CN107417204B

CN107417204B - Tailing sand fiber concrete capable of being printed in 3D mode and preparation and application methods thereof

Info

Publication number: CN107417204B
Application number: CN201710512635.3A
Authority: CN
Inventors: 马国伟; 王里; 李之建
Original assignee: Hebei University of Technology
Current assignee: Hebei University of Technology
Priority date: 2017-06-29
Filing date: 2017-06-29
Publication date: 2020-04-28
Anticipated expiration: 2037-06-29
Also published as: CN107417204A

Abstract

The invention relates to tailing sand fiber concrete capable of being printed in a 3D mode and a preparation method and a use method thereof, wherein the composition and the content of the concrete are as follows in parts by weight: 6.8-7.2 parts of quick-hardening ordinary portland cement; 1.35-1.45 parts of fly ash; 0.75-0.85 part of silica fume; 0.75-0.85 part of hollow glass beads; 7.1-7.3 parts of sand; 4.7-4.9 parts of tailing sand, wherein the average particle size of the tailing sand is 220-270 mu m; 2.6-2.8 parts of water; 0.045-0.055 part of water reducing agent; 0.005-0.007 part of polypropylene fiber with the length of 7-10 mm; 0.005-0.007 part of basalt fiber with the length of 11-14 mm; 0.04 to 0.06 portion of hydroxypropyl methyl cellulose with the viscosity of 2 to 7 ten thousand. The concrete material utilizes the tailing sand as partial sand to prepare the concrete, has high printable performance, high strength and low cost, and is favorable for promoting the practical engineering application of 3D printed concrete.

Description

Tailing sand fiber concrete capable of being printed in 3D mode and preparation and application methods thereof

Technical Field

The invention relates to the technical field of concrete, in particular to tailing sand fiber concrete capable of being printed in a 3D mode and a preparation method and a use method thereof.

Background

The 3D printing technology has been remarkably developed in the civil engineering and construction field in recent years, and examples of 3D printing bridges, 3D printing houses and the like are frequently reported, which largely confirm the feasibility of applying the 3D printing technology to the civil engineering and construction field. The 3D printing concrete technology is also widely concerned and popularized due to the advantages of free design, flexible construction, high construction speed, low labor cost, high automation degree, small environmental pollution and the like.

However, there are currently few reports on the types of concrete materials that can be 3D printed, and the use of 3D printed concrete materials needs to be coordinated with the operating parameters of the 3D printer. The printable performance of concrete mixtures (e.g., flow, extrudability, build-up, early stiffness, etc.) is also complementary to the printing parameters of the printer (e.g., extrusion speed, printing height, print head design size, etc.). On the premise of reasonably and optimally designing the printable performance of the concrete material and the printing parameters of the printer, the smooth completion of the printing process can be ensured.

The 3D printed concrete has the advantages of reducing labor cost, material cost, mechanical transportation cost and the like, for example, the chinese patent with application No. 201610947297.1 discloses a concrete for 3D printing, the chinese patent with application No. 201510375110.0 discloses a high-performance powder concrete for 3D printing, and the chinese patent with application No. 201510228281.0 discloses a concrete material for 3D printing and a preparation method thereof, and the concrete material does not relate to preparation of materials by using waste solid materials.

Disclosure of Invention

The invention aims to provide tailing sand fiber concrete capable of being printed in a 3D mode and a preparation method and a using method thereof. The concrete material utilizes the tailing sand as partial sand to prepare the concrete, has high printable performance, high strength and low cost, and is favorable for promoting the practical engineering application of 3D printed concrete. According to the preparation method, the raw materials are added in two times, and each time, the raw materials containing powder, fine sand and fiber are added, so that the raw materials are uniformly mixed. And then, adding water and additives twice, so that the phenomena of concrete agglomeration and pilling are reduced, the workability of the concrete is improved, and the tailing sand fiber concrete which can be used for an extrusion type 3D printer in civil engineering and building engineering is obtained. The prepared concrete is printed within the range of various parameters limited by the using method, so that the smoothness of the printing process and the structural stability of the 3D printed concrete can be ensured.

