CN109987894B - Rammed earth building material and method for evaluating rammed earth building material - Google Patents
Rammed earth building material and method for evaluating rammed earth building material Download PDFInfo
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- CN109987894B CN109987894B CN201910369550.3A CN201910369550A CN109987894B CN 109987894 B CN109987894 B CN 109987894B CN 201910369550 A CN201910369550 A CN 201910369550A CN 109987894 B CN109987894 B CN 109987894B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/0076—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials characterised by the grain distribution
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/001—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing unburned clay
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
Abstract
The invention provides rammed earth building materials and a method for evaluating the rammed earth building materials. The rammed earth building material comprises the following components in percentage by mass: 0 to 56.9 percent of gravel, 32.04 to 65.95 percent of sand grain, 3.98 to 13.01 percent of powder particle and 7.08 to 21.04 percent of sticky particle. The method for evaluating rammed earth building materials comprises the following steps: obtaining an optimal grading interval and a limit optimal grading interval according to rammed earth building materials; measuring the particle size distribution of the tested soil sample by using a screening method and a sedimentation method to obtain a grading curve of the tested soil sample; and comparing the measured soil sample grading curve with the optimal grading interval and the ultimate optimal grading interval to obtain an evaluation result. The application provides a rammed earth building soil material, wall body, building that the rammed earth formed, intensity and stability are high, the shrinkage is low. The method for evaluating the rammed-earth building soil provided by the application can be used for scientifically and accurately evaluating and optimizing the modern rammed-earth building soil.
Description
Technical Field
The invention relates to the field of rammed earth buildings, in particular to rammed earth building materials and a method for evaluating the rammed earth building materials.
Background
In recent years, with the development of green buildings, the raw earth materials are more and more concerned, modern rammed earth buildings are rising in the field of buildings, and a large number of excellent modern rammed earth construction cases are emerged at home and abroad in recent decades. The inherent defects of the traditional rammed earth building in the aspects of mechanics and durability are core factors for restricting the modern application of the traditional rammed earth building, and the core factors are closely related to the gradation of the rammed earth building (the grade and the proportion relation of soil grains contained in the earth). The modern rammed earth building is different from the traditional rammed earth building in that the gradation of the soil is treated, and the mechanical property and the durability of the rammed earth wall are improved by adjusting the gradation of the soil of the rammed earth building.
In view of the influence of different grain sizes contained in the rammed earth building earth on the earth material characteristics and rammed earth walls, the proper earth material grading is of great importance for modern rammed earth buildings. However, relatively scientific soil grading standards are not formed at home at present, and no grading evaluation and optimization method system corresponding to the soil grading standards is provided.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide rammed earth building materials which are reasonable in gradation, and the rammed earth building obtained by using the building materials is high in stability, high in strength and low in dry shrinkage rate.
The second purpose of the invention is to provide a method for evaluating rammed earth building materials, which is simple and easy to implement and has strong operability.
In order to achieve the above purpose, the invention provides the following technical scheme:
a rammed earth building material comprises the following components in percentage by mass: 0 to 56.9 percent of gravel, 32.04 to 65.95 percent of sand grain, 3.98 to 13.01 percent of powder particle and 7.08 to 21.04 percent of sticky particle.
According to the international system division standard commonly adopted by the international earth-building community, soil particles with a particle size of more than 2mm are generally called gravel, soil particles with a particle size of between 2mm and 0.02mm are called sand particles, soil particles with a particle size of between 0.02mm and 0.002mm are called powder particles, and soil particles with a particle size of less than 0.002mm are called clay particles. The modern rammed earth building soil material grading mainly contains soil particles of the four particle grades, wherein the properties of gravels and sand particles (more than 0.02mm) are similar, and the gravels have no characteristics of cohesiveness, adhesiveness and the like and are used as main aggregates in rammed earth materials. The particle size and the property of the powder particles are between those of the clay particles and the gravel, and the powder particles are used as secondary aggregates in the rammed earth material. Because of its water-holding capacity, wet-swelling property, plasticity, cohesiveness, adhesiveness and other properties, the clay is a key element for binding, polymerizing and molding a soil particle composition containing particles, sand, gravel and the like as an aggregate, similarly to cement in concrete, and is important in rammed earth. In addition, when the content of the clay in the soil is less than 5%, the clay is not regarded as "soil" in the definition of soil mechanics, lacks necessary characteristics such as plasticity, cohesiveness and adhesiveness, cannot meet the requirements of mechanical properties of walls, and cannot be used as a rammed soil material. When the clay is rich in clay, the rammed earth wall body can generate a shrinkage rate of up to 20% in a drying process, and large cracks are generated, so that the rammed earth wall body is difficult to use for rammed earth construction.
