The air and the ground have finally warmed up, and we are now firmly into concrete season.
The redi-mix trucks are rolling daily to various job locations, and our email inquiries are full of great questions from listeners anticipating a concrete placement.
“How important is the base under the pour?” is a common question.
Excavating existing soils, hauling them away, then replacing them with a crushed concrete or limestone base is a critical component of the placement. It also adds an “invisible” cost to the project.
Such costs are those you might not otherwise be aware of when viewing the finished product.
In many applications, we prefer the compacted stone base over less expensive sand, which may wash from beneath the placement and contribute to cracking and displacement. On heavy soils like clay, we specify a deeper base to provide ample drainage and load resistance over time.
“Should concrete be poured in hot, dry weather?”
We like the word placement over the word pour due to the implication of a very wet mix that can be poured in a form and, due to its highly liquid nature, will easily disperse and displace over the ground. This compares to a preferred stiff mix that requires strategic distribution through mechanical placement and manual labor.
Ideally, we will place concrete in cooler weather because heat speeds up cure and a slower cure is usually a better, stronger, placement. Concrete cures or hardens as the water used to evenly mix and distribute the ingredients leaves the placement. Heat is generated internally as the cure progresses.
We never want to install concrete on dry material, and we don’t want the mix exposed to hot, dry winds as it cures. In both scenarios, moisture may be drawn from the mix too rapidly to allow a proper cure, so a professional will protect the placement from rapid drying for the first 24 to 72 hours.
A stronger mix with more cement added is going to be a “hotter” mix and cure more rapidly.
“Why does the truck have to get so close and create ruts in my yard?”
The ruts can be easily repaired, but minimizing movement during placement is important to prevent segregation of the ingredients where the heavier stones might settle to the bottom and only paste is in the upper half. One of the things required to achieve the desired ultimate strength is equal distribution of the fine and coarse aggregate throughout the material.
“Is a troweled surface necessary, or can they simply broom finish?”
Once the mix is properly placed, screeded, and floated, a trowel is used to bring a fine paste of cement and water to the top while pushing down any rock or stone protruding from the surface. This creates a solid and strong cap on the surface and helps to seal it against chemicals, which may degrade or destroy it.
Once the placement has been properly troweled and the bleed water is gone, a light broom finish is acceptable to provide traction and increase slip resistance. Deep broom textures indicate the presence of surface water and no troweling and are often predictors of early surface failure.
“How important is it to have several workers involved?”
Having an adequate crew of trained personnel is critical. One way to save cost is to shorten the crew and simply add water to the mix to expedite placement and slow the cure. When complete, the pour may appear to be exactly what you hoped for, but core sampling would reveal a significantly weaker mix than what was specified and paid for.
“How important is reinforcing steel?” For driveways, patios, and sidewalks, the guys really advocate for the use of reinforcing wire mesh, usually six-inch, ten-gauge material placed in the center of the depth of the placement. This adds little to the cost but will minimize vertical and horizontal displacement of the slab over time.
Tensile strength can be gained from the additional and proper use of deformed, reinforcing steel bars. This increases the ability of the slab to flex and resist cracking.
For many reasons discussed in previous articles, concrete placements are not inexpensive.
The “invisible” costs add up but are critical to that driveway servicing your home for decades. Do not buy on price alone. Start by dealing with a contractor you can trust to do it right.
Professionals like those you can find every day at Insideoutsideguys.com.
Listen to the Inside Outside Guys every Saturday and Sunday on AM 760-WJR from 10 a.m.-noon or contact us at insideoutsideguys.com.
This article originally appeared on The Detroit News: The Inside Outside Guys give tips for a perfect concrete pour this season
Reporting by Ken Calverley and Chuck Breidenstein, The Inside Outside Guys / The Detroit News
USA TODAY Network via Reuters Connect
