Water-cured concrete made with Portland cement can harden even when it is completely submerged in water. In fact, one technique for curing a concrete slab is to build an earthen dam around the perimeter of the slab, flood it with water, and keep it covered for a week. Surprisingly, concrete can dry even better under water than in the air. This happens when the cement particles are hydrated and react chemically with the water, joining sand and gravel.
This curing process (hardening) takes almost a month and causes the concrete to set. The trick when pouring under water is to make sure that the concrete reaches its final position without “falling” through the water. Yes, you can pour concrete in the rain since curing is a chemical and not a physical reaction, so rainwater will not kill it. Considering that concrete can be cast and cured under water, a little rain on your property will normally not hurt a job.
The temperature and moisture content of concrete are two important aspects of curing and, depending on these two factors, concrete achieves its strength. This technique can also be used for vertical concrete columns and walls by wetting them and wrapping them with a curing blanket or plastic sheets. The segregation of the concrete mix under certain conditions results in a variable quality throughout the concrete mass. By paying special attention to the concrete mix during this period rather than moving away as soon as it is poured, you can increase the structural integrity of the concrete and make it more resistant to future cracks.
Your new concrete is designed to reach 90% of its full strength potential after 7 days, so feel free to drive your personal vehicle on it. Note that some concrete slabs can still crack because concrete shrinkage occurs during the use of hydration water and the temperature fluctuates. Often, a concrete covering of a building or house can be reused when other materials, such as wood, begin to deteriorate. When pouring a walkway or patio, a strong gravel base is required to keep the concrete from cracking and moving. On a larger square slab, such as a patio, you'll want to consider breaking concrete with joints that are perpendicular both down and across.
To ensure that the drying process goes smoothly and that the concrete reaches its final position without falling through the water, determine the maximum joint spacing (in feet) by multiplying the planned thickness of the concrete (in inches) by 2.5.In addition, concrete cured by this method is almost 50% stronger than concrete cured without moisture. This ratio should be set according to the moisture content of the surface because if the water-cement ratio exceeds desired limits, it will result in capillary pores in the cured concrete, resulting in poor strength and durability. When a concrete mix is too wet, it causes a greater amount of shrinkage during the drying process than is needed. As a result, concrete has a high probability of cracking and for such cracks they are likely to be quite good in size.