Maria Chiara Bignozzi

New polymer mortars containing polymeric wastes. Part 1. Microstructure and mechanical properties

Abstract Recycling industrial wastes as filler components and/or aggregates in polymer mortars makes these materials very interesting from an ecological and safety point of view. In addition, the resulting materials have useful physical and mechanical properties. Four recycled fillers (powdered rubbers, tyre rubbers, micronized tyre fibers and milled electrical cable wastes) have been used to formulate new polymer mortars. The comparison of their mechanical properties and microstructures with those of a plain polymer mortar indicates that the presence of recycled waste affects the physical–mechanical behavior (compressive and flexural strengths, microstructure). The use of silane coupling agents has been also considered and its effect in leading to more compact materials is reported and discussed.

New polymer mortars containing polymeric wastes. Part 2. Dynamic mechanical and dielectric behaviour

Abstract A promising application for polymer mortars and concretes is for machine tool structures: for this purpose, composite materials with good mechanical properties and high damping characteristics are required. Accordingly, four recycled fillers (powdered rubber, tyre rubber, micronized tyre fibres and milled electrical cable waste) have been used to formulate new polymer mortars. The internal energy dissipation and relaxation processes of the different materials, studied by the combined use of both dynamic mechanical and dielectric analysis, are compared thus showing the effect of the powdered rubber based filler as a damping promoter. The use of silane coupling agents has also been investigated and its effect in leading to stiffer materials is reported and discussed.

Hybrid Liquid-Crystalline Block Copolymers with Polystyrene and Polyester Blocks

SummaryThe synthesis and some thermal and dynamic-mechanical properties of a novel class of hybrid block copolymers comprised of polystyrene and liquid-crystalline polyester blocks are reported. The two blocks appear to be incompatible in the solid and melt phases and undergo distinct thermal transitions. The mesophase transition temperatures of the block copolymers are constant within all the composition range. The mesophase transition enthalpies are directly proportional to the weight fraction of the liquid-crystalline polyester block.

Matt waste from glass separated collection: An eco-sustainable addition for new building materials

Matt waste (MW), a by-product of purification processes of cullet derived from separated glass waste collection, has been studied as filler for self-compacting concrete and as an addition for newly blended cement. Properties of self-compacting concrete compared to reference samples are reported. They include characteristics at the fresh and hardened states, and the compressive strength and porosity of mortar samples that were formulated with increasing amounts of MW to be used as cement replacement (up to 50wt.%). The effects of matt waste are discussed with respect to the mechanical and microstructural characteristics of the resulting new materials.

Role of Recycled Concrete Aggregates on the Long-Term Behavior of Structural Concrete

The effects of coarse recycled concrete aggregates on long-term behavior of concrete (shrinkage and creep) are investigated. Most important, corresponding prediction models have been compared with experimental findings, obtaining a systematic underestimation of results. The adhered mortar of the recycled concrete aggregates is determined and its influence on the final concrete properties is investigated as its content and porosity can influence the final properties of the new concrete.

New Geopolymers Based on Electric Arc Furnace Slag

Electric arc furnace slag (EAF-S), coming from a steel productive plant in Italy, has been used as new source for geopolymers synthesis. The slag has been geopolymerized alone and with different content of metakaolin (MK) with the aim to investigate if EAF-S content plays a role in geopolymerization process. Mechanical properties results and microstructure analysis highlight that the optimum weight ratio MK/EAF-S to be used as starting materials is 40/60, 30/70, 20/80. Moreover EAF-S, when used with MK, directly participates in the formation of calcium-rich alumino-silicate gels.

Ceramic Waste as New Precursors for Geopolymerization

Geopolymers, and more in general alkali activated materials (AAM), are a new class of materials obtained by alumino-silicates precursors activated by means of alkaline solutions. Indeed, the term geopolymers is usually strictly referred to pure alumino-silicates such as metakaolin as starting material, whereas when the precursors also contain calcium oxide the resulting products are usually defined AAM. Geopolymerization technology can be more easily considered a sustainable process when industrial waste is used as precursors and the consolidation process occurs at room temperature. With these premises, alkali activation may be a very promising technology for the ceramic sector as well as construction industry. In this work, waste coming from bricks production has been used to obtain, at room temperature, geopolymers with different porosity tuning the sodium silicate content in the feed. Microstructure analysis carried out by means of mercury intrusion porosimeter and scanning electron microscopy is reported and discussed.

The Influence of Short Fibres and Foaming Agents on the Physical and Thermal Behaviour of Geopolymer Composites

Foaming methods to reduce the density of geopolymers were investigated as low density geopolymers are increasingly being reported in the literature to be effective in improving the insulating properties. However, there is no consistency in foaming methods and as such this study was performed to compare different foaming agents in order to better understand their effect on the properties of geopolymers. In particular, a surfactant and hydrogen peroxide were used individually and in combination to ensure a homogeneous pore distribution in the slurry. Physical and microstructural properties of the hardened low density geopolymers are presented and discussed. The behaviour under fire conditions of fibre reinforced and foamed geopolymer samples will also be presented in order to appreciate the suitability of geopolymer composite in high temperature applications.

Binders alternative to Portland cement and waste management for sustainable construction—part 1:

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Lead waste glasses management: Chemical pretreatment for use in cementitious composites:

This article investigates the effect of a low-impact chemical treatment based on a nitrilotriacetic acid chelating agent on the reactivity of funnel glass derived from discarded cathode ray tubes. Treated and untreated glass has been recycled either as a supplementary cementing material or as a fine aggregate in cementitious mortars. The effect of the treatment on the chemical and morphological properties of cullets, as well as on the solubility in an alkaline environment has been evaluated. Data so far collected underline a change in glass cullets characteristics that consequently affects their behaviour in cementitious mortars, reducing the pozzolanic activity as supplementary cementing material, but strongly decreasing the tendency towards alkali silica reactions when added as a fine aggregate. The leaching behaviour of lead on treated and untreated glass and on derived composites has been determined to verify the sustainability of the prepared materials.