WHAT IS EFFLORESCENCE?
It is a whitish powder like deposit which often appears on concrete and clay products. This deposit is a residue of a soluble salt carried to the surface of the pavement or wall by evaporating moisture, which leaves a dry powder or calcified deposit upon drying.
A phenomenon reported as early as the 1870's, efflorescence in itself, does not affect the structural integrity of the substrate.
The above is an example of efflorescence in it's worse case scenario. The residue is so great that it has the look and feel of caked flour.
Efflorescence usually rises after installation as a powdery substance but can also form harder patches of calcium carbonate during the manufacturing process. The later being more difficult to remove. Hard, definitive white lines or patches (some appear to have a slight bluish tinge) on paving stones must not be confused with efflorescence. These residues are "lime" and often can not be removed at all or at least without substantial damage to the substrate. These pavers should be changed for aesthetic purposes.
These salts are found in the native soil, gravel or limestone pavement base, in the sand, aggregate, ash or cement used to manufacture concrete brick block or paving stones.
HOW IT OCCURS
An example of Paving Stones stockpiled in the yard of a Paving Stone Manufacturer. You can notice the varying degrees of efflorescence. Paving Stone manufactures accept no responsibility for efflorescence.
Salts dissolve in either the ground water, rain water or water added to the mix the concrete and moves to the surface through evaporation. In basement walls, this travel action has been measured to be as much as 600 mm. Since the sun and warmer exterior air evaporates moisture at a faster rate, it causes a "wicking" action that continues to draw moisture to the exterior surface until the substrate is dry. The efflorescence continues to surface until either the salt or moisture supply has been exhausted - which in most salt cases occurs within 60 days - but has been known to last for many years in extreme cases.
Most efflorescence can only be removed with acidic solutions (such as acid rain over extended periods of time, or acidic based efflorescence cleaners). Although most efflorescence will dissipate with a few years of acid rainfall, STONESAVER does not recommend waiting for this to occur before applying a protective sealer. During this extended waiting period, the Pavement or walls could be damaged by staining, acidic etching, freeze-thaw cycles, pitting, spalling, traffic wear and color fading. STONESAVER recommends a minimum 60 day waiting period ("longer" if dry weather exists) after wall or pavement installation, to allow for the majority of efflorescence to surface, prior to product application.
Upper part of the image is the surface cleaned to a point to show how efflorescence can obscure the true colors making paving stones look faded.
After photo of the Paving Stones after Cleaning & Sealing with STONESAVERs Surface Prep and Paving Stone Sealer.
CONCRETE CLEANER & SURFACE PREP
STONESAVER's Surface Prep is a highly concentrated Efflorescence Cleaner which requires no handling or pre-mixing of chemicals. Surface Prep comes complete with a pre-attached "E-Z Sprayer" (a hose end adapter which connects to your garden hose and disperses the Surface Prep in a cherry scented soapy solution. After a light scrubbing, the E-Z Sprayer adapter (along with an additional hose and gun) can be used to facilitate rinsing the cleaner from the surface. A 1 litre bottle of Surface Prep including E-Z Sprayer adapter, weighs less than 3.5 pounds and easily cleans up to 300 square feet. It is the most user friendly acidic based cleaner available anywhere! After a minimum 24 hour uninterrupted drying period, STONESAVER's Premium Sealers, Water Repellents or Paints can be applied for surface beautification and long term protection. Remember! Sealing over an non cleaned surface will trap in efflorescence, dirt, stains and tire tracks. Never: seal or re-seal a concrete surface which has not been previously cleaned with STONESAVER's Surface Prep Cleaners.