BACKGROUND ART Superplasticisers are chemical admixtures, which can maintain an adequate workability of fresh concrete at low water/cement ratios, for a reasonable period of time, preferably without affecting the setting and hardening behaviour of the cementitious system. Concrete prepared at low water/cement ratios will exhibit lower porosity and will thus show enhanced strength and durability.

In order to be classified as a superplasticiser (high range water reducer) the chemical admixture must be able to reduce by 15 to 30% the water required to produce a workable concrete.

In chemical terms, superplasticisers are organic polyelectrolytes, which belong to the category of polymeric dispersants, and are considered as"specialised"dispersing admixtures. Actually, the most commonly used superplasticiser polymers are sulfonated aromatics condensed with formaldehyde. Two such products were developed and optimised: one uses naphthalene as the aromatic building block yielding polynaphthalene sulfonate (PNS); the other uses melamine which leads to polymelamine sulfonate (PMS). These two types of products can achieve comparable water reduction when used at their respective optimal dosage, although they exhibit minor differences in some practical aspects of their application. The main limitation currently reported for these products is their inability to retain the initial slump of the fresh concrete for an extended period, ideally two hours.

Much work has been done to develop new superplasticisers that increase the slump time of fresh concrete without detracting from the quaiities of the hardened concrete product. in U. S. patent no. 5,880,182 (incorporated herein by reference), polycarboxylates are used in conjunction with saccharides. Polycarboxylates can act as very effective superplasticisers. However, polycarboxylate superplasticisers are expensive to produce, making their use less competitive.

Superplasticisers based on naphthalene sulfonate are particularly attractive because of their cost effectiveness. Attempts have been made to increase the slump retention qualities of naphthalene sulfonate/formaldehyde condensates. For example, U. S. patent no.

5,651,817 (incorporated herein by reference) discloses two kinds of superplasticisers: 1) superplasticisers consisting of a copolymer produced by condensation of an oxyethylene-or oxypropylene-aryl compound and an aromatic carboxylic acid with formaldehyde, and 2) superplasticisers consisting of a copolymer produced by condensation of an oxyethylene- or oxypropylene-aryl compound, an aromatic carboxylic acid and an aromatic sulfonate with formaldehyde.

In the same vein, U. S. patent no. 4,759,802 (incorporated herein by reference) discloses the introduction of hydroxy and carboxylate groups into a naphthalene sulfonate/formaldehyde condensate by partial oxidation of the condensate.

Japanese patent no. 60033240 discloses superplasticisers consisting of a formaldehyde condensate with naphthalene sulfonate and naphthalene carboxylic acid.

DISCLOSURE OF THE INVENTION SUMMARY OF THE INVENTION The present invention provides in a first aspect a polymer obtained by condensing with formaldehyde the monomers (A) a sulfonated aromatic compound; and (B): wherein Ri, R2 and R3 may be substituted at any position of either aromatic ring, and are independently selected from H, (CH2) nOH (n=0 to 6), N (CH2CH20H) 2, O (CH2CH20) nH (n=1 to 113), CH20 (CH2CH20) nCH3 (n=1 to 113), O (CH2CH20) nCH3 (n=1 to 113), (CH2) nCOOH (n=0 to 6), and O (CH2) nCOOH (n=1 to 6), and R3 is selected from H and CH20H; and/or (C): wherein R4, Rs and R6 may be substituted at any position of the benzene ring, and are independently selected from H, (CH2) nOH (n=0 to 6), N (CH2CH20H) 2, O (CH2CH20) nH (n=1 to 113), CH20 (CH2CH20) nCH3 (n=1 to 113), O (CH2CH20) nCH3 (n=1 to 113), (CH2) nCOOH (n=1 to 6), and O (CH2) nCOOH (n=1 to 6), and R6 is selected from H and NH2;

wherein the polymer comprises at least one monomer that has at least one carboxyl group, and at least one monomer that has at least one hydroxyl group.

