The Indian standard IS:456-2000 recommends the use of Portland pozzolana cement (blended cement) as well as mineral admixtures for concrete mixes provided that there are satisfactory data on their suitability, such as performance test on concrete containing them. In the present paper concrete mix design with blended cement is presented based on relevant latest I.S. codes.

Dr. S. K. Dubey, Professor (structures), Deptt. of Civil Engineering., M.A.N.I.T., Bhopal

Introduction

Concrete is a widely used structural material consisting essentially of a binder and a mineral filler. It has the unique distinction of being the only construction material actually manufactured on the site, or in a RMC plant whereas other materials are merely shaped to use at the worksite.

Concrete has become an indispensable construction material. In the present scenario concrete has crossed the stage of four component system i.e. cement, water, coarse aggregate and fine aggregate. It can be combination of more number of ingredients such as fly ash, ground granulated blast furnace slag, silica fume, rice husk ash and admixtures etc. are generally used in concrete production in practice which depends upon the requirement and the availability of the expertise.

The fundamental requirement of a concrete mix is that it should be satisfactory both in the fresh as well as in the hardened state, possessing certain minimum desirable properties like workability, strength and durability. Besides these requirements it is essential that the concrete mix is prepared as economically as possible by using the least possible amount of cement content per unit volume of concrete, with due regard to the strength and durability requirements. Since concrete is produced by mixing several discrete material, the number of variables governing the choice of mix design are necessarily large. However continuous research work in this field by various investigators, has helped to identify the major parameters controlling the proportions of ingredients in the mix.

Principle of Mix Design

The basic principle which is generally used for mix design for proportioning mixes is Abram's law for strength development. According to this law, for any given conditions of test the strength of workable concrete mix is dependant only on the water-cement ratio. Lesser the water-cement ratio in a workable mix greater will be its strength. From practical considerations compressive strength is taken as an index of acceptability. Mix proportioning is normally carried out for a specific characteristic compressive strength requirements ensuring that the mix so proportioned should satisfy the workability requirements without segregation and bleeding of concrete.

Data For Mix Design

The following data are required for mix design:
  • Grade designation
  • Type of cement
  • Maximum nominal size of aggregate
  • Minimum cement content
  • Maximum water-cement ratio
  • Workability
  • Maximum cement content
  • Any admixture used
  • Exposure conditions (as per IS: 456)
  • Method of transportation and placing of concrete

Mix Design Procedure

    • Target mean strength

      F
t
      = f
ck
      + 1.65 × S


      Where,


      F
t
      = Target mean strength at 28 days in N/mm
2

      f
ck
      = Characteristic compressive strength at 28 days in N/mm
2

      S = Standard deviation


    • Selection of water-cement ratio

Table 3: Environmental Exposure Conditions (Clauses 8.2.1 and 35.3.2
SI. No. Environment Exposure Conditions
i) Mild Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal area.
ii) Moderate Concrete surfaces sheltered from severe rain or freezing whilst wet Concrete exposed to condensation and rain Concrete continuously under water Concrete in contact or buried under non-aggressive soil/ground water Concrete surfaces sheltered from saturated salt air in coastal area
iii) Severe Concrete surfaces, exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or severe condensation.
Concrete completely immersed in sea water Concrete exposed to coastal environment
iv) Very severe Concrete surfaces exposed to sea water spray, corrosive fumes or severe freezing conditions whilst wet Concrete in contact with or buried under aggressive sub-soil/ground water
v) Extreme Surface of members in tidal zone Members in direct contact with liquid/solid aggressive chemicals

      This ratio should be selected based upon the relationship between target mean compressive strength of concrete and Compressive strength of cement. IS: 10262-1982 fig. 2 gives the values of water-cement ratio for various cements. The water-cement ratio can also be taken from table (5) of IS:456-2000 for particular environmental exposure conditions as starting point. The supplementary cementitious material that is mineral admixtures shall also be considered in water-cement ratio calculations.


      The above selected water-cement ratio should be checked against limiting water–cement ratio for the requirement s of durability and the lower of the two will be adopted.


