Cement binder

Abstract

The invention provides a binder composition comprising: (a) ground granulated blast furnace slag (GGBS), (b) basic oxygen slag (BOS), and (c) an alkaline inorganic waste material selected from by-pass dust (BPD), cement kiln dust (CKD), and mixtures thereof. The use of such a composition as a binder in a concrete mix, concrete mixes comprising such a composition, methods of manufacturing concrete articles, and concrete articles such as paving blocks are also provided.

Claims

1. A binder composition which is free of Portland cement and which comprises: (a) ground granulated blast furnace slag (GGBS) in an amount of 30 to 60 wt. % by weight of binder composition on a dry solids basis, (b) basic oxygen slag (BOS) in an amount of 30 to 60 wt. % by weight of binder composition on a dry solids basis, and (c) an alkaline inorganic waste material selected from by-pass dust (BPD), cement kiln dust (CKD), and mixtures thereof, in an amount of 3 to 12 wt. % by weight of binder composition on a dry solids basis.

2. A binder composition as claimed in claim 1, wherein the alkaline inorganic waste material is BPD.

3. A binder composition as claimed in claim 1 which comprises: (a) GGBS in an amount of about 40 wt. % by weight of binder composition on a dry solids basis; (b) BOS in an amount of about 50 wt. % by weight of binder composition on a dry solids basis; and (c) BPD in an amount of about 10 wt. % by weight of binder composition on a dry solids basis.

4. A concrete mix comprising the following components (i) to (iv): (i) a binder composition as claimed in claim 1; (ii) aggregate; (iii) sand; and optionally (iv) fibres.

5. A concrete mix as claimed in claim 4 comprising about 5 to about 30 wt. % component (i) on a dry solids basis.

6. A concrete mix as claimed in claim 4 comprising about 40 to about 65 wt. % component (ii) on a dry solids basis.

7. A concrete mix as claimed in claim 4 comprising about 15 to about 25 wt. % component (iii) on a dry solids basis.

8. A concrete mix as claimed in claim 4 comprising about 1 to about 2 wt. % component (iv) based on a combined weight of components (i)-(iii) and, where present, any other non-fibre components.

9. A concrete mix as claimed in claim 4 comprising component (i) in an amount of about 28 wt. % on a dry solids basis, component (ii) in an amount of about 52 wt. % on a dry solids basis, component (iii) in an amount of about 20 wt. % on a dry solids basis, and component (iv) in an amount of about 1.5 wt. % based on a combined weight of components (i)-(iii).

10. A concrete mix as claimed in claim 4, wherein the fibres are metallic fibres.

11. A semi-dry composition comprising a concrete mix as claimed in claim 4 in combination with water.

12. A method of manufacturing a concrete article, the method comprising the steps of: (i) preparing a concrete mix as defined in claim 4; (ii) adding water whereby to form a semi-dry composition; and (iii) casting the semi-dry composition into a mould having a desired shape.

13. A method of manufacturing a multi-layered concrete article, the method comprising the steps of: (i) preparing a first concrete mix as defined in claim 4; and (ii) mixing said first concrete mix with water whereby to form a first semi-dry composition; (iii) pouring the first semi-dry composition into a mould having a desired shape; (iv) preparing a second concrete mix as defined in claim 4, wherein a composition of said second concrete mix is different from a composition of the first concrete mix; (v) adding water to said second concrete mix whereby to form a second semidry composition; and (vi) pouring the second semi-dry composition into the mould whereby to form a layer on top of the first semi-dry composition.

14. A concrete article formed from a binder composition as defined in claim 1.

15. A concrete article as claimed in claim 14, wherein the article comprises a plurality of layers and wherein adjacent layers differ in composition.

16. A concrete article as claimed in claim 15, wherein the article comprises an upper layer which is free of fibres and a lower layer which comprises fibres.

17. A concrete article as claimed in claim 14 which is a paving block.

18. A paving block as claimed in claim 17 having at least one of the following properties as determined according to BS EN 1338:2003, (i) a minimum tensile strength of 3.6 MPa; (ii) water absorption of less than 6%; (iii) freeze-thaw resistance of <1.0 Kg/m.sup.2; and (iv) a slip/skid resistance of at least 40 BPN.

