Abstract:
A mixture consisting essentially of fly ash and cement kiln dust which reacts at ambient temperature with water to produce a durable mass.

Description:
This application is a division of application Ser. No. 654,211, filed Feb. 2, 1976, now U.S. Pat. No. 4,018,617. 
     This invention relates to materials which are capable of supporting surfacing such as pavement bases. 
    
    
     BACKGROUND OF THE INVENTION 
     In road paving, at one time it was thought that the base for the surfacing material should comprise a granular or gravel base. However, more recently, it has been concluded that there was a considerable difference in the performance between such bases and cement-aggregate or bituminous (asphalt)-aggregate bases. As reported in the Highway Research Board Special Report 61E, titled The AASHO Road Test, Report 5, Pavement Research, publication 954 of National Academy of Sciences-National Research Council, there is a clear superiority of such treated bases over untreated bases. In recent years, treated bases have become commonly known as stabilized bases. 
     In subsequent work, for example, use of asphalt mixtures in all courses of pavement above the subgrade has been proposed, The Asphalt Institute, Information Series No. 146, June 1968. Asphalt stabilized bases have become the most dominant stabilized base utilized to support a flexible surfacing such as asphalt concrete. In addition, asphalt concrete has found extensive use as a resurfacing material for concrete pavement. 
     It has also been proposed that a lime-fly ash-aggregate stabilized base be used in road paving. Such a base consists of a mixture of proper quantities of lime, fly ash, and graded aggregate at optimum moisture content, in which the stability is greatly enhanced by the cementing action which results from complex chemical reactions between the lime and the fly ash in the presence of water. 
     Stabilized bases are usually employed as base courses under wearing surfaces such as hot mixed, hot laid asphaltic concrete. A wearing surface is necessary to resist the high shearing stresses which are caused by traction, but the stabilized base provides the required stability to support wheel loads. 
     A serious obstacle to the expanded use of stabilized bases is the high energy costs for making the materials. 
     For example, it is well known that the production of portland cement which is used in stabilizing bases requires substantial quantities of coal in manufacture. In fact, the United States Department of Transportation has suggested that fly ash be substituted for a portion of the portland cement utilized in concrete or cement-aggregate bases, Federal Highway Administration Notice N5080.4, Jan. 17, 1974. 
     The use of asphalt in asphalt-aggregate bases which is derived from petroleum processing not only utilizes petroleum which is in short supply but also requires high energy to produce them. 
     Similarly, the lime, fly ash and graded aggregate stabilized bases utilize lime which requires coal in production. Such bases have been used in limited geographical areas of the United States where they can compete economically because of availability of lime and fly ash. 
     Thus, the predominantly used stabilized bases utilize materials that are in short supply and require substantial quantities of energy to produce them. The materials may be termed energy intensive. There is a need to avoid or minimize the use of such energy intensive materials in road paving. 
     Accordingly, among the objects of the invention are to provide a mixture of materials for producing a stabilized base comprising a hard, strong, durable mass capable of supporting surfacing which avoids or minimizes the use of materials which are energy intensive and, moreover, utilizes materials that normally are waste materials that are readily available. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, the mixture consists essentially of fly ash and cement kiln dust which reacts at ambient temperature with water to produce a durable mass. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-3 are curves of compressive strength versus age at test for various compositions. 
     FIG. 4 is curves of energy requirements for various pavement materials. 
    
