CN113433032B - Cement concrete mixture pressure expansion degree variation test and evaluation method - Google Patents
Cement concrete mixture pressure expansion degree variation test and evaluation method Download PDFInfo
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- 239000000203 mixture Substances 0.000 title claims abstract description 143
- 239000004568 cement Substances 0.000 title claims abstract description 134
- 238000010998 test method Methods 0.000 title claims abstract description 10
- 238000011156 evaluation Methods 0.000 title description 11
- 238000005086 pumping Methods 0.000 claims abstract description 52
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000001514 detection method Methods 0.000 claims abstract description 22
- 230000009471 action Effects 0.000 claims abstract description 7
- 238000004364 calculation method Methods 0.000 claims abstract description 6
- 230000006835 compression Effects 0.000 claims abstract 2
- 238000007906 compression Methods 0.000 claims abstract 2
- 238000012669 compression test Methods 0.000 claims abstract 2
- 238000012360 testing method Methods 0.000 claims description 23
- 230000000740 bleeding effect Effects 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 229910000831 Steel Inorganic materials 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 9
- 239000010959 steel Substances 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 229920001971 elastomer Polymers 0.000 claims description 4
- 238000012216 screening Methods 0.000 claims description 3
- 238000010276 construction Methods 0.000 abstract description 36
- 238000004445 quantitative analysis Methods 0.000 abstract description 3
- 238000010521 absorption reaction Methods 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000004576 sand Substances 0.000 description 4
- 239000004575 stone Substances 0.000 description 3
- 238000011835 investigation Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 239000010438 granite Substances 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 230000002522 swelling effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention relates to a cement concrete mixture pressure expansion degree variation test method, which comprises the following steps: (1) Determination of expansion k of Cement concrete mixture by slump cone 0 . (2) Performing a compression test on the same batch of cement concrete mixture obtained in the step (1), and measuring the expansion degree k of the cement concrete mixture by taking the cement concrete mixture after compression as a detection object m And k is m And said k 0 The detection time interval of (2) is not more than 10min. (3) According to k 1 ＝δ k ×k m The relation of (2) will be k m Converted to k 1 . (4) Calculation of k 0 And k 1 The difference value is obtained to obtain the pressure expansion degree loss value delta k of the cement concrete mixture, namely delta k=k 0 －k 1 The greater the Δk value, the greater the flowability loss of the corresponding cement concrete mixture in pumping action, the worse it can be pumped. The method of the invention realizes the detection and quantitative analysis of the pumping pressure expansion degree loss value of the cement concrete mixture before construction.
Description
Technical Field
The invention relates to the technical field of cement concrete mixture fluidity test, in particular to a cement concrete mixture pressure expansion degree variation test and evaluation method.
Background
The information disclosed in the background of the invention is only for enhancement of understanding of the general background of the invention and is not necessarily to be taken as an admission or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.
The expansion degree is a main technical index for representing the fluidity of the cement concrete mixture, and the larger the expansion degree is, the larger the corresponding fluidity is. The pumping construction is to carry cement concrete mixture to the up end of the structure through the concrete delivery pump and the pump pipe for pouring construction, the fluidity is the main property for representing the difficulty of pumping construction of the cement concrete mixture, the higher the expansion degree is, the higher the fluidity is, the easier the corresponding cement concrete mixture is for pumping pouring construction, otherwise, the lower the expansion degree is, the lower the fluidity is, the more unfavorable the pumping pouring construction is, and even the pump pipe is blocked and the pouring construction cannot be performed. The practice finds that: the fluidity of cement concrete mixtures tends to decrease and lose at pumping pressures during pumping, for the following main reasons:
in a first aspect, under pumping action, moisture enters capillary pores of the aggregate, reducing free water content of the cement concrete mix slurry.
In a second aspect, lubrication bubbles between aggregates collapse under pumping pressure.
