matters needing attention for the use of microsilica in construction-pg电玩城

previously calculation: some scholars and experts to the amount of 15% of microsilica to replace cement, cement particles in the concrete and the proportion of microsilica particle number is 20, 00000, thus the microsilica is a kind of super fine powder material, the increase of concrete strength, is the key to improve the bond strength between cement paste and aggregate, can reduce fresh water, prevent moisture under the aggregate surface, thus improve the interfacial transition zone, compactness and reduce the thickness of interface transition zone. microsilica is not suitable for all occasions. 

it is necessary for those who are working on the concrete technology request to carefully analyze specific application situations and acknowledge that the application of microsilica can achieve the desired effect. 

it is necessary to use microsilica in concrete of suitable composition (collaboration ratio), which should be low water-binder ratio (w/ cm) and concrete containing high efficiency water reducing agent. the previous study found that the water-binder ratio of the concrete with micro-silicon powder was 0.6 or higher, which was unreasonable. 

the combined application of microsilica and other auxiliary cementitious materials is being added. at first, these materials were seen as competing materials, but now there is a growing recognition that the best concrete is often the combination of these materials. the amount of microsilica per unit volume of concrete is being reduced, especially for concrete exposed to chlorine. the concrete of the bridge deck at the beginning contains 12% ~ 15% microsilica (measured by cement weight), and the amount of microsilica is reduced to 8% distribution in the next few years. now, if combined with fly ash or ground slag, the content of microsilica is reduced to 5%. when the content of microsilica increases significantly, the strength contribution rate of microsilica to concrete decreases (also known as efficiency index decreases). experiments show that the efficiency index decreases significantly when the microsilica replaces cement more than 20%. when it is more than 30%, the strength of concrete decreases instead, and the risk of plastic cracking and early shrinkage crack of concrete increases. 

in addition, when the amount of microsilica is too high, the fresh concrete becomes very thick, and the difficulty of construction vibration increases. as the output of micro-silicon powder is limited, the price amounts to 2500~4000 yuan of micro-silicon powder are increased, which will increase the cost of concrete. therefore, in practical engineering, the amount of microsilica in concrete is generally 5% to 15%.