DaraFill. Concrete. Controlled Low Strength Material

Transcription

1 Concrete E N G I N E E R I N G B U L L E T I N 1 DaraFill Controlled Low Strength Material This Engineering Bulletin describes the test methods and results used to determine several mechanical properties of Controlled Low Strength Material (CLSM) containing DaraFill. This information will allow engineers to properly design Controlled Low Strength Material containing DaraFill. Introduction DaraFill is a liquid air-entraining performance additive which is added to CLSM. CLSM is also often referred to in the construction industry as flowable fill, controlled density fill, flowable mortar, and soil-cement slurry. DaraFill was developed by Grace Construction Products to broaden the potential applications and end uses for CLSM, particularly in the high performance spectrum of CLSM mix designs. The utilization of DaraFill in CLSM results in stable air contents ranging from 15-35%, allowing for approximate 5% reductions in both water contents and cementitious factors. CLSM containing DaraFill does not segregate, settle or bleed, resulting in a homogenous, cohesive CLSM which can be placed in one pass. Typical unit weights for DaraFill CLSM range from kg/m 3 (9-12 lbs/ft 3 ), lower than conventional CLSM unit weights. These lighter unit weights not only improve material yields, but more importantly, allow for ultimate strength cap specifications to be easily met for future excavatibility. DaraFill CLSM achieves superior flowability characteristics via the ball-bearing effect caused by the presence of millions of air-voids, in lieu of utilizing conventional methods to obtain flowability (i.e. high water content). As CLSM has begun to gain acceptance, some uncertainty has arisen whether to categorize and test the properties of CLSM as compacted fill or concrete. Since CLSM is generally specified in lieu of compacted fill, it seems logical to evaluate CLSM utilizing soil test procedures. Often, a combination of laboratory and field test data can provide sufficient information to the specifier to make a decision whether CLSM is a viable replacement for compacted soil for a particular end use. Depicted below are test procedure descriptions, along with test results conducted on several DaraFill CLSM mixes. Unconfined Compressive Strength (ASTM D 4832) Unconfined compressive strength provides a useful index test to measure the strength of cohesive materials and should be considered as a valuable quality control and design tool for understanding long-term strength and durability properties of CLSM. One advantage of compressive strength testing is the simplicity and ease of fabricating and testing CLSM specimens, when compared to traditional soil test procedures.

2 Table 1 DaraFill CLSM Compressive and Direct Shear Strength Compressive Strength Direct Shear Strength Cement Flyash Water Sand DaraFill Air kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 MPa (psi) kg/cm 2 = (tons/ft 2 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd ) (%) Day Day Day Day Day Day Day (1) () (25) (238) (3) (35.2) (18) (21) (33) (53) (.7) (.34) (.84) 119 kg/m 3 (2 lbs/yd 3 ) cement, Ø (2) () (25) (2295) (3) (35.1) (68) (11) (131) (121) (1.4) (1.78) (2.92) 119 kg/m 3 (2 lbs/yd 3 ) flyash Ø (1) (2) (25) (2168) (3) (3.) (57) (74) (119) (138) (.58) (.74) (2.94) 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash Ø (5) (25) (495) (271) () (.4) (36) (45) (47) (69) (.44) (.28) (1.6) Ø CLSM compressive strength data can provide a general indication of design parameters obtained in specific soil tests such as Direct Shear, Triaxial Shear, California Bearing Ratio (CBR), Modified (cyclic) CBR, Incremental Consolidation, Water and Air Permeability, and Freeze-Thaw Cycling etc. CLSM compressive strength data also provides assurance that CLSM mix designs do not exceed maximum strengths required for future excavation. Tables 1 and 4 depict compressive strength results conducted in accordance with ASTM Standard Test Method for Preparation and Testing of Soil-Cement Slurry Test Cylinders (ASTM D 4832) for several CLSM mixes at 3, 7, 28 and 56 days. Direct Shear (ASTM D 38) Shear strength data measures the ability of the soil to resist shear stress. Large uncontrolled movements (i.e. landslides) occur when the shear stresses from loading exceed the shear strength of the soil. Typically, because soils exhibit a wider variety of deformation characteristics and more complex failure behavior, when compared to concrete, engineers must analyze stress fields in three dimensions. Fortunately, principles of applied mechanics are considered to be reasonably applicable for measuring properties of soils. Therefore, the Direct Shear Test (ASTM D 38), can be utilized to measure the drained shear strength for compacted soil and CLSM. Referring to Table 1 and Figures 1A-1D, direct shear testing was conducted on three DaraFill CLSM and one reference CLSM mix at 3, 7 and 56 days. At 56 days, all mixes met or exceeded typical compacted granular soil shear strengths. Three and 7-day data shows all mixes performed approximately equal to typical compacted granular soil. DaraFill CLSM mixes utilized kg/m 3 (1-3 lbs/yd 3 ) cementitious material, 148 kg/m 3 (25 lbs/yd 3 ) water, with air contents of 3-35% achieved through the addition of one.12 L/m 3 (3 oz/yd 3 ) DaraFill capsule. The excellent shear strength properties of DaraFill CLSM at low unit weights is enhanced by the cohesion properties of the cement.

