CONCRETE FOR WATER STRUCTURE

Water Retaining Structure : Reservoir, Water Tank

Presented by :Intan Madya Ratna146060112011002

ADVANCED MATERIAL ENGINEERING

Concrete for Water Structure

Concrete is an excellent building material. Man has been using concrete to build all types of structures for many centuries.

It has proven to be very durable and very strong in compression.

Concrete for Water Structure

Reinforced concrete structures are widely used for

the storage of water and other aqueous liquid.

The more common types of water-retaining structures are reservoirs, water tanks, pump

station, etc.

Water-Retaining Structure

Durability of Concrete For Water-Retaining

Structure Unfortunately, with the introduction of reinforcing steel into concrete, a new problem was created that affected the durability of concrete. When embedded reinforcing steel corrodes, it can cause concrete to crack and spall.

These cracks and spalls not only reduce the structural integrity of the concrete, but they also allow deleterious elements to freely enter into the concrete to accelerate the rate of deterioration.

Other problems that affect the durability of concrete in water-retaining structure include abrasion, chemical attack and freeze-thaw. These destructive forces can significantly reduce the service life of the structure.

Factor Affecting Durability

FACT !!All concrete (for water structure or

other) deteriorates over time. The rate at which concrete deteriorates is a function of two factors:

1.The quality of the concrete, and2.The environment to which the

concrete is subjected.

Factor Affecting Durability

CORROSION PROTECTION

CORROSION PROTECTION

Abrasion, Chemical Attack and Freeze-Thaw

Protection

Abrasion, Chemical Attack and Freeze-Thaw

Protection

WATERTIGHTNESS“Watertight” is a mix concretes designed to protect a structure from water ingress or to retain

water within a structure. Whether above-ground or

underground products, in many instances we want to prevent

fluid from getting from one side of the concrete wall to the other.

In making our structures watertight, there are two areas

we’re concerned with: the concrete itself, and joints and

penetrations.

The Two P’s of Watertightness

In making our structures watertight, there are two areas we’re concerned with: the concrete itself, and

joints and penetrations.

When discussing watertightness of concrete, we must consider the two P’s: porosity and

permeability.

WATERTIGHTNESS RULE

Watertightness Rule #1Use a low w/c ratio mix design1.The w/c ratio is the most important factor in concrete design. The water content in a mix controls the moisture’s rate of entry (which may contain aggressive chemicals) and the movement of water during the freeze-thaw process.2.The more excess water in a mix, the lower the strength, durability and watertightness. Excess mix water results in capillary pores – entrapped air pockets in hardened concrete that will reduce its resistance to leakage. On the other hand, too little water can cause placement difficulties and undesirable effects such as honeycombing.3.Durability and densification can also be improved with admixtures.

WATERTIGHTNESS RULE

Watertightness Rule #2Meet minimums for cementitious material

1.Sufficient cement must be used to achieve required strength, but high cement contents can causeshrinkage and increase cracking2.Rich concrete mixes provide a denser, more impermeable and superior finished product. Consequently, specifying that cement content not exceed a minimum amount is recommended. In the case of watertight structures, a minimum cement content of 564 lbs/cu yd is suggested.3.The use of supplementary cementitious materials such as fly ash, slag and silica fume can also increase concrete’s density, thus reducing capillary porosity and permeability.

WATERTIGHTNESS RULE

Watertightness Rule #3Use well-graded aggregates1.Gradation of the aggregates is a most important factor and should be of primary consideration. Shape and texture of the particles will also affect workability. 2.Rounded coarse aggregates are preferred, if available, as they can be more uniformly placed.3.Fine aggregate (sand) with a higher fineness modulus (> 2.8) is preferred, as it will provide the necessary coarser particles in the mid-range of the combined aggregate

WATERTIGHTNESS RULEWatertightness Rule #4

Follow quality manufacturing processes

1.Quality concrete manufacturing processes are critical to the production of durable, watertight concrete products. Proper attention to important pre-pour activities such as maintaining prescribed mix proportions, form cleanliness, and specified reinforcement placement and minimum cover is very important. 

2.Concrete must be adequately cured if its optimum properties are to be developed. An adequate supply of moisture, either by covering or other means, is important to ensure full hydration and reduce the porosity level such that the desired durability is

WATERTIGHTNESS RULE

Watertightness Rule #5

Execute joints and penetrations carefully1.A system is only as strong as its weakest link. Close attention to all jointed, connected and sealed areas is absolutely necessary to ensure watertightness. Potential differential settlements and thermal movements must be addressed in the design and manufacture of joints and penetrations.2.Construction joints need to be adequately prepared and bonded to ensure a complete contact between two pours.

DESIGN OF WATER-RETAINING STRUCTURES

CODES OF PRACTICES :• British Standard Code Of Practice BS 8007:

1987 Design of concrete structures for retaining aqueous liquids.

• American Concrete Institute ACI 350 R-83: Concrete Sanitary Engineering Structures

• Australian Standard AS 3735 – 1991 Concretes Structures for Retaining Aqueous Liquids

• New Zealand Standars NZS 3106 : 1986 Code of Practice for Concrete Structures for the Storage of Liquids

CONCLUSION• Durability of concrete for water-retaining structure generally

affected by corrosion on reinforcement, Abrasion, Chemical Attack and Freeze-Thaw Protection

• In order to extend the durability of concrete in hydraulic structure, we must make our concrete “watertigtht” enough. Rules for making watertight concrete are :– Use a low w/c ratio mix design– Meet minimums for cementitious material– Use well-graded aggregates– Follow quality manufacturing processes– Execute joints and penetrations carefully• To protect concrete in water tanks, polymer-modified

cementitious coatings have been used with much success. However, the quality of the polymer component of the coating is an important ingredient that dictates just how flexible and dense the coating will be. Acrylic and styrene-acrylic based polymers provide the desired properties.