Title
Composition of mortar as a function of distance to the brick-mortar interface: A study on the formation of cured mortar structure in masonry using NMR, PFM and XRD
Author
Brocken, H.J.P.
Larbi, J.A.
Pel, L.
van der Pers, N.M.
TNO Bouw
Publication year
1999
Abstract
The formation of cured mortar structure in masonry was studied using multiple experimental techniques. Starting with fresh mortar, nuclear magnetic resonance (NMR) was used to measure the water extraction during brick laying. After curing, the composition of cured mortar was investigated with polarizing and fluorescent microscopy (PFM) and X-Ray diffraction (XRD). Two typical mortars were investigated: a cement-lime mortar and a cement mortar with air entraining agent. The measurements indicate that the mortar composition (i.e. the contents of sand, cured binder and voids) and the contents of chemical substances of the cured binder (i.e. the contents of calcite and portlandite) change with distance to the brick-mortar interface. For the cement mortar with air entraining agent, the observations are explained by the enrichment of binder towards the brick-mortar interface, resulting from the local compaction and compression of the fresh mortar. In the cement-lime mortar such an enrichment of binder hardly occurs and the observations are explained by the intense carbonation that takes place. As a result, the chemical composition of the binders is very much different in both mortars. In the cement mortar with air entraining agent, near the brick-mortar interface the enrichment of cement and the low water content (resulting from the low water retentivity of this mortar), lower the water-to-cement ratio and as a consequence the cement is not fully hydrated. In the cement-lime mortar, because the Ca(OH)2 content and the water content is higher, near the brick-mortar interface, a carbonated zone is formed which is hardly permeable for CO2 (and probably water). The latter does not occur in the cement mortar, it remains permeable. The analysis of the experimental results have lead to the formulation of a conceptual model for the formation of cured mortar structure in masonry. Such a model may be helpful in analyzing the predicting the durability of mortars.
Subject
Architecture and Building
Binders
Brick
Carbonation
Curing
Interfaces (materials)
Mechanical permeability
Mortar
Nuclear magnetic resonance spectroscopy
Optical microscopy
X ray diffraction analysis
Air entraining agents
Polarizing-fluorescent microscopy (PFM)
Masonry construction
To reference this document use:
http://resolver.tudelft.nl/uuid:02eed6cf-1504-4f47-a816-b1fc6c0f15f3
TNO identifier
280438
Publisher
Delft Univ of Technology, Delft, Netherlands
ISSN
0046-7316
Source
Heron, 44 (4), 257-270
Bibliographical note
7th Euroseminar on Microscopy Applied to Building Materials, Delft University of Technology, Delft, The Netherlands, June 29-July 2 1999
Document type
article