A Comparative Study of Limestone Calcined Clay Cement Produced with Different Clay and Cement Types

Atasever, Muhammet
Limestone calcined clay cement (LC3) offers multiple advantages over portland cement, including lower CO2 emissions and superior cost-effectiveness. In addition, LC3 can be produced with existing cement factory equipment, using raw materials widely available worldwide, such as clay and limestone. The focus of this study was the production of LC3 using a range of materials with varying properties, three varieties of portland cement clinker, five different clayey soils, and one type of limestone. The clayey soils, ordinarily used in cement factories in Turkey to produce Portland cement clinker, were determined to contain varying amounts of clay minerals, some none. Initially, the influence on strength development of adding gypsum to LC3 was investigated 1, 3, 7, and 28 days. The inclusion of additional gypsum in LC3 mixtures was observed to increase early-age strength in mixtures containing kaolinite or a high quantity of calcite. Then, an experimental design using the Taguchi Method was carried out to statistically evaluate the influence of calcined clay and limestone fineness on mechanical properties at 1, 3, 7, and 28 days. The design involved two Blaine fineness levels: fine (~10000 cm2/g) and coarse (~3500 cm2/g). The mineralogical properties of the LC3 mixtures were also examined. Strength tests revealed that the fineness of calcined clays containing kaolinite, illite, or montmorillonite is statistically significant at the 95 % confidence level at later ages. The fineness of limestone is statistically significant at the 95 % confidence level in all mixtures, with the exception of the mixture produced with calcined clay containing illite at later ages. Finally, the production of limestone calcined clay calcium sulfoaluminate cement (CSA-LC3) was realized, the first time mortar samples of CSA-LC3 were made in the literature. CSA-LC3 -emits less CO2 (g/g) than portland cement, limestone calcined clay cement, or calcium sulfoaluminate cement (CSA), and can be more economical than calcium sulfoaluminate cement. PC clinker with CSA clinker in LC3 can overcome the commonly reported low-early-strength problem but is reduced at later ages. XRD results and scanning electron microscope (SEM) examinations revealed that hemicarbonate and monocarbonate phases did not form in CSA-LC3 pastes, possibly due to insufficient alkalinity of the system.
Citation Formats
M. Atasever, “A Comparative Study of Limestone Calcined Clay Cement Produced with Different Clay and Cement Types,” Ph.D. - Doctoral Program, Middle East Technical University, 2023.