The purpose of the invention is realized by the following technical scheme:

the tailing sand fiber concrete capable of being printed in a 3D mode comprises the following components in parts by weight:

6.8-7.2 parts of quick-hardening ordinary portland cement;

1.35-1.45 parts of fly ash;

0.75-0.85 part of silica fume;

0.75-0.85 part of hollow glass beads;

7.1-7.3 parts of sand;

4.7-4.9 parts of tailing sand, wherein the average particle size of the tailing sand is 220-270 mu m;

2.6-2.8 parts of water;

0.045-0.055 part of water reducing agent;

0.005-0.007 part of polypropylene fiber with the length of 7-10 mm;

0.005-0.007 part of basalt fiber with the length of 11-14 mm;

0.04 to 0.06 portion of hydroxypropyl methyl cellulose with the viscosity of 2 to 7 ten thousand.

A preparation method of the tailing sand fiber concrete capable of being printed in 3D comprises the following steps:

(1) the raw materials are divided into four groups according to the parts by weight, wherein the first group comprises 6.8-7.2 parts of rapid-hardening ordinary portland cement, 1.35-1.45 parts of fly ash, 7.1-7.3 parts of natural sand and 0.005-0.007 part of polypropylene fiber, the second group comprises 0.75-0.85 part of silica fume, 0.75-0.85 part of hollow glass microsphere, 4.7-4.9 parts of tailing sand and 0.005-0.007 part of basalt fiber, the third group comprises 1.3-1.4 parts of water and 0.04-0.06 part of water reducing agent, and the fourth group comprises the balance of water and 0.045-0.065 part of hydroxypropyl methyl cellulose;

(2) simultaneously sending the raw materials of the first group or the second group into a horizontal mixer for mixing and stirring until the raw materials are completely and uniformly mixed, and then correspondingly adding the raw materials of the second group or the first group into the uniformly mixed mixture for mixing and stirring until the raw materials are completely and uniformly mixed;

(3) and (3) respectively and uniformly mixing the raw materials of the third group and the fourth group, then respectively adding the mixed materials into the final mixture obtained in the step (2), and respectively stirring for 90-180s to obtain the concrete.

A use method of the tailing sand fiber concrete capable of being printed in 3D is as follows: pumping or mechanically conveying the concrete into a printing spray head of a 3D printer, standing for 30-40min, and setting the cross section area of an outlet of the printing spray head to be 180-200 mm²The extrusion speed is 0.3-0.4m³And h, the horizontal printing speed is 250-290m/h, and then printing is carried out.

Compared with the existing 3D printing concrete material, the invention has the beneficial effects that:

1) the damage to the environment and ecology caused by using natural gravels is reduced to a great extent, the maintenance and management cost of the tailing sands is reduced, and the price of a 3D printing concrete material is reduced;

2) the polypropylene and the basalt fiber are mixed and doped, so that on one hand, the phenomena of shrinkage, cracking and the like caused by surface moisture evaporation are effectively inhibited, and on the other hand, the mechanical strength, particularly the ductility, of the concrete material is greatly improved;

3) the use of the viscosity modifier reduces the delamination effect of the printed structure and improves the integrity of the printed structure. The method has the advantages that the mining waste copper tailing sand is used for preparing the 3D printing concrete, and the copper tailing sand is used for replacing river sand in the traditional concrete preparation, so that good cost and environmental benefit can be obtained, on one hand, the maintenance management and treatment cost of the tailings can be reduced, the pollution of the mining waste to the environment can be reduced, on the other hand, the use of the river sand can be reduced, the river bed can be protected, and the water and soil loss can be reduced. The flowability, coagulability, extrudability, constructability and the like of the 3D printing material need to be consistent with the parameters of the 3D printer. For example, if the printing speed of the printer is too slow, the printed structure is prone to stacking or wrinkling, and if the printing speed is too fast, the concrete material may be broken, on the premise that the fluidity of the concrete material is determined.

Drawings

FIG. 1 is a graph showing the effect of the extrudability evaluation test on the concrete of example 1.

FIG. 2 is a graph showing the effect of the test for evaluating the constructability of the concrete of example 1.

