RESUMO
In the direction of reducing greenhouse emissions and energy consumption related to the activities of the cement and concrete industry, the increasingly popular concept of eco-sustainability is leading to the development and optimization of new technologies and low impact construction materials. In this respect, geopolymers are spreading more and more in the cementitious materials field, exhibiting technological properties that are highly competitive to conventional Portland concrete mixes. In this paper, the mix design, mechanical properties, microstructural features, and mineralogical properties of geopolymer mixes are discussed, investigating the influence of the main synthesis parameters (curing regime, type of precursors, activator molarity, mix design) on the performance of the final product. Moreover, recent developments of geopolymer technology based on the integration of functional nanofillers are reported. The novelty of the manuscript is to provide a detailed collection of past and recent comparative studies between geopolymers and ordinary Portland concrete mixes in terms of strength properties, durability, fire resistance, and environmental impact by LCA analysis, intending to evaluate the advantages and limitations of this technology and direct research towards a targeted optimization of the material.
RESUMO
The recycling of waste tires is of paramount importance for environmental protection and for economic reasons. The number of scrapped tires in the United States has reached 550 million per year and is still rising. Even higher numbers are estimated in the European Union, reaching 1 billion tires per year. Disused tires create waste with a highly negative environmental impact. Tire disposal mainly involves highly polluting treatments (e.g. combustion processes to produce fuel oil), with only a small percentage of waste (3% to 15%) destined for less-invasive treatments such as powdering. In this article we will look at previous studies in which different amounts of waste tire powder are combined with cement concrete mixtures to provide a final product with mechanical properties suitable for engineering applications. Previous work has shown that a good compressive strength can be achieved through replacing 30% of powdered tire with crushed sand. First, as the percentage of aggregation between crumb rubber and crushed sand increases, compressive strength decreases. Second, aggregation replacement of crumb rubber and crushed sand shows a reduction in density at around 10%. Third, the modulus of elasticity depends on the percentages added: the more rubber added to concrete, the less elastic the product will be. In addition, a less tough concrete means higher strength. However, adding rubber to concrete increases the toughness.1.
