Measuring apparatus for rate of self-contraction of cement concrete
Technical field
The utility model belongs to building material field, relates to a kind of device of measuring sand-cement slurry and the early stage rate of self-contraction of concrete.
Background technology
The self-constriction of cement concrete is meant that under the condition of constant temperature and humidity the later volume that causes owing to the hydration of self of concrete initial set reduces, and self-constriction does not comprise dry shrink, lower the temperature shrinkage, carbonization contraction etc.The ratio that the rate of self-contraction of high-strength concrete accounts for total contraction is very high, therefore must must be controlled self-constriction.Testing out concrete rate of self-contraction accurately, simply, easily is the basis of research self-constriction, but does not also seek unity of standard both at home and abroad at present about the measurement of concrete self-constriction, and there is different problems in different measuring methods.For example, self-constriction requires just to begin after the cement initial set to measure, but most researchers is to measure just beginning after the concrete final set or behind the moulding 1d, and its main cause is the not sclerosis of concrete before the final set, can't the demoulding and sealing, and cause test difficult.In addition, problems such as at present short the or measuring accuracy of measuring method ubiquity cost height, Measuring Time is not high.
At present, the self-constriction measurement mechanism of various countries' employing generally comprises three parts: strain measurement instrument, mould and temperature measurement and control instrument.
The strain measurement instrument is the core of measurement mechanism, mainly is divided into two kinds of contactless and contacts at present.The non-contact measurement instrument comprises: capacitance type sensor, electric vortex type displacement sensor, laser displacement sensor etc., the test point of these sensors need not to contact with test specimen, makes the self-constriction of test early-age concrete become possibility.But these sensors are affected by environment significantly, and price very high, can't use so testing cost costliness repeatedly.
Instrument with contacts mainly comprises:
(1) clock gauge: the clock gauge mensuration is divided into horizontal and vertical 2 kinds.The concrete self-constriction is measured with fixing clock gauge in horizontal prism test specimen two ends;
The vertical structure structure is seen Fig. 1, at clock gauge of square iron sheet barrel upper fixed.The form removal behind airtight maintenance 1d of prism test specimen, surface are coated paraffin and are put into square iron sheet barrel 20, fill the vacant part of sealing with whiteruss 21, and the fixing clock gauge 3 in top is measured self-constriction.Clock gauge is applicable to the self-constriction test of long-age, because it can overcome the elegant problem of time of electronic sensor, and relative low price.The shortcoming of this method is the early stage self-constriction that can not test before the 1d, and concrete early-age plastic shrinkage or shrink makes a big impact to the self-constriction measurement accuracy, also can not realize control automatically and automatic data acquisition processing.
(2) embedded resistor strainometer and line Vibration Meter: the embedded resistor strainometer must be waited until when having certain cohesive strength between concrete and the strainometer, therefore could guarantee the cooperative transformation between instrument and the concrete, must wait until that concrete hardening just can test later on.The measuring method of imbedding the line Vibration Meter in concrete is that the line Vibration Meter should have suitable rigidity, and rigidity is embedding greatly easily, and is insensitive to early-age shrinkage, and rigidity is too little, though highly sensitive be not easy embedding and the operation.Simultaneously, can early concrete good with this sensor bonding, and whether the distortion of sensor truly reflects concrete distortion, also is worth inquiring into.
(3) LVDT sensor: the distortion of monitoring the early stage volume of concrete at the concrete sample two ends with the linear differential displacement transducer, this method is simple to operate, be subjected to man's activity little, but when measuring, each concrete sample all must be equipped with two sensors, and in measuring process, can not shake test specimen or sensor, the cost height.
The self-constriction measurement mechanism is very high to the sealing and the low frictional resistance requirement of mould, present widely used mould is a detachable, concrete formation with mould also as long-term Measurement die, but mould generally can not satisfy the requirement of sealing and low frictional resistance, therefore the normal very little polytetrafluoroethylmaterial material of friction factor that adopts is as interior lining panel, put into flexible polyvinyl chloride plastic film then again in the inside of interior lining panel to guarantee sealing and low frictional resistance, technology is loaded down with trivial details.
The interference that must get rid of temperature is measured in self-constriction, and method commonly used at present is an also probe temperature in the test concrete deformation, supposes concrete temperature line expansion coefficient then.But because the concrete temperature linear expansion coefficient of plastic stage and non-deterministic numerical value bring error to test result like this.Another kind method is mould to be carried out laminated heat-preserving handle, and provides a kind of environment of intimate thermal insulation with this, and is very high but this method requires mould, and do not meet with actual engineering.
The utility model content
The purpose of this utility model is: develop a kind of measurement mechanism that can measure the concrete rate of self-contraction continuously, accurately, easily.
The utility model provides a kind of measurement mechanism of measuring the concrete rate of self-contraction, comprise clock gauge and die trial, it is characterized in that: at clock gauge 3 of die trial upper fixed, this die trial is made up of the open circles stage body 11 between upper end cover 8, bottom end cover 12 and the upper and lower end cap, and the dead in line of the axis of this open circles stage body and clock gauge measuring junction stock, the bus of open circles stage body and the angle of bottom surface are α=45~60 °, put into resistance strain gage 13 and temperature sensor probe 18 in the die trial; Resistance strain gage 13 leads connect strainmeter, and temperature sensor probe 18 leads connect thermometer.
Upper end cover 8, the bottom end cover 12 of described die trial are detachable.
The utility model has the advantages that:
From the concrete initial set to 1d, can be by the concrete early stage self-constriction of strain gage testing of inside concrete, the clock gauge measured value is as a reference; The later long-term self-constriction strain of 1d can be measured by clock gauge, and this method had both been utilized the short-term measurement precision of resistance strain gage, has utilized the long-time stability of mechanical type clock gauge reading again.The open circles stage body can realize moulding and measure two kinds of functions, do not need after the moulding form removal and sealed test piece again.Die trial is designed to the open circles stage body, can reduces the resistance that concrete shrinkage is subjected to the instrument inwall effectively, the while can be avoided the concrete early-age plastic shrinkage effectively or shrink for the influence of self-constriction measurement accuracy.End cap can be dismantled up and down, has made things convenient for concrete dress mould and form removal, the utlity model has good sealing property simultaneously, does not need additionally to be provided with sealant, has made things convenient for moulding, maintenance and measurement.
Description of drawings:
Fig. 1. vertical clock gauge surveying instrument synoptic diagram
Fig. 2. synoptic diagram of the present utility model;
1-pole; The 2-horizontal gird; The 3-clock gauge; 4-through hole screw; The 5-vertical through holes; The horizontal threaded hole of 6-; The 7-gib screw; The 8-upper end cover; 11-open circles stage body; The 12-bottom end cover; 13-self-constriction measuring sonde; The 16-resistance strain gage; 17-foil gauge lead; The 18-temperature sensor probe; The 19-temperature sensor lead; α-section base angle, cone-shaped body axle center.
Embodiment:
Below the utility model is described further, the structural representation of the utility model mechanical part is seen Fig. 2.Connection support of vertical fixing above the rectangle base plate, support is made up of fixing ganoid pole 1 and horizontal gird 2, tightens with through hole screw 4 between pole and the horizontal gird.The two ends of horizontal gird respectively have a vertical through holes 5, and the diameter of vertical through holes should be slightly larger than the diameter of clock gauge measuring junction stock, and the measuring junction stock of clock gauge can insert in the vertical through holes.The horizontal direction vertical with vertical through holes has threaded hole 6, is used to install the gib screw 7 of clock gauge.In an embodiment, the diameter of the upper end cover 8 of open circles stage body is 50mm, and thickness is 10mm, and the diameter of screwed hole of centre 9 is 10mm, and to also have a diameter be the open pore of 10mm to upper end cover in addition.The height of open circles stage body 11 is 150mm, α=60 °, and the intermediate wall thickness is 6mm, the annulus of intermediate bottom for erectting, annulus height 15mm.The thickness of bottom end cover 12 is 6mm, and brim height is 30mm, and after bottom end cover buckled into open circles stage body bottom, open circles stage body bottom 15mm can be given prominence in the bottom end cover edge, and this structure had both made things convenient for concrete demoulding, also was convenient in the circular groove of base fixing.