3 Maximum Stress kg/cm 2 = (tons/ft 2 ) Fig. 1A - Direct Shear (ASTM D 38) 35.2% air Typical granular soil 2 56 day 1 7 day 3 day Normal Stress kg/cm 2 (tons/ft 2 ) Maximum Stress kg/cm 2 = (tons/ft 2 ) Fig. 1B - Direct Shear (ASTM D 38) 119 kg/m 3 (2 lbs/yd 3 ) cement, 35.1% air day 56 day 3 day Typical granular soil Normal Stress kg/cm 2 (tons/ft 2 ) Fig. 1C - Direct Shear (ASTM D 38) 119 kg/m 3 (2 lbs/yd 3 ) flyash, 3% air 6 Fig. 1D - Direct Shear (ASTM D 38) 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash, % air 6 Maximum Stress kg/cm 2 = (tons/ft 2 ) day 3 Typical granular soil day 3 day Normal Stress kg/cm 2 (tons/ft 2 ) Maximum Stress kg/cm 2 = (tons/ft 2 ) day 56 day 3 day Typical granular soil Normal Stress kg/cm 2 (tons/ft 2 ) California Bearing Ratio (ASTM D 1883) The load bearing capacity of soil and CLSM is directly related to its ability to support foundations, pavements and other structures without failing or experiencing long-term settlement. Ultimate shear resistance of soils and CLSM are largely derived from shear strength and bearing capacity factors. The California Bearing Ratio Test (ASTM D 1883), commonly know as the CBR test, is widely utilized for subbase and subgrade pavement design. Referring to Table 2 and Fig. 2, CBR testing per ASTM D1883 was conducted on 3 DaraFill CLSM and 1 reference CLSM mix. The test procedure consists of measuring the force required to penetrate the surface with a 1936 mm 2 (3 in. 2 ) piston measured at 2.5 mm (.1 in.) depth increments up to 12.7 mm (.5 in.). The resulting loaddeflection curves are then expressed as a percentage of a reference, typically standard crushed rock. CBR indexes are correlated to soil s utilizing classification systems recognized by AASHTO and USCS. Fig. 2 shows that the three DaraFill CLSM mixes tested at 3, 7 and 56 days rated a minimum very good subgrade at early ages (3 days), while all mixes rated good base or better at later ages (56 days). Fig. 3 depicts CBR indexes on the X axis and compressive strength on the Y axis and reveals a strong relationship between CBR indexes and compressive strengths exists. This relationship is valuable since it allows for compressive strength specifications to help assure adequate in-place CBR properties are achieved. Table 3 depicts typical California Bearing Ratio Indexes for several categories of soils and DaraFill CLSM. Modified (Cyclic Loading) CBR The California Bearing Ratio test was modified to compare the relative resistance of compacted fill and CLSM materials to cyclic loading. A cyclic load per unit area of MPa (1-25 psi)

4 Table 2 DaraFill CLSM California Bearing Ratio and Modified (Cyclic) CBR Cement Flyash Water Sand DaraFill Air California Modified (Cyclic) CBR kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 Bearing Ratio (%) (Strain - %) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd 3 ) (%) 3 Day 7 Day 56 Day n = 1 n = 1 n = (1) () (25) (238) (3) (35.2) 119 kg/m 3 (2 lbs/yd 3 ) cement, (2) () (25) (2295) (3) (35.1) 119 kg/m 3 (2 lbs/yd 3 ) flyash (1) (2) (25) (2168) (3) (3.) 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash (5) (25) (495) (271) () (.4) Fig. 2 California Bearing Ratio (ASTM D 1883) CBR (%) kg/m 3 cement, 35.1% air 59 kg/m 3 cement, 35.2% air 7 Specimen Age (days) 59 kg/m 3 cement, 119 kg/m 3 ash, 3.% air 3 kg/m 3 cement, 148 kg/m 3 ash, % air 56 Compressive Strength MPa (psi) Fig. 3 California Bearing Ratio (%) Versus Compressive Strength California Bearing Ratio (%) was applied to test specimens for 3 cycles with data further extrapolated to 1 cycles. These loads were used since.7 MPa (1 psi) approximates the weight of pavement and.17 MPa (25 psi) is the approximate stress exerted on base coarse just below pavement by a large commercial truck wheel. Two strain components developed during cycling: a recoverable elastic component and a plastic component, which causes deformation. The plastic deformation, or cumulative strain, increased with each cycle, but at a decreasing rate. The modified CBR test determines cumulative strain, which relates to the deformation characteristics of DaraFill CLSM. Table 2 and Fig. 4 shows results of modified CBR testing conducted on a typical compacted granular soil (dense glacial till) and two DaraFill CLSM and one reference CLSM mix designs. The results indicate both DaraFill CLSM mix designs outperformed the typical compacted granular soil and reference CLSM mix.

