Concrete Intro
Photo: A large foundation and retaining wall is poured in Milton, GA
Strengths
Concrete's strengths include its high compressive strength, which allows it to support heavy loads and resist forces such as compression and crushing. It also boasts durability, with resistance to weathering, machine and foot traffic making it suitable for a wide range of applications relevant to your home. It is a cost effective surface for exterior sidewalks, patios and driveways (when compared to stone, pavers, brick, etc.). The foundation of the home is almost always made of concrete mainly due to its strength, local trade familiarity and ability to be formed into precise shapes.
Rule of thumb for concrete curing times:
24-48 Hours: safe for foot traffic
7 Days: 75% strength
38 days: 100% strength
Weaknesses
Concrete's leading weaknesses is susceptibility to cracking, particularly when it is exposed to temperature fluctuations or when it dries too quickly. It has relatively low tensile strength, meaning it can be prone to breaking under stretching or bending forces unless reinforced with materials like steel (see next section). While small cracks are generally not a structural concern they pose an aesthetic concern when used in visible flatwork like patios, driveways, and sometimes people will even choose concrete as the finish floor material inside their home. Whenever specifying concrete as a visible finished surface inside or outside your home you must be ok with some level of cracking, it is inevitable.
Photo: a grid of rebar, along with thickened areas called grade beams make this garage slab stronger at our Governors Towne build in Acworth, GA.
Rebar - Mitigating Weaknesses
Rebar, or reinforcing bar, enhances concrete by providing additional tensile strength, which is crucial since concrete alone is strong in compression but weak in tension (pulling). The steel bars are embedded within the concrete before it sets, allowing them to work together to resist bending and stretching forces. This reinforcement helps prevent cracks, improves overall structural integrity, and increases the durability and load-carrying capacity of concrete elements.
Performance Standards
Compressive Strength after 28 Days: 3000 psi is generally the minimum you will see required
Cracking: some performance standards will list 1/4in - 3/8in as acceptable. In our experience with proper re-enforcement, and properly dug footings you can expect 1/8 or less cracks and they will be far and few in-between.
Color: color will change from one truck to another, but generally speaking using the same plant and pouring everything at once will limit this color variation to an unnoticeable level. With that said, you will generally not get a warranty for color matching, its just not in the cards for concrete. If you are using a concrete in a highly visible area where aesthetics are top priority, its best to spend more and go with a stone/tile topper.
Staining: concrete is very porous, expect staining during and after construction.