The self-constriction measuring sonde 13 of imbedding inside concrete is copper or stainless steel material, and it is by screw cap and dull and stereotyped the composition, and dull and stereotyped length is 50mm, and width is 20mm, and thickness is 5mm, and the diameter of screw cap is 10mm, and length is 15mm.Planar surface posts resistance strain gage 16 in advance, and handles with waterproof membrane, and foil gauge lead 17 is by outwards drawing in the upper end cover preformed hole, and the lead 19 of temperature sensor probe 18 is also outwards drawn from preformed hole.The foil gauge lead connects strainmeter, and temperature sensor lead connects thermometer.After lead was drawn, preformed hole was with sealing with wax.In other embodiments, be not limited to above-mentioned size, can limit a proportional range: the limited proportion of the dull and stereotyped length of open circles stage body height and upper end cover diameter, measuring sonde is 2~4; The bus of open circles stage body axle and the angle of bottom surface are α=45~60 °; The length of self-constriction measuring sonde plate part=10: 4: 1; The dead in line of the axis of open circles stage body and clock gauge measuring junction stock.
Monitoring device structure of the present utility model comprises two parts, and a part is that the external wire of resistance strain gage connects strainmeter, reads different strain numerical value constantly by the display screen of strainmeter.Another part is the external wire external temperature meter of temperature sensor probe, reads different Temperature numerical constantly by display screen.Resistance strain gage, strainmeter, thermometer and temperature probe thereof can adopt the commercially available prod.
The disposal route of measurement result is:
Self-constriction strain: ε during from concrete initial set to 1d
1=ε
z(formula 1)
In the formula: ε
z---strain-ga(u)ge reading.
The self-constriction strain that 1d is later:
(formula 2)
In the formula: l
t---clock gauge is at t reading constantly;
l
0---the preliminary examination reading of clock gauge when 1d;
H---cone-shaped body height, 150mm.
The expansion that the concrete hydrating temperature rise produces: ε
3=Δ T (formula 3)
In the formula: Δ---concrete temperature line expansion coefficient, 1 * 10
-5/ ℃;
T---concrete internal temperature rise, ℃.
Concrete final rate of self-contraction is: ε=ε
1+ ε
2-ε
3(formula 4)
Using method of the present utility model is:
Bottom end cover buckles in the open circles stage body, and the inside fresh concrete of packing into is imbedded temperature sensor probe in the concrete, and vibrated concrete is closely knit, floating concrete surface.Screw-driving with upper end cover central through hole screw thread and self-constriction measuring sonde, then measuring sonde and upper end cover just form one, insert the measuring sonde that posts foil gauge then in concrete, it is suitable for reading that upper end cover buckles into the open circles stage body, and slight once more vibrated concrete is closely knit.The lead of foil gauge lead and temperature sensor probe stretches out from the upper end cover preformed hole, with this preformed hole of wax good seal.The open circles stage body is placed on the base plate edge that bottom end cover protrudes and the spill circular groove interlock on the base plate.Adjust the height of horizontal gird, make the clock gauge measuring junction stock that is fixed on the horizontal gird hold out against the ailhead at upper end cover center.Begin to read the reading of any time t on clock gauge, statical strain indicator and the digital display thermometer from concrete initial set, calculate the concrete self-constriction strain value of any time according to formula 1~4 as timing zero point.