5 Table 3 Soil Description CBR (%) DaraFill CLSM 5-13 Base rock, well graded 6-8 Gravel, poorly graded 35-6 Gravel, uniformly graded 25-5 Silty gravel 4-8 Clayey gravel 2-4 Silty, sandy silts, gravely silts 5-15 Lean clays, sandy clays, gravely clays 5-15 Organic silts, lean organic clays 4-8 Micaceous clays, diatomaceous soils 3-5 Fat clays, organic clays 3-5 Strain (%) Fig. 4 Modified (Cyclic Loading) CBR (56 Days) 3 cycles/extrapolated to 1 cycles 1 3 kg/m 3 (5 lbs/yd 3 ) cement 148 kg/m 3 (25 lbs/yd 3 ) ash 59 kg/m 3 (1 lbs/yd 3 ) cement 1 Number of Cycles Dense Glacial Till 119 kg/m 3 (2 lbs/yd 3 ) cement 1 Testing was also done on a dry sand specimen, with results showing a magnitude higher level of strain (2.3%) compared to the other mixes. Triaxial Shear (Consolidated Drained) (USACE EM ) The most common and relevant test procedure for predicting in-place rigidity and overall strength properties of compacted fill is the triaxial shear test. Triaxial shear tests are conducted in a drained or undrained mode, depending on the water permeability properties of the fill material. Since DaraFill CLSM is porous and has relatively high permeability properties (similar to sand and gravel), a drained triaxial shear test procedure was utilized. Shear strength properties of granular material are largely dependent on the effective confining stress acting on the soil element. For many granular materials, shear strength increases linearly as effective confining stresses are increased. The Mohr- Coulomb failure law defines this linear relationship as: ff = c + ff ff = ff = c = = *tan peak shear stress on failure plane at failure, i.e. the shear strength effective normal stress on failure plane at failure cohesion, or shear strength at zero confining stress friction angle tan = coefficient of friction of the material, or slope of the linear relationship between effective normal stress at failure and the shear strength Cohesion and friction angle characteristics for granular materials are best measured by testing specimens over a range of effective confining stresses and measuring the peak shear stress, then best fitting a straight line to the data. The intercept of this straight line with the shear stress axis equals the cohesion of the material. The slope of the straight line (change in shear strength/change in normal stress) equals tan. Consolidated Drained Triaxial Compression Testing (USACE EM ) was conducted on two DaraFill CLSM mixes and one reference CLSM mix at 16 hrs, 7 days and 28 days, with 16 hour data providing guidance for determining when the hole can be topped off or backfilled. Referring to Table 4, friction angle data shows that reference and DaraFill CLSM mix designs at 16 hours have already developed friction angle values representative of well compacted fill. Both DaraFill CLSM mixes achieved minimum 38 degree friction angles at 16 hours, while typical well compacted fill achieve ultimate friction angles in the mid 3 s or higher. Cohesion values at 16 hours are negligible for the DaraFill CLSM mixes, but most compacted granular fills also have negligible cohesion properties at all ages. From 16 hours to 28 days, the excellent cohesive

6 Table 4 DaraFill CLSM Consolidated Drained Triaxial Compression (USACE EM ) Compressive Air Friction Angle Cohesion Cement Flyash Water Sand DaraFill Flow Unit Wt Strength MPa (psi) (degrees) MPa (psi) kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 mm kg/m (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd 3 ) (in.) (lb/ft 3 ) Hour Day Day (%) Hour Day Day Hour Day Day (1) () (328) (233) (3) (7.5) (12.1) (2.8) (19.8) (35.4) (25.6) (.2) (4) (6.3) 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash n/a (5) (25) (229) (2193) (3) (7.5) (99) (n/a) (18.4) (33.9) (29.5) () (3.7) (6.7) 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash (5) (25) (447) (2731) () (8) (13) (7.1) (43.8) (81) (4.3) (1.2) (3.6) (8.4) properties of the cementitious constituents begin to develop. For example, cohesion for the 59 kg/m 3 (1 lbs/yd 3 ) DaraFill CLSM mix increased from.14 MPa to.43 MPa (.2 psi to 6.3 psi). In summary, consolidated triaxial shear strength testing