CN1278519A - Cement for foundation treatment and its preparation - Google Patents

Abstract

The cement for ground treatment is made up by using granulated blast-furnace water-quenched slag as main component, using cement clinker, vessel slag, lime and anhydrite, etc. as excitation agent and using flyash as grinding aid through the processes of mixing according to a certain proportion and grinding to a certain fineness. It is applicable to reinforcement of clay with high water content, and the clay reinforced by using said cement possesses high unconfined compressive strength, triaxial shear strength, modulus of deformation and low permeability coefficient and compression coefficient. Said invention is simple in production process, low in cost and easy to implement.

Description

Cement for foundation treatment and preparation method thereof

The invention relates to cement and a preparation method thereof, in particular to cement for foundation treatment and a preparation method thereof.

Clay is an ancient and common building material. However, due to its low strength and poor water stability, it is often necessary to add a curing agent in engineering to improve its strength and water stability. Common curing agents are portland cement and lime. For example, in the foundation of a building, a temporary enclosure structure of a deep foundation pit, and a dike of a hydraulic engineering, a common construction method such as a mixing pile and a powder-spraying pile is adopted to forcibly mix common cement and clay to form a column with a certain strength, so that the bearing capacity of the foundation and the soil-retaining and water-retaining performance of the enclosure structure and the dike are improved. In another example, lime is often added to the base course and sub-base course of road engineering to improve the bearing capacity of the soil roadbed.

However, the strength of clay reinforced by the existing curing agents such as ordinary cement, lime and the like is low, particularly in areas with more rivers, lakes, coasts and creeks, the water content of the clay is very high, and the effect of reinforcing the clay by the common curing agents is poor, so that a lot of engineering accidents are caused. If the settlement value of the residential building exceeds the allowable range, the residential building has uneven settlement, the foundation pit enclosure has danger and the like.

The existing scientific and technical data show that the strength of ordinary cement reinforced soil and lime reinforced soil can be improved by using sulfate additives such as gypsum, sodium sulfate and the like.

Chinese patent application publication CN1125702A proposes a lime-based soil curing agent, which is a mixture obtained by adding anhydrite, sodium sulfate and aluminum sulfate into quick lime and grinding the mixture. However, the curing agent is only suitable for curing soil with the water content of less than 25 percent, and the strength of the cured soil is only 60 percent higher than that of the soil cured by only quicklime. And is only slightly higher than the No. 325 slag cement with the same doping amount.

In the study on high-water-content clay curing agents (7/1998, 20, 4, 72), Liu Shunni et al suggested that when the water content of the soil is high (about 48%), 14% of gypsum and 3% of sodium sulfate are added to the cement, so that the compressive strength of the reinforced soil can be improved by 73.6%. However, the magnitude of its intensity is still limited; the consumption of cement in the curing agent is larger (83%), and the cost of the curing agent is higher; and the use of the admixture in the cement brings great difficulty to construction and easily causes inaccurate metering.

Therefore, a soil curing agent which is convenient to use, low in production cost, high in soil strengthening strength and suitable for curing soil with high water content is urgently needed.

The invention aims to provide cement for foundation treatment (hereinafter sometimes referred to as foundation cement) and a preparation method thereof. The foundation cement only contains a small amount of cement clinker, but can ensure that the reinforced soil has high unconfined compressive strength, triaxial shear strength, deformation modulus and the like, and low permeability coefficient and compression coefficient. The foundation cement is convenient to use, simple in production process, low in production cost and capable of using a large amount of industrial waste.

The cement for ground treatment of the present invention is composed of 70 to 92% by weight of granulated blast furnace water-quenched slag, 2 to 20% by weight of an alkali-activator and 6 to 20% by weight of a sulfate activator, based on the total weight of the ground cement.

The alkali activator is selected from cement clinker, portland cement, ordinary portland cement, converter steel slag, lime or a mixture thereof. The sulfate excitant is anhydrous gypsum which comprises fluorgypsum, natural anhydrite and anhydrous gypsum calcined at the temperature of 600-800 ℃. To further reduce costs, a small amount of fly ash may be used in place of part of the granulated blast furnace water granulated slag. In addition, the added fly ash also plays a role of a grinding aid.

The preparation method of the cement for foundation treatment comprises the steps of mixing the components according to the proportion, and grinding the mixture until the specific surface area is 250-one sand 500 m²The dosage is one kilogram.

Therefore, the foundation cement of the invention contains more than 90% of industrial waste, has wide raw material sources, simple production process and obvious social and economic benefits, and the production cost of the foundation cement is reduced by more than 30% compared with that of common cement. Under the condition of the same mixing amount, the geotechnical performance index (such as unconfined compressive strength, triaxial shear strength, deformation modulus and the like) of the foundation cement reinforced soil is 425^#The soil engineering performance index of the common cement reinforced soil is 3-5 times that of the common cement reinforced soil, and the permeability coefficient and the compression coefficient of the clay reinforced by the foundation cement are lower than 425^#Permeability coefficient and compressibility coefficient of portland cement reinforced clay. The foundation cement of the present invention is suitable for reinforcing clay with different water content and property, especially high water content clay. In addition, the strength of the 9 wt% foundation cement reinforced soil can exceed 15 wt% 425^#The strength of the common cement reinforced soil is 32%, so that the foundation cement material is saved, and the engineering cost is further reduced.

The foundation cement of the present invention and the method for producing the same will be described in detail below.

The cement for foundation treatment of the invention takes granulated blast furnace water quenched slag as a main component, takes cement clinker, portland cement, ordinary portland cement, converter steel slag or lime as an alkaline excitant, takes anhydrous gypsum as a sulfate excitant, and can also be added with a small amount of fly ash as a grinding aid.

Granulation for use in the foundation cement of the inventionThe blast furnace water-quenched slag is in accordance with the regulation of superior products in GB/T203-₂O₃)／SiO₂Should be greater than 1.6.

The cement clinker adopted in the foundation cement comprises rotary kiln or vertical kiln cement clinker, wherein the content of free calcium oxide in the clinker is not more than 3 percent, and the content of magnesium oxide is not more than 5 percent. It is known that portland cement or ordinary portland cement contains 80-90% of cement clinker. Therefore, portland cement or ordinary portland cement can also be used in place of cement clinker. Portland cement or ordinary Portland cement should meet the regulations of GB 175-1992 Portland cement, ordinary Portland cement, the grade of cement is not lower than No. 425.

The converter steel slag used in the foundation cement of the invention is in accordance with the stipulation of YB/T022-1992 steel slag used in cement, and the grain size after magnetic separation and iron removal and crushing is less than 30 mm. The total content of free calcium oxide and calcium hydroxide is not more than 10%, and the content of magnesium oxide is not more than 10%.

The lime which can be used in the foundation cement of the invention comprises building quicklime or building slaked lime, and the lime meets the regulations of superior products in JC/T479 + 1992 building quicklime or JC/T481 + 1992 building slaked lime.

The sulfate excitant used in the foundation cement of the invention has larger dosage. If natural dihydrate gypsum is used, the dihydrate gypsum is dehydrated at high temperature in a ball mill in actual production, so that normal production is influenced. Therefore, anhydrous gypsum must be used in the foundation cement of the present invention. The anhydrous gypsum comprises fluorgypsum, natural anhydrite or 600-doped 800 ℃ calcined anhydrous gypsum, and the content of anhydrous calcium sulfate is not less than 80 percent according to the regulation of GB 5483-1996 Gypsum and anhydrite.

The fly ash which can be used in the foundation cement of the invention is in accordance with the regulation of class II ash of GB 1596&1991 fly ash used in cement and concrete.

The chemical compositions (% by weight) of the respective raw material components used in the foundation cement of the present invention are shown in Table 1

TABLE 1

Raw materials	SiO2	Al2O3	Fe2O3	CaO	MgO	SO3	FeO	fCaO+Ca(OH)2
									Blast furnace slag	30.08	14.74	1.30	39.92	9.10	0.26	-	-
Steel slag	13.50	-	9.24	39.20	5.80	-	16.90	7.62
									Fluorgypsum	3.37	0.25	0.35	35.70	0.17	51.00	-	-
600 ℃ and 800 ℃ calcination Calcined anhydrite	4.14	0.60	0.65	34.33	0.24	49.04	-	-
									Natural anhydrite	4.50	1.20	2.14	33.00	-	47.14
Fly ash	50.60	29.70	7.43	2.46	1.07	0.82	-	-
									Quick lime	0.02	-	-	94.50	0.02	0	-	-
Slaked lime	0.02	-	-	71.50	0.02	-	-	-
									Cement clinker	21.70	6.30	3.50	65.50	1.80	-	-	1.10
Portland cement	22.30	6.40	3.20	63.00	2.20	2.70	-	-
									Ordinary silicate Cement	22.50	6.50	3.40	62.50	2.40	2.70	-	-

The granulated blast furnace water-quenched slag is used in an amount of 70 to 92% by weight based on the total weight of the foundation cement of the present inventionAmounts, preferably in the range of 80 to 85% by weight. Granulated blast furnace water-quenched slag plays a major role in foundation cement, as long as Ca (OH) in soil is reinforced₂Concentration, SO₄ ^2－The concentration is enough to promote the slag to hydrate to generate ettringite and hydrated calcium silicate, and the more the slag is used, the higher the strength is.

The dosage of the alkali-activator is 2-20% of the total weight of the foundation cement. The preferred amount is 5-15%. The alkali activator can be cement clinker, portland cement, ordinary portland cement, converter steel slag, lime or their mixture.

The cement clinker is the most active alkali activator. It is generally used in an amount of 2 to 10% by weight, preferably 5 to 10% by weight. When the cement clinker is used alone as the alkaline excitant, if the dosage of the cement clinker is less than 2 percent by weight, the alkalinity of the reinforced soil is too low, and the slag hydration is influenced; if the amount of cement clinker used exceeds 10% by weight, the cost of the product increases and the effect of improving the strength is not significant. It is known that portland cement and ordinary portland cement contain 80 to 90% by weight of cement clinker. Therefore, portland cement or ordinary portland cement can also be used in place of cement clinker.

In order to reduce the cost, steel slag and lime can be used for replacing part of cement clinker or all of the cement clinker. The steel slag has low activity, and when used alone, the use amount of the steel slag is generally 10 to 20 weight percent. If the steel slag is used in an amount exceeding 20% by weight, the strength of the soil after reinforcement is reduced; if the consumption of the steel slag is lower than 10 percent, the alkalinity of the reinforced soil is too low, and the hydration of the slag is influenced. Lime has moderate activating activity and when used alone is used in an amount of 5-15% by weight. If it is used in an amount exceeding 15% by weight, the strength of the soil after reinforcement is lowered. If the amount of lime is too low, the hydration of the slag is also affected.

The anhydrite is used in an amount of 6 to 20% by weight, preferably 8 to 12% by weight, based on the total weight of the foundation cement of the present invention. If the amount of the anhydrite is less than 6% by weight, the strength of the soil after the reinforcement is lowered. If the amount of the anhydrite exceeds 20% by weight, the strength of the soil after the reinforcement is not remarkably improved.

The fly ash can replace part of granulated blast furnace water-quenched slag and has a grinding-assisting effect. The usage amount of the fly ash is 0-10%. If the amount of fly ash exceeds 10% by weight, the strength of the soil after reinforcement is lowered.

The production process of the foundation cement is simple, and the requirement on production equipment is low. The cement clinker, the natural anhydrite or the anhydrous gypsum calcined at the temperature of 800 ℃ are crushed to the grain diameter of less than 30 mm by using a conventional jaw crusher. The granulated blast furnace water-quenched slag and the converter steel slag are dried by a conventional rotary drum dryer, and the drying temperature is not more than 400 ℃, preferably 250-350 ℃, and most preferably 300 ℃. The moisture content after drying is controlled within 1.5 percent. The components are then weighed out according to the formulation of the foundation cement according to the invention with an electronic or mechanical weighing device, the metering error not exceeding 5% by weight. Finally, the components are added into a conventional ball mill or a column mill for grinding, so that the specific surface area of the mixture reaches 250-500 m²One kilogram, preferably 400-500 m²In kg. Thus obtained inventionThe base cement can be directly packaged and delivered from the factory after being inspected, and can be used for reinforcement by customersClay foundation.

The strength of the foundation cement is mainly from the action of the active substance in the slag as the trigger to generate hydration products, and the foundation cement reacts with the clay to generate the hydration products with poor crystallinity. The specific strength formation mechanism is as follows:

(1) active Al in granulated blast furnace water-quenched slag₂O₃Is excited by alkaline exciting agents such as cement clinker, steel slag, lime and the like to generate hydrated calcium aluminate, and the reaction formula is as follows:

activity of

The hydrated calcium aluminate is excited by sulfate of anhydrous gypsum to generate trisulfide hydrated calcium sulfoaluminate (ettringite), and the reaction formula is as follows:

the generation of a large amount of ettringite has important significance for improving the strength and the water stability of the reinforced soil. This is because the ettringite crystals contain a large amount of crystal water, and during the production process, the solid phase volume slightly expands to fill a large amount of pores in the clay, thereby reducing the porosity of the clay. In addition, the ettringite has a needle-column structure which is crossed with each other, and plays a role of framework support in the clay. Therefore, the generated ettringite can greatly improve the strength and the water stability of the reinforced soil. In clay with high water content, the filling and supporting effect of the ettringite is especially obvious for improving the strength of the reinforced soil. In addition, the ettringite is generated at a higher speed, so that the early strength of the reinforced soil is higher.

(2) Active SiO in granulated blast furnace water-quenched slag₂Under the excitation of alkaline agent, calcium silicate hydrate is continuously generated, and the reaction formula is as follows:

activity of

The calcium silicate hydrate acts as a cement in the clay, binding the loose soil particles together. With the continuous generation of calcium silicate hydrate, the calcium silicate hydrate and the ettringite act together to ensure that the strength of the reinforced soil is continuously increased.

(3) Al in clay₂O₃And is also subjected to alkali excitation and sulfate excitation to generate ettringite with poor crystallinity, and the reaction formula is the same as that in the step (1).

Due to Al in the clay₂O₃The activity of (a) is poor, the reaction is slow, the crystallinity of the generated ettringite is poor, and the strength is low.

(4) SiO in clay₂And alkali excitation is carried out to generate hydrated calcium silicate with poor crystallinity, and the reaction formula is the same as (2).

Due to SiO in the clay₂The reaction is slow, and the produced hydrated calcium silicate has poor crystallinity and low strength.

The strength of the ordinary cement reinforced soil is mainly derived from hydrated calcium silicate and hydrated calcium aluminate generated by cement hydration and a hydration product with poor crystallinity generated by the reaction of the ordinary cement and clay. Because the gypsum in the ordinary cement containsThe amount is low, most of ettringite is converted into single-sulfur hydrated calcium sulphoaluminate, and the amount of ettringite is small. The strength of lime-stabilized soil is mainly derived from Ca (OH) in lime₂With SiO in clay₂、Al₂O₃Slowly react to generate a hydration product with poor crystallinity. Therefore, the strength of lime-reinforced soil is lower than that of ordinary cement-reinforced soil. As described above, the strength of the ordinary cement-stabilized soil and the lime-stabilized soil can be improved by using the admixture such as gypsum and sodium sulfate, because the admixture promotes the formation of ettringite. However, the foundation cement of the present invention contains a large amount of active Al₂O₃The quantity of the ettringite generated under the action of a proper excitant is far more than that of the ordinary cement reinforced soil and the ordinary cement doped with the gypsum reinforced soil.

In conclusion, the foundation cement has proper raw materials and compositions, and can form a large amount of ettringite for filling and calcium silicate hydrate for cementing in the clay, so that the foundation cement reinforced soil has various remarkable geotechnical properties. In addition, ground waterThe mud can reach the national standard 425^#The technical requirements of slag cement can also be applied to other foundation treatment technologies (such as compaction grouting and the like).

The present invention will be further described with reference to examples. It is to be understood that these examples are illustrative only and are not intended to limit the scope of the present invention.

Examples

The raw materials used were pretreated as follows:

1. crushing: A150X 250 mm PE-150 jaw crusher is used to crush cement clinker (purchased from Shanghai red flag cement factory), natural anhydrite (purchased from Nanjing anhydrite factory) and 600-800 ℃ calcined anhydrite (purchased from Shanghai red flag cement factory) respectively to make their grain diameters smaller than 30 mm for later use.

2. Drying: granulated blast furnace water quenched slag (purchased from Bao Steel) and steel slag (purchased from Shanghai Changchang New Steel slag) are respectivelydried by a rotary drum dryer (purchased from a normal-maturing building material machinery factory) with the diameter of 1.2 multiplied by 10 meters within the temperature range of 250 ℃ and 350 ℃ to ensure that the water content is lower than 1.5 percent for standby.

Example 1

2 parts by weight of pretreated cement clinker, 88 parts by weight of pretreated granulated blast furnace granulated slag and 10 parts by weight of fluorogypsum (purchased from Shanghai electrochemical plant) were charged into a 1.5X 5.7 m-diameter ball mill (purchased from Nanchang mining machinery plant), and mixed and ground to a specific surface area (measured by GB 8074-1987 (Bosch method)) of 400 m²Per kilogram, make formula A1 foundation cement.

Example 2

A foundation cement of formulation A2 was prepared in the same manner as in example 1, using 4 parts by weight of ordinary portland cement (available from Shanghai red-flag cement plant), 86 parts by weight of the pretreated granulated blast furnace water-granulated slag, and 10 parts by weight of fluorogypsum.

Example 3

A foundation cement of formulation A3 was prepared in the same manner as in example 1, using 3 parts by weight of portland cement (available from Shanghai red-flag cement plant), 87 parts by weight of pretreated granulated blast furnace water-granulated slag, and 10 parts by weight of fluorogypsum.

Example 4

A foundation cement of formulation A4 was prepared in the same manner as in example 1, using 4 parts by weight of the pretreated cement clinker, 90 parts by weight of the pretreated granulated blast furnace granulated slag, and 6 parts by weight of fluorogypsum.

Example 5

A foundation cementof formulation A5 was prepared in the same manner as in example 1, using 10 parts by weight of the pretreated cement clinker, 70 parts by weight of the pretreated granulated blast furnace granulated slag and 20 parts by weight of fluorogypsum.

Example 6

A foundation cement of formulation A6 was prepared in the same manner as in example 1, using 5 parts by weight of the pretreated cement clinker, 85 parts by weight of the pretreated granulated blast furnace granulated slag and 10 parts by weight of fluorogypsum.

Example 7

A foundation cement of formulation A7 was prepared in the same manner as in example 1 using 5 parts by weight of the pretreated cement clinker, 84 parts by weight of the pretreated granulated blast furnace granulated slag and 11 parts by weight of the pretreated 600-800 ℃ calcined anhydrite.

Example 8

A foundation cement of formulation A8 was prepared in the same manner as in example 1, using 5 parts by weight of the pretreated cement clinker, 83 parts by weight of the pretreated granulated blast furnace granulated slag and 12 parts by weight of the pretreated natural anhydrite.

Example 9

A foundation cement of formulation A9 was prepared in the same manner as in example 1, using 10 parts by weight of the pretreated cement clinker, 80 parts by weight of the pretreated granulated blast furnace granulated slag and 10 parts by weight of fluorogypsum.

Example 10

A foundation cement of formulation A10 was prepared in the same manner as in example 1, using 20 parts by weight of the pretreated steel slag, 70 parts by weight of the pretreated granulated blast furnace granulated slag, and 10 parts by weight of fluorogypsum.

Example 11

A foundation cement of formulation a11 was prepared in the same manner as in example 1, using 10 parts by weight of quicklime (available from shanghai peacpu lime plant), 80 parts by weight of pretreated granulated blast furnace granulated slag, and 10 parts by weight of fluorogypsum.

Example 12

A foundation cement of formulation a12 was prepared in the same manner as in example 1, using 15 parts by weight of slaked lime (available from shanghai peacpu lime plant), 75 parts by weight of the pretreated granulated blast furnace water-quenched slag, and 10 parts by weight of fluorogypsum.

Example 13

A foundation cement of formulation A13 was prepared in the same manner as in example 1, using 2 parts by weight of the pretreated cement clinker, 75 parts by weight of the pretreated granulated blast furnace granulated slag, 13 parts by weight of the pretreated steel slag and 10 parts by weight of fluorogypsum.

Example 14

A foundation cement of formulation A14 was prepared in the same manner as in example 1 from 10 parts by weight of the pretreated steel slag, 5 parts by weight of quicklime, 75 parts by weight of the pretreated granulated blast furnace granulated slag and 10 parts by weight of fluorogypsum.

Example 15

A foundation cement of formulation A15 was prepared in the same manner as in example 1, using 10 parts by weight of the pretreated cement clinker, 70 parts by weight of the pretreated granulated blast furnace granulated slag, 10 parts by weight of fly ash and 10 parts by weight of fluorogypsum.

Example 16 and comparative example A

This example is a method of reinforcing soil by usingthe ground cements A1-15 of the present invention prepared in examples 1-15, respectivelyUnconfined compressive strength test, comparative example A for 425^#Ordinary cement is subjected to confined soil unconfined compressive strength test. The clay used was a silty clay with a water content of 45%. Various ground cements in clay and 425^#The mixing amount of the common cement is 13 percent by weight, and the water cement ratio is 0.45. Firstly, preparing a reinforced soil test piece according to the following steps: 1. preparing a soil sample: selecting three kinds of natural soil, namely silt silty clay and brown yellowSilty clay and sandy silty soil. They are all drilled on site to take out soil samples, dried at the temperature of 105 ℃ and 120 ℃, crushed and sieved for standby. Wherein, the brown yellow powdery clay is sieved by a2 mm sieve, and the other two kinds of clay are sieved by a1 mm sieve. The moisture content of the dried soil was taken to be 3%. 2. The test piece of the test mold without lateral limit compressive strength and triaxial shear strength adopts the inner wall size as follows: split test molds with diameter Φ = 39.1 mm and height h =80 mm were sampled. 3. The formula of the test piece formula cement mixing amount is as follows: $W_c=\frac{1+w}{1+w_0}{a}_w\·W_0$ adding water: $W_w=\left(\frac{w-w_0}{1+w}{\mathrm{\μa}}_w\right)\frac{1+w}{1+w_0}{W}_0$ in the formula: w₀Weight of dried soil (kg))；

W_cGround cement or 425^#Weight of portland cement (kg);

W_w-water weight (kg);

w-natural moisture content of soil;

w₀-moisture content of the drying soil;

a_wground cement or 425^#The mixing ratio of the ordinary cement;

mu-water-cement ratio. 4. Cementing the foundation with cement or 425^#Placing the common cement and various soil samples in a stirring pot, manually stirring the mixture uniformly by using a stirring shovel, and then adding water according to the amount to stir the mixture uniformly by using a cement mortar stirrer. Stirring was carried out for 10 minutes from the addition of water. 5. The tamping method adopts a manual tamping method to tamp, the soil sample is loaded into a test mould in three layers, and three-axis tamping hammers are used to tamp until no air bubbles appear on the surface. 6. After the maintenance and tamping of the test piece are finished, the test piece is maintained for one day under natural conditions, and then is maintained in water for one day, and then is demoulded, weighed and wovenMaintaining in water until the age is over; the curing temperature is 20 ℃ +/-3 ℃.

Secondly, testing unconfined compressive strength

When the reinforced soil test piece reaches various ages, the unconfined compressive strength test of the reinforced soil is carried out according to GBJ 123-1980 geotechnical test method standard. The test procedure was as follows:

the strain control type unconfined pressure instrument is adopted, a test piece is loaded through deformation of a stress ring, a motor drives a gearbox to control axial strain of the test piece to be 0.5% per minute, namely, a stand rises by 0.4 mm per minute, so that the test is finished in about 20 minutes, the axial pressure, namely, the deformation of the stress ring is recorded according to 0.1% strain, namely, 0.08 mm interval in the test, and the test is stopped until the test is destroyed. Then according to the formula:

f_cu=P／A

f_cucompressive Strength

Magnitude of P-pressure

Bottom area of test piece when A-corresponding size corresponds to pressure

And solving the corresponding strength of each recorded reading, finding out the maximum value as the unconfined compressive strength value of the test piece, and drawing a stress-strain relation graph according to the recorded reading. Each set was subjected to three unconfined compressive strength tests, and the arithmetic mean value was taken as the unconfined compressive strength value for that set of tests. The unconfined compressive strength was measured in MPa and the results are given in Table 2.

TABLE 2

Recipe number	7 days strength	14 days strength	28 days strength	90 days strength
					A1	0．938	2．144	2．682	3．259
A2	0．910	1．939	2．415	3．014
					A3	0．924	2．050	2．515	3．171
A4	0．769	1．650	2．551	3．059
					A5	1．255	1．764	2．227	3．029
A6	1．300	2．189	2．726	3．612
					A7	1．292	2．150	2．690	3．453
A8	1．281	2．147	2．683	3．433
					A9	1．394	2．218	2．811	3．778
A10	1．281	1．835	2．303	3．068
					A11	1．342	2．090	2．584	3．461
A12	1．292	1．890	2．494	3．251
					A13	1．382	2．002	2．720	3．524
A14	1．357	1．910	2．619	3．414
					A15	1．296	1．884	2．466	3．109
425#Ordinary cement	0．509	0．753	1．073	1．360

As can be seen from the data in the above table, among the alkali activators, the cement clinker has the best effect, and the exciting effects of portland cement, ordinary portland cement, quicklime, slaked lime and steel slag are decreased in sequence. When a plurality of alkaline excitants are mixed for use, the effect is better. Among the sulfate excitants, the effect of the fluorgypsum is best, and the excitation effects of the anhydrous gypsum calcined at the temperature of 600-800 ℃ and the natural anhydrite are gradually reduced. In the formula 9, when the dosage of the cement clinker is 10 percent by weight, the dosage of the fluorgypsum is 10 percent by weight and the dosage of the slag is 80 percent, the dosage of the two excitants just fully hydrate the slag, and the dosage of the slag is relatively higher, at the moment, the foundation cement reinforced soil has strong strengthThe highest degree, and far exceeding 425 in comparative example A^#The strength of the ordinary cement reinforced soil.

Example 17

Granulated blast furnace granulated slag, cement clinker and fluorgypsum were mixed and ground to different fineness according to formulation a9 in example 9, and then the obtained foundation cement of different fineness was incorporated into clay to test the unconfined compressive strength of the stabilized soil. The test conditions were the same as in example 16. The results are shown in Table 3.

TABLE 3

Formulation of	Fineness of fineness	Specific surface area Rice and its production process2Kg/kg	7 days strength MPa	14 days strength MPa	28 days strength Mpa	90 days strength MPa
							A9	B1	250	0．791	1．266	1．869	1．964
A9	B2	300	1．082	1．752	2．323	2．621
							A9	B3	400	1．382	2．218	2．811	3．512
A9	B4	500	1．808	2．739	3．691	4．537
							A9	B5	150	0．680	1．160	1．584	1．904
A9	B6	600	2．075	3．040	3．758	4．742

As can be seen from the above table, the greater the specific surface area of the foundation cement, the greater the strength of the reinforced soil. The specific surface area can be generally within the range of 250-500 m²One kilogram, the optimal range is 400-500 meters²In kg. If the specific surface area is less than 250 m²One kilogram, the unconfined compressive strength of the reinforced soil is lower; if the specific surface area exceeds 500 m²The strength of the steel is improved at 7 days and 14 days in each kilogram, the strength is improved in a smaller range at 28 days and 90 days, and the larger the specific surface area is, the higher the production cost is.

Example 18

The foundation cement with fineness B4 and the portland cement No. 425 prepared according to the formula A9 in example 17 were respectively stirred and blended into three typical clays of silty clay, brownish yellow silty clay and sandy clay, the blending amount was 13%, and the water cement ratio was 0.45. And testing the unconfined compressive strength of the reinforced soil. The test conditions were the same as in example 16. The results are shown in Table 4.

