Slag Cement Frequently Asked Questions

1.What is slag cement (ground granulated blast furnace slag)?

Slag cement (also called ground granulated blast furnace slag) is a hydraulic cement produced during the reduction of iron ore to iron in a blast furnace. Molten slag is tapped from a blast furnace, rapidly quenched with water ("granulated"), dried and ground to a fine powder. The rapid quenching "freezes" the molten slag in a glassy state, which gives the product its cementitious properties.

2.How do I find a slag cement making equipment’s supplier?

Xinxiang Great Wall Machinery Corporation was built in 1958, up to now, Great Wall Machinery has constructed more than 100 slag grinding production lines at home and abroad. Great Wall Machinery can undertake 20 tons --1.5 million tons of Blast furnace slag/Steel slag/Nickel slag/Manganese slag powder production EPC projects. Click here to know the details. These cases will be able to let you know about the strength of Great Wall in your area.

3.What is the history of slag cement?

Slag cement use can be traced to the 1700’s when the material was combined with lime to make mortars. The first United States production was in 1896. Until the 1950’s, granulated slag was used in the manufacture of blended portland cements, or as raw feedstock to make cement clinker. However, in the 1950’s, slag cement became available in other countries as a separate product. The first granulation facility in the U.S. to make a separate slag cement product was Sparrows Point, Maryland, in the early 1980’s. Recent years have seen the supply and acceptance of slag cement grow dramatically throughout the U.S.

4.What is slag cement used for?

Slag cement is most widely used in concrete, either as a separate cementitious component or as part of a blended cement. It works synergistically with portland cement to increase strength, reduce permeability, improve resistance to chemical attack and inhibit rebar corrosion. Slag cement is used in virtually all concrete applications:

• Concrete pavements
• Structures and foundations
• Mass concrete applications, such as dams or retaining walls
• Precast and prestressed concrete
• Pipe and Block
• Concrete exposed to harsh environments, such as wastewater treatment and marine applications
• High-performance/high-strength concrete, such as high-rise structures or 100-year service life bridges

Slag cement is also used in non-concrete applications such as soil-cement and hazardous waste solidification.

5.Does slag cement change the hardened properties of concrete?

Slag cement improves many of the strength and durability properties of hardened concrete. Slag cement is a hydraulic binder that, like portland cement, reacts with water to form cementitious material (calcium-silicate hydrate or CSH). It also, similar to a pozzolan, consumes by-product calcium hydroxide from the hydration of portland cement to form additional CSH. The resulting cement paste is stronger and denser, thus improving the concrete.

6.What are the enviromental benefits of using slag cement?

Production of slag cement creates a value-added product from a material—blast furnace slag—that otherwise might be destined for disposal. Not only does the making of slag cement lessen the burden on landfills, but it also reduces air emissions at steel plants through the granulation process (as compared to the traditional air cooling process). Use of slag cement in concrete reduces the environmental impact of concrete by:

1. Reducing greenhouse gas emissions by eliminating approximately one ton of carbon dioxide for each ton of portland cement replaced.
2. Reducing energy consumption, since a ton of slag cement requires nearly 90% less energy to produce than a ton of portland cement.
3. Reducing the amount of virgin material extracted to make concrete.
4. Reducing the “urban heat island” effect by making concrete lighter in color thus reflecting more light and cooling structures and pavements with exposed concrete.

The Environmental Protection Agency recognizes the environmental benefits of using slag cement in concrete. It has classified slag cement as a “recovered” product under the Resource Conservation Recovery Act (RCRA), and has issued a procurement guideline requiring its specification on most federally-funded projects.

7.What specifications govern the use of slag cement in concrete?

Slag cement, when used as a separate component in a concrete mixture, is specified through ASTM C 989 Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortar. When used as a component in blended cement, one of two specifications are used: ASTM C595, Specification for Blended Hydraulic Cements or ASTM C1157, Standard Performance Specification for Blended Hydraulic Cement.

8.How much slag cement do I include in a concrete mixture?

The amount of slag cement added to a concrete mixture, as a percentage of cementitious material by weight, normally ranges from 20 to 80 percent. The amount for a specific project depends on several factors including application, early and later age strength requirements, durability requirements and ambient temperature to name a few. For information on proportioning and a table of suggested percentages for various applications and end results, see SCIC #2, Concrete Proportioning.

Most general or structural concrete applications (flatwork, paving, foundations, walls, columns, floors, etc.) typically use between 25 and 50% slag cement. Optimum slag cement percentage for maximum strength development is generally between 40 and 50 percent. A specification based on concrete strength at 28 days may be able to use less total cementitious material (portland + slag cement) than a similar plain portland mixture is mixture strength is optimized.

