Presentation on theme: "Cement – Specification and Performance Hugh Wang Eduardo Caballero CEMEX USA"— Presentation transcript:
Cement – Specification and Performance Hugh Wang Eduardo Caballero CEMEX USA
Use of cement: Cement is ONLY one of the ingredients in any applications – well cementing or construction concreting. The specified quality parameters of cement are tested without considering other ingredients. Lessons learned from concrete mixtures - interaction of cement with other ingredients can be critical to performance.
Mineral C 3 S, C 2 S, C 3 A, C 4 AF Burning Chemistry Ca, Si, Al, Fe Proportioning Physical fineness, strength, TT, FF etc Grinding Production of quality well cement involves:
Desired clinker characteristics for well cement: Mineral C 3 S, C 2 S, C 3 A, C 4 AF Well crystallized alite; Optimize burning condition in order to minimize f-CaO content; Generally very low in C 3 A content – a challenge for kiln operation.
Physical properties requirements: Physical fineness, strength, TT, free fluid, etc Fineness; Thickening time (TT); Free fluid (FF). Potential conflicting response: Fineness vs TT; Fineness vs FF.
Specifications - ASTM vs API : Fineness: ASTM lowered the limit from 280 to 260 m 2 /kg; SO 3 : ASTM adopted performance based specification; D It is permissible to exceed the values in the table for SO 3 content, provided it has been demonstrated by Test Method C1038 that the cement with the increased SO 3 will not develop expansion exceeding % at 14 days. C 3 S: No requirement for MSR and HSR cements. C 4 AF+2C 3 A: 24 API vs 25 ASTM.
Mineral calculation – ASTM:
Mineral calculation – API 10A:
Mineral calculation – API vs ASTM:
Discussions – ASTM vs API Minimum blaine 400 m 2 /kg for API Class-C: if high blaine is intended for early strength, its benefit may be potentially reduced due to the higher water demand. Minimum blaine for other types of cements should be harmonized with ASTM requirements from 280 to 260 m 2 /kg;. This will improve thickening time performance. Why ASTM revised cement SO 3 content? –Critical in the mixtures containing supplementary cementitious materials (SCM) and chemical admixtures. Construction industry has gone through the learning process. –Potential incompatibility problems in the mixtures shall be considered when complex components are used in slurry.
Cement hydration rate profile I II III IV V Stage I: dissolutionStage II: induction (dormant) Stage III: accelerationStage IV: deceleration Stage V: steady Time in hours Energy release rate mW/g Maximum heat release rate On-set of acceleration stage Conversion of ettringite to mono-sulfate
Well cement with 50% Class-C fly ash (C-FA) Viscosity increase
Well cement with 50% C-FA and 1.5% gypsum
Viscosity profile comparison Gypsum addition eliminates high viscosity during early stages
SO 3 : Supply - Demand Rule SO 3 supply SO 3 demand false normal flash
If SO 3 supply is greater than demand false normal flash SO 3 supplySO 3 demand
If SO 3 supply is greater than demand false normal flash SO 3 supply SO 3 demand
If SO 3 supply is less than demand false normal flash SO 3 supplySO 3 demand
If SO 3 supply is less than demand false normal flash SO 3 supply SO 3 demand
In order to make well cement more robust for slurry mixtures containing SCM and chemical admixtures, the cement SO 3 needs to be optimized. The 280 m 2 /kg blaine requirement needs to be revised to 260 m 2 /kg, this will help to improve thickening time. The minimum blaine 400 m 2 /kg for Class-C cement may be eliminated by specifying the strength requirement. Harmonize cement mineral phase calculation to reflect lasted advance in understanding cement chemistry. Recommendations