Abstract:
This invention provides cementiferous compositions having improved flow characterisitics which are given by the incorporation of certain hydroxy acrylate copolymers. Typical copolymers are of acrylic or methacrylic acid with a hydroxyalkyl acrylate or methacrylate and are used preferably in the range 0.01% to 2.5% w/w on the cement in the cementiferous composition. This invention also provides novel additive compositions for use in the cementiferous compositions.

Description:
This application is a continuation-in-part of our copending application Ser. No. 390,167, filed June 21, 1982, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to cementiferous compositions and to additives for use in such compositions, which improve the physical characteristics such as the flow and workability of such compositions. 
     The cementiferous compositions with which this invention is concerned include concretes which comprise cement, coarse and fine aggregates and water; cement pastes which comprise cement and water, and mortars which comprise cement, sand and water; lime, sand and water, or mixtures containing both lime and cement. The invention is also applicable to high-pressure, steam-cured concretes comprising cement, aggregate and water; lime or limestone and siliceous materials such as silica flour and water. 
     The additives with which this invention is concerned are sometimes referred to as placticisers for concrete. Their purpose is to improve the flow characteristics of the cementiferous compositions containing them so that they may be pumped or effectively poured to fill all the spaces in a mould or other structure and yet not have their strength characteristics weakened by the inclusion of excessive amounts of air which, in certain circumstances, would be undesirable. In addition, these additives can be used to design cementiferous compositions with a reduced water content which still retain adequate flow properties for certain purposes and also produce a stronger concrete. 
     Various additives for use in cementiferous compositions have been previously proposed, including for example, lignosulphonates and sodium naphthalene sulfphonate formaldehyde condensates. Details of such materials are set out in &#34;Chemical Admixtures for Concrete&#34; by M. R. Rixom, published by E. and F. N. Spon Limited, London, and by the Halstead Press, a division of John Wiley and Sons Incorporated of New York, USA, where, at page 34, various known additives are considered. 
     Various polymeric materials have been evaluated as plasticiser additives for cementiferous compositions and it has now been found that certain water-soluble copolymers and their soluble salts comprising copolymers of ethylenically polymerizable carboxylic acids and the hydroxy alkyl esters of such acids have particular merit in this application. 
     SUMMARY OF THE INVENTION 
     This invention provides a cementiferous composition comprising, as a plasticizer additive, a copolymer, water-soluble or soluble salt thereof, comprising from 50 to 95 mole % of an ethylenically polymerizable carboxylic acid and from 5 to 50 mole % of a hydroxy alkyl ester of an ethylenically polymerizable carboxylic acid. The additives may conveniently contain an anti-foaming agent, alternatively known as an air detraining agent. 
     In accordance with a further aspect of this invention, there is provided a plasticiser additive composition comprising an aqueous solution of a copolymer or soluble salt thereof, comprising from 50 to 95 mole % of an ethylenically polymerizable carboxylic acid and from 5 to 50 mole % of a hydroxy alkyl ester of an ethylenically polymerizable caboxylic acid and an effective amount of an anti-foaming agent. Suitable and preferred acids and esters are discussed hereinbelow. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Suitable acids include acrylic, methacrylic, crotonic, maleic, fumaric, itaconic, citraconic, and/or aconitic acids and like ethylenically unsaturated acids. The preferred acids are acrylic, methacrylic, and maleic acid, with acrylic or methacrylic acid being most preferred. Suitable esters include the hydroxy ethyl, propyl, butyl, and like esters of the above acids. The preferred are those having hydroxy alkyl substituents of C 1  -C 8 , most preferably hydroxy propyl. Preferred copolymers include copolymers of acrylic acid and hydroxy ethyl acrylate or methacrylate and of acrylic or methacrylic acid and hydroxypropyl acrylate or methacrylate. The most preferred copolymer is that of acrylic acid and hydroxy propyl methacrylate. 
     Preferably, the amount of anit-foaming agent in the composition is in the range 0.1% to 2.0% by weight of the copolymer or salt thereof. Suitable agents include tributyl phosphate, dibutyl phthalate, various water-insoluble alcohols and silicone derivatives. 
     Preferably the mole percentage of the acid in the copolymer is in the range 60 to 85 mole %. Absolute molecular weight of the copolymers of this invention have not been determined. However, apparent molecular weights as calculated relative to polyethylene glycol standards have been determined, using gel permeation chromatography. The apparent molecular weight of the copolymer may be varied over a wide range, the preferred range being 1000 to 15,000, most preferably 1000 to 9000. 
     Precise molecular weights have not been determined for all the copolymers used but in some cases viscosity determinations have been carried out. The preferred viscosity is less than 30 cps. as a 15% by weight aqueous solution in 1 molar NaCl. 
     The amount of hydroxy alkyl acrylate copolymer or soluble salt thereof used is preferably in the range of 0.01 to 2.5%, preferably 0.03 to 2.0%, on the cement in the cementiferous composition. 
     Suitable copolymers may be made by the copolymerization of the hydroxyl alkyl acrylate or methacrylate with the acrylic acid or other appropriate comonomers, using methods known in polymerization technology. The resultant copolymer may be neutralized with a suitable base such as sodium hydroxide or other soluble base and diluted with water to the required concentration for use in the cementiferous compositions and plasticiser additives provided by this invention. 
    
