Transcript Properties of concrete - Swedish College Of Engineering

Topic : MIX DESIGN OF CONCRETE
Properties of concrete
Submitted To:
DR. AYUB ELAHI
Submitted By:
SOHAIB NASEER
M.ZAEEM FAKHAR
ISRAR–UL–HAQ
AWAIS ULLAH
BILAL RIAZ
2K9-scet-29/CIVIL
2K9-scet-03/CIVIL
2K9-scet-30/CIVIL
2K9-scet-31/CIVIL
2K9-scet-59/CIVIL
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.
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.
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
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
Designing Concrete Mixtures
Factors to be considered
 •Workability
 •Placement conditions
 •Strength
 •Durability
 •Appearance
 •Economy
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
Methods Of Selection Of Mix
Proportions
 There are two main methods for the selection of mix
proportions of concrete.
 American method
 British method
Steps For Mix Designing
ACI
1.
2.
3.
4.
5.
6.
7.
8.
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
Steps For Mix Designing
BRITISH
1.
2.
3.
4.
5.
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
Coarse Aggregate Requirement
 Grading
 •Nature of particles
–Shape
–Porosity
–Surface texture
Max Aggregate Size
 Cover between steel & form, C: Dmax <3/4C
 Spacing between bars, S: Dmax <3/4S
 Depth of slab, D: Dmax <D/3
Max Aggregate Size
(For pumped concrete)
 Dmax < 1/3 diameter of
hose or 1-1/2 inch,
whichever is smaller
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
Air Content
The amount needed depends on:
 Max aggregate size
–Less paste as size
increases
Workability Requirements
 Concrete must always be
made with a workability,
consistency and plasticity
suitable for job placement
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
Water cement ratio
 Range of w/c= 0.45 to 0.65
 For mix design of
 1:2:4
 The w/c is standardized as 0.5
Water Content
Water demand is influenced by:
 Slump requirement
 Aggregate size
 Aggregate shape
 Air content
 Cementing materials content
 Temp
 Admixtures
Water Contents
Slump
mm
Water. Kg/m3 of concrete for idicated nominal maximum size of aggregate
9.5
12.5
19
25
37.5
50
75
150
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
Non-air
entrained
concret
Cement Content
Cement 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