Adding detergent to concrete mix?

My father (sadly departed) used to add a dash of washing up liquid (detergent) to his concrete when mixing, and I never asked him why. I presume that is must have improved the 'workability' of the mix, or perhaps how easily it mixed. Does anyone else do this? What is the definitive reason? Would a small amount of detergent alter the final strength of the concrete under compression or flex? He was pretty smart, but I don't think he would have come up with the idea himself (although he was a chemistry teacher....).


mikeasaurus1 month ago

Your father was a smart man! Historically detergent was added to concrete as an air-entrapment additive, which would keep small bubbles inside the concrete and allow small areas where the concrete could flex without cracking. Modern concrete takes this into account and adding detergent isn't required.

Great question!