Click for next page ( 19


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 18
18 Table 3.1. CLSM applications and relevant properties. CLSM Application Important Properties Potentially Important Properties Flow Freeze-thaw resistance Compressive strength Leaching and environmental impact Excavatability Backfill Hardening time Settlement Corrosion of metal utilities Subsidence Flow Freeze-thaw resistance Compressive strength Leaching and environmental impact Utility bedding Hardening time Thermal conductivity Corrosion of metal utilities Flow Unconfined compressive strength Void fill Subsidence Settlement Flow Leaching and environmental impact Compressive strength Hardening time Bridge approaches Shear strength Resilient modulus/CBR Settlement Freeze-thaw resistance portland cement and the three fly ashes (Class F, Class C, study. These common mixture types were further delin- and high carbon) used is provided in this table, and more eated by defining a range of typical proportions (e.g., 30 to specific information about the chemical and physical prop- 60 kg/m3 of portland cement). For convenience, the mix- erties of these materials can be found in the NCHRP Project tures selected for the laboratory study can be classified as 24-12(01) Interim Report (Folliard et al. 2001). Three types follows: of fine aggregates were used throughout this project: con- crete sand conforming to ASTM C 33, foundry sand espe- CLSM (with fine aggregates) cially blended for CLSM, and bottom ash passing a No. 4 Type I portland cement: 1 type, 2 levels (30 kg/m3, (4.75 mm) sieve. Figure 3.1 compares the gradations of the 60 kg/m3) three materials. The concrete sand meets the requirements Fly ash: 3 types, 3 levels (0 kg/m3, 180 kg/m3, 360 kg/m3) of ASTM C 33 but approaches the coarse limit of the grada- Fine aggregate: 3 types, 1 level (1500 kg/m3) tion band. The bottom ash was found to be slightly coarser Air content: 3 levels (entrapped air only, 15% to 20% air, and the foundry sand slightly finer than the ASTM C 33 gra- 25% to 30% air) (Air-entraining agents were not used dation limits. for CLSM containing fly ash) CLSM (without fine aggregates) Type I portland cement: 1 type, 1 level (60 kg/m3) Mixture Proportions Fly ash: 3 types, 1 level (1200 kg/m3) Based on a survey of current practice (performed as part Air content: 1 level (entrapped air only) of the original NCHRP Project 24-12), the most common CLSM (with set accelerator) types of CLSM mixtures were selected for the laboratory Selected mixtures from the test matrix Table 3.2. Materials included in the laboratory program. Materiala Description Portland cement ASTM C 150 Type I (S.G.=3.15) ASTM C 618 Class F (CaO=1.6%, LOI = 2.9%, S.G.=2.41) Fly ash ASTM C 618 Class C (CaO=26.7%, LOI = 0.37%, S.G.=2.51) High-carbon fly ash (CaO=6.0%, LOI = 14.44%, S.G.=2.09) ASTM C 33 concrete sand (S.G.=2.60, Absorption=1.0%, FM = 3.0) Fine aggregate Foundry sand (ferrous) (S.G.=2.36, Absorption=5.6%, FM = 2.14, LOI=4.5%) Bottom ashb (S.G.= 2.28, Absorption = 8.9%, FM = 2.89) Air-entraining agent (liquid, designed specifically for CLSM) Chemical admixtures Accelerating admixture (non-chloride) a More information on these materials can be found in NCHRP Project 24-12(01) Interim Report (Folliard et al. 2001). b Bottom ash is classified as a fine aggregate because of similar particle size.

OCR for page 18
19 100 Concrete Sand Bottom Ash Foundry Sand 80 ASTM C33 Limits Percent Passing 60 40 20 0 0.1 1 5 Sieve Size (mm) Figure 3.1. Gradations of aggregates used in study. For each of these mixtures defined above, the types and cant results with a minimal number of trials. In other words, amounts of cement, fly ash, and aggregates were selected prior rather than producing CLSM with every possible combina- to mixing (as described later), and the water content of each tion of material and dosage, which would not be feasible, an mixture was then adjusted to achieve a flow of 200 to 250 mm, optimized test matrix was produced that could be used to as measured by ASTM D 6103. The 38 mixtures included in predict test results across the entire spectrum of variables. In the initial laboratory study were classified and tested accord- addition, the program can be used to statistically compare ing to their expected ability to provide information on the fol- the results of one test to another or the effects of individual lowing three groups of CLSM properties (based on expected or combined variables on test results. The program was also level of importance): designed to assess the repeatability of test results by requir- ing duplication of certain mixtures within the test matrix. I. Important CLSM properties (flow, setting time, uncon- Initially, two separate mixture series were generated fined compressive strength, and corrosion) using the statistical software: one for nonair-entrained Measured for all 38 mixtures in initially proposed CLSM (with fly ash) and one for air-entrained CLSM (with- Phase I study out fly ash). The nonair-entrained mixtures are shown II. Potentially important CLSM properties (excavatability, in Table 3.3 (a mixture number followed by "r", such as 1r, subsidence, freezing and thawing, segregation and bleed- denotes a mixture repeated or duplicated for statistical ing, triaxial shear, CBR, resilient modulus, water perme- purposes). ability, drying shrinkage) The air-entrained mixtures originally proposed for study Measured for selected mixtures only (6) were selected using the statistical software, but after diffi- Only "order of magnitude" values sought culties were encountered in generating entrained air in cer- III. Less important CLSM properties (direct shear strength, tain mixtures, the decision was made to include mixtures air/gas permeability, consolidation, thermal conductiv- covering all of the selected variables. That is, two cement con- ity, leaching/environmental impact) tents (30 kg/m3 and 60 kg/m3), two target air contents (15 to Not included in laboratory study 20 percent and 25 to 30 percent), and two aggregate types Literature-based and existing-practicebased cover- (concrete sand and bottom ash) were used in all combina- age only tions to create a total of eight mixtures. From these eight mix- tures, three were selected for replicate mixtures, bringing the After selecting representative materials and a range of total number of air-entrained mixtures to eleven, as shown mixture proportions, as previously defined, a statistical soft- in Table 3.4. ware program (ECHIP) was used to generate the majority of The mixtures shown in Table 3.5 were strategically chosen the mixtures within the test matrix. This software uses ex- to investigate specific mixture types of interest to the research perimental design concepts to produce statistically signifi- team. The mixtures represented typical CLSM paste mixtures

