GB2292141A

GB2292141A - Aeration admixture for cementitious compositions

Info

Publication number: GB2292141A
Application number: GB9516232A
Authority: GB
Inventors: Takao Furusawa; Yoshikazu Minomiya
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1994-08-12
Filing date: 1995-08-08
Publication date: 1996-02-14
Also published as: GB9516232D0; FR2723582A1; IT1277894B1; ITRM950541A0; JP3504346B2; DE19528912A1; CH689619A5; ITRM950541A1; JPH0859320A

Description

1 Aeration Admixture 2292141 This invention relates to the entrainment of

air in cementitious compositions and to airentraining compositions for use therein.

Cementitious compositions such as concrete, mortar and grout sometimes need to be aerated, for example, to improve workability or to confer enhanced freeze-thaw durability. This is commonly done by incorporating into the fluid composition an air-entraining admixture (hereinafter "AE admixture"). The act of mixing the cementitious composition causes bubbles to form; these are stabilised by the AE admixture. The materials themselves are described in ASTM C 260 and the subject of aeration is extensively covered in the literature (see, for example, "Concrete Admixtures HandbooV, ed. Ramachandran (Noyes 1984) the disclosures of which are incorporated herein by reference). Examples of AE admixtures include surfactants, sulphate esters of higher alcohols and alkyl sulphonates.

VAiile the known AE admixtures have given excellent performance with many of the known cementitious compositions, they are not universally effective. One example of diminished effectiveness is use in conjunction with cementitious compositions which comprise fly ash. Fly ash is a residue of industrial powdered coal-burning furnaces and is widely used in cernentitious compositions, for example, as a permeability reducer. The problem with fly ashes is that they contain proportions of residual carbon (sometimes referred to as "uncombusted carbon") which survived the combustion process. It is believed that such residual carbon has the ability to absorb AE admixtures and thereby diminish their effectiveness. The problem is compounded by two further factors, (i) coal may be sourced from a wide variety of areas, meaning that the residual carbon content will change from batch to batch, making it difficult to counteract the problem; and (ii) environmental pressures have forced the burning of coal at lower temperatures, thereby leaving even more residual carbon in the resulting fly ash.

Attempts have been made to overcome this problem by developing particular AE agents. However, these AE admixtures have either had poor airentraining properties or have needed a large dose to achieve their effect, or both of these problems.

154-0272 2 It has now been found that a particular blend of materials gives rise to an AE admixture which not only has excellent air-entraining properties but which also achieves these at relatively low doses, even in the presence of fly ash with residual carbon. There is therefore provided, according to the present invention, an air-entraining admixture which 5 comprises (a) a fatty acid-based surface active agent; and (b) a non-ionic surface active agent; the fatty acid-based surface active agent (a) being selected fromC,2.2, oic acids and their alkali metal, lower alkylarnine and lower olamine salts, and the non-ionic surface 10 active agent (b) being selected from materials of the formula Ph(R)-0+CH2CH20+.H where Ph(R) represents a phenyl group substituted with R, R being C,. galkyl and n is from 1 -50.

In a preferred embodiment of the invention, the air-entraining admixture additionally 15 comprises (c) a salt selected from the group consisting of the salts of alkyl sulphonates, alkylaryl sulphonates, sulphate esters of higher alcohols and resinates.

The fatty acid-based surface active agent (a) may be selected from any such substance known to the art. The fatty acid chain in the surfaceactive agent (a) may be saturated or unsaturated, straight chain or branched chain. The fatty acid-based surface active agents (a) may be fatty acids, or preferably, they may be salts of such fatty acids, preferably the salts of alkali metals or amines. The preferred alkali metal salts are those of sodium and potassium, and the preferred salts of amines are preferably those of low molecular weight alkylamines and alkanolamines, preferably those of triethylamine or triethanolamine. Preferred surface-active agents (a) include tall oil fatty acid soap, oleic acid soap, linoleic acid soap and palm fatty acid soap, tall oil fatty acid soap being especially desirable.

