It also contains shells and chalk combined with shale, clay, slate, slag, sand, and iron ore. Its a hydraulic substance, which means the chemicals in its mixture will harden once water is added. Both concrete and mortar have good strength and durability. That is why it's advisable to apply a scratch coat first for the two surfaces to bond easily. A higher amount of cement will create a stronger material. Wed love to hear from you. It gives you a better chance at creating a strong, level slab. Rather, its the main binding agent for making both concrete and mortar. Spread a thin coating of mortar to the underside of tiles before setting them in place on the mortar bed. bottle 1 gallon bottle Use For: If you dont want the concrete to stick, use a denser, smoother wood or a release agent. The addition of water activates the cement, which is the element responsible for binding the mix together to form a solid. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/5\/53\/Add-Concrete-to-Existing-Concrete-Step-1-Version-2.jpg\/v4-460px-Add-Concrete-to-Existing-Concrete-Step-1-Version-2.jpg","bigUrl":"\/images\/thumb\/5\/53\/Add-Concrete-to-Existing-Concrete-Step-1-Version-2.jpg\/aid1626169-v4-728px-Add-Concrete-to-Existing-Concrete-Step-1-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"