Preparation method and application of lightweight concrete

Abstract

The present invention discloses a preparation method and application of lightweight concrete, relating to the field of concrete technology. The invention discloses a lightweight concrete comprising the following components: cement, fly ash, standard sand, a water reducer, a foaming agent, modified pineapple leaf fiber, modified polyvinyl alcohol fiber, a nonionic surfactant, an anionic surfactant, and water. The preparation method of the modified pineapple leaf fiber comprises the following steps: alkali-treating and benzoyl-modifying the pineapple leaf fiber; and the preparation method of the modified polyvinyl alcohol fiber comprises the following steps: coating the polyvinyl alcohol fiber with polyvinyl acetate. The lightweight concrete exhibits excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a preparation method and application of lightweight concrete. Background Art

[0002] Lightweight concrete includes lightweight foam concrete and lightweight aggregate concrete. Lightweight foam concrete is a porous, lightweight material composed of a matrix, aggregate, and pores. It has the advantages of being lightweight, thermally insulating, seismically resistant, durable, and highly fluid. It is widely used in building components such as basements, insulation boards, walls, partitions, floor slabs, and roofs. However, lightweight foam concrete has poor mechanical properties due to the presence of a large number of pores. Modern civil engineering continuously places new demands on the quality and mechanical properties of structural components, which in turn places higher demands on the performance of lightweight concrete. There is an urgent need to provide a lightweight concrete with excellent mechanical properties. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a lightweight concrete with good mechanical properties and durability.

[0004] The present invention also provides a method for preparing the lightweight concrete.

[0005] The present invention also provides applications of the lightweight concrete or the concrete prepared by the preparation method.

[0006] A lightweight concrete according to a first embodiment of the present invention includes the following components:

[0007] Cement, fly ash, standard sand, water reducing agent, foaming agent, modified pineapple leaf fiber, modified polyvinyl alcohol fiber, nonionic surfactant, anionic surfactant and water;

[0008] The preparation method of the modified pineapple leaf fiber comprises the following steps:

[0009] Pineapple leaf fiber was modified by alkali treatment and benzoylation;

[0010] The preparation method of the modified polyvinyl alcohol fiber comprises the following steps:

[0011] The surface of the polyvinyl alcohol fiber is coated with polyvinyl acetate.

[0012] The lightweight concrete according to the embodiment of the present invention has at least the following beneficial effects:

[0013] The lightweight concrete of the embodiment has excellent mechanical properties and durability, and has good application prospects in the fields of construction and other aspects. By alkali-treating pineapple leaf fiber, substances such as hemicellulose, pectin, and wax are removed, the adhesion between the pineapple leaf fiber and the gel material is improved, and the hydroxyl group can be activated, which helps to promote the reaction between benzoyl chloride and the pineapple leaf fiber. Benzoyl-modified pineapple leaf fiber further reduces the hydrophilicity of the pineapple leaf fiber, slows down the hydration reaction speed of the gel material, and improves the mechanical properties of the lightweight concrete. By coating a layer of less acidic polyvinyl acetate on the surface of the polyvinyl alcohol fiber, the hydration of the gel material can be inhibited, the interfacial strength can be reduced, the amplitude of the increase in internal stress caused by the long service life of the lightweight concrete can be reduced, and the service durability of the lightweight concrete can be improved.

[0014] Modified pineapple leaf fiber and modified polyvinyl alcohol fiber can reduce the fluidity of cement slurry, resulting in a relatively low drainage rate, and can form a certain three-dimensional structure with each other, adsorb on the gel material and bubble surface, thereby improving bubble stability and significantly improving the mechanical properties of lightweight concrete; combined with the coordination between non-ionic surfactants and anionic surfactants, it can effectively improve the dispersibility of modified pineapple leaf fiber and modified polyvinyl alcohol fiber, reduce the surface tension of bubbles, enhance the stability of bubbles, and thus enhance the mechanical properties of lightweight concrete.

[0015] According to some embodiments of the present invention, the lightweight concrete comprises, by weight:

[0016] 80 to 110 parts of cement, 10 to 17 parts of fly ash, 5 to 15 parts of standard sand, 0.1 to 1 part of water reducer, 0.5 to 1.5 parts of foaming agent, 2 to 4 parts of modified pineapple leaf fiber, 1 to 3 parts of modified polyvinyl alcohol fiber, 1 to 3 parts of nonionic surfactant, 0.5 to 2 parts of anionic surfactant and 30 to 50 parts of water.

