Upon your site experience, What is the best time on the day for site concrete casting?
In hot weather countries; in summer it is preferable to pour concrete at sunset and it is wrong to pour concrete at dawn or early morning; this procedure is not a substitute for the precautions for casting concrete in hot weather
In the winter, it is preferred to pour at dawn or early morning
the best time is 7:00 AM at any season which the temperature is 23±2°C
Performance of concrete in all perspectives are best at room temperatures, including mixing of materials, placing and casting of concrete.
Both cold weather and hot weather concrete has detrimental effect. Concreting can be done with proper under standing and precautions.
Hot weather concrete, mainly experience rapid plastic shrinkage which leads to formation of shrinkage cracks and additional tensile stresses. Further, the raw materials especially aggreagtes are also hot ........... loss in workablity is often seen in hot weather.
Where as cold weather concrete, suffers slow hydration .......... and in case of severely cold conditions icing of water is also an issue.
I am considering the exothermic heat in hydration reactions between the Center and periphery. Which means that the width of the concrete is an important parameter to decide the casting time. and for different design width there would be some different best casting time. This are some ideas which I thought before and I haven't confirm that.
You can cast the concrete after taking precausions for hot weather or cold weather.
It Depends on area, but most of the time, may be after sunset upto mid night.
You have in the litterature a large corpus of informations on when to cast concrete and the precautions to take depending on the weather ,the quantity of concrete to be cast ,the type of infrastructure,etc.
Setting produces heat that tends to evaporate not only mixing water but also water needed for this process. Pouring concrete before ambient temperature is soon to rise quickly is not advisable. If unavoidable, then special care shoukl be taken, such as cooling water et al, and curing should begin as soon as possible after pouring.
The question shouldn't focus on the time but should be the ambient temperature. You can refer to ACI Technical Reports for "Hot Weather Concreting", which is a very good reference to find the answer for your question.
Normally concrete can be placed upto 38 deg c ambient conditions. if it exceeds the hot weather precautions needd to be taken. But when the temperature is more then 40 deg c it is advisible to stop concreting as the workability loss will be too high due to evoporation of water from concrete and the laid concrete also will develop shrinkage cracks. During summer the pours can start after 5 pm and continue in night till morinig or can start morning 6am and till 12noon. It is all depend on ambient conditions the call need to be taken and whether it is hot or cold the concrete need to be protected against adverse weather to avoid deterioration.
concrete can be casted at anytime during the day. however, rate of hydration can be very much affected by weather conditions since it can altar initial and final setting time. in hot weather conditions plastic shrinkage may occur due to evaporation of moisture from the concrete also in extreme cold conditions shrinkage can also occur. despite all these considerations per the condition in which you find yourself you will surely know what to do. but to answer your question, preferably it is will be ideal to cast during room temperatures ( in the mornings and evenings).
According to me the best time on the day for site concrete casting is the morning; I mean early in the morning.
Check the ASTM C403 and apply the results to determine the best time for concrete casting on site according to the environmental conditions
Answer to this question is not that simple. Concrete is not suitable for placing at extreme temperature conditions such as > 40 C or < 5 C. If concrete is to be cast against adjacent concrete, we also need to consider the temperature differential between fresh concrete and the adjacent concrete. In countries with very high temperature during summer time, people tend to start concreting some time after noon (e.g. 4pm) when the peak ambient temperature passes and the surface temperature concrete of adjacent concrete against which fresh concrete is cast. In cities with stringent environmental regulations restricting noise pollution, we need to consider the time taken to complete the pour before when the noise permit ceases.
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