Preferably, the rammed earth building material comprises the following components in percentage by mass: 10.4 to 50 percent of gravel, 36.75 to 59.92 percent of sand, 4.36 to 10.46 percent of powder particles and 8.89 to 19.22 percent of sticky particles.
Preferably, the rammed earth building material comprises the following components in percentage by mass:
0-34.14% of first gravel, 0-22.76% of second gravel, 12.64-24.95% of fine sand, 19.4-41% of coarse sand, 3.98-13.01% of powder particles and 7.08-21.04% of sticky particles;
the first gravels are gravels with the grain diameter of 2-16mm, and the second gravels are gravels with the grain diameter of more than 16mm and less than or equal to 32 mm; the fine sand is sand with the grain size of 0.02-0.2mm, and the coarse sand is sand with the grain size of more than 0.2mm and less than 2 mm.
Further preferably, the rammed earth building material comprises the following components in percentage by mass:
10.4-30% of the first gravel, 0-20% of the second gravel, 14.45-22.72% of the fine sand, 22.3-37.2% of the coarse sand, 4.36-10.46% of the powder particles and 8.89-19.22% of the sticky particles.
A method of evaluating rammed earth construction material comprising the steps of:
obtaining a theoretical ideal grading upper limit curve, a theoretical ideal grading lower limit curve, a theoretical limit grading floating upper limit curve and a theoretical limit grading floating lower limit curve according to the rammed earth building materials;
obtaining an optimal grading interval according to the theoretical ideal grading upper limit curve and the theoretical ideal grading lower limit curve, and obtaining a limit optimal grading interval according to the theoretical limit grading floating upper limit curve and the theoretical limit grading floating lower limit curve;
measuring the particle size distribution of the tested soil sample by using a screening method and a sedimentation method to obtain a grading curve of the tested soil sample;
and comparing the measured soil sample grading curve with the optimal grading interval and the limit optimal grading interval to obtain an evaluation result.
The proportion corresponding to the theoretical ideal gradation upper limit curve is as follows: 10.4% of gravel, 59.92% of sand, 10.46% of powder particles and 19.22% of sticky particles; the proportion corresponding to the theoretical ideal gradation lower limit curve is as follows: 50% of gravel, 36.75% of sand, 4.36% of powder particles and 8.89% of sticky particles; the ratio corresponding to the theoretical limit gradation floating upper limit curve is as follows: 0% of gravel, 65.95% of sand grains, 13.01% of powder particles and 21.04% of sticky particles; the ratio corresponding to the theoretical limit gradation floating lower limit curve is as follows: 56.9 percent of gravel, 32.04 percent of sand, 3.98 percent of powder particles and 7.08 percent of sticky particles.
The 4 grading curves (particle size-mass percentage curves) are obtained by using the limit ratio, and then the optimal grading interval and the limit optimal grading interval are obtained by fitting.
Preferably, the process of evaluating comprises: when the measured soil sample grading curve falls into the optimal grading interval, judging the soil sample grading curve to be excellent; when the grading curve of the tested soil sample falls between the optimal grading interval and the limit optimal grading interval, judging that the grading curve is qualified; and when the grading curve of the tested soil sample is outside the limit optimal grading interval, judging that the grading curve is unqualified.
