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Sand Equivalent: Fact or Fiction. J.S Lowe, Winstone Aggregates Dr D.J Wilson, The University of Auckland Prof. P.M Black, The University of Auckland. Contents. Overview of common NZ cleanliness tests Sand Equivalent Initial Findings from Experimental Programme Conclusions

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Presentation Transcript
slide1

Sand Equivalent: Fact or Fiction

J.S Lowe, Winstone AggregatesDr D.J Wilson, The University of AucklandProf. P.M Black, The University of Auckland

slide2

Contents

Overview of common NZ cleanliness tests

Sand Equivalent

Initial Findings from Experimental Programme

Conclusions

Recommendations for further work

slide3

Current New Zealand tests to classify the cleanliness of fine aggregates and sand

  • Limit the amount of -75um material
  • Sand Equivalent
    • Developed 1954 by Hveem
  • Methylene Blue or Clay Index
    • Developed 1967 by Jones
  • Plasticity Index
    • Developed 1911 by Atterberg
when are the tests applied to classify the cleanliness of fine aggregates and sand
When are the tests applied to classify the cleanliness of fine aggregates and sand
  • Typically:
  • All NZ Specifications limit the 75um Material
  • All commonly adopt Sand Equivalent
  • Clay Index less popular not used in concrete industry
  • Plasticity Index mainly used in roading applications
  • No tests adapted specifically for uniqueness of NZ Rock sources
  • SE testing to establish the cleanliness >$2m/annum
  • Local aggregates are often dismissed due to non compliance with National NZ Specifications
sand equivalent se
Sand Equivalent (SE)
  • Quickest of current tests taking approx 30 mins
  • Settling Test
  • Not directly measuring clay content, gives a potential
  • Simple and relatively cheap
  • Accuracy and repeatability concerns
initial findings sand equivalent versus clay index
Initial Findings : Sand Equivalent Versus Clay Index
  • Single quarry source & multiple products
  • Sample size = 90
  • Lower CI with increasing SE
  • 37% of samples ≥40 (Sand Equivalent)
  • 87% of samples ≤3 (Clay Index)
initial findings sand equivalent versus clay index1
Initial Findings: Sand Equivalent versus Clay Index
  • Multiple Quarries and Products
  • Sample size = 197
  • 24% of samples ≥40 (Sand Equivalent)
  • 74% of samples ≤3 (Clay Index)
comparison with passing 75um
Comparison with % passing 75um
  • Single quarry source & multiple products
  • Sample size = 90
  • 37% of samples ≥40 (Sand Equivalent)
  • 87% of samples ≤3 (Clay Index)
  • 63% of samples ≤7 (% Passing 75um)
slide9

Multiple Quarries and Products

  • Sample size = 400
  • 24% of samples ≥40 (Sand Equivalent)
  • 74% of samples ≤3 (Clay Index)
slide17

A suggested approach?

  • Steady State Sand Equivalent
  • Allow full settlement to occur
  • Normalised Clay Index
  • CIn = CI ( P x Wp )
  • Wci
  • Where:
  • CIn = normalised clay index
  • CI = clay index (NZS 4407:1991)
  • P = Percentage passing 75um (from particle size distribution)
  • Wp = Weight of sample (from particle size distribution)
  • Wci = Weight of sample (clay index)
conclusions
Conclusions

Percentage of fines in NZ aggregate products does not appear excessive

Evidence to suggest that using Sand Equivalent as primary test method is not maximising the use of NZ aggregates

Clay Index and Sand Equivalent give differing levels of conformance for same sample

Specifications can create testing and consistency issues for aggregate industry

Specifications are reliant on adopted test methods for aggregates

slide19

Further work

  • Relate results to specific swelling clays using XRD data.
  • Analysis of the ultrafines.
  • Comparison of SEss to CIn.
  • Develop SE and CI Prediction Models.