    
     DESCRIPTION 
     In accordance with the invention, the pozzolanic load supporting composition utilizes cement kiln dust. 
     The solid waste generated by cement manufacture is primarily kiln dust. This dust contains a mixture of raw kiln feed, partly calcined material, finely divided cement klinker and alkali sulfates (usually sulfates). There is economic value in returning the dust to the kiln, but when the alkali content of the returned dust is too high for the product klinker to meet specifications, the dust must be discarded. Up to about 15% of the raw materials processed may be collected as dust and of this about half may be low enough in alkalis to be returned to the kiln. The rest is usually stockpiled as a waste material which must be disposed and may be a nuisance and possibly a hazard. 
     Although the chemical reactions occurring in the resultant cement kiln dust are not well known, typical cement kiln dust has a chemical analysis as follows: 
     SiO 2   
     Al 2  O 3   
     Fe 2  O 3   
     CaO 
     MgO 
     SO 3   
     Na 2  O 
     K 2  O 
     Loss Ignition 
     More specifically, typical cement kiln dust may have the following analyses: 
     
         __________________________________________________________________________ Source     Source         Source             Source                 Source                     Source                         Source                             Source                                 Source                                     Mid-Ingredient A   B   C   D   E   F   G   H   I   Range__________________________________________________________________________SiO.sub.2 28.5%     6.0%         22.4%             11.2%                 13.0%                     23.5%                         14.8%                             14.6%                                 14.7%                                     17.2%Al.sub.2 O.sub.3 9.6 3.4 4.71             3.2 4.0 3.77                         3.4 3.4 3.7 6.4Fe.sub.2 O.sub.3 5.9 0.8 1.77             1.4 5.0 1.71                         2.2 2.2 3.0 3.4CaO   50.1     16.0         65.0             48.8                 47.2                     61.3                         47.3                             46.3                                 46.5                                     40.5MgO   3.4 0.8 2.60             2.1 1.2 4.83                         2.1 2.0 2.0 2.8SO.sub.3 26.3     0.7 1.12             2.4 13.6                     1.48                         4.8 5.0 8.2 13.5Na.sub.2 O 3.18     0.08         0.24             0.2 0.45                     0.24                         0.9 0.9 0.8 1.6K.sub.2 O 26.23     1.08         1.3 4.2 2.9 1.85                         4.1 5.1 3.0 13.7Loss onIgnition 32.0%     7.7%         2.50%             26.6%                 12.9%                     1.84%                         21.1%                             21.4%                                 18.2%                                     17.2%__________________________________________________________________________ 
    
     
         ______________________________________RANGEIngredient   Low %       High %      Average %______________________________________SiO.sub.2   6.0         28.5        16.5Al.sub.2 O.sub.3   3.2         9.6         4.35Fe.sub.2 O.sub.3   0.8         5.9         2.66CaO     16.0        65.0        47.6MgO     0.8         4.83        2.34SO.sub.3   0.7         26.3        7.07Na.sub.2 O   0.08        3.18        0.78K.sub.2 O   1.08        26.23       5.52Loss onIgnition   2.50        32.0        16.0______________________________________ 
    
     When mixtures made in accordance with the invention and mixed with water to produce a pozzolanic reaction have been tested in accordance with the specifications given in ASTM C-593 for fly ash and other pozzolans for use with lime, it has been found that the compositions meet or exceed the specifications. 
     The term &#34;fly ash&#34; as used in connection with stabilized bases is well known and as used herein is intended to indicate the finely divided ash residue produced by the combustion of pulverized coal or lignite, which ash is carried off with the gases exhausted from the furnace in which the coal is burned and which is collected from these gases usually by means of suitable precipitation apparatus such as electrical precipitators. Those finely pulverized ashes resulting from combustion of oil and from combustion of waste materials in a large incinerator or natural pozzolans can also be utilized in the methods described herein providing their chemical compositions are reasonably similar to pulverized coal fly ashes. The fly ash so obtained is in a finely divided state such that usually at least 70% by weight passes through a 200-mesh sieve, although incinerator ashes may be considerably coarser. Fly ash may be considered an &#34;artificial pozzolan&#34;, as distinguished from a &#34;natural pozzolan&#34;. 
     The term &#34;aggregate&#34; as used in connection with load supporting compositions is also well known and refers to natural or artificial inorganic materials most of which are substantially chemically inert with respect to fly ash and lime, and substantially insoluble in water. Typically, aggregate may comprise limestone, sand, blast furnace slag, gravel, synthetic aggregate and other similar material. 
     Aggregates can comprise a wide range of types and gradations, including sands, gravels, crushed stones, and several types of slag. Aggregates should be of such gradation that, when mixed with cement kiln dust, fly ash and water, the resulting mixture is mechanically stable under compaction equipment and capable of being compacted in the field to high density. The aggregate should be free from deleterious organic or chemical substances which may interfere with the desired chemical reaction between the cement kiln dust, fly ash and water. Further, the aggregate should preferably consist of hard, durable particles, free from soft or disintegrated pieces. 
     It has been found that a preferable mixture comprises: 
     
