Vibration Of Concrete And Water Requirements Of Concrete Sai Sumanth Reddy.G Civil-3B:13951A0185 IARE

CONTENTS Introduction Internal Vibrators Formwork (external) vibrators Table vibrators Surface vibrators Uses of vibration Common water requirements of concrete Quality of water

Introduction Compaction of concrete is the process adopted for expelling air from concrete. In process of mixing , transporting and placing, air voids may be entrapped in concrete , these voids weakens the strength, hence Compaction is required. The Compaction is Commonly Done By Vibration The vibration of concrete is commonly done by different types of vibrators given below: 1)Internal vibrators 2)Formwork (external) vibrators 3)Table vibrators 4)Surface vibrators

Internal vibrators Internal Vibrators: These are commonly used and also known as needle or immersion or poker vibrators. It is run by petrol engine or air compressor, the frequency is up to 12000 cycles per minute and its length varies from 25-90 cm. The bigger needle is used in construction of dams . Some times a blade may be facilitated where the needle cant be worked the blade works efficiently

Formwork Or External Vibrators Formwork Vibrators(External Vibrators):These are generally used in concreting columns, thin walls or in casting of precast units. In this the vibration is given to the formworks such that all the concrete in vicinity of it will be compacted, this is done where the reinforcement interferes the internal vibration. It is less efficient than internal vibrators.

Table Vibrators Table Vibration : This is a special case of formwork vibrators where the vibrator is clamped to a table ,any thing that kept on the table can be vibrated . This is mostly used in vibrating concrete cubes and in laboratories A table vibrator with large platform is called as Platform vibrator

Surface Vibrators Surface Vibrators: These are sometimes known as “screed board vibrators”. A small vibrator is placed on a screed board which gives an effective method of compacting and leveling of thin concrete members such as floors, roof slabs and road surfaces . For different types of surfaces different types of screeds are used .

Uses Of Vibration Vibration is a common method used for compaction of concrete it has many uses some of them are given below: The loose mass of concrete is stiffened and denser by means of vibration The voids and the gaps located in the concrete can be removed The concrete with low water/cement ratio can be easily spreaded at the place by means of vibration The strength of the concrete is improved and ultimately the hardness Besides some defaults vibration is mostly accepted method for compaction

Quality Of Mixing Water A popular yard-stick to the suitability of water for mixing concrete is that, if water is fit for drinking then it is fit for making concrete . It may be true for all conditions Generally the water which is used for concrete making is to be potable The ph of water must be in between 6-8 and free from organic matter and other impurities Mostly the suitability of water is founded by comparing 7 and 28 days strength of concrete made by it with the strength of cubes made up of distilled water. If the compressive strength is up to 90% then that water is acceptable

Effects of Impurities in Water The impurities present in water effects much over the strength and setting time of concrete The carbonates and bi-carbonates of sodium and potassium effects the setting time of concrete (accelerates the setting time)and also reduces the strength of concrete .these may be accepted in lower concentration. The salts of manganese, tin, zinc, copper and lead causes the reduction in strength of concrete. Various salts of sodium effects the initial strength of concrete The silt and suspended materials interfere with setting , hardening and bonding characteristics of concrete.

Tolerable Concentration Of Some Impurities Of Mixing Water Impurity Tolerable Concentration Sodium, Potassium, Carbonates & Bi-Carbonates Up to 1000PPM (Total). Chlorides Up to 10,000PPM. Sulphuric anhydride Up to 3,000PPM. Sodium sulphide Even 100ppm it warrants testing Sodium iodate ,Sodium sulphate , Sodium arsenate , Sodium borate Very low

Impurity Tolerable Concentrations Sodium hydroxide 0.5% by Wt. of cement, provide quick set is not induced Salt and Suspended particles Up to 2,000PPM. Mixing water with high suspended particles is allowed to stand in a setting basin before use Total Dissolved salts Up to 15,000PPM. Organic Material Up to 3,000PPM (Humic acid less than 780PPM) PH Should not be less than 6

A Presentation By Sai Sumanth Reddy .G Civil-3B:13951A0185 IARE