CONCRETE MIX DESIGN

Mrinaljyoti Adhyapok

CONCRETE MIX DESIGN

Major Project Report submitted to

Sikkim Manipal University, Sikkim

Submitted in partial fulfillment of the requirements for the award of

the degree of

Bachelor of Technology

By

Mrinaljyoti Adhyapok

Under the guidance of

Mr. Abhranil Adak

DEPARTMENT OF CIVIL ENGINEERING

SIKKIM MANIPAL INSTITUTE OF TECHNOLOGY

MAJITAR, RANGPO, EAST SIKKIM 737136

MAY 2013

2013, Mrinaljyoti Adhyapok. All rights reserved.

DECLARATION

I certify that

a. The work contained in this report is original and has been done by me under the guidance of my supervisor(s).

b. The work has not been submitted to any other Institute for any degree or diploma. c. I have followed the guidelines provided by the Institute in preparing the report. d. I have conformed to the norms and guidelines given in the Ethical Code of Conduct of

the Institute.

e. Whenever I have used materials (data, theoretical analysis, figures, and text) from other sources, I have given due credit to them by citing them in the text of the thesis and giving

their details in the references.

Mrinaljyoti Adhyapok

ABSTRACT

In the following pages to follow an attempt is being made to bring forward a brief analysis about

the concrete mix designs of M30 and M40 concrete. Here an effort has been made to find out the

compressive strengths developed by both M30 and M40 concrete not only by its normal mix

design but also through addition of admixtures and fibres.

The theories presented here have been adopted from the study of various standard codes

available for the conduct of civil engineers. Any suggestions and queries regarding correction of

the theories as well as the numerical presentations are welcome.

Close care has been taken to present the design solution calculation to the nearest

possible decimal values and any error or misprint in the calculations may suitably be considered.

CHAPTER 1

INTRODUCTION

1.1 General

The process of selecting suitable ingredients of concrete and determining their relative amounts

with the objective of producing a concrete of the required strength, durability and workability as

economically as possible, is termed the concrete mix design. The proportioning of ingredients of

concrete is governed by the required performance of concrete in two states, namely the plastic

and the hardened state. If the plastic concrete is not workable it cannot be properly placed and

compacted. The property of workability therefore becomes of vital importance.

The compressive strength of hardened concrete which is generally considered to be an

index of other properties depends upon many factors, for example quality and quantity of

cement, water and aggregates, batching and mixing, placing, compaction and curing. The cost of

concrete is made up of the cost of materials, plant and labour. The variation in the cost of

materials arise from the fact that the cement is several times costly than the aggregate, thus the

aim is to produce as lean a mix as possible. From the technical point of view the rich mixes may

lead to high shrinkage and cracking in the structural concrete, and to evolution of high heat of

hydration in mass concrete which may cause cracking.

The actual cost of concrete is related to the cost of materials required for producing a

minimum mean strength called characteristic strength that is specified by the designer of the

structure. This depends on the quality control measures, but there is no doubt that the quality

control adds to the cost of concrete. The extent of quality control is often and economic

compromise, and depends on the size and types of job. The cost of labour depends on the

workability of the mix.

1.2 Scope of present work

The area of work that has been foreseen in this project is the study of strength of compacting

strength of concrete with the use of the aggregates easily available in this area. Focus has been

given only upon the general strength development of concrete mix design.

1.3 Objective of the present investigation

1. Concrete mix design of M30 and M40 concrete ( M30 and M40 has been selected

because through a general study it has been found out that these two mixes are generally

used in the Sikkim region).

2. Test of development of strength by the use of admixture, jute fibre and steel fibre along

with normal design mix of M30 and M40 concrete.

3. Taking all the results of the various design mixes and comparing their compressive

strength and economic possibilities.

CHAPTER 2

2.1 REQUIREMENTS OF CONCRETE MIX DESIGN

The requirements which form the basis of selection and proportioning of mix ingredients are:-

1. The minimum compressive strength required from structural consideration.

2. The adequate workability necessary for full compaction with the compacting equipment

available.

