Cementitious materials obtained from different sources, although evaluated and classified by the same methods and criteria, inevitably produce concrete with compressive strength variance despite other inputs and constituents remaining constant. This paper investigates the effect of cement by type and source on strength as a function of supplementary cementitious material (SCM) replacement and aggregate type. This was accomplished by compiling and analysing compressive strength data from previous research initiatives; it was concluded that a cement source change can produce coefficients of variation, range and range divided by average compressive strength values up to 18%, 2700 psi (18·6 MPa) and 0·40, respectively, at 14 to 56 d time frames. Concrete comprising SCMs displayed a statistically significant increase in compressive strength variation and a general decrease in compressive strength predictability against mixtures without SCMs when a cement source was changed, and specific aggregate/cementitious material combinations influenced compressive strength variability due to a change in the cement source.

This document is subject to special export controls and each transmittal to foreign governments or foreign nationals may be made only with prior approval of the Air Force Materials Laboratory (MXAS). Wright-Patterson Air Force Base. Ohio 45433. The reaction between aluminum and water, which is sluggish at ambient temperature, is shown below: Al + 3H 2 0-WA I(OH) 3 + 3/2 H2 2j 4i VOL' The presence of gelatinous hydroxide, oxide film or hydrogen all contributh to the system's stability. Due to the fact that metals are such good conductors, the total resistance of the galvanic circuit is usually a function of the solution or electrolyte resistanbe. Consequently, no appreciable galvanic corrosion will be, generated in distilled water due to its poor conductance. Addition of tap water or sult water will supply sufficient ionizable salts to make the water conductive. This results in an increase in the corrosion rate as a function of temperature. The algebraic sum of the two relevant half-cell reactions is given below: