race 08

admixture

Admixture Admixture is defined as a material other than cement ,water, and aggregates,that is used as an ingredient Of concrete and is added to the batch immediately before or during mixing. Until about 1930 additives Admixures though used were not consider on important part on concrete technology since when then there has been an in this in the use of admixture. there was specifically developed in japan and germany around 1970.later on the they were made popular in usa &Europe. Unfortunately the use of plasticizer and super plasticizer have not become popular in India till recently 1985.were not manufactured in India and they were to be imported,and hence costly. Lack of of education and awareness of the benefits accured by the use of plasticizers,we were used to making generally low strength concrete of the type m15 to m30, which do not really need the use of plasticizers. Now, since early 1980, some internationally renowned companies collaborated with Indian companies and have started manufacturing chemical admixtures in India.as a part of marketing they started educating consultants,architects,structural engineer and builders about the benefits of using admixtures.we in India have have also started using higher strength concrete for high rise building and bridges. Sometimes many admixtures affect more than one property of concrete. At times, they affect the desirable properties adversely. Sometimes more than one admixtures is used in the same mix.the effect of more than one admixture is difficult to predict. As per the report of the aci committee 212, admixtures have been classified into 15 groups according to type of materials constituting the admixtures, or characteristic affect of the use. Classification of admixtures • Plasticizers • Super plasticizers • Retarders and retarding plasticizers • Accelerators and acceleraring plasticizers • Air entaining admixtures • Pozzolanic or mineral admixtures • Damp-proofing and waterproofing admixtures • Gas forming admixtures • Air entraining admixtures • Alkali – aggregate expansion inhibiting admixtures • Workability admixtures • Grouting admixtures • Corrosion admixtures • Bonding admixtures • Fungicidal,germicidal insecticidal admixtures • Colouring admixtures Plasticizers(water reducers)