Expansion/shrinkage stress testing device for cement-based material

A cement-based material and testing device technology, applied in the direction of material inspection products, etc., can solve problems such as measurement error, difficult to repeat positioning, and inability to measure expansion and contraction stress

Active Publication Date: 2010-06-16
JIANGSU SOBUTE NEW MATERIALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] Using this method can easily calculate the shrinkage and expansion stress of cement concrete under restricted conditions, but since the restraint is mainly provided by the steel bars in the middle, the degree of restraint is mainly determined by the size of the middle steel bars, the degree of restraint is not large enough, and the middle and There are stress concentrations at both ends
In addition, this method needs to move the test piece during the test, which is difficult to repeat the positioning, so it is easy to cause measurement errors and affect the calculation results, and because the test piece needs to be moved, the early expansion and contraction stress cannot be measured, and for the initial The determination of the cracking time cannot be accurately determined due to the need for human observation

Method used

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  • Expansion/shrinkage stress testing device for cement-based material
  • Expansion/shrinkage stress testing device for cement-based material
  • Expansion/shrinkage stress testing device for cement-based material

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0069] 1: Basic parameters of the test

[0070] The ring material is low carbon steel, the modulus of elasticity is 206GPa, and Poisson's ratio is 0.3.

[0071] Ring size is R 1 =52mm,R 2 =60mm,R 3 =85mm,R 4 =95mm, b=t=25mm.

[0072] The test proportion (clean pulp) is as follows:

[0073] Table 2 test mix ratio (kg / m 3 )

[0074]

[0075] In Table 2, KB is the benchmark specimen (elastic modulus 20GPa, Poisson’s ratio 0.2), PZJ is the specimen mixed with expansion agent (elastic modulus 18GPa, Poisson’s ratio 0.2), the test environment conditions are 20°C, 60% relative humidity.

[0076] 2: Test results and analysis

[0077] Figure 4 It is the steel ring strain of C50-KB group. For the net slurry KB, the outer ring is not subject to external force, which is basically 0, and the inner ring is under pressure, so it is a negative strain. At 4.2 days, the strain of the inner ring changes abruptly, which characterizes the first cracking time of the specimen.

[00...

Embodiment 2

[0084] 1: Basic parameters of the test

[0085] The ring material is Invar steel, with an elastic modulus of 160GPa and a Poisson's ratio of 0.3.

[0086] Ring size is R 1 = 100mm, R 2 =115mm, R 3 =145mm, R 4 =160mm, h=t=75mm.

[0087] The concrete test ratio is as follows (aggregate particle size 5mm-10mm):

[0088] Table 4 Example 2 concrete mix ratio (kg / m 3 )

[0089]

[0090] In Table 4, KB is the benchmark concrete specimen (elastic modulus 30GPa, Poisson’s ratio 0.2), PZJ is the concrete specimen mixed with expansion agent (elastic modulus 28GPa, Poisson’s ratio 0.2), and the test environment conditions are 20°C, 35 % relative humidity, the surface is covered with ethylene plastic film for 2.5 days of moisture-proof curing, and then dried at 35% relative humidity.

[0091] Figure 7 is the steel ring strain of concrete KB group. Within 2.5 days, the strain of the inner ring and the outer ring is basically 0, that is, the concrete has not deformed significan...

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Abstract

The invention relates to an expansion/shrinkage stress testing device for a cement-based material, which comprises an inner circular ring and an outer circular ring which are coaxial and have the same height, and a stress testing device and a data acquisition device which are electrically interconnected, wherein the inner circular ring and the outer circular ring are made of the same material; and the stress testing device comprises a plurality of test stress plates which are distributed evenly along the circumferential direction on the outer surface of the outer circular ring and the inner surface of the inner circular ring and are electrically connected with the data acquisition device. When the testing device is used, the cement-based material (such as pure slurry, mortar or concrete) is cast between the two rings. The expansion and shrinkage stress can be calculated according to the analysis of material mechanics by measuring the stress. Compared with the prior method, the testing device has the main advantages that: a, the testing device is simple, and simple and convenient to operate; b, the restraint stress is even; and c, the testing of starting self water addition molding can be implemented, the testing process needs no manpower to move the test piece, and continuous and automatic test can be realized.

Description

technical field [0001] The invention relates to a cement-based material expansion / shrinkage stress test device, which can evaluate the expansion effect of an expansion agent used to prepare shrinkage-compensating concrete, and belongs to the technical field of cement-based material testing. Background technique [0002] Shrinkage-compensated concrete refers to the concrete that is mixed with expansive agent or expansive cement to produce moderate expansion and certain self-stress under certain constraints. It is mainly used for structural self-waterproofing, filling expansion second-phase project, continuous pouring reinforced concrete project and mass concrete project for extending the distance between building expansion joints or post-casting strips. The expansion component relies on its own chemical reaction or reacts with other components of the cement to produce a certain limited expansion compensation or partially compensate for the shrinkage of the concrete during the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N33/38
Inventor 缪昌文田倩刘加平张建业姚婷郭飞王育江
Owner JIANGSU SOBUTE NEW MATERIALS
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