Placing Concrete in Hot Weather Caution needs to be applied when placing concrete in hot weather what are they?
The success of many hot-weather concreting operations depends on the steps taken to slow the cement hydration reactions within the concrete and to minimize the rate of evaporation of moisture from the freshly mixed concrete.
There are many precautions in hot weather concreting such as:
*The concrete can be scheduled to a time when the temperature is not high e.g. in summer it can be scheduled tonight or early morning
*use material and mix design proportion having good weather resistance e.g. select sand having low specific heat.
* The concrete can be done in a covered environment.
*Chilling: The chilling of aggregate can be done by watering or keeping them covered, use cold water or ice for mixing operation
* Employ efficient workforce and machinery to improve the handling.
*Use of low heat cement, Use chemicals to slow the cement hydration reactions.
* Make curing as soon as possible.
The success of many hot-weather concreting operations depends on the steps taken to slow the cement hydration reactions within the concrete and to minimize the rate of evaporation of moisture from the freshly mixed concrete.
There are many precautions in hot weather concreting such as:
*The concrete can be scheduled to a time when the temperature is not high e.g. in summer it can be scheduled tonight or early morning
*use material and mix design proportion having good weather resistance e.g. select sand having low specific heat.
* The concrete can be done in a covered environment.
*Chilling: The chilling of aggregate can be done by watering or keeping them covered, use cold water or ice for mixing operation
* Employ efficient workforce and machinery to improve the handling.
*Use of low heat cement, Use chemicals to slow the cement hydration reactions.
* Make curing as soon as possible.
Dear Salam Alobaidi
*preferable to work in closed environment (if possible thermally insulated)than open environment where the temperature will be high
* use materials having high thermal resistance
* curing should start as soon as possible
Dear Salam Alobaidi
-preferable to work in closed environment (if possible thermally insulated)than open environment where the temperature will be high
- use materials having high thermal resistance
- curing should start as soon as possible
Dear Salam Alobaidi
1)preferable to work in closed environment (if possible thermally insulated)than open environment where the temperature will be high
2)use materials having high thermal resistance
3) curing should start as soon as possible
Dear Salam Alobaidi
1 preferable to work in closed environment (if possible thermally insulated)than open environment where the temperature will be high
2 use materials having high thermal resistance
3 curing should start as soon as possible
dear Velusamy,
pouring the slab or foundation can not be in closed environment
dear
if that is so, which is not mentioned in your question. any way closed environment may not be possible for your case. thank FYI.
1. Concreting can be done in the evening to avoid higher temperature.
2. Cold water can also be used for the purpose of mixing.
One can sprinkle water on aggregate in order to keep the ambient temperature of aggregates low if they are stored in open
2.One must avoid the loss of moisture from concrete by covering the concrete with Polythene sheets along with resorting to early curing
Curing is always misunderstood by many. The purpose of curing is to maintain high RH in concrete i.e. above 85% and prevent the temperature gradient beyond 15 degree Celsius to avoid internal cracking as the tensile stress may develop if the temperature gradient is more than 15 C. Therefore very high precautions are necessary in curing in hot weather concreting.
Prof. Edward Abdun Nur of US used to say "if you can not cure your concrete keep it warm" means do not do improper curing.
What is Hot Weather for Concreting?
Definition of hot weather condition, as stated in the ACI-305R-10, refers to job-site conditions that accelerate the rate of moisture loss or rate of cement hydration of freshly mixed concrete, including: a) Ambient temperature of 27 °C (80°F) or higher; and b) Evaporation rate that exceeds 1 kg/m2/h Canadian Concrete Design code (CSA A23.1/.2) uses the same ambient temperature for hot weather (27 °C).
This might have caused due to combination of any of the following:
- High ambient temperature
- High concrete temperature
- Low relative humidity
- Wind speed
- Solar radiation
What are the Challenges of Hot Weather Concreting?
How does hot temperature affect concrete? We know that water is a main component in concrete. Increase in the weather temperature increases the rate of vaporization, therefore, hot weather condition increases the water demand in concrete production. Other challenges of hot weather concreting can be summarized as:
1- Accelerated slump loss leading to the addition of water on the job-site, 2- Increased rate of Setting resulting in placing and finishing difficulties, 3- Increased tendency for thermal and plastic cracking, 4- Critical need for prompt early curing, 5- Difficulties in controlling entrained air, 6- Increased concrete temperature resulting in long term strength loss.
7-Increased water demand.
8-Decreased 28-day and later strengths.
9-Increased tendency for differential thermal cracking.
10-Greater variability in surface appearance.
11-Increased permeability
Precautions for Hot Weather Concreting
Following general precautions will help in performing a successful concreting project in hot weather conditions, and mitigating the negative impacts of hot weather. These precautions would be helpful during concrete production and delivery, and will improve the durability performance of concrete by minimizing undesired cracking.
1- Use materials and mix proportions that have a good record in hot-weather conditions, 2- Cool the concrete or one or more of its ingredients, 3- Use a concrete consistency that allows rapid placement and consolidation, 4- Reduce the time of transport, placing and finishing as much as possible, 5- Schedule concrete placements to limit exposure to atmospheric conditions (i.e. at night or during favorable weather conditions)
6-Covered environment: The concrete can be done in a covered environment.
7-Chilling: The chilling of aggregate can be done by watering or keeping them covered.
8-Efficient work force: employ efficient workforce and machinery to improve the handling.
9-Use of low heat cement: Use low heat cement.
Hi
In a hot weather like the one in the summer of the gulf region in middle east, sometime an addition of ice blocks in order to satisfactory moisture content and temperature in freshly cast concrete for a definite period of time immediately following placement. This process prevents or replenishes the loss of moisture from the concrete; It maintains a favorable temperature for hydration to occur for a definite period.
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