Ceramicrete matrix

Wagh and Singh [2-4] have incorporated a range of waste streams and other extenders in Ceramicrete and shown that desired properties can be obtained in Ceramicrete matrix composites. Table 14.2 compares typical properties of Ceramicrete and cement. It also lists the extenders used and niche applications. 

Typical Properties of Ceramicrete Matrix Composites and their Applications. 

Though the data given in Table 14.2 are for Ceramicrete matrix composites, similar properties in other CBPC matrix composites are possible with different extenders. Therefore, overall CBPC matrix composites are versatile materials and have the potential for varied applications as structural and nuclear materials, as well as civil engineering applications in general. In this chapter, we discuss some common CBPC matrix composites and their applications in the construction industry. Additional applications are presented in subsequent chapters. 

Wagh et al. [2] conducted a systematic study of incorporating Class C and Class F ash with compositions described in Table 14.1, and their mixture in the Ceramicrete matrix. Table 14.3 provides the properties of the resulting ceramics. 

During Ceramicrete formation using H3PO4, the caustic soda reacts with the acid-phosphate and forms amorphous MgNaP04 H2O. The neutralized waste is micro-encapsulated in the Ceramicrete matrix, in which the MgNaP04 H20 also acts like a binding phase. 

Two road patches were repaired at ANL with Ceramicrete matrix composite containing 50 wt% class F fly ash on a trial basis in March 1999. The potholes are located on a road with heavy traflic from dehvery trucks. The debris from the patches was not cleared, nor were the sides cut into smoother shapes as normally done. The temperature was 40 °F. After a few hours, it rained heavily, and the patches, being in low-lying areas, were under water till the next day. In spite of this weather, the patches set well the next day. They have not only withstood traflic for the last four years, but also the freeze-thaw cycles of the three winters have not affected patch integrity. At present, the intact patches show up well because the original asphalt road surrounding the patches is crumbling. 

Bindan Corp. (Oak Brook, IL) sells several compositions of Ceramicrete matrix composite as commercial road-repair materials. The American Association of State Highway Transportation Officials (AASHTO) has tested one of these products [6]. Table 14.6 provides the results of their tests. 

In contrast to the two studies mentioned above, the work at ANL has been mainly in demonstrating treatment of a range of radioactive waste streams (both simulated and actual) from the US DOE complex in the Ceramicrete matrix. The reader is referred to Ref. [21] and additional references therein. In this section, we provide an overview in the form of case studies. Table 17.5 lists acceptance criteria and the corresponding case studies selected to demonstrate compliance by the Ceramicrete waste forms with those criteria. 

As mentioned in Section 17.3.1, retention of quadrivalent actinide oxides within the phosphate matrix is not a major issue because these oxides are insoluble in water, and all that is needed is their microencapsulation by the phosphate components of the matrix. This was demonstrated in a number of studies on UO2 and PUO2 and their surrogate Ce02. If the actinides are found in a trace amount in the waste, their chemical form is not so important because the phosphate matrix immobilizes them very efiectively. For example, the wastewater in the case study given in Section 16.3.2.2 contained 32 pCi/ml of and 0.6 pCi/ml of The ANS 16.1 tests conducted on the waste forms with 18.6pCi/g loading of combined U in the waste form showed that the leaching index was 14.52. XCLP tests also showed that levels in the leachate were below the detection limit of 0.2 pCi/ml. This implies that microencapsulation of trace-level U is very efiective in the Ceramicrete matrix. 

Wagh et al. [29] demonstrated that radium-rich wastes from Femald silos can be stabilized in the Ceramicrete matrix. The total specific activity of all the isotopes in the waste was... 

Though the open porosity in the ash-containing Ceramicrete is very low, the matrix has a significant amount of closed or isolated pores. Estimates, based on the densities of individual minerals formed in the final products, show that the closed porosity is =20 vol%. Coupled with this closed porosity, a significant amount of bound water (typically 15 wt%) in the binder component makes this cement lightweight. 

As listed in Table 14.1, various other waste streams can be incorporated in Ceramicrete to produce useful ceramic matrix composites. In addition to those listed in the table, Wagh and his group have explored incorporating drill cuttings from oil fields, slags from iron industry, wood chips, saw dust, and many other waste streams [8]. Most of these studies were limited to proof of concept, and more work is needed to demonstrate concept usefulness. Here, we discuss case studies on swarfs and red mud in which detailed work has been done. 

This versatility allows one to develop CBPC matrix composites with specific properties required for niche applications (see Table 14.2), such as heavy Ceramicrete with iron oxide or light-weight Ceramicrete with cenospheres, 7-ray shield with iron oxides or any other heavy metal oxide, neutron shield with light elements such as boron, insulators with cenospheres and ash, and comparatively better conductor with metals. The remaining chapters in this book address some of the niche applications where considerable scientific... 

Na, and B from a glass waste form. If, on the other hand, this test is to be adopted for a CBPC waste form, such as Ceramicrete, one may look for Mg, K, and P as the matrix components. Thus, the PCX evaluates the durability of the matrix material, which is a result of the integrity of the individual elements within the matrix. 

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