         ______________________________________         Percent by         Dry Weight______________________________________Cement Kiln Dust           8.0%Fly Ash         12.0%Aggregate       80.0%Total           100.0%______________________________________ 
    
     However, the mixture for use in road stabilizer bases may preferably vary as follows: 
     
         ______________________________________         Percent By         Dry Weight______________________________________Cement Kiln Dust            4-16%Fly Ash         6-24%Aggregate       60-90%______________________________________ 
    
     As indicated above, tests were conducted in accordance with ASTM C-593. More specifically, the test specimens were molded using a mechanical compactor, having a 10 pound hammer with an 18 inch drop. The material was placed in the molds in three equal layers, and compacted by 25 blows per layer. The machine has a revolving turntable to evenly distribute the blows over the surface of the layer being compacted. 
     After molding, the samples were carefully removed from the molds, weighed, and sealed in plastic bag, labeled for identification, and placed in a constant temperature oven at 100° F. to cure until tested. Two cylinders of each mix were marked for testing at 7, 14 and 28 days of curing. After removal from the oven, the samples are submerged in water for four hours, removed, and allowed to drain on a non-absorbant surface, capped, and tested within one hour after removal from the water. The capping compound used is &#34;Hydro-Stone&#34; a lime based, quick-hardening compound. Plate glass was used to obtain even, parallel caps on the test specimens. 
     Examples of various tests and compositions are as follows: 
     
                                           EXAMPLE I__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________     Cement Kiln Dust                    8.0%            2.4#     Fly Ash        12.0%           3.6#     Limestone      80.0%          24.0#     Total          100.0%         30.0#__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. In.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    10.8 4.73     141.9 128.1 12.57                               10-16                                   13,140                                       1050B    10.8 4.72     141.6 127.8 12.57                               10-16                                   14,370                                       1140C    10.8 4.73     141.9 128.1 12.57                               10-23                                   15,780                                       1260D    10.8 4.73     141.9 128.1 12.57                               10-23                                   15,530                                       1240E    10.8 4.73     141.9 128.1 12.57                               11-06                                   17,800                                       1420F    10.8 4.73     141.9 128.1 12.57                               11-06                                   17,800                                       1420__________________________________________________________________________ Remarks: Slight bleeding at bottom of mold. 
    
     
                                           EXAMPLE II__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________     Cement Kiln Dust                     8.0%          2.4#     Fly Ash        12.0%          3.6#     Limestone      80.0%          24.0#     Retarder       --             0.96 oz     Total          100.0%         30.0#__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. In.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    10.1 4.73     141.9 128.9 12.57                               10-16                                   --  --B    10.1 4.73     141.9 128.9 12.57                               10-16                                   --  --C    10.2 4.73     141.9 128.8 12.57                               10-23                                   1,650                                       130D    10.2 4.73     141.9 128.8 12.57                               10-23                                   1,930                                       150E    10.3 4.73     141.9 128.6 12.57                               11-06                                   2,300                                       180F    10.3 4.73     141.9 128.6 12.57                               11-06                                   2,100                                       170__________________________________________________________________________ Remarks: Slight bleeding. Samples 2A and 2B fell apart during the four (4) hour soaking. There was no intact sample to subject to the compression test. Samples C, D, E, and F were not subjected to the four (4) hour soaking, prior to testing. 
    
