We strongly recommend that you do not use any cement that has exceeded its use by date. The use by date on cement is related to health and safety regulations about ‘chromium VI’ which can cause allergic dermatitis. After the use by date on the bag we are unable to guarantee that ‘chromium VI’ is below the required legal limit, which could increase the risk of skin irritation. See the material safety data sheet for the product you have purchased for more details.