For the Tulsa commercial contractor, there are two common materials, and they are soil and concrete, and they represent some of the most crucial aspect of any project. The American Institute for Constructors or AIC describes concrete as follows:
“… Concrete is made of three key ingredients: aggregate, water, and hydraulic cement. Approximately three-fourths of the volume of concrete is made up by aggregate, with the remaining amount made up by a paste formed by the water and cement.
The most common type of hydraulic cement used in concrete construction is portland cement. Portland cement is made by grinding, mixing, and then heating materials containing lime, iron, silica, and alumina. The resulting mixture is then combined with small amounts of gypsum and crushed into a fine powder. A standard bag of portland cement in the United States contains 1 cu ft of cement and weighs 94 lb…”
The area that brings concrete and soil together for the Tulsa commercial contractor is aggregate, but below and in the mix design. The AIC defines aggregate as follows:
“…In construction, the term aggregate refers to the granular material, typically sand, gravel, and crushed stone, used in a variety of construction applications. Aggregate is commonly used in concrete, mortar, asphalt, plaster, drainage systems, erosion control, landscaping, as roof ballast, and as a base course for pavement and concrete slabs on grade.
Aggregate is classified by size and gradation using a series of sieves () and divided into two groups: fine aggregates and coarse aggregates. Numbered (No.) sieve sizes are based on the number of square openings per linear inch of sieve. For example, No. 30 sieve has 30 openings per linear inch, or 900 square openings per square inch. Fine aggregates include natural sands or crushed stone with all particles smaller than 3/8 in. and the majority of the particles passing through No. 4 (4.75 mm) sieve. Coarse aggregates include gravel or crushed stone with a majority of the particles retained on the No. 4 sieve and ranging up to 6 in. The American Society for Testing and Materials (ASTM) further defines fine and coarse aggregates and provides a variety of testing methods and technical specifications for aggregates…In concrete, the maximum size and gradation of aggregate that can be used vary depending on application. In general, the maximum size of aggregate should not exceed three-fourths of the clear space between reinforcing bars or one-third of the depth of slabs. Additionally, the gradation and percentages of fine aggregates and coarse aggregates within a concrete mixture should be considered. Excessive coarse aggregate can lead to separation or honeycombing, and excess fine aggregate can lead to concrete with a low density and high water content…”
When a Tulsa commercial contractor uses concrete the most import part to get right is the mix design, and structural engineers will be very specific about the mix design. The AIC has the following to say regarding the mix design of concrete:
“… Concrete cures (hardens) through a chemical reaction between the water and cement called hydration. The amount of water to cement in a concrete mix, or water/cement ratio, plays an important role in determining the strength and durability of the concrete. Too little or excessive water reduces the concrete’s strength and durability. The amount of water in a concrete mix is specified by its mix design. Although some mix designs allow for additional water to be added at the job site to increase a concrete’s fluidity, water should be added only if previously approved by the engineer and certain conditions have been met.
In addition to aggregate, water, and cement, other ingredients, called admixtures, are often added to alter the properties of concrete in various ways. A brief listing of some of the most common admixtures and their properties are listed below. For a more detailed listing of admixtures and their properties refer to Allen & Iano and Portland Cement Association in the list of references…The specific formula and selection of materials that make up a concrete mixture is called the concrete mix design. In addition to compressive strength, the concrete mix design includes specifications for the amount and types of aggregate, consistency, unit weight, air content, water content, cement content, and admixture to be used in the concrete mixture. To ensure that the placed concrete meets the desired properties specified in the mix design, several on-site and laboratory tests can be performed. Concrete field tests typically measure consistency, unit weight, air content, compressive strength, and temperature to ensure the quality of concrete…”
Not all the concrete that is used by the Tulsa commercial contractor is Cast-in-Place, there are also precast concrete pieces. The AIC defines Cast-in-Place concrete as follows:
“… Cast-in-place concrete is concrete that is placed in its fluid state and allowed to cure (harden) at its permanent location on the job site. Cast-in-place concrete may be mixed on site or delivered from an off-site mixing plant (ready mix). Ready-mix concrete is typically delivered by large specialty concrete trucks that slowly rotate the concrete mix to keep it from hardening during delivery.
Concrete should be placed as close as possible to its final resting location; avoid free fall and piling of the concrete. There are several types of specialty equipment used to place cast-in-place concrete, including chutes, belts, buckets, pumps, and buggies. If required, concrete should be moved from a high to low area by shovel. Vibrators should never be used to move concrete.
Cast-in-place concrete typically incorporates concrete reinforcement and may include structural and/or architectural embeds and elements. The placement, shape, and extent of cast-in-place concrete is controlled by formwork. Cast-in-place concrete is commonly used for foundations, structural walls, slabs, sidewalks, lightweight floors, and roof decking…”
Tulsa commercial contractors use precast concrete in a variety of areas including storm drains and underground utility piping. The AIC describes precast concrete as follows:
“… Precast concrete is concrete that has been cast prior to placement on the job site. The shape of precast concrete is determined by the mold or form in which the fluid concrete was cast. Similar to cast-in-place concrete, precast concrete commonly incorporates concrete reinforcement, architectural elements, and structural embeds. Precast concrete may be used for structural or nonstructural applications and cast on- or off-site. Most precast concrete is cast off-site at a precast manufacturing facility (precast plant). Precast plants are typically environmentally controlled and allow for the concrete process to be continually monitored. These factors, along with the ability to make identical pieces by use of reusable molds, can allow precast plants greater quality control and cost efficiencies over cast-in-place concrete. Plant cast precast concrete is typically delivered to the job site by truck and limited to the size and weight that can be delivered. Plant cast precast concrete is used in a wide variety of applications, including reinforced concrete pipe (RCP), manhole structures, equipment pads, vaults, septic tanks, piles, columns, beams, parking decks, load-bearing and veneer walls, planks, and lintels…”
Concrete is a versatile material in commercial construction and is indispensable for the Tulsa commercial contractor because it is a part of every project and usually represent the literal foundation of the project.