OCR for page 18
20 Table 3.3. Nonair-entrained CLSM mixture proportions (using statistical software)a. Cement Fly Ash Water Total Air Fresh Fly Ash Fine Aggregate Flow Mixture Content Content Demand Bleeding Content Density Type b Type c (cm) (kg/m 3 ) (kg/m 3 ) (kg/m 3 ) (%) (%) (kg/m 3 ) 1 30 C 180 CS 211 20.0 NA 0.9 1965 2 60 C 180 CS 206 20.0 2.45 1.0 2108 1r 30 C 180 CS 206 21.0 2.08 0.9 1974 15 30 C 360 FS 486 20.0 0.13 2.8 1741 3 60 C 360 BA 577 17.8 4.32 1.7 1754 8 60 HC 180 FS 532 24.1 1.04 3.3 1647 10 30 HC 180 BA 628 14.0 4.81 2.0 1681 9 60 F 360 FS 520 20.0 0.54 2.5 1684 5 60 F 180 BA 600 17.8 5.84 2.5 1739 12 30 C 360 BA 572 21.6 3.64 2.7 1774 4 30 F 360 CS 220 20.0 0.39 2.2 2199 7 30 F 180 FS 501 20.0 0.57 2.1 1817 3r 60 C 360 BA 541 20.0 2.58 2.1 1997 4r 30 F 360 CS 220 21.6 2.92 1.8 2211 13 60 C 360 FS 499 20.0 0.00 1.8 1902 5r 60 F 180 BA 600 16.0 7.20 1.4 1887 14 60 F 360 CS 216 21.6 1.00 1.3 2174 2r 60 C 180 CS 206 25.0 0.21 0.5 2291 11 60 HC 360 BA 573 23.0 6.42 1.7 1743 6 30 HC 360 CS 315 20.0 2.26 1.3 2103 a ECHIP randomizes order of mixtures and provides for duplicates b C = Class C, HC = High Carbon, F = Class F. c 3 CS = Concrete Sand, FS = Foundry Sand, BA = Bottom Ash. Fine aggregate content was held constant at 1500 kg/m . (i.e., 5 percent cement, 95 percent fly ash) and also included mixtures were based in most cases on previously cast mix- mixtures containing an accelerating admixture. Lastly, this tures (from the original 38 mixtures), but there were other table includes nonair-entrained CLSM mixtures containing mixtures, such as rapid-setting CLSM containing only Class foundry sand (selected after the difficulties encountered in C fly ash as a binder, that were included to better reflect cur- entraining air in mixtures containing foundry sand). rent practice in some parts of the country. Nine sets of addi- After casting and testing the initially proposed mixtures tional mixtures were cast and will be referred to throughout (as summarized in Tables 3.3 to 3.5), additional mixtures this report by as mixture series A through I, as summarized were cast to further investigate or refine selected test meth- in Table 3.6. Because the compressive strength of CLSM is ods or to study selected CLSM properties in more detail. The the most common property measured (and often the only Table 3.4. Air-entrained CLSM mixture proportions. Cement Water Total Air Fresh Fly Ash Fine Aggregate Flow Mixture Content Demand Bleeding Content Density Type b Type c (cm) (kg/m 3 ) (kg/m 3 ) (%) (%) (kg/m 3 ) 18 60 None CS 200 21.6 0.70 16.5 1836 17a 30 None BA 582 12.7 4.35 20.0 1447 16 30 None CS 295 20.0 2.33 16.0 1922 21 30 None CS 170 18.0 0.62 25.5 1789 22 60 None CS 131 20.0 0.05 26.5 1748 22r 60 None CS 136 18.0 0.43 25.5 1802 16r 30 None CS 295 19.1 2.35 15.5 1874 19a 30 None BA 492 13.0 1.08 25.0 1385 20a 60 None BA 525 13.0 3.41 18.5 1485 23 60 None BA 454 14.0 1.30 28.5 1382 20r 60 None BA 525 13.0 1.44 15.5 1511 a These mixtures were substituted for the originally proposed mixtures because of extreme difficulty in entraining air in mixtures containing foundry sand. The originally proposed mixtures containing foundry sand were still cast, but without entrained air. b Fly ash was not used for these mixtures. c 3 Fine aggregate content was held constant at 1500 kg/m . CS = Concrete Sand, BA = Bottom Ash.