How to Properly Pour & Cure a Concrete Slab in McAllen

Site Preparation and Foundation Requirements

Site preparation and foundation requirements are an important part of installing a properly functioning concrete slab. Because McAllen is located in an area with clay-rich soils and because of the need for drainage in the area, there are many factors to consider in preparing the site. One of the most important is excavating 7 inches deeper than the 4-inch-thick slab being installed. A minimum of 3 inches of compacted gravel base needs to be put underneath the 4-inch-thick slab; this will allow for a good base for the concrete to rest on and to keep the slab stable over time.

The type of gravel used must also be considered. Crushed limestone, or all-purpose gravel, should be used and should be compacted in lifts until the gravel base is solid and even. It is also very important that the gravel base is kept from getting too wet, as this will cause the gravel to lose its ability to hold weight and could lead to unevenness and cracking of the slab over time.

Form Construction and Reinforcement

Form construction and placement of the rebar or other reinforcing material are also critical components of the concrete slab installation process. If the forms are not built correctly, the concrete slab will not have a level and square finish, and will also not have the correct dimensions. Straight 2×4 or 2×6 lumber should be used for the form boards, and the boards should be secured to the ground with wooden stakes and deck screws. The form boards should fit tightly together and should be built so that the top of the forms is 1.5 inches above the grade.

The type and amount of reinforcing material used will depend on how the slab will be used and what the local building codes specify. Standard residential slabs usually use either a welded wire mesh or a grid of rebar that has been embedded into the center of the slab. Depending on the use of the slab and the soil conditions in the area, additional reinforcing material may be needed to prevent cracking and ensure that the slab will perform structurally under a variety of loads.

Concrete Mixing and Temperature Requirements in McAllen

Because of the high temperature in McAllen, Texas, during the summer months, it is extremely important to pay attention to the temperature of the concrete while it is being mixed and poured. The ideal temperature range for concrete is between 50°F and 80°F. Temperatures above 80°F require special “hot weather” concreting techniques, and temperatures above 85°F require special consideration in order to pour concrete in a way that it will be workable and can be finished properly. During the summer months, it is best to pour the concrete during the cool morning hours when possible in order to keep the concrete cool enough to work with and to prolong the working time for finishing the concrete.

Standard concrete mix designs work well for most applications in the McAllen area; however, in the summer months, it may be beneficial to use retarders that slow down the initial set of the concrete due to the high temperatures. Even though high humidity does aid in the curing of the concrete by slowing down the rate of moisture loss from the concrete, it is still very important to actively manage the moisture content of the concrete for the first week after placement.

Work closely with your local supplier who is knowledgeable about the specific conditions in the McAllen area, and choose the right mix design for your specific application and seasonal needs.

Concrete Placement Techniques and Timing

Adequate planning and a sufficient number of people to do the placing and finishing of the concrete before the concrete setting will greatly contribute to the overall quality of the finished product. When placing the concrete, pour it in sections if necessary, working across the slab area consistently to maintain the desired thickness and to adequately consolidate the concrete. Screed boards should be at least as wide as the forms to get the concrete flat and to prevent high or low spots on the surface of the finished slab.

Due to the high temperature in the McAllen area, the working time for finishing the concrete is limited. Plan, prepare your tools, assign duties to your workers, and develop your sequence of operations before the concrete arrives on site. Unpredictable temperature fluctuations or sudden storms can make working conditions difficult; therefore, preparation and efficiency are crucial for quality results.

Finishing Processes and Surface Treatments

Finishing begins immediately after screeding and continues until the final surface preparation of the concrete. Bull floating brings the cream to the surface, closes any surface voids, and works consistently across the entire slab, but do not overwork any section of the slab. Allow the bleed water to evaporate before beginning to trowel the surface, as early finishing can trap excess moisture in the surface layer and reduce the quality of the final concrete.

Edging tools will create clean, round edges that will be resistant to chipping and provide a professional look. Control joints should be made within 24 hours of placement and should be placed every 8 to 12 feet, depending on the size of the slab. The depth of the joint should be about one-fourth the thickness of the slab to properly control the location of cracks.

Surface Texture and Final Preparation

The surface texture of the concrete affects both the aesthetic appeal of the concrete and the coefficient of friction (slip-resistance) of the surface. Options range from smooth troweled finishes to broomed textures, which provide better traction. Broom finishing is accomplished by lightly brushing a concrete broom across the surface of the concrete after the final troweling operation, and produces consistent texture patterns. The timing of applying the texture pattern will determine the final texture pattern; earlier texture patterns will result in coarse textures, and later texture patterns will result in finer textures.

Do not over-trowel the surface of the concrete, as doing so will bring too much paste to the surface of the concrete, resulting in a weak and dusty finish that will scale and wear easily. Light, multiple passes of the tool will result in a better finish than heavy pressure or repeated working of the same area.

