The cement acts as a glue to hold the gravel and sand together. When the water and cement are mixed together, crystals form tiny interlocking needles that connect everything together. The strength of the hardened concrete will vary and will depend on the relative amounts of cement, sand and gravel used.
Your local building code should specify the minimum strength of the concrete used for the driveway and sidewalks. Check the contractor’s quote to ensure the correct concrete strength mix is specified.
Although it can cost more for a large workgroup, sufficient manpower is essential for permanent concrete work. If a contractor with too few workers cuts back on money to save money, the concrete can build up before it can be installed and leveled.
In order to allow more working time with fewer workers, the contractor may need to put a little more water on the surface to allow more time for a smooth surface. Adding extra water can drastically reduce the strength of the concrete surface. This can cause problems with your existing driveway.
The contractor should specify wire mesh and 1/2-inch rebar (steel rebar) in the concrete. This reinforcement minimizes the number of deep cracks in the concrete. As concrete shrinks as it hardens, crack control grooves should be made so that small cracks only form in these grooves.