My next door neighbour got in a builder to extend his house. During the early stages of the demolition, I naturally moved my S2000 out of the way of harm, but harm has struck anyway.
The builder took out some floor with a concrete saw, making a cloud of dust naturally.
Since the car was due a really good wash, and the car was well polished with autoglym, I did not mind the dust. BIG MISTAKE.

The dust from the saw has stuck hard to the car all over the paintwork and the glass; it won

 

Hmmm, I wonder if claying the finish will get those particles out? You might try it on a very small area and see what happens.

 

I know using a clay bar takes off paint overspray.. I'm pretty sure if you can take it off with your fingernails, the clay bar will work. Try it...

 

Oh, and if you use the clay bar, make sure you wax up your car real good.

 

Clay bar with recommended lubricant is the answer.

 

I would not use clay bar or do anything until I spoke with your neighbor. The contractor should have insurance. You should definitely document the car's condition before you take any remedial steps! Get the contractor's name and address from your neighbor, write him a letter, take pictures, take the car to a PREMIUM body/paint shop for advice before you do anything else.

Just my 2 emphatic cents

 

DO NOT USE THE CLAY BAR!!!!!!!! Did I say that loud enough? The bar will pick up the particles and grind them back into the paint, if you want that...then go ahead and use it. The concrete dust will come off little by little over time and washings, don't be in such a hurry. If your car wasn't dirty at the time you actually did yourself a disservice, NO wax made is as good as dirt in this situation. The concrete dust would have adhered to the dirt and not the wax or paint. Don't sweat it, it'll be OK, give it time. Oh yeah, don't hand wash it, take it to the carwash for the next 10 washings and keep the nozzle at least 12" away from the car. And yes, for all you fellas that just freaked, I did say car wash (NEVER use the automatic car wash), and yes, I was a professional detailer for 6 years.

Andrew

 

I can't comment on using clay to remove the cement, but a clay bar works wonders on other things such as sap.

 

One thing you might consider is washing the car with a mixture of vinegar and Dawn dishwashing soap and water. I don't know the ratio, but my father used to work at a cement company and he said the only thing that would take off the cement dust was Vinegar with water and soap. You might want to first try a fairly dillute solution and add more vinegar if it doesn't work for you.

Now I warn you...do not leave the vinegar on the car or work in direct sunlight. Rinse thoroughly and immediately after you wash an area if you try this. I can't say that I have done this to my car. I used a little vinegar and water to get off the spots of cement dust when I drove through some road work and it did no damage, but I've heard others warn that vinegar is an acid and if you use it in the sun or leave it on the car it will etch the paint. But this is the exact reason it disolves the cement dust.

Also, be prepared to wax your car thoroughly after washing with Dawn as it will definitely strip the wax off. And this is only one way of removing cement dust...there may be others.

Byron

 

bguernsey's solution seems reasonable, since the cement dust is an alkali and vinegar is acidic. Just make sure you rinse thoroughly with plenty of clean water. I'd try the vinegar solution on a small area at first to check it's effect.