A viscosity reducing agent for low water-cement ratio concrete and its application

Abstract

The present invention discloses a viscosity reducer for low water-cement ratio concrete and its application. The viscosity reducer of the present invention is prepared by mixing three components A, B and C in a mass ratio of (50-80): (30-20): (0-20); the component A is selected from any one or more of small molecule diols and small molecule diol derivatives; the component B is selected from any one or two of glycerol and glycerol polyoxyethylene ether derivatives in any proportion; the component C is pentaerythritol polyoxyethylene ether. The structure of the small molecule polyol and its derivative in the viscosity reducer component of the present invention is a low-density, non-ionic and non-adsorptive molecule with a spacing effect, which can be effectively dissolved in the interstitial pore solution, solving the problem that the interstitial water between particles cannot be released under low water-cement ratio, effectively reducing the viscosity of mortar or concrete, and significantly improving the fluidity of mortar, and moderately improving the expansion of concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of building admixtures, and particularly relates to a concrete viscosity reducer suitable for low water-binder ratio conditions and application thereof. Background Art

[0002] High-performance concrete (HPC) and ultra-high-performance concrete (UHPC) use low water-binder ratio and high bulk density to achieve excellent concrete strength and workability. PCE water reducer can achieve appropriate fluidity and slump, but the viscosity of concrete will rise rapidly at low water-binder ratio, which brings excessive viscosity and long flow time to the construction of pumped concrete and self-leveling concrete. At present, the research on the viscosity of concrete with low water-binder ratio mainly stays in ordinary concrete and high-performance concrete (HPC), especially the water-binder ratio of UHPC is generally lower than 0.27, and even 0.14 in extremely low cases. Therefore, the method of reducing viscosity of ordinary concrete may not be applicable to UHPC.

[0003] The current reports on the viscosity reduction methods of UHPC mainly adjust the mix ratio of silica fume, mineral powder, steel fiber and other inert admixtures to optimize the grading of concrete with low water-cement ratio and introduce a strong ball effect, thereby reducing the internal friction of the concrete and reducing the viscosity. However, the disadvantage of this method is that the dosage of viscosity adjustment through physical methods is large, and the quality of high-quality silica fume, stone powder, etc. is difficult to control, and the cost is relatively high.

[0004] In the report on the use of chemical admixtures to reduce viscosity, patent CN201610331188.7 proposed a viscosity reducer based on 4-hydroxybutyl vinyl ether, unsaturated amide and unsaturated phosphate as raw materials, the molar ratio of the three is 1: (0.5-3): (0.01-0.1), the weight average molecular weight of the viscosity reducer is mainly concentrated between 55000 and 300000, so the molecular weight of the viscosity reducer is relatively large, and its mechanism of action is mainly concentrated in the following aspects: on the one hand, the dispersibility is improved by the hydrolysis of the ester type water reducer in the alkaline solution, and the hydrolyzed phosphate group can provide a stronger electronegativity than the carboxyl group; on the other hand, the TOMS effect of the polymer is used to improve the construction performance and reduce the viscosity of pumped concrete. Although the cone inversion time of mortar and concrete becomes faster, the viscosity reducer is not conducive to the release of free water between particles due to its large molecular weight and the enhanced cross-linking effect between cement and adhesive.

[0005] Wu Wei et al. reduced the viscosity of slow-setting soil by synthesizing viscosity-reducing carboxylic acids in "Synthesis and Characterization of Highly Adaptable Phosphate-Modified Polycarboxylic Acid Water-Reducing Agents". This patent introduces a phosphate group structure with a strong negative charge. The main chain of the PCE water-reducing agent modified with phosphate groups usually has a stronger electronegativity, which combines steric hindrance and stronger repulsion to affect the particle dispersion effect and thus reduce the viscosity of concrete. However, the disadvantage of this method is that the experimental results at a water-binder ratio of 0.29 were verified, and the viscosity-reducing effect at the UHPC water-binder ratio was not very significant.

[0006] Patent CN201810601948.0 A concrete viscosity reducer and its preparation method reports the synthesis of a polymer viscosity reducer with certain water-reducing properties. The method includes two steps: esterification reaction and free radical polymerization. The polymer structure is a "comb-shaped structure". The main chain is composed of acrylic acid and isobutyl acrylate, and the side chain is composed of maleic anhydride-polyethylene glycol esterification structure. Therefore, the product has a good water-reducing effect. The different polyvinyl alcohol chain lengths form a good steric hindrance effect to prevent the van der Waals attraction between particles, thereby achieving the purpose of water reduction and viscosity reduction. .