Detailed Description

The present invention is further explained with reference to the following examples and drawings, but the present invention is not limited thereto.

6.8-7.2 parts of quick-hardening ordinary portland cement;

1.35-1.45 parts of fly ash;

0.75-0.85 part of silica fume;

0.75-0.85 part of hollow glass beads;

7.1-7.3 parts of sand;

2.6-2.8 parts of water;

0.045-0.055 part of water reducing agent;

0.005-0.007 part of polypropylene fiber with the length of 7-10 mm;

0.005-0.007 part of basalt fiber with the length of 11-14 mm;

The specific surface area of the rapid-hardening ordinary portland cement is 348m²Kg, density 3.0g/cm³The water consumption for the standard consistency is 25.9 percent, the initial setting time is 170min, the final setting time is 210min, the loss on ignition is 3.5 percent, the content of magnesium oxide is 2.18 percent, the 3-day breaking strength is 5.7MPa, and the 3-day compressive strength is 30 MPa. The quick hardening cement is used for enabling the concrete to obtain higher early strength and is beneficial to improving the constructability of the concrete.

The loss on ignition of the fly ash is 7.1%, the water content is 0.1%, the calcium oxide content is 3.7%, the water demand ratio is 104%, and the fineness is 17.5% of the residue of a square-hole sieve with the fineness of 45 mu m.

The density of the silica fume is 2.3g/cm³The specific surface area is 25 to 29m²Water content 1.5% per gram.

The hollow glass beads have the particle size of 2-125 mu m and the density of 0.46g/cm³Bulk density of 0.29g/cm³The compression strength is 41.37MPa, the floating rate is 96%, the hollow glass beads can play a role in lubricating, and the extrudability of the concrete can be improved.

The sand has an average particle diameter of 387.5 mu m and a specific surface area of 0.101m²Natural sand per gram;

the average particle diameter of the tailing sand is 246 mu m, and the specific surface area is 0.141m²/g；

The water reducing agent is a polycarboxylic acid water reducing agent, the water reducing rate is more than 30%, and the solid content is 36.5%;

the polypropylene fiber has a length of 9mm, a diameter of 50 μm and a density of 0.9g/cm³Tensile strength is 4MPa, and elastic modulus is 3-8 GPa;

the length of the basalt fiber is 12mm, the tensile strength is 3300-4500MPa, the elastic modulus is 95-115GPa, and the elongation at break is 2.4-3.0%; the addition of the two fibers (the polypropylene fiber and the basalt fiber) can reduce the cracking of the concrete caused by the evaporation of water in the early stage and can improve the fracture toughness of the hardened concrete.

The hydroxypropyl methyl cellulose (HPMC) is a viscosity modifier, the preferred viscosity specification is 5 ten thousand viscosity, and the use of the viscosity modifier can improve the cross-section binding power between layers of the 3D printing structure, so that the integrity of the 3D printing structure is improved.

The tailing sand in the invention is copper tailing sand, iron tailing sand, gold tailing sand and the like, and the tailing sand is treated before use, so that the particle size range is ensured to be 220-plus 270 mu m, and the production and use requirements can be met.

The preparation method of the tailing sand fiber concrete capable of being printed in a 3D mode comprises the following steps:

The preparation method of the invention divides the powder, the sand and the fiber into two groups to be mixed in sequence, then mixes each additive with part of water and then adds the additives respectively, which can improve the mixing uniformity of concrete, and the powder and the fiber are put twice to improve the dispersibility of the fiber and reduce the phenomenon of fiber agglomeration, and the phenomenon of balling and agglomeration can be reduced by adding the water twice. In the preparation method, the adding sequence of the first group and the second group is not required, and the adding sequence of the third group and the fourth group is not required, so that the full mixing is ensured.

The application method of the tailing sand fiber concrete capable of being printed in 3D comprises the following steps: concrete of the formula is pumped or mechanically conveyed into a printing spray head of a 3D printer, standing time is 30-40min, the standing time refers to the time from preparation of concrete to printing, and the sectional area of an outlet of the printing spray head is set to be 180-200 mm²The extrusion speed is 0.3-0.4m³And/h, the horizontal printing speed is 250-290m/h, the vertical printing speed is 0.7-0.9m/h, the printing height of the spray head is 20-32mm, and then printing is carried out.

