The methods of using micro silica fume and six factors affecting the quality of foam concrete

(The methods of using micro silica fume and six factors affecting the quality of foam concrete)

How to add micro silica fume

There is no significant difference in the construction method between micro silica powder concrete and ordinary concrete, but it is necessary to organize and vibrate well during construction. The early strength performance of micro silica powder concrete can advance the final setting time, and special attention should be paid when plastering. Adding micro silica powder at the same time can improve the viscosity of concrete and significantly reduce bleeding, making the plastering slightly difficult.

1. 

Generally, it is 5-10% of the amount of cementitious material. The addition methods of micro silicon powder can be divided into internal and external mixing,

1) Internal mixing: With the same amount of water added, 1 part of silica fume can replace 3-5 parts of cement (weight) and maintain the compressive strength of the concrete while improving other properties.

2) External addition: The cement dosage remains unchanged, but adding micro silica powder significantly improves the strength and other properties of concrete. When micro silica powder is added to concrete, there is a certain slump loss. This should be noted during the mix ratio test.

2. 

Doping and usage method of micro silicon powder for building concrete

When using micro silica powder to prepare concrete, the weight ratio to the cementitious material is generally:

1) High performance concrete: 5-10%;

2) Hydraulic concrete: 5-10%

3) Sprayed concrete: 5-10%;

4) Pump aid: 2-3%;

5) Wear resistant industrial floor: 6-8%;

6) Polymer mortar and insulation mortar: 10-15%,

7) Unshaped refractory casting material: 6-8%. Please select a reasonable and economical dosage through experiments based on actual needs before use. 

3. 

The construction mix proportion of micro silicon powder concrete and pouring materials shall be determined by the laboratory. Strictly follow the mix ratio for construction. In the mixing of micro silica powder concrete, the micro silica powder should be added to the mixer immediately after the aggregate is fed.

There are two ways to add:

Add aggregates, then add micro silica powder and cement for dry mixing, and then add water and other admixtures.

Add coarse aggregate+75% water+micro silica powder+50% fine aggregate, mix for 15-30 seconds, then add cement+additives+50% fine aggregate+25% water, and mix until uniform. The mixing time is extended by 20-25% or 50-60 seconds compared to ordinary concrete. Do not add silica fume to the mixed concrete. 

Six factors affecting foam concrete

Cooperation ratio

If foam concrete is prepared only by using cement, the higher the strength of the cement used, the greater the strength of foam concrete. Generally, a mixture of silicon powder, fly ash, sand, and slag is added together. The participation of the mixed materials will lead to a decrease in the early strength of foamed concrete, but it has little effect on the later strength. If stimulators are introduced together, the loss of early strength can also be reduced to some extent. When sand is used as fine aggregate, the strength of foam concrete will not be reduced in general, but it has great benefits for volume reduction and stability.

Water cement ratio

Only by analyzing the internal structure changes of foam concrete, the increase of water cement ratio will inevitably lead to the reduction of strength. Many experiments have proved that when the water cement ratio is added within a certain range, the strength will not only decrease, but also increase, because the preparation of foamed concrete has a foam mixing process. Suppose foam needs to be evenly distributed in the system. In that case, the slurry needs to have excellent fluidity, and in order to ensure excellent fluidity, a higher water cement ratio is required. However, under the condition of low water cement ratio, taking appropriate measures can also ensure excellent fluidity of cement slurry and then make high-strength foam concrete.

 

Maintenance conditions

Maintenance conditions have a serious impact on the strength and strength development of foam concrete. The water ash content of foam concrete is relatively high, so early maintenance should be strengthened to avoid strength reduction and cracking due to rapid evaporation of water. When the maintenance temperature rises, the hydration rate of cement accelerates, and foam concrete develops rapidly in the early stage, but the strength of concrete has a certain negative impact.

Additives

Admixtures related to foam concrete mainly include foaming agent, water reducing agent and additive initiator. As mentioned above, foaming agents have a greater impact on foamed concrete. It is necessary to choose foaming agents that have few side effects on the system, strong foaming ability, and high foaming strength. The main function of initiator is to make foam concrete deteriorate. Early intensity decline can reduce the fluctuation of the decline, but it also reduces the intensity of the outcome. The water reducer can make the system mix foam and slurry evenly at a lower water cement ratio.

 

Uniformity control

The control factors affecting the uniformity of foam cement slurry are mainly if the design parameters of the static mixer are reasonable or not, especially its length, the number, angle and layout of internal mixing parts. These parameters have an optimal match. Whether the match is unreasonable, the slurry will be uneven. Different manufacturers have different designs, and the core is whether they can all be reasonable and whether they have been tested and optimized before design.

Density control

The factor controlling the density of foam cement slurry is mainly the proportion of foam slurry entering the static mixer, that is, whether the proportion of foam and cement slurry is reasonable and accurate. The greater the bubble-to-paste ratio, the lighter the paste. If the ratio of the two cannot be precisely controlled, it will cause density fluctuations. The key factor is whether the equipment has designed and installed a foam and slurry control mechanism, and the degree of automation of the mechanism. At present, there is no control mechanism installed on some equipment, and the density is not easy to control. How to realize its automatic control, this is the core technology.

Suppliers of foam concrete additives

Luoyang Tongrun Info Technology Co., Ltd. (cabr-concrete.com) is a reliable and high-quality material supplier and manufacturer of foam concrete additives. It has more than 12 years of experience providing ultra-high quality chemicals and nanotechnology materials, including Water reducer, nitride powder, graphite powder, sulfide powder, and 3D printing powder. It accepts payment via Credit Card, T/T, West Union, and Paypal. TRUNNANO will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are looking for high-quality concrete additives, please feel free to contact and send an inquiry. (sales@cabr-concrete.com).

(The methods of using micro silica fume and six factors affecting the quality of foam concrete)