The influence of anhydrite III as cement replacement material in production of lightweight masonry blocks for unreinforced non-load bearing walls

Abstract

Lightweight cellular hollow concrete (LCHC) block is a type of masonry unit that has excellent thermal and acoustic performance, fire resistance and high weathering resistance, and manufactured by precast technique. This work presents an experimental study, which investigates the effects of volumetric partial replacement of Portland cement by calcium sulfate anhydrite on precast properties, especially hardening time of the products, thermal insulation properties and mechanical properties of the blocks. LCHC block is produced by the mixing of Portland cement (PC), anhydrite III (ANH), expanded perlite (EP), pumice (PU) and calcite (CA) for building applications. The physical and mechanical properties of LCHC blocks having various replacement levels of ANH are studied. Experimental studies were carried out on both 10x10x10 cm3 cube specimens and 19x19x39 cm3 block specimens. In this research work, LCHC blocks with 16 different mixture batches were cast into a mould with vibro-compacting, de-moulded immediately and transferred to a storage area for curing up to 28 days in normal air condition. The unit weights and compressive strengths of the cube specimens decreased as the ANH replacement level increased, depending on the decrease in the cement ratio. However, it was observed that the compressive strength of the block specimens increased up to the volumetric replacement level of 1.86 %. As expected, the thermal conductivity values of the specimens decreased with the decrease in unit weight. The most notable change on the specimens occurred in the hardening time. The hardening process of the specimens can be completed up to 90 times faster than the control mixture. In addition, within the scope of the study, three formulations are presented in which the compressive strength and the elastic modulus of the wall sections made with LCHC blocks can be calculated, and thermal conductivity value of masonry block unit can be calculated.