[0017] According to some embodiments of the present invention, the lightweight concrete comprises, by weight:

[0018] 90 to 100 parts of cement, 12 to 15 parts of fly ash, 8 to 10 parts of standard sand, 0.3 to 0.5 parts of water reducer, 0.7 to 1 part of foaming agent, 2.5 to 3 parts of modified pineapple leaf fiber, 1.5 to 2 parts of modified polyvinyl alcohol fiber, 1.5 to 2 parts of nonionic surfactant, 0.9 to 1.5 parts of anionic surfactant and 35 to 45 parts of water.

[0019] According to some embodiments of the invention, the cement comprises Portland cement.

[0020] According to some embodiments of the present invention, the strength grade of the silicate cement is not less than P.O.42.5.

[0021] The term "not less than" means greater than or equal to and should be understood to include the number itself.

[0022] According to some embodiments of the present invention, the method for preparing the modified pineapple leaf fiber may include the following steps:

[0023] Alkali treatment, first water washing, benzoylation modification, second water washing, alcohol washing, and drying.

[0024] According to some embodiments of the present invention, the method for performing the alkali treatment comprises the following steps:

[0025] Soak the pineapple leaf fibers in an alkaline aqueous solution.

[0026] According to some embodiments of the present invention, the length of the pineapple leaf fiber is 5 mm to 7 mm, for example, 5 mm, 5.2 mm, 5.4 mm, 5.6 mm, 5.8 mm, 6 mm, 6.2 mm, 6.4 mm, 6.6 mm, 6.8 mm, or 7 mm.

[0027] According to some embodiments of the present invention, the diameter of the pineapple leaf fiber is 35 μm to 45 μm, for example, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm or 45 μm.

[0028] According to some embodiments of the present invention, the alkaline aqueous solution contains 12 wt % to 17 wt % of a strong base, for example, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt % or 17 wt %.

[0029] According to some embodiments of the present invention, the mass volume ratio of the pineapple leaf fiber to the alkaline aqueous solution is 1 g:40 mL to 60 mL. For example, it can be 1 g:40 mL, 1 g:45 mL, 1 g:50 mL, 1 g:55 mL, or 1 g:60 mL.

[0030] According to some embodiments of the present invention, the strong base comprises an alkali metal hydroxide, and the alkali metal hydroxide comprises at least one of NaOH and KOH.

[0031] According to some embodiments of the present invention, the soaking time is 10 min to 30 min, for example, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, or 30 min.

[0032] According to some embodiments of the present invention, the method for performing the benzoylation modification comprises the following steps:

[0033] In the presence of an alkaline catalyst, the pineapple leaf fiber treated with alkali is reacted with benzoyl chloride to obtain the modified pineapple leaf fiber.

[0034] According to some embodiments of the present invention, the alkaline catalyst includes at least one of pyridine, triethylamine, and sodium carbonate.

[0035] According to some embodiments of the present invention, when the alkaline catalyst is pyridine, the amount of pyridine added is 5 (v / v)% to 15 (v / v)%. For example, it can be 5 (v / v)%, 6 (v / v)%, 7 (v / v)%, 8 (v / v)%, 9 (v / v)%, 10 (v / v)%, 11 (v / v)%, 12 (v / v)%, 13 (v / v)%, 14 (v / v)%, or 15 (v / v)%.

[0036] According to some embodiments of the present invention, the mass ratio of the benzoyl chloride to the pineapple leaf fiber is 1:0.4-0.6, for example, 1:0.4, 1:0.42, 1:0.44, 1:0.46, 1:0.48, 1:0.5, 1:0.52, 1:0.54, 1:0.56, 1:0.58, or 1:0.6.

[0037] According to some embodiments of the present invention, the reaction time with the benzoyl chloride is 1 h to 3 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, or 3 h.

[0038] According to some embodiments of the present invention, the temperature for reacting with the benzoyl chloride is 35° C. to 45° C. For example, it may be 35° C., 36° C., 37° C., 38° C., 39° C., 40° C., 41° C., 42° C., 43° C., 44° C., or 45° C.

[0039] According to some embodiments of the present invention, the solvent used in the benzoylation modification includes acetone, dichloromethane, dichloroethane or dimethylformamide.