[0007] Developing a concrete viscosity reducer that can be well adapted to the existing water-reducing agent system, has an outstanding viscosity reduction effect, and is suitable for low water-cement ratio conditions will be of great benefit to the construction and working performance of concrete. Summary of the invention

[0008] In order to overcome the above-mentioned defects, the purpose of the present invention is to provide a viscosity reducer for low water-cement ratio concrete, which has the characteristics of simple preparation method, excellent viscosity reducing effect when used in combination with a water reducer, and is suitable for low water-cement ratio mortar or concrete.

[0009] Another object of the present invention is to provide application of the above concrete viscosity reducer.

[0010] The technical solution of the present invention is as follows:

[0011] The present invention provides a viscosity reducer for low water-cement ratio concrete, which is prepared by mixing three components A, B and C in a mass ratio of (50-80): (30-20): (0-20);

[0012] The component A is selected from any one or more mixtures of small molecule diols and small molecule diol derivatives;

[0013] The component B is selected from any one of glycerol and glycerol polyoxyethylene ether derivatives or a mixture of two of them in any proportion;

[0014] The C component is pentaerythritol polyoxyethylene ether.

[0015] The small molecule diol in the A component is selected from any one or more of all straight-chain and branched diols of C3 to C8 and mixed in any proportion, and the small molecule diol derivative is selected from one or more of polyoxyethylene ether derivatives of straight-chain\branched diols and mixed in any proportion;

[0016] The small molecule diol is selected from diethylene glycol, triethylene glycol, tetraethylene glycol and any one or more monomers represented by the general structural formula (I) and mixed in any proportion. The general formula of the small molecule diol derivative is shown in (II).

[0017]

[0018] In the above general formula (I) and (II), a=1-6, a1=1-6, b=2-7, R and R1 are independently selected from -H, -CH3, -CH2CH3 or -CH(CH3)2.

[0019] The structure of the glycerol polyoxyethylene ether derivative of the B component is shown in the following formula (III), wherein c=2-7;

[0020]

[0021] The C component is pentaerythritol polyoxyethylene ether, and its general structural formula is (IV), wherein d=2-7;

[0022]

[0023] According to the second aspect of the present invention, the application of the viscosity reducer is also provided. The conventional dosage of the viscosity reducer is 0.2%-4% of the total cementitious material mass, and the optimal dosage is 0.5%-2%, and the dosage is a pure solid dosage. If the dosage is too low, the wetting of cement particles is insufficient, the release of cement interstitial fluid is insufficient, the synergy between the water reducer molecules is insufficient, and the viscosity improvement is not obvious at a low water-cement ratio. If the dosage is too high, the cost is likely to be high, and the effects in the solution are balanced, and the dispersion promoting effect and viscosity reducing effect of the water reducer cannot be further improved. In actual use, engineers can select within this range according to the application scenario.

[0024] Beneficial effects of the present invention:

[0025] The present invention is different from the widely reported viscosity-reducing carboxylic acid water-reducing agent or admixture viscosity-reducing work, and the prior art rarely involves the viscosity-reducing technology of small molecule compounds; the present invention relates to the structure of small molecule polyols and their derivatives contained in the viscosity-reducing agent component, which are low-density, non-ionic and non-adsorbing molecules with a spacing effect, and can be effectively dissolved in the interstitial pore solution, solving the problem that interstitial water between particles cannot be released under low water-binder ratios, preventing the unabsorbed polycarboxylic acid water-reducing agent from bridging the particles under low water-binder ratio conditions, releasing more free water, effectively reducing the viscosity of mortar or concrete, and significantly improving the fluidity of mortar, and moderately improving the expansion of concrete. DETAILED DESCRIPTION

[0026] The following examples describe the concrete viscosity reducer prepared by the present invention in more detail, and the purpose is to enable people familiar with the art to understand the content of the present invention and implement it accordingly, but these examples do not limit the scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be included in the protection scope of the present invention.

[0027] Example 1

[0028] A concrete viscosity reducer, which consists of diethylene glycol: glycerol: pentaerythritol polyoxyethylene ether (d=3) in a mass ratio of 50:30:20.

