Center for By-Products Utilization

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1 Center for By-Products Utilization NO-FINES CONCRETE USING OFF-SPECIFICATION COAL COMBUSTION PRODUCTS By Tarun R. Naik, Rudolph N. Kraus, Yoon-moon Chun, and Francois D. Botha Report No. CBU REP-491 May 2003 For Publication and Presentation at the Eighth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Las Vegas, May 23-29, Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN MILWAUKEE

2 NO-FINES CONCRETE USING OFF-SPECIFICATION COAL COMBUSTION PRODUCTS by T. R. Naik (corresponding author) Director, UWM Center for By-Products Utilization Department of Civil Engineering and Mechanics College of Engineering and Applied Science University of Wisconsin-Milwaukee P. O. Box 784 Milwaukee, WI Tel: (414) Fax: (414) R. N. Kraus Assistant Director, UWM Center for By-Products Utilization Y. Chun Postdoctoral Fellow, UWM Center for By-Products Utilization and F. D. Botha Project Manager, Illinois Clean Coal Institute 5776 Coal Drive, Suite 200 Carterville, IL Tel: (618) Fax: (618) MS #LV55

3 i No-Fines Concrete Using Off-Specification Coal Combustion Products by T. R. Naik 1, R. N. Kraus 2, Y. Chun 3, and F. D. Botha 4 ABSTRACT No-fines porous concrete mixtures were made in the laboratory and field by replacing up to about 30 % of cement and 2 % of coarse aggregate with a mixture of high-carbon (33 %), wetcollected coal bottom ash and fly ash (CCPs, coal combustion products). Overall, the average 28-day compressive, splitting tensile, and flexural strengths were approximately 7.0, 1.1, and 1.2 MPa, respectively. Laboratory mixtures incorporating the CCPs showed either equivalent or higher compressive and splitting tensile strengths, higher flexural strength, and lower freezingand-thawing resistance compared with a control mixture without the CCPs. Field mixtures incorporating the CCPs generally showed lower strengths and freezing-and-thawing resistance compared with a control mixture. However, the field mixture made with 20 % replacement of cement with the CCPs was equivalent to the control mixture in splitting tensile strength at all test ages, in flexural strength from 28 days, and in resistance to 50 cycles of freezing and thawing. Keywords: bottom ash, compressive strength, flexural strength, fly ash, high-carbon coal ash, no-fines concrete, permeable base, porous concrete, freezing and thawing, splitting tensile strength. 1 Director, 2 Assistant Director, 3 Postdoctoral Fellow, UWM Center for By-Products Utilization, Department of Civil Engineering and Mechanics, College of Engineering and Applied Science, University of Wisconsin-Milwaukee, Milwaukee, WI, USA. 4 Project Manager, Illinois Clean Coal Institute, Carterville, IL, USA.

4 1 INTRODUCTION Past investigations have established that drainage under rigid (concrete) or flexible (asphaltic) pavements is required in producing durable pavements [1, 2]. To help solve drainage problem, open-graded porous bases can be used [2, 3]. A properly designed and constructed porous base eliminates pumping, faulting, and cracking in pavements. Therefore, a porous base must be capable of maintaining both permeability and stability. It is estimated that the use of a porous base would increase pavement service life by up to 70 % for portland cement concrete and asphaltic pavements [1]. Due to the large size of the pores, no-fines concrete is not subject to capillary suction [4]. Therefore, no-fines concrete is highly resistant to freezing and thawing, provided that the pores are not saturated; if saturated, freezing would cause deterioration. The water absorption can be as high as 25 % by volume. This research was conducted to develop no-fines, non-air-entrained, porous concrete mixtures using difficult-to-recycle high-carbon coal ash. LITERATURE REVIEW Porous bases are divided into two classes: treated and untreated. A treated porous base employs a binder, which typically consists of either cement or asphalt. An untreated base contains more smaller-size aggregates in order to provide stability through aggregate interlock. In order to have improved stability, an untreated base should contain 100 % crushed aggregate [5]. A cement-treated porous base is typically composed of 85 % aggregate, 10 % cement, and 5 % water by mass [6]. The coefficient of permeability for treated base depends upon several factors such as aggregate gradation and binder content. Due to the coarse gradation and small amount of binder used in manufacture of treated base, they are by design quite porous. The