TABLE 4

Categories	Foundation cement reinforced soil				425#Ordinary cement reinforced soil
									Property of soil	Silty powder Clay clay		Brown and yellow colour powder Clay clay	Sand stick Soil for soil	Silt paste Soil for soil			Brown and yellow colour powder Clay clay	Sandy clay
Water content	45％	55％	35％	35％	45％		55％	35％											35％
									3 days	1．022	0．830	1．451	1．976	0．328		0．204	0．430	0．372
7 days	1．808	1．067	2．228	2．788	0．509		0．293	0．692											0．547
									14 days	2．739	1．654	3．365	4．012	0．753		0．522	0．949	1．099
28 days	3．691	2．265	4．233	5．230	1．073		0．685	1．377											1．479
									60 days	4．024	2．710	4．606	5．473	1．360		0．851	1．541	1．540
90 days	4．537	3．241	5．013	5．716	1．172		0．896	1．590											1．714

As can be seen from the above table, the unconfined compressive strength of the foundation cement-reinforced soil is 425 for different soil qualities^#The unconfined compressive strength of the common cement reinforced soil is 3-5 times. In addition, the unconfined compressive strength ratio 425 of the silt silty clay-stabilized soil with high water content (55%) of the foundation cement^#The low water content (35%) brown yellow powdery clay or sandy clay reinforced soil of the common cement has high unconfined compressive strength. This shows that the reinforcement effect of the foundation cement of the invention is much better than that of the common cement in the areas with more rivers, lakes, rivers, coasts and creeks.

Example 19

The silty clay with the water content of 45 percent is mixed with the foundation cement with the fineness of B4 prepared according to the formula A9 and 425^#Ordinary cement with water-cement ratio of 0.45. The unconfined compressive strength (MPa) of the reinforced soil was measured at 28 days and 90 days under the same test conditions as in example 16, and the results are shown in Table 5.

TABLE 5

Water cement ratio mu = 0.45	Silty clay (45%) reinforced soil unconfined compressive strength (28 days) (MPa)
					Amount of addition of aw	9％	11％	13％	15％
Foundation cement	1．157	1．793	3．691	3．684
					425#Ordinary cement	0．476	0．755	1．073	1．196
Water cement ratio mu = 0.45	Silty clay (45%) reinforced soil unconfined compressive strength (90 days) (MPa)
					Amount of addition of aw	9％	11％	13％	15％
Foundation cement	2．236	2．551	4．024	5．386
					425#Ordinary cement	0．745	1．142	1．172	1．689

As can be seen from the above table, the unconfined compressive strength of the foundation cement reinforced soil can greatly exceed 42 under different mixing amounts5^#Unconfined compressive strength of ordinary cement-reinforced soil, and strength of 9 wt% foundation cement-reinforced soil exceeds 425 of 15 wt%^#The strength of the ordinary cement reinforced soil is 32 percent. This shows that the cost of the foundation cement is low, the material consumption is also saved, and the construction cost can be further reduced.

Example 20

The foundation cement with fineness of B4 prepared according to the formula A9 and 425 ground cement are mixed into three typical clays, namely silty clay, brown yellow silty clay and sandy clay^#The admixture of the ordinary cement is 13 percent, and the water cement ratio is 0.45. A reinforcing soil test piece was prepared in the same manner as in example 16, and then GBJ 123-The triaxial shear strength of reinforced soil of different ages is tested in geotechnical test method standard. The test procedure was as follows:

the test equipment is the same with no confined compressive strength test equipment, adopts not concreting not drainage test (UU), and experimental confined pressure divides the level four: 14 days of age: 50 kPa 100 kPa 200 kPa 300 kPa 28-day age: 100 kPa 200 kPa 400 kPa 500 kPa

The recording, reading and drawing are the same as the unconfined compressive strength test. And drawing a Moire stress circle and an envelope curve thereof according to the confining pressure and the corresponding maximum principal stress of each group of 4 test pieces, and according to Coulomb's law:

τ＝σtgψ_u+c_u

t-shear strength

Sigma-stress

ψ_uInternal angle of friction

c_uCohesion force

Determining the shear strength index psi_uAnd c_u. The results are shown in Table 6.

TABLE 6

Age of age	Curing agent	Triaxial shear strength Degree (MPa)	Silty powder Clay (55%)	Silty powder Clay (45%)	Brown yellow powder Clay (35%)	Sandy clay (35％)
							14 days	Foundation cement	cu	1．050	1．120	1．500	1．800
ψu	1．5°	1°	2°	1°
					425#General purpose Cement	cu			0．180	0．290	0．500	0．550
ψu	1°	0．5°	1°	0．5°
						28 days		Foundation cement	cu	1．100	1．200	2．150	2．300
ψu	1°	1°	3°	1°
					425#General purpose Cement		cu		0．180	0．300	0．650	0．700
ψu	0．5°	0．5°	1°	0．5°
							90 days	Foundation cement	cu	1．200	1．400	2．500	2．800
ψu	1°	2°	3°	3°
					425#General purpose Cement	cu			0．210	0．320	0．800	0．800
ψu	0．5°	1°	1°	1°

As can be seen from the above table, the internal friction angle psi of the two types of stabilized soils_uAll approach to 1-2 degrees, and the cohesive force c of the foundation cement reinforced soil_uIs 425^#Cohesion of ordinary cement-reinforced soil c_u3-5 times of the total weight of the product. 425^#The low cohesion of ordinary cement to silt silty clay with high water content is an important cause of many engineering accidentsThus, the method is simple and easy to operate. The cohesive force of the silt silty clay reinforced soil of the foundation cement is not much different from that of the brown yellow silty clay or sandy silty clay reinforced soil. Moreover, the cohesive force of the silty clay (55%) of the foundation cement-reinforced soil is more than 425^#The common cement brown yellow powdery clay reinforces the cohesive force of the soil or the sandy powdery soil reinforces the cohesive force of the soil. Therefore, the foundation cement can be widely used for high water contentSoil layer with poor quality and geological condition, the effect ratio is 425^#Ordinary cement is much more ideal.

Example 21

The foundation cement with fineness B4 prepared according to the formula A9 and 425 ground cement are stirred and mixed into three typical clays, namely silty clay, brown yellow silty clay and sandy clay^#Ordinary cement with water-cement ratio of 0.45. A stabilized soil test piece was prepared in a similar manner to example 16, except that the inner wall dimensions were: and (3) manually leveling and vibrating a ring cutter test piece die with the diameter phi= 61.8 mm and the height h =20 mm, leveling the test piece by using a knife, molding, numbering, directly putting into water, maintaining until the age is finished, and weighing. The permeability coefficients of the reinforced soil with different ages and different mixing amounts are tested according to GBJ 123-1980 geotechnical test method standard. The results are shown in Table 7.