indicates that all DaraFill CLSM mixes tested equal to or superior to granular compacted fill at 16 hours, with further gains after 16 hours as the cohesive properties of the CLSM continue to develop. Incremental Consolidation (ASTM D 2435) A Standard Test Method for One-Dimensional Consolidation Properties of Soil (ASTM D 2435), also commonly called the Odometer Test, is utilized to help estimate both the rate and total amount of differential and total settlement for foundations and backfill. Consolidation property values are also utilized to derive bedding factors and soil stiffness values needed for pipe bedding design. Particulate materials show a relationship between vertical strain and the change in vertical stress applied in a one-dimensional consolidation test. This relationship can be used to compute vertical strain of the material and settlement resulting from a load increment as depicted below. Strain = m v * v Settlement = Strain * D m v = coefficient of volume compressibility of material measured in consolidation tests v = change in vertical stress from loading D = thickness of compressible layer Referring to Table 5, coefficient of volume compressibility of material values (mv) are depicted at 16 hours, 7 days and 28 days for two DaraFill CLSM and one reference CLSM mixes. Mv values were calculated at v loads of 1 kg/cm 2 and 4 kg/cm 2 (1 tons/ft 2 and 4 tons/ft 2 ). This data shows that mv values decrease as vertical stress is increased. The compressibility properties of DaraFill CLSM are not well developed at 16 hours, but improve as the cementitious material begins to develop strength. For backfill design, mv values should be selected based on an average vertical stress acting at the middle of the flowable fill. Typical mv values for several soils are shown below. Soil m v (ft 2 /ton) = (cm 2 /kg) Dense gravel.5-.1 Dense sand.1-.2 Dense silt.2-.4 Firm Clay.1-.3 Soft Clay Peat >.15 Thermal Conductivity (ASTM C 518) The thermal conductivity of a material is defined as the amount of heat that will flow through an object when a temperature difference exits across the object. Materials with low thermal conductivity values allow small amounts of heat flow and are called thermal insulators. Materials with large thermal conductivity values allow more heat to flow through the material under identical temperature gradients.

7 Table 5 DaraFill CLSM Incremental Consolidation (ASTM D 2435) (m v ) Coefficient of Volume Compressive Air Compressibility cm 2 /kg = (ft 2 /ton) Cement Flyash Water Sand DaraFill Flow Unit Wt Strength stress kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 mm kg/m 3 y =1 kg/cm 2 stress y = 4 kg/cm 2 MPa (psi) (stress y =1 ton/cm 2 ) (stress y = 4 ton/cm 2 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd 3 ) (in.) (lb/ft 3 ) Hour Day Day (%) Hour Day Day Hour Day Day (1) () (328) (233) (3) (7.5) (12.1) (2.8) (19.8) (35.4) (25.6) kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash n/a (5) (25) (229) (2193) (3) (7.5) (99) (n/a) (18.4) (33.9) (29.5) kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash < < (5) (25) (447) (2731) () (8) (13) (7.1) (43.8) (81) (4.3) NM NM Referring to Table 6, thermal conductivity testing was performed on three 59 kg/m 3 (1 lbs/yd 3 ) cement factor DaraFill CLSM specimens per ASTM C (Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Heat Flow Meter). The samples were tested under three conditions: oven dry (% relative humidity), saturated surface dry (SSD), and immersed in water. Results indicate that under dry and SSD conditions, the thermal conductivity characteristics for the DaraFill CLSM specimens did not vary significantly over a wide range of air contents [.42 to.48 W-m/K (2.9 to 3.4 Btu-in./ hr-f-ft 2 )]. Under immersed conditions, however, the thermal conductivity characteristics significantly increased [1.1 to 1.7 W-m/K (7.8 to 11.9 Btu-in./hr-F-ft 2 )]. Table 6 also shows typical thermal conductivity values for several soil types with data indicating that moisture content and soil type significantly impact thermal conductivity properties. In summary, DaraFill CLSM is a good thermal insulator when compared to compacted