[0029] Example 2

[0030] A concrete viscosity reducer, the components of which are composed of A (1,3-propylene glycol (a=1)+dipropylene glycol polyoxyethylene ether (b=2)):B (glycerol: glycerol alcohol polyoxyethylene ether (c=2)) in a mass ratio of A (20+50):B (15:15).

[0031] Example 3

[0032] A concrete viscosity reducer, the components of which are (tetraethylene glycol + 2-methyl-3,6-hexanediol polyoxyethylene ether (R1 is -CH(CH3)2, b=5)): glycerol: pentaerythritol polyoxyethylene ether (d=7)=(35+35):(14+6):10.

[0033] Example 4

[0034] A concrete viscosity reducer, the components of which are composed of A (1,7-octanediol (a=6)): B (1,4-butanediol monomethyl ether+glycerol polyoxyethylene ether (c=7)): C (pentaerythritol polyoxyethylene ether (d=3))=50:(20+10):20.

[0035] Example 5

[0036] A concrete viscosity reducer, the components of which are A (2-methyl-2,4-pentanediol): B (glycerol + glycerol polyoxyethylene ether (c=5))=(70):(20+10).

[0037] Example 6

[0038] A concrete viscosity reducer, the components of which are composed of A (1,4-butanediol + triethylene glycol + heptaethylene glycol): B (1,4-butanediol monomethyl ether + glycerol polyoxyethylene ether (c=2)): C (pentaerythritol polyoxyethylene ether (d=3)) = (20+20+20): (20+15): 5.

[0039] Comparative Example 1 (Component A uses a diol derivative in the form of monomethyl ether)

[0040] A concrete viscosity reducer, the components of which are A (1,4-butanediol monomethyl ether) + B (glycerol

[0041] The composition of polyoxyethylene ether (c=7) is 60:40.

[0042] Comparative Example 2 (component B uses glycerol polyoxyethylene ether, c>7)

[0043] A concrete viscosity reducer, the components of which are composed of A (diethylene glycol + dipropylene glycol dimethyl ether): B (glycerol polyoxyethylene ether (c=10))=70:30.

[0044] Comparative Example 3 (B component derivatives using non-hydroxyl terminal derivatives)

[0045] A concrete viscosity reducer, the components of which are composed of A (1,4-butanediol monomethyl ether): B (glycerol polyoxyethylene ether trimethyl ether (c=5)): pentaerythritol polyoxyethylene ether (d=3)=70:20:10.

[0046] Comparative Example 4 (Component A a>7, R is -CH2CH2CH2CH3)

[0047] A concrete viscosity reducer, the components of which are composed of A (decanediol): B (glycerol polyoxyethylene ether (c=10)): pentaerythritol polyoxyethylene ether (d=3)=70:20:10.

[0048] Application Examples

[0049] Application Example 1

[0050] The viscosity reducer prepared in Examples 1-4 was added to the mortar to test the performance of the mortar. The mortar test used 900 g of Onoda cement PO 42.5 cement, 1350 g of standard sand, 135 g of silica fume, and 3.6 g of Subote polycarboxylic acid water reducer (50% wt) (0.2% relative to the amount of the adhesive); the blank mortar test used Onoda cement PO 42.5 cement 900g, standard sand 1350g, silica fume 135g, Subote polycarboxylate water reducer (50%wt) 3.6g; the above water-cement ratio and viscosity reducer dosage are shown in Table 1. The Subote polycarboxylate water reducer in the blank example and the mortar added with the viscosity reducer of Examples 1-3 and Comparative Example 4 is PCA water reducer. The Subote polycarboxylate water reducer in Example 4 is Subote naphthalenesulfonate water reducer + aliphatic water reducer (reference 2:1, 40% mass concentration) 3.6g (relative to the amount of glue is 0.2%).

[0051] Table 1 Mortar performance test after adding viscosity reducer in each example

[0052]

[0053] Note: T200 means the time required when the mortar diffusion is 200mm

[0054] Table 1 shows that the viscosity reduction effect will be better when the proportion of diols and their derivatives is high, and the low molecular weight is conducive to the release of bound water between components, which is conducive to the viscosity reduction effect; the comparative example shows that when the molecular weight of the component is too large, the viscosity reduction effect will be lost, and the effect is relatively small when the water-binder ratio is high. The lower the water-binder ratio, the greater the adverse effect on fluidity and inverted cone time. In comparative example 4, due to the long carbon chain, component A has poor water solubility and loses the viscosity reduction effect, and the EO segment of component B is too long, so the air entrainment effect of this component is better, which is not conducive to the later strength of low water-binder ratio concrete.

