Mixing and Testing CE 331 Engineering Materials II Slides developed - - PowerPoint PPT Presentation

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Mixing and Testing CE 331 Engineering Materials II Slides developed - - PowerPoint PPT Presentation

Oct 16, 2023 246 likes •601 views

Concrete: Mixing and Testing CE 331 Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 1 of 35 Objectives Learn the ASTM Standard for hand mixing Understanding the time dependency of concrete properties

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 1 of 35

Concrete: Mixing and Testing

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Objectives

  • Learn the ASTM Standard for hand mixing
  • Understanding the time dependency of concrete

properties

  • Learn how to conduct the mechanical and durability

testing

  • Learn the effects of fly ash
  • Effects
  • f

w/c

  • n

workability, electrical measurements, and strength

  • Learn the principles of isothermal calorimeter testing
  • Learn an application of Power’s Gel Space Ratio

Theory

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 3 of 35

Outline

  • Mixtures
  • Sample Preparation
  • Mixing & Placement
  • Conditioning
  • Hardened Testing Procedures
  • Calorimetry Testing
  • Powers Model
  • Report
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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 4 of 35

Mixtures

w/c=0.36 w/c=0.36, 40 % Fly Ash w/c = 0.3 w/c=0.3 w/o WRA w/c=0.36 w/c=0.42 w/c=0.6

We will distribute the data for these mixtures You will make these mixtures in the lab

Mixtures are 30% fine aggregate, 30% coarse aggregate by volume There will be a water reducing admixture as well

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 5 of 35

Materials

Abs = 1.8 % Abs = 0.8 % We will use oven dry aggregate and increase the mix water to correct for absorption

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 6 of 35

Prepare a label with your lab section and mixture number

Sample Preparation

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  • 1. Assemble Mixing Equipment

Mixing Procedure

We will be utilizing the hand-mixing procedure described in ASTM C192

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  • 2. Measure materials with the mixture design your

group is given in class.

  • 3. Mix cement and fine aggregate

Mixing Procedure

We will be utilizing the hand-mixing procedure described in ASTM C192

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 9 of 35

  • 4. Mix in the coarse aggregate
  • 5. Slowly mix in the water and chemical admixtures

Mixing Procedure

We will be utilizing the hand-mixing procedure described in ASTM C192

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 10 of 35

Placing Procedure

  • Fill your 3x6 cylinders in 3 equal layers, rod each 25

times

  • Each group should make

3— 3x6s

  • Clean and dispose of excess materials
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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 11 of 35

Compression Testing w/ Friction

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Compression Testing w/o Friction

We will use neoprene caps smooth the ends and ensure uniform stress

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Compression Testing

Forney 700 kip compression machine in Pankow Laboratory

𝒈𝒅

′ = 𝐐

𝐁

A is cross-sectional area We are using a 3” diameter cylinder

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 14 of 35

An upcoming and popular rapid test to give an indication of durability

Electrical Resistivity Testing

𝝇 = 𝐒𝐥

Electrical Resistivity Resistance (measured in lab) Geometry Factor (A/L)

This is 𝐒!

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 15 of 35

Electrical Resistivity

Resistivity is a measure

  • f

electrical resistance independent of geometry, units of ohm-m (Ω ∙ m) Concrete is a porous composite

  • Solid Phase (reactancts, products, and aggregates)

𝜍𝑡𝑝𝑚𝑗𝑒𝑡 ≈ 109 Ω ∙ m

  • Vapor Phase

𝜍𝑤𝑏𝑞𝑝𝑠 ≈ 1015 Ω ∙ m

  • Liquid Phase (pore solution)

𝜍𝑚𝑗𝑟𝑣𝑗𝑒 < 1 Ω ∙ m

Weiss (‘05), Rajabipour (‘06)

Electricity is conducted primarily through the liquid

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 16 of 35

Electrical Resistivity

Weiss (‘05), Rajabipour (‘06)

These parameters can be used to quantify the durability of a mixture

𝝇 = 𝝇𝟏 𝟐 𝝔𝜸 = 𝝇𝒑𝐆

𝝇𝒄𝒗𝒎𝒍: resistivity (easily measured) 𝝇𝟏: pore solution (model/experimental data) 𝝔: liquid volume fraction 𝜸: connectivity(related to pore distribution) 𝐆: Formation Factor

These tests are highly dependent on moisture content and temperature!

