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Hot Weather Concrete ACI 305

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What is Hot Weather Concreting? ... Hot weather is any combination of the above which impair quality of fresh or ... with satisfactory records in hot weather ... – PowerPoint PPT presentation

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Title: Hot Weather Concrete ACI 305


1
Hot Weather ConcreteACI 305
  • Joseph E. Diedrich
  • Technical Service Manager
  • Southdown, Inc.

2
What is Hot Weather Concreting?
  • When concrete is mixed, transported, and place
    under conditions of high ambient temperature, low
    humidity, solar radiation, or wind, an
    understanding of the effects there environmental
    factors have on concrete properties and
    construction operations is required (ACI 305).

3
Introduction
  • Often specifiers establish a maximum as placed
    concrete temperature in an attempt to control
    strength, durability, plastic shrinkage, thermal,
    and drying shrinkage cracking.
  • Concrete durability is a general term that is
    difficult to quantify, but it is perceived to
    mean resistance of the concrete to weathering.

4
General
  • Initial curing of concrete test specimens for
    checking adequacy of mix for strength or basis of
    acceptance are cured initially at 60 to 80F
    (16 to 27C), ASTM C31
  • 24hr cure at 100F, 28 day may be 10 to 15
    percent lower than cured ASTM C31
  • drying at early age, strengths will be reduced
    even further

5
Definition of Hot Weather
  • High ambient temperature
  • High concrete temperature
  • Low relative humidity
  • Wind velocity
  • Solar radiation
  • Hot weather is any combination of the above which
    impair quality of fresh or hardened concrete
    and/or cause detrimental results

6
Hot Weather
  • Hot weather concrete problems generally occur
    during the summer season
  • Thermal shrinkage is more severe in the spring
    and fall (temperature differential)
  • When air temperatures are identical, a calm,
    humid day is less severe than a dry, windy, sunny
    day

7
Potential Problems in Hot Weather - Plastic
Concrete
  • Increased water demand
  • Increased rate of slump loss, tendency to add
    water at the jobsite
  • increased rate of setting, resulting in difficult
    handling, finishing, and risk of cold joint
  • Increase for plastic shrinkage
  • Increased difficulty in controlling entrained air
    content.

8
Potential Problems in Hot Weather - Hardened
Concrete
  • Decreased 28 day and later strengths, higher
    water demand, concrete temperatures
  • Increase for drying shrinkage and thermal
    cracking
  • Decreased durability from cracking
  • Increased permeability
  • Increased potential for reinforcing steel
    corrosion due to increased cracking

9
Avoiding Potential Problems
  • Use concrete materials and proportions with
    satisfactory records in hot weather
  • Use cool concrete
  • Use a concrete consistency that permits rapid
    placement and effective consolidation
  • Transport, place, consolidate, and finish with
    least delay
  • Protect concrete against moisture loss at all
    times, during placement and curing period

10
Curing Temperature Relationship
11
(No Transcript)
12
Water Vs. Temperature
13
Temp, Slump, Water Demand
14
Questions?
  • Remember
  • Use Common Sense
  • Temperature effects on your body have very
    similar effects on concrete
  • If you are not sure, ASK!!!
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