TABLE 7

Property of soil		Curing agent	Mixing amount		Permeability coefficient of consolidated soil (cm/sec)
								7 days	28 days	90 days
					Silt powder Clayey clay (55%)		Foundation cement				13％		9．83×10－6	8．78×10－8	1．98×10－8
425#Ordinary cement	13％		1．14×10－6	3．25×10－7				6．54×10－8
							Silt powder Clayey clay (45%)		Foundation cement	13％		1．25×10－６	2．99×10－7	3．68×10－8
425#Ordinary cement	13％		2．74×10－7	1．72×10－7	5．20×10－8
						Brown and yellow colour powder Clayey clay (35%)			Foundation cement	13％		4．77×10－8	1．11×10－8	5．06×10－9
425#Ordinary cement	13％		3．10×10－7	2．50×10－7	3．70×10－8
								Sand Quality of food Powder Soil for soil (35％)		Foundation cement	11％		8．95×10－7	4．91×10－7	6．03×10－8
Foundation cement	13％		5．17×10－8	4．69×10－8	9．40×10－9
						425#Ordinary cement	13％			3．93×10－6	1．62×10－7	5．26×10－8
Foundation cement	15％		1．26×10－7	5．39×10－8	6．98×10－9
						425#Ordinary cement	15％			2．44 × 10－7	6．40×10－8	4．44×10－8

As can be seen from the above table, the 28-day permeability coefficient of the foundation cement-reinforced soil is substantially maintained at 10^－7－10^－8Of the order of magnitude, even up to 10^－9The permeability coefficient is basically stabilized at 10 in 90 days^－8－10^－9An order of magnitude. And the permeability coefficient of the foundation cement is lower than 425 under the same other conditions^#Permeability coefficient of ordinary cement reinforced soil. Description of the inventionThe foundation cement is used for a building envelope and a dike, and has ideal impermeability.

Example 22

The foundation cement with fineness of B4 prepared according to the formula A9 and 425 ground cement are mixed into three typical clays, namely silty clay, brown yellow silty clay and sandy clay^#Ordinary cement with water-cement ratio of 0.45 and mixing amount of a_wAnd = 13%. When the unconfined compressive strength is tested, the ratio of stress to strain when the vertical stress reaches 50% unconfined compressive strength is called the deformation modulus E₅₀. Testing deformation modulus E of reinforced soil with different ages and different water contents₅₀The results are shown in Table 8.

TABLE 8

Categories	Foundation cement reinforced soil E50(MPa)				425 # Portland cement reinforced soil E50(MPa)
									Property of soil	Silt paste Soil for soil		Brown and yellow colour powder Clay clay	Sand stick Soil for soil	Silt paste Soil for soil			Brown and yellow colour powder Clay clay	Sandy clay
Water content	45％	55％	35％	35％	45％		55％	35％											35％
									3 days	75．39	100．19	195．00	126．33	28．35		31．98	72．49	31．33
7 days	90．44	104．43	288．39	151．71	81．15		42．72	84．28											69．92
									14 days	220．88	173．19	331．64	311．48	94．01		67．84	107．25	132．49
28 days	285．88	184．99	352．97	376．13	130．84		77．19	114．05											189．86
									60 days	369．20	242．77	442．35	488．98	142．07		109．76	119．10	239．28
90 days	493．44	278．25	489．85	672．48	191．24		171．83	155．40											286．07

As can be seen from the above table, the deformation modulus of the foundation cement-stabilized soil is 425 under the same other conditions^#The deformation modulus of the common cement is 3-5 times. This indicates that the foundation cement-reinforced soil has a high rigidity and can generate a large stress when the strain is small. And the influence of the water content of the clay on the deformation modulus of the foundation cement reinforced soil is more favorable than that of 425^#The influence of the ordinary cement is small.

Example 23

The foundation cement with fineness B4 prepared according to the formula A9 and 425 ground cement are stirred and mixed into three typical clays, namely silty clay, brown yellow silty clay and sandy clay^#Ordinary cement with water-cement ratio of 0.45 and mixing amount of a_wAnd = 13%. Test pieces of stabilized soil were prepared in the same manner as in example 21, and compression tests were conducted thereon in accordance with GBJ 123-.

Compression tests were performed on a consolidator, all tests using graded loading: the pressure of the liquid at 50 kPa, 100 kPa,200 kPa, 400 kPa, 600 kPa, 800 kPa, wherein 50 kPa, 100 kPa, 200 kPa after sequentially adding each after solidifying for two hours, recording the count, and then adding the next stage load; two hours after 400 kPa loading and 24 hours after allowing the consolidation to stabilize, 600 kPa and 800 kPa were then added in sequence, the two stages being separated by two hours. From the recorded readings, calculating the correspondingPore ratio e of_iAnd a load P_iThereby calculating a compression coefficient a_1－2、a_2－4、a_4－6、a_6－8. And taking the arithmetic mean value of each group of two test pieces as a result. The compression coefficient has a measurement unit of MPa^－1. The results are shown in Table 9.

