Abstract

The chemical resistance or durability of Portland cement pastes (PS0) incorporating natural Perlite rock (PT) against the aggressive attack of 4% MgSO4 solution up to 12 months were investigated. Results showed that water of consistency and setting times (initial and final) are elongated. The compressive strength slightly improved during the early ages of immersion only up to three months with the blank cement batch (Pp0), but up to 4, 5, 6 and 7 months with cement batches (Pp1-Pp4) containing 5, 10, 15 and 20wt%PT, respectively and then decreased. Thereafter, certain deleterious or detrimental reactions started till forming high levels of ettringite and/or gypsum. These new phases are responsible for the decrease of compressive strength. Both combined water and total sulfate contents increased with time of immersion up to 12 months but decreased with PT content if compared with those of the blank (Pp0). The blank cement pastes (Pp0) recorded the highest values of total sulfate content, i.e. it is very sensitive to SO42- ions. At the end of the 12th month of immersion, the SO42- ions only precipitated on the external and lateral surfaces of the hardened cement pastes, and some horizontal minor cracks and little deformation could be seen on the edges of specimens with samples containing PT, whilst large swelling was noted with cement pastes of the blank (Pp0).

Keywords: OPC; PT;Sulfate attack;Strength;Ettringite;Gypsum;Sulfate content