19. A concrete article formed from a concrete mix as defined in claim 4.

20. A concrete article formed from a semi-dry composition as defined in claim 11.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will now be illustrated further with reference to the following non-limiting Examples and the accompanying Figures in which:

(2) FIG. 1 shows thermogravimetric (TGA) analysis results for un-weathered basic oxygen slag (UW-BOS) and weathered basic oxygen slag (W-BOS);

(3) FIG. 2 shows TGA analysis results for cement bypass dust (BPD);

(4) FIG. 3 shows a sieve analysis of 6 mm aggregates;

(5) FIG. 4 shows a sieve analysis of 4 mm aggregates;

(6) FIG. 5 shows the results of a splitting tensile strength test (in MPa) on OPC-GGBS-BOS mixtures according to the invention carried out after 14 days using different methods of compaction;

(7) FIG. 6 shows the results of a splitting tensile strength test (in MPa) on OPC-GGBS-BOS mixtures according to the invention carried out after 14 days using different pressing loads (in kN);

(8) FIG. 7 shows the results of an X-ray diffraction (XRD) analysis of a BOS-BPD-GGBS mixture according to the invention carried out after 28 days; and

(9) FIG. 8 shows a photograph of a paving block made using the binder composition of the invention (mix 5), taken after tensile testing was performed.

(10) In the Examples the following acronyms and abbreviations are employed:

(11) TABLE-US-00002 Ordinary Portland Cement OPC Basic Oxygen Slag BOS Ground Granulated Blast Furnace Slag GGBS Cement Bypass Dust BPD Pulverised Fuel Ash PFA Steel Fibre SF Loss on Ignition LoI British Pendulum Number BPN Run Of Station Ash ROSA

(12) The ground granulated blast furnace slag (GGBS) was obtained from Civil and Marine, a part of Hanson UK. The material was marketed under the BS EN 15167-1:2006 standard and had a specific gravity of 2.9.

(13) The basic oxygen slag was acquired from Tarmac UK from the Corus-Tata plant at Scunthorpe. This was milled using a laboratory ball mill, and passed through a 600 m sieve before being added to the mixes. The average particle size of BOS slag used was 40-60 m as determined by a Malvern Mastersize 2000 laser analyser with an accuracy of 1%. FIG. 1 shows the results of thermogravimetric analysis (TGA) of weathered and unweathered BOS as determined by a Perkin Elmer Pyris 1 thermogravimetric analyser. Weathered BOS is not freshly produced, but rather is taken from the stock pile and hence tends to be more carbonated, i.e. it has less free lime than unweathered BOS.

(14) BPD from a local cement works, Castle Cement (Heidelberg cement group, Rugby, UK), was obtained. The BPD was provided in a powder form. The average size of fine particles was about 10 m for the BPD, and the maximum particle size was 200 m. The TGA results are shown in FIG. 2.

(15) Steel wire fibre with hooked ends 35 mm in length and 0.55 mm in diameter with tensile strength of about 1250 N/mm.sup.2 was obtained from KrampeHarex.

(16) The aggregates used in the Examples originated from two sources. The natural sand used has a density of 2.6 g/cm.sup.3 as determined using a helium pycnometer. Two different maximum sizes, 4 mm and 6 mm, of natural crushed quartz aggregates were used.

(17) Tables 2 and 3 and FIGS. 3 and 4 show the results of sieve analysis of the aggregates used. These aggregates comply with BS 882:1992 and BS EN 12620:2002.

(18) TABLE-US-00003 TABLE 2 Aggregate grading of 6 mm used for concrete paving blocks Retained passing Percent Sieve size weight weight passing (mm) (g) (g) (%) 9.0 0 2000 100 6.3 157.8 1842.2 92.11 6.0 730.9 1111.3 55.57 5.0 43.1 1068.2 53.41 4.75 175.9 892.3 44.62 4.0 284.5 607.8 30.39 3.35 129.9 477.9 23.89 2.8 71.6 406.3 20.32 2.36 24.3 382 19.1 1.18 37.3 344.7 17.24 600 13.5 331.2 16.56 300 29.5 301.7 15.09 150 268.3 33.4 1.67 75 22.9 10.5 0.53 <75 10.5 Total weight 2000

(19) TABLE-US-00004 TABLE 3 Aggregate grading of 4 mm used for concrete paving blocks Retained passing Percent Sieve size weight weight passing (mm) (g) (g) (%) 5.00 0 2000 100 4.75 119.3 1880.7 94.04 4.0 94.7 1786 89.3 3.35 92.2 1693.8 84.69 2.8 142.7 1551.1 77.56 2.36 122.5 1428.6 71.43 1.18 615.0 813.6 40.68 600 610.5 203.1 10.16 300 141.8 61.3 3.07 150 28.3 33 1.65 75 24.4 8.6 0.43 <75 8.6 Total weight 2000

EXAMPLE 1

Comparison of Laboratory Compaction Simulation with Factory Methods Using Conventional Portland Cement-Containing Paving Block Mixtures

(20) Conventional Portland cement-containing mixtures were prepared and subjected to a number of different methods of compaction. This was carried out to optimise the compaction methods to be used in laboratory testing of the compositions of the invention.

(21) The optimal method of compaction examined was a pressing action method making use of a compression machine. In this technique, different magnitudes of loads were applied to determine the best results in order to obtain consistent density and optimum flexural strength results. The materials were compacted in one layer. A mould collar was also used to retain the material within the mould.