[0040] According to some embodiments of the present invention, the alcohol washing comprises washing with anhydrous ethanol.

[0041] According to some embodiments of the present invention, the drying temperature is 60°C to 80°C. For example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C.

[0042] According to some embodiments of the present invention, the method for preparing the modified polyvinyl alcohol fiber may include the following steps:

[0043] The modified polyvinyl alcohol fiber is obtained by placing the polyvinyl alcohol fiber in a polyvinyl acetate emulsion, performing ultrasonic treatment, and baking.

[0044] According to some embodiments of the present invention, the mass ratio of the polyvinyl alcohol fiber to the polyvinyl acetate in the polyvinyl acetate emulsion is 1:9-12. For example, it can be 1:9, 1:10, 1:11 or 1:12.

[0045] According to some embodiments of the present invention, the method for preparing the modified polyvinyl alcohol fiber further includes solvent water.

[0046] According to some embodiments of the present invention, during the ultrasonic treatment, the mass volume ratio of the polyvinyl alcohol fiber to the solution is 1 g:90 mL to 110 mL, for example, 1 g:90 mL, 1 g:95 mL, 1 g:100 mL, 1 g:105 mL, or 1 g:110 mL.

[0047] According to some embodiments of the present invention, the length of the polyvinyl alcohol fiber is 7 mm to 9 mm, for example, 7 mm, 7.5 mm, 8 mm, 8.5 mm or 9 mm.

[0048] According to some embodiments of the present invention, the diameter of the polyvinyl alcohol fiber is 25 μm to 35 μm, for example, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm or 35 μm.

[0049] According to some embodiments of the present invention, the pH of the polyvinyl acetate emulsion is 4 to 5. For example, it can be 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.

[0050] According to some embodiments of the present invention, the solid content of the polyvinyl acetate emulsion is 10-11 g / 100 mL, for example, 10 g / 100 mL, 10.1 g / 100 mL, 10.2 g / 100 mL, 10.3 g / 100 mL, 10.4 g / 100 mL, 10.5 g / 100 mL, 10.6 g / 100 mL, 10.7 g / 100 mL, 10.8 g / 100 mL, 10.9 g / 100 mL, or 11 g / 100 mL.

[0051] According to some embodiments of the present invention, the ultrasonic power of the ultrasonic treatment is 40 kW to 60 kW, for example, 40 kW, 42 kW, 44 kW, 46 kW, 48 kW, 50 kW, 52 kW, 54 kW, 56 kW, 58 kW, or 60 kW.

[0052] According to some embodiments of the present invention, the ultrasonic treatment time is 10 min to 20 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min.

[0053] According to some embodiments of the present invention, the baking temperature is 35° C. to 45° C. For example, it may be 35° C., 36° C., 37° C., 38° C., 39° C., 40° C., 41° C., 42° C., 43° C., 44° C., or 45° C.

[0054] According to some embodiments of the present invention, the baking time is 3 h to 5 h, for example, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, 4 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h or 5 h.

[0055] According to some embodiments of the present invention, the method for preparing the modified polyvinyl alcohol fiber further includes a third water washing treatment after baking.

[0056] According to some embodiments of the present invention, the water reducer includes a polycarboxylate water reducer.

[0057] According to some embodiments of the present invention, the nonionic surfactant includes a polyoxyethylene nonionic surfactant.

[0058] According to some embodiments of the present invention, the polyoxyethylene nonionic surfactant includes at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

[0059] According to some embodiments of the present invention, the anionic surfactant includes a sulfonate-type anionic surfactant.

[0060] According to some embodiments of the present invention, the sulfonate type anionic surfactant includes at least one of sodium dodecylbenzenesulfonate, sodium diisooctyl sulfosuccinate, sodium dibutylnaphthalenesulfonate, and sodium heavy alkylbenzenesulfonate.

[0061] According to some embodiments of the present invention, the foaming agent includes a HTW-I type composite foaming agent.

[0062] The method for preparing the lightweight concrete according to the second embodiment of the present invention comprises the following steps:

[0063] S1. Mixing a water reducer with water to obtain a mixture A;

[0064] S2. Add cement, fly ash and standard sand to the mixture A and mix to obtain a mixture B;

[0065] S3, adding a foaming agent to the mixture B, and mixing to obtain a mixture C;

[0066] S4, add modified pineapple leaf fiber, modified polyvinyl alcohol fiber, nonionic surfactant and anionic surfactant in described mixture C, obtain cement slurry; Cast, demoulding and curing are carried out successively, obtain lightweight concrete.

