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The production of cement, the predominant construction binder, is associated with high energy consumption, enormous raw material depletion, and a large volume of CO2 emissions, making cement one of the most polluting materials. This study aims to contribute to the sustainability of the construction industry by significantly reducing the proportion of Portland cement (PC) in the composition of mortars. The binder content reduction was achieved by the addition of large amounts of fly ash admixture (FA) from lignite combustion while studying the effectiveness of the immobilization of heavy metals (HMs), which are present in FA, in the PC/FA matrix. Along with the analysis of the FA admixture amount on the properties of the prepared mortars, emphasis was put on the study of the influence of prolonged curing on the development of the physical parameters of the mortars and the immobilization efficiency of the HMs. It was revealed that FA can be added to PC by up to 20 wt%, enabling the production of construction mortars with high strength and low porosity, while confining hazardous substances such as HMs in the matrix. Prolonged curing at elevated relative humidity led to the continuous evolution and solidification of the mortar structure, improving its engineering properties and HMs immobilization efficiency.

In the steel industry, a large amount of diverse waste is generated, including carbon-bonded magnesia-rich waste originating from refractories. This study focused on the development and characterization of composite material based on magnesium oxychloride cement (MOC), with an emphasis on incorporating MgO–C-based refractory waste (CBMW) as a sustainable filler. To reach the best possible material properties, two different size fractions were applied in various ratios, completely replacing quartz sand. A comprehensive analysis of all composite material samples was conducted utilizing various analytical techniques, XRD, SEM, EDS or STA-MS. Mechanical properties such as compressive strength, flexural strength, and Young's modulus of elasticity were evaluated. Even though even the best sample did not surpass the mechanical properties for the reference, compressive strength 78.1 MPa was achieved, which is a more than sufficient value for most indoor applications.

Materials for the conservation of cultural heritage must meet specific demands, such as high durability, service life, and compatibility with other materials used in the original building structures. Due to their low permeability to water and water vapor and their high rigidity, the use of Portland cement (PC) mortars, despite their high mechanical resistance and durability, does not represent an appropriate solution for the repair of historic masonry and structures. Their incompatibility with the original materials used in the past, often on a lime basis, is therefore a serious deficiency for their application. On the other hand, lime-based mortars, compared to PC-based materials, are more susceptible to mechanical stress, but they possess high porosity, a high water vapor transmission rate, and moderate liquid water transport. This study aims at the development of two types of lime-based mortars, calcium lime (CL) and hydraulic lime (HL). The modification of mortars was conducted with a carbon-based nanoadditive and graphene nanoplatelets (GNs) in three dosages: 0.1%, 0.3%, and 0.5% of the binder weight. The enhancement of CL mortars by GNs greatly increased mechanical strength and affected heat transport characteristics, while other characteristics such as porosity, water absorption, and drying rate remained almost similar. The application of GNs to HL not only enhanced the strength of mortars but also decreased their porosity, influenced pore size distribution, and other dependent characteristics. It can be concluded that the use of graphene nanoplatelets as an additive of lime-based composites can be considered a promising method to reinforce and functionalize these composite materials. The improved mechanical resistance while maintaining other properties may be favorable in view of the increasing requirements of building materials and may prolong the life span of building constructions.

A reduction in cement consumption can be achieved through the use of supplementary cementitious materials (SCMs). In addition, the utilization of more than one SCM can show a beneficial synergic performance. In this paper, a combination of calcium aluminate cement, alumina admixtures and one other type of SCM was investigated. Namely: microsilica, ferrite powder, ceramic dust, calcined shale and sintered mullite were employed. The phase compositions of the designed binders were primarily characterized by XRD, XRF, DSC and SEM. Subsequently, the basic physical and mechanical properties as well as thermal expansion of the ternary binder-based composites up to 1400 °C were determined. The results revealed the synergic performance of used components. Calcined shale and ceramic powder were the most promising admixtures, exhibiting compressive strength of 80 MPa at room temperature and 117 and 128 MPa for ceramic powder and calcined shale, respectively, after exposure to 1400 °C.

The excellent technical parameters of magnesium oxychloride cement (MOC) and its ability to sequester CO2 from the environment predestine its use as an alternative to Portland cement. However, its main shortcomings, low water resistance, and excessive water absorption need to be addressed to enable its wider application in construction. For this reason, the improvement of the water resistance of MOC-based composites through the use of nanosized molybdenum disulfide (MoS2) is the subject of this case study. The MOC-based composites were subjected to experimental testing of their chemical, structural and physical parameters using a wide range of advanced laboratory techniques. The composites enriched by MoS2 nanoadditive exhibited a densified and compact structure with improved mechanical parameters and stiffness. Water transport and storage were significantly decelerated and reduced by the incorporation of MoS2 nanoparticles, resulting in an improvement of water resistance, characterized by the softening coefficient, which was 66.1 % after 24 h of immersion in water, which is about 13.8 % higher than that of the reference MOC-based composite.

