Concrete contractors play a crucial role when it comes to building concrete structures for home or commercial use. Their experience in the business helps them to understand the process in and out and finish the work on time.
They can also offer suggestions that elevate the project. Level Ground Excavation also stays openly communicative about timelines and overall costs.
Site Preparation
Site preparation is a critical phase that determines the success of any construction project. It involves several activities that are required before any building work begins, including clearing and leveling the land; grading the soil; laying pipes and conduits; and constructing foundations. These steps are necessary to ensure that the building will be constructed on a solid and stable base.
The type of site preparation that is required will vary depending on the nature of the construction project. For example, a small residential building will require less site preparation than a large commercial project. Additionally, the location of the site will also affect the site preparation requirements.
When the site preparation is completed correctly, it will make all other construction activities much easier. For instance, it will help contractors know where to dig and where not to dig, which will prevent any issues with underground pipes bursting during construction. It will also help them identify any obstacles that need to be removed or relocated before the construction process begins. This will save a lot of time, money, and effort in the long run.
During this phase, the contractor will need to survey the site and determine its topography and soil condition. They will also need to perform a soil test to find out what kind of foundation will be suitable for the site. They will also need to clear the land and prepare it for construction by removing any trees, rocks, or debris.
Once the land is prepared, it will be ready for concrete construction to begin. During this phase, the contractor will need a crane and other heavy equipment to move debris and dirt around the construction area. They will also need to install drainage systems, septic tanks, and piping.
During the site preparation stage, the contractor will need to mark out where the new building will be located on the site. They will also need to create access roads for construction vehicles and temporary storage areas. They will need to clear the area of any bushes, grass, and trees. They will also need to test the soil to find out its composition and classification. They will also need to locate any underground utilities and flag them before construction begins.
Concrete Mixing
The proportioning of the concrete mix is critical for achieving the desired workability and strength. To accomplish this, the contractor must use the proper ratio of cement to fine and coarse aggregates. The mix should also contain admixtures for workability and reinforcement durability. The contractor must also follow a proper batching process to ensure that the mix design is correctly batched and that it arrives at the job site by the approved submittals.
The mixer type is important, as well. Ideally, the mixing drum should be tilted to optimize the mixing time. It should not be so inclined that it is almost horizontal (inclination 0deg), since this will not allow the blades to impart adequate energy to the concrete during the knitting and mixing phase. It should remain at an inclination of 15 degrees for most of the mixing cycle. This enables the concrete to be pushed up into the mixer by the action of the blades and will enable it to drop into the drum during discharge, which is when the concrete is properly knitted and mixed.
If a mixer is not equipped with an inclination control, it should be provided with this feature. The inclination control should be calibrated to the specific mixer and will enable it to maintain an optimum inclination during the entire mixing cycle. This will increase mixing efficiency and the quality of the concrete produced.
For ready-mix concrete, the batching equipment must be properly calibrated and verified to comply with the approved mix designs. It must also be properly inspected to ensure that the ingredients are batched and dispensed by the mix designs.
It is also important to verify that the concrete is being tested for consistency and homogeneity. A good test for this is the coefficient of variation, which measures the standard deviation of the average, and a value of less than 0.75 indicates homogeneity. The contractor should always be prepared to provide the appropriate sample to the testing lab for analysis.
Make sure that the concrete contractors are submitting approved mix designs, and that any revisions in the original proportioning have been authorized by the engineer. Observe the addition of water to truck mixers to ensure that it is not withheld during mixing and that the water is incorporated into the concrete mixture as specified.
Formwork
Concrete contractors need to balance quality, cost, and safety in the construction of formwork. Formwork molds concrete to the desired shape and supports it until it becomes self-supporting, but it also constitutes a significant portion of a construction budget. Effective formwork must accurately create the structure to architect-engineering specifications while minimizing defects like sagging, bulging, or unevenness of concrete surfaces. It must also be capable of withstanding the pressure of poured concrete and construction live loads such as materials, equipment, and workers.
Formwork can be made of a wide range of materials including timber, plywood, steel, and plastic. It can be assembled on-site from a kit of panels, ties, wedges, and clamps or prefabricated and shipped to the job site ready for assembly. Collaboration between the contractor and project engineer often determines formwork configuration. For example, the design team might specify that a concrete slab should be poured in one direction. If this is the case, the concrete contractor must ensure that formwork is erected to provide sufficient clearance for pouring in this direction.
The concrete is still in a liquid state when it is poured, so the construction site needs to provide support and a temporary casing until it gains strength. For this reason, it’s important to know how to measure the slump of a batch of concrete. The slump is a rough measurement of how much water is in the mix, and a contractor can use a simple device to gauge it by scooping a sample of concrete into a cone-shaped container.
A proper mix is essential for the durability of concrete. To prevent a slump, contractors should monitor the concrete temperature, ensure that the mixing drum is kept clean, and add water as necessary. In addition, contractors should make sure that formwork is positioned correctly and that it’s well supported on all sides.
Formwork failures are responsible for more than 25 percent of all construction accidents and collapses. They occur for a variety of reasons, including overfilling with concrete, inadequate bracing, insufficient shoring, or insufficient strength of the concrete before removal of formwork.
Pouring
Concrete is a manmade composite material that consists of a structural binder (typically cement paste or asphalt) and a dispersed phase or “filler” of granulated aggregate. The size of the granules and their distribution within the matrix determines the strength, density, chemical resistance, and other properties. Concrete is a common building material that is poured in place for sidewalks, patios, driveways, and other structures.
During pouring, the contractor ensures the proper concrete mix is used, which includes proper water content. The contractor may also add admixtures for specific workability or durability properties. The mix is then transferred to the project site where it will become a permanent structure. Depending on the volume and distance involved, the concrete may be transported by truck, poured free under gravity or through a device such as a tremie pipe, or pumped through a pipe.
The site is prepped by clearing away any vegetation, rocks, and other debris that could interfere with the concrete placement. A gravel base of 4-6 inches is recommended for drainage. This can be tamped down by hand or with a plate compactor. The area is a tent with tarps to prevent rain from mixing with the concrete.
A concrete pour requires all hands on deck for safety and efficiency. To avoid a cold joint, the next layer of concrete must be poured before the previous one begins setting. To avoid this, the pouring pattern is planned ahead of time and sequenced correctly.
It is also critical to pay attention to the initial and final setting times. For a slab, the initial set typically lasts about 45-60 minutes. For large pours, the set time can be extended by using admixtures.
Once the concrete is poured, it must be kept moist during curing. This process hydrates the concrete, which results in increased strength and durability. Without proper curing, the concrete will weaken and deteriorate over time. It is recommended that concrete is cured for a minimum of four weeks to achieve maximum strength. Regular cleaning and sealing are also advised to minimize the risk of staining.