After the evaluation is finished, the method further comprises the following optimization steps: the method can adjust the soil sample to be detected according to the comparison of the grading curve of the soil sample to be detected with the optimal grading interval and the limit optimal grading interval, reduce the content of the components corresponding to the particle size with the content higher than the interval range, and increase the content of the components corresponding to the particle size with the content lower than the interval range, so that the content of each particle size interval of the soil sample to be detected falls into the interval.
Preferably, the screening method is used for detecting the mass percentage of particles with different particle sizes, the particle sizes of which are larger than 0.08mm, in the soil sample to be detected, and the sedimentation method is used for detecting the mass percentage of particles with the particle sizes of which are smaller than or equal to 0.08mm in the soil sample to be detected.
Further preferably, the screening method comprises the steps of:
stacking multiple layers of sieve trays according to the order that the pore diameters are sequentially reduced from top to bottom, drying the soil sample to be detected to constant weight, and then sieving by using the sieve trays;
immersing each screened sieve tray with water one by one and cleaning small particles, and merging the cleaned objects of the adjacent upper layer of sieve tray into the next layer of sieve tray;
and respectively drying the particles which are not sieved and the particles with the particle size of less than or equal to 0.08mm to constant weight, and calculating the mass percentage of the particles with different particle sizes with the particle size of more than 0.08mm in the soil sample to be tested.
The multi-layer sieve tray is arranged for sieving components with different particle size intervals and measuring the mass percentage of the components with different particle sizes.
Further preferably, the sedimentation method comprises the steps of:
mixing the dried particles with the particle diameter of less than or equal to 0.08mm with a dispersing agent and water, taking the aqueous solution of the dispersing agent as a reference, fixing the volume, keeping the constant temperature to obtain a mixed solution and a reference solution, respectively stirring, and measuring the mixed solution A by using a hydrometertnAnd specific gravity values B of the reference solution at a plurality of different time pointstnAccording to 8 (A)tn-Btn) P is the mass percentage of the particles with corresponding particle sizes;
wherein P is the sieving rate of particles with a 0.08mm screen.
The measurement time intervals correspond to the particle sizes, so that the specific gravity measurement is performed at different time intervals, and the mass percentages of the particles of the corresponding particle sizes can be obtained.
More preferably, the method for evaluating rammed earth building materials further comprises the step of optimizing the tested soil sample according to the evaluation result, and the optimizing step comprises the following steps:
determining the components to be adjusted according to the comparison result;
measuring the grading curve of the standby raw material corresponding to the component to be adjusted;
and calculating the use amount of the components needing to be adjusted, and fitting the grading curve of the raw materials to be used and the grading curve of the soil sample to be measured to obtain the grading curve of the target soil sample, so that the grading curve of the target soil sample falls into the optimal grading interval or the limit optimal grading interval.
For the soil sample needing to be adjusted, the content of the components below the interval is increased according to the comparison result of the measured soil sample curve and the theoretical ideal grading upper limit curve, the theoretical ideal grading lower limit curve, the theoretical limit grading floating upper limit curve and the theoretical limit grading floating lower limit curve, and is corrected according to the smoothness degree of the curves, the smoothness degree of the curves is better, the more uniform the particle size distribution is, the higher the stability and strength of the soil material under the grading are, and the lower the dry shrinkage rate is, and finally the proportion meeting the requirements is obtained.
In fact, most rammed earth construction soil samples are sampled below 30-50 cm of the earth surface, have high soil content and low gravel content, and therefore, gravel and sand particles are generally supplemented and adjusted.
Compared with the prior art, the invention has the beneficial effects that:
(1) the rammed earth building material provided by the application has the advantages of good stability, high strength and low dry shrinkage;
(2) the application provides a method for evaluating rammed earth building soil, maneuverability is strong, and the judgement degree of accuracy is high, can be quick judge whether surveyed soil sample is fit for being used for rammed earth building to adjust according to this.
Drawings
To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of the present invention.
FIG. 1 is a graph of sieve plate pore size versus percent of particles sieved for soil samples provided in examples 1-5;
FIG. 2 is a graph showing the sieve plate pore size versus percent of particles sieved for a soil sample as provided in example 6;
fig. 3 is a graph showing a sieve plate pore size-percent sieved particle curve, a gravel grading curve, a sand grading curve, and a target soil sample grading curve of the soil sample provided in comparative example 1.