Table 5: Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregates of 20 mm Nominal Maximum Size
Clauses 6.1.2, 8.2.4.1 and 9.1.2)
SI. No. Exposure Plain Concrete Reinforced Concrete
Minimum Cement Content kg/m3 Maximum Free Water-cement Ratio Minimum Grade of Conrete Minimum Cement Content kg/m3 Maximum Free Water-cement Ratio Minimum Grade of Conrete
(1) (2) (3) (4) (5) (6) (7) (8)
i) Mild 220 0.60 - 300 0.55 M 20
ii) Moderate 240 0.60 M 15 300 0.50 M 25
iii) Severe 250 0.50 M 20 320 0.45 M 30
iv) Very severe 260 0.45 M 20 340 0.45 M 35
v) Extreme 280 0.40 M 25 360 0.40 M 40
Notes
1. Cement content prescribed in this table is irrespective of the grades of cement and it is inclusive of additions mentioned in 5.2. The additions such as fly ash or ground granulated blast furnace slag may be taken into account in the concrete composition with respect to the cement content and water-cement ratio if the suitability is established and as long as the maximum amounts taken into account do not exceed the limit of pozzolona and slag specified in IS 1489 (Part 1) and IS 455 respectively.

2. Minimum grade for plain concrete under mild exposure condition is not specified.

    • Selection of water content

      The water content i.e. the quantity of maximum mixing water per unit volume of concrete may be determined from the following table:

      Table: Maximum water content per cubic meter of concrete
      S.No. Nominal maximum size of agg. Maximum water content
      1. 10 mm 208 kg
      2. 20 mm 186 kg
      3. 40 mm 165 kg
      The above table is for angular coarse aggregates and for 25 to 50mm slump range.

      Note:
      • The water estimates can be reduced by approximately 10 kg for sub-angular aggregates, 20 kg for gravel with some crushed particles & 25 kg for rounded gravel to produce same workability.
      • For desired workability (other than 25 to 50mm slump range) the required water content may be increased by about 3 percent for every additional 25mm slump or alternatively by use of chemical admixtures.
      • Water reducing admixtures usually decrease water content by 5 to 10 percent and 20 percent and above respectively at appropriate dosages.

    • Cementitious material content

      This may be calculated from the free water-cement ratio and the quantity of water per unit volume of concrete. The cementitious material content so calculated shall be checked for minimum content for the durability requirements and the greater of the two values adopted. The maximum cement content shall be as per IS: 456-2000.


    • Proportioning of coarse aggregate content

      For a water-cement ratio of 0.5 approximate values of aggregate volume is given in the following table.
      Table: Volume of coarse aggregate per unit volume of total Aggregate for different Zones of Fine Aggregate
      S, No. Nominal Maximum Size of Aggregate Volume of Coarse Aggregate* per unit Volume of Total Aggregate for Different Zones of Fine Aggregate
        mm Zone IV Zone III Zone II Zone I
      1 2 3 4 5 6
      i) 10 0.50 0.48 0.46 0.44
      ii) 20 0.66 0.64 0.62 0.6
      iii) 40 0.75 0.73 0.71 0.69
      *Volumes are based on aggregates in saturated surface dry condition.

      Note:
      • Adjust volume of coarse aggregate for decrease in w/c ratio by 0.05 the increase in coarse aggregate by 1%.
      • For more workable concrete such as pumped concrete etc the above estimated coarse aggregate content may be reduced by up to 10%.

    • Determination of Fine Aggregate Content:

      This is obtained by finding out the absolute volume of cementitious material; water and the chemical admixture by dividing their masses to their specific gravity, multiplying by 1/1000 subtract the results of this summation from unit volume.


      The above obtained values are distributed into coarse and fine aggregate fractions by volume in accordance with coarse aggregate fractions.


      The coarse and fine aggregates contents are then determined by multiplying with their respective specific gravities and multiplying by 1000.


    • Trial Mixes

      The trial mixes shall be made and cubes be tested, if any discrepancies may be observed during concrete making it should be taken into considerations and more trial mixes be prepared and finally the mix which provides sufficient information, including the relationship between compressive strength, water cement ratio and slump, from which the mix proportions for field trials may be arrived at. The concrete for field trials shall be produced by methods of actual concrete production.


