Pore morphology variation under ambient curing of plain and fiber-reinforced high performance mortar at an early age

Abstract

Pore morphology and its changes at an early age in two different mortar mixtures are analyzed by means of a CT-Scan and DIP software. Both mixtures share the same cement paste composition. The only difference between them is the inclusion of 0.1% by volume of steel fibers in one paste and its omission from the other paste. A total of six specimen cylinders measuring 45.2 mm in diameter and 50 mm in height were cast. All the specimens were held in a controlled atmosphere at 20 °C and at 60% humidity, reflecting natural ambient curing conditions. Each specimen was scanned at 1, 2, 3, 4, and 7 days using a micro CT-Scan. The data were analyzed using a Digital Image Processing (DIP) software and some post-processing subroutines. Each individual void was identified and isolated and all its geometrical parameters were measured. Among the most interesting and relevant findings was that the presence of fibers substantially modified the pore morphology, increasing the volume of voids, and the pore-size, and reducing the shape factor of the voids, among other effects. Both mixtures showed different pore morphologies at the beginning of the curing process that metamorphosed into different and even divergent geometrical dimensions.