Lightweight cement mortars: Advantages and inconveniences of expanded perlite and its influence on fresh and hardened state and durability

Lightweight aggregates are frequently incorporated in renders to control dry bulk density and workability. Expanded perlite leads to water:cement (w:c) ratios higher than normal, especially in renders whose w:c ratios are higher due to the addition of cellulose ethers. Initially, this paper looks at the effect that perlite has on fresh-state parameters considered of great importance in renders: mixing water, density, consistence, workability and water retentivity. In addition, the role of perlite in sorptivity, water absorption and mechanical strength is also reported. The experiments show that mechanical strength, sorptivity and water absorption are negatively affected above 1.77%, while workable life and water retentivity are generally improved. The study is finished by quantifying the effect of agents such as water, hydrochloric acid and sodium sulfate on renders made with perlite. The effects are quantified by mass loss/gain measurements, water absorption tests are visually inspected using scanning electronic microscopy.