Tips for Building Concrete Sidewalks
RS Means Engineering Staff , RSMeans
 |
Seed Newsvine |
Concrete is the most logical choice of material for sidewalks, driveways, patios, steps, garage floors, basement floors, slabs-on-grade, and commercial and industrial floors, not to mention walls, columns and beams — whether cast-in-place or precast.
Concrete used in flat work provides a surface that is durable and easy to maintain, and that can be attractive with the various finishing techniques available. Care must be given to construction methods even with the smallest of concrete projects. The following tips will help ensure the construction of quality trouble-free sidewalks.
During preparation, all organic materials such as trees, shrubs, plants, grass and their root systems must be removed from the sidewalk area. Any topsoil must be removed along with any rocks, boulders and other debris. It is preferable, and sometimes specified that the area be over-excavated and that suitable fill material be brought in, spread, and compacted properly to grade.
When setting formwork, it is recommended that they be placed to provide future surface water runoff. A typical slope is ¼" per foot, or a 1" slope across a typical 4' wide sidewalk. When the formwork is finally set to grade, staked and braced, the thickness of the sidewalk slab should be checked once more and adjustments made to grade of the base material.
Steel reinforcement, whether rebar or welded wire mesh, should be furnished and installed according to plans, specifications and applicable codes. An alternative to steel reinforcement in sidewalks is synthetic fibers contained in the ready-mix concrete.
Ready-mix concrete should be ordered with an air-entrainment additive that will provide between 5% to 8% total air content. This is very important for concrete flat work that will be exposed to freeze-thaw cycles and de-icing chemicals. When the concrete truck arrives, do not add water to increase the slump to make it easier to move the wet concrete around. A slump of 5" is recommended for hand-placed flat work.
When placing the ready-mix concrete, strike off the surface with a straightedge while keeping a small amount of concrete ahead of the screed to fill in the low spots. The concrete should then be consolidated with a vibrator to allow the concrete to flow into all the corners of the formwork, to eliminate air voids, and to allow the concrete to flow around the reinforcing steel.
The surface of the wet concrete should be floated with a bull float before the bleed water comes up to the surface. Wait for the bleed water to evaporate before doing any finish floating or final finishing. Use a jointing tool to make contraction/control joints at regular intervals along the sidewalk to a depth of ¼ the slab thickness. An alternative to making joints this way is to sawcut the joints within 12 to 24 hours. Be cautioned that ready-mix concrete for sidewalks, that contain entrained air, should never be steel troweled, rather it should be floated with a wood float and given a broom finish or a stamped finish.
Curing must begin as soon as the finishing is completed. This can be accomplished with wet curing methods such as burlap and sprinklers or a burlap/poly blanket, or with a sprayed on curing membrane.
When estimating the cost of installing concrete sidewalks, these seven elements must be considered separately: preparation, formwork, reinforcing, ready-mix concrete, placing, finishing and curing.
Member Comments
For northern climates try pervious concrete sidewalks. They do not develop ice as easily and do not pond.
