Quailty Assurance of Cement

Quality Assurance of Cement from Production to Construction

Presented by : K.K. Choi 14th February 2006

Content Cement Standar di n HK s Cement Manuf ac tur i ngPr oc es Qual i tyAs s ur anc e Pl anni ng Qual i tyContr olSc hemes

Quality Planning

National Standards Customer Requirements Market Positioning Raw Material Constrains Process Constrains

QUALITY PLANS: • Product Specification • Process Specification • Procedures • Sampling & Testing Plans • Work Instruction/Records • Testing Data QA

Cement Standard Migration Portland Cement Standard

HK Adoption year

BS12:1989

1992

BS12:1991

-

BS12:1996

2003

BSEN197-1:2000

2005

Major Changes since BS12:1991

BS12:1989

Since BS12:1991

Test method

Mortar and Concrete cube Mortar prism test to EN196 tests to BS4550

Classification

By Fineness and early 4 major Strength Classes in BS, strength, into CFPC, OPC and 3 major strength classes and RHPC in BSEN197:2000

Minor constituents

Not permitted

Up to 5%

Compliance

Based on single sample and single test. Compliance based on absolute limits

Employs statistical method in strength class classification, and Single Sample Acceptance based on deviations.

Conformity Criteria Arithmetic Mean

Population

P C3A CA +3C +F => C4AF CS + C => C2S 2C + S => C2S

1450oC C2S + C => C3S

1100oC

Cooler

To Clinker Silo 110oC

Cement Kiln Controls

Kiln Feed

80oC

380oC

600oC

750oC

Combustion air control ® Reduce excess air ® Prevent reducing atmosphere ( Fe2+ formation)

Precalciner temperature control Provide reactive oxide for sintering Reduce kiln thermal loading

870oC 850oC

Clinker cooling rate Control crystal and glass formation Control of alite size Control periclase (MgO) crystal

1000oC 900oC

Kiln

1450oC

Burning zone temperature control Reduce residue free lime Complete transform C2S to C3S

1100oC

Cooler

To Clinker Silo 110oC

Typical Close Circuit Finish Grinding With High Efficiency Separator High Efficiency Separator

∑Control particle size distribution

Gypsum dosing ® Control hydration reaction ® Obtain optimal dosing

Clinker

Gypsum

Cement cooling ®Control false setting during storage

Additives

Additives dosing

Finish mill

Reduce strength deviation Regulate strength

Cement Cooler Water spray

Cement Silo

Mill temperature control Control false setting during grinding

Comparison of Size distribution on Separator product 8.00 7.00

result in %

6.00 5.00 4.00

e Over-grind

Inert

3.00

Active

2.00 1.00 0.00 0.10

1.00

10.00

100.00

size (u) Conventional

H.Efficiency

1000.00

Comparison of Separator Blaine, 45um residue, % cm2/g

Specific Power Consumption, kWh/t

Open Circuit

3800

14%

-

Mechanical Separator H. E. Separator

3600

14%

49

3200

8%

45 (-8%)

Conflict between BS12:1989 & HE Separator Test items Fineness, m2/kg Mortar Strength 3 days, MPa 28 days, MPa

BS12:1989 Limits

2002 Average

OPC

RHPC

HK

Japan

>275

>350

330

325

>25

>25

35.5

34.0

>47 52

69.0

68.5

Standards & Cement Process HE Separator drove the review of BS12:1989. Auto-Control scheme of BS12:1991 provides incentives to reduce SD through QA. Provision of 5% additive enables better control of strength variation and cost saving. End-users are benefit from the addition of 5% pozzolanas.

Thank You