(22) FIG. 5 shows that the pressing action gives the highest splitting tensile strength for the paste compared to other methods (rammer application, hammer drill compaction, and compaction with a drill hammer and vibrating table). FIG. 6 shows the effect of different compaction loadings on the tensile strength of the paste.

(23) Table 4 shows the results obtained for tensile strength of paste mixtures (averaged over three specimens) using various compaction loadings.

(24) TABLE-US-00005 TABLE 4 Pressing action technique results (using compression machine). Average Average Average Average tensile Age Load weight failure load density strength Code name Type (days) (kN) (g) (kN) (Kg/m.sup.3) (MPa) OPC-GGBS-BOS Block 14 15 2673.4 53.20 1833 2.3 OPC GGBS BOS Water 20 2737.2 55.52 1877 2.4 40% 30% 30% 15% 25 2730.4 57.83 1872 2.5 3.6 2.7 2.7 1.35 30 2911.2 64.77 1996 2.8 (kg) (kg) (kg) (L) 40 2930.7 67.08 2010 2.9 70 2975.2 71.71 2030 3.1 100 3138.0 76.33 2009 3.3 150 3174.5 87.89 2162 3.8 200 3173.4 90.21 2176 3.9 250 3270.3 92.53 2242 4.0 400 3261.5 129.54 2236 5.6

(25) The results indicated that loadings over 70 kN gave more consistent results than lower loadings. As expected, 400 kN gave the highest strength. 150 kN was found to be practical, as bracing of the mould was not needed. A 400 kN load was found to provide comparable strength values to factory-produced specimens, but required more bracing of the moulds to avoid buckling. Loadings of more than 400 kN were not required since similar density results to factory-produced paving blocks were obtained and the bracing of the moulds would have proved difficult. Another concern for higher than 400 kN compaction loadings was the crushing of the aggregates in concrete paving blocks.

(26) 150 and 400 kN loadings were therefore adopted, respectively, for casting of the experiments for paste and concrete paving blocks using the Portland cement-free compositions of the invention.

EXAMPLE 2

Comparison of Factory-Made and Laboratory-Made Blocks Including Portland Cement

(27) A mix design obtained from a paving block manufacturer is given in Table 5 below. The materials used by the factory were also obtained and used in the laboratory to cast the replicated mix design from the factory and compare the results.

(28) TABLE-US-00006 TABLE 5 Two mix designs of paving blocks used by a factory (percentage by weight) Portland Colour Cement GGBS 4 mm - Dust 6 mm Clean Sand Natural 10% 4% 53% 9% 24% Portland Colour Cement PFA 4 mm - Dust 6 mm Clean Sand Charcoal 10% 4% 53% 9% 24%

(29) The results of the two different factory designed mixes cast and tested in the laboratory are given in Tables 6 and 7. The compaction loading of 400 kN was used in the laboratory for these mixes. The results indicate 28 days tensile strength of 3.2 and 2.6 MPa respectively for their GGBS and PFA mixes which includes the traditional 10 percent cement by weight.

(30) It is remarkable that the factory blocks of GGBS mix which were brought to the laboratory also gave an average tensile strength of 3.2 MPa. This implies that the laboratory compaction method of 400 kN for concrete blocks gives an exact match with the factory compaction method. It is noteworthy that a minimum tensile strength of 3.6 MPa is specified by the BS EN1338: 2003 standard for paving blocks to be acceptable for consumers. For this reason all the blocks were cast in the laboratory to ensure satisfaction of standard requirements.

(31) TABLE-US-00007 TABLE 6 Factory mixture design with GGBS showing compressive and tensile splitting strength results at 14 and 28 days carried in the laboratory. Cement GGBS 4 mm-Dust 6 mm Clean Sand 10% 4% 53% 9% 24% 50 mm cubes Mean compressive compressive Age Mass Failure load Density strength strength No (days) (g) (kN) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) Cubes 1 14 274.0 30.8 2192.0 12.3 11.7 2 273.5 29.7 2188.0 11.9 3 273.5 28.5 2188.0 11.4 4 273.0 27.2 2184.0 10.9 1 28 290.5 45.1 2324.0 18.0 18.6 2 291.0 46.3 2328.0 18.5 3 291.5 47.5 2332.0 19.0 4 290.0 40.9 2320.0 16.4 5 292.0 47.5 2336.0 19.0 190 100 76 mm Mean tensile tensile Failure Failure Failure Splitting Splitting Time Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKs 1 14 3467.0 47.3 190 76 2377.2 2.1 2.0 2 3466.5 45.7 190 76 2376.9 1.9 3 3465.5 43.9 190 76 2376.2 1.9 1 28 3477.0 74.6 190 76 2384.1 3.2 3.2 2 3484.5 75.9 190 76 2389.2 3.3 3 3474.0 72.4 190 76 2381.9 3.1 4 3470.5 70.1 190 76 2379.6 3.0 5 3474.5 73.2 190 76 2382.3 3.2

