Special Issue: MDA2018 Environmentally friendly lightweight gypsum-based materials with waste stone dust J Krejsova ´, R Schneiderova ´ Heralova ´, M Dolez ˇelova ´ and A Vimmrova ´ Abstract Gypsum is one of the most environmentally friendly binders and consequently its importance in building industry is increasing. New applications are being sought and new materials are being developed. A lightweight gypsum material foamed by waste stone dust was designed and tested. The amount of stone dust, a waste product formed during the cutting and polishing of decorative stones, is becoming serious problem in some countries. When the stone dust contains calcium carbonate, it can be used for gypsum foaming to produce cheap, environmentally attractive material. The physical and mechanical properties of lightweight gypsum-based materials with different amounts of stone dust were designed and tested. The material with largest amount of waste stone dust attained a bulk density under 600 kg/m 3 and compressive strength of 1.1 MPa, with a thermal conductivity of 0.117 W/m.K. These properties are sufficient for use of the material as a thermal insulating plaster, as the core of thermal insulating gypsum boards or in lightweight blocks for inner walls and partitions. Life cycle cost analyses was performed for the most favourable material and was compared with aerated autoclaved concrete, which is a common commercial product with similar properties. Keywords Lightweight gypsum, lightening method, mechanical properties, thermal properties, waste stone dust, life cycle cost Date received: 10 July 2018; accepted: 2 January 2019 Introduction The fact that gypsum is one of the most ecologically favourable building binders makes large-scale utiliza- tion of calcined gypsum in the building industry highly desirable. The energy demand for gypsum pro- duction by calcination is low compared with the pro- duction of lime or cement because the gypsum calcination temperature (under 200  C) is substan- tially lower than the temperature during cement or lime production (over 1000  C). Another ecological advantage of gypsum also lies in the choice of its raw materials. Gypsum can be produced from natural gypsum rock, but can also be produced from a wide range of industrial by-products, e.g. from the flue gas desulfurization (FGD) of power plants (FGD gypsum) 1 and also from the production of phosphate fertilizers (phos- phogypsum), 2 of titan dioxide (red gypsum) 3 or citric acid (citrogypsum). 4 Gypsum also exhibits excellent fire-resistance, good workability and aesthetic properties. The main prob- lem associated with gypsum materials is the fact that gypsum can be used only in a dry environment, because it is slightly soluble and undergoes a substantial loss of strength when wet. This drawback could be solved by proper hydrophobization 5 or by the use of compound binders, e.g. with pozzolans. 6 In spite of the above-described advantages of gypsum, its use in the building industry is currently limited. Recently, calcined gypsum has mostly been used in gypsum boards (drywalls), for flooring (self- levelling floors), for interior plasters and, to a lesser extent, in the form of blocks. The use of lightweight gypsum-based products as a more ecological alterna- tive to lightweight cement-based materials is one of the ways in which gypsum use can be extended. Lightweight building materials are generally preferred at the present time because of their better thermal insulation properties, smaller dead load, attractive acoustic properties, better earthquake resistance and also lower transportation and placement costs. As a Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic Corresponding author: AVimmrova, Faculty of Civil Engineering, Czech Technical University in Prague, Thakurova 7/2077, Prague 6, 167 00 166 29, Czech Republic. Email: vimmrova@fsv.cvut.cz Proc IMechE Part L: J Materials: Design and Applications 0(0) 1–10 ! IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1464420719826163 journals.sagepub.com/home/pil