5 2 coefficient of permeability for the untreated porous base is normally lower than that for the treated porous base due to greater amount of fines. As a paving material, porous concrete is raked or slip-formed into place with conventional spreader or paving equipment and then roller compacted, similar to asphaltic pavement. Vibratory screeds or hand rollers can be used for confined spaces or smaller project work. In order to maintain porous properties, the surfaces should not be closed or sealed; therefore, troweling and finishing are not desired. The compressive strength of different mixtures typically ranges from 3.5 to 28 MPa at 28 days [3]. Drainage rates commonly range from 80 to 700 L/min./m 2 [7]. A porous base system is composed of three major elements: permeable base, separator or filter layer, and edge drain system. Information on design, construction, and material requirements are available in the literature [3, 5, 6, 8-12]. Various parameters such as cross slope, longitudinal grade, and drainage-layer width and thickness can influence the permeability and performance of open-graded porous materials [2]. Although the thickness of porous bases generally varies between 100 to 300 mm, a 200 mm thickness of the porous base is the most commonly used [2, 13, 14]. Factors such as cement content, truck traffic, sublayer stability, segregation, and surface irregularities are important in affecting performance of the porous material [15]. Based on investigations in California [12, 16], a minimum life increase was estimated to be 33 % for asphaltic pavement and 50 % for portland cement concrete pavement incorporating porous bases compared to undrained pavements. Studies conducted by several state agencies in the USA were summarized by Munn [16]. Two eight-year-old pavements on porous bases in California did not exhibit any cracking, whereas corresponding undrained pavements showed 18

6 3 % and 47 % cracking. Nondestructive testing of porous base pavements in Iowa revealed a greater support relative to undrained pavements. The increased support was equivalent to a thickness of 75 to 125 mm of additional pavement. In Michigan, porous-base test sections built in 1975 did not show any faulting or cracking and had less D-cracking compared to control sections of bituminous and dense-graded sections. In Minnesota, a jointed reinforced concrete pavement on porous base built in 1983 experienced only one mid-panel crack in its 59 panels, while undrained sections adjacent to either end showed 50 % mid-panel cracks. Performance of Pennsylvania s porous base sections built in was rated much better than that of densegraded aggregate sections. In Pennsylvania, a porous base between portland cement concrete pavement and the dense-graded aggregate subbase was standardized in Wisconsin [17] estimates that the use of a cement-stabilized base would add 25 % more service life to concrete pavements. Recent nondestructive testing in Iowa [18] has shown excellent performance of porous base pavements. New Jersey [10] found similar rutting for porous base pavements constructed in for either thicker or thinner sections. Also, there was less deflection, no faulting or pumping, and reduced frost penetration on concrete pavements. In 1990, porous base concrete pavement became standard in nine different states [6]. The use of porous bases is rapidly increasing in the USA. EXPERIMENTAL PROCEDURES Materials ASTM Type I portland cement was used in this research. A mixture of wet-collected coal bottom ash and fly ash (CCPs) obtained from combustion of Illinois basin coal, Illinois, USA, was used. In a typical porous concrete mixture produced in this research, one-half of the coal ash added was considered to be a replacement for a part of cement (up to 32 %), and the

