Fly ash concrete application
With the improvement of ecological civilization construction and environmental protection requirements, on the one hand, the prices of cement and mineral powder are increasing, and the traditional cement and commercial mixed market capacity base is huge. Therefore, the ultra-fine filler of coal and electricity solid waste based on fly ash is substituted for ordinary cement and ore. Powder, its market potential and economic benefits are huge; on the other hand, with the rise of prefabricated building materials and green high-performance concrete, the market potential of replacing mineral admixtures such as silica fume is huge and the benefits are significant. At present, the market price of silica fume is more than 2,000 yuan per ton. Substituting fly ash microbeads for silica fume can significantly reduce the cost and improve performance of high-performance concrete, with significant benefits.Micro-aggregate effect produces compact potential energy
The particles of fly ash are very small, which can act as a micro-aggregate in concrete and fill the tiny pores. At the same time, the surface hydrates to form a gel. The physical filling and the filling of the hydration reaction product work together, which is less than inert. The pure physical filling effect of aggregate is better, making the concrete denser.
Based on the above three effects, fly ash can improve the performance of concrete from at least the following aspects:
(1) Reduce water consumption of concrete, increase workability, and reduce bleeding, especially Class I fly ash, known as "solid water reducer" or "mineral water reducer".
(2) Improve compactness and impermeability.
(3) Reduce shrinkage.
(4) Reduce the heat of hydration and reduce the risk of cracking caused by the internal temperature rise of the concrete.
(5) Improve the durability of concrete. The concrete mixed with fly ash has strong continuous hydration ability, more strength increase in the later stage, and significantly improved compactness, thereby improving the ability to resist the impact of the natural environment, including crack resistance, chemical corrosion resistance, sulfate corrosion resistance, and alkali inhibition. Aggregate reaction, etc.
In addition to the above three basic effects, the fly ash effect also reflects the special functions of fly ash in concrete, such as "immune effect", "heat reduction effect", "pumping effect", "aesthetic effect", etc., but they The mechanism of this is inseparable from the basic effect. The more processes on the fly ash production line, the finer the fly ash produced, and the higher the price of fly ash. For example: the "immune effect" of fly ash is a special effect treated in accordance with the durability of concrete. Its characteristic is to show the special application value of fly ash as a basic component of concrete, which can make modern reinforced concrete engineering structures in an environment of deteriorating or severe conditions. Concrete depends on its own components to produce effective immune effects. The quality of control tends to deteriorate. However, great attention should be paid to the negative effects of fly ash immunity.
Through independent research and development, Shanghai CLIRIK redesigned and combined the grinding lining, grinding body, and discharging device of the traditional grinding machine, upgraded to an ultra-fine powder grinding machine, and combined with a special ultra-fine grade machine to form a closed circuit system, which can remove steel slag , Slag, fly ash, desulfurized gypsum and other industrial waste slag are ultra-finely ground to a specific surface area of ??700 or more, and the energy consumption per ton of product does not exceed 50 kWh.
Modification of fly ash powder, turning waste into treasure
The use of fly ash microbeads instead of alumina powder to manufacture ceramic membranes, and the use of spherical microbeads as porogens can achieve better filtration effects and greatly reduce the cost of raw materials. Utilizing the hollow, microporous and spherical features of fly ash microbeads, it can be used for heat preservation, noise reduction, light weight, adsorption material or carrier, etc.Fly ash + gypsum, lime, etc. cemented filling
In order to reduce environmental pollution and reduce the cost of filling and mining, and make full use of the solid waste and fly ash discharged from the chemical industry as the filling and cementing material to cement and fill the tailings, some scholars have conducted experiments and research.
In view of the high cost and low strength of cemented filling in mines, by analyzing the chemical composition of desulfurized gypsum, fly ash and tailings, Chen Yunnen et al. used whole tailings as the filling aggregate, and desulfurized gypsum and fly ash were the main cementing materials.
The test results show that: the amount of desulfurized gypsum and tailings is fixed, the strength of the test block with the same amount of fly ash added as cement is increased by 8.8% at 14d and the strength at 28d compared with the test block without fly ash. After 35%, the 90d strength increased by 84.1%, indicating that fly ash can significantly improve the later strength of the backfill. In the process of processing fly ash, there are still many places where fly ash mills are needed. Using desulfurized gypsum fly ash cement as a substitute for cement can not only meet the compressive strength requirements of the filling body, but also reduce the cost of full tail cement filling, and also realize the "turning waste into treasure" of desulfurized gypsum fly ash. Good social, economic and environmental benefits.
Based on the analysis of the physical and chemical properties of fly ash and crushed limestone, ST studied fly ash cement as a cementing material under a small amount of cement (pozzolan cement: fly ash = l: 20) and liquid-solid ratio = 0.2 The influence of the mixing ratio with limestone on the compressive strength and capillary water absorption coefficient of the hardened body, and the impact of the hardened body on the environment is analyzed. The results show that with the increase of limestone, the compressive strength of the hardened body gradually decreases. Ash + cement): limestone=1: 3, 28d compressive strength 1.36MPa, and (fly ash+cement): limestone=1: 6, 28d compressive strength is 0.85MPa, and the ratio decreases , The growth rate of the later strength decreases, and the large lime-sand ratio is conducive to the strength growth; the capillary water absorption mf increases with the increase of lime, indicating that the addition of limestone increases the mesoporous structure of the hardened body, which is not conducive to the development of strength.
In order to solve the economic filling problem of Liangjia Coal Mine of the Bureau of Mining Affairs, Yang Youling et al. through a test study of 21 sets of fly ash, bentonite, lime and water quick-setting materials, and found that fly ash: water: quicklime: material: Material B = l: 2: 0.3: 0.07: 0.07, fly ash: water: quicklime: Material A: material B: bentonite = l: 2: 0.3: 0.05: 0.05: 0.06 and the ratio of 4 groups of materials can meet the requirements Filling requirements: the initial setting time is less than 4h, the bleeding rate is less than 10%, the filling material cost is less than 40 yuan/m3, and the 28d strength of the filling is greater than 0.15MPa.
Feng Juen mixes fly ash with sulfoaluminate cement, gypsum, lime and composite additives to make a filling and cementitious material: when fly ash is mixed with 10% trash, the early strength is basically the same as without fly ash; when mixed with 20% , The early strength is slightly decreased, and the later strength is increased; when it is mixed with 30%, the early strength decreases significantly, and the 90d strength can reach the mantle of the all-water cement solid material without fly ash. Fly ash used as an active admixture for underground filling in mines can reduce the filling cost by 15% to 50%, and has a good prospect and practical value.
Surface modification is one of the necessary processing methods for fillers to change from general incremental fillers to functional fillers, and it is also the main purpose of mineral filler surface modification. The main effects of surface modification of mineral fillers include dispersion, viscosity reduction, filling, and interface mechanics. The most commonly used modification methods mainly include surface chemical modification, coating modification, and mechanochemical modification.
Shanghai CLIRIK provides modification equipment and solutions for various non-metallic minerals (fly ash, steel slag, slag, etc.). You are welcome to contact us.