Marls as an Ecological Substitute for Cement with Lower Energy Consumption. Mortars Research

This work suggests how to reduce the negative impact of cement production on the natural environment. Marl rock was milled to granulation less than 1 mm, dried at 105°C, calcined at 800°C and 1000°C. The mass content of clay phase in marls was 16%, calcium carbonates 75%. Mortars of marl (m) and cement (c) in m:c proportions of 50:50, 30:70, 25:75 and 0:100 were made, in order to compare their compressive strength values after 1st, 4th and 15th week of hardening. The compressive strength of samples using marl calcined at 1000°C and dried at 105°C were similar, but lower than in the case of samples with marl calcined at 800°C. Unlike in other cases marl calcined at 800°C contained 34% of the amorphous phase. The obtained strength values ranged from 20 to 75% in relation to the cement reference samples. These low values were caused due to granulation of the marl, dilution effect, presence of non-binding phases or mechanically weak hydrates, weak microstructure of the dried and calcined marls themselves. Although these mixtures are not suitable for high-performance concrete, they had warm colour and texture that may be useful in the reconstruction of architectural details or for other decorative purposes.