1, using the standard
GB8076-2008 concrete admixture
GB / T8077-2000methods for testing uniformity of concrete admixture
In 2, scope of application
Applicable to ordinary concrete water-reducing agent, retarding superplasticizer, early strength water-reducing agent, water reducing retarder, air-entraining water-reducing agent, early strength agent, retarder and air entraining agent in all 9 kinds of concrete admixture.
In 3, the technical requirements
Concrete with admixture performance shall be in accordance with the GB8076-2008" concrete" to the requirements in table 1.
4, test method
The 4.1 material
4.1.1 cement
Using GB8076-2008" concrete" described in Appendix A cement. In the event no reference cement, to allow the use of C3A content of 6% ~8%, total alkali content ( Na2O+0.658K2O ) of not more than 1% clinker and gypsum, two slag grinding label ( including) greater than42.5ordinary Portland cement. But the arbitration still using reference cement.
4.1.2sand
With GB / T14684required fineness modulus is 2.6~ 2.9sand. Mud content of less than 1%.
4.1.3stone
With GB / T14685diameter of 5mm ~ 20mm ( sieve ), with two level, which accounted for 40% of5mm ~ 10mm,10mm ~ 20mm accounted for 60%. In case of any dispute, to cobble test results shall prevail.
4.1.4 water
In line with the JGJ63 requirements.
4.1.5admixture
Need to detect the admixture.
4.2mix
Reference concrete mix ratio design according to the JGJ55, mixed with Air-Entraining Admixtures for concrete and reference concrete cement, sand, stone ratio constant. Mix design should accord with the following provisions:
(1): with gravel, cement (310kg / m3soil 5); use of stone, (3305kg / m3soil ).
(2): sand rate reference concrete and concrete with admixture of sand rate is 36% ~ 40%, but mixed with air-entraining water-reducing agent and air-entraining agent of concrete sand rate should be1% to3% lower than the reference concrete.
(3) amount of admixture: according to scientific research units or production factory recommended dosage.
(4) water use: should make the concrete slump of (8010mm soil ).
4.3 concrete mixer
Using 60L Falling-self concrete mixer, all materials and additives in one time, mixing amount shall not be less than15L, not more than 45L3min, stirring, feeding in the iron on artificial turning2~ 3 times for test.
In 4.4specimens and test for the number of specimens
4.4.1specimens, specimens of concrete production and maintenance according to GB / T50080, but the concrete pre-curing temperature (20degrees C soil 3).
4.4.2test items and quantities needed to see GB8076-2008"" Table 3concrete admixture.
5, inspection items
Determination of5.1water reducing rate:
The water reducing rate of slump is essentially the same when reference concrete and concrete with admixture of water content difference and reference concrete unit water content ratio. Slump by GB / T50080 determination. The water reducing rate (1) in computing
= WR ( W0-W1) / W0x 100% ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (1).
Type : WR -- the water reducing rate, %;
W0-- Reference concrete unit water content, kg / m3;
W1-- concrete with admixture of water content, kg / m3.
The three batch of WR to test the arithmetic average value of meter, accurate to one decimal place. If the three batch of test the maximum or minimum value has an intermediate value difference than the median value of15%, the maximum value and the minimum value are eliminated, intermediary values as the group test the water reducing rate. If there are two measured value with intermediate value difference of more than 15%, then the number of test results invalid, should do.
5.2bleeding rate determination:
Bleeding rate measured by (2) calculation, accurate to one decimal place.
BR = Bt / Bc x 100... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (2)
Type : BR -- bleeding rate, %;
Bt -- admixture concrete bleeding rate, %;
Bc -- Reference concrete bleeding rate, %
Bleeding rate determination and calculation methods are as follows:
To use a damp cloth wetted volume of 5L belt cover tube (diameter185mm, high 200mm ), the concrete mixture in a mount, vibration platform vibration 20s, and then use the spatula gently smooth, sealed to prevent water evaporation. The specimen surface should be higher than the barrel mouth edge low of about 20mm. Since finishing the start time, before 60min, every 10min with pipette aspiration bleeding time, after every20min water once, until three times in a row without bleeding. Each time the suction tube should be5min, bottom side of the pad is approximately 20mm higher, so that the cylinder, in order to facilitate absorption. After absorbing water, the barrel cover lightly. Each suction water injection plug cylinder, finally calculate the total water quantity, accurate to 1g, and press (3), (4) calculating the bleeding rate.
B = VW / ( ( W / G ) GW ) x 100... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (3)
GW = G1-G0... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (4)
Type: -- bleeding rate, %;
Total quality -- bleeding, g;
-- concrete mixture of water, g;
-- concrete mixture of total mass, g;
-- a sample quality, g;
-- cylinder and sample quality, g;
-- cylinder quality, G.
Test, each batch of concrete mixture in a sample, the bleeding rate and three specimens of arithmetic average. If the three sample maximum or minimum value has an intermediate value difference than the median value of15%, the maximum value and the minimum value are eliminated, intermediary values as the group test bleeding rate. If there are two measured value with intermediate value difference of more than 15%, then the number of test results invalid, should do.
5.3air content:
According to GB / T50080with air water mixing type gas content determination, and according to the test instructions. But the concrete mixture and slightly higher than a full container, for vibration compaction15s ~ 20s, with high frequency insertion type vibrator in the model center inserted vertically ramming10s.
Test, each batch of concrete mixture in a sample, content in three samples of measured values of arithmetic average value to express. If the three sample maximum or minimum value of a with the intermediate value difference of0.5%, the maximum value and the minimum value are eliminated, intermediary values as the group test bleeding rate. If the maximum value and the minimum value are more than0.5%, then the number of test results invalid, should do.
