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In the Name of “ALLAH” most
Gracious most Merciful
Topic
ADMIXTURES OF CONCRETE
4
Admixtures
INTRODUCTION
O Admixtures is defined as a material, other than,
O Cement
O Water
O Aggregate
O That is used as an ingredient of concrete and is added to the batch immediately before or during mixing.
O Admixtures are used to modify the properties of ordinary concrete so as to make it more suitable for any situation.
Admixture in Liquid form
Admixture in Solid form
HISTORY
O History of admixtures is as old as the history of concrete. It embraces a very vast field, but a few type of admixtures called Water Reducers or High Range Water Reducers, generally referred as plasticizers and superplasticizers, are of recent interest.
O Specially developed in Japan & Germany around 1970.
Why Are They Used?
OTo modify properties of fresh & hardened concrete.
O Increase slump and workability .
ORetard or accelerate initial setting .
O Increase strength (compressive, tensile, or flexural)
OReduce or prevent shrinkage .
Why Are They Used?
OModify the rate or capacity for bleeding
OReduce segregation
ORetard or reduce heat evolution during early hardening
OTo ensure the quality of concrete during mixing, transporting, placing & curing.
FUNCTION OF ADMIXTURE
O To improve workability of fresh concrete
O To improve durability by entrainment of air
O To reduce the water required
O To aid curing
O To impart water repellent / water proofing property
FUNCTION OF ADMIXTURE
O To retard setting
O To improve wear resistance (hardness)
O To offset / reduce shrinkage during setting & hardening
O To impart colour to concrete
O To offset or reduce some chemical reaction
CLASSIFICATION OF
ADMIXTURES
O Chemical Admixtures
O Mineral Admixtures
Types of Chemical Admixtures
According to characteristics effects produced by them chemical admixtures used are as follows.* Plasticizers* Super Plasticizers* Retarders and retarding admixtures* Accelerators and Accelerating Plasticizers* Air-entraining admixtures
* Grouting admixtures
* Air – detraining admixtures
* Gas – forming admixtures
* Corrosion inhibiting admixtures
* Shrinkage reducing admixtures
* Water or damp proofing and permeability reducing admixtures
Minerial Admixtures
O Cementitious
O Pozzolanic
O Ground Granulated Blast Furance Slag (GGBS)
O Fly ash
O Silica Fume
O Rice Husk
The End
Thank
You
