MASS CONCRETE - Concrete •Introduction •What is it? •Why is it a concern? •How do we know we have mass concrete? •What can be done? •What controls

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  • MASS CONCRETE

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    2

    Introduction

    Craig Knapp, SBE Division of Engineering Services,

    Concrete Committee Chair

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    3

    Introduction What is it? Why we care? How we know? What can be done? What is necessary? Did it work?

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    4

    What Is It? ACI 207.1 definition of mass

    concrete, Any large volume of cast in place concrete with dimensions large enough to require that measures be taken to cope with generation of heat and attendant volume change to minimize cracking.

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    5

    Why Is It a Concern Delayed Ettringite

    Formation (DEF) Results in high

    sulfate concentration in the pore liquid. Sulfate has

    expansive reaction with calcium- and aluminium-

    http://upload.wikimedia.org/wikipedia/commons/a/a1/Ettringite-24339.jpghttp://upload.wikimedia.org/wikipedia/commons/a/a1/Ettringite-24339.jpg

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    6

    Why Is It a Concern Self-desiccation Self-drying Resulting in

    Impeded hydration

    Voids Increased

    shrinkage Lower ultimate

    strengths

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    7

    Why Is It a Concern Thermal cracking Caused by excessive temperature

    differential Increase permeability

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    8

    How Do We Know?

    Standard SpecsCast-in-place Piles8ft Dia and Greater

    Special ProvisionsGenerally smallest dimension

    exceeding 7ft

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    9

    How Do We Know?

    Other risk factors need to be considered High ambient temperature Higher cement content Lightweight Concrete Long haul times Etc.

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    10

    What Can Be Done?

    Controls Passive

    Active

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    11

    Passive Controls Actions taken before placement

    Includes

    Use of SCMs

    Low CTE Aggregate

    Lowering initial concrete temp

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    12

    Passive Controls Use of FA and

    GGBS 60%-75%

    High performance SCMs like Silica Fume and Metakaolin do not substantially lower heat of hydration

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    13

    Passive Controls Lower Placement

    Temp. Ambient Concrete

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    14

    Active Controls Actions taken after concrete is

    placed. Includes Cooling the surface

    Insulating the surface

    Cooling pipes

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    Cooling Tubes

    15

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    16

    What Is Necessary?

    IT DEPENDS Max temp 160 deg F No crack parameter

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    What Is Necessary? Thermal Control Plan Includes Calculations showing

    Hottest point in the mass Maximum allowable temp differential

    Mix design Curing method and duration Peak and differential temperature

    controls

    17

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    18

    Did it Work? Temperature monitoring and

    recording. Included in the thermal control plan Monitoring

    Hottest calculated point At least two

    Outer faces Top surface Two corners

    Recording Hourly Stop when core temp starts to drop.

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    19

    Summary 160 deg F max is the Departments

    determination acceptable risk. There are a multitude of factors that

    impact concrete temperature during hydration. Many ways to mitigate.

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    20

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    21

    What Is It?

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    22

    What Is It?

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    23

    What Is It?

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    What Is It?

    Deck thickness 10 Stem thickness 1 10 Lightweight Concrete 980lb/cy 5% Flyash

    24

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    25

    What Is It? Benicia martinez superstructure

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    What Is It? Specific heat The amount of heat required to raise

    1 gram of material 1 degree.

    Coarse aggregates SHlightweight = SHnormal weight Total mass of concrete reduced 15% Peak Temperature increased 15%

    26

  • Mass Concrete

    Introduction

    What is it?

    Why is it a concern?

    How do we know we have mass concrete?

    What can be done?

    What controls are necessary?

    How do you know they work?

    Cooling Tubes

    27

    Slide Number 1IntroductionIntroductionWhat Is It?Why Is It a ConcernWhy Is It a ConcernWhy Is It a ConcernHow Do We Know?How Do We Know?What Can Be Done?Passive ControlsPassive ControlsPassive ControlsActive ControlsCooling TubesWhat Is Necessary?What Is Necessary?Did it Work?SummarySlide Number 20What Is It?What Is It?What Is It?What Is It?What Is It?What Is It?Cooling Tubes