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

Properties of alkali activated slag-fly ash blends with limestone addition

In this article, the effects of raw materials’ composition on fresh behavior, reaction kinetics, mechanical properties and microstructure of alkali activated slag–fly ash–limestone blends are investigated. The results indicate that, with the increasing content of fly ash and limestone, the slump flow increases. The setting times are shortened when increasing the slag content, while both fly ash and limestone show a negligible influence. The reaction process is slightly accelerated by the presence of limestone due to the extra provided nucleation sites, but the reaction process is mainly governed by the slag. The slag content exhibits a dominant role on strength in this ternary system, while for a constant slag content, the compressive strength increases with the increasing limestone content up to 30%. The microstructure analysis shows that the gel characteristics are independent of the limestone powder content. The presence of limestone in initially high Ca and Al conditions does not lead to the formation of additional crystalline phases, which is different from Portland cement systems. Both physically and chemically bound water contents are slightly increased when limestone powder is incorporated

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