Abstract
The thermal conductivity and mechanical strength of gypsum and gypsum-cellulose plates made from commercial plaster by a new process have been measured. The gypsum parts made by the new process, 'novogesso', have high mechanical strength and low porosity. The gypsum strength derives from both the high aspect ratio of the gypsum crystals and the strong adhesion among them by nano-flat layers of confined water, which behaves as supercooled water. Another contribution to the strength comes from the nano-flatness of the lateral surfaces of the gypsum single crystals. The bending and compression strengths, σB and σc, of gypsum plates prepared by this new technique can be as high as 30 and 100 MPa, respectively. The way gypsum plates have been assembled as well as their low thermal conductivity allowed for the construction of a low-cost experimental house with thermal and acoustic comfort.
Highlights
DH, SO Ca.2H O crystals are derived from plaster, HH, SO4Ca.1/2H2O crystals by hydration according to the chemical equation: 2.0 (SO Ca.1/2H O)
This paper presents a new process for the preparation of high-strength and low-porosity gypsum plates together with their mechanical strength and thermal conductivity
Cellulose fibers are obtained from Eucalyptus wood, the same wood used for paper making (≈20 μm diameter and 2.0 to 3.0 mm length) and have been
Summary
DH, SO Ca.2H O crystals are derived from plaster, HH, SO4Ca.1/2H2O crystals by hydration according to the chemical equation: (SO Ca.1/2H O) +3.0 (H O) 2 → (SO Ca.2H O) (1). Gypsum crystals grow through the HH dissolution in water and the DH crystals seed and grow Such a process was already proposed by Le Chatelier[1] in 1883, it has always been thought that an excess of water would be needed to help the dissolution of plaster. The minimum mass ratio between water and the HH, W/HH, required for the full hydration of the HH mass, as given by the above equation, is 0.186, nearly 20% of water relative to the HH mass. Brazil has two sources of gypsum: one of mineral origin and phosphogypsum, derived from the phosphate production
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