Ettringite

About: Ettringite is a research topic. Over the lifetime, 2702 publications have been published within this topic receiving 67056 citations. The topic is also known as: woodfordite.

Mechanism of seawater attack on cement pastes

Abstract: TYPE I (WHITE), II, AND V (ZERO TRICALCIUM ALUMINATE) CEMENT PASTES OF WATER-CEMENT RATIOS OF 0.3 AND 0.5 WERE IMMERSED IN SEAWATER AND SOLUTIONS OF SODIUM AND MAGNESIUM SULFATES. THE ATTACK ON THE CEMENT PASTES WAS INTERPRETED IN TERMS OF KINDS, AMOUNTS, AND LOCATION OF THE REACTION PRODUCTS IN THE PASTES. X-RAY DIFFRACTION AND DIFFERENTIAL THERMAL ANALYSIS WERE USED IN STUDYING THE SPECIMENS. ETTRINGITE IN TYPE I CEMENT PASTES PRECIPITATED AS CRYSTALS. GROWTH OF THESE IN CONFINED SITES CAUSED EXPANSION. THE ETTRINGITE IN TYPE V CEMENT PASTES PRECIPITATED AND PERSISTED AS A GEL. SINCE THERE WAS NO CRYSTAL GROWTH, EXPANSION DID NOT OCCUR. THE ROLE OF CHLOROALUMINATE, BRUCITE, AND GYPSUM IS DISCUSSED. /AUTHOR/

Field experiences in concrete deterioration by thaumasite formation: possibilities and problems in thaumasite analysis

Abstract: In Germany, after testing two concretes deteriorated due to the formation of thaumasite, possibilities and problems in analysing thaumasite and ettringite-containing concrete samples will be discussed. The image of polished thin sections show, that thaumasite formation leads to microstructures similar to the microstructure of ettringite. It is recognisable in the microstructure that the formation of thaumasite happens as well via deterioration of CSH-phases as via the decomposition of ettringite. The identification of thaumasite using environmental scanning electron microscopy is possible without problems. Investigations using X-ray powder diffraction did show, that quantitative analysis of thaumasite and ettringite is possible by using the Rietveld method. The samples of deteriorated concrete (excluding coarse aggregate) contain 20–75% thaumasite.

Carbonation of calcium sulfoaluminate cement blended with blast furnace slag

Abstract: The present study investigated the carbonation of calcium sulfoaluminate (CSA) cement blended with blast furnace slag. Paste samples were prepared by substituting CSA cement with slag at dosages of 0, 30, 50, and 70 wt%. The samples were carbonated for 28 days at a CO2 concentration of 3% after a sufficient pre-curing period. The test results indicated that slag incorporation did not affect the phase assemblage of the sample regardless of carbonation, while the incorporated slag promoted the formation of monosulfate and stratlingite upon carbonation in which this observation is closely related to the improved reaction degree of Si in the slag by carbonation. Meanwhile, monosulfate and ettringite were the first phases to be carbonated, while the C-A-S-H gel formed due to the carbonation of belite, thereby enhancing the compressive strength by refining the pore size in the gel pore region. On the other hand, the carbonation degree of the samples vastly increased as the slag content increased due to a small amount of ettringite formed along with the low reaction degree of slag which induced the development of macropores.