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Geopolymers offer increasingly better physico-mechanical properties concerning thermal exposure at high temperatures compared to ordinary Portland cements (OPC). This paper aims to comprehensively study the use of different types of fillers with different particle size distributions in terms of type (silica sands and cordierites) and surface area, loaded at different temperatures and dwell times (30 min and 180 min). After thermal exposure in the temperature range of 100–1000 °C, geopolymer samples were evaluated regarding physico-mechanical properties compared to samples without thermal exposure, using OPC as a reference material. Geopolymer samples were found to have a denser microstructure than OPC, supporting their better resistance to elevated temperature conditions. In addition, the influence of different filler compositions on the resulting internal structure and porosity was demonstrated. Samples containing fillers in two particle size ranges showed better densification than samples with one particle size range. Conversely, OPC samples showed the least favourable results. In addition, the mechanical behaviour of the geopolymers under static loading, especially in bending and compression tests, showed that the prepared geopolymers exhibited better properties than Portland cement at elevated temperatures, especially in the range of 500–1000 °C. In conclusion, appropriately designed geopolymer compositions have the potential to be a sustainable material, a high-performance alternative to traditional building materials. • Geopolymers (GP) with cordierite and silica sand exposed to 100–1000 °C were studied. • The physico-mechanical properties of the samples after thermal loading were investigated. • The results of the GP samples were compared with ordinary Portland cement (OPC) ones. • GP results suggest solid phase reactions and/or partial sintering at higher temperatures. • GP show better overall properties than OPC in the 500–1000 °C range. [ABSTRACT FROM AUTHOR]

• Acrylic latex additives were produced with and without keto-hydrazide crosslinking from standardly available low-cost raw monomers. • The results indicate that the highest effect on heat flow evolution changes has been detected in the case of latexes without crosslinking. • An important mitigation of liquid water transport properties of latex-modified composites has been achieved. • The developed latex cement-based composites may find utilization as special materials for structures or products for water-loaded constructions. Polymer-modified Portland-based composites are of interest for specific applications, in reason of their properties. There are different types of commercial additives and waste polymer-based materials applied to cement-based composites, however, their impacts on the environment are debatable. This work has prepared new acrylic latex additives with and without keto-hydrazide crosslinking from standardly available low-cost raw monomers. The influence of their incorporation into Portland cement-based fine-grained mortars has been investigated. The obtained results indicate that the highest effect on heat flow evolution changes has been detected in the case of latexes without crosslinking. The incorporation of both latex types into produced cement composites resulted in a significant increase in open porosity connected with the gradual decrease in mechanical resistance, especially the compressive strength. On the other hand, an important mitigation of liquid water transport properties of latex-modified composites has been achieved, and such properties can be tuned according to the used latex type and its concentration. The developed latex cement-based composites may find utilization as special materials for structures or products for water-loaded constructions or in areas with high concentrations of water-soluble salts or other pollutants. [ABSTRACT FROM AUTHOR]

• Designed eco-friendly polymer emulsions improved the properties of Magnesium cements. • Self-crosslinking is beneficial and exhibits synergistic effect with cement reaction. • More crystals, lower porosity, higher toughness, lower reaction rates, were obtained. In the context of reducing the environmental impact of cement manufacturing, magnesium phosphate cements raise interest as alternative binders in construction, for immobilization of wastes, and recycling purposes. Their use in applications is somehow limited by short setting time, brittleness and low water resistance; this calls for the use of additives. Two polymer additives were designed adopting emulsion polymerization, an environmentally friendly solution to make available polymers as water-based latex dispersions. The composites containing 5 wt% of polymer, exhibited better elastic behaviour, with up to twice the toughness of the reference sample and of a sample produced with commercial styrene-butadiene rubber latex. Moreover, the additives reduced the apparent porosity, promoted phosphate crystallization, modified the size and shape of crystals, and effectively retarded the reaction, extending working time. The acrylic emulsion developing keto-hydrazide self-crosslinking reaction imparted better properties to the composite, thanks to the synergistic effect with the MPC setting reaction. [ABSTRACT FROM AUTHOR]