In a second aspect, the invention provides a superplasticiser for fresh concrete, the superplasticiser being obtained by condensing with formaldehyde the monomers (A) a sulfonated aromatic compound; and (B) : wherein Ri, R2 and R3 may be substituted at any position of either aromatic ring, and are independently selected from H, (CH2) nOH (n=0 to 6), N (CH2CH20H) 2, O (CH2CH20) nH (n=1 to 113), CH20 (CH2CH20) nCH3 (n=1 to 113), O (CH2CH20) nCH3 (n=1 to 113), (CH2) nCOOH (n=0 to 6), and O (CH2) nCOOH (n=1 to 6), and R3 is selected from H and CH20H; and/or (C): wherein R4, Rs and R6 may be substituted at any position of the benzene ring, and are independently selected from H, (CH2) nOH (n=0 to 03 6), N (CH2CH20H) 2, O (CH2CH20) nH (n=1 to 113), CH20 (CH2CH20) nCH3 (n=1 to 113), O (CH2CH20) nCH3 (n=1 to 113), (CH2) nCOOH (n=1 to 6), and O (CH2) nCOOH (n=1 to 6), and Rs is selected from H and NH2;

wherein the superplasticiser comprises at least one monomer that has at least one carboxyl group, and at least one monomer that has at least one hydroxyl group.

In a third aspect, the invention provides a method for decreasing the water requirement of a fresh concrete composition comprising adding to cement a plasticising amount of a superplasticiser according to the invention.

In a fourth aspect, the invention provides a dry cement composition, comprising cement and a superplasticiser according to the invention.

In a fifth aspect, the invention provides a wet fresh concrete composition comprising a dry cement composition, according to the invention, mixed with water.

In a sixth aspect, the invention provides a cured concrete product produced by curing a wet fresh concrete composition according to the invention.

DETAILED DESCRIPTION OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described with the aid of the drawings, which show: Figure 1 shows the slumps of fresh concrete (Lafarge T-10 cement) at 10,30,45,60 and 120 minutes, using different wt %'s of a superplasticiser having a molar composition of 91 molar % naphthalene sulfonate and 9 molar % 3-hydroxy-2-naphthoic acid (BON), in comparison with fresh concrete prepared with polynaphthalene sulfonate (regular pNS) as superplasticiser.

Figure 2 shows the slump loss obtained with St. Lawrence Cement and 0.5 wt% superplasticiser of the invention (Example 7), in comparison with 0.6 wt% pNS.

Figure 3 shows the slump loss obtained with Holnam Cement and 0.6 wt% superplasticiser of the invention (Example 7), in comparison with 0.6 wt% pNS.

Figure 4 shows the initial and final setting times (in hours and minutes) for Lafarge T-10 cement with 0.6 wt% superplasticiser of the invention (Example 7), in comparison with 0.7 wt% pNS.

Figure 5 shows compressive strength (in Mpa) at 1,7 and 28 days for concrete prepared with 0.6 wt% superplasticiser of the invention (Example 7), in comparison with 0.7 wt% pNS.

Figure 6 shows the slump of fresh concrete (Lafarge T-10 cement) at 10,30,45,60 and 90 minutes, using 0.6 wt % superplasticiser of the invention (Example 7), in comparison with fresh concrete prepared with 0.2 wt% of an acrylic ester copolymer ("polycarboxylate") as superplasticiser.

Figure 7 shows the air content at 10 and 90 minutes of fresh concrete prepared with 0.6 wt% superplasticiser of the invention (Example 7) in comparison with concrete prepared with 0.2 wt% polycarboxylate superplasticiser.

Figure 8 shows the initial and final setting times (in hours and minutes) for Lafarge T-10 cement with 0.6 wt% superplasticiser of the invention (Example 7), in comparison with 0.2 wt% polycarboxylate O Ç superplasticiser.

Figure 9 shows compressive strength (in Mpa) at 1,7 and 28 days for concrete prepared with 0.6 wt% superplasticiser of the invention

(Example 7), in comparison with 0.2 wt% polycarboxylate superplasticiser.

