Properties of concrete

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Properties of concrete

• Topic MIX DESIGN OF CONCRETE

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Properties of concrete

• Submitted To
• DR. AYUB ELAHI
• Submitted By
• SOHAIB NASEER
  2K9-scet-29/CIVIL
• M.ZAEEM FAKHAR 2K9-scet-03/CIVIL
• ISRARULHAQ
  2K9-scet-30/CIVIL
• AWAIS ULLAH
  2K9-scet-31/CIVIL
• BILAL RIAZ
  2K9-scet-59/CIVIL

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INTRODUCTION

• Concrete is the second largest material consumed
  by human beings after food and water as per WHO.
  It is obtained by mixing cement, fine aggregate,
  coarse aggregate and water in required
  proportions. The mixture when placed in forms and
  allowed to cure becomes hard like stone. The
  hardening is caused by chemical action between
  water and the cement due to which concrete grows
  stronger with age.

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INTRODUCTION

• The strength, durability and other
  characteristics of concrete depend upon the
  properties of its ingredients, proportion of the
  mix, the method of compaction and other controls
  during placing, compaction and curing.

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Definition

• the process of selecting suitable ingredients of
  concrete and determining their relative
  proportions with the object of producing
  concrete of certain minimum strength and
  durability as economically as possible

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Objective In Designing Concrete Mixtures

• To determine the most economical practical
  combination of readily available materials to
  produce a concrete that will satisfy the
  performance requirements under particular
  conditions of use

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Designing Concrete MixturesFactors to be
considered

• Workability
• Placement conditions
• Strength
• Durability
• Appearance
• Economy

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Factors to be considered

• Strength important to the design engineer
• Durability important to the owner
• Workability important to the contractor
• Economy important to the owner
• Proportioning concrete is the art of optimizing
  the mixture to meet these requirements

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Methods Of Selection Of Mix Proportions

• There are two main methods for the selection of
  mix proportions of concrete.
• American method
• British method

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Steps For Mix DesigningACI METHOD

• Choice of slump
• Choice of max. Size of aggregates
• Estimate of water and air contents
• Selection of water cement ratio
• Calculation of cement contents
• Estimate of coarse aggregates content
• Estimate of fine aggregates content
• Adjustments to mix proportion

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Steps For Mix DesigningBRITISH METHOD

• Determining the Free Water/ Cement Ratio
• Determining the Free-water Content
• Determining the Cement Content
• Determining the Total Aggregate Content
• Determining of The Fine and Coarse
• Aggregate Contents

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Coarse Aggregate Requirement

• Grading
• Nature of particles
• Shape
• Porosity
• Surface texture

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Max Aggregate Size

• Cover between steel form, C Dmax lt3/4C
• Spacing between bars, S Dmax lt3/4S
• Depth of slab, D Dmax ltD/3

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Max Aggregate Size(For pumped concrete)

• Dmax lt 1/3 diameter of
• hose or 1-1/2 inch,
• whichever is smaller

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Fineness Modulus of Sand

• The FM is calculated from
• particle size distribution of
• the sand
• Values should range
• between 2.3 to 3.1
• Coarse sand has a higher
• FM than fine sand
• FM influences the bulk
• volume of coarse aggregate

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Air ContentThe amount needed depends on

• Max aggregate size
• Less paste as size
• increases

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Workability Requirements

• Concrete must always be
• made with a workability,
• consistency and plasticity
• suitable for job placement

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Workability Requirements
Concrete Construction Slump Maximum Slump Minimum
Reinforced walls footings 3 1
Plain footings, caissons, and Substructure walls 3 1
Beams reinforced walls 4 1
Columns 4 1
Pavements and slabs 3 1
Mass concrete 3 1
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Water cement ratio

• Range of w/c 0.45 to 0.65
• For mix design of
• 124
• The w/c is standardized as 0.5

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Water ContentWater demand is influenced by

• Slump requirement
• Aggregate size
• Aggregate shape
• Air content
• Cementing materials content
• Temp
• Admixtures

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Water Contents
Slump mm Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate
Slump mm 9.5 12.5 19 25 37.5 50 75 150
Non-air entrained concret
25 to 50 207 199 190 179 166 154 130 113
75 to 1oo 228 216 205 193 181 169 145 124
150 to 175 243 228 216 202 190 178 160 -
Amount of air entrapped 3 2.5 2 1.5 1 0.5 0.3 0.2

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Cement ContentCement Material Content Water
Content W/CM

• Minimum cement content may be
• specified for the purpose of
• Durability
• Finishability
• Wear resistance
• Appearance
• Excessively high cementitious contents
• should be avoided for
• Economy
• Avoid adverse effects
• Workability
• Shrinkage
• Heat of hydration