If durability parameters are specified (e.g. permeability, sulfate resistance, alkali-silica reaction (ASR) resistance) up to 70 percent slag cement may be required. For instance, one combination of portland and slag cement, in combination with a highly reactive aggregate may need as much as 70 percent slag cement to mitigate ASR, while a less reactive aggregate, combined with a lower alkali cement and slag cement may only need 25 percent.

Precast and prestressed concrete is an excellent application for slag cement at levels between 20 and 50 percent. If heat curing is used (or ambient curing temperatures relatively high) higher levels within this range are common. Using higher levels of slag cement in precast, provides the additional benefits of a more flowable mixture with smoother surface finish (fewer bugholes), and a whiter concrete appearance, often favored by designers and architects.

Mass concrete utilizes the highest potential levels of slag percentage to provide effective heat mitigation and reduced thermal stress. Mass applications use between 50 and 80 percent slag cement, with the thickest, most massive placements normally in the 65 to 80 percent range. Some slag cements in massive placements may not provide sufficient heat mitigation at the 50 to 65 percent levels because slag cement is activated by heat, and may react faster than desired because of the heat generated by portland (and slag) hydration.

9.What is the difference between slag cement and slag aggregate?

Slag cement is the hydraulic cement that results when molton slag from an iron blast furnace is rapidly quenched with water, dried and ground to a fine powder. The rapid quenching ("granulation") "freezes" slag cement in a glassy state and imparts cementitious properties to the product when ground finely.

Blast furnace slag aggregate comes in two forms:

Air cooled blast furnace slag, results when molten slag from a blast furnace slag cools slowly by ambient air (as opposed to rapid quenching), and is processed through a screening and crushing plant for use principally as a construction aggregate. Air cooled slag is not cementitious.

Pelletized or expanded slag results when molten slag is quickly cooled using water or steam. It produces a lightweight aggregate that can be used for concrete masonry, lightweight fill, or can be ground into a cementitious product.

For more information on slag aggregates, visit the National Slag Association's website.

10.What’s the best equipment to produce slag cement?

Nowadays, the slag vertical roller mills are widely accepted by customers, because it has the advantage of energy-saving, environment friendly, simple process, high intelligence.

People’s daily:Great-Wall machinery corporation provide the high quality grinding equipment with the help of “internet +”

On 16th of February ,just after the Chinese New Year ,Xinxiang Great-wall machinery Corporation which located in Xinxiang Hui xian city ,Henan Province ,have a “foreigner visiting” ,an engineer from South Africa named Jaime came here for checking and accepting the cement rotary kiln roller order ,it is the second order from international of this year. In January,one cement plant of Pakistan have bought 2 sets of vertical raw mill with capacity 300,000 MT. people.com.cn reported on 20th February .

Why a machinery manufacture company which located in inland China can get so many foreign orders ? the Vice generial manager Jiajia Liu of Great-Wall machinery corporation said:” It's all depend on the power of the Internet”.

Xinxiang Great Wall Machinery Corporation was initially built in 1958,a professional main manufacturer of kilns and mills,provided the complete equipment for cement plant,steel plant, It is a famous manufacturing enterprise.For a long time, the corporation assist for domestic market as the traditional marketing pattern.

The Great-Wall set up the Electronic Commerce department in May of 2013,starting the marketing mode like “internet +machinery + casting” .it brings a large number of orders By using the Google, Alibaba and other search engines and other B2B platforms,combining online service and offline service. The accumulated amount is 128,000,000 RMB ,including the domestic order amount : 88,200,000 RMB,international order amount: 39,800,000 RMB, the international order amount is about 30% of the accumulated amount.

“Electrical business was opened the international markets for us successfully ,it also improved the visibility and reputation of our company ,in the new year we will continue to increase investment in the internet and customer service , we will provide more and more clients of intelligent, environmental protection of grinding equipment.” Jiajia Liu said.

The equipment photo of Xinxiang Great-Wall Machinery which have exported to overseas at the beginning of 2016:

The casing of slag vertical roller mill

The chimney of slag vertical roller mill product line

The dust collecter box of slag powder production line

The explanation for new technology of GGBS

The GGBS is used to the concrete projects, such as projects involving in roads and bridges, which have higher requirements for bending strength. Meanwhile, the GGBS also suits to make concrete with high strength and high performance .The two advantages following of GGBS make it having great superiority in the big scale concrete projects, underground concrete projects and sea concrete projects.

Meng electricity cement plant took the opportunity promptly and invested and established a production line of GGBS with annual capacity of 60,0000t. Xinxiang Great Wall Machinery Co., Ltd has built the production line. The project has used the most advanced vertical mill system up to now. Different with the technology used in the conventional GGBS vertical mill system in the market, the Great Wall Machinery has innovated many new technology which ensure that the whole GGBS production can operation stably with high capacity, high efficiency ,low carbon.

