The performance of the micro silicon powder
Micro silica fume also called silica powder, silica fume or condensed silica fume is in smelting ferrosilicon and industrial silicon, the formation of powdered silica (SiO2), the dust is micro silica fume. Micro silicon powder grains are extremely fine and the particle size is basically save 1 m below, with an average of 0.1 ~ 0.3 m, about 1 / 100 of the cement, micro silica fume is a kind of efficient active mineral admixture can significantly improve the strength and durability of concrete.
The mechanism of micro silicon powder
Micro silica fume in concrete mechanism can be summarized as: ordinary concrete is not dense, cement is gravel and angular. Due to the effect of pore water surface tension. Inter particle incomplete contact; after adding water reducing agent, eliminate the effect of surface tension of water, grain contact, the porosity is reduced; after the addition of silica fume, due to the micro silica fume particles and spherical, micro silica powder granules can be filled therein and reacted with Ca (OH) 2 generated new material. The blockage of the pores. Reducing the number of large pores, generation of C - S - H crystal, high strength, good stability. At the same time, due to the micro silica fume concrete less bleeding, improve the structure of the transition zone, so as to improve the strength of concrete.
Experimental study
1 raw materials
Test using P - 052, ordinary portland cement, ordinary river sand fineness modulus of 2.5; aggregate with gravel, continuous gradation, before the test screened and meet the maximum particle diameter 20mm continuous gradation requirements: water reducing agent by Mn superplasticizer, is a yellow brown powder. The reduction of water rate for 15%~25%, reducing agent dosage for 1.8% of cementitious materials, micro silica fume concrete with than shown in Table 1.
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Table 1 silica fume concrete mix
2 test results and analysis
Static compression tests are carried out on 60 tons of electro-hydraulic servo universal pressure testing machine and 100 tons hydraulic universal testing machine. The specimen size is 100mm * 100mm * 100mm, the test procedure is as follows:
1) the test piece is placed on the lower part of the test machine, and the pressure plate is in a horizontal state, and the center of the test piece is aligned with the center of the testing machine. Then slowly adjust the upper plate of the testing machine to make it down until the surface of the test machine is in contact with the specimen.
2) using continuous and uniform loading, take 1.0MPa per second. When the specimen is close to the failure of the start of the rapid deformation, stop adjustment test machine to the accelerator, until the destruction. Then record the damage load.
Three) the arithmetic mean value of the 3 test pieces is the intensity value of the test sample (0.1MPa); the maximum or minimum value of the three test value is 15% when the intermediate value gap exceeds the intermediate value. The value of the test results is more than 15% of the intermediate value.
Press type (the result is accurate to 0.1MPa).
=F A / FCC
FCC: is a concrete cube compressive strength (MPa); F is a specimen failure load (N); A is a pressure bearing area (mm2). The measured compressive strength of the small cube is multiplied by the coefficient of 0.95. The measured intensity of concrete 28d.
The strength effect of the trend of blob.png in Figure 1 micro silica fume content of
From Figure 1 it can be seen, nuanced doped silica fume can significantly improve the concrete compressive strength, the compressive strength of concrete with micro silica fume content increases and improve. Water cement ratio of 0.3, when the micro silica content less than 16%, micro silica fume concrete compressive strength with micro silica fume content increases and increases, and when the micro silica fume content more than 16%, adding silica fume, micro silica fume concrete compressive strength decreased. In the same water cement ratio, there is no doped silica fume, 7d and 28d static compressive strength were 48.5MPa and 65.6mpa, and reached; and nuanced doped silica fume, compressive strength significantly increased 5% doped micro silica fume 7d and 28d compressive strength than the non doped were increased by 22.7% and 23.9%. The incorporation of micro silica in alkaline environment, can quickly pozzolanic reaction occurred, generate a large number of C - S - H gel, early strength improve soon, and in the late tends to be stable.
