One technique that some fence builders will use is to dry set their posts. Essentially, they dump in sacks of dry ready mix and wet them in the post hole. They will tell you there is no difference in this method and wet mixing the concrete in a mixer or wheel barrow and pouring it in the hole.
Fast-setting concrete is ideal for setting posts because there's no mixing—you simply pour the dry concrete from the bag right into the hole, then add water.
Dry pouring a concrete slab is a method of concrete placement where the dry concrete mix is poured into a form or mold, and then water is added on-site to initiate hydration and curing.
How long does concrete take to set in a post hole? We would advise waiting at least four hours before any weight or pressure is applied to the posts or fence holes. For best results, you should wait at least 24 hours before you continue hole and fence construction.
However, this method really isn't ideal for most projects. You've probably heard the saying “good, fast, cheap – pick two”. Dry pour concrete is certainly fast and cheap, but it isn't that good – meaning it isn't all that durable. Wet pour concrete tends to have better strength and durability.
Initial Setting Times for Concrete
In standard industrial cases, full-strength concrete is recognized at 28 days. At seven days, you should have concrete that is cured to 70% full strength or greater. But to answer the question of, “How long does concrete take to set?” concrete setting time is generally 24 to 48 hours.
QUIKRETE® Fast- Setting Concrete sets in approximately 20 to 40 minutes. Heavy objects, such as basketball backboards, may be hung from the post in 4 hours. (If the temperature is below 72 degrees, additional time for curing will be required.)
So, a six-foot-high finished post ideally needs to be buried three feet into the ground. You may be able to get away with two feet depending on the weight of your fence, soil conditions and local climate.
This process can take several weeks or even months to reach full strength. In general, concrete foundations reach around 70% of their maximum strength after 7 days. However, to achieve enough strength to support heavy structures, it is often recommended to allow a concrete drying time of at least 21 days.
It is important to keep in mind that dry-pour concrete may not offer the same level of strength and durability as wet-mix concrete. Dry-pour concrete can also be more prone to cracking and shrinkage, which can lead to structural issues and the need for costly repairs over time.
Whether you are building a new fence, setting a mailbox or anchoring a basketball goal or play set, QUIKRETE® Fast-Setting Concrete is the ideal product for the job. With Fast-Setting Concrete there is no mixing or tools required – You simply pour the dry mix right from the bag into the hole, then add water.
Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
One technique that some fence builders will use is to dry set their posts. Essentially, they dump in sacks of dry ready mix and wet them in the post hole. They will tell you there is no difference in this method and wet mixing the concrete in a mixer or wheel barrow and pouring it in the hole.
Two 50-pound bags of fast-setting concrete will set a 4-inch-by-4-inch post in a hole that's 10 inches wide and 2 feet deep. Make sure the post is perfectly straight before allowing the concrete to set.
Fill with Gravel or Concrete
The choice is yours. Gravel helps keep moisture from the fence posts, slowing the rot. Concrete can more sturdily set the posts, but the moisture in the concrete may collect and absorb at the bottom of the post, accelerating the very process you're trying to mitigate.
Installing a fence post in dry cement is pretty simple. You want to pour about 5 inches of the dry cement into the hole around the fence post and tamp it down. Then repeat this process until the hole has been filled.
The depth of the post should be a minimum of ⅓ of the height of what's above ground. This means that if you want a 6-foot tall fence, you need at least 2 feet of the post to go below ground. If this was the case, you would need at least 2 bags of concrete per fence post, with each individual bag being a 50lb bag.
Dig post hole so diameter of the hole is 3 times the width of the post (i.e., the hole for a 4” wood post should be about 12 inches wide). The depth of the hole should be 1/3-1/2 the post height above ground (i.e., a 6-foot tall fence would require a hole depth of at least 2 feet).
Since Quikrete needs less time to become fully set up, it has stronger strength than traditional concrete. Quikrete has been engineered to be a stronger product with a higher compressive strength (ability to bear loads) and greater tensile strength (resistance to being pulled apart).
Using a post-hole digger, it will depend on how deep the holes are. For holes 2.5-feet deep, you will probably use about 2.25 to 2.5 60-pound bags of concrete per hole. If you use a shovel, figure 4 to 5 bags per hole.
Although fast-setting concrete dries within 20 minutes, don't put any weight or heavy loads on your post until the next day. That way, you can ensure that it stays plumb while it dries. Tip: If your post isn't level once the cement is dry, dig around the cement base and shift your post so it's level.
The consequences of not letting the concrete set properly
If you don't let it set properly, it will disturb the curing process. This will cause loss in strength and durability and may also lead to cracking.
To ensure proper curing, there are several key things to ensure optimal results. Spray: To maintain the proper moisture levels, concrete should be sprayed with water frequently. This is known as moist-curing. Most specialists recommend watering the slab 5 to 10 times per day for the first seven days.
If kept dry, portland cement will retain its quality indefinitely. However, bagged cement that's stored for long periods in a dry atmosphere can develop what's called warehouse pack, a mechanical compaction that makes the cement lumpy.