Concrete is used in construction because it has a high capacity for cohesion and strength to bear the load. However, the performance of concrete is significantly affected by inclement weather conditions.
Concrete has to face different problems due to increases in temperatures and accelerated hydration, hot weather, etc. So, we have to know the effect of hot weather on concrete to get the required amount of quality and integrity of concrete structures over time.
Durable and Strong concrete is very important for any type of construction for the safety of life and properties. So, concrete should be carefully prepared according to design and load on the structure. But, even if we prepare concrete according to the design we have one issue with nature i.e. weather.
Here we will discuss the effect of hot weather on Concrete, the effect of cold weather on Concrete, and their precaution.
Effect of Hot Weather on Concrete
There will be more problems for concrete if the temperature of the environment is more than 40 degrees Celsius. The major effect of Hot weather on concrete is given below.
1. Increase demand for water:
Warm weather speeds up the hydration process of concrete, resulting in a quicker setting time and early stiffening of concrete. So, more amount of water is required to keep the concrete mix workable and to prevent premature hardening.
The increased demand for water increases the water-cement ratio, which affects negatively on the strength and durability of concrete.
2) Rapid Evaporation
Higher temperatures and lower moisture levels evaporate the moisture from the surface of the concrete. This rapid loss of moisture creates plastic shrinkage cracks, especially in the early stages of curing.
These cracks reduce the capacity of concrete to withstand external stresses, which also leads to loss of surface integrity.
3) Thermal Expansion and Contraction
Concrete expands and experiences internal stresses in hot weather due to high temperatures. On the other hand, It contracts during cool evening temperatures which creates breakage and reduced the hardness of concrete.
4) Reduced Setting Time:
High temperatures accelerate the chemical reactions involved in concrete setting time. This rapid setting time reduces the time to handle, place, and finish the concrete before the initial setting time i.e. it becomes unworkable.
5) Alkali-Silica Reaction (ASR):
Hot weather increases the risk of salt silica reaction (ASR) in concrete. Cement alkalis react with weak aggregate to produce ASR, to form a gel-like substance.
This gel expands longitudinally and creates internal stresses and breakage within the concrete.
Furthermore, It has many small effect of hot weather on concrete like,
- Provide Less time for finishing like, leveling, and pouring small ditches.
- Difficulty in air entrainment & curing.
- Has less time for transportation of concrete
- Increase the overall cost of construction
- Reduce the efficiency of manpower. etc.
So, we discussed the effect of hot weather on concrete. We can not control nature but we can take some effective precautions to prepare and place concrete to get hard and durable concrete for our structure.
Precautions for effect of hot weather on concrete
a) Management of materials
- Aggregate should be stored in the shade
- Regular sprinkling of water to aggregate
- Using cold water (upto 5-degree Celsius)
- Use low-heat cement
- Use of retarding admixtures
b) Management of concreting work
- Scheduling the concreting work in the evening (but with sufficient lighting)
- Use of more masons for quickly finishing the work
- Transporting the concrete in a deep container
- Covering of concreting with moist materials as early as possible
c) Curing of concreting
- The concrete should be cured with cold water
- The surface shall be continuously made wet either by pending or using water-absorbing materials in the surface like cloth, jute, sand, etc
Effect of Hot Weather on Concrete
The major effects of cold weather in the concreting area follow,
a. Delay in setting & hardening
- Rate of hydration decrease with a decrease in temperature
- It increases the time from work & curing
- The progress of work will be slow which affects the economy
- It also makes the concrete more vulnerable to frost action.
b. Freezing of concrete in the early stage
- If water is frozen, then the hydration stops which makes the concrete weak.
- The expansion of water in concrete during freezing induces cracks in low-strength concrete, as the hardening process is not sufficient.
- It Affects the durability of concrete
c. Freezing & thawing cycle.
The alternate freezing & thawing cause early disintegration in the concrete.
Precautions for cold weather concreting
- Shielding of wind in the working area & Insulating with insulators around the site should be well managed for quick delivery finishing & covering of concrete with insulators like straw, jute, sacks, plastic sheets, waterproof paper, etc.
- The material for concrete can be preheated with water in the container, coarse aggregate in closed stream coils under a stoke pip, steam or hot air, or sand in steel plates while cement should not be heated.
- From work & subgrade can be heated before placing of concrete.
- A special type of cement-like RHC, high aluminum cement, etc. can be used that has a high rate of hydration & high heart of hydration & keeps the concrete warm.
- Accelerating admixture is also commonly wed which increases the rate of hydration.
- The cycle is a good accelerator, but use in higher amount increase the corrosion in steel embedded in RCC.
- Electrical heating for curing can be done on concrete to prevent from too much cold weather.
Hot weather conditions can fundamentally affect the performance and hardness of concrete. Concrete technicians and engineers must be aware of the difficulties created by the hot climate on concrete and find out appropriate mitigation techniques for getting long-term construction.