Gypsum hydration: a theoretical and experimental study

Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building\ud material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs in two formations of α- and β-type. Among them β-hemihydrate is mainly used to produce gypsum plasterboard since the hydration product of the α-hemihydrate is too brittle to be used as building material /10/. This article addresses the hydration of hemihydrate since it determines the properties of gypsum and it is influenced strongly by water and the properties of hemihydrate. The microstructure development of gypsum during hydration is investigated. The influence of water is studied from its effect on fresh behavior and void fraction of the gypsum

The application of MSWI bottom ash fines in high performance concrete

In this study, the application of municipal solid waste incineration (MSWI) bottom ash fines (0-2 mm) as aggregate in high performance concrete is experimentally evaluated. The characteristics of bottom ash fines (BA) and sand are measured and compared. The bottom ash fines are used as sand replacement in the proportion of 10%, 20% and 30% by mass of sand; the properties of concrete are investigated. The influential factors of MSWI bottom ash fines on concrete properties are analyzed, and the further research orientation is addressed

Wood-wool cement board : potential and challenges

Wood-wool cement boards (WWCB) produced from Ordinary Portland Cement and spruce wood-wool since the beginning of 1920 are still widely applied. However, the question remains if this type of material is still feasible in the current market where both sustainability and durability perceive popularity. One of the reasons is the high CO2 footprint of cement production which contrasts to the increased environmental concern. This paper describes the potential of the WWCB in the current market, together with the challenges concerning the sustainability. Firstly, the motivation for this study is introduced. Secondly, the production process of the WWCB is reviewed. Thirdly, the available studies on the interaction between wood and cement, are summarized. Finally, the physical influence of an applied binder is discussed

Structural lightweight aggregates concrete

This paper addresses the development of a structural lightweight aggregates concrete (SLWAC), aiming at a good balance between a low specific density and thermal conductivity, and high mechanical properties. The mix design is performed by applying the modified Andreasen and Andersen model to secure a densely packed matrix, composed of a binder and lightweight aggregates. The water absorption of the applied lightweight aggregates, expanded clay, is studied and an effective water dosage is determined from the obtained results. The fresh behaviour test of the designed concrete shows an acceptable workability, under a water-cement dosage of 0.35. The developed SLWAC shows excellent thermal properties, with a low thermal conductivity of about 0.20 W/(m¿K); and moderate mechanical properties, with a 28-day compressive strength of about 34 MPa (class of LC30-33 according to EN 206-1), with an apparent density of about 1250 kg/m3. The significantly low thermal conductivity of the developed concrete under this strength class can find a wide application potential, both for structural and thermal insulating purposes