Properties and Utilization of Zeolite-Blended Portland Cements

Abstract

The resistance to acidic and sulfate attack of Portland-pozzolan cement containing 35 wt.% of zeolite was compared with that of unamended Portland cement. Mortar specimens kept in 0.5% and 1.0% HCl solution, 5% Na2SO4 solution, and in reference water for 365 and 720 days were tested using a set of physical-mechanical and chemical techniques. The ability of mortars containing zeolitic cements with 15 to 50 wt.% of zeolite to protect steel against corrosion was verified by a potentiodynamic method. Mortar with zeolitic cement performs better when exposed to 1% HCl solution due to the presence of a finer pore matrix, a hydrate phase poorer in CaO-containing hydration products with lower leachability, and the high resistance of zeolite material itself to acidic attack, compared with Portland cement and siliceous sand. The improved sulfate resistance of the mortar with zeolitic cement is caused by the decreased C3A in the cement blend in comparison with that in Portland cement, a reduction in SO3 binding into the cement paste and decreased amount of CaO-containing hydration products capable of reacting with a sulfate solution forming voluminous reaction products, and consequent crack propagation, large expansion and structural disintegration. Passivation of steel in mortars with blends of Portland cement to zeolite percentage ratios of 85/15, 75/25 and 65/35 by weight is comparable to that of Portland cement mortar. This is particularly important because the mortar with zeolitic cement exhibits late strengths similar to that of Portland cement mortar. This confirms that zeolitic cement can replace Portland cement in many applications with the advantage of higher resistance to acidic and sulfate attack.

The Impact of Thermocycling Process on the Dislodgement Force of Different Endodontic Cements

“…On the other hand, additives such as zeolite which is a crystalline hydrated aluminosilicate of alkaline metals and metals of alkaline soils (Ca, K, Na, and Mg) can act as an additive stabilizer agent in Nano-WMTA cement. This substance also has an anticorrosive behavior against sulfate which is responsible for sulfate attack occurring through the reaction of Portland cement [29]. This issue can explain the significant differences between the push-out bond strength values of Nano-WMTA with MTA and Bioaggregate, respectively.…”

Soil mix technology for land remediation: recent innovations

“…Zeolites exhibit relatively high permeability which makes them suitable for flowthrough applications and have hence been studied and applied in groundwater remediation systems, such as PRB, as well as the immobilisation of contaminants in soils (Erdema et al, 2004;Mozgawa and Bajda, 2005;Oste et al, 2002;Park et al, 2002). Zeolites have recently been blended with PC as they have been shown to offer strength as well as durability advantages over PC alone (Janotka and Stevula, 1998;Janotka et al, 2003). Work has also been conducted on the effect of zeolite in cement-based deep mixing of clays on mechanical performance, permeability and durability (Osman, 2007;Osman and Al-Tabbaa, 2006).…”

Sustainable binders for soil stabilisation

“…Zeolites blended with PC have been shown to offer enhanced strength as well as durability over PC alone in concrete (Feng et al, 1992;Janotka et al, 2003, Perraki et al, 2003 based on the following: (a) the highly porous structure of zeolite provides large reaction surfaces for the interaction with portlandite hence consuming it; (b) zeolite in a cement matrix produces a hydration phase which contains less portlandite and less Ca-rich C-S-H reducing leachability; (c) zeolite produces a finer pore matrix in cement paste, reducing the permeability; and (d ) zeolite has a higher pozzolanic activity than commonly used pozzolans offering much improved durability. The expected significant enhancement in technical performance will lead to a significantly increased lifespan of construction products.…”

“…The performance of PC in some aggressive environments is poor, mainly due to the leaching of calcium; first the portlandite (which is highly soluble and highly reactive) dissolves and then the calcium silicate hydrate gel (C-S-H) is decalcified leading to its degradation. Hence there are efforts to produce binders with significantly enhanced durability (Harrison, 2003;Higgins, 2005;Janotka et al, 2003;Sear, 2007). This paper presents some of the mechanical properties and durability performance obtained using a number of PCblended binders, which are considered more sustainable than PC, in the stabilisation of a range of soils.…”