The concrete obtained according to the formula and the preparation method provided by the invention is printed, and the printed structural body is subjected to related performance tests, namely fluidity evaluation, constructability evaluation and compressive strength evaluation level bending strength evaluation.

Example 1

The 3D printable tailing sand fiber concrete of this embodiment is counted according to parts by weight, and the composition and the content of concrete are respectively:

7.0 parts of No. 42.5 rapid hardening ordinary portland cement;

1.4 parts of fly ash,

0.80 part of silica fume,

0.8 part of hollow glass micro-beads,

7.2 parts of natural sand, namely,

4.8 parts of copper tailing sand,

2.6 parts of water, namely,

0.05 part of a water reducing agent,

0.006 part of polypropylene fiber with the length of 9mm,

0.006 part of basalt fiber with the length of 12mm,

0.05 part of HPMC viscosity modifier with the viscosity of 5 ten thousand.

The specific surface area of the rapid-hardening ordinary portland cement is 348m²Kg, density 3.0g/cm³The water consumption for the standard consistency is 25.9 percent, the initial setting time is 170min, the final setting time is 210min, the loss on ignition is 3.5 percent, the content of magnesium oxide is 2.18 percent, the 3-day breaking strength is 5.7MPa, and the 3-day compressive strength is 30 MPa.

The density of the silica fume is 2.3g/cm³The specific surface area is 25 to 29m²(ii)/g; the particle size of the hollow glass beads is 100 mu m, and the density is 0.46g/cm³Bulk density of 0.29g/cm³The compressive strength is 41.37MPa, and the floating rate is 96 percent; the sand has an average particle diameter of 387.5 mu m and a specific surface area of 0.101m²Natural sand per gram; the average particle diameter of the copper tailing sand is 246 mu m, and the specific surface area is 0.141m²(ii)/g; the water reducing agent is a polycarboxylic acid water reducing agent, the water reducing rate is more than 30%, and the solid content is 36.5%.

The preparation method of the tailing sand fiber concrete capable of being printed in 3D mode comprises the following steps:

(1) the raw materials are divided into four groups according to the parts by weight, wherein the first group comprises 7.0 parts of 42.5# quick-hardening ordinary portland cement, 1.4 parts of fly ash, 7.2 parts of natural sand and 0.006 part of polypropylene fiber, the second group comprises 0.8 part of silica fume, 0.8 part of hollow glass microsphere, 4.8 parts of copper tailing sand and 0.006 part of basalt fiber, the third group comprises 1.3 parts of water and 0.05 part of water reducing agent, and the fourth group comprises the balance of water and 0.05 part of hydroxypropyl methyl cellulose;

(2) simultaneously feeding the first group of raw materials into a 30L horizontal stirrer for mixing and stirring, wherein the stirring speed is 45 r/min, the stirring temperature is 20 ℃ at room temperature, and the stirring time is 180s until the raw materials are completely and uniformly mixed; then correspondingly adding the raw materials of the second group into the uniformly mixed mixture at the same time, and carrying out mixing and stirring at the stirring speed of 45 revolutions per minute at the stirring temperature of 20 ℃ for 180s until the raw materials are completely and uniformly mixed;

(3) respectively and uniformly mixing the raw materials of the third group and the fourth group, adding the mixed materials of the third group into the final mixture obtained in the step (2), and stirring for 90s at the stirring temperature and the stirring speed; and finally, adding the fourth group of mixed materials at the stirring temperature and the stirring speed, and stirring for 90 seconds to obtain the concrete.

But use the tailings sand fiber concrete that this embodiment 3D printed to carry out 3D and print, specific process is: pumping the concrete with the formula into a printing spray head of a 3D printer, standing for 30min, and setting the cross section area of an outlet of the printing spray head to be 8 multiplied by 24mm²Extrusion speed of 0.3m³The horizontal printing speed is 260m/h, the vertical printing speed is 0.75m/h, and the printing height of the spray head is 24 mm; and printing according to the printing parameters to obtain the printing structural body. The printing process is smooth, and the printed structure has good integrity and good stability.

