Pouring concrete at night became popular in the construction industry as it helps control the temperature and reduce the chances of evaporation during the curing process.
Before starting the concrete project at night, it’s important to consider all factors and strategies to ensure proper concrete pouring and ensure the concrete sets effectively. With careful planning and knowledge about the tips you can, you can achieve great results even in varying weather conditions.
What is Concrete and How does it Work?
Concrete is a composite or construction building material comprising three components, including cement, aggregates, and water. The cement, a binding agent and usually in powder form, is mixed with aggregates (usually gravel, sand, or crushed rocks) and water, which forms a paste that binds all the components together.
The purpose of water is for the hydration of the cement or the chemical reaction between the components that cause the concrete to form and harden. It also provides and controls the hardened properties of the concrete, including workability, permeability, durability, water tightness, and weathering.
The amount of water in the concrete mix provides ease of workability by providing enough lubrication between the aggregate/sand particles. If the concrete has too much water, its strength reduces because the particles are too far apart and it makes the concrete porous. Too little water makes the concrete ineffective. A balanced ratio of cement to water is important to make concrete workable and durable.
Concrete also goes through another process, which is called curing or maintaining adequate moisture and temperature in the concrete to achieve the properties, such as strength, wear resistance, water tightness, and durability. Properly curing the concrete also helps delay the concrete from shrinking to resist cracking.
It takes place after placing the concrete and finishing, and concrete, such as slabs, pavements, driveways, parking lots, small footings, and other structural concrete, requires a minimum curing period of about seven days above 40 degrees Fahrenheit.
Factors that Affect Concrete
There are so many different factors that can affect the concrete’s properties, especially its workability and strength. Some of the factors include:
The Quality of Materials
The quality of materials greatly affects the concreting process. The cement should be free of lumps and moisture. Also, never use contaminated, old, and already wet cement bags. Aggregates must be smooth, free of moisture, and must contain uniformly-sized particles. Water should be clean and not contaminated. It should be free of alkali, oil, salt, acid, or other impurities.
Having a balanced ratio for concrete mix is essential because it can affect the durability, workability, and strength of the concrete.
A good rule of thumb for concrete mix ratio is 1:2:3 or 1 cement: 2 aggregates: 3 gravel. Mix the ratio and don’t forget to add water.
The workability of the concrete will be reduced if the quantity of cement is lower compared to the water. If there is more cement than the water, drying shrinkage is more likely to occur.
The curing of concrete must be done right after stamping and finishing, and the best temperature for curing concrete is about 50° F to 850° F.
24 to 48 hours after the initial set of curing concrete, normal foot traffic is safe and people can already walk on this surface. The strength will increase 7 days after the initial placement or partial curing. The surface after one week will be safe and strong enough to handle vehicular and heavy machinery traffic.
Once it’s reached 28 days after the placement or curing, the concrete will have reached its full strength. The higher or longer the curing period, the stronger and more durable the concrete is.
Always remember that improper curing of concrete can lead to drying shrinkage and cracks, which will result in a decrease in durability.
The temperature during the placing of concrete can affect its curing period and strength. High temperatures when pouring the concrete can diminish the water in the concrete mixture because the water evaporates. Not enough water can cause cracking, flaking, and chipping because the concrete expands, which results in weaker and porous concrete.
So when temperatures are high, workers use cold or chilled water during the mixing process to control and maintain the temperature of the concrete, which will reduce the probability of damages like cracks.
During cold weather, the curing period of concrete will take much longer as it will not dry quickly. Freezing temperatures can also make the concrete freeze and shrink, resulting in crystals or ice formation.
The ideal temperature of pouring concrete is between 50 to 60°F because the water in temperatures below 40°F has a higher probability of freezing and slowing the process of curing, while temperatures above 60°F can make the water in the concrete evaporate.
Excessive moisture on concrete can affect the compaction or the process of releasing trapped air to increase the concrete’s density. Increased levels of moisture can also reduce the durability and strength of concrete. It can also cause microbial growth as it can trap pollen, salt, dust, or other microorganisms, which are food sources of mold and bacteria.
Concrete Pouring Tips at Night
Pouring concrete at night can help reduce the chances and effect of hydration caused by heat on the concrete. It will also reduce the evaporation of water on the concrete mixture as there are lower wind speeds and calmer wind conditions during the night. The ideal time to pour concrete at night is after sunset or after 8 p.m, to midnight or before 10 a.m, to avoid the hottest time of the day.
Maintaining the ideal temperature will provide a good curing process for concrete, so pouring concrete at night is recommended, especially in high-temperature areas.
Temperature can change even at night, so it’s important to always check for the temperature of the location, the subbase, and any surface in contact when pouring concrete at night. Make sure that the temperature will not go lower than 32° Fahrenheit.
Heating methods are also good options to do, especially if the temperature quickly changes during concrete pouring at night. You can cover the concrete using wet blankets, insulated blankets, and heated enclosures to help trap moisture and prevent the concrete from freezing. They will also help speed up the curing period process of concrete.
You can also preheat one or more components like sand or gravel when mixing the concrete. You can also use hot water for the concrete mixture but always remember the proper ratio. Don’t add too much water because the curing process of concrete will take longer, which can cause freezing.
Moreover, you can also use concrete admixtures or additives to cure the concrete faster at night. Also, wait for the bleed water to evaporate first before finishing.
Get the Best Result by Pouring Concrete at the Right Temperature
Concrete can be successfully placed, cured, and finished at night or during cold weather, but to achieve this, learning about the different factors that can affect concrete, proper placing, and tips must be observed.
By controlling these factors, the workability, durability, and strength of concrete will be controlled, which will result in long-lasting concrete. Use the following information and some tips mentioned above to ensure a successful and efficient concrete pouring at night.