tempting to remove them by sandblasting the contaminated layer, but that can exacerbate the problem by spreading contaminants over previously uncontaminated areas. Recommended methods of removal are  scrubbing with a brush, water and detergent, steam cleaning, and low pressure washing (less than 5000 psi) . Some chemical cleaning methods are appropriate, but solvent cleaning is not. Unlike steel, concrete has pores and cracks that solvents can enter, which inhibits adhesion formation.

A detailed discussion of acceptable methods for surface cleaning can be found in SSPC SP 13 / NACE No. 6 - Concrete Surface Preparation.

Efflorescence

Efflorescence  is a powdery, crystalline deposit that slowly forms as moisture seeps soluble salts to the concrete surface.

Efflorescence is an aesthetic problem, not a structural one, but must be addressed when the concrete surface serves as a cover. If not done, efflorescence will cause unsightly stains under sealers and decorative finishes.

Being a soluble salt, efflorescence can be removed  by scrubbing with a brush and water, power washing, or with a light blast of abrasive steam . However, unless the underlying moisture problem is resolved, the efflorescence will return.

Humidity problems

If the relative humidity of the air is less than that of the cured concrete slab, the moisture will be drawn from under the slab to the surface, causing efflorescence, mold, and emulsion of flooring adhesives. Where sealants and other waterproof coatings block vapor flow, delaminations and blistering can occur. The solution is to install a vapor barrier under the slab.

There are two common tests for the relative humidity of concrete:

Plastic sheeting test. A plastic sheet is glued to the concrete surface and left for 16 hours or more, then removed and inspected for condensation. See ASTM D4263

Calcium chloride test. A plate with calcium chloride is weighed, placed on the concrete surface, and sealed under a dome. About sixty or seventy-two hours later, the plate is weighed again. The increased weight of the sample indicates the amount of moisture absorbed, which is used to calculate the moisture vapor emission rate (MVER).

Grout

Grout  is a weak, friable layer of cement and fine aggregate materials carried to the surface by water exiting the concrete. It is the result of excess water in the mix or excess water that has occurred during curing, and  is always present to some degree in new concrete.If grout is not removed, repairs, layers and coatings, because the friable layer has poor material strength. However, cement grout is tough enough to warrant removal by abrasive blasting, sandblasting, grinding, high pressure water blasting, or acid washing.

Grout appears when the concrete surface is scraped with a sharp object, leaving a dusty residue.

Curing compounds  are applied during the curing process to seal the concrete and retain water for cement hydration. By sealing the pores in concrete, curing compounds inhibit the adhesion of mortars and coatings. Adhesive layers and coatings above  present the same problem. The solution is to remove the concrete layer below the penetration level of the compound by abrasive blasting, shot blasting, high pressure water blasting, or by mechanical means.




With healthy, contaminant-free concrete, all that's left is to properly scrape the surface, but to what extent? In Part III of our series on Concrete Surface Preparation, we will discuss the specifications of structures and blasters to agree on the number of profiles needed, and examine the various concrete surface preparation methods, their advantages and disadvantages, and their applications.