     
                                           EXAMPLE III__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________  Cement Kiln Dust   8.0%          2.4#  Fly Ash           12.0%          3.6#  Limestone         80.0%          24.0#  Calcium Chloride Solution                    --             (0.24#)  Total             100.0%         30.0#__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. in.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    10.4 4.77     143.1 129.6 12.57                               10-16                                   15,160                                       1210B    10.4 4.77     143.1 129.6 12.57                               10-16                                   15,750                                       1250C    10.0 4.73     141.9 129.0 12.57                               10-23                                   17,250                                       1370D     9.9 4.73     141.9 129.1 12.57                               10-23                                   18,950                                       1510E     9.8 4.73     141.9 129.2 12.57                               11-06                                   20,600                                       1640F     9.7 4.72     141.6 129.1 12.57                               11-06                                   20,700                                       1650__________________________________________________________________________ Remarks: Slight bleeding 
    
     
                                           EXAMPLE IV__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________     Cement Kiln Dust                    8.0%           2.4#     Stack Dust     3.0%           0.9#     Fly Ash        12.0%          3.6#     Limestone      77.0%          23.1#     Total          100.0%         30.0#__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. In.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    8.5  4.53     135.9 125.3 12.57                               10-17                                    8,200                                       652B    8.5  4.54     136.2 125.5 12.57                               10-17                                    8,900                                       708C    8.7  4.58     137.4 126.4 12.57                               10-24                                   10,950                                       871D    8.8  4.56     136.8 125.7 12.57                               10-24                                   11,775                                       937E    9.0  4.58     137.4 126.1 12.57                               11-07                                   16,050                                       1280F    9.0  4.56     136.8 125.5 12.57                               11-07                                   14,850                                       1180__________________________________________________________________________ Remarks: No bleeding. 
    
     
                                           EXAMPLE V__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________     Cement Kiln Dust                    12.0%          3.6#     Fly Ash        88.0%          26.4#     Total          100.0%         30.0#__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. In.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    9.5  2.87     86.1  78.6  12.57                               10-17                                   2,350                                       187B    9.7  2.90     87.0  79.3  12.57                               10-17                                   2,300                                       183C    9.7  2.90     87.0  79.3  12.57                               10-24                                   2,075                                       165D    9.7  2.90     87.0  79.3  12.57                               10-24                                   1,900                                       151E    9.7  2.90     87.0  79.3  12.57                               11-07                                   3,040                                       240F    10.0 2.96     88.8  80.7  12.57                               11-07                                   3,230                                       260__________________________________________________________________________ Remarks: Had difficulty in reaching the desired moisture content because of the dust&#39;s extremely dry condition. Extremely &#34;fluffy&#34; material. 
    
     
                                           EXAMPLE VI__________________________________________________________________________                                   Weight of                    Percent        Batch__________________________________________________________________________Cement Kiln Dust         8.0%           2.4#Fly Ash                  8.0%           2.4#Limestone                79.0%          23.7#Limestone Fines          5.0%           1.5#Total                    100.0%         30.0#Water added: 1158 + 136 = 1294__________________________________________________________________________SpecimenPercent     Wt. As   Wet Wt.                    Dry Wt.                          Area Date                                   Mach.No.  Water     Molded (Lbs.)              Per Cu. Ft.                    Per Cu. Ft.                          (Sq. In.)                               Tested                                   Load                                       P.S.I.__________________________________________________________________________A    9.8  4.85     145.5 132.5 12.57                               10-20                                   13,900                                       1110B    9.8  4.81     144.3 131.4 12.57                               10-20                                   15,000                                       1190C    9.8  4.79     143.7 130.9 12.57                               10-27                                   17,350                                       1380D    9.9  4.81     144.3 131.3 12.57                               10-27                                   18,200                                       1448E    9.9  4.81     144.3 131.3 12.57                               11-10                                   17,050                                       1356F    9.9  4.78     143.4 130.5 12.57                               11-10                                   16,600                                       1321__________________________________________________________________________ Remarks: Good compactability. Material was relatively easy to work with. 
    