154-0272 3 The non-ionic surface active agent (b) as hereinabove defined may be selected from any such material. The substituent R on the phenyl group may be straight chain or branched chain, and is preferably Cg or C9 alkyl. Specific examples include polyoxyethylene nonylphenyl ether and polyoxyethylene octyl phenyl other. The number n of oxyethylene units per molecule is in the range of 1 to 50. It has been found that the value of n has an effect on the ability of the AE admixtures of this invention to cause sufficient air-entraining in the presence of fly ash with a high proportion of residual carbon. For use with such a material, the AE admixture preferably comprises a surface-active agent (b) with from 20 30 oxyethylene units per molecule.

The salts of component (c) of the AE admixture according to the invention may be selected from a wide variety of suitable materials.

The alkyl radicals of alkyl sulphonate and alkyl aryl sulphonate are typically CV"C12 and may be straight chain or branched chain. The salts are preferably alkali metal salts, especially sodium and potassium, or triethanolamine salts. Specific types include wolefin sulfonates, alkyl benzene sulphonates and alkyl sulphates. With regard to the high alcohol sulphates, the alcohols should have at least 12 carbon atoms. Ethylene oxide adducts of such alcohols are also useful, and typical examples include polyoxyethylene alkyl ether sulphates and polyoxyethylene alkyl phenyl ether sulphates. Typical resinates include rosin soap obtained by saponification of pine resin with sodium hydroxide or potassium hydroxide, and sodium, potassium, triethanolamine salts of abietic acid.

The weight ratios of the individual components are from 10 - 90%, preferably from 10 80% (based on active material) of surface-active agent (a), from 90 - 10% from non-ionic surface-active agent (b) and no more than 20% of component (c) when this material is present. The admixture is used at a rate of from 0.00 1 to 0. 1 % by weight actives by weight of cement plus AE admixture. The AE admixtures are generally used in the form of aqueous solutions. They may be used in conjunction with other artrecognised admixtures such as water-reducing agents, AE water-reducing agents, high-range water-reducing agents, high-range AE water-reducing agents, fluidifiers, waterproofing agents, rustinhibiting agents and shrinkage-reducing agents.

154-0272 4 The AE admixture according to the invention is useful for the aeration of cementitious compositions. It is especially useful when used in such compositions which comprise materials comprising residual carbon. It is believed, without limiting the invention in any way, that the residual carbon absorbs conventional AE admixtures. The problems caused by materials such as fly ash are recognised in J15 (Japanese Industrial Standard) A 6201 which specifies that fly ashes of more than 5% loss on ignition should not be used.

However, the AE admixtures of the present invention can be used with fly ashes with loss on ignition in excess of 5%. The invention therefore provides a process of preparing an aerated, fly ash-containing cementitious composition using a fly ash which has a loss on ignition of more than 5%, comprising the addition to the cementitious composition including the fly ash of an air-entraining admixture as hereinabove described. The invention further provides an aerated fly ash-containing cernentitious composition in which the fly ash has a loss on ignition of more than 5%, the composition comprising an air-entraining admixture as hereinabove described.

The invention is further illustrated by the following examples.

Example 1

1) Method of Testing a. Method of Mixing Concrete Fine aggregate, cement, and mixing water (including AE water-reducing agent and AE admixture according to the invention) is introduced into a mixer and mixing is performed for 30 seconds. Coarse aggregate is then introduced and mixing is performed for 90 seconds.

b. Time-dependent Change in Concrete After measuring slump QIS, A 110 1) and air content QIS A 1128) of the concrete mix, the mix is transferred to a tilting-type mixer, and agitation is carried out at an 154-0272 angle of tilting of the mixer of 15 degrees and rotating speed of the mixer of 2 rpm, and air contents at 30 minutes and 60 minutes are measured.

Materials Used a. Cement Ordinary portland cement (specific gravity = 3.16) consisting of equal parts of ordinary portland cements of the Onoda, Sumitomo, and Mitsubishi Material companies are mixed together and used.

b. Fly Ash Commercial fly ash (specific gravity = 2.26, specific surface = 3410 cm'lg, loss on ignition = 3.9%, methylene blue absorption = 0.9 mglg) is used.

C. Fine Aggregate Oi River System pit sand (specific gravity = 2.64, fineness modulus = 2. 76) is used.

d. Coarse Aggregate Crushed stone from Ome, Tokyo (maximum size = 20 mm, specific gravity = 2. 65, fineness modulus = 6.63) is used.

e. Mixing Water Tap water is used.

f. AE Water-reducing Agent An AE water-reducing agent (proprietary name: "Pozzolith" (trade mark) No. 70) 154-0272 6 manufactured by NMB Ltd. is used.

g. AE Adn-dxture The following AE admixtures are used.

As fatty acid-based surface active agent (a):

potassium hydroxide-saponified tall oil As nonionic surface-active agent (b):

the 10-, 20-, 25-, 30-, 40-, and 50-mol ethylene oxide adducts of polyoxyethylene nonylphenyl ether (hereinafter abbreviated to bl, b2, H, M, M and M, respectively).

As ingredient (c):

Dodecylbenzene sodium sulfonate (hereinafter abbreviated to cl) Potassium hydroxide-saponified resin acid (hereinafter abbreviated to c2) (x-olefin sodium sulfonate (hereinafter abbreviated to c3) Polyoxyethylene nonylphenyl ether sodium sulfate (hereinafter abbreviated to c4) is 3) Concrete Mix PropQrtions and Test Results Concrete mix proportions are determined with target slump of 18 2 cm and target air content of 5 0.5 percent, without adding fly ash and with fly ash added as 20 percent of total cement plus fly ash. The mix proportions are given in Table 1.

154-0272 Table 1

7 Fly Ash Water Content Binder Rate Ratio FAl(C+FA) WI(C+FA) Sand- Unit Content (kg1M3) Agg.

Ratio W c FA S G AEWRA sla 0 0.575 46 184 320 - 798 352 800 nil 0.563 45 130 250 64 776 963 800 mI W: water, C: cement, FA: fly ash, S: sand (fine aggregate) G: gravel (coarse aggregate), 10 AEWRA: air-entraining, water-reducing agent Concrete is manufactured according to these mix proportions, and the air contents and time-dependent changes in air contents are tested. The results are given in Tables 2 and 3.

Table 2

Experi- Fly Ash AE Admixture Time-dependent Air Content ment Content Ingredient Dosage Dosage Change (%) No. Rate (a) (b) (c) (%) Increment % Rate Kind Rate Kind Rate Rate 2) % 0 min. 30 min. 60 min.

Comparison 1 0 100 0 0 None 0 0.0035 4.9 5.1 4.8 Example 2 0 90 0 10 0 0.0035 4.8 4.7 4.6 3 0 75 H 25 0 0.0035 5.1 4.9 4.6 4 0 so H so 0 0.0045 5.1 4.9 4.8 0 25 H 75 0 0.0050 5.2 4.8 4.3 6 0 10 0 90 0 0.0100 5.1 4.8 4.4 7 0 0 0 100 11 0 0.0170 5.2 4.5 4.2 8 0 0 0 0 c2 100 0.0006 5.1 4.7 4.4 9 20 0 W 0 c2 100 0.0040 667 5.0 3.0 2.4 20 100 0 0 None 0 0.0255 729 5.2 5.3 5.5 Example 11 20 90 H 10 None 0 0.0250 714 5.3 5.0 4.8 12 20 75 0 25 0 0.0210 600 5.4 5.2 4.9 13 20 50 H so 0 0.0165 367 5.0 4.8 4.6 14 20 25 H 75 0 0.0155 310 5.2 4.7 4.6 20 10 H 90 0 0.0160 160 5.4 5.1 4.6 Comparison 16 20 0 0 100 None 0 0.0300 143 5.1 4.6 3.6 Example

Example 17 20 50 bl so None 0 0.0100 - 5.1 4.9 4.4 18 20 so U so 0 0.0145 - 4.9 4.7 4.5 19 20 50 M 50 0 0.0200 - 5.2 4.8 4.6 20 50 bS 50 0 0.0240 5.0 4.7 4.5 21 20 50 b6 50 0 0.0240 - 5.0 4.8 4.6 A n M ote Dosage of AE admixture so 1 s percent by weight or cement or total quant ty o cement an y - 2) Rate of AE admixture dosage when using fly ash with dosage when not using fly ash as 100 percent.

oc 154-0272 9 Experiments No. 13 and Nos. 17 to 21 in Table 2 are cases where the number of oxyethylene units added to polyoxyethylene nonylphenyl ether is varied, being 10 (b 1), 20 (U), 25 (B), 30 (M), 40 (M) and 50 (M), surface-active agent (a) being held constant. A tendency is seen for the dosage of AE admixture to decrease as the number of 5 oxyethylene units is decreased. Further, as the solubility of nonionic surface-active agent (b) decreases with decreasing number of oxyethylene units, for practical purposes it is desirable for the number of oxyethylene units added to be in the range of 20 to 30.

Experiments No. I to No. 7 are cases where no fly ash has been added, and when the addition rate of ingredient (b) is increased, a tendency is seen for the dosage of AE admixture needed for attaining the target air content to be higher compared with the case where there is no addition of the ingredient (b) (Experiment No. 1). However, in the cases of Experiments No. 10 to No. 16 in which fly ash is used, the dosage of AE admixture needed to attain the target air content, when the addition rates of the ingredient (b) are from 10 to 90 percent, are lower compared with those needed in the cases of surface-active (a) used alone (Experiment No. 10) and nonionic surface-active agent (b) used alone (Experiment No. 16). The smallest dosage is obtained when the ratio of the ingredients (a) and (b) is 25: 75 weight percent. This can be seen with reference to Figure 1, a graph of dosage versus composition.

Experiments No. 8 and No 9 are cases in which a commercial resinate type AE admixture 20 (c2) is used, and although the target air content is obtained immediately after mixing, in the case of the addition of fly ash (Experiment No. 9) air content is greatly reduced with elapse of time.

Table 3 gives the results when dodecylbenzene sodium sulfonate (cl), potassium hydroxidesaponified resin acid (c2), wolefin sodium sulfonate (c3) and polyoxyethylene nonylphenylether sodium sulphate (c4) are used in combination added as (c) to the ingredients (a) and (b). Experiments No. 26 to No. 31 in Table 3 are cases where fly ash is added, and the AE admixtures using these ingredients exhibit excellent properties at small dosages. Experiment No. 32 is a case where potassium hydroxide-saponified resin acid is used at the higher-than-desirable mixing ratio of 25 weight percent, and air content decreases with elapse of time.

Table 3

Experi- Fly Ash AE Admixture Time-dependent Air Content ment Content Ingredient Dosage Dosage Change (%) No. Rate (a) (b) (b) (c) (%) Increment % Rate Kind Rate Kind Rate Rate 2) % 0 min. 30 min. 60 min.

Comparison 22 0 40 H 50 cl 10 0.0040 5.0 4.8 4.7 Example 23 0 40 0 so c2 10 0.0040 4.8 4.6 4.4 24 0 40 0 so c3 10 0.0035 4.9 4.7 4.5 0 40 0 so c4 10 0.0040 4.6 4.4 4.2 Example 26 20 40 0 so cl 10 0.0140 350 5.1 5.0 4.7 27 20 35 0 50 c2 5 0.0155 - 4.8 4.6 4.4 28 20 40 H so c2 10 0.0145 413 4.9 4.8 4.6 29 20 45 0 so c2 Is 0.0135 - 4.7 4.5 4.4 20 40 0 so c3 to 0.0140 414 4.9 4.7 4.5 31 20 40 b3 so c4 10 0.0145 362 5.2 5.0 4.8 Comparison 32 20 25 0 50 c2 25 0.0100 - 5.0 4.0 3.1 Example

Note 'I Dosage of AE admixture solids percent by weight of cement or total quantity of cement 2)Rate of AE admixture dosage when using fly ash with dosage when not using fly ash as 100 percent.

154-0272 11 Example 2

1) Method of Testing a. Method of Mixing Concrete - as per Example 1 Slumps QIS A 1101) and air contents QIS a 1128) of concretes are measured.

2) Materials Used a. Cement Ordinary portland cement (specific gravity = 3.16) consisting of equal parts of ordinary portland cements of the Onoda, Sumitomo and Mitsubishi Material companies mixed together is used.

b. Fly ash Eight lots (FI to F8) of fly ashes of different losses on ignition produced from the same power station are used. The specific gravities, losses on ignition and methylene blue absorptions of these fly ashes are given in Table 5.

C.

Fine Aggregate Oi River System pit sand (specific gravity = 2.64, fineness modules = 2. 76) is used.

d. Coarse Aggregate Crushed stone form Ome, Tokyo (maximum size = 20 mm, specific gravity = 2. 65, fineness modules = 6.63) is used.

e. Mixing Water Tap water is used.

f. AE admixture The AE admixtures described hereinunder are used.

AE1 Potassium hydroxide-saponified tall oil as fatty acid base surface active agent (a) in a proportion of 50 weight percent and a polyoxyethylene nonylphenyl ether adduct having 25 oxyethylene units as nonionic surface active agent (b) in a proportion of 50 weight percent are mixed together.

154-0272 - 12 AE2 Potassium hydroxide-saponified tall oil as fatty acid-based surface agent (a) in a proportion of 35 weight percent, polyoxyethylene nonylphenyl ether adduct having 25 oxyethylene units as nonionic surface active agent (b) in a proportion of 60 weight percent, and potassium hydroxide- saponified resin acid in a proportion of 5 weight percent are mixed together.

AE3 An AE admixture manufactured by NMB Ltd. (proprietary name: No. 303A, with an alkylaryl sulfonate as the main ingredient).

AE4 An AE admixture for fly ash of Totio Kagaku Kogyo (proprietary name: "CemeroP T-80, with polyoxyethylene sorbitan mono-oleate as the main ingredient) 3) Concrete Mix Proportions and Test Results The dosage of AE admixture which gave an air content of approximately 5 percent when using fly ash F4 of roughly median loss on ignition is determined. This dosage is used for the other fly ashes and the fluctuations in air content are measured.

The mix proportions when fly ash is used at 20 percent by total weight of cement plus fly ash are determined by trial mixes. The mix proportions are shown in Table 4.

Table 4

Fly Ash Water- Sand- Unit Content (kg1M3) Content Binder Agg.

Rate Ratio Ratio W c FA S G FAl(C+FA) (%) WI(C+FA) sla 0.60 45 180 240 60 788 981 W: water, C: cement, FA: fly ash, S: sand (fine aggregate) G: gravel (coarse aggregate) The test results are given in Tables 5 and 6. As shown in Table 5, whereas air contents 30using AEl are in a range of 3.7 to 5.2 percent with the coefficient of variation 10.0 percent and air contents using AE2 are in a range of 3.7 to 5.2 percent with the coefficient of 154-0272 13 variation 9.8 percent, the air contents using AE3 are in a range of 2.5 to 7.0 percent with the coefficient of variation 35.2 percent, the air contents using AE4 are in a range of 2.7 to 6.4 percent with the coefficient of variation 25.0 percent. Moreover, when AE I and AE2 are used, the fluctuations in air contents are extremely small and stable air contents are obtained with small dosages, even though the loss on ignition of the fly ashes varies. This contrasts with the results obtained when AE3 and AE4 are used, where the variations are much greater.

Table 5 on next page Table 6 is Kind of AE Admixture Time-dependent Change Fly Ash in Air Content (%) Kind Dosage') (%) 0 min. 30 min. 60min.

Example F4 AE1 0.0350 5.0 4.8 4.5 AE2 0.0290 5.0 4.9 4.6 Comparison AE3 0.0075 4.3 3.0 2.5 Example AE4 0.1200 5.5 5.0 4.7 Note 11 Dosage of AE admixture solids percent by weight of cement or total quantity of cement and fly ash.

Table 6 gives the results of testing time-dependent changes in air contents of concretes using AE1, AE2, AE3 and AE4. The air contents of concretes using AE1 and AE2 show hardly any decline even after elapse of a period of 60 minutes. However, in the case of AE3, compared with AE1 and AE2, although air can be entrained with a low dosage, the reduction in air content after elapse of 60 minutes is considerable. In the case of AE4, although reduction in air content after the elapse of 60 minutes is small, the dosage required is very high in comparison with AE1 and AE2.