[0067] The application of the above-mentioned lightweight concrete or the lightweight concrete prepared by the above-mentioned preparation method in the field of construction according to the third aspect of the present invention.

[0068] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0069] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0070] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0071] In the description of the present invention, if there are descriptions of first, second, third, etc., they are only used to distinguish technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0072] In the description of the present invention, the terms "comprises" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product or apparatus.

[0073] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0074] As used herein, the terms "comprises," "including," "having," "containing" or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a listed element is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0075] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0076] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. For example, if we say that the parts by mass of component A are a parts and the parts by mass of component B are b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0077] Unless otherwise specified, “about” in the present invention means that the allowable error is within ±5%.

[0078] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0079] In the examples of the present application, unless otherwise specified, P·O42.5 ordinary Portland cement was purchased from Hunan Yiyang Conch Cement Co., Ltd.;

[0080] Fly ash, first-grade fly ash, was purchased from Jining Hengzhi New Building Materials Co., Ltd.;

[0081] Standard sand was purchased from Xiamen Aisiou Standard Sand Co., Ltd.

[0082] The polycarboxylate superplasticizer was Point-TS1 polycarboxylate superplasticizer purchased from Fujian Kezhijie New Materials Co., Ltd.

[0083] The foaming agent was HTW-I type composite foaming agent purchased from Henan Huatai Building Materials Development Co., Ltd.

[0084] Polyvinyl acetate emulsion, brand 8482, was purchased from Celanese Corporation, with a solid content of 53%.

[0085] The preparation method of modified pineapple leaf fiber is as follows:

[0086] 10 g of pineapple leaf fiber (about 6 mm long, average diameter about 40 μm) was soaked in 50 mL of 15wt% NaOH aqueous solution for 20 min. After washing with clean water, the fiber was placed in 60 mL of acetone solution containing 5 g of benzoyl chloride and 6 mL of pyridine at 40°C for 2 h. The fiber was washed with clean water and then soaked in anhydrous ethanol for 1 h to remove unreacted benzoyl chloride. The fiber was further washed with clean water and dried at 70°C to obtain modified pineapple leaf fiber.

[0087] The preparation method of modified polyvinyl alcohol fiber is as follows:

[0088] 20 g of polyvinyl acetate emulsion was diluted to 100 mL with deionized water, and 1 g of polyvinyl alcohol fiber (about 8 mm in length and 31 μm in average diameter) was immersed in the diluted polyvinyl acetate emulsion. The fiber was stirred and treated with ultrasound (50 kW) for 15 min. The polyvinyl alcohol fiber was taken out and baked at 40 °C for 4 h. The fiber was then washed with clean water to obtain the modified polyvinyl alcohol fiber.

[0089] Example 1

[0090] This example provides a lightweight concrete, the raw material composition of which is as follows by weight:

[0091] PO42.5 ordinary Portland cement 100 parts;

[0092] 15 parts of fly ash;

[0093] 10 parts of standard sand;

[0094] 0.5 parts of polycarboxylate water reducer;

[0095] 1 part foaming agent;

[0096] 3 parts modified pineapple leaf fiber;

[0097] 2 parts of modified polyvinyl alcohol fiber;

[0098] 2 parts of fatty alcohol polyoxyethylene ether;

[0099] 1.5 parts of sodium dodecylbenzenesulfonate;

[0100] 45 parts water.

[0101] This example also provides a method for preparing the lightweight concrete, and the steps are as follows:

[0102] S1, mixing the polycarboxylate water reducer with water and stirring uniformly to obtain a mixture A;

[0103] S2. Add PO42.5 ordinary Portland cement, fly ash, and standard sand to mixture A and continue stirring to obtain mixture B;

[0104] S3, adding a foaming agent to mixture B, and continuing stirring for 2 minutes to obtain mixture C;

[0105] S4. Add modified pineapple leaf fiber, modified polyvinyl alcohol fiber, fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate to mixture C, stir thoroughly to obtain cement slurry; pour, demould and cure in sequence to obtain lightweight concrete.