     
                                           EXAMPLE VII__________________________________________________________________________                        Weight of                  Percent                        Batch__________________________________________________________________________     Fly Ash      8.0%  2.40#     Kiln Dust    10.0% 3.00#     No. 304 Limestone                  82.0% 24.60#     (Screened over 3/4&#34; screen)     Total        100.0%                        30.00#__________________________________________________________________________Cyl.   Percent   Wt. As Wet Wt.                Dry Wt.                      Area Date                               Mach.No.   Water   Molded(Lbs.)          Per Cu. Ft.                Per Cu. Ft.                      (Sq. In.)                           Tested                               Load                                   P.S.I.__________________________________________________________________________1  11.5 4.73   141.9 127.3 12.57                           4-01                                9350                                    7452  11.1 4.71   141.3 127.2 12.57                           4-01                                8610                                    6853  11.1 4.73   141.9 127.7 12.57                           4-01                                9290                                    7404  11.1 4.74   142.2 128.1 12.57                           4-22                               14050                                   11205  11.0 4.75   142.5 128.4 12.57                           4-22                               13500                                   10756  10.7 4.74   142.2 128.5 12.57                           4-22                               13620                                   1085__________________________________________________________________________ A. Slight bleeding at bottom of mold during compaction. B. Material appeared deficient in limestone fines (#4 material). C. Some free moisture noted, giving slight &#34;glossy&#34; appearance. D. Samples slumped, following extraction from molds. 
    
     
                                           EXAMPLE VIII__________________________________________________________________________                        Weight of                  Percent                        Batch__________________________________________________________________________     Fly Ash      10.0% 3.00#     Kiln Dust    8.0%  2.40#     No. 304 Limestone                  82.0% 24.60#     (Screened over 3/4&#34; screen)     Total        100.0 30.00#__________________________________________________________________________Cyl.   Percent   Wt. As Wet Wt.                Dry Wt.                      Area Date                               Mach.No.   Water   Molded (Lbs.)          Per Cu. Ft.                Per Cu. Ft.                      (Sq. In.)                           Tested                               Load                                   P.S.I.__________________________________________________________________________1  9.3  4.72   141.6 129.6 12.57                           4-01                               8060                                   6402  9.4  4.71   141.3 129.2 12.57                           4-01                               7750                                   6153  9.4  4.71   141.3 129.2 12.57                           4-01                               8000                                   6354  9.5  4.69   140.7 128.5 12.57                           4-22                               9730                                   7755  9.6  4.68   140.4 128.1 12.57                           4-22                               10450                                   8306  9.5  4.69   140.7 128.5 12.57                           4-22                               11490                                   915__________________________________________________________________________ A. Samples retained shape following extraction from molds. B. No free water noticed bleeding during compaction. 
    
     
                                           EXAMPLE IX__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Fly Ash      8.0%       2.40#   Kiln Dust    10.0%      3.00#   Fill Sand    82.0%      24.60#   Total        100.0%     30.00#__________________________________________________________________________Cyl.   Percent   Wt. As Wet Wt.                Dry Wt.                      Area Date                               Mach.No.   Water   Molded (Lbs.)          Per Cu. Ft.                Per Cu. Ft.                      (Sq. In.)                           Tested                               Load                                   P.S.I.__________________________________________________________________________1  9.8  4.09   122.7 111.7 12.57                           3-31                               1800                                   1452  10.0 4.12   123.6 112.4 12.57                           3-31                               1700                                   1353  9.9  4.10   123.0 111.9 12.57                           3-31                               1690                                   1354  9.9  4.11   123.3 112.2 12.57                           4-21                               2810                                   2255  10.0 4.10   123.0 111.8 12.57                           4-21                               2880                                   2306  9.8  4.09   122.7 111.7 12.57                           4-21                               2670                                   210__________________________________________________________________________ A. No bleeding of sample during compaction. B. Material stayed in a ball when packed by hand. C. Slight bulking noticed. D. Easily compacted. 
    
