Vietnam is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, Thailand across the Gulf of Thailand to the southwest, and the Philippines, Malaysia and Indonesia across the South China Sea to the east and southeast.[d] Its capital city has been Hanoi since the reunification of North and South Vietnam in 1976, with Ho ...
Cement. 1  Cement is a binder. Similar to flour in a recipe, the purpose of cement is to hold the other materials together. 2  Concrete is a composite of aggregate (such as sand or gravel), cement, and water. Itâs like a cookie. 3  The basic composition of mortar might seem similar to concrete, but what really sets it apart is how it is used.
Concrete is an artificial conglomerate stone made essentially of Portland cement, water, and aggregates. When first mixed the water and cement constitute a paste which surrounds all the individual pieces of aggregate to make a plastic mixture. chemical reaction called hydration takes place between the water and cement, and concrete normally changes from a plastic to a solid state in about 2 hours. Thereafter the concrete continues to gain strength as it cures.