fill comprised of sand and gravel, and thermal conductivity insulation characteristics decrease as moisture contents increase. Table 6 Thermal Conductivity W/m-K (Btu-in./hr-F-ft 2 ) Sample Moisture Condition Air (%) Dry SSD Immerse (3.4).51 (3.5) 1.1 (7.8) (2.9).53 (3.7) 1.7 (11.9) (3.) n/a 1.3 (9.1) Typical Soil Thermal Conductivity* Soil 2% 2% 8% Type Moisture Moisture Moisture silts, clays.7 (.5).97(6.87) 1.5 (1.71) sands 1.1 (7.69) 2.3 (16.5) Triaxial Water Permeability (ASTM D 584) Voids in backfill materials produce interconnected, small, irregular conduits, through which water flows. The coefficient of permeability, or water permeability, expresses the rate or velocity which water flows through materials. Grain size, shape, gradation, void ratio and degree of saturation are major factors in determining permeability characteristics of soils. gravel 1.4 (9.68) 2.9 (2.77) *Thermal conductivity values derived from Kersten, M.S., Thermal Properties of Soils, University of Minnesota Institute of Technology Bulletin, No. 28, Minneapolis, MN

8 Triaxial water permeability tests per ASTM D 584 were conducted on two DaraFill CLSM and one reference CLSM mixes. The top of Table 7 shows the two DaraFill CLSM mixes having permeability values of 1.2 x 1-3 cm/sec and 1.7 x 1-3 cm/sec, with reference CLSM having a lower permeability value of 1.8 x 1-4 cm/sec. This data implies that as air contents increase, the water permeability properties of DaraFill CLSM also increase. The bottom of Table 7 shows ranges in permeability values for various classifications of soil. Air Permeability (ASTM D 4525) Standard Test Methods for Permeability of Rocks by Flowing Air (ASTM D 4525) covers procedures for determining the coefficient of specific permeability of air. This value can be used to predict the flow rate of various gases through CLSM. Referring to Table 8, air/gas permeability tests were conducted on two DaraFill CLSM and one reference CLSM mixes. Results indicate that as air contents increase, air/gas permeability rates also increase. In fact, the rate of air flow of CLSM containing 3% air is approximately 4 orders of magnitude faster Table 7 CLSM and DaraFill CLSM Triaxial Water Permeability Values Mix 1-3 kg/m 3 (5 lbs/yd 3 ) cement, 1333 kg/m 3 (2246 lbs/yd 3 ) Fine Aggregate, 123 kg/m 3 (27 lbs/yd 3 ) water, 3% air K = 1.7 x 1-2 cm/sec Mix kg/m 3 (2623 lbs/yd 3 ) Fine Aggregate, 176 kg/m 3 (297 lbs/yd 3 ) water, 21% air K = 1.2 x 1-3 cm/sec Mix 3-3 kg/m 3 (5 lbs/yd 3 ) cement, 1619 kg/m 3 (2728 lbs/yd 3 ) Fine Aggregate, 298 kg/m 3 (52 lbs/yd 3 ) water, 1.4% air K = 1.8 x 1-4 cm/sec Water Permeability Values of Soils Permeability K (cm/sec) Formation High greater than 1-1 Coarse Gravel, Rock Medium 1 x 1-1 to 1 x 1-3 Sand, Fine Sand Low 1 x 1-3 to 1 x 1-5 Silty Sand, Dirty Sand Very Low 1 x 1-5 to 1 x 1-7 Silt, Sandstone Practically Less than 1 x 1-7 Silt, Sandstone Impervious Clay, Mudstone when compared to CLSM without air (K= 18.2 m 2 versus.16 m 2 ). Freeze-Thaw (ASTM D 56) A Standard Test Method for Freezing and Thawing (ASTM D 56) of Compacted Soil- Cement Mixtures covers procedures for determining durability of soil specimens to resist repeated cycles of freezing-thawing. The test procedure is applicable for evaluating the freeze-thaw characteristics of CLSM and was conducted on two DaraFill CLSM and one reference CLSM mixes. Relative to properly air entrained 27.6 Mpa (4 psi) concrete, CLSM (and compacted fill) will possess minimal durability characteristics to resist severe freeze-thaw damage. Therefore, the freeze-thaw test for soilcement is mild (12 cycles), when compared to concrete freeze-thaw test procedures (3 cycles). Table 9 depicts results of freeze-thaw testing and shows that the DaraFill CLSM mixes (3% and 2% air content), while having significant volume loss at test completion, clearly outperformed the reference CLSM mix (1.4% air content). The reference CLSM mix suffered rapid freeze-thaw deterioration after only 3 cycles ( 1 3 of the sample broke off) and freeze-thaw testing had to be discontinued after 5 cycles because the sample continued to break apart and could not be further handled or tested.

