Abstract
Perlite, a natural pozzolan, was activated with NaOH to prepare alkali-activated (AA) intumescent pastes. After curing at 100°C for 3–24h, the solidified pastes had medium strengths, up to 40MPa, and low densities, ∼1500–2000kg/m3, compared to Portland cement pastes. Upon heating, volume expansion in the 200–600°C range resulted in a porous solid. Expansion occurs due to a loss of silanol condensation water, as vapor. Chemical composition of the pozzolan, activator content, and heat-treatment temperature influence the size and amount of pores formed. Mechanical, physical, and microscopic investigations were made. Volume increases up to 225% were measured. Densities decreased to as low as ∼450kg/m3 after heat treatment and cooling. Strengths of porous products were in the 3–7MPa range. Such materials able to intumesce over specific temperature ranges could be useful in applications where absorption of thermal energy is necessary, such as passive fire protection.
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