A combined computational/experimental technique was developed to analyze the compressive elastic properties of a rigid organic foam. This technique combines X-ray computed tomography, image analysis, and large-scale finite element computations utilizing a new numerical technique. Predictions of Young's modulus were validated with uniaxial compression testing. Good agreement was obtained between imaging/finite element computations and experimental mechanical measurements within experimental error, and the limited knowledge existing on the solid material comprising the backbone of the foam. Using the new combined experimental/theoretical procedures, it was found that the predicted Young's modulus of the solid backbone differed by more than a factor of 100 % between two different grades of the foam, in accordance with the findings of other researchers. A significant variability of the backbone modulus was also found within the same grade. Density measurements identified the variability between different grades of foam and different as-received sample thicknesses within the same grade of foam.

As part of a larger investigation on freeze-thaw durability of masonry segmental retaining wall (SRW) units, specimens of various geometries were extensively evaluated for their resonant frequency prior to freeze-thaw exposure. These pretest trials were conducted to assess the applicability of the impact resonance method on these specimens, to identify factors affecting test result interpretation, and to obtain initial values for future comparison with values after freeze-thaw cycling. The importance of correctly identifying resonant frequencies corresponding to different modes of vibration of the specimen is highlighted, and methods to achieve this in the laboratory are discussed. The effects of specimen moisture content variations, temperature, and sampling parameters on resonant frequency are also presented.

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Part I (Observed Variations) of this article summarized observed spatial variations in material properties that could exist in Segmental Retaining Wall (SRW) units. As a continuation of Part I, Part II of this article examines in more detail the statistical significance of these observed variations and the implications of such variations on sampling and test result interpretation. It was demonstrated that the observed spatial variations were statistically significant along the casting direction (parabolic distribution) and in a direction away from the split face (linear distribution). As a result of these variations, an analysis involving test simulations showed that, depending on how specimens are sampled, a technician could interpret the SRW unit as being either very uniform or marginally uniform. The effect of increasing the quantity of specimens per test was only to modestly improve the expected value of the perceived test variation, though the range of possible values of perceived variation was substantially narrowed. This analysis also showed that variations in test results decreased with increasing soak time. Finally, an alternate method of specimen sampling (stratified random sampling) was explored and shown to yield slightly more consistent test results by reducing the overall variability in test results.

Segmental retaining walls (SRWs) constructed of dry-cast concrete masonry units are used in transportation-related applications for which freeze-thaw (FT) durability is evaluated on the basis of percent mass-loss accumulated after multiple FT cycles as per ASTM C1262. This study compared mass loss, mass gain owing to absorption during (FT) exposure, and relative dynamic modulus (RDM) as per ASTM C215. Application of RDM required accounting for the influence of the shape and moisture content of SRW coupons on resonant frequency, with corrections that are likewise applicable to ASTM C666 for ordinary concrete. It was demonstrated that mass loss does not exclusively indicate surface damage, and the relationship between mass loss and RDM is unique to each specimen. Mass gain (as moisture absorption) during testing emerged as a key index of damage, with rapid escalation of mass loss and reduction in RDM at the number of FT cycles required to increase the moisture content of the residual coupon by about 1%.