Study of the pozzolanic activity and hydration products of cement pastes with addition of natural zeolites

Abstract

This paper presents results from comparative thermogravimetric, calorimetric and pozzolanic activity analyses of five natural zeolite samples from Bulgaria, Slovakia, Philippines, USA and North Korea. The zeolites actively participate in the hydration processes of cement. Their activity in the early stage of hydration is based mainly on the large surface area of the particles while, in the later stages of activation, chemical reactions occur between the products of the hydration of cement and the soluble SiO2 that is present in the bulk of the zeolites. It has been shown that in all cement pastes which contain zeolite additives, the quantity of portlandite is lower than that in pure cement paste or is even totally absent. The amounts of hydration products are greater when 30% zeolite is used than when 10% zeolite is added (excluding the sample with chabazite). The lowest pozzolanic activity is shown by chabazite, which possessed the lowest SiO2/Al2O2 ratio.

The effect of acid treatment on the reactivity of natural zeolites used as supplementary cementitious materials

“…Prior research has shown natural zeolites to be feasible for use as supplementary cementitious materials (SCMs), replacing a portion of the cement in concrete while still generating similar or improved concrete properties [1][2][3][4]. Natural zeolites have also been shown to be pozzolanic, reacting with portlandite (calcium hydroxide) and water in cementitious systems to create more C-S-H [2,5]. Zeolites improve many concrete properties when included as part of the cementitious binder including resistance to alkali silica reaction, sulfate attack, and penetration by chlorides [3,4].…”

Influence of Natural Zeolite on Portland Cement Hydration Processes and Properties of Hardened Cement Paste

“…According to literature sources, hydrated zeolite and cement blends have lower Ca(OH) 2 contents and smaller amounts of calcium aluminate (C 3 A) hydration products [27] than hydrated OPC. XRD patterns described in research papers, especially the development of Ca(OH) 2 peaks, propose a new way of stimulating cement hydration (in the presence of fillers) [28].…”

Cimentos Portland aditivados com arenito zeolítico com propriedades pozolânicas

“…Pelo fato do arenito ser uma pozolana de baixa reatividade, acredita-se que as argamassas com teores de 20 e 30% de incorporação continuarão a apresentar desenvolvimento de resistência ao longo de tempo. Trabalhos anteriores constataram que as zeólitas de baixa reati-vidade são capazes de combinar com a portlandita até a idade de 365 dias [14]. Diante, parte da hipótese que a argamassa com teor de 10% de arenito possa suplantar a de referência para idades mais avançadas.…”