7 4 other half of the ash was considered to be a replacement for a small portion of coarse aggregate (up to 2 %). Physical and chemical properties of the ash are presented in Tables 1 and 2, respectively. The as-received moisture content of the ash ranged between 10 % and 20 %, and the carbon content was about 33 %. Grading of the ash is shown in Table 3. Only 12 % by mass of the ash passed 150 μm sieve. Two different sources of coarse aggregates, both with a nominal maximum size of 19 mm, were used. A crushed limestone aggregate meeting the grading requirement of ASTM C 33 was used in laboratory concrete mixtures, and a natural river gravel meeting the grading requirement of Illinois Department of Transportation (IDOT) was used in the field concrete mixtures. Properties of the coarse aggregates are shown in Tables 3 and 4. Manufacturing of Laboratory Mixtures Before field manufacturing, porous concrete mixtures were made in the laboratory to establish preliminary mixture proportions and to determine performance of the mixtures. Laboratory mixing procedures followed those outlined in ASTM C 192 for mixing concrete in the laboratory. Manufacturing of Field Mixtures All ingredients were batched and mixed at a ready-mixed concrete plant in Peoria, Illinois, USA. Coarse aggregate, cement, and water were automatically batched into a central mixer. Coal ash was loaded directly into the ready-mixed concrete truck, and then the remaining auto-batched materials were added from the central mixer. After all materials were added to the truck, they were mixed at the maximum mixing speed until 70 revolutions were completed. Transportation time to a typical job site was then simulated by mixing at transit speed for approximately 10 minutes. Then the porous concrete mixture was discharged for density testing and for casting of test specimens.

8 5 Specimen Preparation All test specimens were cast in accordance with ASTM C 1435 Standard Practice for Molding Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Hammer. The specimens were compacted using a vibrating hammer having a mass of 10 kg. Either a circular tamping plate for compaction of cylinders or a rectangular plate for compaction of beams was attached to the shaft of the vibrating hammer. Each lift of concrete was compacted in the molds for minimum 10 seconds. For each porous base course mixture, 100 x 200 mm cylinders were prepared for determination of compressive strength (ASTM C 39) and splitting tensile strength (ASTM C 496); and 75 x 100 x 400 mm beams were prepared for determination of flexural strength (ASTM C 78) and resistance to freezing and thawing (modified ASTM C 1262). For evaluation of resistance to freezing and thawing, porous concrete beams in saturated surface-dry condition were subjected to a total of 50 cycles of freezing to negative 17 ± 5 C and thawing to positive 24 ± 5 C. The mass losses of the beams due to freezing and thawing were determined every 10 cycles. Specimens cast in the laboratory were demolded one day after casting, and cured in a standard moist-curing room maintained at 100 % relative humidity and 23 ± 1.5 C, until the time of testing. Specimens cast in the field were typically initially cured for six to seven days in their molds at about 23 ± 5 C at the location of the specimen preparation at the ready-mixed concrete plant. Then, they were brought to the laboratory, demolded, and cured in the moistcuring room.

9 6 RESULTS AND DISCUSSION Laboratory Concrete Mixtures A total of four porous concrete mixtures were produced in the laboratory (Table 5) to establish performance characteristics of the porous base concrete mixtures before production in the field. One-half of the coal ash replaced up to 27 % of cement by mass, and the other half of the ash replaced up to 2 % of coarse aggregate by mass. All base course concrete mixtures made in the laboratory exhibited satisfactory levels of compressive strength (Fig. 1). The 28-day compressive strength values of Mixtures L0, L9, L18, and L27 were about 6.1, 7.1, 9.1, and 6.2 MPa, respectively. All mixtures produced higher strength than the minimum desired strength of 5.5 MPa at 28 days. Mixture incorporating the ash exhibited either equivalent or higher compressive strength compared to the control mixture at all test ages. Peak compressive strength was achieved at 18 % cement replacement by CCPs at all test ages. The average 28-day splitting tensile and flexural strengths of laboratory porous concrete mixtures were both about 1.1 MPa (Figs. 2, 3). Splitting tensile strength of the porous concrete incorporating the ash was approximately equal to or exceeded that of the control mixture at all test ages (Fig. 2). The 28-day splitting tensile strength values of Mixtures L0, L9, L18, and L27 were about 1.1, 1.0, 1.2, and 1.0 MPa, respectively. At the 28-day age, peak splitting-tensile strength was achieved at 18 % cement replacement by CCPs. Flexural strength of the concrete mixtures incorporating the ash was higher than that of the control mixture at all test ages. As the CCPs content increased, the flexural strength increased at early test ages. The 28-day flexural strength values of Mixtures L0, L9, L18, and

