Fly ash vs Limestone powder
Fly ash vs Limestone powder
(OP)
Hi!
Last week I posted my question about fly ash market.
Most engineers can predict that fly ash supply will reduce eventually.
This time, I wonder limestone powder can be a substitute (supplementary cementitious materials) for fly ash.
This means calcined lime is used for cement and its 'raw' powder instead of fly ash will be added later.
Another question is a small concrete company can make trustworthy mix design.
(Right now, my company has been using fly ash with the ratio of 20% of concrete by weight.)
A small concrete company can do only compression strength and workability tests.
But, other physical and chemical data are needed to use this concrete for major structural concrete members.
Please share your knowledge and experience.
Thanks!
Last week I posted my question about fly ash market.
Most engineers can predict that fly ash supply will reduce eventually.
This time, I wonder limestone powder can be a substitute (supplementary cementitious materials) for fly ash.
This means calcined lime is used for cement and its 'raw' powder instead of fly ash will be added later.
Another question is a small concrete company can make trustworthy mix design.
(Right now, my company has been using fly ash with the ratio of 20% of concrete by weight.)
A small concrete company can do only compression strength and workability tests.
But, other physical and chemical data are needed to use this concrete for major structural concrete members.
Please share your knowledge and experience.
Thanks!






RE: Fly ash vs Limestone powder
The complete reaction between the materials is slow at normal temperatures and there can still be a substantial amount of calcium unbonded after months or years (about 30%). There are processes using heat to accelerate the rate. One is an autoclave process where the concrete is subjected to 360F in a saturated atmosphere (150 psi), but is applicable to for smaller units that has large autoclaves (pressure vessels) that can be loaded and unloaded on a scheduled basis (4 to 6 hour cycle) and can achieve very high strengths (far beyond normal concrete) and uses all of the calcium during that shot cycle.
Fly ash has been used for centuries. The early fly ash was natural ash from volcanic activity, but ash from power plants is the main type used now.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Fly ash vs Limestone powder
Large contractors frequently set up batch plants in remote locations and have to meet government requirements so it's all doable. Sometimes the Contract even specifies the lab facilities that must be furnished by the Contractor.
RE: Fly ash vs Limestone powder
Yes.
The Use of Limestone in Portland Cement: A State-of-the-Art Review - Portland Cement Association, 2003
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RE: Fly ash vs Limestone powder
RE: Fly ash vs Limestone powder
RE: Fly ash vs Limestone powder
www.SlideRuleEra.net
www.VacuumTubeEra.net