The polymers of the invention are in themselves novel. They demonstrate superior plasticising ability in fresh concrete, extending slump time while not substantially increasing setting time, and without exhibiting any detrimental effect on the quality of the hardened concrete product.

Preferred compounds for the sulfonated aromatic monomer (A), are those having 6 to 10 carbon atoms in the aromatic nucleus. Preferred are those bearing one sulfonate group. The sulfonated aromatic monomer may also bear up to four (Cl-C6) alkyl groups as substituents on the aromatic nucleus. Examples of compounds suitable as monomer (A) are benzene sulfonate, naphthalene sulfonate, sulfosalicylic acid, sulfophthallic acid, xylene sulfonic acid, toluene sulfonic acid, sulfanilic acid, sulfobenzoic acid, (Cl-C6) alkylbenzene sulfonates and (Cl- C6) alkylnaphthalene sulfonates. Preferred is naphthalene sulfonate, particularly p-naphthalene sulfonate.

In polymers in which only monomer (A) and monomer (B) are used, it is preferred that in the monomer (B), one of Ri and R2 be a group containing an OH group, for example (CH2) nOH (n=0 to 6), or N (CH2CH20H) 2, and the other be a group containing a carboxyl group, for example (CH2) nCOOH (n=0 to 6), or O (CH2) nCOOH (n=1 to 6). It is particularly preferred that one of Ri and R2 be OH, and the other be COOH. The substituents Ri and R2 may be at any position in either of the rings of the naphthalene nucleus. Some examples of compounds suitable as monomer (B) for preparing a polymer of the invention are 3-hydroxy- 2-naphthoic acid (BON) (i. e. Ri is 3-OH, R2 is 2-COOH, and R3 is H) and 4- hydroxymethyl-3-hydroxy-2-naphthoic acid (i. e. Rl is 3-OH, R2 is 2- COOH, and R3 is CH20H).

Some examples of suitable compounds for use as monomer (C) include benzoic acid, o-m-and p-hydroxy benzoic acids, benzyl alcohol, phenylacetic acid, and phenoxyacetic acid.

The polymers of the invention can be obtained by two general routes, which for the purposes of this discussion, are called"one step" and"two step"methods. The one step method is carried out by condensing a mixture of formaldehyde (or formalin) and monomer (A) with at least one of monomers (B) and (C). Included in this are polymers produced by condensation with formaldehyde of monomer (A) and monomer (B), monomer (A) and monomer (C), and monomer (A) with both monomers (B) and (C).

Although the invention is described in terms of condensates with formaldehyde, it would be understood by one skilled in the art that other Cl-6 aldehydes would also work.

For the two step method, a homopolymer of a sulfonated aromatic compound ("poly-monomer (A)") is reacted with monomer (B), and/or monomer (C).

The polymers of the invention comprise at least one monomer with at least one carboxyl group, and at least one monomer with at least one hydroxyl group. The polymer should comprise at least about 1 molar % and can comprise up to 70 molar % of total monomer units which bear a COOH group (In the condensing reaction, the formaldehyde forms a linking methylene group between monomers. In this description, the linking methylene groups are not considered as monomers, and"molar %"in reference to a monomer, with respect to the total, does not include the linking methylene groups). Particularly effective superplasticisers are those in which about 4 molar % to about 10 molar % of the total monomer units bear a carboxyl group.

The polymers of the invention comprise at least one monomer bearing a hydroxyl group. The polymer should comprise at least about 1 molar % and can comprise up to 70 molar % of total monomer units which bear a hydroxyl group. Excellent plasticising properties are conferred if about 4 molar % to about 10 molar % of the total monomer units bear a hydroxyl group.