9 These freeze-thaw test results confirm data presented in a paper written by T.E. Nantung and C.F. Scholer, titled Freezing and Thawing Durability and Early Set and Strength Development of CLSM, published by the American Concrete Institute. Conclusions drawn from the results of this work suggests increasing air content and strength will improve CLSM s ability to resist freeze-thaw cycling. Table 8 CLSM and DaraFill CLSM Air/Gas Permeability Test Results (Coefficient of gas permeability, average taken at 4 mean pressures) Mix 1-3 kg/m 3 (5 lbs/yd 3 ) cement, 1333 kg/m 3 (2246 lbs/yd 3 ) Fine Aggregate, 123 kg/m 3 (27 lbs/yd 3 ) water, 3% air K = 18.2 m 2 Mix kg/m 3 (2623 lbs/yd 3 ) Fine Aggregate, 176 kg/m 3 (297 lbs/yd 3 ) water, 21% air K = 1.3 m 2 Mix 3-3 kg/m 3 (5 lbs/yd 3 ) cement, 1619 kg/m 3 (2728 lbs/yd 3 ) Fine Aggregate, 298 kg/m 3 (52 lbs/yd 3 ) water, 1.4% air K =.16 m 2 Table 9 CLSM and DaraFill CLSM Freeze-Thaw Durability Measured as material loss (%) Mix 1-3 kg/m 3 (5 lbs/yd 3 ) cement, 1333 kg/m 3 (2246 lbs/yd 3 ) Fine Aggregate, 123 kg/m 3 (27 lbs/yd 3 ) water, 3% air Volume loss (%) 3 cycles - 13% 5 cycles - 27% 12 cycles - 81% Mix kg/m 3 (2623 lbs/yd 3 ) Fine Aggregate, 176 kg/m 3 (297 lbs/yd 3 ) water, 21% air Volume loss (%) 3 cycles - 8% 5 cycles - 2% 12 cycles - 82% Mix 3-3 kg/m 3 (5 lbs/yd 3 ) cement, 1619 kg/m 3 (2728 lbs/yd 3 ) Fine Aggregate, 298 kg/m 3 (52 lbs/yd 3 ) water, 1.4% air Volume loss (%) 3 cycles - 43% 5 cycles - 47% 12 cycles - SAMPLE DETERIORATED Electrical Resistivity (Corrosion Potential) The potential for compacted granular fill and CLSM to initiate corrosion of embedded steel pipe is related to the electrical resistivity of the backfill material, along with its ph and drainage characteristics. DaraFill CLSM has high electrical resistivity characteristics at low relative humidity, (7,5 ohm-cm), but lower values (approximately 2 ohm-cm) when saturated with water. Since DaraFill CLSM has high ph (typically 9-11), and excellent water permeability (drainage) properties (K ranging from 1.2 x 1-3 cm/sec at 2% air to 1.7 x 1-2 cm/sec at 3% air), it will have good corrosion resistance properties when utilized in applications allowing for water drainage. If DaraFill CLSM or other backfill materials are not able to freely drain, electrical resistivity properties will decrease and corrosion potential will increase. Bleeding Bleeding, or de-watering, occurs concurrently with subsidence and segregation as the heavier constituents of the CLSM fall to the bottom of the fill. Excessive bleeding and subsidence can cause significant volume loss which may necessitate pouring a second lift or topping out with CLSM. The falling out of the cementitious materials, coupled with the water rising to the top of the fill, can also result in a non-homogenous in-place material (i.e. higher strength at the bottom due to

10 high cement content, and lower strengths at the top due to high water contents). DaraFill CLSM, due to reduced water content, does not segregate, settle or bleed, resulting in a homogenous, cohesive CLSM which can be placed in one pass. Table 1 shows results of ASTM C 94 testing (Bleeding of Freshly Mixed Grouts for Preplaced Aggregate Concrete) conducted on reference CLSM and DaraFill CLSM containing 3% air. The inclusion of 3% air in the mix resulted in no measurable bleed water, while reference non-air entrained CLSM measured 2.4% bleed water at the top of the sample. Pipe Backfill Design Parameters Buried rigid and flexible pipe depend on the support of the surrounding embedment to safely carry the loads imposed by overburden and surface vehicles. The most important areas of support include the bedding, where vertical loads must be supported, and the sidefill, where a soil reaction develops to prevent a pipe from deflecting outward. The haunch zone is also a critical support area since it contributes both to carrying vertical load and resisting lateral deformations. Triaxial Shear (Consolidated Drained) and Incremental Consolidation test results provide strength and stiffness data which correlate to the quality of support provided by DaraFill CLSM to rigid and flexible pipe. Methods developed by Duncan (198) and Selig (1988) use this data to develop an elasticity model for finite element analysis of pipe installations to evaluate DaraFill CLSM. Traditional parameters for pipe backfill design can thereby be developed for DaraFill CLSM. Simpson, Gumpertz, & Heger Inc., Consulting Engineers, Arlington, MA provided this analysis from finite element studies and prior experience with buried pipe installations. The rigid pipe backfill analysis described below was based on using DaraFill CLSM to the springline, while flexible pipe analysis was based on using DaraFill CLSM to the top of the pipe. Analysis was done in Table 1 ASTM C 94 - Bleeding of Freshly Mixed Grouts for Preplaced-Aggregate Concrete 3 kg/m 3 (5 lbs/yd 3 ) cement, 1333 kg/m 3 (2246 lbs/yd 3 ) Fine Aggregate, 123 kg/m 3 (27 lbs/yd 3 ) water 3% air - % Bleed 3 kg/m 3 (5 lbs/yd 3 ) cement, 1619 kg/m 3 (2728 lbs/yd 3 ) Fine Aggregate, 298 kg/m 3 (52 lbs/yd 3 ) water 1.4% air - 2.4% Bleed this manner since rigid pipe performance is more sensitive to bedding support than lateral pressure. For both rigid and flexible pipe, optimal performance will result when the entire trench is filled with DaraFill CLSM. Rigid Pipe-Bedding Factors Available load bearing capacity or strength (W teb ) of rigid pipe is determined by a three-edge bearing test, which utilizes a concentrated load condition and is more severe than actual in-ground loadings. The load applied to a pipe underground (W e ) is related to the required three-edge bearing strength for a pipe to work under those conditions by the bedding factor (B f ): (W teb )=(W e )/(B f ): Table 11 depicts recommended bedding factors for two DaraFill CLSM mixes for both trench and embankment types of installations. Comparisons to traditional Class A, B, C and D type beddings and the new ASCE (SIDD) beddings are also included. Suggested bedding factors for the two DaraFill CLSM mixes increased from 16 hours to 28 days due to gains in the cohesive properties of the cementitious material. For both trench and embankment design, however, 16 hour suggested bedding factors are already equivalent to well compacted typical granular fill. At 28 days, suggested bedding factors are excellent, superior to a ASCE (SIDD) Type 1 coarse grained bedding

11 Table 11 Suggested Bedding Factors - Rigid Pipe Backfill Design Suggested Bedding Factors Cement Flyash Water Sand DaraFill Flow Unit Wt Air kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 mm kg/m 3 Trench-DaraFill CLSM age Embankment-DaraFill CLSM age (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd 3 ) (in.) (lb/yd 3 ) (%) Hour Day Day Hour Day Day DaraFill CLSM (1) () (328) (233) (3) (7.5) (12) (25.6) to 2.8 to 3.4 to 4.8 DaraFill CLSM 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash (5) (25) (229) (2193) (3) (7.5) (99) (29.5) to 2.8 to 3.4 to 4.8 Traditional Bedding Materials Trench Embankment Class A - Concrete Cradle 2.8 to to 5. Class B - Densely compacted granular backfill, uniform bedding support to 2.8 Class C - Lightly compacted backfill, partial bedding support to 2.3 Class D - Loose backfill, flat bedding to 1.3 ASCE (SIDD) Type Beddings Trench-Compaction Level Embankment-Compaction Level 85% 9% 95% 85% 9% 95% Type 1-coarse grained to 4.4 Type 2-coarse grained to 3.2 Type 2-Silt to 3.2 Type 3-coarse grained to 2.5 Type 3-Silt to 2.5 Type 3-Clay to 2.5 Type 4-Clay and in the Class A Concrete Cradle category. These results clarify that DaraFill CLSM can be effectively utilized as a backfill material to provide stiff uniform support to buried pipe. The excellent flowability of DaraFill CLSM further assures uniform and continuous support in the critical bedding, sidefill and haunch zones. Flexible Pipe-Modulus of Soil Reaction, E Flexible pipes