     
                                           EXAMPLE X__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Fly Ash      8.0%       2.40#   Kiln Dust    10.0%      3.00#   Glass (Crushed to approx.   1/2&#34; size)   32.0%      9.60#   Fill Sand    50.0%      15.00#   Total        100.0%     30.00#__________________________________________________________________________Cyl.   Percent   Wt. As Wet Wt.                Dry Wt.                      Area Date                               Mach.No.   Water   Molded (Lbs.)          Per Cu. Ft.                Per Cu. Ft.                      (Sq. In.)                           Tested                               Load                                   P.S.I.__________________________________________________________________________1  9.4  4.50   135.0 123.4 12.57                           4-02                               4390                                   3502  9.4  4.50   135.0 123.4 12.57                           4-02                               4590                                   3653  9.3  4.51   135.3 123.8 12.57                           4-02                               4200                                   3354  9.2  4.52   135.6 124.2 12.57                           4-23                               6750                                   5355  9.1  4.51   135.3 124.0 12.57                           4-23                               6870                                   5456  9.1  4.47   134.1 122.9 12.57                           4-23                               6280                                   500__________________________________________________________________________ A. Material originally mixed to 10.3% moisture, looked wet, probably because nonabsorbancy of glass. B. Air dried the mix out to approximately 9.4% moisture, did not bulk at this moisture content. C. Surprisingly good cohesion of mix, even with the smooth faces of glass particles. D. Strength of cylinders higher than expected, thought the mix would slip off the smooth glass faces, when put under compression. 
    
     
                                           EXAMPLE XI__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Cement Kiln Dust                16.0       3.2#   Fly Ash      24.0       4.8#   No. 304 Crushed Limestone                60.0       12.0#   Total        100.0      20.0#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date                                 Mach.No.  Water     Molded (Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested                                 Load                                     P.S.I.__________________________________________________________________________A    16.6 4.50   135.0 115.8 12.57                             12/22                                 5890                                     470B    15.1 4.46   133.8 116.2 12.57                             12/22                                 6000                                     480C    15.0 4.46   133.8 116.3 12.57                             12/22                                 6150                                     490__________________________________________________________________________ 
    
     
                                           EXAMPLE XII__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Cement Kiln Dust                4.0        0.8#   Fly Ash      6.0        1.2#   No. 304 Crushed Limestone                90.0       18.0#   Total        100.0      20.0#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date                                 Mach.No.  Water     Molded (Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested                                 Load                                     P.S.I.__________________________________________________________________________A    11.1 4.94   148.2 133.4 12.57                             12/22                                 2950                                     230B    11.2 4.93   147.9 133.0 12.57                             12/22                                 3570                                     280C    11.2 4.93   147.9 133.0 12.57                             12/22                                 3250                                     260__________________________________________________________________________ 
    
     
                                           EXAMPLE XIII__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Cement Kiln Dust                6.9%       140#   Fly Ash      11.8%      240#   Limestone Screenings                39.4%      800#   No. 57 Crushed Limestone                39.4%      800#   Water        2.5%        50#   Total        100.0%     2030#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date      Mach.No.  Water     Molded (Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested    Load                                           P.S.I.__________________________________________________________________________A    5.6  4.49   134.7 127.6 12.57                             11-22     8,950                                           712B    5.1  4.51   135.3 128.7 12.57                             11-22     8,225                                           654C    5.5  4.51   135.3 128.2 12.57                             11-22     9,050                                           720D    5.4  4.50   135.0 128.1 12.57                             11-29     9,610                                           760E    5.5  4.49   134.7 127.7 12.57                             11-29     8,080                                           640F    4.9  4.50   135.0 128.7 12.57                             11-29     9,630                                           770G    5.1  4.46   133.8 127.3 12.57                             12-13     8,820                                           700H    5.3  4.51   135.3 128.5 12.57                             12-13     9,380                                           750I    5.4  4.50   135.0 128.1 12.57                             12-13     9,400                                           750J    5.3  4.46   133.8 127.1 12.57                             02-03K    5.1  4.51   135.3 128.7 12.57                             02-03L    4.9  4.48   134.4 128.1 12.57                             02-03M    5.0  4.54   136.2 129.7 12.57                             For Durablilty TestN    4.9  4.54   136.2 129.8 12.57                             For Durability TestO    4.8  4.47   134.1 128.0 12.57                             For Durability Test__________________________________________________________________________ 
    