    
     EXAMPLES 
     Materials and Methods 
     (a) Mix Design 
     
         ______________________________________Ordinary Portland Cement              350 kg/m.sup.3ex Blue Circle20 mm Croxden Gravel              780 kg/m.sup.310 mm Croxden Gravel              330 kg/m.sup.3Zone 3Almington Pit Sand 740 kg/m.sup.3% Fines = 40Aggregate/cement = 5.3______________________________________ 
    
     Aggregates were washed, dried for 24 hours on a steam bed and allowed to cool for a further 24 hours. 
     (b) Mixing Procedure 
     The aggregate is placed in the mixer, approximately half the mixing water added and mixed for 30 seconds. After standing for 1 minute the mixer is re-started and the cement added over 30 seconds. The remaining water (containing the additive) is added and mixed for a further 3  minutes. 
     (c) Slump Test, Plastic Density, Compressive Strength 
     To British Standard BS 1881. 
     Results 
     Three copolymers additives (A, B and C) of the invention were prepared as described above and compared with known additives (D and E). 
     
         ______________________________________                          Visc (cps)                          15% solids              Mw   Mn     1 m NaCl______________________________________(i)  75 mole % acrylicacid                    Admix-                          8800 4300 5.525 mole % hydroxy   ture Apropyl acrylate(ii) 67 mole % acrylicacid                    Admix-                          8500 4700 5.333 mole % hydroxy   ture Bpropyl acrylate(iii)80 mole % acrylicacid                    Admix-                          9000 4500 5.720 mole % hydroxy   ture Cpropyl acrylate(iv) Calcium ligno       Admix-sulphonate          ture D42% solution(v)  PolymerizedSodiumnaphthalene         Admix-sulphonate 30%      ture Esolution______________________________________ 
    
     Admixtures A, B and C contained 0.25% by weight of composition of tributyl phosphate (TBP). 
     These materials were evaluated as plasticisers in concrete using a water/cement (W/C) ratio=0.60. 
     Admixture dosage used as 140 cm 3  /50 kg cement as 40% active solutions of their sodium salts. 
     Results are summarized in Table I. 
     
                       TABLE I______________________________________    Plastic             Compressive Strength    Density   Slump     (N/mm.sup.2)Admixture    (kg/m.sup.3)              (mm)      1 day   7 day______________________________________Nil      2330       30       10.0    37.8D        2330       70       9.4     37.5A        2330      160       8.8     37.0B        2330      120       8.3     37.5C        2310      160       7.5     --______________________________________ 
    
     These results show that the copolymer additives of this invention are more efficient plasticisers than D, admixture A being more efficient than B and equivalent to C. 
     All the admixtures show some retardation on 1 day compressive strength. Admixture A gave slightly more retardation than D, with C showing significantly more retardation than A at 1 day. All 7 day compressive strength results were similar. 
     A similar set of experiments were carried out at two different W/C ratios, i.e. 0.64 and 0.56. 
     Results are shown in Tables II and III respectively. 
     