The concrete of this example and the printed structure were subjected to the following performance tests:

evaluation of fluidity:

the fluidity of the concrete in the embodiment is tested by referring to national standard 'cement mortar fluidity determination method' (GB _ T2419-2005), 'premixed concrete' (GBT14902-2012) and 'common concrete mixture performance test method Standard' (GB/T50080-: the slump is 70-88mm, the flow expansion is 200-210mm, and the flow time of the V-shaped funnel is 20-25 s.

Evaluation of extrudability:

extrudability refers to the ability of a material to be extruded through a set outlet, and if the material can be extruded under the condition of a small outlet, the material can be extruded smoothly by changing to a large-opening nozzle, and a printing nozzle with a small outlet of 8mm multiplied by 8mm is selected for the extrusion evaluation to be tested. The concrete of the embodiment can continuously and continuously print the filament with the length of 200mm under the conditions that the printing parameters of the 3D printer are 8mm multiplied by 8mm of the size of the printing nozzle, 5.4L/min of the extrusion speed, 270m/h of the horizontal printing speed and 24mm of the printing height of the nozzle, and no interruption or blockage occurs, as shown in figure 1.

And (3) evaluation of constructability:

the constructability is characterized by the capability of stacking materials to a certain height without collapse, and a printing nozzle with the size of 8mm multiplied by 24mm is selected for printing, so that the materials are stacked, and constructability evaluation is carried out (the constructability refers to the capability or the property of stacking the printing materials in the vertical direction, and the constructability evaluation test cannot be carried out by a nozzle with too small size). According to the concrete of the embodiment, under the conditions that the printing parameters of a 3D printer are that the size of a printing nozzle is 8mm multiplied by 24mm, the extrusion speed is 5.4L/min, the horizontal printing speed is 270m/min, the vertical printing speed is 1.3cm/min and the printing height of the nozzle is 24mm, 42 layers of vertical printing are not interrupted and do not collapse, the aspect ratio of the obtained structural body is 10:1, the vertical deformation of each printing layer is only 0.59%, and as shown in FIG. 2, the concrete of the embodiment shows excellent constructability and structural stability.

Evaluation of early stiffness:

the concrete of the embodiment is subjected to early rigidity test by referring to the national standard of Standard test methods for Performance of common concrete mixtures (GB/T50080-2002). The test results are: the injection resistance is 20-25kPa at the age of 30min, 30-35kPa at the age of 60min, 40-45kPa at the age of 90min, 90-110kPa at the age of 3 h, 220kPa at the age of 6 h and 0.7MPa at the age of 8 h.

Evaluation of compressive strength:

the concrete of this example was subjected to a compressive strength test in accordance with Standard test methods for mechanical Properties of ordinary concrete (GB/T50081-2002). The test results are: the compressive strength is 36MPa when the aged is 3 days, 49.6MPa when the aged is 14 days, and 54.6MPa when the aged is 28 days.

And (3) evaluating the bending strength:

the concrete of this example was subjected to a flexural strength test in accordance with Standard test methods for mechanical Properties of ordinary concrete (GB/T50081-2002). The test results are: the bending strength can reach 7.8MPa in 7 days, and the mid-span deflection is 0.31 mm.

As can be seen from the above test results, the concrete of this example can be continuously printed (fluidity problem), without clogging (extrudability problem, fig. 1), without collapsing (constructability problem, fig. 2) into a structure under the set parameters of the 3D printer, and the printed and formed structure has sufficient compressive strength and bending strength after hardening. The concrete has good fluidity, extrudability, constructability, compressive strength and bending strength.

Example 2

6.8 parts of No. 42.5 rapid hardening ordinary Portland cement;

1.35 parts of fly ash,

0.75 part of silica fume,

0.75 part of hollow glass micro-beads,

7.1 parts of natural sand, namely,

4.7 parts of copper tailing sand,

2.6 parts of water, namely,

0.05 part of a water reducing agent,

0.005 part of polypropylene fiber with the length of 9mm,

0.005 part of basalt fiber with the length of 12mm,

0.04 part of HPMC viscosity modifier with the viscosity of 5 ten thousand.

