Maintaining Tools 2

[Dave_yosei]

Hi, I'm a new engineer who works with your standard set of fresh concrete tests (slump cone, cylinders, sometimes air). I have a kit (tampers, trowel, scoop, bucket) I carry around when driving to job sites and wanted to know if anybody has any tips for best practices to maintain them. I know it's impossible to have pristine tools, but I wanna make sure they last. Obviously cleaning and drying them after working with any cements can go a long way. Does anybody have any experiences with degreasers or acid-based tool cleaners? I'm worried about corrosion with the latter in particular.

 

[TigerGuy]

Your best option is to keep them clean. Wet them before each use, and clean them with water and a sponge, brush, etc. after every test. The scoop is especially sensitive, because it is easy for build-up to accumulate in the back of the bowl, near the handle. Also watch for areas where concrete can easily accumulate (inside the slump cone handles).

You will find yourself in situations where there does not seem to be sufficient time to clean the equipment between tests, do your very best. Fast setting concrete is another challenge, where the concrete seems to harden before you can complete your tests and start cleaning the equipment.

When I finish my slump test, I immediately clean the slump cone and base plate. When the air test is completed, the top section of the air pot is immediately cleaned. Then I dump the base, and submerge it in water and clean it after test cylinders or beams are molded. Unless you are working with fast-setting concrete, the scoop, strike off bar or trowel, and tamping rod can be left in water until you have placed your samples in initial curing.

Dilute hydrochloric acid can be used to partially dissolve the dried concrete, but this can cause corrosion. There are products available on the market that supposedly clean the equipment without corroding it. I've never trusted them enough to try any of their products. Usually, the best approach is patiently chipping the hardened concrete away.

 

[Dave_yosei]

Thanks TigerGuy! I remember the undergrab lab I worked in always had tools with concrete caked on in those exact spots... I'm definitely trying to avoid that. I'm also thinking of getting a roll of shop towels or old rags to carry around myself as I don't always have a clean cloth to wipe things down with after washing.

 

[3DDave]

Would a light spray of cooking oil just before use cause a problem?

 

[TigerGuy]

I've always understood that we are not permitted to oil the tools before use. That may have changed, I haven't made a set of cylinders in over 3.5 years.

A wire wheel can also be used to clean hardened concrete from the equipment.

 

[Dave_yosei]

I've used spray oil in the lab to allow for easier demolding of formwork and cylinder molds when reusing, but never on tools. I don't think ACI or any body calls out against the use of oil in spec, but it's probably a bad idea as it can get in the middle of the sample and cause weak spots e.g., air voids.

 

[TigerGuy]

Agreed, I've used gallons of WD-40 over the years on all kinds of soil testing and concrete beam and cube molds. I've always just made sure the tooling was wet before testing in the field (and yes, I've had many contractors whine that there was too much water on the slump base that caused their slump to be over limit by 3 inches).