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 17 of 35

D = 1 𝐺 ∙ 𝑑𝑝𝑜𝑡𝑢𝑏𝑜𝑢

Formation Factor

Reinforcing Bar Deicing Salt Cover Deicing salts -> pavements and bridge decks Salt (Cl-) and steel = corrosion

We need to know how the Cl- moves through the concrete

Main parameter is the “Diffusion Coefficient” which describes the speed Nernst-Einstein

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 18 of 35

Formation Factor

The diffusion coefficient can be used to estimate the time to reach a critical concentration level 𝐷𝑦,𝑢: 𝐷𝑦,𝑢 − 𝐷𝑝 𝐷𝑡 − 𝐷𝑝 = 1 − erf 𝑦 2 𝐸𝑢

(with a few assumptions that you will discuss later in the semester)

Steel depassivation and corrosion can begin when this reaches a critical level

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 19 of 35

Cement hydration

Cement hydration is an exothermic reaction.

CE530 slides

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Five stages in cement hydration by heat

CE 530 slides

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Isothermal calorimetry

  • A good method for the study of cement hydration process.
  • Relevant standards include ASTM C186 and ASTM C1702
  • Widely used for studying the reaction kinetics of pure cement

pastes as well as the temperature dependence of the reaction.

  • Degree of hydration can be determined by calorimetry.
  • Q(max) is determined from the chemical composition of the

materials For the raw materials in this lab: Q(max) cement: 512 J/g cement

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Heat flow and cumulative heat

In general one test generates two plots: heat flow and cumulative heat. They are intrinsically the same data. Cumulative heat is an integral of heat flow on time.

50 100 150 200 250 300 50 100 150 200 Cumulative Heat (J/g) Age (hour) 0.5 1 1.5 2 2.5 3 50 100 150 200 Heat flow (mw/g) Age (hour)

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8 samples in total

TAM air

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Ampoules

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A simple yet effective model that can be used to describe the microstructure of hydrating cement Inputs

water-cement ratio (𝑥/𝑑) degree of hydration (𝛽)

Powers Model

This is an example for a w/c=0.5

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You can program the equations or use spreadsheet on website

Powers Model - Calculations

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Report

  • Three weeks of lab work will be in this report
  • Worth twice as much as previous write-ups
  • Sections

– Executive Summary (15 %) – Introduction and Background (10 %) – Materials and Methods (10 %) – Results and Discussion (50 %) – Summary and Conclusions (15 %)

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 28 of 35

Report

Introduction and Background

– Brief description of the main concepts being investigated – Present appropriate equations and/or figures – Use sources such as books, lecture notes, etc and cite them! Remember, It Is About Concept And Theory, NOT Lab Procedure Or Results!

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 29 of 35

Report

Materials and Methods

– What materials did we use? Be specific – Describe the following procedures in your own words:

  • Mixing
  • Strength Testing
  • Electrical Testing
  • Isothermal Calorimetry
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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 30 of 35

Report

Materials and Methods

– What materials did we use? Be specific – Describe the following procedures in your own words:

  • Mixing
  • Strength Testing
  • Electrical Testing
  • Isothermal Calorimetry
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Report

Results and Discussion

Strength – 𝑔

𝑑 ′ vs age for the plain and fly ash concrete

– 𝑔

𝑑 ′ vs w/c for the class mixtures

Resistivity – 𝜍 vs age for the plain and fly ash concrete – 𝜍 vs w/c for the class mixtures

Comment on trends and observations Check units, captions, and legends

Hint: This section is the most important part of a lab report

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Report

Results and Discussion

Isothermal Calorimetry – Heat flow vs age

  • Identify the regions discuss in class

– Cumulative heat vs age – Degree of hydration vs Age

Comment on trends and observations Check units, captions, and legends

Hint: This section is the most important part of a lab report

You will be given data for three mixtures of differing w/c

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CE 331 – Engineering Materials II Slides developed by Spragg, Cao, and Weiss Slide 33 of 35

Report

Results and Discussion

Powers’ Model – Prepare a figure of capillary porosity vs DOH for the 3 mixtures analyzed for calorimetry Qualitative Comparison of the workability of the different mixtures

Comment on trends and observations Check units, captions, and legends

Hint: This section is the most important part of a lab report

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Report

Summary and Conclusions

– Summarize the experiments – Mention the Main Conclusions – Clear and Concise

There will be a rubric posted

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Lab Schedule

Mixing in Lab Analyzing Data Spring Break Hardened Testing

3/5 3/19 3/12

Lab Reports Due by 4/2/15

3/26