1.Separation of dry material and wet material

The slag and scrap (outside cycle) and wet slag will be put into the mill separately. The wet slag will be put into the mill by spiral reamer and the scrap with iron removal will be sent to vertical mill through rotary feeder.

When the dry powder of vertical mill scrap meets the wet slag, the weak water chemical reaction happens which leads to caking. That is because the slag itself has weak hydraulic. Therefore the usual mixture scheme of feeding material will lead to hardening of spiral reamer .The hardening will reduce transportation ability of reamer, and even will break the reamer.

2.The outside cycle using bury scraping machine and hauling engine and pipe iron remover combination

Because the waster will always stay in the shell, using bury scraping machine and hauling engine and pipe iron remover combination to convey the outside waster from vertical mill can avoid overflow of waster and powder, which can improve the surrounding environment of vertical mill. For traditional belt conveyor and hanging iron remover and hauling engine and hauling engine combination, the air flow caused by the waster from the belt conveyor and the operation of hanging iron remover will lead to much floating dust and bad environment.

3.Set up steady flow storehouse ( middle storehouse )

Set up slag steady flow warehouse and make it near to the vertical mill ( located in the waster frame) .The slag measured by the belt scale under the slag steady flow warehouse will fell to a short belt, and the belt will convey the slag to spiral reamer for grinding.

Setting up the steady flow warehouse can make the material feeding of vertical mill more balance and the vertical mill will work more stable.

4.The waster material will be send to the vertical mill going through the outside warehouse

The discharged waster will be discharged to waste warehouse to store under material framework by slide pipe when vertical mill stop work. The scale is installed under outside warehouse. The powder weighed by scale will be fed in vertical mill when starting vertical mill again.

5.Set the dust collector on the chute transportation corridor

Setting a dust collector on the chute gallery between the powder collector and the finished products hauling machine can make the chute and hauling machine always work in a negative pressure condition ,which can stop the dust from overflowing caused by badly shell seal.

6.Using two gate valve to replace 3-way valve which has a high failure rate.

7.The large pieces of slag will be crushed again and again.

The large pieces of slag screened by rotary screen will go into the crusher machine for crushing and the fine particles after crushing together with the qualified fine particles will be sent to middle warehouse for grinding again. The slags are used 100 percent after realizing the feeding of loading machine.

8.Add the iron choosing machine to make a better separation effect of slag and iron

9.Other creative industrial technique

Around the foundation of the vertical mill, besides of the submerged scraping machine, other pipes like (hydraulic pipe, lubricating oil pipe, cable threading pipe) are put in the trench or buried in the foundation of vertical mill).

Set a supporting at the expansion joint of the dust collector’ air inlet and air outlet, in order to stop the pipe from sinking after several years.

The concrete platform is built in the finished product warehouse 5.300 which is used for the .repairing of electric ball machine. A daylighting window is installed on the silo wall.

Bulk machine with optimization design can avoid the powder spray outside because of the positive pressure when the bulk car is fully filled.

Set chimney at the centrifugal fan of small dust collector to reduce the noise.

The ideal choice of rotary kiln tire manufacturers-Chaeng machinery corporation

As a manufacturer and distributor of new and used rotary replacement parts, Rotary Service Company is the company of choice for Kiln Tires.Chaeng machinery corporation has a complete line of replacement one-piece and four-piece tires.Chaeng machinery corporation also provides field maintenance repair services for kiln tires and other rotary parts. Chaeng machinery corporation’s dedicated professional field staff delivers emergency on-site services 7 days a week, 24 hours a day for minor repairs or for complete replacement of parts and assemblies.

All of our Rotary Kiln Tires are engineered to OEM specifications. We provide our customers with engineered CAD drawings that include dimensional data. In order to manufacture to our customer’s specifications, drawings are sent to our customers prior to production of any part.

In addition,Chaeng machinery corporation’s engineering group can reverse engineer to exact OEM specifications, or develop new or enhanced designs of a customer’s Kiln Tires. These engineering services include mill specs and any required metallurgical verification. In addition, Chaeng machinery corporation will recommend upgrades in metallurgy and mounting designs when available. All parts, installation, and field service maintenance is guaranteed for one full year.

Chaeng machinery corporation is committed to providing quality products and services to our customers, whether for replacement or repair.Chaeng machinery corporation will work with our client’s scheduled or emergency maintenance shutdown in order to limit interruptions in their workflow.Finally,Rotary Service Company can develop a comprehensive ongoing maintenance program that is designed to increase the service life of Kiln Tires and other rotary parts in order to reduce unnecessary down time.