    • Example

Grade of Designation M-25
Type of Cement PPC confirming to Is1489 – Part I
Maximum Nominal Size of Aggregate 20 mm
Minimum Cement Content 300 kg
Maximum water cement ratio 0.5
Workability 60 mm slump
Type of Aggregate Crushed Angular aggregate
Maximum Cement Content 450 kg/m3
Chemical Admixtures Fosroc (as supplied)

Sieve Analysis of Coarse Aggregate
IS sieve No Analysis of Coarse Aggregate Fraction, % passing Percentage of Different Fractions Remarks
  I II I II Combined  
      30% 70% 100%  
20mm 81 100 24.3 70 94.3 Conforming to Table: 2 of IS383
10mm 0.8 47 .24 32.9 33.14
4.75mm 0 4.4 0 3.08 3.08  
2.36mm - - - - -  

IS sieve No Percentage passing Remarks
4.75mm 100 Conforming to Zone IV Table 4 of IS383
2.36mm 98.5
1.18mm 96
600 µm 85  
300 µm 3  
150 µm 0  

      Target Mean Strength F
t
      = f
ck
      + 1.65 S


      = 25 + 1.65 * 4.0


      = 31.6 N/mm
2

      The mix proportions obtained for above materials are:


      Water : Cement : Sand : Aggregate = 184.5 lits: 410 kg: 606 kg : 1176 kg


      w/c ratio = 0.45, 1 : 1.478 : 2.868


      Admixture dose = 0.25 % of weight of cement in terms of volume of admixture.


      Cube strength after 7 days = 24.0 N/mm
2
      , 20.88 N/mm
2
      , 22.22 N/mm
2

      Average Value = 22.36 N/mm
2

      Cube strength after 28 days = 31.11 N/mm
2
      , 34.66 N/mm
2
      , 31.11 N/mm
2

      Average Value = 32.29 N/mm
2

Conclusions

The concrete mix produced with blended cements (PPC Cement) possesses nearly same quality as of OPC except with adjustments in water cement ratio as such the heat of hydration of PPC is lower than OPC the cement content obtained is slightly higher for blended cements. Hence, it is concluded that with proper quality control and supervision at site, the effectiveness of concrete produced with blended cements will be increased. It will also satisfy the requirements of workability, strength and durability.

References

  • IS:456-2000 (fourth revision)code of practice for plain and reinforced concrete structures, BIS New Delhi
  • IS:10262-1982, Recommended guideline for conc. mix design, BIS, Feb 1983 , BIS New Delhi.
  • IS:10262-2009, Concrete mix proportioning – Guide lines July, 2009 , BIS New Delhi.
  • IS:383 – 1970, Specification for coarse and Fine aggregates from natural sources for concrete BIS New Delhi.
  • Shetty, M. S., Concrete Technology Theory and Practice, 2005, S Chand & Co. New Delhi.
  • Roy Sabyasachi, Pumped concrete with admixtures, Civil Engineering & Construction Review, 2004 pp 51-54.
  • N. Krishnaraju, Design of Concrete Mixes, CBS publishers, Delhi, 1993
.
Finnish company Betolar expands to Indian concrete markets with a cement-free concrete solution
Betolar, a Finnish start-up, and innovator of geopolymer concrete solution Geoprime®, has expanded its operations to Europe and Asian markets including India, Vietnam and Indonesia. Betolar’s innovation Geoprime® is the next-generation, low carbon

Read more ...

Why Fly Ash Bricks Are Better Than Clay/Red Bricks
It is estimated that in India each million clay bricks consume about 200 tons of coal and emit around 270 tons of CO2; on the other hand, with fly ash bricks production in an energy-free route, there are no emissions. Dr. N. Subramanian, Consulting

Read more ...

Low Fines, Low Viscosity, Self-Consolidating Concrete for Better Impact on CO2 Emissions
Production of low fines SCC with increased robustness in a highly flowable, less viscous condition meeting true SCC specifications is now a reality to help realise the architect’s and engineer’s dream of various complex profiles and shapes in

Read more ...

Methods & Factors for Design of Slabs-on-Grade
Sunitha K Nayar, gives the grouping of slabs-on-grade based on the design philosophies and a brief overview of the different design methods, the commonalities between design strategies in terms of the input parameters, assumed and estimated parameters, and the

Read more ...

FIBERCRETE®: Synthetic Fibers for Concrete Reinforcement
Kalyani Polymers is offering world-class made-in-India Synthetic Micro & Macro Concrete Fiber Products for the Construction Industry under the brand name FIBERCRETE®. Concrete is an integral part of any construction project, it can be roads, tall structures

Read more ...