                       TABLE II______________________________________DoseAd-  cm.sup.3 /50    Plastic      Compressive Strengthmix- kg              Density                       Slump (N/mm.sup.2)ture Cement   W/C    (kg/m.sup.3)                       (mm)  1 day  7 day______________________________________Nil  Nil      0.64   2315    55   9.0    34.5D    140      0.64   2315   170   7.1    32.8A    140      0.64   2315   210   6.8    33.5______________________________________ 
    
     
                       TABLE III______________________________________DoseAd-  cm.sup.3 150    Plastic      Compressive Strengthmix- kg              Density                       Slump (N/mm.sup.2)ture Cement   W/C    kg/m.sup.3)                       (mm)  1 day  7 day______________________________________Nil  --       0.64   2330   55     9.0   34.5D    140      0.56   --     10    --     --A    140      0.56   2350   60    12.4   43.3E    500      0.56   2350   80    --     42.7______________________________________ 
    
     It can be seen that D is ineffective at a W/C of 0.56 whereas admixture A still gives a slump similar to the control with a water reduction of 12.5%. E required dosage of 500 cm 3  /50 kg cement to give a similar water reduction. 
     Compressive strengths are significantly higher than control at 1 and 7 days. 
     Further work was done to determine the effect of changes in the molecular weight and molar ratio of the components of the copolymer. Details of the copolymer are set out in Table IV and the effects on concrete are shown in Table V. 
     
                       TABLE IV______________________________________Acrylic Acid (Na salt)-Hydroxy Propyl Acrylate Copolymers                                15%Copolymer                    Visc (cps)                                Copolymer(moles) Sample   Solids      25% in  in 1M NaClAA   HPA    No       w/w   pH  water   (cps)______________________________________3    1      (361/11) 40.0  7.5 37      5.0       (361/8)  41.0  7.5 42      5.9       (361/12) 40.0  7.5 50      6.62.5  1      (361/16) 46.8  7.1 38      5.1       (361/15) 45.5  7.3 43      5.4       (361/25) 44.3  7.5 55      6.92    1      (361/18) 44.4  7.4 38      5.9       (361/19) 42.6  7.6 42      6.8       (361/26) 38.0  7.6 58      7.7______________________________________ AA = Acrylic acid HPA = Hydroxy propyl acrylate. 
    
     These copolymers were evaluated in a 350 kg/m 3  OPC concrete mix design. 
     
         ______________________________________Mix Design______________________________________OPC ex Blue Circle     350 kg/m.sup.320 mm Croxden Gravel   780 kg/m.sup.310 mm Croxden Gravel   330 kg/m.sup.3Zone 3 Almington Pit Sand                  740 kg/m.sup.3% Fines = 40Aggregate/cement = 5.3______________________________________ 
    
     The copolymers were dosed at 0.28% bwc as 30% aqeuous solutions (+0.25% by weight of the composition tributyl phosphate as air entraining suppressant) and the results are detailed below: 
     
                       TABLE V______________________________________                               Compressive                 Molecular     Strength                 Weight as     (N/mm.sup.2)Sample Mole            function of                         Slump 1    7    28No.   % AA            viscosity                         (mm)  day  day  day______________________________________361/11 75            ↓    110   8.6  31.4 39.6361/8 75            ↓                   Increasing                           104 90                                 8.8  31.4 40.4361/12 75            ↓    80    8.3  30.9 40.8361/16 71.4          ↓                   Increasing                           110   8.5  31.9 41.3361/15 71.4          ↓                   Increasing                           95    8.8  31.7 38.6361/25 71.4          ↓    90    8.6  31.5 39.0361/18 67            ↓    105   8.4  30.6 38.0361/19 67            ↓                   Increasing                           105   8.1  31.2 37.0361/26 67            ↓    95    7.4  29.5 37.8Nil   Nil           ↓                   --      20    9.8  30.4 40.0______________________________________ AA = Acrylic acid. 
    