[0106] Example 2

[0107] This example provides a lightweight concrete, the raw material composition of which is as follows by weight:

[0108] PO42.5 Ordinary Portland Cement 90 parts;

[0109] 12 parts of fly ash;

[0110] 8 parts of standard sand;

[0111] 0.3 parts of polycarboxylate water reducer;

[0112] 0.7 parts of foaming agent;

[0113] 2.5 parts of modified pineapple leaf fiber;

[0114] 1.5 parts of modified polyvinyl alcohol fiber;

[0115] 1.5 parts of alkylphenol polyoxyethylene ether;

[0116] 0.9 parts of sodium dibutylnaphthalenesulfonate;

[0117] 35 parts water.

[0118] This example also provides a method for preparing the lightweight concrete, and the steps are as follows:

[0119] S1, mixing the polycarboxylate water reducer with water and stirring uniformly to obtain a mixture A;

[0120] S2. Add PO42.5 ordinary Portland cement, fly ash, and standard sand to mixture A and continue stirring to obtain mixture B;

[0121] S3, adding a foaming agent to mixture B, and continuing stirring for 2 minutes to obtain mixture C;

[0122] S4. Add modified pineapple leaf fiber, modified polyvinyl alcohol fiber, alkylphenol polyoxyethylene ether and sodium dibutylnaphthalene sulfonate to mixture C, stir thoroughly to obtain cement slurry; pour, demould and cure in sequence to obtain lightweight concrete.

[0123] Comparative Example 1

[0124] This example provides a lightweight concrete, the raw material composition of which is as follows by weight:

[0125] PO42.5 ordinary Portland cement 100 parts;

[0126] 15 parts of fly ash;

[0127] 10 parts of standard sand;

[0128] 0.5 parts of polycarboxylate water reducer;

[0129] 1 part foaming agent;

[0130] 3 parts of alkali-treated pineapple leaf fiber;

[0131] 2 parts of modified polyvinyl alcohol fiber;

[0132] 2 parts of fatty alcohol polyoxyethylene ether;

[0133] 1.5 parts of sodium dodecylbenzenesulfonate;

[0134] 45 parts water.

[0135] Wherein, the preparation method of alkali-treated pineapple leaf fiber is as follows:

[0136] Pineapple leaf fibers (about 6 mm in length and 40 μm in average diameter) were soaked in a 20% NaOH aqueous solution for 20 min, washed with clean water, and dried at 70°C to obtain alkali-treated pineapple leaf fibers.

[0137] This example also provides a method for preparing the lightweight concrete, and the steps are as follows:

[0138] S1, mixing the polycarboxylate water reducer with water and stirring uniformly to obtain a mixture A;

[0139] S2. Add PO42.5 ordinary Portland cement, fly ash, and standard sand to mixture A and continue stirring to obtain mixture B;

[0140] S3, adding a foaming agent to mixture B, and continuing stirring for 2 minutes to obtain mixture C;

[0141] S4. Add modified pineapple leaf fiber, modified polyvinyl alcohol fiber, fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate to mixture C, stir thoroughly to obtain cement slurry; pour, demould and cure in sequence to obtain lightweight concrete.

[0142] Comparative Example 2

[0143] This example provides a lightweight concrete, the raw material composition of which is as follows by weight:

[0144] PO42.5 ordinary Portland cement 100 parts;

[0145] 15 parts of fly ash;

[0146] 10 parts of standard sand;

[0147] 0.5 parts of polycarboxylate water reducer;

[0148] 1 part foaming agent;

[0149] 3 parts modified pineapple leaf fiber;

[0150] 2 parts of polyvinyl alcohol fiber;

[0151] 2 parts of fatty alcohol polyoxyethylene ether;

[0152] 1.5 parts of sodium dodecylbenzenesulfonate;

[0153] 45 parts water.

[0154] This example also provides a method for preparing the lightweight concrete, and the steps are as follows:

[0155] S1, mixing the polycarboxylate water reducer with water and stirring uniformly to obtain a mixture A;

[0156] S2. Add PO42.5 ordinary Portland cement, fly ash, and standard sand to mixture A and continue stirring to obtain mixture B;

[0157] S3, adding a foaming agent to mixture B, and continuing stirring for 2 minutes to obtain mixture C;

[0158] S4. Add modified pineapple leaf fiber, polyvinyl alcohol fiber, fatty alcohol polyoxyethylene ether and sodium dodecylbenzene sulfonate to mixture C, stir thoroughly to obtain cement slurry; pour, demould and cure in sequence to obtain lightweight concrete.