Climate Control Concrete
Leading cement and concrete maker ACC has unveiled a revolutionary thermal insulating climate control concrete system in India. Sridhar Balakrishnan, MD & CEO, ACC Limited, discusses its attributes, applications, and benefits for home builders, architects

Read more ...

Innovations in Crack Bridging with Self-Healing Bacteria in Concrete
Dr. Manjunatha L R, Vice President - Direct Sales & Sustainability Initiatives, and Raghavendra, Senior officer, JSW Cement Limited, discuss bacterial concrete that can meet the requirements for strength, durability, and self-healing of cracks.

Read more ...

Sustainable Development Through Use of Self-Curing Concrete
Dada S. Patil, Assistant Professor, Civil Engineering Department, AIKTC, Panvel, Navi Mumbai, Maharashtra; Dr. S. B. Anadinni, Professor & Associate Dean (Core Branches), School of Engineering, Presidency University, Bengaluru; and Dr. A. V. Shivapur, Professor

Read more ...

Developing a Corrosion Resistant RCC Structure
Samir Surlaker, Director, Assess Build Chem Private Limited, emphasizes the importance of a clear cover for a concrete structure since concrete as a porous material needs protection of its reinforcement. Along with the thickness (quantity) of cover, the porosity of

Read more ...

Quest for Higher Strength Concrete From HSC to UHPC
Concrete technology has come a long way since the Romans discovered the material, with a number of ingredients, which include a host of mineral and chemical admixtures, besides of course, the Portland cement, aggregates (coarse and fine), and water. These ingredients

Read more ...

Modelling Methods for Protection of RCC Structures
Anil Kumar Pillai, GM, Ramco Cements, discusses two major softwares (Life 365 and DuraCrete), used in the industry for protection of RCC structures. The common design approach is faulty because we consider only the loading aspect, whereas the environmental aspect is equally

Read more ...

Bajaj Reinforcements LLP - Introduces Fibre Tuff heavy-duty synthetic fibres that offer a range of benefits to concrete
Fibre Tuff, macro synthetic polypropylene fibres, are heavy-duty synthetic fibres that are specially engineered for use as secondary reinforcements, providing excellent resistance to the post cracking capacity of concrete. They are replacing steel fibres in a range

Read more ...

Use of Headed Bars in Reinforced Concrete Design
Reinforced concrete design and construction practice has historically focused on the use of bonded straight or bend rebar as a method for rebar anchorage. This relies on bond integrity between the rebar and the concrete so that sufficient anchorage

Read more ...

Innovation easy, effective and economical tool for asset creation
Innovation and entrepreneurship are essential ingredients in building a successful commercial venture. The ways in which these two concepts fuel enterprise are something entrepreneur's never stop exploring. There is no doubt that innovation were

Read more ...

Reactivity of Alite and Belite towards Sustainability of Concrete
Alite and belite are the predominant phases of Portland cement formulation. Alite is impure tricalcium silicate (C3S) and belite is impure dicalcium silicate (C2S). The impurities are an integral part as cement is manufactured

Read more ...

Innovative, Economic, Durable and Sustainable Concrete to last for +100 years of service life
Concrete is a versatile construction material and day by day its consumption is increasing globally. It is second only to water in the global consumption. No civil engineering structure is feasible without using concrete

Read more ...

Nanospan India Pvt Ltd
The use of Graphene with concrete has been talked about and researched ever since Graphene was invented in 2010 which grabbed its inventors a Nobel prize. Nanospan is the first company in the world to break technological and commercial

Read more ...

Fosroc: Building, Cementing & Supporting
Fosroc is the foundation of the JMH Group. It employs over 1700 employees in 17 operating companies based in Europe, the Gulf & Middle East, India, South Asia, and China. Through FGT, its trading company, it services another 50 countries

Read more ...

Dextra Group
Established in 1983 by French expatriate entrepreneurs, the Dextra Group has a long history of growth and development, driven by strong entrepreneurship and innovation. It has diversified into three main activities: manufacturing, trading and freight forwarding

Read more ...

Ferrochrome Ash Based Geopolymer Concrete
Jyotirmoy Mishra, Ph.D. Scholar, Department of Civil Engineering, Veer Surendra Sai University of Technology, Burla, Odisha, presents his research on the feasibility and compressive strength performance of geopolymer concrete

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.
Click here to subscribe.
×