(1) the raw materials are divided into four groups according to the parts by weight, wherein the first group comprises 6.8 parts of 42.5# quick-hardening ordinary portland cement, 1.35 parts of fly ash, 7.1 parts of natural sand and 0.005 part of polypropylene fiber, the second group comprises 0.75 part of silica fume, 0.75 part of hollow glass microsphere, 4.7 parts of copper tailing sand and 0.005 part of basalt fiber, the third group comprises 1.3 parts of water and 0.05 part of water reducing agent, and the fourth group comprises the balance of water and 0.04 part of hydroxypropyl methyl cellulose;

(2) simultaneously feeding the raw materials of the second group into a 30L horizontal stirrer for mixing and stirring, wherein the stirring speed is 45 r/min, the stirring temperature is 20 ℃ at room temperature, and the stirring time is 180s until the raw materials are completely and uniformly mixed; then correspondingly adding the raw materials of the first group into the uniformly mixed mixture at the same time, and carrying out mixing and stirring at the stirring speed of 45 revolutions per minute at the stirring temperature of 20 ℃ for 180s until the raw materials are completely and uniformly mixed;

(3) uniformly mixing the raw materials of the third group and the fourth group respectively, adding the mixed materials of the fourth group into the final mixture obtained in the step (2), and stirring for 90s at the stirring temperature and the stirring speed; and finally, adding the mixed materials of the third group at the stirring temperature and the stirring speed, and stirring for 90 seconds to obtain the concrete.

The concrete of the embodiment is transported into a printing nozzle of a printer after standing for 30min, and the sectional area of the nozzle outlet is 8 multiplied by 24mm²Extrusion speed 0.3m³The horizontal printing speed is 250m/h, the vertical printing speed is 0.7m/h, and the printing height of the nozzle is 26 mm. The printing parameters are set according to the above, the printing process is smooth, and the integrity and the stability of the printed structure are good.

Example 3

7.2 parts of No. 42.5 rapid hardening ordinary portland cement;

1.45 parts of fly ash,

0.85 part of silica fume,

0.85 part of hollow glass micro-beads,

7.3 parts of natural sand, namely,

4.9 parts of copper tailing sand,

2.8 parts of water, namely,

0.05 part of a water reducing agent,

0.007 part of polypropylene fiber with the length of 9mm,

0.007 part of basalt fiber with the length of 12mm,

0.06 part of HPMC viscosity modifier with the viscosity of 5 ten thousand.

The concrete material obtained in this example was transported to the printing head of a printer after standing for 40min, the sectional area of the head outlet was 8X 24mm, as in example 1²Extrusion speed 0.4m³The horizontal printing speed is 290m/h, the vertical printing speed is 0.9m/h, and the printing height of the nozzle is 20 mm. According to the printing setting parameters, the printing process is smooth, and the integrity and the stability of the printed structure are good.

Example 4

The composition, preparation method and printing parameters of the concrete of this example were the same as those of example 1, except that 0.045 parts of hydroxypropylmethylcellulose was used in this example.

Comparative example 1

The material types, addition amounts, stirring and mixing manners, and printing parameters were the same as those in example 1, except for 6.0 parts of natural sand and 6.0 parts of copper tailings. The test result shows that: the printing process can be carried out smoothly, but the printed structure is inclined to collapse due to strong concrete fluidity, and the structure cannot be molded. The replacement amount of the natural sand in this comparative example was 50%, and the compressive strength test for 28 days was carried out, and the compressive strength was 44.1MPa, which was much smaller than that of example 1.

Comparative example 2

The material types, addition amounts, preparation methods and printing parameters were the same as in example 2, except that the standing time after completion of concrete mixing was adjusted to 45 min. The test result shows that: because the standing time is too long, the concrete material is converted into a molding state from a flow state, the phenomenon of interruption often occurs when the concrete material is extruded from a printing nozzle, and the printing process cannot be smoothly carried out.

Comparative example 3

Except for 0.01 part of polypropylene fiber and 0.01 part of basalt fiber, the types, the addition amounts, the preparation methods and the printing parameters of the other materials were the same as those of example 3. The test result shows that: because the mixing amount of the fibers is large, the fibers in the concrete mixture are led to have a cluster phenomenon, so that in the printing process, the sprayer is blocked, and the printing process cannot be smoothly carried out.

