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16 have more pipe installation work than void fill work, and 40 percent of responding state DOTs perform quality control not necessarily a result of CLSM being more applicable for within their organization for CLSM applications. Nearly all bedding/backfill applications than void fill applications. other state DOTs hold the contractor or supplier responsible A fairly new application for CLSM is for use as a subbase/ for quality control. base under bridge approaches. For example, the Delaware Responses from the 1998 survey found that CLSM is spec- Department of Transportation (DelDOT) favors the use ified by a variety of state DOT sections, including materials, of CLSM for many of its bridge approaches. Research by geotechnical, roadway design, bridge design, utility design Oklahoma DOT and Oklahoma State University indicated (also known as pipe design or hydraulics), and construction. satisfactory results (Snethen and Bensen 1998). Based on these Because so many different parties are involved in the specify- applications, CLSM appears to be effective, compared to ing and testing of CLSM, logistical and management difficul- compacted fill, at reducing settlement and minimizing the ties may occur. A more standardized quality assurance pro- "bump at the end of the bridge." gram where CLSM specifications, testing procedures, and CLSM has been used in significant volumes by most states construction methods are clearly organized and managed for only a few years (up to 1998); therefore, there are still chal- should lead to a better understanding of CLSM performance lenges that must be overcome to further increase usage. Fig- and lead to more widespread use. ure 2.4 shows the number of years each state DOT has been using CLSM. Almost half of the states that responded to the Summary survey have used CLSM for less than 4 years (as of 1998). This chapter briefly described the history and background of CLSM, including information on relevant materials, mix- Quality Assurance and Quality Control ture proportions, properties, and applications. A review of Quality assurance and quality control are essential for the this information highlights some of the key research needs successful long-term performance of materials and struc- that existed prior to conducting the research described in the tures. CLSM is a unique material with a variety of applica- remainder of this report: tions. Quality assurance serves as a management tool, is generally developed within the owner's organization, and en- Lack of standardized test methods, specifications, and con- compasses quality control and independent assurance pro- struction guidelines for CLSM grams. Results from the survey indicate that approximately Concerns over long-term strength gain (and impact on half of the states have quality assurance programs for CLSM excavatability) within their materials department. Almost all DOTs have Potential concerns over long-term durability of CLSM, some type of quality assurance program in place. especially related to corrosion of utilities Quality control is generally a contractor's tool to ensure that a product meets specification requirements. For CLSM It is hoped that the findings from this project (highlighted applications, this could include material handling (in the field in Chapters 3 and 4) will help fill some of the gaps in under- and in the laboratory); construction practices; and material standing related to CLSM and will lead to an increase in sampling, testing, and inspection. Interestingly, approximately CLSM usage in a range of transportation applications.