10 7 L27 were about 0.9, 1.3, 1.2, and 1.1 MPa, respectively. At the 28-day age, peak flexural strength was achieved at 9 % cement replacement by CCPs. At the end of 50 cycles of freezing and thawing, cumulative mass loss values of Mixtures L0, L9, L18, and L27 were 0.16, 0.40, 0.76, and 0.55 %, respectively, of the original mass of concrete (Fig. 4). The results were evaluated as a comparison of the performance between the various porous concrete mixtures. In general, concrete with higher ash content showed lower resistance to freezing and thawing (which meant, higher mass loss). Mixtures containing CCPs had higher mass loss than the 0 % CCPs mixture. Field Concrete Mixtures A total of three porous concrete mixtures were produced in the field (Table 6). One-half of the coal ash replaced up to 32 % of cement, and the other half of the ash replaced up to approximately 2 % of coarse aggregate by mass. The average 28-day compressive, splitting tensile, and flexural strengths of the field porous concrete mixtures were about 6.8, 1.2, and 1.2 MPa, respectively (Figs. 5, 6, 7). At all test ages, compressive strength of field porous concrete mixtures decreased as the amount of ash increased and as the amount of cement decreased (Fig. 5). This trend is different from that observed for laboratory mixtures, and the reason for this is not known. The 28-day compressive strength values of Mixtures F0, F20, and F32 were about 9.8, 6.9, and 3.8 MPa, respectively. Mixtures F0 and F20 produced higher strength than the minimum desired 28-day strength of 5.5 MPa. From early test ages, splitting tensile strength of Mixture F20 was equivalent to that of the Control Mixture F0 (Fig. 6). At all test ages, Mixture F32 showed about 30 % lower splitting

11 8 tensile strength than the Control Mixture F0. The 28-day splitting tensile strength values of Mixtures F0, F20, and F32 were about 1.3, 1.3, and 0.9 MPa, respectively. At early ages, Mixtures F20 and F32 showed lower flexural strength values than the Control Mixture F0 (Fig. 7). From 28 days, the flexural strength of Mixture F20 became equivalent to that of the Control Mixture F0. The 28-day flexural strength values of Mixtures F0, F20, and F32 were about 1.4, 1.2, and 0.9 MPa, respectively. At 91-day test age, flexural strength of Mixture F32 was equivalent to that of the Control Mixture F0. At the end of 50 cycles of freezing and thawing, cumulative mass loss values of Mixtures F0, F20, and F32 were 0.69, 0.96, and 3.43 %, respectively (Fig. 8). Concrete with higher ash content showed lower resistance to freezing and thawing (higher mass loss). Compared with the Control Mixture F0, the cumulative mass loss of Mixture F20 was noticeably higher at about 30 and 40 cycles of freezing and thawing, but was only slightly higher at the end of 50 cycles of freezing and thawing. CONCLUSIONS Based on the results of this research, the following conclusions may be drawn: 1. No-fines porous concrete mixtures made in the laboratory with up to 27 % of cement and two % of coarse aggregate replaced with a high-carbon, wet-collected CCPs exhibited either equivalent or higher compressive strength, equivalent splitting tensile strength, higher flexural strength, and lower freezing-and-thawing resistance compared with the control mixture made without the ash. 2. No-fines concrete mixtures made in the field with up to 20 % of cement and 1.4 % of coarse aggregate replaced with the ash exhibited lower compressive strength, equivalent splitting tensile strength, generally lower flexural strength, and equivalent resistance to 50 cycles of