TABLE 9

Categories	Age of age	Compression Coefficient of performance	Silt paste Soil (45%)	Silt silty clay (55％)	Brown yellow powder Soil (35%)	Sandy silt (35) ％)
							Ground Base of Water (W) Mud Adding Fixing device Soil for soil	28 Sky	a1－2 a2－4 a4－6 a6－8	0．074 0．057 0．019 0．024	0．087 0．063 0．022 0．033	0．062 0．048 0．026 0．022	0．067 0．044 0．018 0．020
90 Sky	a1－2 a2－4 a4－6 a6－8	0．074 0．043 0．021 0．020	0．064 0．035 0．032 0．031	0．087 0．043 0．020 0．019	0．067 0．042 0．020 0．032
						425# General purpose Tong (Chinese character of 'tong') Water (W) Mud Adding Fixing device Soil for soil		28 Sky	a1－2 a2－4 a4－6 a6－8	0．065 0．050 0．060 0．053	0．190 0．193 0．193 0．187	0．055 0．039 0．017 0．016	0．060 0．043 0．017 0．018
90 Sky	a1－2 a2－4 a4－6 a6－8	0．070 0．044 0．025 0．029	0．070 0．105 0．238 0．128	0．058 0．039 0．019 0．020	0．130 0．059 0．035 0．033

Compression factor a_1－2The axial load of the reinforced soil is expressed by 1.0 kg/cm²Increased to 2.0 kg/cm²Rate of change of void ratio with load, a_2－4、a_4－6、a_6－8And so on. The smaller the compression factor, the more difficult the consolidated soil is to compress, and the better the compression performance. As can be seen from the above table, the compression factor of the foundation cement-stabilized soil is less than 425^#The compression coefficient of the ordinary cement reinforced soil. In clay with high water content, the difference between the two is more obvious. For silty clay, the compression factor of a lower moisture (45%) ground cement-stabilized soil is 10-20% less than that of a higher moisture (55%) stabilized soil, and 425^#60-70 portions of ordinary cement reinforced soil% of the total weight of the composition. Therefore, the common cement cannot overcome the defects of sudden strength reduction and sudden deformation rise when the water content of the soil layer is higher in strength and deformation, and the foundation cement just makes up the defects. In addition, for different soil properties, the compression coefficients of the foundation cement reinforced soil are not greatly different, and the deformation change rules of various soil property reinforced soil are relatively close along with the increase of the load stage number. This indicates that the foundation cement is relatively stableThe fixed cementing material is very effective for controlling the settlement of the building.

Example 24

The ground cement with the fineness of B4 and 425 prepared according to the formula A9 are prepared according to GB 177-1985 Cement mortar Strength testing method^#The portland cement was tested and the results are listed in table 10. 425 in GB 1344-1992 Portland slag Cement^#The specifications of slag cement are also shown in Table 10.

Watch 10

Inspection item	Fineness (80 μm) Sieve allowance)	Initial setting Time of day	Final setting Time of day	Stabilization of Property of (2)	Flexural strength (MPa)			Compressive strength (MPa)			Standard thick Degree (%)
												3 days	7 days	28 days	3 days	7 days	28 days
					Foundation cement	1.0	2∶57	5∶33	Qualified	3.2								7.8	9.3	13.0	32.4	45.4	24.8
425#Ordinary cement	5.5	2∶33	4∶23	Qualified							5.1	-	8.1	24.9	-	57.8	25.5
					425#Slag cement Technical requirements of	≤10.0	Am not early In 45 minutes Clock (CN)	Must not be late At 10 Hour(s)	Must be provided with Qualified	-								4.0	6.5	-	21.0	42.5	-

As can be seen from the above table, the foundation cement can reach the national standard 425^#The technical requirements of slag cement. The foundation cement can also be applied to other foundation cement technologies (such as compaction grouting and the like). In addition, the 28-day flexural strength of the foundation cement mortar is higher than 425^#The breaking strength of the common cement mortar; the flexural strength of the cement mortar for 3 days, the compressive strength of the cement mortar for 3 days and 28 days and the foundation cement are all lower than 425^#And (4) ordinary cement. This indicates that the effect of the foundation cement in cementing the clay is better than that of the cemented sand.

In summary, various soils reinforced with the foundation cement of the present invention have much higher unconfined compressive strength, triaxial shear strength, deformation modulus, and much lower permeability and compressibility than ordinary cement.

Claims (13)

1. A cement for ground treatment, characterized in that it consists of 70-92% by weight of granulated blast furnace water-quenched slag, 2-20% by weight of an alkali-activator and 6-20% by weight of a sulfate activator, based on the total weight of the cement.

2. The cement for foundation treatment as claimed in claim 1, wherein the granulated blast furnace water granulated slag is contained in an amount of 80 to 85% by weight based on the total weight.

3. The cement for foundation treatment as claimed in claim 1, wherein fly ash is used in place of 0 to 10% by weight of the granulated blast furnace granulated slag.

4. The cement for ground treatment according to claim 1, wherein the alkali-activator is selected from the group consisting of cement clinker, portland cement, ordinary portland cement, converter steel slag, lime, and a mixture thereof.

5. A cement for ground treatment according to claim 1 or 4, wherein said alkali-activator is cement clinker and is contained in an amount of 2 to 10% by weight.

6. The cement for ground treatment according to claim 1 or 4, wherein the alkali-activator is converter slag and is contained in an amount of 10 to 20% by weight.

7. A cement for ground treatment according to claim 1 or 4, wherein the alkali-activator is lime in an amount of 5 to 15% by weight.

8. The cement for foundation treatment as set forth in claim 1, wherein the sulfate salt-activating agent is contained in an amount of 8 to 12% by weight.

9. A cement for ground treatment according to claim 1 or 8, wherein the sulfate salt-exciting agent is anhydrite.

10. The cement for foundation treatment as claimed in claim 9, wherein the anhydrous gypsum is selected from the group consisting of fluorogypsum, natural anhydrite and anhydrous gypsum calcined at 800 ℃ of 600 ℃.

11. The cement for foundation treatment as set forth in claim 10, wherein said anhydrite is fluorogypsum.

12. The method for preparing cement for foundation treatment as claimed in claim 1, wherein the components are mixed in the ratio and ground to a specific surface area of 250-500 m²In kg.

13. The method for preparing cement for foundation treatment as claimed in claim 12, wherein the components are mixed in the ratio and ground to a specific surface area of 400-500 m²In kg.