Detailed Description
The terms as used herein:
"prepared from … …" is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements 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.
The conjunction "consisting of … …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when the range "1 ~ 5" is disclosed, the ranges described should be construed to include the ranges "1 ~ 4", "1 ~ 3", "1 ~ 2 and 4 ~ 5", "1 ~ 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
In these examples, the parts and percentages are by mass unless otherwise indicated.
"part by mass" means a basic unit of measure indicating a mass ratio of a plurality of components, and 1 part may represent any unit mass, for example, 1g or 2.689 g. If we say that the part by mass of the component A is a part by mass and the part by mass of the component B is B part by mass, the ratio of the part by mass of the component A to the part by mass of the component B is a: b. alternatively, the mass of the A component is aK and the mass of the B component is bK (K is an arbitrary number, and represents a multiple factor). It is unmistakable that, unlike the parts by mass, the sum of the parts by mass of all the components is not limited to 100 parts.
"and/or" is used to indicate that one or both of the illustrated conditions may occur, e.g., a and/or B includes (a and B) and (a or B).
For the acquisition of the grading interval, two factors are mainly considered: compressive strength and dry shrinkage. The compressive strength is an important parameter for reflecting the mechanical property of the wall material. The traditional rammed earth material which is often used as a main body material of a wall body has larger difference of compressive strength due to different soil compositions. According to cubic test block compression tests performed by researchers at home and abroad aiming at the soil quality of different regions, the compression strength of the traditional rammed soil is usually 0.3-1.8 MPa. However, if the compositions of the sticky particles, the powder particles, the sand particles and the gravels in the soil are prepared to a specific proportion interval according to the particle size grading principle on the basis of the traditional rammed soil, the compaction degree of a rammed body formed by the soil is far higher than that of the traditional rammed soil, and the mechanical property and the durability of the rammed body can be greatly improved. According to the practical results of the soil material test and the ramming engineering of the inventor, the average compressive strength of the wall body formed by ramming the rammed soil material obtained by blending the particle size grading interval can reach 2-3.5MPa, which is 2-4 times of the conventional rammed soil strength.
In addition, the dry shrinkage phenomenon of the rammed earth wall is a problem which needs to be particularly taken into consideration. As mentioned above, the only clay that has both viscosity and water absorption in the soil composition is the clay. During the ramming process of the soil materials, the clay granules absorb water and expand, after ramming is completed, water overflows along with the gradual drying of the soil wall, and the clay granules shrink to cause the soil wall to shrink and generate cracks. The dry shrinkage rate of rammed earth materials is greatly different due to different content of the clay. Generally, the dry shrinkage of the traditional rammed earth material is between 0.4% and 2%, which is much larger than that of concrete (generally between 0.03% and 0.08%), and especially for rammed earth buildings constructed on site integrally, the high dry shrinkage can cause a large amount of dry shrinkage cracks on the wall surface. According to the soil test and the practical results of the rammed soil engineering of the inventor, the wall body formed by rammed soil is obtained by blending the particle size grading interval according to the invention, the dry shrinkage rate is about 0.2% on average, the dry shrinkage rate of the wall body can be obviously reduced, and the crack phenomenon can be weakened.
Embodiments of the present invention will be described in detail below with reference to specific examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Example 1
The rammed earth building material comprises, by mass, 10.4% of gravels, 59.92% of sand grains, 10.46% of powder particles and 19.22% of sticky particles.
Wherein the gravel is gravel with the particle size of 2-16mm, the sand grains comprise 37.2% of coarse sand and 22.72% of fine sand, the fine sand is sand grains with the particle size of 0.02-0.2mm, and the coarse sand is sand with the particle size of more than 0.2mm and less than 2 mm.
Example 2
The rammed earth building material comprises, by mass, 50% of gravels, 36.75% of sand grains, 4.36% of powder particles and 8.89% of sticky particles.
