ADMIXTURE FOR CONCRETE

ADMIXTURE FOR CONCRETE
[CODE NO.3056]  

Admixtures are chemicals in the form of powder or liquid which are added to the concrete during the mixing process, at the plant or  inside  the  transit mixer, prior to  casting,  in  order  to improve  certain properties of the concrete or to add  properties which are not present in regular concrete.

Basically, concrete admixtures are divided into two groups:

Plasticizers, and superplasticizers, the main difference between them being the extent of the admixtures ability to reduce the quantity of water required, whilst maintaining or even improving the concretes workability.

In general the difference between the two types can be defined as follows: The plasticizer can reduce up to 10% of  the water  required  in  the mix  whilst  maintaining  the  concretes workability,  while the superplasticizer can reduce 20% and  more of the water quantity.

Chemocrete Ltd., of the Readymix Group, is the Groups center for the production and supply of Chemicals for building.

Modern concretes almost always process additives, either  in the  mineral  form  or  chemical  form.  Particularly,   chemical admixtures  such  as  water  reducers  and  set  controllers  are invariably  used to enhance the properties of fresh and  hardened concrete.

A Chemical Admixture is any chemical additive to the concrete mixture that enhances the properties of concrete in  the fresh or hardened state. This does not include paints or coatings ACI 116R (2000). Defines the term admixture as a material  other than water, aggregates, hydraulic cement and fiber reinforcement, used  as  an ingredient of concrete or mortar, and added  to the batch immediately before or during its mixing.

A number of types of chemical admixtures are used for concrete. The general purpose chemicals include those that reduce the water demand for a given workability (called water reducers), those entraining air in the concrete for providing resistance to freezing  and  thawing action (called air entrainers)  and  those chemicals that control the setting time and strength gain rate of concrete  (called accelerators and retarders). Apart  from  these chemicals, there   are   others  for   specials   purposes-namely, viscosity  modifying,  shrinkage  reducing  chemicals   corrosion inhibiting  admixtures,  and  alkali-silica  reaction  mitigating admixtures.

Apart from the multitude chemical admixtures, a number of different types and brands of cement are also available in the market  today. With the increasing number of types and brands of cement,  as  well as variants of  the  water-reducing  chemicals, there are issues that arise related of the compatibility  between these two ingredients of concrete. Most users apply a  trial-and-error approach to these chemicals, often resulting  in an unfortunate  negative experience and/or  low  cost-effectiveness, which produce a bias against admixtures in general.

Common  problems that arise as a result  of  incompatibility between cement and water reducers are rapid loss of  workability, excessive  quickening / retardation of setting and low  rates  of strength  gain.  Very often, there  even  exists  incompatibility between  a  particular chemical and a certain batch of  the  same otherwise  compatible cement, indicating that the nature  of  the problem  is  complex and needs further  understanding.  Moreover, high  performance concretes, which are in wide use today,  almost always  incorporate a mineral admixture or filler such as  silica fume, fly ash and limestone powder. This further complicates  the physico-chemical  behavior of the cement-based system  since  the mineral admixtures play an important role in the evolution of the hydration reactions and the availability of free water during the early ages of concrete.

INTRODUCTION
ADMIXTURES FOR CONCRETE
CHARACTERISTICS OF THE DIFFERENT CHEMICALS
MECHANISM OF ACTION OF WATER REDUCERS
USES AND APPLICATION
CHEMICAL ADMIXTURES FOR CONCRETE
PROPERTIES AND CHARACTERISTICS
ADVANTAGE OF SUPER PLASTICIZER (LIQUID)
CLASSIFICATION OF CONCRETE ADMIXTURES
SPECIFICATION OF CONCRETE ADMIXTURE
INCOMPATIBILITY OF SUPERPLASTICIZER
DETAILS OF ADDITIVES USED IN READYMADE
CONCRETE SUPER PLASTICIZER
MARKET SURVEY
GLOBAL MARKET POSITION OF CONCRETE MIXTURE
PRESENT MANUFACTURERS/SUPPLIERS OF READYMADE
CONCRETE
PERFORMANCE AND DOSAGE OF PREVAILING SUPERPLASTICIZER
FORMULATION OF CONCRETE ADMIXTURE
FORMULATION OF WATER REDUCING AND RETARDING ADMIXTURE
FORMULATION OF WATER REDUCER (LIGNOSULFONATE BASED)
FORMULATION OF HARDENING ACCELERATOR
FORMULATION OF READYMADE CONCRETE ADMIXTURE
SUPERPLASTICIZER WITH RETARDER
MANUFACTURING PROCESS OF READYMADE CONCRETE
ADMIXTURE SUPER PLASTICIZER WITH RETARDER
PROCESS FLOW DIAGRAM
COST EFFECTIVE SUPER PLASTICIZER FOR READYMIX CONCRETE
SUPPLIERS OF RAW MATERIALS
SUPPLIERS OF PLANT & MACHINERY

APPENDIX – A:

1.      COST OF PLANT ECONOMICS
2.      LAND & BUILDING
3.      PLANT AND MACHINERY
4.      FIXED CAPITAL INVESTMENT
5.      RAW MATERIAL
6.      SALARY AND WAGES
7.      UTILITIES AND OVERHEADS
8.      TOTAL WORKING CAPITAL
9.      COST OF PRODUCTION
10.      PROFITABILITY ANALYSIS
11.      BREAK EVEN POINT
12.      RESOURCES OF FINANCE
13.      INTEREST CHART
14.      DEPRECIATION CHART
15.      CASH FLOW STATEMENT
16.      PROJECTED BALANCE SHEET