Properties of lime composites containing a new type of pozzolana for the improvement of strength and durability

Abstract

The basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric parameters, and thermal properties of several lime–pozzolana composites with different dosage of the burnt Czech clay shale are investigated. Within the studied range of the pozzolana:lime (P:L) ratio of 0.2:2.3–1.7:0.8, the mix with P:L=0.9:1.6 is found to be the most effective solution. Its compressive strength, bending strength, effective fracture toughness, fracture toughness, and fracture energy are up to ten times higher, as compared with the reference lime composite without pozzolana addition, the water transport parameters are several times lower, the water vapor transport parameters are only about two times higher, the freeze/thaw resistance is significantly better, and the thermal properties are comparable. In a comparison with the reference lime–metakaolin composite, the corresponding material with burnt Czech clay shale is found to achieve similar mechanical and fracture-mechanical properties, its freeze/thaw resistance is somewhat worse, the water absorption coefficient is slightly lower, the water vapor diffusion coefficient is slightly higher, and the thermal properties are comparable. Therefore, the new lime–pozzolana composites have a good potential to be used as surface layers of building structures instead of lime composites without any addition, as an alternative solution to lime–metakaolin composites.