     
                                           EXAMPLE XIV__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Cement Type I                1.0%        20#   Cement Kiln Dust                6.8%       140#   Fly Ash      11.7%      240#   Limestone Screenings                39.0%      800#   No. 57 Crushed Limestone                39.0%      800#   Water        2.5%        50#   Total        100.0%     1050#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date      Mach.No.  Water     Molded (Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested    Load                                           P.S.I.__________________________________________________________________________A    5.4  4.58   137.4 130.4 12.57                             11-21     10,030                                            800B    5.4  4.58   137.4 130.4 12.57                             11-21     11,780                                            940C    5.4  4.58   137.4 130.4 12.57                             11-21     14,120                                           1120D    5.3  4.58   137.4 130.5 12.57                             11-28     15,500                                           1230E    5.0  4.58   137.4 130.9 12.57                             11-28     18,500                                           1470F    5.8  4.46   133.8 126.5 12.57                             11-29     14,910                                           1190G    5.8  4.46   133.8 126.5 12.57                             12-13     17,900                                           1420H    5.7  4.46   133.8 126.6 12.57                             12-13     20,010                                           1590I    5.7  4.46   133.8 126.6 12.57                             12-13     14,980                                           1190J    5.7  4.46   133.8 126.6 12.57                             02-13K    5.6  4.46   133.8 126.7 12.57                             02-13L    5.6  4.46   133.8 126.7 12.57                             02-13M    5.4  4.49   134.7 127.8 12.57                             For Durability TestN    5.4  4.49   134.7 127.8 12.57                             For Durability TestO    5.4  4.49   134.7 127.8 12.57                             For Durability Test__________________________________________________________________________ 
    
     
                                           EXAMPLE XV__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Cement Kiln Dust                7.8%       160#   Fly Ash      11.7%      240#   Limestone Screenings                39.0%      800#   No. 57 Crushed Limestone                39.0%      800#   Water        2.5%        50#   Total        100.0%     2050#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date      Mach.No.  Water     Molded(Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested    Load                                           P.S.I.__________________________________________________________________________A    8.1  4.24   127.2 117.7 12.57                             11-22     4,650                                           370*B    7.9  4.24   127.2 117.9 12.57                             11-22     5,700                                           450C    8.3  4.29   128.7 118.8 12.57                             11-22     6,030D    7.8  4.25   127.5 118.3 12.57                             11-29     7,200                                           570E    7.7  4.24   127.2 118.1 12.57                             11-29     6,850                                           540F    7.6  4.26   127.8 118.8 12.57                             11-29     8,080                                           640G    7.6  4.30   129.0 119.9 12.57                             12-13     10,000                                           800H    7.6  4.27   128.1 119.0 12.57                             12-13     9,500                                           760I    7.6  4.27   128.1 119.0 12.57                             12-13     8,980                                           710J    7.5  4.27   128.1 119.2 12.57                             02-13K    7.3  4.28   128.4 119.7 12.57                             02-13L    7.2  4.26   127.8 119.2 12.57                             02-13M    7.2  4.27   128.1 119.5 12.57                             For Durability TestN    7.1  4.24   127.2 118.8 12.57                             For Durability TestO    7.2  4.25   127.5 118.9 12.57                             For Durability Test__________________________________________________________________________  *Sample fractured horizontally during capping Remarks: This product was produced on November 6, and sampled on November 13. Materials are the same as in Example XIII  This example is a check to see if the age of the product, before use, has any effect on the strength results. 
    
