Shrinkage Cracking Potential & Petrographic Analysis of Concrete with MgO Expansive Admixture

Open Access
Author:
Bazer, Abdulsamed
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 13, 2018
Committee Members:
  • Aleksandra Z Radlinska, Thesis Advisor
  • Shelley Marie Stoffels, Committee Member
  • Patrick Joseph Fox, Committee Member
Keywords:
  • shrinkage
  • restrained ring test
  • MgO expansive admixture
  • MgO concrete
  • petrography
  • thin sections
  • concrete
  • cementitious admixtures
  • shrinkage cracking
  • cracking potential
  • microstructure of concrete
  • fluorescence microscopy
  • polarized light microscopy
  • scanning electrom microscopy
  • SEM
  • EDS
  • concrete petrography
Abstract:
Shrinkage cracking is one of the main engineering problems that reduce the durability of concrete infrastructure. MgO expansive admixture is a technology designed to diminish shrinkage cracking in various applications of concrete, to decrease the cost of maintenance and project timeline as well as to increase the service life of the material. Ordinary portland cement (OPC) concrete with MgO expansive admixture is tested by two sets of restrained ring instruments standardized by ASTM C1581 and AASHTO PP-34. Results of restrained ring tests of plain and MgO concrete specimens with 0.42 w/c showed that 5% addition of MgO expansive admixture to the OPC delayed shrinkage cracking in concrete. Petrographic analyses of plain and MgO concrete showed that fewer shrinkage microcracks are observed in the MgO concrete specimens. SEM/EDS analyses showed that hydrated MgO expands in concrete and reduces shrinkage microcracks. Fresh properties of MgO concrete showed insignificant difference from that of plain concrete while MgO admixture reduced the slump of concrete predominantly.