In the third aspect, substances such as mud powder with wet swelling property in the cement concrete mixture are subjected to pressure water absorption and wet swelling under the action of a pump pressure, so that the absorption capacity of molecules of the water reducing agent with fluidization is increased.
The cement concrete mixture can be reduced in pumping expansion degree, thickened and reduced in fluidity, and segregation and dryness of the cement concrete mixture can be caused when the cement concrete mixture is serious.
At present, the measurement of the loss value of the expansion degree of the cement concrete mixture under the pumping pressure is carried out by actual site construction, firstly, the expansion degree of the cement concrete mixture when the cement concrete mixture is pumped in is measured, then, the expansion degree of the cement concrete mixture at the orifice of a pouring surface pump delivery pipe is measured, and the difference between the expansion degree and the expansion degree is the loss value of the pumping pressure expansion degree of the cement concrete mixture. However, the detection control method is limited to field control, and the pumping pressure expansion loss value of the cement concrete mixture before pumping is unknown and uncontrollable, and can be obtained only by attempting to perform actual construction pumping detection, so that the unpredictability and the risk of pumping construction are increased, and perhaps the pumping construction is free of any problem, and perhaps the pumping difficulty is increased, even the pumping blocking construction is interrupted, and large manpower and material resources are consumed for treatment, so that unnecessary quality and economic loss are caused.
Disclosure of Invention
The pumping pressure expansion loss value of the cement concrete mixture cannot be detected and evaluated in advance, the pumpability of the corresponding cement concrete mixture cannot be pre-controlled in advance, the method is a key problem to be solved in the current concrete pumping construction control emergency, and the method is particularly important for ultra-long and ultra-high Cheng Bengsong construction control. Therefore, the invention provides a cement concrete mixture pressure expansion degree variation test and evaluation method, which realizes the detection and quantitative analysis of the cement concrete mixture pumping pressure expansion degree loss value before construction. In order to achieve the above object, the technical scheme of the present invention is as follows.
In a first aspect of the invention, a method for testing the pressure expansion degree variation of a cement concrete mixture is disclosed, comprising the steps of:
(1) Determination of expansion k of Cement concrete mixture by slump cone 0 。
(2) Performing a pressurization test on the same batch of cement concrete mixture obtained in the step (1), and measuring the pressure expansion of the cement concrete mixture by taking the pressurized cement concrete mixture as a detection objectDegree k m And k is m And said k 0 The detection time interval of (2) is not more than 10min so as to ensure the accuracy of the calculation result.
(3) According to k 1 ＝δ k ×k m The relation of (2) will be k m Converted to k 1 Wherein: the k is 1 Representing the expansion degree, delta of the slump cone k Represents the conversion coefficient, and k 0 、k 1 、d m The units are the same; the delta is k ＝2.3－0.1k 0 /300＋0.008d m 。
(4) Calculation of k 0 And k 1 The difference value is obtained to obtain the pressure expansion degree loss value delta k of the cement concrete mixture, namely delta k=k 0 －k 1 。
Further, in step (1), the k 0 The test method of (2) is as follows: preparing cement concrete mixture, uniformly mixing, extracting a part of cement concrete mixture, filling the cement concrete mixture into a slump cone, and calculating the expansion degree k of the cement concrete mixture when no big bubbles are seen on the surface of the cement concrete mixture in the slump cone and no sinking is caused 0 Obtaining the product.
Further, after the cement concrete mixture is filled into the slump cone, a hammer is adopted to knock the outer wall of the slump cone, so that on one hand, the concrete mixture can be ensured to be completely filled into the slump cone and gas in the slump cone is promoted to be discharged, and on the other hand, the phenomenon that the cement concrete mixture in the slump cone is caused to have different components such as layering sedimentation and the like due to the fact that stones are excessively accumulated at the bottom of the slump cone and larger surface slurry is generated due to the fact that a rammer rod is adopted to insert is prevented, and therefore larger test errors are caused.
