It should be that the water is not well mixed, or the mixing is uneven after adding water. The strength of caulking agent mainly depends on cement and rubber powder. At present, there is a surface magnetized caulking agent on the market, which has the same effect as the ceramic tile mirror after completion, but the cost is more expensive. The reason for your powder is that the proportion of water is wrong, or the mixing is uneven, or the worst effect is ha. See if the bricklayer added anything else, such as white cement. It won't appear as long as it's caulking agent, but you can't add anything else, because the proportion will be good when it leaves the factory. Adding other things will destroy the proportion, will produce powder, and inferior caulking agent will also exist.
Njmkt brand underwater joint sealant is good, and waterproof joint sealant is a patent developed by Nanjing Mankate, which is definitely their good. There are many also known as waterproof, but the actual use effect is different.