Method for determining the moisture condition in hardened concrete

Abstract

A method for studying the moisture conditions inside hardellcd concrete and cement paste is described. An electric hygrometer developed by the National Bureau of Standards was used to measure the relative hum idity in cavities at various locations in the material. The r elat ive humidity inside 12-inch concrete cubes stored at 50 percent rehtive hu midity for 300 days was found to range from 50 percent near the surface to 66 percent near the center of the cube. For cubes stored at 20-percent relative humidity the co rresponding range was from 20 t o 60 p ercent. The relative humidity over cement paste of approximately normal consistency and cured in hermetically sealed bottles fo r 28 days was found to be 88 percent for a m oderate heat-oI-hardening cement a nd 79 percent for a highearly-strength cement. CONTENTS

Alkali–Silica Reactions: Literature Review on the Influence of Moisture and Temperature and the Knowledge Gap

“…Moisture plays a vital role in the durability of concrete [ 42 ]. Its availability beyond a specific limit could be favourable for the alkali–silica reaction, freezing and thawing [ 21 ], carbonation [ 43 ], etc.…”

Curing, Hydration, and Microstructure of Cement Paste

“…While they imposed reduced relative humidities on their specimens via external drying, here, the internal relative humidity is reduced autogenously due to the chemical shrinkage and self-desiccation accompanying the cement hydration reactions. 24,31,32 It should be noted that for sealed curing conditions, microcrack formation could also be contributing to the observed repercolation of the open gel and capillary pores.…”

A study of the national humidity and moisture measurement system

“…The history of the involvement of the National Bureau of Standards in the humidity and moisture measurement system dates back, at least, to the early Twenties, ihe concern then and over the ensuing years was in the develooment of specialized instrumentation [10, 33,48,49,[108][109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129], humidity cabinets and chambers [15, [130][131][132] and environmental test room.s [133]. Late in the Thirties, the Bureau developed a small electrical humidity sensor for use in radiosondes [116,117] which was adopted by the National Weather Service (then the Weather Bureau) and by the U. S. military meteorological services, and subsequently became an important industrial device.…”