In the last years many studies have been addressed on the development of new types of cement with the aim to find a sustainable alternative to traditional ordinary Portland cement. Alkali-activated materials (AAM) seem particularly attractive for this purpose, even if effective admixtures such as plasticizers still need to be designed limiting so far the diffusion of AAM for geopolymer concrete preparation. AAM come from the alkali-activation of aluminosilicate powders with suitable amorphous content. Among all the suitable aluminosilicate precursors, great interest is nowadays focused on the possibility to activate industrial waste (e.g., slag or fly ash). The use of waste as precursors, along with a room temperature curing, makes these materials low-polluting binders potentially suitable for green building products. The purpose of this paper is to study the influence of different superplasticizers on the AAM properties. In particular, first, second and third generation superplasticizers (i.e., lignin-, naphthalene-, melamine-, polycarboxylic ether-, and acrylic based superplasticizers) have been used for the preparation of carbon fly ash pastes and mortars in order to improve their physical and mechanical properties at the fresh and hardened state. Different amounts were tested with the aim to determine the best concentration. The results are then compared with those of reference AAM prepared without any admixture addition. Among the investigated admixtures, the mix with the polycarboxylic ether based plasticizer has the best behavior in terms of both fresh and hardened state properties. The optimum amount of SP corresponds to a dosage of 1% by mass of fly ash. Test results show an increase in terms of workability of both geopolymeric pastes and mortars in comparison with AAM samples without any admixture addition. Moreover the use of polycarboxylic ether based superplasticizer does not compromise the final strength of hardened material.
Study of the influence of different admixtures on the properties of alkali-activated materials
MANZI, STEFANIA;CARABBA, LORENZA;BIGNOZZI, MARIA
2015
Abstract
In the last years many studies have been addressed on the development of new types of cement with the aim to find a sustainable alternative to traditional ordinary Portland cement. Alkali-activated materials (AAM) seem particularly attractive for this purpose, even if effective admixtures such as plasticizers still need to be designed limiting so far the diffusion of AAM for geopolymer concrete preparation. AAM come from the alkali-activation of aluminosilicate powders with suitable amorphous content. Among all the suitable aluminosilicate precursors, great interest is nowadays focused on the possibility to activate industrial waste (e.g., slag or fly ash). The use of waste as precursors, along with a room temperature curing, makes these materials low-polluting binders potentially suitable for green building products. The purpose of this paper is to study the influence of different superplasticizers on the AAM properties. In particular, first, second and third generation superplasticizers (i.e., lignin-, naphthalene-, melamine-, polycarboxylic ether-, and acrylic based superplasticizers) have been used for the preparation of carbon fly ash pastes and mortars in order to improve their physical and mechanical properties at the fresh and hardened state. Different amounts were tested with the aim to determine the best concentration. The results are then compared with those of reference AAM prepared without any admixture addition. Among the investigated admixtures, the mix with the polycarboxylic ether based plasticizer has the best behavior in terms of both fresh and hardened state properties. The optimum amount of SP corresponds to a dosage of 1% by mass of fly ash. Test results show an increase in terms of workability of both geopolymeric pastes and mortars in comparison with AAM samples without any admixture addition. Moreover the use of polycarboxylic ether based superplasticizer does not compromise the final strength of hardened material.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