(32) TABLE-US-00008 TABLE 7 Factory mixture design with PFA showing compressive and tensile splitting strength results at 14 and 28 days carried in the laboratory. Cement PFA 4 mm-Dust 6 mm Clean Sand 10% 4% 53% 9% 24% 50 mm cubes Mean Compressive Compressive Age Mass Failure load Density strength strength No (days) (g) (kN) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) Cubes 1 14 283.5 30.2 2268.0 12.1 12.9 2 285.0 32.8 2280.0 131 3 284.5 31.6 2276.0 12.6 1 28 290.5 42.3 2324.0 16.9 15.7 2 289.0 38.8 2312.0 15.5 3 289.5 39.5 2316.0 15.8 190 100 76 m Mean Tensile Tensile Failure Failure Splitting Splitting Time Mass Failure load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKs 1 14 3479.0 44.7 190 76 2385.4 1.9 2.0 2 3480.5 46.9 190 76 2386.5 2.0 3 3487.5 48.7 190 76 2391.3 2.1 1 28 3493.0 58.4 190 76 2395.0 2.5 2.6 2 3493.5 60.3 190 76 2395.4 2.6 3 3519.0 62.3 190 76 2412.8 2.7 4 3495.0 60.6 190 76 2396.4 2.6 5 3501.0 61.8 190 76 2400.5 2.7

EXAMPLE 3

Portland Cement-Free Binder and Paste Compositions

(33) Materials and Methods

(34) Mixing and Casting Methods:

(35) All mixtures were mechanically mixed in a pan mixer to produce a uniform distribution of the materials. Steel paving block moulds of 190 mm in length, 100 mm in width and 76 mm in depth were used for the casting of paving blocks. A compression machine was used to fully compact the materials in one layer with 150 kN of load for pastes and 400 kN for concrete.

(36) Paste and Concrete Mixture:

(37) A Hobart mixer machine was used for all paste mixes. The mixing technique adopted for paste was as follows: The dry materials were mixed using a mechanical pan mixer for 2 minutes. Then the paste was hand mixed to ensure the materials in the bottom of the bowl were mixed thoroughly. The dry materials were mixed again for another 2 minutes. Water was then added and the paste was mixed for another 2 minutes, at medium and high speed.

(38) The mixing for concrete was carried out according to standard procedures followed in factory production of concrete paving blocks. A pan mixer of about 15 liter capacity was used to make the concrete mixes. This mixing procedure was as follows: The fine and coarse aggregates were measured in the designed proportions (see Tables 10 and 19) and poured into the pan mixer. They were then mixed dry for 45 seconds. The BOS, BPD, and GGBS were measured, poured in the mixer and mixed dry for 45 seconds. Half the water needed for the mix was added and the mixing continued for another 1 minute. The mixer was stopped and mixture scrapped off the corners and bottom of the pan and blades. The remainder of the water was added and mixing was carried out for another 2 minutes.

(39) When steel fibres were added, these were added (as applicable) and mixed properly after the aggregates had been mixed properly with the cementitious material.

(40) Casting and Curing:

(41) The materials were cast in pre-oiled blocks and cube moulds by a compression machine. Once cast, the specimens were covered with a polythene sheet so that there would be no loss of water. On the next day all samples were de-moulded and then stored in curing chambers at a constant air temperature of 222 C. and 98% relative humidity until they were to be tested.

(42) Test Methods

(43) Compressive Strength:

(44) The compressive strength of the cubes and paving block specimens can be defined as the measured maximum resistance of a concrete to axial loading. This test was carried out at 14 and 28 days of age for each specimen and then the density was determined. The compressive strength of the specimens was determined using the Avery-Denison compression testing machine with a maximum capacity load of 2000 kN, according to standard methods as described in BS EN 12390-3:2009. For the 5050 mm cubes, the compression load was applied to the smooth face The compressive strength of the cubes were determined by dividing the maximum load by the load area of the specimen.

(45) Splitting Tensile Strength Test:

(46) BS EN 1338: 2003 was used to determine the tensile splitting strength of the paving blocks and the load was applied along the longest splitting section of the specimen block. Prior to the test, the block specimen was located in the split tensile steel frame, using wood pieces on the top and bottom of the specimen to provide packing.

