Mineral Admixture Definition Classification Active admixture Introduction Secondary Hydration Reaction Function of Active Admixture Inactive admixture
Mineral Admixture Definition processed or raw mineral materials when grinding materials when grinding Improving Property Adjusting Strength Grade Lowering Costs Mineral Admixtureis the processed or raw with the purpose of improving cement property, adjusting cement grade and lowering costs. Mineral Admixture is the processed or raw with the purpose of improving cement property, adjusting cement grade and lowering costs.
Classification Classification by performance Inactive admixture （ filling admixture ） Active admixture (Pozzolan Admixture) Classification by performance: active admixture (Pozzolan Admixture) and inactive admixture （ filling admixture ）
Active Admixture It is not hardened after grinding and watering. But after mixed with lime and water A secondary hydration activity happens To form hydraulic cementing material activity Volcanic ash activity Introduction
SiO 2 +mH 2 O + xCa(OH) 2 xCaO·SiO 2 ·nH 2 O Al 2 O 3 +aH 2 O + yCa(OH) 2 yCaO·Al 2 O 3 ·bH 2 O Active admixture Consumption Ca(OH) 2 Hydraulic cementing forms Secondary Hydration Reaction
Active Admixture Although active admixture is not a compound of Portland cement. The replacement of a portion of cement with active admixture changes the properties of the various types of cement.
Hydration Reaction Takes place when portland-pozzolan cement is used or when a pozzolan is added to concrete with portland cement Portland cement hydrates First reaction Secondary cementing reaction
Characteristics of Secondary Hydration Reaction Sensitivity to temperature Low reaction speed at common temperature High reaction speed at high temperature Consumption Ca(OH) 2 Improving the structure of pores
Consumption Ca(OH) 2 When the calcium silicates hydrate, hydrated lime is one of the products of hydration This leaves a reactive soluble salt in the concrete mass and is responsible for the white encrustations and efflorescence which appears in hydraulic structures where the lime has leached to the surface and reacted with CO 2.
Function of Active Admixture Improving products. Lower costs. Better the property of cement. Adjusting strength grade of cement. Expanding application range. Benefiting to prevention of environment. Making full use of industry rubbish. Protecting the environment.
–Pozzolanic action occurs very slowly. –Consequently the temperature rise is much smaller Reducing temperature rise Better the property of cement
A pozzolan is an active, amorphous silica. Reacting readily with any alkali in the presence of moisture. The pozzolan, as a very finely divided silica. Readily consuming the Na 2 O and K 2 O from the cement. Completely dispersing the expansive silica. Consequently, the alkalis are not available to react with reactive aggregates. Reducing alkali-aggregate expansion Better the property of cement
To Reduce Harmful Effects of C 3 A The harmful effects of tricalcium aluminates can be reduced by use of a pozzolan. If the pozzolan is used to replace 30 percent of the Portland cement, the percentage of tricalcium aluminates in the total cementing material will also be reduced by 30 percent.
Types of Active Admixture Granulated blast furnace slag Other active admixture Fly ash
Types of Active Admixture Fly ash is the flu dust that is precipitated in the smokestacks of coal-burning power plants Granulated blast furnace slag composed of the fine particles of shale in the coal which form tiny spheroids of glass when exposed to the hot flame of the furnace
Types of Active Admixture Other active admixture such as –silica fume –diatomite –ground pumice –other volcanic rocks
It can’t form hydraulic cementing material with gelatification after grinding and mixing with lime in water. Quartz Clay Slow cooling slag Inactive Admixture