A preferred polymer of the invention is produced by condensing formaldehyde with naphthalene sulfonate and BON. Good plasticising properties are obtained using a polymer in which the monomer units are about 80 to 98 molar % naphthalene sulfonate and about 20 to 2 molar % BON. Excellent superplasticiser properties are obtained with a polymer in which the monomer units are about 94 molar % naphthalene sulfonate and about 6 molar % BON.

The polymers of the invention can be produced by methods known in the art. In a preferred method, monomer (A) and/or monomer (B) and/or monomer (C) and formalin are heated in water in the presence of an acid catalyst. A preferred acid catalyst is a mineral acid, such as sulphuric acid. The condensation causes the monomers to be linked by linking methylene groups.

The superplasticisers of the invention may be mixed with water and then added to cement, however, the invention further relates to a dry cement composition, comprising a polymer of the invention. The dry cement composition comprises, in addition to a polymer of the invention, at least cement, such as Portland cement, or high alumina cement. It may additionally comprise sand and fine aggregate such as gravel, and other cement additives known to one skilled in the art (see for example: Franklin, A. J.; Cement and Mortar Additives; Noyes Data Corp., USA, 1976; Gutcho, M. H.; Cement and Mortar Technology and Additives; Noyes Data

Corp., USA; Ramachandran, V. S.; Concrete Admixtures Handbook; Noyes Publications, USA, 1984; Ramachandran, V. S.; Concrete Admixtures Handbook; 2nd Edition, Noyes Publications, USA, 1995, all incorporated herein by reference).

The invention further relates to a wet fresh concrete composition, comprising a paste or slurry made by adding a polymer of the invention either as a solid, suspension or solution in water to a conventional cement mixture.

When used as superplasticisers, the polymers of the invention are added to a dry cement composition in amounts of from about 0.1 to 1.0 wt %, preferably 0.3 to 0.8 wt %, most preferably 0.6 to 0.7 wt %, based on the dry weight of the total cement composition (excluding fine aggregate and sand).

A cement composition according to the invention can be used to prepare a wet fresh concrete composition, with a decreased water requirement. The prepared wet fresh concrete compositions exhibit enhanced slump, and extended slump times. Slump and slump time for simple cement pastes may be measured according to a"mini-slump test", as described in Cement, Concrete and Aggregates; Kantro, D. L.; vol. 2,1980, pp 96-102., and slump and slump time for concrete may be measured in accordance with ASTM designation C 143-90a.

Cement compositions prepared with superplasticisers of the invention set within a convenient time frame, allowing construction workers to remove moulds for use elsewhere without undue waiting.

The time of setting for hydraulic cement may be measured according to ASTM designations C 191-92, and C 403/C 403M-95.

Wet fresh concrete compositions according to the invention yield hardened concrete products with high compressive strengths and

excellent durability. Compressive strength may be measured according to ASTM designation C 39-94.

Preferred embodiments of the invention will be further described with reference to the following examples, which are not intended to limit the invention in any way.

Example 1,"one step method", 94 molar % naphthalene sulfonate, 6 molar % BON A condensate of naphthalene sulfonate, BON and formaldehyde was prepared according to the"one step"method, in the following manner: Naphthalene (256 g, 2.00 moles) and 98 % sulphuric acid (214 g, 2.14 moles) were charged into a two litre pressurised reactor, and heated for three hours at 160°C to produce naphthalene sulfonate, which was not isolated. The mixture was cooled to 110°C, and water (295 g), BON (25 g, 0.13 mole) mixed with water (25 g), and 37% formaldehyde (190 g, 2.34 moles) were added (addition of water first cools the mixture so that formaldehyde may be added). The molar percentages of naphthalene sulfonate and BON in the reaction mixture (based on the total of naphthalene sulfonate and BON) were approximately 94 molar % naphthalene sulfonate and approximately 6 molar % BON. The temperature was increased to 128-130°C and stirred for six hours at approximately 36 p. s. i. The mixture was then allowed to cool to 80°C and calcium hydroxide (58 g 38% slurry, 0.30 mole) and 50% sodium hydroxide (162 g, 2.03 moles) were added. After filtration, the product had the following characteristics:

Solids (wt%) 41.57 pH 9.21 Viscosity (cps) 78.20 Free formaldehyde (wt%) 0.14 Sulphate (wt%) 1.39 Example 2,"one step method", 97 molar % naphthalene sulfonate, 3 molar % BON A second condensate of naphthalene sulfonate, BON and formaldehyde was prepared according to the"one step"method, as in Example 1, except that the BON was decreased to 12 g (0.06 mole) and 185 g (2.28 mole) of formaldehyde were used. The molar percentages of naphthalene sulfonate and BON in the reaction mixture (based on the total of naphthalene sulfonate and BON) were approximately 97 molar % naphthalene sulfonate and approximately 3 molar % BON. After filtration, the product had the following characteristics: Solids (wt%) 41.22 pH 8.58 Viscosity (cps) 126.00 Free formaldehyde (wt%) 0.17 Sulphate (wt%) 1.17 Example 3,"two step method"; with poly (naphthalene sulfonate) and BON A condensate of naphthalene sulfonate and formaldehyde (1585 g, 1.679 moles expressed as Clos) was charged into a two litre pressurised reactor without isolation, with BON (41 g, 0.213 moles). The mixture was heated at 108°C for 1.5 hours, after which time it was cooled to 80OC and neutralised with lime and caustic to approximately pH 8. After filtration, the product had the following characteristics:

Solids (wt%) 40.93 pH 7.89 Viscosity (cps) 79.70 Free formaldehyde (wt%) 0.01 Sulphate (wt%) 1.18 Example 4,"two step method", with poly (naphthalene sulfonate) and BON methylol 4-hydroxymethyl-3-hydroxy-2-naphthoic acid, or BON methylol, was synthesised for use as a monomer, as follows: BON (25 g, 0.13 mole) NaOH (50%, 11g, 0.14 mole) and 37% formaldehyde (11 g, 0.14 mole) were heated in water (50 g) to approximately 75-800C at pH 9-10 for 1 hour. Without isolation, the BON methylol was charged into a two litre pressurised reactor with a naphthalene sulfonate/formaldehyde condensate (944 g, 1.00 mole, expressed as CloHs), and the resulting mixture was heated at 100oC for 1.5 hours. It was then cooled to 80OC and neutralised using lime and caustic to approximately pH 8. After filtration, the product had the following characteristics: Solids (wt%) 41.05 pH 8.22 Viscosity (cps) 79.2 Free formaldehyde (wt%) 0.17 Sulphate (wt%) 1.49 Example 5,"one step method", 83 molar % naphthalene sulfonate, 17 molar % naphthalene acetic acid Naphthalene was sulfonated as in example 1. The crude naphthalene sulfonate reaction mixture (765 g) was charged into a two litre pressurised reactor, and water (80 g), naphthalene acetic acid (75 g, 0.40 mole), 98 % sulphuric acid (6 g), and 37% formaldehyde (215 g, 2.65

moles), were added at approximately 80°C. The molar percentages of naphthalene sulfonate and naphthalene acetic acid in the reaction mixture (based on the total of naphthalene sulfonate and naphthalene acetic acid) were approximately 83 molar % naphthalene sulfonate and approximately 17 molar % naphthalene acetic acid. The temperature was increased to 128-130°C and held for 7 hours with stirring at approximately 36 p. s. i. The mixture was then cooled and neutralised with calcium hydroxide (71 g 38 % slurry, 0.36 mole) and 50 % sodium hydroxide (184 g, 2.30 moles). After filtration, the product had the following characteristics: Solids (wt%) 42.20 pH 7.78 Viscosity (cps) 41.2 Free formaldehyde (wt%) 0.17 Sulphate (wt%) 0.86 Example 6,"one step method", 88 molar % naphthalene sulfonate, 12 molar % BON methylol Naphthalene (256 g, 2.00 mol) was sulfonated with 98 % sulphuric acid (214 g, 2.14 moles) as in Example 1. After adding water (200 g), and cooling to approximately 800C, to the reaction vessel were added a BON methylol reaction mixture synthesised according to Example 4 (219 g reaction mixture, containing 0.27 mole BON methylol), and 37 % formaldehyde (179 g, 2.21 moles). The temperature was increased to 128- 1300C and held for 8 hours with stirring at approximately 37-40 p. s. i.