(47) In this test the block samples were immersed in water at 205 C. for 24 hours after which they were removed, wiped dry and the tests were carried out immediately. Contact was made between the plates of the loading machine and the top and bottom of the steel plates of the testing frame, before the load was slowly applied at a rate of (0.050.01) MPa/s until the point of failure, at which point the test was brought to an end and the specimen was divided into two halves. A record was made of the failure load and the tensile splitting stress was calculated in MPa according to BS EN1338: 2003 as given below:
Splitting strength=0.637failure loadthickness factor/(failure lengthfailure thickness)

(48) The mean strength must be at least 3.6 N/mm.sup.2 with no individual result below 2.9 N/mm.sup.2.

(49) TABLE-US-00009 TABLE 8 Factors given in BSEN1338 standard Thickness Factor 50 mm 0.79 60 mm 0.87 70 mm 0.94 80 mm 1 100 mm 1.11

(50) A minimum tensile strength of 3.6 MPa is specified to be obtained by the standard for paving blocks in order to be acceptable by the industry. The compressive strength of the cubes is defined as measured maximum resistance of a concrete to uni-axial loading. Blocks and cubes were tested at 14 and 28 days of age for comparison purposes only.

(51) Slip/Skid Resistance:

(52) The likelihood of pedestrians slipping and vehicles skidding is measured by determining its slip/skid resistance. In order to measure unpolished slip resistance use is made of a standard rubber material which is attached to a Pendulum Friction Tester; this is then tested under wet conditions. BS EN 1338: 2003 Annex I was used to find the unpolished slip resistance value. Concrete paving blocks have satisfactory slip/skid resistance provided that their whole upper surface has not been ground and/or polished to produce a very smooth surface. This test is able to measure a block paving's slip resistance under laboratory conditions subsequent to be subjected to simulated traffic loadings. This is in order to reproduce the condition that paving blocks will perform under traffic conditions.

(53) The test was carried out as follows: The friction test equipment was kept in a room at a temperature of 202 C. for 30 minutes before the test. The block samples were immersed in water at 202 C. 30 minutes before the test. The friction tester was then placed on a firm level table and the levelling screws were adjusted to make sure the pendulum support column was vertical. The test sample was then placed on the equipment with the longer dimension lying track of the pendulum and centrally placed with respect to the rubber slider. The pendulum and the pointer were then released and the values on the pointer (measured in British Pendulum Numbers (BPN)) on the scale were recorded.

(54) This process was repeated five times for each sample and the mean of the last three readings were recorded. The mean is the accepted value for the slip/skid resistance. BS EN 1338: 2003 Annex I gives the following slip resistance table (Table 9) as an indication of the value against the potential for slip.

(55) TABLE-US-00010 TABLE 9 Pendulum test values taken from BS EN 1338: 2003 Annex I Pendulum test value (BPN) Potential for slip Description of surface Below 19 High Dangerous 20 to 39 Moderate Marginal 40 to 74 Low Satisfactory Above 75 Extremely low Excellent

(56) Weathering Resistance:

(57) This is an expression of the extent to which concrete paving blocks are able to withstand weathering where particular circumstances exist, such as surfaces being frequently subjected to contact with de-icing salt when there is frost. It is possible to assess this capacity under laboratory conditions by making a measurement of the amount of spalled material accumulating on a surface when it has been subjected to repeated freezing and thawing with a de-icing salt being used. Where there has been no use of de-icing salt, measurements should be made of the porosity by measuring the block's water absorption.

(58) The water absorption test is carried out after conditioning the test sample to 205 C. soaked to a constant mass and then oven dried to a constant mass. The loss in mass is expressed in percentage of the mass of the dry sample. The samples were soaked for 3 days which is the minimum period required. The water absorption W.sub.a of each sample in percentage of its mass was calculated using the equation:

(59) $W_a=\frac{M_1-M_2}{M_2}100\%$
where M.sub.1 is the initial mass of the sample in grams M.sub.2 is the final mass of the sample in grams.

(60) The water absorption value is the mean of all the values of the samples. The weathering resistance is determined by tests according to annex D of BS EN 1338 for freeze-thaw resistance or annex E of BS EN 1338 for water absorption. Both tests were carried out in this study.

(61) Binder Mixture Designs and Characteristics:

(62) A range of different Portland cement-free binder compositions were prepared. The paste mixtures (i.e. containing no aggregates or fibres) used are given in Table 10 together with a constant water-to-binder ratio (W/B) by weight of 0.15.

(63) TABLE-US-00011 TABLE 10 Mixture design of paste BOS BPD GGBS Mix code (%) (%) (%) W/B BOS35/BPD10/GGBS55 35 10 55 0.15 BOS40/BPD5/GGBS55 40 5 55 0.15 BOS45/BPD5/GGBS50 45 5 50 0.15 BOS40/BPD10/GGBS50 40 10 50 0.15 BOS50/BPD10/GGBS40 50 10 40 0.15 BOS50/BPD5/GGBS45 50 5 45 0.15 BOS55/BPD5/GGBS40 55 5 40 0.15 BOS60/BPD10/GGBS30 60 10 30 0.15 BOS60/BPD5/GGBS35 60 5 35 0.15

(64) The chemical analyses of the materials used are given in Table 11. LoI denotes Loss on Ignition, in which a sample is ignited at a specified temperature, allowing volatile substances to escape, until its mass ceases to change.