Further, in step (2), the k is tested by using a concrete pressure bleeding machine m . Preferably, a metal net, a lower filter paper, a perforated steel plate and an upper filter paper are sequentially placed in the bottom bin of the concrete pressure bleeding instrument from bottom to top, and water is injected into the bottom bin until the water is flush with the surface of the perforated steel plate.
Further, the k is tested by using a concrete pressure bleeding machine m The method comprises the following steps: vibrating the cement concrete mixture, pressurizing the vibrated cement concrete mixture, and measuring the expansion degree k of the pressurized cement concrete mixture by adopting a half slump cone m 。
Further, the method for vibrating the cement concrete mixture comprises the following steps: the cement concrete mixture is put into the pressure-bearing cylinder body in two layers, each layer is inserted and rammed, and the outer wall of the pressure-bearing cylinder body is symmetrically and uniformly beaten by a hammer until the inserted and rammed holes on the surface of the cement concrete mixture disappear and no big bubbles are generated. Optionally, the tamping rod is evenly inserted from edge to center when the tamping is performed.
Further, the method for pressurizing the vibrated cement concrete mixture comprises the following steps: pressurizing the cement concrete mixture in the pressure-bearing cylinder body by a pressurizing device of a concrete pressure bleeding instrument, wherein the pressurizing pressure is 4-6 MPa, and is kept for 20-30 s, preferably 5.5MPa, and is kept for 30s; and after the pressurization is finished, taking out the cement concrete mixture, uniformly mixing, and marking the cement concrete mixture as the cement concrete mixture to be measured.
Further, the expansion degree k of the cement concrete mixture after pressurization is measured by adopting a half slump cone m The method of (1) comprises: screening out aggregate with the size exceeding 31.5mm in the cement concrete mixture to be tested, loading the aggregate into a half slump cone, and not being inserted and tamped during loading, knocking the half slump cone through a rubber hammer, and calculating the expansion k of the cement concrete mixture to be tested when no large bubbles are seen and no sinking is caused on the surface of the concrete mixture in the half slump cone m Obtaining the product. In general, when the capacity of the half slump cone is limited and the aggregate with the size exceeding 31.5mm is too much, other materials in the mixture are difficult to add into the half slump cone or the mixture is small in proportion, so that the obtained mixture sample is insufficient.
Further, after the cement concrete mixture to be tested is filled into the half slump cone, a hammer is adopted to knock the outer wall of the slump cone so as to promote the settlement of the concrete mixture and the discharge of gas in the concrete mixture.
Further, in the step (3), the invention can also be adopted to proposeK in the following table 0 、d m 、δ k Obtaining k by the conversion relation of (2) 1 Is a numerical value of (2). With respect to the terms k 1 ＝δ k ×k m ，δ k ＝2.3－0.1k 0 /300＋0.008d m Is calculated by the relation of the k 1 The table look-up mode is adopted, so that the table look-up is more convenient and quick.
k 0 、d m 、δ k The units of the numerical values in the table are all mm.
Further, in step (3), the k 0 、k 1 、d m All accurate to 1mm, delta k Accurate to 0.01mm.
In a second aspect of the invention, a method for evaluating pumpability of a cement concrete mixture is disclosed: the pumpability of the cement concrete mixture was evaluated on the basis of the Δk: the larger the Δk value, the greater the flowability loss of the corresponding cement concrete mixture in pumping action, the worse it can be pumped.
Further, the pumpability of the cement concrete mixture is qualified, good and excellent, wherein the delta k is less than or equal to 120, the delta k is less than or equal to 90 and the delta k is less than or equal to 60.