12 9 freezing and thawing compared with the control mixture. At higher replacement level, strengths as well as the freezing-and-thawing resistance was lower. 3. A high-carbon, off-specification coal ash could be successfully used as a replacement for up to approximately 20 % of cement in producing no-fines porous concrete base for pavements. REFERENCES 1. Cedergren, H. R., America s Pavement: World s Longest Bathtubs, Civil Engineering, September 1994, pp Crovetti, J. A. and Dempsey, B. J., Hydraulic Requirements of Permeable Bases, Transportation Research Record, No. 1425, National Research Council, Washington DC, 1993, pp Naik, T. R and Ramme, B. W., Roller Compacted No-Fines Concrete Containing Fly Ash for Road Base Course, Proceedings of the third CANMET/ACI International Symposium on Advances in Concrete Technology, Auckland, New Zealand, August Meininger, R. C., No-fines Pervious Concrete for Paving, Concrete International, Vol. 10, No. 8, 1988, pp Baumgardner, R. H., Overview of Permeable Bases, Materials Performance and Prevention of Deficiencies and Failures, 92 Materials Engineering Congress, ASCE, New York, 1992, pp Kozeliski, F. A., Permeable Bases Help Solve Pavement Drainage Problems, Concrete Construction, September 1992, pp Kosmatka, S. H. and Panarese, W. C., Design and Control of Concrete Mixtures, Portland Cement Association, Skokie, IL, Thirteenth Edition, 1988, pp. 192, 194, and 195.

13 10 8. Zhou, H., Moore, L., Huddleston, J., and Grower, J., Determination of Free-Draining Base Material Properties, Transportation Research Record, No. 1425, National Research Council, 1993, pp Mathis, D. M., Design and Construction of Permeable Base Pavement, FHWA, U.S. Department of Transportation, Mathis, D. M., Permeable Base Design and Construction, Proceedings of the Fourth International Conference on Concrete Pavement Design and Rehabilitation, Purdue University, 1989, pp Grogan, W. B., User s Guide: Subsurface Drainage for Military Pavements, A Final Technical Report submitted to US Army Corps of Engineers, USAE Waterway Experiment Station, Vicksburg, MS, Forsyth, R. A., Wells, G. K., and Woodstrom, J. H., The Road to Drained Pavements, Civil Engineering, March 1989, pp Strohm, W. E., Nettles, E. M., and Calhoun, C. C., Jr., Study of Drainage Characteristics of Base Course Materials, Highway Research Record, No. 203, National Research Council, Washington DC, 1967, pp Moynahan, T. J., Jr., and Steinberg, Y. M., Effects on Highway Subdrainage of Gradation and Direction of Flow Within a Densely Graded Base Course Material, Transportation Research Record, No. 497, National Research Council, Washington DC, 1974, pp Hall, M., Cement Stabilized Open Graded Base: Strength, Testing, and Field Performance Versus Cement Content, Wisconsin Concrete Pavement Association, November Munn, W. D., Behind the Shift to Permeable Bases, Highway and Heavy Construction, July 1990, pp

14 Hall, M. J., Cement Stabilized Permeable Bases Drain Water, Add Life to Pavements, Roads and Bridges, September 1994, pp Brown, D., Highway Drainage Systems, Roads and Bridges, February 1996, pp. 34,