Wherein the gravel comprises 30% of first gravel and 20% of second gravel, the first gravel is gravel with the particle size of 2-16mm, and the second gravel is gravel with the particle size of more than 16mm and less than or equal to 32 mm; the sand grains comprise 22.3 percent of coarse sand and 14.45 percent of fine sand, the fine sand is the sand grains with the grain size of 0.02-0.2mm, and the coarse sand is the sand with the grain size of more than 0.2mm and less than 2 mm.
Example 3
A rammed earth building material comprises 65.95% of sand grains, 13.01% of powder particles and 21.04% of sticky particles by mass percent.
Wherein the sand grains comprise 41 percent of coarse sand and 24.95 percent of fine sand, the fine sand is sand grains with the grain size of 0.02-0.2mm, and the coarse sand is sand with the grain size of more than 0.2mm and less than 2 mm.
Example 4
The rammed earth building material comprises, by mass, 56.9% of gravels, 32.04% of sand grains, 3.98% of powder particles and 7.08% of sticky particles.
The gravel comprises 34.14% of first gravel and 22.76% of second gravel, wherein the first gravel is gravel with the particle size of 2-16mm, and the second gravel is gravel with the particle size of more than 16mm and less than or equal to 32 mm; the sand grains comprise 19.4 percent of coarse sand and 12.64 percent of fine sand, the fine sand is sand grains with the grain size of 0.02-0.2mm, and the coarse sand is sand with the grain size of more than 0.2mm and less than 2 mm.
The particle size distribution of the rammed earth construction material provided in examples 1-4 was determined using sieving and sedimentation methods, with sieve plate aperture as the abscissa and percent sieved particles as the ordinate, and the results are shown in figure 1. The example 1 corresponds to a curve B (theoretical ideal gradation upper limit curve), the example 2 corresponds to a curve D (theoretical ideal gradation lower limit curve), the example 3 corresponds to a curve a (theoretical limit gradation upper limit curve), and the example 4 corresponds to a curve C (theoretical limit gradation lower limit curve).
The region between curve a and curve C is the ultimate optimal grading interval and the region between curve B and curve D is the optimal grading interval.
Example 5
Taking a soil sample to be tested in a permanently-determined region of Longyan City in Fujian province, and testing the particle size distribution according to the following testing method:
in the first stage, the mass percentage of different particles with the particle size larger than 0.08mm in the soil material is determined. 1 set of standard square mesh sieve trays was used: 20mm, 10mm, 5mm, 2mm, 1mm, 0.4mm, 0.2mm, 0.08mm, specifically including the following steps:
1. preparation of soil sample
Piling soil in a soil containing basin into a cone shape (800-; leveling a soil pile, dividing soil materials into four parts along a diagonal line, and uniformly selecting soil samples in each area, wherein the total weight is 300-500 g; placing the soil sample into a drying box, setting the temperature to be 105 ℃, and completely drying to constant weight; and weighing the mass DSW value of the dry soil sample.
2. Test operation
1) Performing rapid dry screening: stacking all the sieve trays in the order of big top and small bottom in the aperture, placing the sieve trays on an aluminum tray (the first tray), pouring the completely dried soil sample into a sieve tray column from the top, covering the sieve tray column with a cover and shaking the sieve tray column;
2) the first sieve tray (20 mm diameter) was placed in an aluminum tray (second);
3) adding distilled water until the mesh of the sieve tray is immersed for 1cm, and dissolving and separating sand and fine particles adhered to particles which are not sieved on the sieve tray;
4) carefully cleaning large particles by hand and small particles by a brush;
5) taking out the sieve tray from water, and washing the sieve tray clean by distilled water by using a water drawing bottle;
6) placing the particles which are not sieved into a metal basin (weighing and recording the weight of the dry basin in advance), and placing the metal basin into a drying oven for drying;
7) when the soil sample is dried to constant weight, recording the weighing result in the table;
8) placing the next sieve tray (10mm) in the aluminum tray (third), pouring the water and fines from the second aluminum tray into it, and then repeating the operations of 3) -7) for all sieve trays;
9) for the remaining particles with a diameter of less than 0.08 mm: and (3) precipitating the water, sucking out the water by using a transparent plastic pipe when the water is completely clear, and putting the tray into a drying oven for drying.
