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"Statistical reliability of the screw pullout test in the assessment of in-situ concrete strength" presented at CERI2018 by Shah Nur Sourav

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The assessment of concrete compressive strength is an essential element in assessing the load carrying capacity of structural members in an existing structure. The reliability of non-destructive tests (NDTs) results for assessing concrete strength is always a questionable issue. This is mainly due to the uncertainty associated with the strength predictions based on the NDT measurements. This paper studies the Post-installed Screw Pullout (PSP) test as a potential method for assessing in-situ concrete strength. The objective of this paper is to study the reliability of the assessment using PSP test by analysing the effects of several influencing factors: presence of coarse aggregates, types and size of coarse aggregates, and the amount of coarse and fine aggregates. Analyses of results are presented to evaluate the repeatability and reliability of the PSP test with respect to test standard deviation, coefficient of variation and RMSE. The repeatability of the screw pullout test has been compared with the other NDTs available in literature.

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"Statistical reliability of the screw pullout test in the assessment of in-situ concrete strength" presented at CERI2018 by Shah Nur Sourav

  1. 1. Workshop CERI, UCD, Dublin Wednesday 29th August 2018
  2. 2. Md Shah Nur Alam Sourav, Salam Al-Sabah and Ciaran McNally Statistical reliability of the screw pullout test in the assessment of in-situ concrete strength
  3. 3. Focus of the paper • Statistical properties of the test • Factors influencing the test • Repeatability • Strength assessment and reliability
  4. 4. Research Background • In-situ compressive strength of concrete • Core testing • Non-destructive tests (NDTs) • Indirect approach and uncontrolled factors • Empirical relationships • Lack of accuracy and confidence level • Core testing + NDTs • Time and costs
  5. 5. Post-Installed Screw Pullout (PSP) test • Newly developed • Partially destructive in nature • HUS3-H8- a product of Hilti • Inner diameter-7.70 mm • Outer diameter-10.40 mm • Hole diameter-9.0 mm
  6. 6. Post-Installed Screw Pullout (PSP) test Concrete cone failure Complete pullout failure
  7. 7. Post-Installed Screw Pullout (PSP) test Experimental set up Crushed concrete in between the threads
  8. 8. Post-Installed Screw Pullout (PSP) test Load-displacement curve Zone 1 Zone 2 Zone 3 Zone 4
  9. 9. Post-Installed Screw Pullout (PSP) test Experimental investigation • 73 batches of mortar & concrete • 3 different aggregate types • Limestone, brick chips and lightweight • 292 PSP tests • Corresponding compressive strength tests
  10. 10. Post-Installed Screw Pullout (PSP) test Factors studied • Compressive strength • Aggregate type • Cement content • Water-cement ratio • Aggregate content • Particle size distribution Regression analysis
  11. 11. Post-Installed Screw Pullout (PSP) test Repeatability of the PSP test • With-in test variation (CoV) as inherent scatter Aggregate Mean CoV Limestone 16% Brick chips 9% Lightweight 9% Mortar 7%
  12. 12. Post-Installed Screw Pullout (PSP) test Strength relationships • Linear relationships considered • Effect of aggregate type • Type of relationship
  13. 13. Post-Installed Screw Pullout (PSP) test Rebound hammer and UPV
  14. 14. Post-Installed Screw Pullout (PSP) test Statistical properties Aggregates R-sq Mean Residual (MPa) RMSE (MPa) Mortar (No aggregate) 0.90 3.24 4.47 Limestone 0.80 4.98 6.29 Brick chips 0.83 3.40 3.33 Lightweight 0.87 1.90 2.28 All 0.73 5.26 6.83 All except mortar 0.75 4.70 6.13
  15. 15. Conclusions • Cost effective in compared to core test and other NDTS • Harder the aggregate, higher the CoV • No effect of compressive strength on the repeatability • Only aggregate type has direct influence on the test • R-sq values are greater than 0.80 when produced separately based on aggregate • Mean residual less than 5 MPa in every case • Potential to be reasonably accurate and reliable
  16. 16. The TRUSS ITN project (http://trussitn.eu) has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 642453 Thanks for your attention

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