(65) The loss on ignition is used as a quality test and reported as part of an elemental or oxide analysis of a mineral. The volatile materials lost usually consist of combined water (hydrates and labile hydroxy-compounds) and carbon dioxide from carbonates.

(66) TABLE-US-00012 TABLE 11 Chemical analysis of the raw materials carried out using X-ray fluorescence (XRF) techniques as described in ASTM D5381-93 (2009) OPC BOS ROSA PBD GGBS Sample (%) (%) (%) (%) (%) SiO.sub.2 20.00 11.43 45.91 21.86 37.28 TiO.sub.2 0.39 1.41 0.29 0.58 Al.sub.2O.sub.3 6.00 1.60 26.51 3.85 10.79 Fe.sub.2O.sub.3 3.00 28.24 5.23 2.57 0.43 MnO 4.35 0.08 0.02 0.68 MgO 1.50 8.27 2.13 1.13 8.83 CaO 63.00 41.29 6.88 53.40 40.12 Na.sub.2O 1.00 0.02 0.61 0.41 0.27 K.sub.2O 1.00 0.02 1.35 3.64 0.37 P.sub.2O.sub.5 1.48 0.98 0.08 <0.05 SO.sub.3 2.00 0.44 1.37 7.10 0.15 LoI 0.50 3.12 7.11 5.64 1.03

(67) Using the mix codes given in Table 10, density and tensile strength of the mixes are given in Table 12.

(68) TABLE-US-00013 TABLE 12 Average density and tensile strength of paste paving blocks Average density Average tensile (kg/m.sup.3) Strength (MPa) BOS BPD GGBS 14 28 14 Mix Code (%) (%) (%) days days days 28 days BOS35/BPD10/ 35 10 55 2119 2160 2.9 3.1 GGBS55 BOS40/BPD5/ 40 5 55 2091 2116 2.6 3.3 GGBS55 BOS45/BPD5/ 45 5 50 2149 2191 3.1 3.5 GGBS50 BOS40/BPD10/ 40 10 50 2209 2283 3.2 4.5 GGBS50 BOS50/BPD10/ 50 10 40 2248 2304 3.9 5.1 GGBS40 BOS50/BPD5/ 50 5 45 2268 2301 3.0 3.9 GGBS45 BOS55/BPD5/ 55 5 40 2299 2323 2.9 3.9 GGBS40 BOS60/BPD10/ 60 10 30 2323 2360 3.7 4.4 GGBS30 BOS60/BPD5/ 60 5 35 2304 2391 3.1 4.0 GGBS35 BOS35/BPD35/ 35 35 30 2171 2221 3.7 4.8 GGBS30

(69) The BOS50/BPD10/GGBS40 mixture shown in Table 12 above gives the highest strength. This paste was used for the making of the concrete paving blocks.

(70) Chemical analysis of the composition of the overall mixture was carried out using the XRF method. The results of XRD and XRF for this mixture are given in Table 13 and FIG. 7.

(71) Since including aggregates as a constituent of the blocks would reduce their strength, the highest tensile strength mix of BOS50/BPD10/GGBS40 was chosen to continue the concrete paving block investigations.

(72) TABLE-US-00014 TABLE 13 Chemical analysis of the BOS-BPD-GGBS SiO.sub.2 TiO.sub.2 Al.sub.2O.sub.3 Fe.sub.2O.sub.3 MnO MgO CaO Na.sub.2O K.sub.2O P.sub.2O.sub.5 SO.sub.3 LOI Total 21.11 0.51 6.33 12.36 1.92 6.53 39.22 0.32 0.45 0.63 1.10 8.70 99.17

EXAMPLE 4

Paving Blocks and Cement Mixes

(73) Paving blocks were made with the same proportions as used in the factory-produced blocks, i.e. with 14% binder (but with no Portland cement, in contrast to factory-produced blocks) and with 86% stones (i.e. combined aggregates and sand). The mixtures used are given in Table 14. As it can be seen the mean tensile strength values are lower than the factory cement mix and the standard required strength. To improve this, 1.5 percent steel fibres (calculated as described above) were used to increase the required strength. This proved that using fibre with no Portland cement paste can achieve the necessary strength requirement of the paving blocks (see Table 15).

