Quality Flat Work

WELCOME TO CHARGER'S WORLD OF QUALITY CONCRETE FLAT-WORK!

Everyone knows that concrete cracks, a lot of it settles, flakes, holds puddles and sometimes just plain looks ugly! So how can we at Charger consistently do attractive quality work? By knowing what to do, when to do it and then doing it right the first time.

BASE AND PLACEMENT PREPARATION

The finished job will last no longer than what is under it. The ground under concrete must be free of anything that will decay and cause settling. If roots or other debris are buried under it failure of the concrete is inevitable. Base soil should be clean, leveled and compacted for best results.

Forms, can’t just be set by eye. Using a laser to set the elevations of forms and grade pegs is the start. But concrete must be placed and troweled to those preset forms and pegs or puddling is inevitable. Also, if the base is not free of organic material and compacted properly the cracking and settling can become disastrous!

Elevations must be set to accommodate drainage. Control joints and expansion joints must be planned to avoid cracking.

PROPER CONCRETE MIX

Concrete is a mixture of portland cement, sand, aggregate perhaps admixtures and water. The proportions of cement, sand, aggregate and water are extremely important. Too little water makes the concrete hard to work and provide a smooth surface. Too much water will cause too much cement to float to the surface and will reduce strength and cause flaking. Too little water will reduce hydration and make the mix hard to work. As concrete sets up a chemical process called hydration begins, which involves shrinking. How can that be prevented for causing damage?

Everyone knows that concrete cracks as it cures. Wire mesh and rebar hold the cracked concrete together. But the right kind of fiber reinforcement holds it together while it cures and greatly reduces cracking. That's where strong, fiber reinforcement comes in, but the fibers must be denser than water or they'll float to the top of the slab. They must be homogeneously mixed with the concrete to be effective. Fibers that float to the surface will be of little value.

Fibers before mixing with concrete

Fibers disperse as mixing begins

Another matter of major importance is the mixing time of the concrete, especially if ready-mix trucks are backed up because of problems with equipment, such as a pump, or screed not operating properly. Once water has been added to the mix hydration occurs which is the process that turns a plastic material into a strong hard, solid mass. But if mixing is prolonged, the concrete will begin to lose strength, harden prematurely, and become less or totally unworkable. This is another area where the skill of the crew is more important than textbook knowledge

In extreme temperatures or humidity, admixtures may be necessary to control hardening or curing. Good concrete work is not just a studied science, but is also an experienced form of art.

PLACING, WORKING AND FINISHING FLAT CONCRETE

Concrete must be placed expeditiously once it is mixed thoroughly. It can be off loaded directly from a ready-mix truck, transported by a crane lifted bucket, pumped or moved by conveyor.

Usually, trucks should not back over the area to be placed. This creates ruts and damages the integrity of the base. Other methods are needed to transport concrete over relatively short distances to avoid this. These include wheelbarrows, power buggies and come-alongs or rakes. FOR LONGER DISTANCES CONCRETE PUMPS ARE USED.
A riding trowel can be used to provide a super flat slab.	A vibrating float prepares a slab for trowelling or brooming.

Using forms and grade pegs as guides, the concrete is then leveled to these guides with rakes, shovels and bull floats. Trowelling is critical. Too much work will bring too much cement to the surface, weakening the mix, and setting the stage for flaking after curing. Too little trowelling will leave exposed aggregate, which is also undesirable.

Expansion and shrinkage is provided for with control joints or saw cuts. If there is a lapse of time between the pouring of adjacent slabs, cold joints must be provided. The correct use and placement of such joints is both a science and an art. Experience can not be over emphasized.

Before the concrete hardens beyond the workability stage, any decorative process should be added. These include picture framing, brooming, dying or decorative stamping.

Charger Enterprises, with 25 years of experiences, not only has the knowledge of all aspects of concrete flat-work, but years of the learned skills and art enable us to provide Concrete Evidence that we give our customers more than they pay for!