The test method for the water reduction rate of admixtures is carried out according to the GB8076-2008 "Concrete Admixtures" standard.
Water consumption: The slump of high-performance water-reducing agent or pumping agent reaches 210±10mm, and the slump of high-efficiency water-reducing agent reaches 80±10mm.
The mud uses standard cement, the cement dosage of high-efficiency water-reducing agent is 330kg/m3; the cement dosage of high-performance water-reducing agent and pumping agent is 360kg/m3
Stones: 5-10mm account for 40%, 10-20mm account for 60%
Sand: use medium sand
Sand rate: 36~40% for high-efficiency water-reducing agent, 43~47% for high-performance water-reducing agent and pumping agent
After the mixing ratio is designed, pour the materials into the mixing pot and stir for 2 minutes
After taking it out of the pot, stir evenly and collapse Slump test
Slump test:
High-efficiency water reducing agent: packed in three layers Put it into the cylinder, and tamp each layer for 25 times. The tamping is performed in a spiral from the outside to the center. The second and third layers are inserted into the surface of the previous layer, and then the concrete higher than the cylinder is wiped off and lifted away from the slump cylinder. , and then measure the height between the concrete slump height and the slump cylinder as the slump.
High-performance water-reducing agent and pumping agent: put into the cylinder in two layers, each layer is tamped with 15 effects, and the tamping is carried out in a spiral from the outside to the center. The second layer is inserted into the surface of the previous layer, and then the concrete higher than the cylinder is wiped off, lifted away from the slump cylinder, and then the height between the height of the concrete after collapse and the slump cylinder is measured as the slump.
Calculation of water reduction rate:
Water reduction rate = (baseline concrete water consumption - Water consumption of tested concrete) / water consumption of benchmark concrete × 100%
Benchmark concrete: concrete without admixtures
Concrete under inspection: Concrete mixed with admixtures
Concrete admixture high-efficiency water-reducing agent (water reduction rate greater than 14%) Water reduction rate steps:
1. First make a benchmark concrete without adding additives, and control the slump at 7~9 cm. Record the water consumption (for example: 210kg water)
2. Add admixtures to make one, and control the slump at 7~9 cm. Record the water consumption (for example: 180kg water)
1 Test principle
(1) Take water 142.5ml, put it into the cement slurry mixing pot, add 500 g of cement, and mix according to the method of "Method for Determination of Standard Consistency of Cement, Water Consumption, Setting Time Stability" (GT31346-2001).
(2) Measure the sinking depth S of the test cone. If the sinking depth S is within the range of (28±2)mm, the water consumption at this time is the standard consistency water consumption W; if the sinking depth S is not within the range of (28±2)mm, the water consumption should be based on the formula P=33.4- 0.185S Calculate the water consumption P1 for this consistency. Using the water consumption of this consistency P1×500, we can get the water consumption of standard consistency W1.
(3) Weigh the recommended amount of admixture. 500g cement, add water, the same as W. If the admixture is mixed first, it should be added together with the cement; if the water retention method is used, the admixture lags behind the water and is added in 1-3 minutes. Then mix according to the method of "Method for Determination of Cement Standard Consistency Water Consumption and Setting Time Stability" (GT31346-2001).
(4) After mixing, measure the test cone sinking depth S2 and calculate P2o.
(5) Water reduction rate of admixture WR,=((P,-P2)1P,)x100, the result is accurate to 0.10. </p
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