[0159] Comparative Example 3

[0160] This example provides a lightweight concrete, the raw material composition of which is as follows by weight:

[0161] PO42.5 ordinary Portland cement 100 parts;

[0162] 15 parts of fly ash;

[0163] 10 parts of standard sand;

[0164] 0.5 parts of polycarboxylate water reducer;

[0165] 1 part foaming agent;

[0166] 3 parts modified pineapple leaf fiber;

[0167] 2 parts of modified polyvinyl alcohol fiber;

[0168] 1.5 parts of sodium dodecylbenzenesulfonate;

[0169] 45 parts water.

[0170] This example also provides a method for preparing the lightweight concrete, and the steps are as follows:

[0171] S1, mixing the polycarboxylate water reducer with water and stirring uniformly to obtain a mixture A;

[0172] S2. Add PO42.5 ordinary Portland cement, fly ash, and standard sand to mixture A and continue stirring to obtain mixture B;

[0173] S3, adding a foaming agent to mixture B, and continuing stirring for 2 minutes to obtain mixture C;

[0174] S4. Add modified pineapple leaf fiber, modified polyvinyl alcohol fiber and sodium dodecylbenzene sulfonate to mixture C, stir thoroughly to obtain cement slurry; pour, demould and cure in sequence to obtain lightweight concrete.

[0175] Test example

[0176] 1. The compressive strength of the lightweight concrete (100 mm × 100 mm × 100 mm) of Examples 1-2 and Comparative Examples 1-3 was tested in a standard curing room after curing for 7 days and 28 days, respectively, according to the test method in JG / T 266-2011 "Foamed Concrete".

[0177] The test results are shown in Table 1.

[0178] Table 1

[0179]

[0180] 2. The crack resistance of the lightweight concrete of Examples 1 and 2 and Comparative Examples 1 and 2 was tested with reference to JC / T 951-2005 "Test Method for Crack Resistance of Cement Mortar". The specific method is as follows:

[0181] The test was conducted in a laboratory at 20 ± 1°C and a relative humidity of (43 ± 2%). Cement slurry was poured into the formwork and smoothed. A fan (located 150 mm from the short side of the mold, with the center of the blade parallel to the specimen surface, and an average wind speed of 5 m / s) was immediately turned on to blow air onto the specimen surface. An iodine-tungsten lamp (1000 W, located 1.2 m above the specimen's transverse centerline and 150 mm from the mold's long side) was also turned on. The fan was turned off after 3 days, and the lamp was turned off after 4 hours. The specimens were cured in the laboratory for 360 days, and the time to initial cracking (cracking age) was recorded.

[0182] The test results are shown in Table 2.

[0183] Table 2

[0184]

[0185] In summary, it can be seen that the lightweight concrete of Examples 1 and 2 has good compressive strength and crack resistance.

[0186] Compared to Example 1, the modified pineapple leaf fiber in the lightweight concrete of Comparative Example 1 exhibited weakened compressive and crack resistance after being benzoylated. This may be because the benzoylation modification reduced the water absorption of the plant fiber, slowed the hydration reaction of the gel material, improved the interaction between the pineapple leaf fiber and the gel material, and reduced concentrated stress, thereby improving the compressive and crack resistance.

[0187] Compared to Example 1, the lightweight concrete in Comparative Example 2, in which the modified polyvinyl alcohol fibers were replaced with polyvinyl alcohol fibers, exhibited weakened compressive and crack resistance. This may be due to the lack of polyvinyl acetate coating on the polyvinyl alcohol fibers, which prevented the hydration reaction of the gel material from being effectively suppressed, leading to weakened compressive and crack resistance.

[0188] Compared with Example 1, the lightweight concrete of Comparative Example 3 lacks fatty alcohol polyoxyethylene ether, and its compressive strength becomes poor.

[0189] The embodiments of the present invention are described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A lightweight concrete, characterized in that: Includes the following components: Cement, fly ash, standard sand, water reducing agent, foaming agent, modified pineapple leaf fiber, modified polyvinyl alcohol fiber, nonionic surfactant, anionic surfactant and water; The preparation method of the modified pineapple leaf fiber comprises the following steps: Pineapple leaf fiber was modified by alkali treatment and benzoylation; The preparation method of the modified polyvinyl alcohol fiber comprises the following steps: The surface of the polyvinyl alcohol fiber is coated with polyvinyl acetate.