rely on pipe backfill to resist deflection, defined as change in vertical pipe diameter. The most common method used to calculate the deflection of pipe under load is the Iowa formula (Spangler, 1941). v = D 1 KW E / (EI/r 3 ) +.61E v = change in vertical pipe diameter, m (in) D 1 = deflection lag factor K = bedding factor W E = load on pipe, kn/m (lbs/in) E = modulus of elasticity of pipe material, kpa (psi) I = moment of inertia of pipe wall per unit length of pipe, m 4 /m (in 4 /in) r = mean radius of pipe, m (in) E = modulus of soil reaction, kpa, (psi) 1. A minimum bedding factor, K, of.83 should be used for DaraFill CLSM since it should provide full uniform support to the lower half of the pipe. 2. Current work indicates that the load on flexible pipe W e should be determined in the same manner as current practice. 3. EI/r 3 represents pipe stiffness and is not affected by the use of DaraFill CLSM as backfill. 4. The deflection lag factor, D 1 accounts for increases in deflection that occur over time. Since no data exists for CLSM current practice for determining D 1 should be used.

12 Table 12 Modulus of Soil Reaction Values (E ) Cement Flyash Water Sand DaraFill Flow Unit Wt Air DaraFill CLSM AGE kg/m 3 kg/m 3 kg/m 3 kg/m 3 L/m 3 mm kg/m 3 16 Hour 7 Day 28 Day (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (lb/yd 3 ) (oz/yd 3 ) (in.) (lb/yd 3 ) (%) E - kpa (psi) DaraFill CLSM (1) (2) (3) (1) () (328) (233) (3) (7.5) (12) DaraFill CLSM 3 kg/m 3 (5 lbs/yd 3 ) cement, 148 kg/m 3 (25 lbs/yd 3 ) flyash (1) (2) (3) (5) (25) (229) (2193) (3) (7.5) (99) Compaction Level 85% 9% 95% Soil Category E - kpa (psi) Crushed Stone (1) (3) (3) Coarse grained with little or no fines (2) (2) (3) Coarse grained with fines or fine grained with low plasticity and greater than 25% coarse particles (1) (1) (2) Fine grained soils with low plasticity and less than 25% coarse particles (5) (4) (1) The modulus of soil reaction, E, is actually an empirical parameter and represents the stiffness of soil support at the sides of the pipe. Calculations with the same elastic properties that were used for the rigid pipe evaluation indicate the values of the modulus of soil reaction, E, depicted in Table 12 for two DaraFill CLSM mixes, can be used in the above equation to estimate the deflection of pipe embedded in DaraFill CLSM. In accordance with common practice, E values are single values. For purposes of comparison, E values for typical compacted fills are also included in Table 12. Modulus of soil reaction values (E ) increased for the 2 DaraFill CLSM mixes from 16 hours to 28 days due to gains in the cohesive properties of the cementitious material. At 16 hours, E values for both DaraFill CLSM mixes are equal to 85% compacted crushed stone and at 28 days E values are equal to 95% compacted crushed stone. NOTE: The bedding factor and modulus of soil reaction values presented here are for consideration by engineers when specifying DaraFill CLSM. Actual installations include many variables that the designer must take responsibility for assessing when selecting design values. North American Customer Service: AD-MIX1 ( ) Visit our web site at: printed on recycled paper W. R. Grace & Co.-Conn. 62 Whittemore Avenue Cambridge, MA 214 DaraFill is a registered trademark of W. R. Grace & Co.-Conn. We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate and is offered for the users consideration, investigation and verification, but we do not warrant the results to be obtained. Please read all statements, recommendations or suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation or suggestion is intended for any use which would infringe any patent or copyright. W. R. Grace & Co.-Conn., 62 Whittemore Avenue, Cambridge, MA 214. In Canada, Grace Canada, Inc., 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6. This product may be covered by patents or patents pending. Copyright 22. W. R. Grace & Co.-Conn. DF-6A Printed in U.S.A. 7/2 FA/GPS/1.5M