Efeito da aplicação do poliestireno sulfonado (PSSNa) como aditivo em argamassas e concretos de cimento Portland CPV32

Abstract

Neste trabalho foi investigado o uso do Poliestireno sulfonado (PSSNa), produzido a partir de copos plásticos descartáveis de Poliestireno (PS), como aditivo em argamassas e concretos de cimento Portland CPV32. A avaliação do PSSNa como aditivo foi baseada em ensaios de fluidez e resistência mecânica à compressão de corpos de prova. Foi observado, em argamassas com relação água/cimento (a/c) de 0,48, um aumento na fluidez com o aumento das porcentagens de PSSNa (0,25 a 1,00%). A adsorção do PSSNa sobre as partículas de cimento melhora a dispersão dos componentes da argamassa, aumentando a resistência mecânica à compressão dos corpos de prova após a cura. A aplicação do PSSNa em concreto apresentou o mesmo efeito. O abatimento do concreto sem PSSNa foi de 50 mm, atingindo cerca de 200 mm com o uso do polieletrólito. Devido à elevada plasticização observada é possível empregar o PSSNa como aditivo redutor de água. Foi produzido um concreto com o mesmo abatimento da referência sem aditivo reduzindo-se a quantidade de água em 20,8%. O ganho de resistência mecânica à compressão obtido foi de 21,5 e 26,3 %, respectivamente aos 7 e 28 dias de cura. Estes resultados mostraram que soluções de PSSNa podem atuar eficientemente como aditivo superplastificante ou redutor de água em argamassas e concretos.

Mortar modified with sulfonated polystyrene produced from waste plastic cups

“…Even when there was an increase in admixture content of 1-1.4%, there was no increase in fluidity, showing that the admixture had already reached the optimum content, and that the increase fluidity of the mixture is purely attributed to admixture action, and not the water present in its solution. Note that the water/cement ratio has not changed; the increase in the consistency index is because the anionic long-chain molecules of the sulfonated polystyrene admixture became adsorbed on the surface of the cement particles that are effectively dispersed in water, as reported by Assunção et al [19] and Royer et al [20]. It was also observed that the mortar with SPS addition provided a cohesive aspect and more fluid than the reference mortar, as can be seen in Figure 3.…”

“…The sulfonated polystyrene (SPS) was produced from the sulfonation of polystyrene plastic cups discarded post-consumer, as per already defined procedures in previous research carried out by our group [19][20][21]. The sulfonation was carried out with concentrated sulfuric acid (H 2 SO 4 98%) and silver sulfate (Ag 2 SO 4 ) as a catalyzer.…”

“…There was an increase in the tensile strength in bending for all levels of admixture, reaching 23.72% for the A1.0 mortar. Therefore, even with low levels of SPS, the presence of polymer in the mortar appears to form a film on the microstructure of the paste, which tends to improve its tensile strength, as pointed out by Ohama [17], Assunção et al [19] and Royer et al [20].…”

“…Some commercial plasticizer admixtures or superplasticizers incorporated into concrete and mortar have the presence of the sulfonate group, chemically modified group, responsible for the strong interactions with cement particles. Furthermore, the sulfonate group increases the solubility of the polymer in water, resulting in better dispersion and homogeneity of the cement paste [19][20][21]. Polystyrene can be recycled for the production of new materials.…”

“…Polystyrene can be recycled for the production of new materials. In a previous work, the PS obtained from discarded cups and food trays was used for the production of ion-exchange membranes [5], in the water treatment as an auxiliary agent of coagulation, flocculation and flotation for water and wastewater treatment [1,18], and as an admixture to concrete with excellent results, such as increased workability and water reduction, being classified as a superplasticizer admixture [19][20][21]. The objective of this study was to examine the application of sulfonated polystyrene, obtained from discarded plastic cups, as an admixture in mortars.…”