     These results suggest that all the copolymers show some retardation of 1 day compressive strength, being most significant with the 67 mole % AA (2/1) polymers. 7 and 28 days compressive strengths are very similar to control concrete except perhaps with the 67 mole % AA polymers which are somewhat lower. Plasticising action is shown to be related to the molecular weight/viscosity of the polymers and tends to increase as molecular weight/viscosity decreases. 
     The super-plasticising properties of the additives provided by this invention were compared with admixture E. 
     The additive of the invention was a 2.5/1 AA/HPA copolymer and comprised: 
     75 parts of a 40% solids copolymer solution 
     25 parts of water, and 
     0.25 parts tributyl phosphate (TBP) 
     All parts by weight and referred to as EP 82/27. 
     Super-plasticising Properties 
     Flowing Concrete 
     Super-plasticised concrete mixes were produced using composition A and EP 82/27 at a range of dosage levels. Workability was measured using the flow table method (DIN 1048). Flow &#34;A&#34; refers to the spread before tamping and flow &#34;B&#34; to the spread after the prescribed number of tamps. 
     
         ______________________________________Mix Design______________________________________OPC ex Blue Circle 350 kg/m.sup.320 mm Croxden Gravel              780 kg/m.sup.310 mm Croxden Gravel              330 kg/m.sup.3Zone 3 Almington Sand              740 kg/m.sup.3% Fines = 40Aggregate/cement = 5.3Water/cement = 0.66______________________________________ 
    
     Results are shown in Table VI. 
     
                                           TABLE VI__________________________________________________________________________ Admixture Dose       Flow Flow                     Compressive Strength % by wt.       Slump            &#34;A&#34;  &#34;B&#34; (N/mm.sup.2)Admixture OPC   (mm) (cm) (cm)                     1 day                         7 day                             28 day__________________________________________________________________________Nil   --    50   20   --  9.4 31.3                             38.0Admix E 0.3   --   21,23                 47,47                     8.1 29.7                             38.5Admix E 0.5   --   25,25                 51,51                     9.5 32.0                             39.5Admix E  0.74 --   26,27                 55,56                     8.3 32.0                             39.0Admix E 1.0   --   40,40                 63,61                     9.5 32.0                             37.3EP 82/27 0.1   --   22,22                 50,50                     8.6 31.3                             38.0EP 82/27 0.2   --   26,26                 53,52                     9.8 32.0                             38.5EP 82/27 0.3   --   27,28                 56,55                     7.7 31.5                             37.5EP 82/27 0.4   --   35,33                 62,58                     7.4 31.5                             37.0__________________________________________________________________________ 
    
     EP 82/27 is shown to produce highly workable concrete at much lower dosages than admixture E. The flow properties obtained by using admixture E at typical super-plasticiser dosage rates (0.6-1%) can be achieved by EP 82/27 at rates of addition in the range 0.2-0.4%. 
     High Range Water Reduction 
     Admixture E and EP 82/27 were used to produce high range water reductions (constant workability) in the following mix design. 
     
         ______________________________________OPC ex Blue Circle  350 kg/m.sup.320 mm Croxden Gravel               780 kg/m.sup.310 mm Croxden Gravel               330 kg/m.sup.3Zone 3 Almington Pit Sand               740 kg/m.sup.3% Fines = 40Aggregate/cement = 5.3______________________________________ 
    
     Results shown in Table VII. 
     
                                           TABLE VII__________________________________________________________________________  Admixture  Dose %             Compressive Strength  by wt    Slump               % Water                     (N/mm.sup.2)Admixture  OPC   W/C           (mm)               Reduction                     1 day                         7 day                             28 day__________________________________________________________________________Nil    --    0.66           60  --    8.2 27.3                             38.5Admix E  0.3   0.61           55   7.4  9.1 32.7                             42.0Admix E  0.5   0.59           50  10.9  11.0                         32.6                             43.0Admix E  1.0   0.55           60  15.7  12.9                         39.0                             45.0Admix E  1.5   0.53           50  19.6  15.6                         44.4                             46.8Admix E  2.5   0.51           45  22.8  15.0                         44.0                             53.0EP 82/27  0.1   0.59           50  10.0  10.0                         33.1                             44.0EP 82/27  0.2   0.59           55  10.9  10.2                         36.3                             46.0EP 82/27  0.5   0.55           55  15.7  11.1                         39.8                             49.8EP 82/27  0.8   0.53           60  19.6  11.1                         44.0                             51.0EP 82/27  1.5   0.51           55  22.8   9.2                         45.0                             56.8__________________________________________________________________________ 
    
