Difficulties associated with the interpretation of site data collected over long periods of time from commonly used electrochemical corrosion monitoring techniques often make it difficult to assess the corrosion of reinforcing steel. An alternative approach for the interpretation of data is proposed, based on a model of the quality of passive film upon the steel surface. This model leads to a representation of the corrosion state by means of the relationship, over a long period of time, of the corrosion potential and the logarithm of the Linear Polarization Resistance, since both are functions inter alia of corrosion rate. It is shown that for the reinforced concrete panels tested, data points representing this relationship closely fitted a family of results; allowing the development of a “monitoring control diagram”, MCD. The MCD reveals that for a fixed geometry and experimental conditions, a relationship between the corrosion potential and polarization resistance of steel exists, facilitating a useful monitoring tool for assessment of both the corrosion and remediation of reinforced concrete structures. Particular emphasis is placed on the latter in this work.

Difficulties associated with the interpretation of site data collected over long periods of time from commonly used corrosion monitoring techniques for steel reinforcement in concrete, such as corrosion potential measurements and linear polarisation resistance, often make it difficult to asses accurately the extent of corrosion. An alternative methodology for the interpretation of data is proposed, based upon a model of the quality of the passive film on the steel surface. This model leads to a representation of the corrosion state by means of the relationship, over a long period of time, between the corrosion potential and the logarithm of the linear polarisation resistance. For the reinforced concrete panels tested in this study, data points representing this relationship closely fitted a family of results. This led to the development of a so called 'monitoring control diagram', MCD, in which for a fixed geometry and fixed experimental conditions, a relationship between the corrosion potential and polarisation resistance of steel exists. The establishment of an MCD may enable the development of a useful monitoring tool.

Corrosion testing (half-cell and LPR) was carried out on a number reinforced concrete panels which had been taken from the fascia of a twenty five year old high rise building in Melbourne, Australia. Corrosion, predominantly as a result of carbonation of the concrete, was associated with a limited amount of cracking. A monitoring technique was established in which probe electrodes (reference and counter) were retro-fitted into the concrete. The probe electrode setup was identical for all panels tested. It was found that the corrosion behaviour of all panels tested closely fitted a family of results when the corrosion potential is plotted against the polarisation resistance (Rp). This enabled the development of a so-called 'control curve' relating the corrosion potential to the Rp for all of the panels under investigation. This relationship was also confirmed on laboratory samples, indicating that for a fixed geometry and experimental conditions a relationship between the potential and polarisation resistance of steel can be established for the steel-concrete system. Experimental results will be presented which indicate that for a given monitoring cell geometry, it may be possible to propose criteria for the point at which remediation measures should be considered. The establishment of such a control curve has enabled the development of a powerful monitoring tool for the assessment of a number of proposed corrosion remediation techniques. The actual effect of any corrosion remediation technique becomes clearly apparent via the type and magnitude of deviation of post remediation data from the original (preremediation) control curve.

If a three-element mechanical model incorporating a stress-dependent thermally activated rate process is used to predict the instantaneous and anelastic components of elastic modulus of high density polyethylene, it is suggested that the measured elastic modulus determines the anelastic response rather than an instantaneous response and, furthermore, it is related to an interlamellar shear rather than a slip process in the crystalline region. (C) 1996 John Wiley & Sons, Inc.

The effect of different thermal treatments on the elastic modulus of high-density polyethylene has been studied in order to determine which of the parameters defining the polymer morphology has the major effect on the modulus. After examination of the effects of crystallinity, spherulite size, and lamellar thickness, it is concluded that it is the spherulite size which plays the dominant role in controlling the magnitude of the modulus. (C) 1995 John Wiley & Sons, Inc.