The second stage is called sedimentation method, the experimental principle is based on the precipitation law, and the sedimentation velocity is related to the particle size. The principle of dispersion and sedimentation technology is adopted for a soil sample with given weight, the density of the suspension is reduced along with the sedimentation of the initial uniformly dispersed suspension, the speed of density reduction is directly related to the sedimentation velocity of the particles, and the sedimentation velocity is related to the particle size of the particles, and the mass percentage corresponding to the known particle size can be calculated from the density of the mixed suspension through a corresponding calculation formula.
In stage two, the mass percentages of different particles with diameters less than 0.08mm in the soil are mainly determined, comprising the following steps:
1. preparation of the dispersant
Mixing sodium hexametaphosphate and distilled water in a mass ratio of 1: 19;
by using sodium hexametaphosphate as a dispersing agent, the content percentage of particles with each particle size in the particles with the particle size of less than or equal to 0.08mm can be better measured, and the error is reduced.
2. Sample preparation
1) Crushing particles with diameter less than 0.08mm (the particles with diameter less than 0.08mm which are dried after being sieved) into powder by using 1 pestle with rubber head, and weighing 20g of the powder and putting the powder into a glass beaker;
2) adding 15ml of dispersing agent and 125ml of distilled water into a beaker;
3) stirring for several minutes by a constant-temperature electric stirrer and then standing for 12-15 hours;
4) stirring again for 15 minutes with a constant temperature electric stirrer, ensuring that the temperature of the mixture is kept at 40 ℃ during stirring;
5) pouring the soil sample into a measuring flask, adding distilled water until the soil sample is full of 1 liter, and stirring for 3 minutes by using a manual stirrer;
3. preparation of reference reagent
1) Pouring 15ml of dispersing agent into another measuring flask, and adding distilled water until the measuring flask is full of 1 liter;
2) inserting a thermometer and a hydrometer;
3) standing until the temperatures of the two measuring bottles are the same;
4. operation of
1) Stirring the mixed solution with a manual stirrer for 3 minutes;
2) after waiting for 45 seconds, the hydrometer is gently inserted into the measuring flask;
3) respectively timing the 1 st minute and the 2 nd minute by using a timer, and reading corresponding values A on a hydrometertnThen taking out the hydrometer;
4) in the following measurement time (5 th minute, 10 th minute, 30 th minute, 60 th minute, 2 nd hour, 5 th hour and 24 th hour), the gravimeter was inserted into the mixed solution 15 seconds in advance, and immediately taken out after reading;
5) reading the value B of the specific gravity meter in the reference reagent simultaneously according to the same methodtn。
According to 8 (A)tn-Btn) P is the mass percentage of the particles with the corresponding particle size, wherein P is the sieving rate of the particles with a 0.08mm sieve (namely the mass percentage of the particles with the particle size of less than or equal to 0.08mm in the soil sample). The correspondence between time and particle size is shown in table 1 below:
TABLE 1 correspondence of time to particle size
Drawing a curve on the test data to obtain a curve E, and measuring and calculating the component proportion as follows: 29.36 percent of gravel, 44.64 percent of sand, 11.5 percent of powder particles and 14.5 percent of sticky particles. The curve E falls within the optimal grading interval and the soil sample is excellent rammed earth building material.
Example 6
A soil sample to be tested, namely denying chen county poa torhodgkangcun in gansu province, was taken, and a particle size distribution test was performed according to the test method of example 5, with the result shown as a curve F in fig. 2. The proportion of each component is as follows: 43% of gravel, 37% of sand, 11% of powder and 9% of sticky particles.
And judging that the curve F falls into the limit optimal grading interval, but not all the curves fall into the optimal grading interval, and judging that the curve F is qualified.
It should be noted that, the inventor tests prove that the smoother the sieve plate aperture-sieving particle percentage curve is, the higher the compressive strength of the rammed earth building material is, so that when determining the ultimate optimal grading interval and the optimal grading interval, after obtaining each measured point value, the curve is fitted to improve the smoothness, and an ideal interval is obtained. The mass contents of corresponding gravels, sands, powder particles and sticky particles can be measured and calculated through a sieve plate aperture-sieve particle percentage curve.