After cooling to approximately 80°C, the mixture was neutralised with calcium hydroxide (58 g 38 % slurry, 0.30 mole) and 50% sodium hydroxide (135 g, 1.69 moles). After filtration, the product had the following characteristics:

Solids (wt%) 41.34 pH 8.36 Viscosity (cps) 103 Free formaldehyde (wt%) 0.17 Sulphate (wt%) 1.07 Example 7,"one step method", 91 molar % naphthalene sulfonate, 9 molar % BON According to the method recited in Example 2, a superplasticiser was made consisting of 91 molar % naphthalene sulfonate and 9 molar % BON. The resulting polymer had the following characteristics: Example7 Solidscontent(% w/w)41.2 Insolubles(% v/v)<0.1 Sodiumsulphate(% w/w) 1. 8 pHof41% solution 8.5 Specificgravity@25°C1.20 Chlorides(ppmasCt-)60 Viscosity@25°C(cps) 75

In the above examples, it is possible to obviate the need for filtering, by neutralising with a hydroxide or oxide (e. g. LiOH, KOH, NaOH, MgO, Mg (OH) 2 or NH40H alone or in combination) which will not form an insoluble sulphate salt on reaction with the excess sulphuric acid.

Slump enhancing and prolonging characteristics of superplasticisers of the invention The above superplasticisers were tested for slump enhancing and prolonging characteristics in simple cement pastes, according to a"mini- slump test", as described in Cement, Concrete and Aggregates; Kantro, D. L.; vol. 2,1980, pp 96-102. As a reference compound, the known superplasticiser polynaphthalene sulfonate (pNS) was used. For the slump trials, a weighed amount of cement was mixed with a solution of the superplasticiser in water, to produce cement paste. The superplasticisers were mixed with cement at various wt% concentrations, based on dry cement. The pastes were all prepared at a water/cement ratio of 0.35. Slump is measured using a standard inverted cone, open at the bottom. The cone is placed with its open bottom on a glass plate, and the cement paste is placed inside the cone. When the cone is lifted, if the cement paste is sufficiently fluid, it will flow out the bottom of the cone, forming a roughly circular blob of cement paste on the glass, which is commonly called a"pie". Slump can be reported as either the diameter or the area of the pie. The slumps for the pastes prepared using pNS and the superplasticisers of the invention were measured at intervals of 10,30,60, 90 and 120. The results are listed in Tables 1 to 4. Table 1. Slump (mm) versus time (minutes) for cement pastes prepared with pNS, Example 1 and Example 2 as superplasticisers (St.

Laurent T-10 cement, water/cement ratio of 0.35) SuperplasticiserpNS(reference)Example1Example2 used Superplasticiser0.60.60.6 concentration(wt%) ondrycementbasis Time(min.)Slump(mm)Slump(mm)Slump(mm) 10 178 202 194 30 174 196 185 60 143 180 170 90 126 171 151 120 107 163 140

From the results in Table 1, it is clear that the two plasticisers of the invention exhibit enhanced initial slump, when compared to the known superplasticiser, pNS, and also extend the slump time considerably. With the superplasticiser of Example 1, the slump after 120 minutes is comparable to the initial slump of a batch prepared with pNS. Table 2. Slump (mm) versus time (minutes) for cement pastes prepared with pNS, Example 3 and Example 4 as superplasticisers (St.

Laurent T-10 cement, waterlcement ratio'0.35) SuperplasticiserpNS(reference)Example3Example4 used Superplasticiser0.60.60.6 concentration (wt%)ondry cementbasis Time(min.)Slump(mm)Slump(mm)Slump(mm) 10 167 184 195 30 162 194 190 60 135 182 185 90 117 177 175 120 98 169 164

From the results in Table 2, it is clear that the two plasticisers of the invention exhibit enhanced initial slump, when compared to the known superplasticiser, pNS, and also extend the slump time considerably. With the superplasticiser of both Examples 3 and 4, the slump after 120 minutes is comparable to the initial slump of a batch prepared with pNS. Table 3. Slump (mm) versus time (minutes) for cement pastes prepared with pNS, and Example 5 as superplasticisers (Lafarge T-10 cement, water/cement ratio of 0.35) SuperplasticiserpNS(reference)Example5 used Superplasticiser0.70.7 concentration(wt%) ondrycementbasis Time(min.)Slump(mm)Slump(mm) 10 129 129 30 119 131 60 107 128 90 94 122 120 82 119

From the results in Table 3, it can be seen that the superplasticiser of Example 5 confers the same initial slump on the cement paste as pNS.

However, unlike pNS, the superplasticiser of Example 5 maintains the slump at close to its initial level at 120 minutes.

Table 4. Slump (mm) versus time (minutes) for cement pastes prepared with pNS, Example 1 and Example 6 as superplasticisers (Lafarge T-10 cement, water/cement ratio of 0.35) SuperplasticiserpNS(reference)Example1Example6 used Superplasticiser0.70.70.7 concentration(wt%) ondrycementbasis Time(min.)Slump(mm)Slump(mm)Slump(mm) 10 163 169 175 30 159 167 173 60 154 165 171 90 145 157 166 120 141 153 160

Comparison of a superplasticiser of the invention with pNS infresh and hardened concrete Tests onfresh concrete The performance of a superplasticiser of the invention (Example 7) was compared with that of polynaphthalene sulfonate ("regular pNS").

The properties of fresh and hardened concrete were investigated under different cements at a water to cement ratio of 0.30.

The composition of the different cements tested is indicated in Table 5. The fine aggregate was natural siliceous sand and the coarse aggregate was local metamorphic limestone having a maximum size of 20 Table 5: Cement Composition ABC (LafargeCement)(St-LawrenceCement)(HoinamCement) Si02(%) 20. 6 22. 3 20. 9 4.05.1Al2O34.4 Fe203 3. 0 3. 0 3. 8 CaO 62. 8 62. 4 64. 2 2.01.3MgO2.8 Na20eq.0. 77 0. 75 0. 32 S03 3. 2 3. 0 2. 7 Lossonignition2.1 1. 8 0.6 C3S 56 53 55 C2S172418 67C3A7 C4AF 9 9 12 BlaineSurface 380 360 400 Area(m2/kg)

Concrete (70# or 170kg each batch) was prepared in a laboratory tilt mixer with a capacity of 100 litres. The mixture proportions of the concrete are indicated in Table 6.

Table 6: Mixture Proportions Water(kg/m3)142.5 Cement(kg/m3)475 FineAggregates(kg/m3)790 CoarseAggregates14mm(kg/m3)1060 Water/Cement 0. 30 RegularPNS 0.7%(6.8t/m3) Example70.5-0.7%(4.7-6.6t/m3)

The slumps of fresh concrete at 10,30,45,60,90 and 120 minutes with different cements at different dosages of superplasticiser were determined according to CSA-A23.2.5C Standards (ASTM C143). Figure 1 shows results obtained with Lafarge T-10 cement.

From Figure 1 it can be seen that beyond a certain threshold dosage, the superplasticiser of Example 7 conveys greatly improved slump retention compared to polynaphthalene sulfonate (REGULAR PNS).

Furthermore, in order to achieve better initial slump and longer slump retention on a 2-hour period, the required dosage of Example 7 is approximately 15% lower than with REGULAR PNS.

Slump losses measured with St. Lawrence cement and Holnam cement are shown in Figures 2 and 3, respectively.

With all tested cements, the superplasticiser of Example 7 maintains concrete workability during a 2-hour period. The dosage required is generally 15% lower than the dosage required for REGULAR pNS.

Air entrainment Air content of concrete was determined at 10 and 90 minutes according to CSA-A23.2.4C Standards (ASTM C231). Concrete made with pNS as superplasticiser or with Example 7 showed less than 3% air content.

Setting time Setting time was measured according to ASTM C-403 standard, on the mortar extracted from the fresh concrete by sieving. A comparison of setting times (initial and final) for concrete prepared with 0.7 wt% pNS versus concrete prepared with 0.6 wt% Example 7 is shown in Figure 4 (Lafarge T-10 cement).

Tests on hardened concrete Compressive strength was determined according to CSA-A23.2.9C Standards (ASTM C39). Compressive strength measured at 1,7 and 28 days for concrete prepared with 0.7 wt% pNS versus concrete prepared with 0.6 wt% Example 7 is shown in Figure 5. From Figure 5, it is evident that the superplasticiser of example 7 gives similar short and long term compressive strengths to those obtained with pNS.

Comparison of a superplasticiser of the invention with an acrylic ester copolymer ("polycarboxylate") infresh and hardened concrete Tests onfresh concrete The performance of a superplasticiser of the invention (Example 7) was compared with that of an acrylic ester copolymer, ("polycarboxylate"). The properties of fresh and hardened concrete were investigated under different cements at a water to cement ratio of 0.30.

The composition of the Lafarge T-10 cement tested is indicated Table 7. The fine aggregate was natural siliceous sand and the coarse aggregate was local metamorphic limestone having a maximum size of 20 mm.

Table 7 : Cement Composition LafargeCement Si02(%)20.6 A12034.4 Fe2O33.0 CaO62.8 MgO2.8 90.77Na2Oeq. SO33.2 LOI 2.1 C3S 56 C2S 17 C3A 7 C4AF 9 BlaineSurfaceArea(m2/kg)380

Concrete (70# or 170kg each batch) was prepared in a laboratory tilt mixer with a normal capacity of 100 litres. The mixture proportions of the concrete are indicated in Table 8.

Table 8: Mixture Proportion Water 142.5 Cement(kg/m3)475 FineAggregates(kg/m3)790 CoarseAggregates14mm(kg/m3)1060 W/C 0. 30 Polycarboxylate 0.2%(3.5t/m3) Example(5.8#/m3)0.6%

The slumps of fresh concrete at 10,30,45,60,90 and 120 minutes were determined according to CSA-A23.2.5C Standards (ASTM C143).

The results shown in Figure 6 were obtained with Lafarge T-10 cement.

Figure 6 clearly shows that the superplasticiser of Example 7 gives a similar slump and slump life to the polycarboxylate superplasticiser.

Air entrainment Air content of concrete was measured at 10 and 90 minutes, according to CSA-A23.2.4C Standards (ASTM C231). The results are shown in Figure 7. It is clear that the superplasticiser of Example 7 does not cause significant air entrainment, whereas the polycarboxylate superplasticiser causes significant air entrainment. Air entrainment decreases the compressive strength of the resulting hardened concrete.

Setting time The setting time of fresh concrete was determined according to ASTM C-403 Standard on the mortar extracted from the fresh concrete by sieving. The setting time for fresh concrete prepared with 0.6 wt%

Example 7 was compared with that obtained using 0.2 wt % polycarboxylate superplasticiser. The results are shown in Figure 8.

Tests on hardened concrete Compressive strength was measured according to CSA-A23.2.9C Standards (ASTM C39). Compressive strengths were measured at 1,7 and 28 days for concrete prepared with 0.6 wt% superplasticiser of Example 7 and compared with those obtained for concrete prepared with 0.2% polycarboxylate superplasticiser. The results are shown in Figure 9.

It is clear that the superplasticiser of the invention gives similar short and long term compressive strengths to those obtained with polycarboxylate superplasticiser.