Warm applied Mortar (WAM) – An insight into the historical technique of “Heiße Speis” and its use for renders

Author(s): Robert Wacha, Farkas Pintér
Paper category: Proceedings
Book title: Proceedings of the 5th Historic Mortars Conference
Editor(s): José Ignacio Álvarez, José María Fernández, Íñigo Navarro, Adrián Durán, Rafael Sirera
ISBN: 978-2-35158-221-3
e-ISBN: 978-2-35158-222-0
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 579-584
Total Pages: 6
Language : English

Abstract: The method of using dry slaked mortar while it is still hot or warm (warm applied
mortar, WAM) originates mainly from an oral tradition amongst craftsmen in Austria,
describing the method as “the hot matter” (“Heiße Speis” in German). For this
purpose, mortar was not left to rest but used immediately after the mixing process and
ongoing slaking reaction. To test this seemingly unconventional technique under field
conditions quicklime and local river sand was dry slaked in boxes, mixed and used
warm to render a chapel ́s façade. During the application the “WAM” showed
surprisingly good workability and good state of preservation even after harsh winters.
Render samples from the test site were analysed after seven years of exposition. SEM
images showed signs of a characteristic structure of shrinkage cracks. The paper shows
the first results of practical tests of producing and working with warm applied mortar
and the experience with this special technique.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00