Compared with the prior art, the invention has the following beneficial effects:
(1) The testing method provided by the invention realizes the detection and quantitative analysis of the cement concrete mixture pumping pressure expansion loss value before construction, provides a cement concrete mixture pressure expansion loss value delta k and a cement concrete mixture pumpability evaluation method, and the corresponding technical requirements of different pumping heights on the cement concrete mixture pressure expansion loss value delta k, and realizes scientific and objective advanced pre-control and evaluation of cement concrete mixture pumpability. Thereby: the method has the advantages that the purpose of predicting whether the constructed concrete meets the casting requirements of pumping construction in advance is achieved, the problems of pump blockage and casting quality are avoided, the pumping construction and quality risks are avoided and reduced, economic losses are reduced and avoided, and particularly the method has great significance in effective control and smooth construction of ultra-long and ultra-high Cheng Bengsong construction. In addition, data support and basis can be provided for evaluation and improvement of the mix proportion design performance, so that the construction quality of the cement concrete is improved.
(2) Testing the k by using a concrete pressure bleeding instrument m When the invention is used, the filter paper, the perforated steel plate and the metal net are combined and placed in the bottom bin, and the bottom bin is filled with water, so that the invention has the advantages that: on one hand, the cement concrete sample can be prevented from being pressed into the bottom bin with excessive water and cement paste under the action of piston pressure. On the other hand, due to the action of the filter paper, excessive migration of water in the bottom bin into the concrete during charging and vibrating can be prevented; the method can better reflect the actual pumping pressure state of the cement concrete mixture, and improves the detection effectiveness and accuracy.
(3) Because the volume of the concrete pressure bleeding instrument is limited, the sample volume of the cement concrete mixture in the cylinder body after the pressure test is finished cannot meet the sample volume required by the expansion degree detection of the slump cone once, the test times are increased, the test workload and time are increased, and the test efficiency is reduced; and provide the relativity mathematical formula and recommended table of the expansion degree of the half slump detection and expansion degree of the slump can detection, realize the expansion degree of the half slump detection and expansion degree calculation of the slump can detection and trade, have obviously saved test workload and time, has raised the test work efficiency.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic view of a conical slump cone according to an embodiment of the present invention, wherein: the slump cone is a cylindrical structure with a round table body penetrating up and down, and the inner diameter of the upper end faced 1 100mm, in the lower bottomDiameter ofd 2 200mm in heighth 1 300mm.
Fig. 2 is a schematic structural view of a concrete pressure bleeding machine according to an embodiment of the present invention.
FIG. 3 is a schematic diagram showing the combination of filter paper, perforated steel plate, filter paper and metal mesh in the embodiment of the invention.
FIG. 4 is a schematic view of a tapered semi-slump cone according to an embodiment of the present invention, wherein: the slump cone is a cylindrical structure with a round table body penetrating up and down, and the inner diameter of the upper end faced 3 50mm, inner diameter of lower bottom surfaced 4 100mm in heighth 2 150mm.
The labels in the figures represent: 1-a pressure gauge; 2-an oil pump; 3-piston; 4-a pressure-bearing cylinder body; 5-a bottom bin; 6-upper filter paper; 7-punching a steel plate; 8-lower filter paper; 9-a metal filter screen; 10-fastening bolts.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and the specific meaning of the terms in this invention will be understood by one of ordinary skill in the art to which this invention belongs according to the specific circumstances. Further description will now be made with reference to the drawings and specific examples.
First embodiment
The cement concrete mixture pressure expansion degree variation test and evaluation method comprises the following specific steps:
(1) Preparing a C30 cement concrete mixture for pumping, wherein the sampling number is 20L, the maximum nominal particle size of aggregate is 25mm, and uniformly mixing the samples to obtain a cement concrete mixture sample for later use.
(2) A portion of the sample was sampled from the cement concrete mixture sample, and the slump cone was filled to measure the expansion k of the cement concrete mixture as shown in FIG. 1 0 The measured value was 650mm.