Comparative example 1
Another soil sample to be tested in the permanently-determined region of longstone city, fujian province is taken, and the particle size distribution test is performed according to the test method of the embodiment 5, and the result is shown as a curve G in fig. 3. The proportion of each component is as follows: 0% of gravel, 26% of sand, 32% of powder particles and 52% of sticky particles.
And judging that the curve G does not fall into the limit optimal grading interval or the optimal grading interval, and judging that the curve G is unqualified.
Optimizing the soil sample:
and determining the components needing to be adjusted to be gravel and sand according to the comparison result of the measured soil sample curve and the theoretical ideal grading upper limit curve, the theoretical ideal grading lower limit curve, the theoretical limit grading floating upper limit curve and the theoretical limit grading floating lower limit curve.
And measuring the particle size distribution of the ready-to-use raw materials of the gravel and the sand grains to obtain a grading curve H of the gravel and a grading curve I of the sand grains.
And calculating the addition amounts of the gravel and the sand according to a formula of X% gravel, Y% sand and Z% soil sample, and fitting a grading curve H of the gravel, a grading curve I of the sand and a grading curve G of the tested soil sample to obtain a grading curve J of the target soil sample.
And correcting the smoothness of the curve as required to ensure that the particle size distribution is more uniform, the soil material under the grading has higher stability and strength and lower dry shrinkage.
The proportion of each component is as follows: 44.26% of gravel, 32.58% of sand grains, 7.21% of powder particles and 15.95% of sticky particles. Curve J falls within the optimum grading interval and the soil sample is excellent rammed earth building material.
The compacted earth building materials of examples 1 to 6 and comparative example 1 were subjected to the compression strength and the dry shrinkage test, and the results are shown in the following table 2:
TABLE 2 test data
As can be seen from the data in the table 2, the soil material within the soil material proportioning range of the rammed-soil building provided by the application has good compressive strength and lower dry shrinkage rate, and the rammed-soil building using the soil material has excellent performance and high stability.
The invention provides a grading interval of the soil used by modern rammed earth buildings with good stability through a large amount of rammed earth engineering practices and soil experiments, converts the grading interval into a grading interval curve chart, provides a set of complete soil grading evaluation and optimization system relatively suitable for the modern rammed earth building practices according to the grading interval curve chart, and provides scientific and efficient reference and reference for the building practices of related practitioners.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Claims (8)
1. A method of evaluating rammed earth construction material, comprising the steps of:
obtaining a theoretical ideal grading upper limit curve, a theoretical ideal grading lower limit curve, a theoretical limit grading floating upper limit curve and a theoretical limit grading floating lower limit curve according to rammed earth building materials; the rammed earth building material comprises the following components in percentage by mass: 0 to 56.9 percent of gravel, 32.04 to 65.95 percent of sand, 3.98 to 13.01 percent of powder particles and 7.08 to 21.04 percent of sticky particles; the proportion corresponding to the theoretical ideal gradation upper limit curve is as follows: 10.4% of gravel, 59.92% of sand, 10.46% of powder particles and 19.22% of sticky particles; the ratio corresponding to the theoretical ideal gradation lower limit curve is as follows: 50% of gravel, 36.75% of sand, 4.36% of powder particles and 8.89% of sticky particles; the ratio corresponding to the theoretical limit gradation floating upper limit curve is as follows: 0% of gravel, 65.95% of sand grains, 13.01% of powder particles and 21.04% of sticky particles; the ratio corresponding to the theoretical limit gradation floating lower limit curve is as follows: 56.9 percent of gravel, 32.04 percent of sand, 3.98 percent of powder particles and 7.08 percent of sticky particles; the soil with the grain diameter larger than 2mm is called gravel, the soil with the grain diameter between 2mm and 0.02mm is called sand, the soil with the grain diameter between 0.02mm and 0.002mm is called powder, and the soil with the grain diameter smaller than 0.002mm is called sticky grain;
obtaining an optimal grading interval according to the theoretical ideal grading upper limit curve and the theoretical ideal grading lower limit curve, and obtaining a limit optimal grading interval according to the theoretical limit grading floating upper limit curve and the theoretical limit grading floating lower limit curve;
measuring the particle size distribution of the tested soil sample by using a screening method and a sedimentation method to obtain a grading curve of the tested soil sample;
comparing the measured soil sample grading curve with the optimal grading interval and the limit optimal grading interval to obtain an evaluation result;
the process of evaluating includes: when the measured soil sample grading curve falls into the optimal grading interval, judging the soil sample grading curve to be excellent; when the grading curve of the tested soil sample falls between the optimal grading interval and the limit optimal grading interval, judging that the grading curve is qualified; and when the grading curve of the tested soil sample is outside the limit optimal grading interval, judging that the grading curve is unqualified.
