Had some shrinkage cracks occur on a garage slab. 50% of the cracks are hairlike and the other cracks are only about a fat 1/6th wide. Not too bad overall but I want to try and hide them as much as possible.

I read one article online that says for small cracks to just make a paste out of water and Portland cement and fill the cracks. Would this blend in well to hide the best? The cracks are so small it's got to be something without aggregate used to fill. What would you recommend?

 

If some are as wide as 3/16" (your description being 1/6"), you would do well to add fine mason's sand to the Portland cement slurry you plan to use. The sand will make for a more dimensionally stable product, less likely to re-crack if the cracks themselves are not quite dormant. No sand needed in the hairline cracks (0.003" wide, like a human hair).

If they were in my garage, I'd probably ignore them. But if I ever reached a point of wanting to do something serious, it would involve a visit to a local concrete supply retailer, where a gallon of 2-component, HMWM (high molecular weight methylmethacrylate) mixed and flooded into the cracks would do the trick, permanently. The stuff is wetter than water, and has the ability to yield slightly with small-movement cracks while bonding tightly to the sides.