Curing Methods for the McAllen Climate

In the McAllen area, it is very important to properly cure the freshly laid concrete to prevent plastic shrinkage cracking and to obtain the highest amount of strength from the concrete. Freshly laid concrete that has been properly cured for 7 days is about 50% stronger than uncured concrete, and makes curing a worthwhile investment for the longevity of the concrete. Start curing the concrete immediately after the finishing operation, as curing the concrete will begin the process of preventing plastic shrinkage cracking and will start the chemical reaction that will result in the strongest concrete possible.

There are two ways to properly cure concrete in the McAllen area: water curing, which is the most effective method for obtaining the highest strength possible from the concrete, and using membrane curing compounds.

Water curing uses a continuous flow of water to protect the concrete from the elements and to conserve moisture in the concrete. There are three methods of using water curing: misting continuously, covering with wet burlap, and ponding water on horizontal surfaces. Due to the high temperatures in the McAllen area, it is very important to inspect the water-curing system often to ensure that it remains moist, as dry burlap or plastic can absorb moisture from the concrete instead of keeping it in the concrete. Cure the concrete for a minimum of 7 days and for a maximum of 28 days to develop the greatest strength possible from the concrete.

Alternative Curing Techniques

If water curing is not possible, then alternative curing methods can be used. Membrane curing compounds are a popular choice among builders and engineers, as they are easy to apply, provide protection against moisture loss, and allow the chemical reactions to occur in the concrete. Apply membrane curing compounds to the freshly laid concrete immediately after the finishing operation and before the surface moisture has evaporated. Many membrane curing compounds provide both curing and sealing properties and can provide long-term protection to the concrete.

Another alternative curing method is using plastic sheeting to cover the concrete. Plastic sheeting is particularly useful in covering large areas of concrete and provides excellent protection from temperature extremes and rain during the curing period. Make sure the plastic sheeting is in direct contact with the concrete surface and that it is weighed down to prevent wind from blowing the sheeting away. Clear plastic sheeting allows for heat build-up in cooler weather to accelerate the curing process, and white plastic sheeting will reflect heat in warmer weather.

Temperature and Weather Management

Managing temperature and weather in the McAllen area is critical to the proper curing of the concrete. In the summer months, temperatures in the area average 97°F and can present challenges for builders and engineers. Hot weather can cause the concrete to set faster, increase the amount of water needed to achieve the right consistency, and increase the likelihood of plastic shrinkage cracking. To combat these effects, pour the concrete in the early morning, mist the concrete continuously during the placing operation, and begin curing the concrete immediately after finishing.

Wind speed can also contribute to the negative effects of hot weather by increasing the rate of moisture loss from the surface of the concrete. Using windbreaks or protective covers during the finishing and early curing phases can help to mitigate the effects of wind.

Seasonal Timing Considerations

Spring and Fall are generally the best seasons for performing concrete work in the McAllen area, as the temperatures are moderate and the humidity is relatively low, thereby minimizing weather-related issues. However, Summer projects must be carefully planned to avoid peak heat hours and potential afternoon thunderstorms that are common to the McAllen area. Winter projects, although less challenging than those experienced in Northern climates, must still account for temperature fluctuations and occasional cold snaps that can affect the curing process.

When scheduling a concrete pour, try to schedule it around the forecast and avoid any times when the forecast calls for heavy rain, extreme heat, or rapid temperature changes. Also, having backup plans and weather protection supplies available will help to ensure the success of your project, no matter what the weather does.

Quality Control and Inspection Points

Performing quality control and inspections on the concrete placement process will help to ensure that the finished product meets the specified standards. Check the slump of the concrete as it is being placed to verify that the concrete is workable and has the correct consistency without too much excess water. Verify that the reinforcement material was placed correctly in the slab before pouring the concrete and that the reinforcement material has adequate cover to prevent it from shifting during the placement of the concrete.

During the finishing phase, inspect the surface of the concrete for any issues that need to be addressed immediately, such as bleeding, segregation, or surface defects. Record the temperature of the concrete, the ambient conditions, and the timing of the significant process steps, so that the proper process steps are followed and that any deviation from the process can be identified and corrected.

Long-Term Performance Expectations

With proper installation and curing, a concrete slab in the McAllen area can last 30 to 50 years or more. To maximize the lifespan and appearance of the concrete, regular maintenance, such as sealing cracks, cleaning the surface of the concrete, and periodically resealing the concrete, should be performed. By knowing the proper installation and curing techniques, you will know what constitutes quality work and will be able to maximize the value of your concrete investment over the long term.

Monitoring the newly placed concrete for the first few weeks after placement for any signs of unusual cracking, settlement, or surface issues will help to identify any potential installation issues that may need to be corrected as soon as possible and will help to prevent minor issues from becoming major repair issues.

For McAllen area property owners planning to install concrete slabs, learning the proper installation and curing techniques will help to ensure a successful outcome and provide the best possible return on their investment. Whether you are going to perform the installation yourself or hire a contractor to perform the installation, knowing the proper techniques will help to ensure that you receive quality results that are suitable for your local climate and conditions. Once you are ready to move forward with your concrete slab installation project, McAllen Concrete Contractors is here to assist you with your installation needs and provide you with the expertise and techniques that we have developed over the years.