Mr. Mohammad,

In my limited experience, successful pouring is dependent on many factors. Putting them all together is at times an art, is always made more reliable by experience, and is definitely not for beginners.

As others have said, ACI 318 is a good beginning point. In addition, the Portland Cement association in the USA has a very good book on the topic of design and placement of portland cement mixes, available (often for free) from the various ready mix concrete companies.

Segregation is a real problem--as the mix drops and splatters off the reinforcement it will separate with the fines hanging up while the aggregate drops down. Therefore there can be sections with holes because the mix is no longer a mix.

The amount of water is critical--the common practice of adding more to increase flowability drastically reduces the strength of the final mix. Instead of adding water, you must add "water reducers" also called "plasticizers" or "super plasticizers". These increase the floawability without reducing the strength. They come with trade-offs that you must beware of. One is that their time of effectiveness is limited, such as for a half hour after they are added.

Another factor is the height of each "lift"--how high you can pour in any one area at a single time. Because of pressure exerted by the concrete on the form sides, freshly poured concrete can very easily cause the ties to break and the forms to separate or "blow out". When this happens you have a major problem! Therefore, many companies' specifications call for lifts not over 2 or 3 feet. However, you then have to ensure that when you return to pour a new lift, the top of the previous one is still plastic enough that the new lift will seal with the old one. The time lapse allows the previous lift to take an initial set so the added concrete on top does not greatly add to the pressure on the form sides below.

Vibration has been mentioned. You can do too much and too little. Also, internal versus external vibration needs to be considered. Whatever you do, the intent is to ensure that any air pockets work out to the top of the pour.

Some (patented) mixes, often called architectural mixes, have amazing flowability without the problem of segregation. They come with higher cost and bring their own difficulties in pouring (such as greater pressure on the forms), but at the advantage of total elimination of vibration.

Like I said at the beginning, you need on-the-job experience in addition to book knowledge. You will probably make many mistakes and have a number of near misses, in addition to many successes. Ask questions, and do not discard the advice from others, including the truck operators, etc.

--John M.