(3) Because the sample component of the cement concrete mixture required by the slump cone cannot be obtained once due to the limit of the capacity of the concrete pressure bleeding instrument, the repeated simulation of pressure application can cause overlong test time, and the cement concrete mixture sample obtained repeatedly has variable, the embodiment simultaneously extracts part of the cement concrete mixture sample prepared in the step (1), carries out the pressurization test by using the concrete pressure bleeding instrument shown in the figure 2, and determines the pressure expansion k of the part of the cement concrete mixture on the basis of the pressurization test m Obtained measured value is 200mm, and k m And said k 0 The detection time interval of (2) is within 10min, the time is too long after the sample is taken out, and even if the same sample is taken out, if one of the two samples is just taken out for testing, the test is carried out after the other sample is taken out for a period of time, and the tested data can be inaccurate. k (k) m The specific measurement steps of (a) are as follows:
(i) The concrete pressure bleeding instrument is placed on a flat ground and kept horizontal, the concrete pressure bleeding instrument is opened, as shown in fig. 2 and 3, upper filter paper 6, perforated steel plate 7, lower filter paper 8 and metal net 9 are placed in the bottom bin 5 of the concrete pressure bleeding instrument from top to bottom in sequence, and then water is injected into the bottom bin 5 until the water is flush with the upper surface of the perforated steel plate 7.
(ii) The cement concrete mixture sample is put into a pressure-bearing cylinder body 4 of a pressure bleeding instrument in two layers, the number of times of inserting and tamping is 6 when each layer is put into the pressure-bearing cylinder body, the tamping rod is uniformly inserted and tamping from the edge to the center, and the outer wall of the cylinder body is symmetrically and uniformly beaten for 6 times by a rubber hammer gently until the inserting and tamping holes on the surface of the mixture disappear and no big bubbles are seen.
(iii) After the cover body of the concrete pressure bleeding instrument is covered, the fastening bolt 10 is screwed, air tightness is guaranteed, the oil pump 2 is started, the band-pass piston 3 is pressurized to 5.5MPa and kept for 30 seconds, the pressurizing pressure can be read out from the pressure gauge, the cover body is opened after the completion, the cement concrete mixture sample is taken out, and then the cement concrete mixture sample to be measured is obtained after uniform mixing.
(iv) Screening out the material to be charged by using a sieve with a pore diameter of 31.5mmAggregate with the size exceeding 31.5mm in the cement concrete mixture sample is measured, then the cement concrete mixture sample to be measured is put into a half slump barrel shown as 4, the outer wall of the cylinder body is lightly and uniformly beaten for 6 times by a rubber hammer until no big bubbles are seen on the surface of the concrete mixture in the half slump barrel and no sinking is caused, and then the expansion k of the cement concrete mixture is measured m The measured value was 200mm.
(4) The slump cone obtained in the step (2) is measured to have the expansivity k 0 Measured value 650mm and coarse aggregate maximum nominal particle diameter d of cement concrete mixture sample m Is substituted into the conversion coefficient delta by 25mm of the measured value of (2) k In the calculation formula of (a): delta k = 2.3－0.1k 0 /300＋0.008d m Obtaining the conversion coefficient delta k =2.28。
(5) Substituting 200mm of the measured value of the expansion degree km measured by the half slump cone into a formula of the slump cone for converting the expansion degree k 1: k (k) 1 ＝δ k ×k m Obtaining k 1 =456mm。
(6) Calculating the slump cone measured expansion k 0 Measured value 650mm and slump cone reduced expansion k 1 The difference between 456mm measured values is denoted Δk=k 0 －k 1 The method comprises the steps of carrying out a first treatment on the surface of the The Deltak is the loss value of the expansion degree of the pressure of the cement concrete mixture, and Deltak=194 mm is obtained.
Referring to table 1, the loss of pressure expansion value Δk is greater than 120, and is not acceptable, so that the cement concrete mixture after pumping is not satisfactory for construction.
TABLE 1 technical requirement of different pumping heights for the loss of pressure spread value Deltak of Cement concrete mixture
| Pumpability rating | Qualified product | Good grade (good) | Excellent (excellent) |
| Pumping height (mm) | <100 | 100~200 | >200 |
| Loss of pressure expansion value Deltak (mm) | ≤120 | ≤90 | ≤60 |
The reason why the loss value of the expansion degree of the pressure is large is that, through investigation and analysis: the sand has low particle strength and water absorption rate, and the crushing index value is 33 percent.
