Nothing wrong with the block. It has what is called efflorescence. Usually caused by water, perhaps in back, bringing salts along and evaporating in front, leaving the salts.
its definitely deteriorating and I realize it is efflorescence, but only along the 3rd course. Why not the other courses? the wall is free standing, there is no water ever against the wall other than rain
I have seen a case similar to this where the block was not grouted solid below grade and the cores were filled with water below grade. The water vapor would migrate up through the block until it came to the first continuous bond beam. Then the water would seep out through the face shell just below the bond beam. It was significant enough that the face shells were spalling in the courses just below the 1st bond beam course due to freeze-thaw action. We had them fill the cores solid below grade, which is a pain, but I have not heard any complaints or seen any issue since.
What is the height of the soil behind the wall? the back soil looks slightly sloped towards the wall. Could the soil be up to course 3, and rain accumulating and running into the wall at the top of back-soil? This would cause efflor.
And i have seen many walls with efflor that are free standing, no soil; ie dumpster enclosures. Efflor, is not deterioration (we may just not be able to see the deterioration in the photo), it is the removal of salts/calcium from the block or water passing through the block.
As others have noted, this is simple efflorescence. This will occur whether the block cells are filled or not. In some instances, incomplete filling of cells (creating voids) will exacerbate the problem....in fact, this might be at play here since usually the efflorescence follows the water accumulation and would be expected to be worse near the bottom of unfilled cells. Since this occurs at mid-height of the wall, it is either related to voids in the filled cells or just an accumulation of more calcium in the block or fill at these locations to allow solutioning by the water intrusion and evaporation to create the residue.
Other probable causes:
1. Incomplete application of a surface applied sealer
2. If the block has a waterproofing admixture (Prime-A-Pell or similar), it is possible for the admixture to be incompletely dispersed in the block, so you get odd patterns of efflorescence as a result
3. Variations in density of the block to allow variations in water intrusion, thus differences in efflorescence pattern.
Also...this is not "deterioration" of the block at this stage. The efflorescence can be removed with a light acid wash (I recommend citric acid, but muriatic can also be used), followed by a surface application of a siloxane sealer (that must be re-applied about every 2 or 3 years).
1.) It is not deterioration, but a temporary surface deposit on the wall that can disappear with the weather or be cleaned of if i, but it is definitely not deterioration, it is not permanent unless it is fed moisture from a continuous source (like soil and standing water. Often, it a seasonal combination of weather conditions and exposures. Over time (many years), it can cause some surface deterioration.
2.) It has some benefits. When an engineer friend from a masonry group said, "It gives you clues to track down a basic problem with the structure". That was when we were looking (as a professional group) at exterior efflorescence on 4 story museum with a blue and white glazed brick exterior over concrete block. - It was in a full "bloom" when we were there. But at times, it was pristine and clean.
That indicated there was a lot of water in the exterior walls that was coming out. Nowhere in the interior of the museum was there any signs of moisture. It turned out the wall consisted of concrete block (partially grouted), no parging, but a black coating of some sort on the block and a small (3/8" maximum) gap to the brick to maintain a modular over-all wall thickness. Apparently, the weeps on the lower level of the wall could not handle the amount of water in the wall. Because of the pattern of the efflorescence, it became obvious there was water in the gap from a flashing problem on the roof, so the roofing and insulation had to be replaced. The brick was pressure washed and there were no more problems in the last 15 years or so.
I am not a fan or supporter of efflorescence, but it can be very helpful for diagnosis in some cases.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
there is deterioration, the concrete is eroding. you cant see it well in the photo, but the concrete surface is loose and crumbling
there is no backfill or soil against either side of the wall, it is a freestanding wall anchored to a concrete foundation. no soil anywhere
there is some minor freeze thaw, only occasional snow which does not last more than a day. the wall is not located on or near a road and to my knowledge, there is no salt used on the roads in that area
the block is easy to gouge in some of these areas.
there is no soil in contact with the wall anywhere. what you see on the ground is just loose gravel over a mass concrete foundation
OG, so you are suggesting that there are some sort of soluble salts in the concrete block which are expanding when they get wet? that is certainly possible, the only issue is the lack of a water source. the only water source is from rain which is seldom in this area. there is no soil contact at all with the wall. It is at least 20 feet above the maximum water table. and also above the 100-year flood elevation as well. there is a mortar cap on the wall which should keep rain water out. that significantly limits any water that could get into the block, unless there are cracks at the foundation level allowing water into ungrouted cells.
The "salts" in the concrete referred to do not swell or expand when wet. When the moisture, containing the salts, gets near to the surface, crystals form to cause expansion. - That is the same process for cast in place concrete. - Not that different from the pealing of paint with low permeability or multiple coats that just peel off because it has some tensile strength.
Some aggregates can cause problems because of their absorption and the ability to supply moisture. Some aggregates (like natural and manufactured lightweight aggregates) higher absorption but have a different structure and can absorb some of the forces from the external crystallization near there surface.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
