Cracks

Non-structural cracks occur due to climatic changes, poor curing, bad quality of sand, lack of moisture in climate, the moment of footing below ground, natural disasters, due changes in groundwater level, and also expansion and contraction of soil, and Finally corrosion of Steel, etc.

Cracks in structure or plaster are a very serious problem, this affects the quality of construction. To solve this problem we will have to take special Precaution while doing plaster work and before and after plasterwork. Engineers, supervisors, and masons should have adequate knowledge about the Process of Plasterwork.

Reasons behind cracks in Plaster

1. Due to loss of moisture- (Shrinkage Cracks)
   Initially, when cement comes in contact with water, cement starts its setting process at the same time, the heat of hydration will start and generates heat which we have to control by providing required moisture. If cement not gets a sufficient amount of moisture or water this will leads to develop in cracks on plastered surface.During hot weather when temperature increases about 35 degree Celsius evaporation process get accelerate. Hot climates evaporate moisture from plaster, and also hot wind and dry wind makes plaster surface dry. This process leads to develop cracks in the plaster. This type of cracks called shrinkage cracks.

2. Cracks due to temperature changes. (Thermal Cracks)
   This type of cracks also called as a Thermal Cracks. When the plaster surface is exposed to the external climatic condition, in the day time the temperature is hoter as compare tonight. Due to these temperature changes in such a short period of time, this leads to develop cracks in the plaster surface.

3. Cracks due to fine sand and silty sand
   If silt content excess in the sand above a limit, it absorbs more moisture content from plaster surface, which is required at the time of heat of hydration process & moisture content get reduced which leads to Cracks in plastered surface.

Silt particles are very fine in size, which is finer than 150 micron. It absorbs more water at the time of mixing of mortar to get required workability. This will leads to bleeding or drying, which helps to develop cracks on plastered surface.

1. Cracks due to corrosion- When the protective layer of steel is weak to protect steel from the weather, which leads to corrosion of steel. When corrosive layer comes over steel, It increases the volume of steel. Due to this stress is developed on the layer covering steel. Which develops cracks on the Concrete layer over steel.

2. Cracks because of structural defects & bad workmanship.
   Sometimes cracks occur due to the bad quality of workmanship. Workers & supervisor should have adequate knowledge to avoid cracks. Many times it is observed that workers don’t give importance on a joint filing, curing, and application of chicken mesh, etc.

Water-cement ratio
In most of the cases, it is observed that worker add more amount of water than required at the time of mixing of mortar. If the water-cement ratio is less, then strength will be high. If the water-cement ratio is more, strength will be low.

Many times defective RCC structure may lead to development in cracks. Excessive bending moment leads to develop excessive stress on block wall which develops cracks. Defective design of footing develope movement in structure this will result in a crack in structure.

1. Natural disasters-
   Natural disasters like earthquake, flood, excessive wind load may also reason for developing cracks in the structure. In the case of earthquakes, vibration is transferred through the soil and which is followed by the structure resting on the soil. Due to which structure moment occurs because of these cracks can take place.

During flooding excess amount of water is transferred from one place to another and with that water, earth particles may move due to flooding. Because of this settlement of structure can take place, in that case, these cracks can be developed. In case of high rise buildings due to heavy wind pressure, structural movement can take places this may lead to the formation of cracks.