During manual concreting of a raft footing which was designed for M25 grade concrete, the estimated cement required was 240 bags, while the laborers due to sheer negligence have added only 140 bags. The Soil conditions are good. There was more coarse aggregate added.
What is the possibility of failure and what could be the remedy?
Due to less of the quantity of cement, water/cement ration increased which also increase the void ratio.
It’s affected the future durability.
For remedial measures , first, need to investigate the foundation for various measures and then do suitable remedial measures.
Effects due to less amount of cement mix
Effect of cement content on strength of footing:
The result reveals that the strength of concrete Foundation increases with increasing cement content in it.
However, for concrete with cement content more than 150 kg per metre cube then the strength increases with the increase in the size of coarse aggregate up to 25 mm and decreases as the aggregate size increases beyond 25mm.
Without a proper range of cement in the mixture then low strength development or excessive shrinkage may occur leading to premature deterioration.
Madeh Izat Hamakareem
This problem needs an adequate investigation to determine the weakness of the foundation, and then specify remedial options if needed.
The strength of the foundation should be evaluated, then structural designer can check the load-carrying capacity of the foundation, and ultimately decided whether remedial measures are needed or not.
Adequate quantity of cement content ensures sufficient alkalinity and cement paste volume to fill spaces between compacted aggregate particles. So, durability issues may also arise in the future.
The remedial measures are determined based on the mat foundation weaknesses and conditions. Hamidul Ahasan, Shajal Khan, Ahmedul Hassan, Raquib Ahsan, and Mehedi Ahmed Ansary published an article under the title Use of Jet Grouting in Retrofitting of a RMG Factory Building in Chittagong,
Bangladesh. They discussed a repair method to increase the load-carrying capacity of the mat foundation that supports four-story building.