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62 Table 4.1. Matrix of field testing issues and applications. Agency or Organizationa Issue/Application Hamilton UT c d Texas e NRMCA County EBMUD TAMU Austinb DOT (OH) Technical Issue Long-term strength gain/excavatability Short-term strength gain/constructibility Corrosion of metals in CLSM Productivity and cost Resistance to freezing and thawing Construction issues (i.e., pipe floating) Settlement Use of by-product materials Environmental issues Permeability/leak detection CLSM Application Backfill Utility bedding Void fill Bridge approach a Information on productivity and cost was also obtained from the New York DOT but is not included herein (for conciseness). Also, a field test was planned with the Florida DOT, but permitting issues prevented the field test from occurring. b UT Austin = University of TexasAustin c NRMCA = National Ready-Mix Concrete Association d EBMUD = East Bay Municipal Utility District e TAMU = Texas A&M University Field Test at the University mix concrete producers, each of whom had experience with of TexasAustin producing CLSM for various applications. The mixture pro- portions were based primarily on experience gained from the Introduction laboratory portion of this study. Mixtures were selected to span Significant field testing was performed at the J. J. Pickle a range of materials and proportions and to generate strengths Research Campus at the University of TexasAustin. The that would result in various degrees of ease of excavatability. main goals of these tests were to evaluate the use of CLSM as Intentionally, no trial mixing was performed using materials trench backfill; to establish a link between laboratory tests and similar to those used in the field test, specifically to deter- field performance; and to study the impact of materials, mix- mine if prescriptive mixture proportions (e.g., cement con- ture proportions, and curing regime on long-term strength tent, aggregate content, water added to achieve target flow) gain and excavatability. would result in desirable mixtures (e.g., target flow, mini- mal segregation/bleeding). On-site adjustments were available for these mixtures if they arrived at the field test either too dry Materials and Mixture Proportions or too wet in consistency, as discussed later. However, if the Six CLSM mixtures were included in this study, as shown in water added to the drier mixtures resulted in excessive bleed- Table 4.2. Each of the mixtures was procured from local ready- ing or segregation, no further water was added. Table 4.2. Mixture proportions for excavation study. Type I Fly Concrete Water Air Mixture Fly Ash Flow Density Mixture Cement Ash 3) Sand Content Content Temperature (kg/m (mm) (kg/m3) (kg/m3) Type (kg/m3) (kg/m3) (%) (C) Flash 0 Class C 224 1672 165 4.0 190 35.2 2179 A1 30 0 130 130 29.5 200 33.6 1539 A2 60 0 130 130 28.5 220 34.5 1539 Paste 60 Class F 1195 485 485 1.0 420 42.5 1795 F1 30 Class F 180 175 175 2.25 100 36.8 2051 F2 60 Class F 180 175 175 2.5 140 35.2 2083 "" = not used