3、Cement Grinding 

3.1 Gypsum Purity Identification

The final step in cement production is to grind cement clinker with gypsum, in which about 5% of dihydrate gypsum, also known as raw gypsum, is generally added. The main role of gypsum is as a retarder, in the absence of gypsum cement clinker grinding after adding water will quickly set, affecting construction and inspection. A proper amount of gypsum will increase the strength of cement. Too much or too little gypsum will cause false setting or rapid setting. So gypsum is an essential raw material in cement production.

Gypsum as a retarder can be raw gypsum (CaSO4 ·2H2O), anhydrite (CaSO4), plaster of Paris (2CaSO4·H2O), and anhydrous gypsum (CaSO4). Unripe gesso and anhydrite are natural gesso, hind two kinds are artificial dehydrated gesso. The rate of dissolution of gypsum determines its reactivity with tricalcium aluminate (C3A). The dissolution of hydrated gypsum and anhydrous gypsum is more than three times that of raw gypsum in 1min. The dissolution of raw gypsum takes several minutes to reach the dissolution equilibrium, and the solubility is about 2.1g/L. The dissolution rate of anhydrite is slow, and it takes several days or several days to reach the dissolution equilibrium (in the humid environment, anhydrite will absorb water and become gypsum containing water of crystallization). With plaster of Paris or anhydrous gypsum as retarding agent due to severe reaction, the amount of incorporation should be less, such as too much incorporation, cement mixed with water, soon formed saturated solution of gypsum, gypsum rapidly recrystallized to produce false coagulation or gypsum condensation. At present, natural gypsum is often used as retarder. These gesso have different crystal structures and are easily and quickly distinguished by XRD. Therefore, XRD diffractometer can play a role in the inspection and storage of incoming materials and gypsum purity identification.

4、Cement Finished Product Quality Control

Quality control of finished cement fillers and additives such as limestone, blast furnace slag and fly ash can be directly analyzed using XRD. The XRD fingerprint can be used as the inspection standard for qualified cement products.

5、Cement Hydration Research

After Portland cement is mixed with water, the four main clinker minerals react with water in the following ways:

3CaO·SiO2+ 6 H2O = 3CaO·2SiO2·3H2O  +3 Ca(OH)2

2(2CaO·SiO2)+4 H2O = 3CaO·2SiO2·3H2O + Ca(OH)2

3CaO·Al2O3 + 6 H2O = 3 CaO·Al2O3 ·6 H2O

4CaO·Al2O3·Fe2O3+7H2O = 3CaO·Al2O3·6H2O+CaO·Fe2O3·H2O

There are different intermediate phases in each stage of cement hydration reaction. At present, the hydration process of C3S is an exothermic process. According to the change of heat release rate and time, the hydration process can be roughly divided into five stages: early induction period, induction period, acceleration period, attenuation period and stable period. The hydration mechanism of C3S is generally not controversial in the first, fourth and fifth stages, but there are different interpretation methods for the second and third stages: the protective layer theory and the nucleation delay theory.

Therefore, XRD analyzer can be used to analyze the phases formed by each stage of cement hydration reaction, which can be used to reveal the reaction mechanism. To sum up: mirror SHINE portable XRD analyzer can be applied to different aspects of cement production process. What is more noteworthy is that it will show outstanding advantages in the analysis of C3S and C3A polycrystalline phase and has great application potential.

6、Principle of X-ray Diffractometer

X-ray diffractometer (XRD) is a kind of X-ray analysis instrument based on non-destructive detection. It qualitatively and quantitatively analyzes the main components of samples by studying the crystal structure of samples. It is widely used in medical, chemical, material, biological, geological and other research fields. Traditional X-ray diffractometer (XRD) mainly in the large laboratory XRD instrument is given priority to, mainly contains the design more complex goniometer, external accessory equipment such as water cooling system, its large size, large energy consumption, need professional characteristics in actual use of calibration on a regular basis with a lot of restrictions. In this case, the advantages of portable X-ray diffraction analyzer gradually emerged. It has the characteristics of convenient sample preparation, high efficiency and energy saving, no need for regular calibration and portability, and has been more and more applied to rapid detection in the field. In addition, the accuracy of quantitative analysis results has a good linear correlation with the accuracy of X-ray diffractometer (XRD) in traditional large laboratory, which has a high reference value.

7、Product introduction

SHINE instrument is a portable XRD/XRF equipment developed and produced by LANScientific Co., Ltd. SHINE instrument mobile XRD system is a high-performance, fully enclosed, battery operated, closed ray portable XRD analyzer, which can be used for one-time rapid XRF scanning of magnesium to uranium elements. Provide the crystal phase ID information of main component, minor component or trace component of the material. The system's minimal sample preparation technology and unique sample bay enable rapid sample analysis in the field.

The analysis speed and data quality of SHINE are extremely high, and it provides users with quantitative chemical composition values in real time on the test site where users need to know the test results most.

The SHINE is shipped with the necessary software (CrystalX analysis software) for processing X-ray diffraction data results. This software integrates AMCSD ore database, ICDD ore database and ICSD ore database to support users to match objects across databases. For quantitative analysis, CrystalX analysis software provides a RIR quantitative analysis method and a tool for analyzing various diffraction patterns.

In addition, SHINE also provides XRD pattern data in a variety of file formats, making it easy for users to obtain XRD pattern interpretation information for third party projects.

7.1 Sampling and Sample Preparation

In this experiment, the SHINE portable X-ray diffraction (XRD) analyzer of LANScientific was used to detect and analyze GBW 03201c Portland cement and GBW 03206a volcanic ash Portland cement. Powder samples were prepared by the pocket sample making box provided by LANScientific, and the samples were put into the sample chamber for detection and diffraction patterns of samples were obtained. CrystalX analysis software was used to analyze the composition of the diffraction pattern.

7.2 Equipment Configuration

Instrument Model: SHINE

Anode : Cu

Voltage: 30kV

Analysis time: 15mins

Pic 6. Display of SHINE equipment

7.3 Analysis Result

The results show that the main components of Portland cement are dicalcium silicate, tricalcium silicate, tricalcium aluminate and tetralcium ferroaluminate. Volcanic ash Portland cement also contains a certain amount of MgO.

8、Conclusion

From the analysis results show that, through the LANScientific’s SHINE portable XRD analyzer can be quickly and the analysis of various constituents in Portland cement phase and content, it will help to understand each component proportion in the cement, deduce the setting time of cement, water consumption of early change parameters such as strength, provide powerful data basis for the actual construction.