Mix Design

(FOR BANGAlORE REGION)
DESIGNED By: G.PRABHAKARAN M.TECh, QA/QC ENGINEER

Mix proportioning for a concrete of M35 grade is given in A·I to A-ll.
A·I STIPULATIONS FOR PROPORTIONING

a) Grade designation : M35
b) Type of cement : OPC 53 Grade conforming IS 12269
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 340 kg/m³ (IS 456:2000)
e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
f) Workability : 100-120mm slump
g) Exposure condition : Moderate (For Reinforced Concrete)
h) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed Angular Aggregates
m) Maximum cement content : 390 kg/m³
n) Chemical admixture type : Super Plasticizer ECMAS HP 890

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(FOR BANGAlORE REGION)
DESIGNED By: G.PRABHAKARAN M.TECh, QA/QC ENGINEER

Mix proportioning for a concrete of M40 grade is given in A·I to A-ll.
A·I STIPULATIONS FOR PROPORTIONING

a) Grade designation : M40
b) Type of cement : OPC 53 Grade conforming IS 12269
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 360 kg/m³ (IS 456:2000)
e) Maximum water-cement ratio : 0.40 (Table 5 of IS 456:2000)
f) Workability : 100-120mm slump
g) Exposure condition : Moderate (For Reinforced Concrete)
h) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed Angular Aggregates
m) Maximum cement content : 420 kg/m³
n) Chemical admixture type : Super Plasticizer ECMAS HP 890

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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

While carrying out Concrete Mix Design, there are chances that we do not consider some technical points resulting the production of poor quality concrete. This is best illustrated by the following two examples. The I^st mix design is carried out carelessly, where as the 2^nd mix design is worked out taking into consideration all technical points. In both mix design examples the materials and requirements are same as given below:

1. Cement, PPC, 7-days strength 36.5 N/mm² and 28-days strength 46.8 N/mm². Specific gravity 3.0
2. Aggregates grading are as given below:

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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

A simple method of concrete mix design for pumpable concrete based on an estimated weight of the concrete per unit volume is described in the paper. The tables and figures presented are worked out by the author from a wide range of Indian materials. The method is suitable for normal weight concrete with admixture.

INTRODUCTION
Pumped concrete may be defined as concrete that is conveyed by pressure through either rigid pipe or flexible hose and discharged directly into the desired area. Pumping may be used for most all concrete construction, but is especially useful where space or access for construction equipment is limited.
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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

Concrete mix design is the process of choosing suitable ingredient of concrete and determining their relative quantities with the object of producing as economically as possible concrete of certain minimum properties, notable workability, strength and durability. It should be explained that an exact determination of mix proportions by means of table or computer data is generally not possible. The materials used are essentially variable and many of their properties cannot be assessed truly quantitatively. A Laboratory trial mix does not provide the final answer even when the moisture condition of aggregates are taken into account. Only a mix made and used on the site can guarantee that all properties of the concrete are satisfactory in every detail for the particular job in hand. In fact mix selection requires a knowledge of the properties of concrete and experimental data, and above all the experience of the expert who conduct the mix design. The selection of mix proportions is an art as much as a science. It is not enough to select a suitable concrete mix; it is also necessary to ensure a proper execution of all the operation involved in concreting. It cannot be stated too strongly that, competently used, concrete is a very successful construction material but, in the literal service of the word, concrete is not fool proof. The mix proportions once chosen, cannot expected to remain entirely immutable because the properties of the ingredients (cement, sand, aggregate, water and admixture) may vary from time to time.
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