• MSWI-FA is tested as either inert or reactive component in MKPC. • In both conditions, dissolution reactions involving Ca, Mg, S, Al, Si and Zn occur. • The precipitated secondary products are mostly amorphous phosphates. • The heavy metals leaching is below the Italian legal limits. • A 60% compressive strength increase is observed for the reactive formulation. In this study, the behaviour and reactivity of Municipal Solid Waste Incineration Fly Ash (MSWI-FA), introduced in the formulation of magnesium potassium phosphate cement (MKPC), was investigated by considering the waste either as fully inert or reactive. MSWI-FA induced structural and compositional modifications in MKPC as a consequence of dissolution/precipitation processes which involved many MSWI-FA elements (e.g., Ca, Mg, Al, Si, Zn) and led to the formation of mostly amorphous phosphate secondary products. The reaction path has been described in terms of the early fast dissolution of MSWI-FA, with precipitation of very low solubility phases, and subsequent late precipitation due to pH changes and water subtraction during MKPC gelification. The increase in amorphous content peaked to 50 wt.% and it has been related to the improved behaviour with respect to the leaching of heavy metals (reduced by 70-99%), pointing to this cement as an excellent matrix for their chemical stabilization. The obtained MKPC microstructure exhibited better mechanical performance, with an improvement of up to 60% in compressive strength. All in all, the results indicated that the incorporation in MKPC is a viable recycling opportunity for MSWI-FA, although, for an effective cement formulation, its reactivity must be taken into account. [ABSTRACT FROM AUTHOR]

[Display omitted] • The role of carbonized bio-based aggregate in the preparation of advanced lightweight concretes was investigated. • Honeycomb-like structure of BA particles was observed. • Lower BA additions up to 50 vol% allow to make concretes with sufficient strength for structural applications. • Highly thermal and acoustic insulating composites, suitable for building claddings, were prepared with BA content above 25 vol%. Concrete is the most utilized man-made building material and its global production reaching 25 billion tons per year represents a huge burden on our environment. Unsurprisingly, a lot of effort is dedicated to searching for suitable replacing materials of concrete constituents, e.g. of mineral aggregate that usually forms 70–80 vol% of fresh concrete mix, not only to reduce the depletion of our natural resources, but, at the same time, to improve some of the concrete properties. For example, dense building materials are not very effective in acoustic-insulation performance. In this context, renewable resources can provide a possible solution in the preparation of advanced concrete composites that will help to reduce noise originating in high populated urban and/or industrialized areas. This paper is focused on the application of carbonized lightweight bio-based aggregate (BA), having about 63 % lower thermal conductivity compared to the traditional ones, in the manufacturing of lightweight concretes which, related to BA quantity in mixes, dispose with considerably mitigated thermal transport properties and enhanced acoustic-insulation function. Traditional dense aggregate was replaced with the bio-based alternative in the amount of 0–100 vol% and the batch water content was adjusted to keep similar consistency (class S4) of fresh concrete mixes. After 28 days of water curing, the development of dry bulk density, open porosity, flexural and compressive strengths as well as thermal and acoustic performance in the dependence on bio-based aggregate content were determined on hardened specimens. Experimental investigation revealed significant lightening effect of BA particles having a honeycomb-like porous structure and thus promoting the high thermal and acoustic performance of developed concretes. Accordingly, hardened concrete samples with alternative aggregate content only showed 7.5 times lower thermal transport and about 16.2 % improved acoustic performance compared with ordinary dense concrete. In addition, lower BA dosages (up to 50 vol%) allowed to produce concretes disposing sufficient strength parameters – average flexural strength about 6.5 MPa and compressive strength about 27.0 MPa maintaining their usage for structural purposes. Furthermore, bio-based aggregates are sorted among renewable resources that may mitigate environmental impacts connected with the quarrying of traditional filling materials, and thus contribute to higher sustainability of concrete production. [ABSTRACT FROM AUTHOR]

• The waste incorporation up to 25 vol.% allows structural application of concrete. • Considerable lightening and high thermal performance of composites were observed. • Designed concretes may find usage for special filling and flooring applications. • The waste application mitigates negative environmental impacts. Intensive quarrying of natural non-renewable resources belongs to the actual topics related to the dynamically developing construction industry worldwide. However, at the same moment, an appreciable quantity of construction and demolition waste (CDW) is generated, from which the primacy to concrete, ceramic and masonry derived materials is attributed. These are already traditionally applied in concrete manufacturing as supplementing and filing materials due to their good recycling ability. Nevertheless, a number of material blends which separation is complicated or highly financial demanding still remain and thus burden our environment. This work has been aimed at the effective application of lightweight blended building waste (LBW) in the manufacturing of eco-friendly concretes. Concrete mixtures with the volumetric content 0–100% of the waste blend have been prepared. The influence of LBW on 28 days' water cured samples has been investigated with the application of a wide range of experimental procedures and various instrumental techniques. Performed tests revealed a substantial lightening effect of LBW – leading to hardened concretes with a unit weight of about 760 kg·m−3. On the other hand, a high rate of lightening caused considerable decrease in strength properties of produced composites. However, application of LBW up to 25% can be used to preserve usage of these blended concretes for construction applications. Other performed tests showed excellent thermal performance of waste aggregate enriched concretes, and thus these materials may find usage for special filling and flooring applications with minimum loading of bearing structures. [ABSTRACT FROM AUTHOR]