Introduction

The cement industry improves the performance of its products every day. This continuous adaptation of production plants to technical, ecological and so on requirements makes it necessary for regular monitoring during cement manufacturing.

Some samples are taken in every step of the process and routed to a control laboratory. A fast and precise analysis device allows the duplication of controls in order to be compliant to the major standards. Different types of cement have to follow strict guidelines in terms of composition, particle size…

These characteristics affect the mechanical properties, setting time and so on of the different kinds of cement. The manufacturing process controls properties and helps in the reduction of production cost. About 1% of the worldwide energy production is consumed by the cement industry, mostly during the grinding step.

Particle size analysis helps cement manufacturers optimize the grinding process and therefore reduce their cost. Particle size analyzers are a good way to control the process and reduce costs.

Why Certified Cement ?

post32Control devices such as particle size analyzers have to be precise and reliable.

In order to verify the accuracy of these devices, the cement industry has established certified cement. It
allows:

– A regular check of the accuracy of the instrument (validation control)

– The standardization of measurements between different manufacturing sites for national or international companies.

How to obtain Certified Cement ?

Labs such as the National Society of the Littoral (SNL) in France produce some cement. An amount of this cement is taken and homogenized. Then the samples are packaged in airtight containers and are sent to different laboratories.

How to obtain Certified Cement Data?

The French Technical Association of the Industry of the Hydraulic Binder (ATILH) is one of worldwide companies which certifies cement for particle size analysis.

It arranges an interlaboratory test campaign each year. The participants are mostly French or European laboratories from various stages of cement production and consumption :

  • cement manufacturers,
  • raw material producers,
  •  cement users,
  •  research and control centers for building materials.

These tests improve the reliability of the cement test methods, compare the methods and verify the measurement reproducibility.

CILAS’ application laboratory takes part in this campaign.

Cement is measured with the two most popular techniques for size measurement in the cement industry: sieve and wet mode laser particle size analysis. The cement measurement tests are numerous and sometimes involve several operators and/or several experiment maps. Analysis of the results consists of doing statistical treatment using working methods and in producing a table with all the cement characteristics.

The measures are centralized by ATILH and are treated using classical statistical analysis: Student test, Laplace-Gauss distribution, Cochran test, and Grubbs test. Certified cement is commercially available in vials provided with a measurement certificate containing a table listing the expected size distribution.

Measurement of Reference Cement using DJD Technology

NIST Cement :

Certified Cement, such as that produced by NIST, is available for sale. This cement is used for sieve control. NIST gives the residue value at 45μm for its certified cement.

Performing cement measurements allows us to observe a good correlation between the sieve values and the results from a CILAS particle size analyzer.

Results

Residue at 45μm NIST CILAS PSA
Min value 0.60% 0.70%
Mean Value 0.79% 0.74%
Max Value 0.98% 0.76%

Results obtained show that the cement is measured correctly in dry mode using Dry Jet Dispersion (DJD) technology.

SNL Cements :

Measures of Reference Cement #8 from SNL were performed on a CILAS PSA with DJD Technology.

The SOP for Dry mode was :
– P = 220 mbars
– Vibratory Level : 1/9
– Obscuration : 10%

Results

SNL Expected values

Min Max CILAS PSA
D10% 0.99 2.29 1.51
D50% 11.52 15.2 14.08
D90% 34.34 45.33 41.39

Analysis on results of Certified Cement measurement

CILAS’ new dry measurement technology shows excellent reproducibility.

The pressure needed to disperse powders is low (less than 1 bar) and prevents the possible erosion of particles. Cohesive powders like cement are perfectly dispersed.

Excellent correlation between wet and dry modes is obtained because of the innovative calibration method of the two dispersion modes according to ISO 13320.

 

img90