Use method and precautions.
1. Blending amount: generally 5-10% of the amount of cementitious materials. The mixing method of micro-silica fume is divided into internal mixing and external mixing.
(1) Internal blending: under the premise of the same amount of water, 1 part of silica fume can replace 3-5 parts of cement (weight) and keep the compressive strength of concrete unchanged while improving other properties of concrete.
(2) External mixing: the amount of cement remains unchanged, the addition of micro-silica fume is a significant increase in concrete strength and other properties. Concrete mixed with micro-silica fume when there is a certain slump loss. This point needs to be noted in the ratio test.
Micro-silica fume must be used in conjunction with water reducing agents, it is recommended to compound fly ash and finely ground slag to improve its constructability.
When formulating concrete with micro-silica fume, the general weight ratio with cementitious materials is.
(1) High-performance concrete: 5-10%.
(2) Hydraulic concrete: 5-10%
(3) Shotcrete: 5-10%.
(4) Pumping aid: 2-3%.
(5) Wear-resistant industrial flooring: 6-8%.
(6) Polymer mortar, insulation mortar: 10-15%.
(7) Indefinite refractory castables: 6-8%. Before use, please select the reasonable and economic dosing amount through experiment according to the actual needs.
2. Mixing method.
Micro-silica fume concrete and casting material should be made by the test room construction ratio. Strictly in accordance with the ratio of construction. In the micro-silica fume concrete mixing micro-silica fume should be added to the mixer immediately after the aggregates are fed. There are two procedures for adding:
(1) Into the aggregate, followed by micro-silica fume, cement dry mix, and then add water and other admixtures.
(2) Put in coarse aggregate+75% water + silica fume + 50% fine aggregate, mix for 15-30 seconds, then put in cement+admixture+50% fine aggregate+ 25% water, mix until uniform. Mixing time is 20-25% or 50-60 seconds longer than ordinary concrete. Never add micro-silica powder into the already mixed concrete.
3. Construction method.
There is no significant difference between the construction method of micro-silica fume concrete and ordinary concrete, but it is necessary to organize and vibrate densely during construction well. The early strength of micro-silica fume concrete will make the final setting time earlier, which should be paid attention to when plastering; at the same time, the addition of micro-silica fume will improve the viscosity of concrete and significantly reduce water secretion, making plastering slightly difficult.
4. Construction safety.
Micro-silica fume concrete construction safety should be strictly in accordance with the relevant national construction specifications for concrete projects, but because micro-silica fume is light, it is strictly forbidden to throw the material from height to prevent micro-silica fume from flying.
Product packaging, storage and transportation:
1. The product is packed in plastic woven bag with compound film. Packing specification: 30kg/bag, 25kg/bag, 20kg/bag, or ton bag.
2. The product should be stored in a dry, rain-proof and sun-proof environment. The product is caked with water and activity loss. Prohibit prolonged exposure to the sun to avoid weathering of the bag and spilling of the product.
3. This product is not dangerous goods, transportation can be handled according to the “non-dangerous goods rules”.
H. The supply form of micro-silica powder.
Micro-silica powder is mainly supplied in two forms, i.e. original state micro-silica powder and encrypted micro-silica powder.
1. The original ash micro-silica powder(undensified silica fume), that is, the product collected directly through the dust collector, the loose volume of about 150-200kg/m3, micro-silica powder into the concrete mixer, the working environment is dusty, the efficiency is low.
2, Encryption micro-silica powder(densified silica fume), in order to solve the original ash micro-silica powder is not suitable for long-distance transportation and low efficiency, developed a micro-silica powder to improve the loose compactness of the micro-silica powder “micro-silica powder encryption technology”. This technology enables the original gray micro-silica powder to roll and gather into small particle clusters under the action of compressed air flow, thus increasing the loose volume of micro-silica powder to 500-700kg/m3, which greatly facilitates the use of encrypted micro-silica powder. After feeding into the mixer to ensure that the dense micro-silica particle mass spread out and good dispersion.
I. How to distinguish micro-silica fume from silica micropowder?
First of all, micro-silica fume and silica micronized powder are two different products. As micro-silica fume and silica micronized powder are widely used in different industries, coupled with regional and industry restrictions by some enterprises and employees, mistakenly considered the same product (different industries do not know).
The appearance of micro-silica fume is gray or off-white powder ﹑ refractoriness >1600℃. Volume weight: 200-250 kg/m3. The fineness of micro-silica fume less than 1um accounts for more than 80%, with an average particle size of 0.1-0.3um and a specific surface area of 20-28m2/g. Its fineness and specific surface area are about 80-100 times that of cement and 50-70 times that of fly ash.
Micro-silica fume is mainly used in: commercial concrete, high-strength concrete, self-leveling concrete, irregular refractory materials, dry-mix (ready-mixed) mortar, high-strength non-shrink grout, wear-resistant industrial flooring, repair mortar, polymer mortar, thermal insulation mortar, anti-seepage concrete, concrete compacting agent, concrete anticorrosion agent, cement-based polymer waterproofing agent; rubber, plastic, unsaturated polyester, paint, coating and other polymer materials, reinforcement, ceramic products, etc. Modification of ceramic products, etc.
Silica micronized powder is crystalline silicon dioxide, which is a micronized powder made from natural quartz (SiO2) or fused quartz (amorphous SiO2 after natural quartz is fused and cooled at high temperature) through multiple processes such as crushing, ball milling (or vibrating or airflow milling), flotation, acid purification, and high purity water treatment. Silica micronized powder is a non-toxic, tasteless and pollution-free inorganic non-metallic material.
Because of its excellent properties such as good temperature resistance, acid and alkali corrosion resistance, poor thermal conductivity, high insulation, low expansion, stable chemical properties and high hardness, it is widely used in chemical industry, electronics, integrated circuits (IC), electrical appliances, plastics, coatings, advanced paints, rubber, national defense and other fields. With the rapid development of high technology, silica micronized powder will also enter a new period of historical development.
Appearance of silica micronized powder: white, slightly white. The specific weight is heavy, like stone powder. The common specifications of silica micronized powder are 400 mesh, 800 mesh, 1000 mesh, 1500 mesh and 2000 mesh. The feel of silica fines is relatively rough and not slippery. The content of silicon dioxide is generally 98~99.99%.
