Agriculture Reference
In-Depth Information
will determine key properties such as porosity and hardness, thus dictating
the physical and chemical resistance of the material. The nature of their raw
materials, as well as their firing temperature and firing process affects greatly
the final mineralogical composition, porosity, and durability of the material,
and therefore the final quality of the brick. In general, high temperatures
and/or long firing periods will result in a harder, less porous, and more vitre-
ous brick.
It is, therefore, considered essential to determine the mineralogical compos-
ition and texture of the brick, with a particular focus on the presence, nature
and arrangement of the mineral cements, in order to understand the proper-
ties of the rubbing brick in relation to durability. To this end, petrographic
microscopy and X-ray diffractometry (XRD) were used.
Furthermore, since moisture is directly responsible for many decay processes
and mineral reactions that induce hardening, the presence and movement of
moisture within the brick were considered important factors. Porosity, water
absorption and water suction were therefore measured in order to characterise
the moisture transport properties of the rubbing brick.
Methods
In the first instance, ten samples of rubbing brick from a variety of locations in
England and continental Europe, dating from the seventeenth to the twenti-
eth century (Table 6) were analysed (Pavia and Lynch, 2003).
All analyses and testing were carried out at Trinity College Dublin, the
Dublin Institute of Technology and Loughborough University.
Thin sections were made from the samples and petrographic examination
was carried out using both natural and polarised transmitted light.
The mineral composition of the samples was determined by XRD.
The presence and movement of water within the brick samples was deter-
mined by measuring the rate of water uptake (suction) of a dry brick and the
amount of water that the brick could hold (absorption). The amount of water
absorbed by each sample was determined by comparing the wet mass of the
sample to its dry mass.
The volume of pore space in the brick samples (porosity) was also measured.
Open porosity, or porosity accessible to water, is the ratio of the volume of the
accessible pores to the bulk volume of the sample.
Results and Discussion
The mineralogical compositions of the bricks are given in Table 7.
From the results, the analysed rubbing bricks can be divided in to two main
groups: those that contain calcium-bearing minerals (diopside and wollastonite)