(74) The binder (paste) amount was increased in mixes 3 (given in Table 16) and 4 (Table 17) to improve the strength further. Concrete blocks of mix 3 contained 28 percent by weight binder and the concrete blocks of mix 4 contained 42 percent by weight. The mix designs and results of these concrete mixes are given in Tables 16 and 17 respectively. In the last mixture (mix 5, Table 18) steel fibre was used to enhance the strength and reach the required tensile strength of above 3.6 MPa.

(75) TABLE-US-00015 TABLE 14 Mix 1 - Mixture design and tensile splitting strength at 14 and 28 days for 14 percent binder. Code name BOS50/BPD10/GGBS40 Mix No. 1 BOS BPD GGBS 4 mm-Dust 6 mm Clean Sand 7% 1.4% 5.6% 53% 9% 24% Mean Tensile Tensile Failure Failure Failure Splitting Splitting Age Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKS 1 14 3543.0 23.1 190 76 2429.3 1.0 1.0 2 3551.0 23.9 190 76 2434.8 1.0 3 3548.0 23.5 190 76 2432.7 1.0 1 28 3564.5 23.7 190 76 2444.0 1.0 1.1 2 3578.5 30.1 190 76 2453.6 1.3 3 3561.5 24.3 190 76 2441.9 1.1 4 3568.0 25.4 190 76 2446.4 1.1 5 3578.0 26.8 190 76 2453.3 1.1

(76) TABLE-US-00016 TABLE 15 Mix 2 - Mixture design and tensile splitting strength at 14 and 28 days for 14 percent binder with steel fibre Code name BOS50/BPD10/GGBS40/Steel Fibre 1.5 Mix No. 2 BOS BPD GGBS 4 mm-Dust 6 mm Clean Steel Fibre Sand 7% 1.4% 5.6% 53% 9% 1.5% 24% Mean Tensile Tensile Failure Failure Failure Splitting Splitting Age Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKS 1 14 3512.0 62.5 190 76 2408.1 2.7 2.5 2 3511.5 50.9 190 76 2407.7 2.2 3 3507.0 57.8 190 76 2404.6 2.5 1 28 3517.5 67.1 190 76 2411.8 2.9 3.1 2 3519.5 76.3 190 76 2413.2 3.3 3 3518.0 71.7 190 76 2412.2 3.1 4 3516.5 66.8 190 76 2411.1 2.9

(77) TABLE-US-00017 TABLE 16 Mix 3 - Mixture design and tensile splitting strength at 14 and 28 days for 28 percent binder Code name BOS50/BPD10/GGBS40 Mix No. 3 BOS BPD GGBS 4 mm-Dust 6 mm Clean Sand 14% 2.8% 11.2% 44.4% 7.5% 20.1% Mean Tensile Tensile Failure Failure Failure Splitting Splitting Age Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKS 1 14 3532.1 15.0 190 76 2437 0.65 0.69 2 3529.9 14.6 190 76 2436 0.63 3 3533.0 18.3 190 76 2438 0.79 1 28 3560.0 32.6 190 76 2456 1.41 1.39 2 3558.5 31.9 190 76 2455 1.38 3 3554.6 31.7 190 76 2453 1.37

(78) TABLE-US-00018 TABLE 17 Mix 4 - Mixture design and tensile splitting strength at 14 and 28 days for 42 percent binder Code name BOS5050/BPD10/GGBS40 Mix No. 4 BOS BPD GGBS 4 mm-Dust 6 mm Clean Sand 21% 4.2% 16.8% 35.7% 6.1% 16.2% Mean Tensile Tensile Failure Failure Failure Splitting Splitting Age Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKS 1 14 3665.4 31.2 190 76 2529 1.35 1.35 2 3668.6 34.5 190 76 2531 1.49 3 3663.5 27.9 190 76 2528 1.21 1 28 3666.0 45.1 190 76 2529 1.95 1.95 2 3669.5 46.5 190 76 2532 2.01 3 3665.0 43.7 190 76 2529 1.89

(79) TABLE-US-00019 TABLE 18 Mix 5 - Mixture design and tensile splitting strength at 14 and 28 days for 28 percent binder with steel fibre Code name BOS50/BPD10/GGBS40 Steel Fibre 1.5 Mix No. 5 BOS BPD GGBS 4 mm-Dust 6 mm Clean Steel Fibre Sand 14% 2.8% 11.2% 44.4% 7.5% 1.5% 20.1% Mean Tensile Tensile Failure Failure Failure Splitting Splitting Age Mass load length thickness Density strength strength No (days) (g) (kN) (mm) (mm) (kg/m.sup.3) (N/mm.sup.2) (N/mm.sup.2) BLOCKS 1 14 3619.0 77.7 190 76 2497 3.36 3.4 2 3622.0 78.4 190 76 2499 3.39 3 3625.5 78.9 190 76 2502 3.41 1 28 3645.0 83.3 190 76 2515 3.75 3.7 2 3646.0 87.9 190 76 2516 3.67 3 3648.0 82.4 190 76 2517 3.62 4 3637.3 85.6 190 76 2510 3.56

(80) Table 19 shows the summary of the mix designs and tensile strength results for the five mixes made. As can be seen, mix 3, which has 28 percent binder (paste), can achieve the minimum required strength by adding steel fibres (this is mix 5). However as mix 4 has higher strength, this can also achieve the minimum strength requirement, but mix 4 has 42 percent binder and hence will increase the cost. Due to this reason, mix 3 was selected to add fibres into it.