     Compared with admixture E, EP 82/27 is shown to perform very efficiently as a water reducing agent, producing similar increases in compressive strength at much lower doses. 
     Evaluation of Range of Hydroxy Monomers 
     Abbreviations used: 
     AA=Acrylic acid 
     MAA=Methacrylic acid 
     HPA=Hydroxy propyl acrylate 
     HPMA=Hydroxy propyl methacrylate 
     HEMA=Hydroxy ethyl methacrylate 
     HEA=Hydroxy ethyl acrylate 
     TBP=Tri-n-butyl phosphate 
     Copolymers were prepared as 30% w/w active solutions as sodium salts in water (+0.25% TBP). 
     
         ______________________________________               Visc (cps)               15% IM               aqueous NaCl______________________________________F       2.5/1 molar              MAA/HPA    7.4G       2.5/1 molar              AA/HEMA    5.1H       2.5/1 molar              AA/HPMA    5.4J       2.5/1 molar              AA/HEA     3.4______________________________________ 
    
     The copolymers were evaluated in concrete in comparison with EP 82/27 (viscosity 5.1 cps) (2.5/1 molar AA/HPA). 
     
         ______________________________________Mix Design______________________________________OPC                  3.5 kg20 mm Croxden Gravel 7.8 kg10 mm Croxden Gravel 3.3 kgZone 3 Almington Pit Sand                7.0 kg______________________________________ 
    
     Admixtures were dosed at 0.4% bwc in order to produce flowing concrete. 
     Workability of the concrete was measured using &#34;Flow Table&#34; according to DIN 1048. 
     Flow A refers to spread before tamping and Flow B to the spread after tamping. 
     w/c=0.61 
     
                       TABLE VIII______________________________________                           Compressive Strength   Slump   Flow A   Flow B (N/mm.sup.2)Admixture   (mm)    (cm)     (cm)   7 day  28 day______________________________________Nil     90      23       40     33.2   44.8EP 82/27   --      31       60     34.5   44.0F       --      32       61     32.5   44.3G       --      35       61     34.5   45.2H       --      39       64     32.8   44.3J       --      32       60     33.0   45.5______________________________________ 
    
     Using the same mix design, admixtures G and H were re-evaluated in comparison with both EP 82/27 and admixture E in order to determine 1 day compressive strengths and &#34;set&#34; times. 
     
                       TABLE IX______________________________________                                 Compressivead-   Admixture                       Strengthmix-  Dose      Slump   Flow A Flow B (N/mm.sup.2)ture  % bwc     (mm)    (cm)   (cm)   1 day______________________________________Nil   --        90      23     40     9.5EP 82/27 0.4       --      43     63     8.1G     0.4       --      43     66     8.8H     0.3       --      44     67     8.4H     0.4       --      49     68     8.2Admix E 1.0       --      48     66     8.5______________________________________ 
    
     Penetration tests were conducted using a Proctor Needle (according to ASTM No. C-403-80) and the results are summarized below: 
     
                       TABLE X______________________________________    Admixture  Extension of Set over Control    Dose       (hours)Admixture    % bwc      Initial     Final______________________________________EP 82/27 0.4        2.2         2.2G        0.4        1.4         1.6H        0.3        1.0         1.3H        0.4        2.7         2.5Admix E  1.0        2.7         2.5______________________________________ 
    
     The plasticising performance of a range of hydroxy acrylates/methacrylates demonstrates that the AA/HPMA copolymer is preferred. 
     The use of methacrylic acid instead of acrylic acid in EP 82/27 gives similar results. 
     In concretes of similar initial high workability set retardation is in the following order (2.5/1 copolymers with AA). 
     