2. The lightweight concrete according to claim 1, characterized in that The lightweight concrete comprises, by weight: 80 to 110 parts of cement, 10 to 17 parts of fly ash, 5 to 15 parts of standard sand, 0.1 to 1 part of water reducer, 0.5 to 1.5 parts of foaming agent, 2 to 4 parts of modified pineapple leaf fiber, 1 to 3 parts of modified polyvinyl alcohol fiber, 1 to 3 parts of nonionic surfactant, 0.5 to 2 parts of anionic surfactant and 30 to 50 parts of water.

3. The lightweight concrete according to claim 1, characterized in that The lightweight concrete comprises, by weight: 90 to 100 parts of cement, 12 to 15 parts of fly ash, 8 to 10 parts of standard sand, 0.3 to 0.5 parts of water reducer, 0.7 to 1 part of foaming agent, 2.5 to 3 parts of modified pineapple leaf fiber, 1.5 to 2 parts of modified polyvinyl alcohol fiber, 1.5 to 2 parts of nonionic surfactant, 0.9 to 1.5 parts of anionic surfactant and 35 to 45 parts of water.

4. The lightweight concrete according to claim 1, characterized in that The method for carrying out the alkali treatment comprises the following steps: soaking pineapple leaf fibers in an alkaline aqueous solution; And / or, the method for performing the benzoylation modification comprises the following steps: In the presence of an alkaline catalyst, the pineapple leaf fiber treated with alkali is reacted with benzoyl chloride to obtain the modified pineapple leaf fiber.

5. The lightweight concrete according to claim 4, characterized in that The alkaline aqueous solution contains 12 wt% to 17 wt% of a strong base; the strong base includes at least one of NaOH and KOH; And / or, the soaking time is 10 min to 30 min.

6. The lightweight concrete according to claim 4, characterized in that The alkaline catalyst includes at least one of pyridine and triethylamine; And / or, the mass ratio of the benzoyl chloride to the pineapple leaf fiber is 1:0.4-0.6; and / or, the reaction time with the benzoyl chloride is 1 h to 3 h; And / or, the temperature for reacting with the benzoyl chloride is 35° C. to 45° C.

7. The lightweight concrete according to claim 1, characterized in that The preparation method of the modified polyvinyl alcohol fiber comprises the following steps: The modified polyvinyl alcohol fiber is obtained by placing the polyvinyl alcohol fiber in a polyvinyl acetate emulsion, performing ultrasonic treatment, and baking.

8. The lightweight concrete according to claim 7, characterized in that The solid content of the polyvinyl acetate emulsion is 10-11 g / 100 mL.

9. The lightweight concrete according to claim 7, characterized in that: The pH of the polyvinyl acetate emulsion is 4-5.

10. The lightweight concrete according to claim 7, characterized in that: The mass ratio of the polyvinyl alcohol fiber to the polyvinyl acetate in the polyvinyl acetate emulsion is 1:9-12.

11. The lightweight concrete according to claim 1, characterized in that: The nonionic surfactant includes a polyoxyethylene nonionic surfactant; And / or, the anionic surfactant includes a sulfonate type anionic surfactant.

12. The lightweight concrete according to claim 11, characterized in that: The polyoxyethylene nonionic surfactant includes at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether; And / or, the sulfonate type anionic surfactant includes at least one of sodium dodecylbenzenesulfonate, sodium diisooctyl sulfosuccinate, sodium dibutylnaphthalenesulfonate, and sodium heavy alkylbenzenesulfonate.

13. The method for preparing lightweight concrete according to any one of claims 1 to 12, characterized in that: The following steps are involved: S1. Mixing a water reducer with water to obtain a mixture A; S2. Add cement, fly ash and standard sand to the mixture A and mix to obtain a mixture B; S3, adding a foaming agent to the mixture B, and mixing to obtain a mixture C; S4, add modified pineapple leaf fiber, modified polyvinyl alcohol fiber, nonionic surfactant and anionic surfactant in described mixture C, obtain cement slurry; Cast, demoulding and curing are carried out successively, obtain lightweight concrete.

14. Use of the lightweight concrete according to any one of claims 1 to 12 or the lightweight concrete prepared by the preparation method according to claim 13 in the field of construction.

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