Concrete blocks 5

[salalahmaroon]

Hi guys.

Can somebody please help me in identifying the exact technical term for crumbling of concrete block surface as seen in the attached.

Thank you.

 

[racookpe1978]

Those are clean blocks (never used) and are still stacked on pallets.

I'd call it "corners damaged during shipment by impact" and bad forklift operators.

 

[LittleInch]

Some (bottom block) look like poor compaction and vibration, not to mention poor mix control and air entrainment. Some of those blocks don't look great to me.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[dhengr]

Salalahmaroon:
Those are just plain crappy conc. blks, looking mealy in texture and strength, they are crumbling, and will have very low strength. Did they use salt water to mix the conc? Get the mix design and internal testing and QC reports from the supplier. You should have an experienced testing lab test of representative sample of those blocks. They will be able to comment on the original conc. mix, the manufacture of the blocks, material make-up and mech. properties, etc.

 

[concretemasonry]

Those look like typical coarse texture solid block (possibly "lightweight" according to ASTM C90 specs) but could be normal weight if a coarse "hard slag" is used for some reason.

Little inch- Concrete block are never made with any air entrainment. They were made with a mix that was to dry, so the molds were not able to be filled to provide uniform compaction..

dhenry - Not likely he will be able to get a "mix design" by weight since very often batching is by volume. They were probably made in a plant and stacked by hand on a pallet when they a a day or so old by hand, so corners of the "green concrete" tend to get chipped off on weak planes.

The block would most likely by used and covered with plaster or similar materials as finished coat. They block are usually laid with a relatively jpoint, filling the cracks an irregularities to make surface coating easier. The coarse texture is often preferred for compatibility with surface coatings.

When tested, they may very well meet the specifications for use since the ASTM standards and similar standards have numerous specification levels for acceptance.

I have seen worse in my 40+ years of seeing concrete masonry uses and usually the demands set the requirements of the products since the equipment can do wonders with poor aggregates and meet specific standards.

Dick





Engineer and international traveler interested in construction techniques, problems and proper design.

 

[salalahmaroon]

Thanks guys for the inputs.

Sir Dick,
You are definitely correct, they will be used to be covered with plaster. The problem is blocks in the lower layers in the palette seems to have these "slight crumbling" characteristics but we can say the upper part is satisfactory. I'd also go for dhengr's post to check manufacturer's side and have samples tested. Your thoughts?

You've seen worse as you have said, do you suggest these are acceptable?

Can you please advice as to what standard can we refer to in order to further reinforce specification criteria on acceptance for this particular characteristic. Oh and by the way sir Dick, can I call it non-durable block surface? Thanks

 

[hokie66]

My "exact technical term" for those blocks would be "homemade, low strength rubbish".

 

[dhengr]

Hokie:
Now that Dick (concretemasonry) mentions it, and the OP’er. seems to confirm it, I’ve seen those kinds of blocks before. I think the OP’er. kinda mislead me/us, when he called the block in the photo concrete block. I assumed they were a real bad example of what we know as real structural concrete block, because I’ve seen some of those too. And, that they were some sort of half height solid blocks. Instead, they are actually a mass masonry wall block made out of something akin to lean concrete, with various aggregates. They are only intended to act in compression, at a fairly low stress, in a multi-wythe pile-up to make a bearing wall. They may be mortared, maybe bonded together at different heights, etc. But, they are just thick, stacked, mass masonry for a wall, a fairly common building method in many developing countries. Then they are covered with a weather resistant plaster, our some such, as outer skins and finishes on the wall. A few generations ago they may have been hand packed mud/clay bricks, sun dried, and then covered with a clay skin coat finish, adobe, or some such?

 

[salalahmaroon]

Sorry to have misled you dhengr but it is called concrete block in this part of the world. Please enlighten me for the term used in your area. This might be a new insight. Thanks in advance.

Now that a much clearer picture is painted. It is still right to go and check supplier's side for QC aspect? I suspect something's wrong since the half part of that palette manifests this "characteristic".