Comparative example 4

The material types, addition amounts, preparation methods and printing parameters were the same as those of example 2 except that the HPMC viscosity modifier was 0.02 part and the standing time was 30 min. The test result shows that: the printing process is smooth, but the interface bonding force between layers of the printing structure is poor, obvious layering phenomenon occurs, and the integrity of the printed structure is poor.

Comparative example 5

Except that the extrusion speed is 0.5m³The types of materials, the amounts of addition, the stirring and mixing method, and the printing parameters were the same as those in example 2 except that the horizontal printing speed was 210 m/h. The test result shows that: the concrete material can be smoothly extruded from the printing head, but because the extrusion speed of the concrete is high, and the printing speed is low, the printed concrete is accumulated near the nozzle, and the printed plane is wrinkled.

Comparative example 6

The preparation method and the raw material composition of comparative example 6 were the same as those of example 4 except that the HPMC viscosity modifier was 0.015 parts in this comparative example.

Comparative example 7

The preparation method and the raw material composition of comparative example 7 were the same as those of example 4 except that the HPMC viscosity modifier was 0.030 parts in this comparative example.

The bending strength of comparative example 6, comparative example 7 and example 4 was measured for 7 days, and the results were 6.5MPa, 6.7MPa and 7.2MPa, respectively. Therefore, the 7-day flexural strength in the inventive formulation is better.

The invention is applicable to the prior art, and the raw materials involved are either commercially available or obtained by conventional methods.

Claims

1. The method for using the 3D printed tailing sand fiber concrete comprises the steps of pumping or mechanically conveying the concrete into a printing spray head of a 3D printer, standing for 30-40min, and setting the cross section area of an outlet of the printing spray head to be 180-200 mm²The extrusion speed is 0.3-0.4m³The horizontal printing speed is 250-290m/h, and then printing is carried out;

the concrete comprises the following components in parts by weight:

6.8-7.2 parts of quick-hardening ordinary portland cement;

1.35-1.45 parts of fly ash;

0.75-0.85 part of silica fume;

0.75-0.85 part of hollow glass beads;

7.1-7.3 parts of natural sand;

2.6-2.8 parts of water;

0.045-0.055 part of water reducing agent;

0.005-0.007 part of polypropylene fiber with the length of 7-10 mm;

0.005-0.007 part of basalt fiber with the length of 11-14 mm;

2. Use according to claim 1, characterized in that said rapid-hardening Portland cement has a specific surface area of 348m²Kg, density 3.0g/cm³The water consumption for the standard consistency is 25.9 percent, the initial setting time is 170min, the final setting time is 210min, the loss on ignition is 3.5 percent, the content of magnesium oxide is 2.18 percent, the 3-day breaking strength is 5.7MPa, and the 3-day compressive strength is 30 MPa.

3. The use method of the fly ash as claimed in claim 1, wherein the loss on ignition of the fly ash is 7.1%, the water content is 0.1%, the calcium oxide content is 3.7%, the water demand ratio is 104%, and the fineness is 17.5% of the screen residue of a 45 μm square-hole sieve.

4. Use according to claim 1, characterized in that the silica fume has a density of 2.3g/cm³The specific surface area is 25 to 29m²(ii)/g; the hollow glass beads have the particle size of 2-125 mu m and the density of 0.46g/cm³Bulk density of 0.29g/cm³The compressive strength is 41.37MPa, and the floating rate is 96 percent; the natural sand has an average particle diameter of 387.5 μm and a specific surface area of 0.101m²Natural sand per gram; the specific surface area of the tailing sand is 0.141m²(ii)/g; the water reducing agent is a polycarboxylic acid water reducing agent, the water reducing rate is more than 30%, and the solid content is 36.5%.

5. Use according to claim 1, characterized in that the tailings are copper, iron or gold tailings.

6. A method of preparing 3D printed tailings sand fibre concrete for use in preparing concrete for use according to any one of claims 1 to 5, comprising the steps of: