Applications and Advantages of Slag Powder

1. Brief Introduction
Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam.

Slag Powder Standard (GB/T18046-2017) in China:

Item Technical Parameter
S105 S95 S75
Density(g/cm3) ≥2.8
Specific Surface Area (m2/kg) ≥500 ≥400 ≥300
Activity Index 7 days ≥95 ≥70 ≥55
28 days ≥105 ≥95 ≥75
Mobility Ratio (%) ≥95
Initial Setting Time Ratio (%) ≤200
Moisture Content (%) ≤1.0
Sulfur Trioxide (%) ≤4.0
Chloridion (%) ≤0.06
Loss on Ignition (%) ≤1.0
Insoluble Matter (%) ≤3.0
Vitreous content (%) ≥85
Radioactivity IRa≤1.0 and Iγ≤1.0


2. Applications of Slag Powder
GGBS is used to make durable concrete structures in combination with ordinary portland cement and/or other pozzolanic materials. GGBS has been widely used in Europe, and increasingly in the United States and in Asia for its superiority in concrete durability, extending the lifespan of buildings from fifty years to a hundred years.
Two major uses of GGBS are in the production of quality-improved slag cement, namely Portland Blast furnace cement (PBFC) and high-slag blast-furnace cement (HSBFC), with GGBS content ranging typically from 30 to 70%; and in the production of ready-mixed or site-batched durable concrete.

(1) Making slag cement
When the specific surface area reaches 450 m2/kg~550 m2/kg and the activity index reaches 100% in 7days, it can be used in the production of 32.5~42.5 grade slag cement by using a small amount of clinker (about 25% clinker). It not only reduces the cost of cement production, but also saves a lot of energy and reduces environmental pollution. It has significant economic benefits and good social benefits.

(2) As a concrete admixture, replacing cement
Since the 28-day activity index of the slag powder can be close to or greater than 100%, the slag powder can be used to make concrete in equal or excess amount. Slag powder can reduce the amount of cement used in concrete, reduce the cost of concrete production, save resources and reduce energy consumption. In addition, the slag powder can effectively enhance the strength of the concrete and be used for high-strength concrete.

(3) Other applications
The slag powder is also used in pipe making plants as an underwater filling material. Incorporating 40% to 50% of composite slag powder into the cement pipe to replace the cement has the following advantages:
the impermeability of the concrete pipe is significantly improved, and the concrete pipe mixed with the composite slag powder is used for several decades. The concrete strength is keep increasing, which not only ensures the quality of the concrete pipe in use, but also prolongs the life of the pipe.


3. Advantages of Slag Powder Used For Concrete
(1) Slag powder can reduce the initial temperature crack of concrete.
Compared with ordinary Portland cement concrete, slag cement concrete has the characteristics of less total heat release, slower hydration heat release rate and lower temperature rise. These characteristics can reduce the initial temperature crack of concrete, especially suitable for large volume concrete. 

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(2) Slag powder can reduce sulfate attack on concrete.
The mixed slag powder can reduce the content of aluminate in the cement, thereby reducing the sulfate attack. And the mixed slag powder enhances the impermeability of the concrete and reduces the penetration of sulfate, then reduces the sulfate attack. 

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(3) Slag powder can reduce alkali aggregate reaction
The slag powder can reduce the alkali content in the cementitious material and increase the compactness of the hardened cement, thereby preventing the alkali aggregate reaction. 

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(4) Slag powder can improve corrosion resistance against chloride ions
The slag powder can improve the permeability resistance of concrete, reduces the diffusion of chloride ions in concrete, and thus enhances the corrosion resistance of steel in concrete. 

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(5) Reduce carbon emissions
The slag powder is the green building material which is a by-product of the iron making process. The carbon emissions generated during the production process are only 5-8% of the Portland cement. 

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4. Flowchart 

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1 Raw Material Silo 2 Belt scale conveyor 3 Magnetic separator 4 Bucket Elevator
5 Air-lock feeder 6 LM vertical roller mill 7 Pulse Bag Filter 8 Blower
9 Air valve 10 Hot blast stove 11 Muffler 12 Belt Conveyor
13 Magnetic Separator


5. Slag Grinding Cases

CASE1
Raw Material: Slag
Model: LM150N Vertical Mill
Output Size: 325 Mesh D70
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CASE2
Raw Material: Slag
Model: LM190N Vertical Mill
Output Size: 325 Mesh D90

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