Accession Number : AD0763832

Title :   Hydration Characteristics and Properties of Alite Pastes Containing Small Amounts of C3A, C4AF, and CSH2.

Descriptive Note : Interim technical rept.,

Corporate Author : CALIFORNIA UNIV BERKELEY STRUCTURAL ENGINEERING LAB

Personal Author(s) : Mehta,Povindar Kumar ; Williamson,Robert Brady

Report Date : DEC 1972

Pagination or Media Count : 24

Abstract : Mixtures of high-purity alite, tricalcium aluminate (C3A), a calcium aluminum ferrate (C4AF) and gypsum (CSH2) were used to make cements typical of different types of portland cements. The hydrated cement pastes wer investigated at regular intervals for microstructure, strength development, and sulfate resistant characteristics. CSH2 accelerated the hydration of alite at early ages. The scanning micrographs showed that in the presence of CSH2 the outer hydration products from the alite grains grew more rapidly. In an accelerated sulfate resistant test using magnesium sulfate additions, expansion leading to cracking in pastes containing C3A or 15-20% C4AF were shown to be associated with ettringite formation. X-ray diffraction studies showed that large quantities of CSH2 were formed in the hydrated alite pastes. In the presence of moisture, CSH2 dissolution could ultimately lead to strength loss. Hence, the inherent inertness of even ASTM Type V portland cement concrete exposed for long periods to sulfate environments is questionable. (Author)

Descriptors :   (*CEMENTS, SILICATES), (*SILICATES, MECHANICAL PROPERTIES), COMPRESSIVE PROPERTIES, SURFACE PROPERTIES, ELECTRON MICROSCOPY, CALCIUM COMPOUNDS

Subject Categories : Ceramics, Refractories and Glass
      Construction Equipment, Materials & Supplies

Distribution Statement : APPROVED FOR PUBLIC RELEASE