15 12 Table 1. Physical Properties of Ash Analysis Parameter CCPs ASTM C 618 Class F Class C Fineness, amount retained when wet-sieved on 45 µm sieve (%)* Strength Activity Index with Cement (% of Control)* 3-day 7-day 14-day 28-day Water Requirement (% of Control)* Specific Gravity * Material finer than 150 µm used for test. Table 2. Chemical Properties of Coal Ash Analysis Parameter (%) CCPs ASTM C 618 Class F Class C Silicon Dioxide, SiO Aluminum Oxide, Al 2 O Iron Oxide, Fe 2 O SiO 2 + Al 2 O 3 + Fe 2 O Calcium Oxide, CaO Magnesium Oxide, MgO Titanium Oxide, TiO Potassium Oxide, K 2 O Sodium Oxide, Na 2 O Sulfur Trioxide, SO Loss On Ignition (LOI) at 750 C * 6.0 Moisture Content Available Alkalies, Equivalent Na 2 O * The use of Class F pozzolan containing up to 12.0 % LOI may be approved by the user if either acceptable performance records or laboratory test results are made available. Optional requirement for the ash to be used in controlling alkalisilica reaction.

16 13 Sieve Opening Size Table 3. Grading of Coarse Aggregate and CCPs Crushed Stone for Lab Mixtures Amounts Finer than Each Sieve, % by mass Results Requirements for Aggregates Gravel CCPs ASTM C IDOT for Field 33 for for Mixtures Coarse Coarse ASTM C 33 for Fine Agg. Agg.* Agg mm mm mm mm mm mm mm μm μm μm * For nominal size of 19.0 to 4.75 mm. Illinois Department of Transportation. Table 4. Bulk Density and Specific Gravity of Coarse Aggregates Source Dry-Rodded Bulk Density (kg/m 3 ) Dry Bulk Specific Gravity SSD Bulk Specific Gravity SSD Absorption (%) Crushed Stone for Lab Mixtures Gravel for Field Mixtures

17 14 Table 5. Mixture Proportions of Laboratory Porous Base Concrete Mixtures Mixture Designation L0 L9 L18 L27 Cement Replacement with CCPs (%) Coarse Agg. Replacement with CCPs (%) Cement (kg/m 3 ) Coal Ash, dry basis (kg/m 3 ) Coarse Aggregate, SSD basis (kg/m 3 ) Water (kg/m 3 ) w/cm* Density (kg/m 3 ) * One-half of the CCPs considered for w/cm calculations Table 6. Mixture Proportions of Field Porous Base Concrete Mixtures Mixture Designation F0 F20 F32 Cement Replacement with CCPs (%) Coarse Agg. Replacement with CCPs (%) Cement (kg/m 3 ) Coal Ash, dry basis (kg/m 3 ) Coarse Aggregate, SSD basis (kg/m 3 ) Water (kg/m 3 ) w/cm* Density (kg/m 3 ) * One-half of the CCPs considered for w/cm calculations

18 Splitting Tensile Strength, MPa Compressive Strength, MPa days 7 days 3 days Cement Replacement with CCPs, % Fig. 1. Compressive strength of laboratory porous concrete mixtures Cement Replacement with CCPs, % 28 days 7 days 3 days Fig. 2. Splitting tensile strength of laboratory porous concrete mixtures

19 Cumulative Mass Loss, % Flexural Strength, MPa Cement Replacement with CCPs, % 28 days 7 days 3 days Fig. 3. Flexural strength of laboratory porous concrete mixtures Freezing and Thawing Cycles L27 L18 L9 L0 Fig. 4. Mass loss of laboratory porous concrete mixtures due to freezing and thawing

20 Splitting Tensile Strength, MPa Compressive Strength, MPa Cement Replacement with CCPs, % 91 days 28 days 7 days 3 days Fig. 5. Compressive strength of field porous concrete mixtures Cement Replacement with CCPs, % 91 days 28 days 7 days 3 days Fig. 6. Splitting tensile strength of field porous concrete mixtures

21 Cumulative Mass Loss, % Flexural Strength, MPa days 28 days 7 days 3 days Cement Replacement with CCPs, % Fig. 7. Flexural strength of field porous concrete mixtures Freezing and Thawing Cycles F32 F20 F0 Fig. 8. Mass loss of prototype field porous concrete mixtures due to freezing and thawing