Silica fume concrete descrption Silica fume in concrete Because the silica fume powder can fill the pores between the cement particles, it also forms a gel with the hydration product and reacts with the basic material magnesium oxide to form a gel. In cement-based concrete, mortar, concrete, and...Send InquiryChat Now
Silica fume concrete descrption
Silica fume in concrete
Because the silica fume powder can fill the pores between the cement particles, it also forms a gel with the hydration product and reacts with the basic material magnesium oxide to form a gel. In cement-based concrete, mortar, concrete, and refractory castables, the appropriate amount of silica fume silica fume in concrete can be used as follows:
1. Significantly improve compressive, flexural, impermeability, corrosion resistance, impact resistance and wear resistance.
2, with water, prevent segregation, bleeding, significantly reduce the role of pumping resistance.
3, significantly prolong the service life. Especially in the harsh environment of chloride salt pollution, sulfate erosion, high humidity and other harsh environments, the durability of concrete can be doubled or even several times.
4. Significantly reduce the landing ash of jet ramming and pouring materials, and increase the single shot layer thickness.
5. It is an essential component of high-strength plutonium, and it has been applied in engineering of C150.
6. It has the effect of about 5 times of cement, and it can reduce the cost and improve the durability when it is used in common concrete and low cement castables.
7, to effectively prevent the occurrence of alkali oxime aggregate reaction.
8. Improve the compactness of cast refractories. In coexistence with Al2O3, the mullite phase is more easily formed, so that its high-temperature strength and thermal shock resistance are enhanced.
Silica fume concrete application
For the mix design of microsilica fume concrete, the main method is to determine the method of incorporation of silica fume, the optimum amount of micro-silica fume, the optimal amount of superplasticizer, and the adjustment of sand and stone, according to the design requirements.
Ordinary concrete design method.
a) Method of incorporation of micro-silica fume:
There are generally two methods for micro-silica fume in concrete:
one is for blending and the other is for blending, and it should be used in conjunction with a water-reducing agent.
The internal mixing method often uses micro-silicon instead of cement, which is replaced by equivalent and partial equivalents.
The equivalent volume is replaced by micro-silicon powder instead of equivalent cement, and partially replaced by 1 kg of micro-silicon instead of 1 to 3 Kg cement, as research general content of 5% to 30%, water-cement ratio remained the same:
while the external mixing means that the micro-silica fume is mixed into the concrete like an admixture, and the amount of cement is not reduced. Usually 5% to 10%, the general mechanical properties of concrete obtained by external mixing are much higher,
but the amount of cementitious material in the concrete is increased.
b) The optimum amount of micro-silica fume:
The amount of micro-silica fume added in the concrete is too little to improve the performance of the concrete.
However, if the amount is too much, the concrete is too viscous to be easily applied, and the drying shrinkage is large. Poor coldness, therefore, when adding micro-silica powder, should find the optimal amount to get the best results. Under normal circumstances, the effect of less than 10% is more satisfactory.
The appropriate amount of micro-silica fume is generally based on the microsilica used, the type of cement and the properties of the aggregate, and several microsilica dosing amounts are selected, such as 3, 5, 7, 10%, etc., to form concrete specimens and draw R-SF (strength - microsilica dosing) curves are determined. It is worth noting that the price of microsilica is relatively high. When determining the optimum amount of microsilica, it is also necessary to consider technical and economic indicators.
c) The optimum amount of water reducer:
Use micro-silica in concrete, if not add water reducer, if you want to maintain the same fluidity, it will inevitably increase the amount of water, the ratio of water to cement increase, and add micro-silica The strength of concrete does not go up, which is why the use of micro-silica fume has not been promoted in concrete in the past. The water-cement ratio of the micro-silica powder and the water-reducing agent used in combination with the micro-silica fume is constant, ie, the water consumption does not increase, and the same fluidity as the concrete without the micro-silica fume can be achieved, and the strength of the micro-silica fume concrete is also achieved. It has been greatly improved. In general, domestic use of naphthalene-based superplasticizers such as 1, H, DH3, FDN, NF, N2B, etc., is generally within 1% of the amount of rubber used, and sometimes to reduce water consumption. Ash ratio, mixing ultra-high strength concrete, water reducing agent dosage of 2% to 3%.
d) Aggregate dosage adjustment: The amount of gravel does not have to be adjusted in general with microsilica. External micro-silica powder should be deducted from the volume of sand with the same volume of micro-silica.
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