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.