The improvement and adjustment measures are as follows: sieving sand by adopting a 4.75mm square hole sieve, preparing concrete according to the same mixing ratio, and detecting the loss value of the expansion degree of pressure according to the same method, wherein the detection result is as follows: aggregate maximum nominal particle diameter d m 25mm, k 0 Found to be at 428 mm, k m The measured value was 258mm. Calculated delta k Is 2.29, k 1 590mm and Deltak 47mm.
The analysis and evaluation are continuously carried out according to the comparison table 1, and it can be seen that the loss value delta k of the pressure expansion degree after the improvement and adjustment meets the requirement, and the pumping grade is good when the pumping construction of concrete with the pumping height of more than 200mm is met.
Further, the cement concrete mixture meeting the requirements is put into the pumping construction, and the cement concrete mixture is detected: the expansion degree of the pump inlet is 650mm, the expansion degree of the pump outlet pipe orifice after pumping is 595, the loss value delta k of the pressure expansion degree is 55mm, the pumping pouring construction is smooth, and the construction technical quality requirement is met.
Second embodiment
(1) Preparing a C50 cement concrete mixture for pumping, wherein the maximum nominal particle size of aggregate is 20mm, and the mixture is used for pumping construction and is detected: the expansion degree of the pump inlet is 660mm, the expansion degree of the pump outlet pipe orifice after pumping is 400, the loss value delta k of the expansion degree of the pressure is 260mm, the loss of the expansion degree of the pressure is large, the pumping pouring speed is low, and the pump is blocked during pouring.
(2) The reason why the loss of the expansion degree of the pressure is large is that, through investigation and analysis: the crushing index value of the particles with the particle size larger than 5mm in the sand is 32%, and the strength is low; the stone is made of granite, and the saturation dry water absorption rate is 3.2%. The improvement and adjustment measures are as follows: sieving sand by adopting a square hole sieve with the diameter of 4.75 mm; the stone is replaced by limestone material, the saturated surface dry water absorption is 0.8%, and the concrete is prepared according to the same mixing proportion.
(3) The C50 cement concrete mixture prepared after adjustment was subjected to the loss of pressure expansion value detection by referring to the first embodiment described above. The detection result is as follows: maximum particle diameter d of aggregate m 20mm, k 0 At 640mm, k m The measured value was 263mm.
(4) Look up delta according to Table 2 k =2.24, calculated, k 1 For 589mm, Δk was 56mm, and it can be seen from the analysis and evaluation performed in comparison with Table 1 above: improved adjusted compliance with pumping height>The pumping construction of 200mm concrete can be performed with the pump grade being good. The cement concrete mixture is put into the pumping construction, and the detection shows that: the expansion degree of the pump inlet is 640mm, the expansion degree of the pump outlet pipe orifice after pumping is 590, the loss value delta k of the pressure expansion degree is 50mm, the pumping pouring construction is smooth, and the construction technical quality requirement is met.
Table 2 k 0 、d m 、δ k The units of the numerical values in the table are all mm.
The test method provided by the invention can be used for detecting and quantitatively analyzing the pumping pressure expansion degree loss value of the cement concrete mixture in a laboratory before construction, and realizing scientific and objective pre-control and evaluation on the pumpability of the cement concrete mixture in advance. Therefore, the purpose of predicting whether the constructed concrete meets the casting requirements of pumping construction in advance is achieved, the problems of pump blockage and casting quality are avoided, the pumping construction and quality risks are avoided and reduced, economic losses are reduced and avoided, and the method has great significance in effective control and smooth construction of ultra-long and ultra-high Cheng Bengsong construction.