     
                                           EXAMPLE XVI__________________________________________________________________________                           Weight of                Percent    Batch__________________________________________________________________________   Fly Ash      11.6%       232#   Lime          3.4%       68#   No. 304 Crushed Limestone                85.0%      1700#   Water        --         --   Total        100.0%     2000#__________________________________________________________________________SpecimenPercent     Wt. As Wet Wt.                  Dry Wt.                        Area Date      Mach.No.  Water     Molded(Lbs.)            Per Cu. Ft.                  Per Cu. Ft.                        (Sq. In.)                             Tested    Load                                           P.S.I.__________________________________________________________________________A    10.4 4.60   138.0 125.0 12.57                             11-28     10,325                                            820B    10.4 4.70   141.0 127.7 12.57                             11-28     11,950                                            950C    10.2 4.62   138.6 125.8 12.57                             11-28     10,650                                            850D    10.2 4.67   140.1 127.1 12.57                             12-05     19,600                                           1559E    10.2 4.66   139.8 126.9 12.57                             12-05     18,950                                           1508F    11.1 4.65   139.5 125.6 12.57                             12-05     19,825                                           1577G    10.8 4.66   139.8 126.2 12.57                             12-19     21,860                                           1740H    10.8 4.66   139.8 126.2 12.57                             12-19     20,790                                           1650I    10.8 4.64   139.2 125.6 12.57                             12-19     21,000                                           1670J    10.8 4.70   141.0 127.3 12.57                             02-19K    10.9 4.65   139.5 125.8 12.57                             02-19L    10.9 4.68   140.4 126.6 12.57                             02-19M    10.9 4.66   139.8 126.1 12.57                             For Durability TestN    10.9 4.68   140.4 126.6 12.57                             For Durability TestO     9.6 4.63   138.9 126.7 12.57                             For Durability Test__________________________________________________________________________ 
    
     The results of the tests are summarized in FIGS. 1-3. 
     As shown in FIG. 1, mixtures containing cement kiln dust vary but in each instant produce a base that is stabilized. 
     As shown in FIG. 2, the addition of additives or admixtures generally do not affect the strength except that a retarder tends to prevent the early development of strength as might be expected. 
     As shown in FIG. 3, the strength of mixtures including cement kiln dust compare favorably with a lime, fly ash, aggregate mixture. In addition, even a mixture of cement kiln dust and fly ash produces a stabilized base. 
     Thus, the mixtures of the present invention result in a stabilized base that is comparable in strength and required performance characteristics to cement-aggregate or lime-fly ash-aggregate stabilized bases and yet are not energy intensive. The mixtures of the present invention cost less than the predominantly used asphalt-aggregate bases. Also, the use of mixtures of the invention releases asphalt for use in resurfacing or as a heavy industrial fuel. 
     FIG. 4 is a curve showing the BTU&#39;s per mile versus thickness for various road paving materials taken from Highway Research Circular titled &#34;Fuel Usage Factors for Highway Construction&#34;, Number 158, July, 1974. It ca be seen that asphalt concrete and cement type mixtures require substantial energy and only granular base or sub-base of aggregate has minimal energy requirements in hauling, spreading, compacting and finishing. Since the mixtures of the present invention utilize waste materials, namely, cement kiln dust and fly ash, the energy requirements for making a stabilized base are only in hauling, spreading, compacting and finishing. 
     As a result, the mixtures of the present invention have minimal energy requirements and thereby obviate the energy intensive materials or prior stabilized bases. 
     The mixtures of the present invention utilize cement kiln dust which is a waste product that is relatively available from cement plants and fly ash which is readily available from power plants.