XRD and unconfined compressive strength study for a qualitative examination of calcium-arsenic compounds retardation of cement hydration in solidified/stabilized arsenic-iron hydroxide sludge

Tanapon Phenrat, Taha F. Marhaba, Manaskorn Rachakornkij

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

This study investigates the adverse effects of synthesized arsenic-iron hydroxide sludge, the by-product of arsenic removal by coagulation with ferric chloride, on unconfined compressive strength (UCS) and cement hydration of solidified/stabilized matrices. The results from both UCS tests and X-ray diffraction (XRD) implied that synthesized arsenic-iron hydroxide sludge might not be chemically inert in a cementitious environment, which could account for the retardation of cement hydration. The culprit for this retardation is likely to be the multiphase formation of calcium arsenic compounds suggested by the strong peak at 7.90 Å (11.2° 2θ). This peak appeared when more than 20 and 13% of arsenic-iron hydroxide sludge were added to the solidification/stabilization (SS) process of cement-water and cement-hydrated lime-water systems, respectively. The proposed mechanisms for the retardation of cement hydration by calcium-arsenic compounds are calcium complexation and, subsequently, surface precipitation due to the interaction between desorbed arsenate and hydration by-products in a cement porewater environment. The extent of the hydration retardation is qualitatively determined by the semiquantitative comparison of Ca3 Si O5 and Ca2 Si O4 remaining after 28 days of hydration between the control SS samples and that with various doses of the sludge added. When 20 and 33% of the sludge were added into the SS matrices, the remaining Ca3 Si O5 and Ca2 Si O4 were more than that of the control sample by factors of 2 and 3.2, respectively.

Original languageEnglish (US)
Pages (from-to)595-607
Number of pages13
JournalJournal of Environmental Engineering
Volume133
Issue number6
DOIs
StatePublished - 2007

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Civil and Structural Engineering
  • Environmental Chemistry
  • Environmental Science(all)

Keywords

  • Calcium
  • Cement
  • Compressive strength
  • Sludge
  • Solidification
  • Stabilization
  • X rays

Fingerprint

Dive into the research topics of 'XRD and unconfined compressive strength study for a qualitative examination of calcium-arsenic compounds retardation of cement hydration in solidified/stabilized arsenic-iron hydroxide sludge'. Together they form a unique fingerprint.

Cite this