2. The method of claim 1, wherein the rammed earth building material comprises, in mass percent: 10.4 to 50 percent of gravel, 36.75 to 59.92 percent of sand, 4.36 to 10.46 percent of powder particles and 8.89 to 19.22 percent of sticky particles.
3. The method of claim 1, wherein the rammed earth building material comprises, in mass percent:
0-34.14% of first gravel, 0-22.76% of second gravel, 12.64-24.95% of fine sand, 19.4-41% of coarse sand, 3.98-13.01% of powder particles and 7.08-21.04% of sticky particles;
the first gravels are gravels with the grain diameter of 2-16mm, and the second gravels are gravels with the grain diameter of more than 16mm and less than or equal to 32 mm; the fine sand is sand with the grain size of 0.02-0.2mm, and the coarse sand is sand with the grain size of more than 0.2mm and less than 2 mm.
4. The method of claim 3, wherein the rammed earth building material comprises, in mass percent:
10.4-30% of the first gravel, 0-20% of the second gravel, 14.45-22.72% of the fine sand, 22.3-37.2% of the coarse sand, 4.36-10.46% of the powder particles and 8.89-19.22% of the sticky particles.
5. The method of claim 1, wherein the sieving method is used to detect the mass percentage of particles with different particle sizes greater than 0.08mm in the soil sample to be tested, and the sedimentation method is used to detect the mass percentage of particles with particle sizes less than or equal to 0.08mm in the soil sample to be tested.
6. The method of claim 5, wherein the screening method comprises the steps of:
stacking multiple layers of sieve trays according to the order that the pore diameters are sequentially reduced from top to bottom, drying the soil sample to be detected to constant weight, and then sieving by using the sieve trays;
immersing each screened sieve tray with water one by one and cleaning small particles, and merging the cleaned objects of the adjacent upper layer of sieve tray into the next layer of sieve tray;
and respectively drying the particles which are not sieved and the particles with the particle size of less than or equal to 0.08mm to constant weight, and calculating the mass percentage of the particles with different particle sizes with the particle size of more than 0.08mm in the soil sample to be tested.
7. The method of claim 5, wherein the settling process comprises the steps of:
mixing the dried particles with the particle diameter of less than or equal to 0.08mm with a dispersing agent and water, taking the aqueous solution of the dispersing agent as a reference, fixing the volume, keeping the constant temperature to obtain a mixed solution and a reference solution, respectively stirring, and measuring the mixed solution A by using a hydrometertnAnd specific gravity values B of the reference solution at a plurality of different time pointstnAccording to 8 (A)tn-Btn) P is the mass percentage of the particles with corresponding particle sizes;
wherein P is the sieving rate of particles with a 0.08mm screen.
8. The method of claim 1, further comprising the step of optimizing the test soil sample based on the evaluation, the step of optimizing comprising:
determining the components to be adjusted according to the comparison result;
measuring the grading curve of the standby raw material corresponding to the component to be adjusted;
and calculating the use amount of the components needing to be adjusted, and fitting the grading curve of the raw materials to be used and the grading curve of the soil sample to be measured to obtain the grading curve of the target soil sample, so that the grading curve of the target soil sample falls into the optimal grading interval or the limit optimal grading interval.
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