Table 5

Example Comparison Example AE admixture Kind AEl AE2 AE3 AE4 Dosage') 0.035% 0.029% 0.0075% 0.12% Fly ash Lot Spec. lg. Loss Methylene Slump Air Slump Air Slump Air Slump Air Grav. (%) Blue Ad- (cm) (cm) (%) (cm) (cm) sorption (Mglg) Fl 2.21 6.84 0.77 15.0 5.2 15.0 5.0 15.5 6.8 16.0 5.7 F2 2.18 7.16 1.12 15.0 5.1 14.5 5.2 14.5 7.0 14.0 5.1 F3 2.16 7.75 0.85 14.5 4.6 14.0 5.1 15.0 6.5 11.0 3.7 F4 2.15 8.04 0.87 14.0 5.0 14.0 5.0 13.5 4.3 17.0 5.5 F5 2.17 8.42 0.85 13.5 5.1 13.0 5.2 14.5 4.8 15.0 6.4 F6 2.20 8.60 1.11 13.0 5.2 13.5 4.6 13.0 3.5 13.5 4.9 F7 2.20 9.06 0.73 13.5 4.6 13.0 4.6 12.0 2.8 11.5 4.4 F8 2.20 10.51 1.29 13.0 3.7 13.5 3.7 12.0 2.5 9.5 2 Air Average (%) - 4.8 - 4.8 - 4.8 - 4.8 Content Standard (%) - 0.48 - 0.47 - 1.7 - 1.2 Deviation Range - 1.5 - 1.5 - 4.5 - 3.7 Variation 10.0 - 9.8 - 35.2 - 25.0 Coefficient _7 Note ') Dosage of AE admixture solids percent by weight of cement or total quantity of cement and fly ash.

154-0272 is

Claims

Claims:

An air-entraining admixture which comprises (a) a fatty acid-based surface active agent; and (b) a non-ionic surface active agent; the fatty acid-based surface active agent (a) being selected from C,2-24 alkanoic acids and their alkali metal, lower alkylamine and lower alkanolan-dne salts, and the non-ionic surface active agent (b) being selected from materials of the formula Ph(R)-0+CH2C1120+.11 where Ph(R) represents a phenyl group substituted with R, R being Cg- galkyl and n is from 1 - 50.

An air-entraining admixture according to claim 1, wherein the admixture additionally comprises (c) a salt selected from the group consisting of salts of alkyl sulphonates, alkylaryl sulphonates, sulphate esters of higher alcohols and resinates.

An air-entraining admixture according to claim 1, wherein the fatty acidbased surface active agent (a) is selected from fatty acids, or salts thereof, preferably the salts of alkali metals or amines.

4. An air-entraining admixture according to claim 3, wherein the alkali metal salts are those of sodium and potassium, and the preferred salts of amines are preferably those of low molecular weight alkylamines and alkanolarnines, preferably those of triethylamine or triethanolarnine.

An air-entraining admixture according to claim 1, wherein the R substituent is selected from octyl and nonyl groups.

154-0272 16 6. An air-entraining admixture according to claim 1, wherein the number n of oxy- ethylene units per molecule is in the range of 1 to 50, preferably from 20 - 30 oxyethylene units per molecule.

An air-entraining admixture according to claim 2, wherein the additive (c) is an alkali metal salt, preferably of sodium and potassium, or triethanolamine salt.

8. An air-entraining admixture according to claim 1, wherein the weight ratios of the individual components are from 10 - 90% (based on active material) of surfaceactive agent (a), from 90 - 10% from non-ionic surface-active agent (b) and, when component (c) is present, no more than 20% thereof.

A process of preparing an aerated, fly ash-containing cementitious composition using a fly ash which has a loss on ignition of more than 5%, comprising the addition to the cementitious composition including the fly ash of an air-entraining adn-fixture according to claim 1 or claim 2.

10. An aerated fly ash-containing cementitious composition in which the fly ash has a loss on ignition of more than 5%, the composition comprising an air- entraining admixture according to claim 1 or claim 2.