5.4 the setting time difference measurement:
Setting time difference according to (5) calculation
Delta T = Tt - Tc ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (5)
Type: T -- setting time difference, min;
Tt -- concrete with admixture of initial setting and final setting time, min;
Tc -- Reference concrete initial setting and final setting time, min.
The setting time of the penetration resistance tester, precision of the instrument is 5N, the setting time of the method are as follows:
The concrete mixture with 5mm ( sieve ) vibration sieve out the mortar, mix into the upper diameter of160mm, and inner diameter of150mm, height150mm rigid impermeable metal cylinder, the specimen surface should be lower than the cylinder mouth of about10mm, for vibration compaction (about 3S ~ 5S (20), Park Soil 3) degrees in a C environment, the container cover. General reference concrete after molding3H ~ 4h, with early strength agent in forming1H ~ 2H, adding retarder in forming4H ~ 6h began to determine, after every0.5h or 1H were measured once, but near the initial setting, final setting time interval can be shortened when determination. Each measuring point should avoid the previous measuring holes, the spacing is2 times the diameter of the needle, but at least not less than15mm, needle and vessel edge distance of not less than 25mm. Determination of setting time with a cross-sectional area for the 100mm2test needle, the determination of final setting time with the 20mm2test needle. According to (6) calculation of penetration resistance:
R = P / A ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (6).
Type : R -- penetration resistance value, MPa;
P -- penetration depth of25mm required for the net pressure, N;
A -- penetrometer test needle cross-sectional area, mm2.
According to the calculation results, the penetration resistance value of the vertical coordinate, test time as abscissa, drawing the penetration resistance value and time curve, and penetration resistance values of3.5MPa corresponding to time as an initial setting time and penetration resistance values of28MPa corresponding to the time as the final setting time. The setting time of cement and water from the contact time.
Test, each batch of concrete mixture in a sample, the setting time take three sample average value. If the three batch of test the maximum or minimum value of one with the intermediate value difference of more than 30min, the maximum value and the minimum value are eliminated, intermediary values as the experimental setting time. If the two measured value with intermediate value difference of more than30min, the test results shall be invalid, redo.
5.5 solid content
5.5.1method summary
Will have constant weighing bottle is put into the test samples under certain temperature and drying to constant weight.
The 5.5.2 instrument
Balance: should not lower than level Four, accurate to0.0001g;
Blast electric thermostatic drying oven: the temperature range of 0DEG to 200DEG C C;
Belt cover weighing bottle:25mm x 65mm;
Dryer: filled with silica gel.
The 5.5.3test procedure
(1) will be clean with cover said flask is put into an oven at 100degrees,105 degrees30min C C drying out, placed in the dryer, cooling the 30min weighing.
(2) samples to be tested into the already constant weighing bottle, cover called a sample and the total mass of M1weighing bottle.
(3) containing the sample weighing bottle is put into an oven, to open the bottle cap, heating up to 100degrees C and 105 degrees C ( except for special varieties ) drying, cover and placed in the dryer inner cooling30min after weighing, repeat the above steps until the constant weight, its mass m2.
5.5.4 results indicated
Solid content of X fixed (7) calculation
X solid = ( m2-m0) / ( m1-m0) x 100% ... ... ... ... ... ... ... ... ... ... ... ... . (7).
Type: X solid -- solid content, %;
M0-- weighing bottle quality, g;
M1-- weighing bottle plus sample quality, g;
M2-- weighing bottle and drying quality of specimen, G.
5.5.4allows differential
Interior allowing deviation of 0.30%;
Chamber allows the deviation of 0.50%.
5.6density ( Pycnometer method)
5.6..1Abstract
The corrected volume ( V value) of the pycnometer, filled with the solution to be tested, at20 degrees C soil 5degrees C temperature, on the balance of its quality.
The 5.6.2 instrument
Specific gravity bottle:25mL or 50mL;
Balance: should not lower than level Four, accurate to0.0001g;
Dryer: filled with silica gel;
Super thermostat thermostatic equipment or equivalent.
The 5.6.3test procedure
(1) the proportion of volume correction
Specific gravity bottle in water, ethanol, acetone and ether bottle stopper washing and dry, even into the dryer, remove, weighing bottle quality is M0, until constant. Then a boiled and cooled water into a bottle stopper, the stopper, excess water from the capillary flow, with absorbent paper to drain water out of the bottle. Pay attention to not let bibulous paper suction stopper capillary water, water keeping and capillary outlet is flat, immediately in the balance a bottle filled with water quality m1.
According to the (8) V volume calculation
V = ( m1-m0) / 0.9982... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (8)
Type : V -- pycnometer in20 C volume, mL;
M0-- dry specific gravity bottle quality, g;
M1-- specific gravity bottle filled with20 C water quality, g;
0.9982--20 C water density, g / mL.
(2) additive solution density determination of P
The corrected V values of specific gravity bottle washing, drying, filled with the solution to be tested, stopper after immersion in20 degrees1 degrees C soil C super thermostat, thermostat20min after the removal, with absorbent paper to dry bottles of water and by capillary overflow solution, on the balance out the bottle filled with admixture solution to the quality of m2.
In 5.6. 4Results
Additive solution density p in (9) calculation
P = ( m2-m0) / V = ( m2-m0) / ( m1-m0) x 0.9982... ... ... ... ... ... ... ... (9).
Type: P --20 C admixture solution density, g / mL;
M2-- specific gravity bottle filled with20 degree C admixture solution quality, G.
In 5.6. 5allowable deviation
Interior allowing the difference is 0.001g / mL;
Chamber allows the difference is 0.002g / M