Finally, it should be noted that any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention. While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (7)
1. The method for testing the pressure expansion degree variation of the cement concrete mixture is characterized by comprising the following steps of:
(1) Determination of expansion k of Cement concrete mixture by slump cone 0 ；
(2) Performing a compression test on the same batch of cement concrete mixture obtained in the step (1), and measuring the expansion degree k of the cement concrete mixture by taking the cement concrete mixture after compression as a detection object m And k is m And said k 0 The detection time interval of (2) is not more than 10min;
(3) According to k 1 ＝δ k ×k m The relation of (2) will be k m Converted to k 1 Wherein: the k is 1 Representing the expansion degree, delta of the slump cone k Representing the conversion coefficient d m Represents the maximum nominal particle size of coarse aggregate and k 0 、k 1 、d m The units are the same; the delta is k ＝2.3-0.1k 0 /300+0.008d m ；
(4) Calculation of k 0 And k 1 The difference value is obtained to obtain the pressure expansion degree loss value delta k of the cement concrete mixture, namely delta k=k 0 －k 1 ；
In step (1), the k 0 The test method of (2) is as follows: preparing cement concrete mixture, uniformly mixing, extracting a part of cement concrete mixture, filling the cement concrete mixture into a slump cone, and testing to obtain the expansion degree k of the cement concrete mixture when no bubbles are generated on the surface of the cement concrete mixture in the slump cone and no sinking is generated 0 ；
In step (2), the k is tested by using a concrete pressure bleeding machine m A metal net, lower filter paper, a perforated steel plate and upper filter paper are sequentially placed in a bottom bin of the concrete pressure bleeding instrument from bottom to top, and water is injected into the bottom bin until the water is flush with the surface of the perforated steel plate;
the k is tested by adopting a concrete pressure bleeding instrument m The method of (1) specifically comprises the following steps: vibrating the cement concrete mixture, pressurizing the vibrated cement concrete mixture, and measuring the expansion degree k of the pressurized cement concrete mixture by adopting a half slump cone m ；
The method for pressurizing the vibrated cement concrete mixture specifically comprises the following steps: filling the cement concrete mixture into a pressure-bearing cylinder body and ensuring complete filling, pressurizing the cement concrete mixture in the pressure-bearing cylinder body by a pressurizing device of a concrete pressure bleeding instrument, taking out the cement concrete mixture after the completion, uniformly mixing, and marking the cement concrete mixture as the cement concrete mixture to be tested;
the expansion degree k of the cement concrete mixture after pressurization is measured by adopting a half slump cone m The method of (1) specifically comprises the following steps: screening out aggregate with the size exceeding 31.5mm in the cement concrete mixture, loading the aggregate into a half slump cone, and not being inserted and tamped during loading, knocking the half slump cone through a rubber hammer, and calculating the expansion k of the cement concrete mixture to be measured when no big bubbles are seen and no sinking is caused on the surface of the concrete mixture in the half slump cone m Obtaining the product.
2. The method for testing the pressure expansion degree variation of the cement concrete mixture according to claim 1, wherein after the cement concrete mixture is filled into the slump cone, the outer wall of the slump cone is knocked by a hammer.
3. The method for testing the pressure expansion degree variation of the cement concrete mixture according to claim 1, wherein the pressurizing pressure is 4-6 mpa and is maintained for 20-30 s.
4. The method for testing the pressure expansion degree variation of cement concrete mixture according to claim 3, wherein the pressurizing pressure is 5.5MPa and is maintained for 30s.
5. The method for testing the pressure expansion degree variation of the cement concrete mixture according to claim 1, wherein after the cement concrete mixture is filled into the half slump cone, the outer wall of the slump cone is knocked by a hammer.
6. A method for evaluating pumpability of a cement concrete mixture, characterized in that Δk calculated according to the test method of any one of claims 1 to 5 is used for evaluating pumpability of a cement concrete mixture: the larger the Δk value, the greater the flowability loss of the corresponding cement concrete mixture in pumping action, the worse it can be pumped.
7. The method for evaluating pumpability of a cement concrete mixture according to claim 6, wherein the pumpability of the cement concrete mixture is qualified, good and excellent, respectively, for Δk not more than 120, Δk not more than 90, and Δk not more than 60.
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