BAUHAUS-UNIVERSITÄT WEIMAR

Milieu-dependent effect of retardants on hydrating calcium sulphate binders

To meet technical and economic requirements, calcium sulphate binders must exhibit varying properties. Especially in respect of the open processing time and the setting time, the binders must be adjustable in a time period from a few minutes to several hours. To meet these requirements, the use of additives to regulate setting is necessary [1]. Objective of this work was to characterize the effect of selected retardants on a plaster of Paris paste as a function of the pH value (adjusted with NaOH).

1 Introduction

Mallon [2] has defined the retardation factor as the quotient of the start of setting of gypsum plaster paste containing a retardant to the start of setting of a gypsum plaster paste without a retardant. The corresponding pH value was adjusted with an alkali or acid. The milieu-dependent effect is illustrated in Figure 1.

Reul [3] established in his investigations that selected retardants (application concentrations 0.03… 0.1 % relative to the binder mass) have a different effect with different calcium sulphate binders. For instance, DL malic acid, citric acid and mesotartaric...

Related articles:

Issue 2017-7-8 Bauhaus-Universität Weimar

Additive-dependent effects on plaster ­hydration

1 Introduction Among calcium sulphate binders, building plasters in particular, plaster of Paris, or gypsum plaster, is the most well-known and often used. Plaster of Paris is a partially calcined...

more
Issue 2017-6 SIKA SERVICES AG

The spice of gypsum

1 Background Gypsum boards are produced from gypsum plaster, water and additives for the gypsum core as well as cardboard on continuous conveyor lines. Prior to diving into the chemistry of gypsum...

more
Issue 2017-5 THIRD WEIMAR GYPSUM CONFERENCE, WEIMAR/GERMANY

Gypsum (not) only for construction

In his welcoming address, Hans-Bertram Fischer pointed out that gypsum has a very wide range of applications. One of the organizers’ prime concerns, therefore, was to create a forum for a broad...

more
Issue 2021-5 MENDELEEV UNIVERSITY OF CHEMICAL TECHNOLOGY | BAUHAUS-UNIVERSITÄT WEIMAR

Composite gypsum binders with improved water resistance

1 Introduction In recent years the domestic industry has been in need of environmentally friendly and safe construction materials that can be produced at minimum energy consumption. These materials...

more
Issue 2009-03 Materials Science

Acceleration of the setting of hemihydrate plaster with calcium sulfate dihydrate

1 Introduction Calcium sulfate binders are required to have widely varying properties to meet technical and economic requirements. In particular, it has to be possible to vary the workability time and...

more