Durability of Concrete Containing Calcined Clays: Comparison of Illite and Low-Grade Kaolin

CORDOBA, GISELA P.; ZITO, SILVINA; TIRONI, ALEJANDRA; RAHHAL, VIVIANA F.; IRASSAR, EDGARDO F.

RILEM Bookseries

Springer

Año: 2020 vol. 25 p. 631 - 640

2211-0844

Calcined clays have been proved as supplementary cementitious materials with good pozzolanic properties. Currently, its use in concrete mixes is promoted to reduce CO2 emissions from the cement industry, but sustainable concrete requires the performance of fresh and hardened concrete to be better, or at least equivalent, than portland cement concrete. Furthermore, durability is a critical factor.In this paper, durability parameters (water sorptivity, water penetration, chloride penetration and natural carbonation) are studied on conventional mix-tures (w/cm=0.50). Concretes were elaborated with portland cement (PCC) and blended portland cements, containing 25% replacement by illitic calcined clay (ICC) and low grade kaolinitic calcined clay (KCC). They were characterized by slump, compressive and tensile strengths, and bulk porosity. Water sorptivity (ASTM C 1585) was determined on concretes cured 2, 7 and 28 days; water penetration test (EN 12390) and chloride penetration (ASTM C 1556) were de-termined on concretes cured 28 days. Carbonation depth undergoing a good and very good curing was assessed using a phenolphthalein indicator at 3 and 6 months of natural exposition.Results show that water sorptivity is reduced when concrete is curing for 2, 7 and 28 days for all concretes. KCC has a significantly lower sorptivity than PCC and ICC. At 28 days, the water penetration is deeper for ICC and lower for KCC concrete. All concretes have similar apparent chloride diffusion coefficients. After six months, the natural carbonation of all concretes is less than 2 mm, with a slightly lower performance of ICC and KCC than PCC.