3. Maximum water cement ratio and/or maximum cement content to give adequate

durability for the particular site condition.

4. Maximum cement content to avoid shrinkage, cracking due to temperature cycle in mass

concrete.

2.2 FACTORS AFFECTING THE CHOICE OF MIX PROPORTION

1. Compressive strength

2. Workability

3. Durability

4. Maximum nominal size of aggregate

5. Grading and type of aggregate

6. Quality control

2.3 FACTORS TO BE CONSIDERED FOR MIX DESIGN

1. The grade designation giving the characteristic strength requirement of concrete.

2. The type of cement influences the rate of development of compressive strength of

concrete.

3. Maximum nominal size of aggregates to be used in concrete may be as large as possible

within the limits prescribed by IS 456-2000.

4. The cement content is to be limited from shrinkage, cracking and creep.

5. The workability of concrete for satisfactory placing and compaction is related to size and

shape of section, quantity and spacing of reinforcement and technique used for transportation,

placing and compaction.

2.4 METHODOLOGY AND PROCEDURE

Before performing the design calculations we have to perform the following standard tests.

1. Test for specific gravity of cement, fine aggregate and coarse aggregate.

2. Test for water absorption of coarse and fine aggregate.

3. Test for free moisture of coarse and fine aggregate.

4. Sieve analysis.

5. Compacting factor test.

2.4.1 Test for specific gravity of cement, fine aggregate and coarse aggregate

2.4.1.1 Test for specific gravity of cement

Apparatus: Specific gravity bottle, weighing balance

Procedure: Weigh a clean and dry specific gravity bottle with its stopper (w1). Place a sample of

cement upto half of a flask and weigh its stopper (w2). Add kerosene to the cement in the flask

till the graduated mark. Mix thoroughly with glass rod to remove entrapped air. Dry the outside

and weigh (w3). Empty the flask, clean it and refilled with clean kerosene up till the graduated

mark. Wipe dry the outside and weigh (w4).

Calculation:

Table 2.1: Showing values for calculating average specific gravity of cement

Weights Sample 1 Sample 2 Sample 3

Empty weight of

bottle, W1

0.031 0.030 0.030

Weight of bottle +

cement, W2

0.048 0.046 0.045

Weight of bottle +

cement + kerosene,

W3

0.083 0.082 0.082

Weight of bottle +

kerosene, W4

0.072 0.072 0.072

*weights are in kg(kilogram)

. =21

(41)(32)= 3.0997

= 3.1

2.4.1.2 Test for specific gravity of fine aggregate

Apparatus: Specific gravity bottle, weighing balance

Procedure: Weigh a clean and dry specific gravity bottle with its stopper (w1). Place a sample of

sand upto half of a flask and weigh its stopper (w2). Add water to the sand in the flask till the

graduated mark. Mix thoroughly with glass rod to remove entrapped air. Dry the outside and

weigh (w3). Empty the flask, clean it and refilled with clean water up till the graduated mark.

Wipe dry the outside and weigh (w4).

Calculation:

Table 2.2: Showing values for calculating average specific gravity of sand

Weights Sample 1 Sample 2 Sample 3

Empty weight of

bottle, W1

0.063 0.065 0.066

Weight of bottle

+ sand, W2

0.15 0.139 0.142

Weight of bottle

+ sand + water,

W3

0.24 0.236 0.232

Weight of bottle

+ water, W4

0.186 0.188 0.185

*weights are in kg(kilogram)

. =21

(41)(32)= 2.68

= 2.68

2.4.1.3 Test for specific gravity of coarse aggregate

Apparatus: conical flask, weighing balance

Procedure: Weigh a clean and dry conical flask with its stopper (w1). Place a sample of coarse

aggregate upto half of a flask and weigh its stopper (w2). Add water to conical flask in the flask

till the graduated mark. Mix thoroughly with glass rod to remove entrapped air. Dry the outside

and weigh (w3). Empty the flask, clean it and refilled with clean water up till the graduated

mark. Wipe dry the outside and weigh (w4).

Calculation: