[C M Dordi]

BATCHlNG AND MIXING OF MORTAR AND CONCRETE INGRADIENTS
Taken from : Ambuja Technical  Literature Series - 6

1.0 INTRODUCTION

Concrete is the most widely used construction material in the world. This material is not going to be easily replaced by any other material on account of its economical as well as technical advantages.
This material is generally produced at site in our country and therefore needs to be carefully supervised and controlled in order that it performs the way it is technically expected to perform. Concrete is made from raw materials such as cement, natural and manufactured aggregates, water and at times concrete additives (chemicals). It is worth noting that cement and aggregates are manufactured or obtained from natural solid stone which
is quarried, crushed, ground, screened and processed to give the required physical and chemical properties. The same materials are then hatched, mixed with water, transported, placed, compacted and cured to give concrete of desired shape which after it is hardened resembles a solid stone.

This booklet covers the hatching and mixing processes of concrete manufacture. The processes of hatching and mixing of concrete or mortar materials  are very similar to preparations of a dish in cookery as per a recipe wherein various ingredients depending on their individual properties have to be mixed in correct proportions to give the required flavour and taste. The process of hatching and mixing are therefore as important to concrete as a accurately proportioned and cooked dish is important to our taste buds.
 
Batching and mixing are extremely important parts of mortar and concrete manufacture as they influence properties of concrete both in plastic as well as in hardened stages.

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[Manish Jain]

2.0 INFLUENCE OF BATCIDNG AND MIXING PROCESSED ON FRESH CONCRETE

2.1 The factors which influence the quality of fresh concrete are as follows :
2.1.1 CONSISTANT QUALITY OF RAW MATERIALS
Consistent quality of raw materials is very essential. Batching and mixing is more consistent if the raw materials with consistent specific gravity, fineness,
grain size, strength and other properties are used. Variation in grading and fineness can; create variations in concrete quality as the water demand or
workability for the same proportions may increase or decrease. 

2.1.2 ACCURACY. OF BATCHING (VOLUMETRIC I WEIGHMENT)
Batching accuracy is also important. It is preferred to do weigh hatching and not volumetric hatching of cement and aggregates. However, if accurate weigh
hatchers are :not available it is preferable to do proper volumetric hatching. Bulkage correction for natural moist sand is necessary in case of volumetric
hatching. ·
2.1.3 ADEQUACY OF MIXING (MANUAL/MECHANICAL)
Mixing is generally practiced manually in case of mortar and at times even for concrete. Manual mixing is not recommended until
and unless the work is carried out by trained skilled worker in a systematic manner. Machine mixing is faster and more efficient than manual mixing.
It is often observed that mixers Figure 1 : Inadequately designed mixer causes mix to segregate. 
used in our country are not properly
designed to cater to adequate mixing of concrete materials . Care should be taken that mixers available on site are capable of mixing the concrete ingredients.

2.1.4 MIXING TIME
It is necessary to ensure that adequate time is given for proper mixing of concrete ingredients. However; mixing time may greatly depend on the workability of concrete mix, type of mixer and it's size or capacity.

2.1.5 BATCHING AND MIXING EQUIPMENTS AND METHODS
There are various types of hatching and mixing equipment's and methods that is to say from manual to most sophisticated computerized hatching and mixing. 
Mechanization improves quality of batching and mixing, its speed and thereby can most often result in economy. 
Manual batching and mixing is more prone to errors and slower in speed than mechanical arrangement. Volumetric batching if done with proper boxes (farmas) and filled up to brim and levelled is quite accurate for batching aggregates.

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 batching and mixing of mortar and concrete ingredients-fd.pdf