         ______________________________________Admixture E ≧       HPA &gt;     HEMA &gt;     HPMA(retards most)                   (retards least)______________________________________ 
    
     Various copolymers were made to demonstrate the effect of varying the AA/HPMA ratio of the general type of admixture H. 
     
         ______________________________________                 Visc (cps)                 15% solids in                 1M aqueous NaCl______________________________________K   2/1    molar   (67 mole                      AA/HPMA  5.3              % AA)L   2.5/1  molar   (71 mole                      AA/HPMA  5.1              % AA)M   3.0/1  molar   (75 mole                      AA/HPMA  6.4              % AA)N   5.0/1  molar   (83 mole                      AA/HPMA  5.2              % AA)P   1/0    molar   (100 mole                      AA       6.6              % AA)______________________________________ 
    
     Each copolymer was made up into the following additive composition 
     30% Copolymer as Na salt 
     70% Water 
     +0.25% TBP 
     
         ______________________________________Mix Design______________________________________OPC                  350 kg/m.sup.320 mm Croxden Gravel 780 kg/m.sup.310 mm Croxden Gravel 330 kg/m.sup.3Zone 3 Almington Pit Sand                700 kg/m.sup.3Water                200 kg/m.sup.3Water/cement = 0.57% Fines = 38.7Aggregate/cement = 5.2Admixture dose = 0.4% bwc.______________________________________ 
    
     
                       TABLE XI______________________________________                           Compressive Strength   Slump                   (N/mm.sup.2)Admixture   (mm)    Flow A   Flow B 1 day  7 day______________________________________Nil     60      20        *     11.2   38.0K               32       56     9.5    37.0L               30       56     9.6    38.0M               28       53     8.8    35.5N               24       50     8.6    38.3P               20       44     8.0    34.7______________________________________ *No cohesion 
    
     Results show mole % AA in copolymer significantly affects performance as a plasticiser and to some extent early compressive strength development and support the preferred 60 to 85 mole % acrylic acid content. 
     Comparisons were made with two other commercially-available plasticisers. They were: 
     Composition B-a calcium lignosulphonate 43% w/w solution 
     Composition C=a polysaccharide-based water reducing agent 
     
         ______________________________________Mix Design______________________________________OPC ex Blue Circle  350 kg/m.sup.320 mm Croxden Gravel               780 kg/m.sup.310 mm Croxden Gravel               330 kg/m.sup.3Zone 1 Almington Pit Sand                70 kg/m.sup.3Zone 2 Almington Pit Sand               670 kg/m.sup.3Aggregate/cement = 5.3% Fines = 40______________________________________ 
    
     
                                           TABLE XII__________________________________________________________________________   Admixture            Plastic  Compressive Strength   Dose     Density                 Slump                     (N/mm.sup.2)Admixture   % bwc W/C            (kg/m.sup.3)                 (mm)                     1 day                         7 day                             28 day__________________________________________________________________________Nil     Nil   0.67            2360  45 3.1 31.8                             40.2EP 82/27    0.05 0.67            2360  85 3.1 31.7                             39.3EP 82/27   0.1   0.67            2360 160 2.8 31.0                             39.6EP 82/27   0.2   0.67            2360 195 3.1 31.3                             40.0Comp B  0.2   0.67            2360 140 3.1 32.4                             41.2Comp B  0.3   0.67            2360 150 2.3 30.7                             39.1Comp B  0.4   0.67            2360 180 2.3 31.2                             41.0Comp C  0.2   0.67            2360 175 3.3 33.1                             40.5Comp C  0.3   0.67            2360 190 2.7 33.6                             41.2Comp C  0.4   0.67            2360 220 1.0 33.9                             43.0__________________________________________________________________________ 
    
     At the dosage levels used here EP 82/27 shows no retardation of 1 day compressive strength. Increased dosages of composition B and composition C to obtain higher workability result in retardation of early strength. 
     7 and 28 day compressive strength results are all similar. 
     EP 82/27 is shown to perform as a highly effective low dosage plasticizer. 
     Comparing the dosage levels required to produce concrete with, e.g. 150 mm slump: 
     
         ______________________________________EP 82/27             0.09% bwcComposition B        0.25% bwcComposition C        0.16% bwc______________________________________