Understanding GGBS in Concrete Technology
Ground Granulated Blast Slag (GGBS) is a popular supplementary cementitious material used in concrete production, derived from blast-furnace slag. The production process involves rapid quenching of molten slag with water. GGBS concrete offers advantages like improved workability, reduced water demand, and slower setting times. However, it exhibits slower strength development compared to traditional Portland cement concrete, with varying strength gains over time based on the GGBS percentage used.
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Building and Construction Engineering Department Constructional Technology 2 nd class Lecture (5): supplementary cementitious materials (SCMs) part 2 lecturer : Ruqayah Hayder
Ground granulated blast slag (GGBS) GGBS (Ground Granulated Blast-furnace Slag) is a cementitious material whose main use is in concrete. GGBS is a by-product from the blast-furnaces used to make iron. How is it produced? Blast-furnaces operate at temperatures of about 1,500 C and are fed with a carefully controlled mixture of iron ore, coke and limestone. The iron ore is reduced to iron and the remaining materials form a slag that floats on top of the iron. This slag is periodically tapped off as a molten liquid and if it is to be used for the manufacture of GGBS it has to be rapidly quenched in large volumes of water.
(GGBS) production https://www.youtube.com /watch?v=0EqizKAD7vc
GGBS concrete Ground granulated blast-furnace slag is off-white in color and substantially lighter than Portland cement CEM I. This whiter colour is also seen in concrete made with GGBS, especially at 50% replacement.
GGBS concrete On its own, GGBS hardens slowly for use in concrete, it needs to be activated by combining it with an activator (typically Portland cement CEM I but alkali activation is also used). A typical combination is 50% GGBS with 50% CEM I But, percentages of GGBS anywhere between 20 and 80% are commonly used. The greater the percentage of GGBS, the greater will be the effect on concrete properties
GGBS concrete Setting times With GGBS, the setting time will be extended slightly. An extended setting time is advantageous in that the concrete will remain workable longer. This is particularly useful in warm weather. Water demand There will be small reduction in water demand due to the difference in the rheological behavior between GGBS and Portland cement
GGBS concrete Strength gain in GGBS concrete The rate of reaction and strength development of GGBS concrete is slower than equivalent concrete made with Portland cement CEM Typically the 7-day strength of a ggbs concrete will be 55-65% of the 28- day strength compared to 70-80% for a similar CEM I Portland cement concrete. The reduction in early-strength will be more noticeable at high GGBS levels and low temperatures
GGBS concrete Relative strength development of concrete with different cement types
GGBS concrete Relative strength development of concrete with different cement types
GGBS concrete Relative strength development of concrete with different cement types
Advantages of GGBS Increases the strength and durability of the concrete structure Better workability, making placing and compaction easier Reduces the risk of thermal cracking in large pouring Reduced shrinkage cracks It reduces voids and permeability in concrete Gradual hydration of GGBS generates both lower peak and less total overall heat Considerable sustainability benefits
application of GGBS GGBS is used to make durable concrete structures in combination with ordinary portland cement Major uses of GGBS are in the production of quality-improved slag cement and in the production of ready-mixed concrete.
application of GGBS https://www.youtube.com/watch?v=YB-MpWCgUuo
https://ukcsma.co.uk/what-is-ggbs/ https://ukcsma.co.uk/ggbs-concrete/ https://www.made-in-china.com/showroom/lipeibao/product- detailtMOQyAuCXnUF/China-GGBS-Ground-Granulated- Blast-Furnace-Slag-.html https://www.constrofacilitator.com/what-are-the-advantages- and-applications-of-ggbs/
