SYNOPSIS The paper describes a study of concrete creep during drying-and-wetting regimes. Damp specimens were loaded at ages of 7 or 140 days and drying began at intervals thereafter. Drying creep was observed; its rate of development was linearly related to that of concurrent shrinkage. The correlation was independent of age at loading and of delay in drying, and only mildly dependent upon stress. For different concretes, drying creep can be closely predicted from water/cement ratio or 28 day strength. The creep recoveries of drying specimens were greater than those of damp specimens; drying creep was recoverable to the same extent as basic creep. No additional recovery of drying creep was observed upon rewetting unloaded specimens. Specimens rewetted under load exhibited wetting creep which was linearly related to concurrent swelling. Reference is made to the calculation in practice of strains in concrete subjected to stress and varying humidity. The nature of drying creep is discussed briefly.

The bond between fresh and hardened concrete can be subjected to various stress states depending on the application and service conditions. Four test methods, reflecting different stress states at the bond between the fresh and hardened concrete, are evaluated. The four methods are a slant shear test, an indirect tension test and two different flexure tests.The slant shear test is shown to b~ consistent and the most sensitive test in showing the strength of the bond, and was used to evaluate the effect of the following parameters on that strength:We conclude that copolymer PVA is a poor bonding agent over a wide range of curing conditions and that the thickness of a portland cement mortar layer has a strong influence on bond strength. The other factors did not affect strength significantly.

The Metropolitan Sewer District of Greater Cincinnati's (MSD) SWMM model is one of the largest SWMM models in the world. In developing this model, MSD advanced the state-of-the-art in collection system modeling in a number of areas including the size and scope of the model, the application of radar rainfall data, the use of water consumption data to estimate dry weather flows, and the use of GIS for model development. It provided MSD with an extraordinary tool to evaluate existing and projected conditions and to use a modeled problem with a modeled solution approach for consent decree compliance. This paper provides the history, features and applications of the MSD SWMM model. Modeling challenges and lessons learned are also discussed.

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