Harsh weathers for sure effects the working schedules in a civil engineering project. Whether it is too hot or too cold outside the considerations in the mind of a construction manager is \”How to fight with this new hurdle\”. Concrete shrinks and expands due to temperature variations which is very critical as far as fresh pouring is considered because if that is not controlled it may proved fatal for the pour.
|Concrete pouring in Cold Weather
This next time whenever you are pouring a concrete you should consider the temperature and measure it at site to avoid such troubles.
- Keep water – Cement ratio on lower side as much as workable.
- Transport concrete mix by covered transit mixers.
- Use hot water for mixing concrete at the batching plant.
- Keep formwork insulated by wood liner.
- Prior to pouring concrete was concrete surface and re-bars hot water.
- Maximize resources to quickly complete concrete pouring exercise by using more transport equipment.
- Cover the concrete immediately after pouring with proper insulating sheet.
- Keep formwork for longer time. Assure that concrete develops sufficient strength for safe removal of forms.
- Strip the formwork during rising temperature.
- Observe temperature of concrete at all steps.
- Vertical day joint in concrete in cold weather.
- The large quantity involving more than 200 m3 of concrete in each pilecap led the engineers to plan workability of the site situation.
- It should be kept in mind that.
- The cold weather does not permit to work upto late hours in the evening. Hence, it was agreed upon to provide day joint at suitable position and to complete the work thereafter.
- Accordingly, It is proposed to provide slightly inclined stopper in form of wooden strips to be accommodated between the rebars. This arrangement will allow planned quantity of work during day time in full depth as it would mainly retain the heat of the concrete evolved during the chemical reaction.
- The workable position of day joint could be between 1/3 and ¼ span where there are no extra re-bars.
- Apply bonding agent in the joint
- Before the next pour all loose material at joint shall be cleaned and green cut shall be made.
Steps to pour concrete in Pile Cap
Following are some of the steps that will guide you to a stable and harmless concrete.
1. Prepare stable working platform upto bottom level of pile cap.
2. Excavate and clean the area for pile cap.
3. Check ground level and place approved lean concrete for the pile cap.
4. Next day mark the layout of the pile cap and the re-bars
5. Place specified reinforcement bars in position as shown in the construction drawing and tie them firmly. Provide spacers below the reinforcement bars to provide desired cover to the reinforcement.
6. Place shuttering plates all around in position. Provide firm supports to remain in position during concreting.
7. Wash all transit mixers with hot water immediately before loading.
8. Transport approved fresh concrete from batching plant to site.
9. Collect concrete samples for testing as specified.
10. Start pouring concrete by dropping through chute, till the concrete is place in full depth as shown in the construction drawing and to the length as planned for the day.
11. While placing concrete, operate vibrators to compact concrete and trowel the top.
12. Make sure surfaces in contact with concrete are free of ice and snow.
13. Good quality thermometers shall be kept at site for checking air temperature.