RU2235082C1 - Composition for preparing dispersed-reinforced foam concrete - Google Patents

Abstract

FIELD: building industry.

SUBSTANCE: invention relates to compositions of foam concrete with using dispersed reinforcing with different fibers and can be used for manufacturing articles under stationary conditions and in building platform directly in carrying out monolith heat-insulating works. Composition for preparing dispersed-reinforced foam concrete comprising Portland cement, quartz sand, natural fiber as component for dispersed reinforcing and foaming agent an aqueous solution contains coconut fiber as natural fiber and foaming agent aqueous solution in the concentration 0.3-0.6% in the following ratio of components, mas. p. p.: Portland cement, 100; quartz sand, 10-95; indicated solution of foaming agent, 50-70; coconut fiber, 1-3. Invention provides simplifying technology and enhancing tensile strength limit of foam concrete at bending.

EFFECT: improved and valuable properties of foam concrete.

1 tbl, 1 ex

Description

The invention relates to foam concrete compositions using dispersed reinforcement with various fibers and can be used for the manufacture of products in stationary conditions and directly at the construction site when carrying out monolithic thermal insulation works.

The composition according to the invention is especially effective in the manufacture of wall products in stationary installations for low-rise construction, as well as for monolithic thermal insulation of roofs using mobile units equipped with mortar pumps.

It is known in the method of preparing a foam concrete mixture according to [1] replacing asbestos fiber with kaolin fiber with a diameter of 1-10 microns and a length of 0.1-2 cm, introduced into the aqueous solution of the foaming agent in an amount of 0.18-0.86% by weight of the dry components of the mixture as a foam stabilizer during its whipping and directly into the dry mixture in an amount of 0.55-1.82% of its mass. This ensures a uniform distribution of fibers throughout the volume of the pouring mixture, but does not lead to an increase in tensile strength of foam concrete in bending.

By its technical nature and the achieved effect, the composition according to [2] for the manufacture of dispersively reinforced foam concrete, including Portland cement, silica sand, dispersed reinforcement component — natural fiber and an aqueous foaming solution is closest to this invention.

In the known composition, as a component of dispersed reinforcement, fiber is used from cotton or flax 0.3-1.9 cm long, and also from organic fiber based on polymers (polyethylene, polypropylene, etc.) of the same length with a diameter of 0.02-0, 50 mm with a flow rate of 0.22-2.2% by weight of Portland cement. The technological process involves the preparation of a solution from Portland cement, quartz sand, natural fiber and water, followed by the addition of separately prepared foam, as well as other types of mineral aggregate, such as limestone, basalt, granite, granular (foamed) slag, expanded clay or ash, with a total consumption of small and large fractions of aggregates 1-10 wt.ch. for 1 max. Portland cement.

The main disadvantage of the composition is the low efficiency of reinforcing these fibers. Polymer fibers practically do not adhere to cement stone, requiring the application of adhesives to the fibers, which complicates the technology. Natural fiber from cotton or linen does not have the necessary elasticity for uniform distribution throughout the volume of the material. The relatively low fiber content in the mixture of 0.2-2.2% by weight of Portland cement does not increase the tensile strength of foam concrete in bending.

The aim of the invention is to simplify the technology and increase the tensile strength of foam concrete in bending.

This goal is achieved in that the composition for the manufacture of dispersively reinforced foam concrete, including Portland cement, quartz sand, a component of dispersed reinforcement - natural fiber and an aqueous foaming agent, contains coconut fiber as a natural fiber, and an aqueous foaming agent concentration of 0.3-0.6 % with the following ratio of ingredients, wt.h .: Portland cement 100, silica sand 10-95, the specified foaming solution 50-70, coconut fiber 1-3.

The combination of coconut fiber with sand (preferably quartz with grains of acute angular shape) in these ratios makes it possible to use foam concrete of non-autoclave hardening with an average density in the dry state of 400-900 kg / m ³ and compressive strength when using Portland cement with a grade of at least “400” 0.75-5.15 MPa and tensile strength in bending of 0.08-0.40 MPa after 28 days of hardening under normal conditions (n.u.) at 15-20 ° C.

Coconut fiber, supplied from Vietnam, contains mainly cellulose 45-47 wt.% And lignin 37-39 wt.%, Which determines its high stability in alkaline environments. In addition, the fiber contains xylans 11-13 wt.%, Increasing its biostability, as well as oils 5-6 wt.%.

