Cement concrete is a porous system, these pores will directly affect the performance and service life of concrete, so in the preparation of concrete will be properly mixed with silica fume (microsilica ) and other active mineral admixtures, to increase the strength of concrete, improve its pore structure, but the specific effect is related to silica fume content and concrete curing conditions, Henan Superior Abracives sorted out the influence of silica fume on the concrete pore structure for your reference.
The effect of silica fume content on the pore structure
The influence of different dosages
The addition of silica fume can significantly reduce the pore size of the hardened slurry, and the porosity is slightly reduced, and the reduction amplitude will increase with the increase of silica fume content. The addition of silica fume also concentrates the pore size distribution in the 10 to 50 nm range. However, when the silica fume content is 15%, it will increase the large pores in the slurry. When the silica fume content does not exceed 10%, it can greatly reduce the pore size of harmful pores in the slurry, reduce the porosity, and make the slurry structure more solid.
The reason for reducing porosity and refining pore size
Silica fume has a strong chemical reactivity, and cement hydration generated Ca(OH)2 reaction, the formation of C-S-H gel, C-S-H gel quickly fills the pores between cement particles, while the particle size of silica fume itself is much smaller than the cement itself, can play a good filling role, through physical and chemical effects, reduce the total porosity of the slurry, refine the pore size, reduce the number of connected pores, and improve the pore structure of the slurry.
The influence of curing conditions on the improvement of the pore structure of silica fume
Low temperature curing conditions
Under the condition of low temperature curing, the addition of silica fume can significantly reduce the proportion of harmful pores of concrete, refine the pore structure, and within the range of no more than 10% of the dosage, the amplitude of improving the pore structure increases with the increase of silica fume content. At the same time, the compound doping of silica fume and fly ash can further reduce harmful pores, and the effect of improving the pore structure is significantly better than that of constant low temperature conditions under variable low temperature curing conditions, which is mainly related to silica fume and cement secondary hydration filling and plugging of pores, and the constant low temperature curing conditions will seriously slow down the hydration rate of silica fume and cement.
Under the steam-curing condition of concrete, the addition of silica fume will increase the porosity of the slurry, and the pore size will be significantly coarsed, the harmful pores will increase, and the proportion of harmful pores will increase. This is mainly due to the rapid reaction and rapid release of hydration heat from silica fume, which aggravates thermal damage during the steam curing process. At the same time, the silica fume has obvious coarsening of the slurry pore structure under the condition of large content, but the porosity is reduced compared with the low content, which may be related to the damage of the surface layer of the slurry.
The above content can be seen that a certain amount of silica fume can significantly improve the concrete pore structure, but excessive or improper curing, may cause the opposite effect, so before preparing concrete, should be tested, determine the appropriate amount and use of curing methods, to avoid unnecessary situations.
Henan Superior Abracieves is a new technology company that develops and promotes silica fume, which can provide high-grade silica fume with different content and use for different engineering projects, If necessary, you can leave a message on our website or call customer service calls in detail.