Author: Aritra Pal; Entry No. 2013CEC8314
The Aim of this study is to select a better choice of water tight concrete for the water proofing construction of water retaining structures like tanks, reservoirs, swimming pools etc. This paper includes the study of early age & later age properties of concretes with Chemical Admixtures & Supplementary cementecious materials, from the aspect of water tightness & durability.
2.0 Principle of Water Tightness:
• Concrete should be dense & durable
• Concrete must have the capacity to withstand hydrostatic pressure without water seepage.
• Concrete generally contains voids and cracking can be happened by the external loading or internal thermal and shrinkage strain, structural movement etc. These voids and cracks can become the path for water seepage.
• For cracks due to external loading nothing can be done with concrete properties but for internal shrinkage strain good mix design is required with limited cement content, proper placing & curing.
• Dense and durable concrete can be achieved by low water to cement ratio & for the proper placing & curing workability of the concrete mix is one of the important factors.
• For high strength, low permeability, high durability & workability use of admixture is recommended.
3.0 Some Properties that have to be taken care:
• Permeability: Concrete is a mixture of cement & aggregate. Aggregates are generally dense materials so permeability of the cement paste determines the water tightness of the concrete. The gel pores in the cement paste are very small, generally they do not affect the density, but the capillary pores with the micro & macro cracks can form the passage for the water. Capi...
... middle of paper ...
... the voids and the micro cracks thus they can reduce the permeability & increase the water tightness.
• Pozollanic reaction will convert the high dense C-S-H with large cavities to relatively low density C-S-H with smaller voids
• This properties can increase the strength and durability of the concrete.
• Due to the filler effect of the SCM permeability of the concrete will be decreased effectively.
• Steel Corrosion: The low permeability of the concrete will prevent the chloride penetration and thus reduce the chance of corrosion in the reinforcement steel.
Due to the impermeability in the concrete carbon-di-oxide gas cannot penetrate into the concrete and the risk of carbonation will be minimized thereby the attack in steel by carbonation will be reduced.
• Acidic Environment: Due to the presence of large amount of calcium hydroxide
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