Freeze-thaw durability and ASTM C 1262 testing of segmental retaining wall (SRW) units.

摘要

Segmental Retaining Walls (SRW) have grown in popularity in recent years for a variety of applications including earth retention near highways, parking grounds and landscaping. Although SRW manufacturing technology has improved in recent years and durable units can be produced, there have been documented cases of deterioration of SRW units in the field.; Initial studies in this research were targeted towards determining damage mechanisms in field SRWs and identifying variables relevant to their durability. Experimental work was conducted in the areas of SRW durability in the absence of frost conditions through their interaction with salts, freeze-thaw durability in the presence of different types of deicing chemicals and correlating material characteristics to freeze-thaw durability. Details of this work are covered in the Federal Highway Administration, FHWA Project No. DTFH61-02-R-00078 (Project Manager: Mike Adams) report.; Through these studies, it became increasingly apparent that variability in the evaluation of frost durability of SRWs was a critical issue in the industry. This dissertation was thus geared towards an objective evaluation of ASTM C 1262, which is the standard used to evaluate freeze-thaw resistance of SRWs. In general, sampling methods were found to be important due to systematic spatial distribution of properties over SRW units and the presence of cracks on split surfaces. Freezer variability also affects specimen exposure condition and an approach was developed to maximize compliance of specimens with test method requirements. Detailed studies were also carried out to elucidate ice formation processes and associated damage during freezing of solutions and to relate these observations to actual specimen cooling response under a variety of test conditions including variations in surrounding water volume, container size and number of specimens in freezer. This dissertation also covers a comprehensive study conducted to evaluate the significance of variations due to test method tolerances and explores alternate techniques to assess specimen condition using resonant frequency, pulse velocity, visual scaling rating, specimen moisture changes and modulus of rupture. Finally, recommendations for changes to ASTM C 1262 are incorporated in an annotated version of this test standard. Key recommendations include evaluating uniformity of the freezer environment, maximizing uniformity of the cooling curve, details of specimen and containers, and damage assessment via resonant frequency and moisture content.