(81) TABLE-US-00020 TABLE 19 Summary of BOS/BPD/GGBS mixes made with and without 1.5% Steel fibre (percentage by weight). Tensile GGBS BPD BOS SF 4 mm 6 mm Sand Strength (MPa) Mix No. (%) (%) (%) (%) (%) (%) (%) 14 days 28 days Mix 1 (Table 14) 5.6 1.4 7.0 53 9 24 1.0 1.1 Mix 2 (Table 15) 5.6 1.4 7.0 1.5 53 9 24 2.5 3.1 Mix 3 (Table 16) 11.2 2.8 14.0 44.4 7.5 20.1 0.69 1.39 Mix 4 (Table 17) 16.8 4.2 21.0 35.7 6.1 16.2 1.35 1.95 Mix 5 (Table 18) 11.2 2.8 14.0 1.5 44.4 7.5 20.1 3.4 3.7

(82) As can be seen in Table 19, mix 5, containing 28% paste of BOS50/BPD10/GGBS40 with 72% stones and 1.5% steel fibre satisfies the BS EN 1338: 2003 minimum required tensile splitting strength of 3.6 MPa.

(83) Mix 5 containing BOS 14%-BPD 2.8%-GGBS 11.2%-SF 1.5%-Agg. 51.9%-sand 20.1% with W/B of 0.15 satisfies all the requirements of BS EN 1338: 2003 standard including splitting tensile strength, skid/slip resistance, water absorption and freeze/thaw resistance.

(84) This Portland cement-free mix is of the same consistency and properties as the conventional paving block mixtures and can be easily cast in the factory with the usual plant and machineries available.

(85) Density Results:

(86) The average measured densities of paving blocks that were made are presented in Tables 14-18. It can be seen that the densities for different groups are mainly in the same range due to the different specific gravities of the ingredients in each mix. The density ranges between approximately 2400 to 2530 kg/m.sup.3 as expected.

(87) Slip/Skid and Weathering Resistance Test Results:

(88) Table 20 shows skid/slip resistance, water absorption and freeze/thaw resistance for the five mixes of BOS/BPD/GGBS shown in Table 19 and the two factory control mixes made in the laboratory to make them all have the same condition of casting, curing and testing.

(89) TABLE-US-00021 TABLE 20 Durability test results Weathering resistance Slip/Skid Water Freeze/thaw resistance absorp- resistance Mix (BPN) tion (%) (Kg/m.sup.2) Factory Mix I (Control Mix I) 100 5.4 All Factory Mix II (Control Mix II) 92 5.8 blocks <1.0 Mix 1(BOS7/BPD1.4/GGBS5.6) 92 5.9 Mix 2 (BOS7/BPD1.4/GGBS5.6/ 89 6.0 SF1.5) Mix 3 (BOS14/BPD2.8/GGBS11.2) 90 5.8 Mix 4 (BOS21/BPD4.2/GGBS16.8) 92 6.0 Mix 5 (BOS14/BPD2.8/GGBS11.2/ 93 5.9 SF1.5)

(90) The results of slip/skid resistance show that all paving block mixes made in the laboratory have excellent (as defined in Table 9) skid resistant surfaces and the potential for slip is extremely low according to BS EN1338: 2003. In addition, the result of freeze/thaw resistance shows that all mixes meet the British standard of BS EN1338: 2003. On the other hand, the water absorption test should show a result of less than 6% according to the BS EN1338: 2003 standard.

EXAMPLE 5

Paving Block

(91) Paving blocks were made from mix 5 in Table 18. A photograph of one of these blocks is shown in FIG. 8. The top 10 mm surface is made without steel fibres but the main body of the blocks have the steel fibre. This is to make the blocks to have same surface texture as the conventional blocks in the market. The colour of the block is white/gray. The reddish colour is due to the colour of the aggregates and sand used.

(92) Paving blocks made of this mixture satisfies all the industry standards and specifications. The mix is of the same consistency and properties as the conventional paving block mixtures. Even at 14 days, the characteristic splitting tensile strength of paving blocks prepared with ternary mixture of BOS50/BPD10/GGBS40 paste shows better results than the minimum required tensile strength of 3.6 MPa. This mix can be also used for factory production based on economic considerations.