The fiber has the necessary elasticity for uniform distribution in cement mortar in almost any quantities, has a length of 5-30 cm, a diameter of 0.20-0.25 mm and is characterized by high tensile strength of 80-100 MPa with fiber elongation of 15-20% .

The presence of oils in the fiber causes a delayed capillary suction of water and, accordingly, its low consumption for wetting the surface of the fibers during the preparation of the foam concrete mixture. At the same time, the fiber, immersed in water for a long time, gradually absorbs it, absorbing 120-180 wt.% For 24 hours. Slow internal fiber suction of free water from the molded concrete mixture accelerates its hardening without special additives like CaCl ₂ , and most importantly, does not require special care for hardening concrete. This further simplifies the technology.

When storing natural fiber under normal conditions, the capillary moisture content in it is 15-18 wt.%. The hygroscopicity of the fiber, dried at 60 ° C to constant weight, 5-7 wt.%.

The optimal fiber length for dispersed reinforcement of foam concrete is in the range of 1-10 mm.

In the technical implementation of the invention, the raw fiber, kept to equilibrium humidity indoors at 15-20 ° C, is chopped in a knife mill with a rotating working body and sent to a spare hopper for subsequent dosing to the mixer. The fibrous loose mass after felling contains fibers mainly 3-5 mm long and has a bulk density of 500-600 kg / m ³ . The true fiber density is 1450 kg / m ³ .

Quartz sand must meet the requirements of standards for the production of stucco mortars. The preferred module of the size of the sand M _to = 1,2. The best results are obtained by sand having a residue on a sieve with a hole diameter of 0.63 mm of not more than 5 wt.% With a grain size mainly in the range of 0.1-0.5 mm.

Cement should meet the requirements for Portland cement and its varieties and have a brand name preferably “400” - “500”.

The foam concrete mixture is prepared by any known method using any cement-compatible foaming agent, preferably from a number of cationic surfactants (surfactants), supplied in the form of 30-33% aqueous solutions, such as, for example, “Amine oxide”, “PO -3NP ”,“ Hostapur OSB Neu ”software, etc.

Example. Commodity 30% aqueous solution “PO-3NP” with a density of 1.07 g / cm ^{3 was} mixed with water to obtain a concentration of 0.3-0.6%, which corresponds to the consumption of commodity foaming agent in an amount of 1-2 l per 100 l of water . From the resulting working solution, foam was whipped to a ratio of 4-10, expressed as the ratio of the volume of the foam to the volume of the working solution. The finished foam was sent to a mortar mixer, and with continuous rotation of the working body, fiber, quartz sand and Portland cement were poured into it in a predetermined ratio. The mixer was stopped as soon as the white spots of foam disappeared.

The concentration of the working solution of the foaming agent, its amount per batch and the multiplicity of the foam were selected empirically depending on the given average density of the foam concrete in the dry state.

The resulting foam concrete mixture was poured into molds. The poured molds were kept until formwork strength, samples were taken from the molds and stored under normal conditions at 15–20 ° C.

The tests were carried out after 28 days of hardening in NU Before testing, the samples were dried at 95-105 ° C to constant weight. Their average density, compressive strength, and tensile strength in bending were determined.

The compositions of the prototypes and their characteristics are given in the table.

The table shows that as the average density of foam concrete decreases, the amount of quartz sand decreases, the amount of fiber increases, the concentration of the working solution of the foaming agent and its amount increase. However, an increase in the concentration of the working solution of the foaming agent up to 0.65%, its amount up to 70 wt.ch. and fiber content up to 3.4 wt.h. while reducing the amount of sand to 5 wt.h. at 100 max. Portland cement does not lead to an increase in both compressive and tensile strength when bending foam concrete of the same average density. An increase in the content of quartz sand to 115% while reducing the amount of fiber to 0.5% by weight of Portland cement leads to an increase in the average density of foam concrete to 1100 kg / m ³ , which is not economical.

Literature:

1. A.S. USSR No. 783291, C 04 V 43/02, 02/20/1979 - analogue.

2. GB patent No. 1285701, C 04 V 21/10, 08.16.1972 - prototype.

Claims (1)

Composition for the manufacture of dispersed reinforced foam concrete, including Portland cement, quartz sand, a component of dispersed reinforcement - natural fiber and an aqueous foaming agent, characterized in that it contains coconut fiber as a natural fiber, and an aqueous foaming agent concentration of 0.3 - 0.6% in the following ratio of ingredients, parts by weight: Portland cement 100 Quartz sand 10 - 95 The specified foaming agent solution 50 - 70 Coconut Fiber 1 - 3