[0055] Application Example 2

[0056] The viscosity reducers prepared in Example 5 and Example 6 were added to concrete to conduct concrete experiments. The experiment used Onoda cement: 5.6 kg; fly ash: 2.0 kg; large stone: 13.2 kg; small stone: 8.4 kg; sand: 14.8 kg; water-cement ratio was 0.19 / 0.22 respectively; and 18% admixture (15% water reducer + 3% sodium saccharide).

[0057] The viscosity reducer prepared in comparative examples 1-3 was added to concrete to carry out concrete experiments. The experiment used Onoda cement: 5.6 kg; fly ash: 2.0 kg; large stone: 13.2 kg; small stone: 8.4 kg; sand: 14.8 kg; montmorillonite 38 g; water-cement ratio as shown in Table 2; and 18% admixture (15% water reducer + 3% sodium saccharide).

[0058] In the blank concrete experiment, 5.6 kg of Onoda cement, 2.0 kg of fly ash, 13.2 kg of large stone, 8.4 kg of small stone, 14.8 kg of sand were used. The water-cement ratio was 0.19 / 0.22 respectively. 18% admixture (15% water reducing agent + 3% sodium saccharide) was used.

[0059] Table 2 Concrete test

[0060]

[0061] Note: T500 means the time required for the concrete to expand to 500mm

[0062] From the data in Table 2, it can be found that Examples 3, 5, and 6 show that the mortar can be effectively reduced in concrete under the combined conditions, and the viscosity reduction effect is more advantageous when the A component is higher and the molecular weight of the component is smaller. However, in the comparative example, the reduced hydroxyl ratio or excessively large molecular weight is not conducive to the viscosity reduction effect.

[0063] In Comparative Example 1, since monomethyl ether basically makes the product lose half of its viscosity reducing effect, and the amount of glycerol polyoxyethylene ether added is relatively large, the viscosity reducing effect becomes poor after exceeding the optimal amount.

[0064] In Comparative Example 2, the triol derivative of component A loses its viscosity reducing effect due to the loss of viscosity reducing effect of glycerol polyoxyethylene ether trimethyl ether, and the overall viscosity reducing effect becomes poor.

[0065] The non-terminal hydroxyl group compound used in Comparative Example 3 has no viscosity reducing effect in low water-binder ratio concrete due to the lack of the ability of the hydroxyl group to bind water.

Claims

1. A viscosity reducer for concrete, characterized in that: It is prepared by mixing three components A, B and C in a mass ratio of (50-80): (30-20): (0-20); The A component is selected from any one or more small molecule diols and small molecule diol derivatives; the small molecule diol in the A component is selected from any one or more of all straight-chain and branched diols of C3 to C8 and mixed in any proportion; the small molecule diol derivative is selected from any one or more of polyoxyethylene ether derivatives of straight-chain\branched diols and mixed in any proportion; The general formula of the small molecule diol derivative is shown in (II), In the above general formula (II), a1=1-6, b=2-7, R1 is -H, -CH3, -CH2CH3 or -CH(CH3)2; The component B is selected from any one of glycerol and glycerol polyoxyethylene ether derivatives or a mixture of the two in any proportion; the structure of the glycerol polyoxyethylene ether derivative of the component B is shown in the following formula (III), wherein c=2-7; The C component is pentaerythritol polyoxyethylene ether, and its general structural formula is (IV), wherein d=2-7; 2. A concrete viscosity reducer according to claim 1, characterized in that: The small molecule diol is selected from any one or more of diethylene glycol, triethylene glycol, tetraethylene glycol and the monomers shown in the general structural formula (I) and mixed in any proportion. In the above general formula (I), a=1 to 6, and R is -H, -CH3, -CH2CH3 or -CH(CH3)2.

3. The method for applying the viscosity reducer for concrete according to any one of claims 1 to 2, characterized in that: The dosage of the viscosity reducer is 0.2%-4% of the total mass of the gelling material, and the dosage is a pure solid dosage.

4. The method for applying a viscosity reducer for concrete according to claim 3, characterized in that: The dosage of the viscosity reducer is 0.5%-2% of the total gelling material mass.

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