The Portland cement (PC) industry is a big producer of CO2 – a major contributor to the global warming. As the world tends to reduce the CO2 emissions because of its negative effect, a sustainable and efficient PC alternative is needed to be found. One of the most promising substitute is based on reactive magnesia – magnesium oxychloride cement (MOC). This paper deals with the design, development, and characterization of environmentally friendly composites based on MOC. In addition to the standard quartz sand filler, carbon spheres-based waste produced by polypropylene treatment via plasma gasification was used as a nanoadditive. Before the preparation of the composites themselves, the carbon spheres (CS) were analysed with a wide range of analytical methods in order to determine their microstructure and composition. The CS were used in the amount of 0.5, 1.0, and 3.0 wt% related to the weight of the pure MOC paste. The prepared composite samples were tested for their microstructure, phase and chemical composition, micro- and macrostructural parameters, and mechanical properties after 28 days of maturing. Furthermore, the influence of CS on the hygric properties and the water resistance of the MOC-based composites were studied after 24 h-long immersion in water. It has been shown, that with the increasing amount of CS, the mechanical parameters improve quite rapidly, making CS an enhancing eco-friendly nanoadditive. It was also shown, that CS helps to slow down water transport in MOC-based composites, which is a key aspect in the improvement of their water resistance and overall durability after exposure to humidity. The incorporation of carbon spheres-based waste as a nanoadditive in MOC-based composites shows promising improvements in mechanical properties and water resistance, contributing to the development of environmentally friendly construction materials.

To solve heat energy storage of building enclosure systems, phase change materials (PCMs) were implemented into magnesium oxychloride cement (MOC) to form a MOC-PCM composite. Such composites possess sufficient mechanical strength for specific usage and high heat storage efficiency. The chemical and physical properties of raw materials were investigated as well as fresh composite mixture rheology. On matured samples, structural, mechanical, hygric, and thermal properties were tested. The results suggest that the enrichment of MOC with PCM particles causes an increase in porosity, hence a decrease in the specific density of the composites. With each addition of PCM the reduction of mechanical properties of the composite material occurs, where the maximum reduction in flexural and compressive strength for the sample with 40 wt % of PCM is around 80%. The low strength of the composite is compensated by excellent thermal properties that are required for its intended application. The enthalpies of phase changes increased linearly with the dosage of PCM and can contribute to the passive moderation of temperature fluctuations. The developed composites can find use in building engineering in the form of indoor cladding panels, facing slabs ceiling boards, etc. Which can be beneficially applied for example in the passive cooling of attic rooms and retrofitting of the present building stock.

Nowadays, many researchers are intensively trying to develop novel environmentally friendly composite materials for construction with a view to replace widely used Portland cement (PC). Current hopes are pinned on the use of materials based on reactive magnesia. In this case study, composites prepared from magnesium oxychloride cement (MOC), ground waste glass, and either quartz sand or foam glass were prepared and analyzed in detail. The main aim was to design and develop novel composites with low unit weight, good thermal insulation performance, and high water damage resistance. In addition, the application of secondary-raw materials as a partial substitution for common fillers was accented. The properties of fresh and matured composites were studied and analyzed within the framework of a complex experimental campaign involving phase composition assessment, structural, textural, mechanical, hygric, thermal, and durability parameters testing, as well as the identification of main chemical bonds in the formed hardened materials. The usage of ground waste glass led to a significant drop in porosity, densified microstructure, enhanced compressive strength, reduced water ingress, and improved durability. In general, the prepared composites provide properties and performance, which make them promising eco-efficient alternatives to PC-based construction composites.

Heavy metal contamination, associated with the increase in industrial production and the development of the population in general, poses a significant risk in terms of the contamination of soil, water, and, consequently, industrial plants and human health. The presence of ecotoxic heavy metals (HMs) thus significantly limits the sustainable development of society and contributes to the deterioration of the quality of the environment as a whole. For this reason, the stabilization and immobilization of heavy metals is a very topical issue. This paper deals with the possibility of the simultaneous immobilization of heavy metals (Ba2+, Pb2+, and Zn2+) in mortar based on magnesium potassium phosphate cement (MKPC). The structural, mechanical, and hygric parameters of mortars artificially contaminated with heavy metals in the form of salt solutions were investigated together with the formed hydration products. In the leachates of the prepared samples, the content of HMs was measured and the immobilization ratio of each HM was determined. The immobilization rate of all the investigated HMs was >98.7%, which gave information about the effectiveness of the MKPC-based matrix for HM stabilization. Furthermore, the content of HMs in the leachates was below the prescribed limits for non-hazardous waste that can be safely treated without any environmental risks. Although the presence of heavy metals led to a reduction in the strength of the prepared mortar (46.5% and 57.3% in compressive and flexural strength, respectively), its mechanical resistance remained high enough for many construction applications. Moreover, the low values of the parameters characterizing the water transport (water absorption coefficient Aw = 4.26 × 10−3 kg·m−2·s−1/2 and sorptivity S = 4.0 × 10−6 m·s−1/2) clearly demonstrate the limited possibility of the leaching of heavy metals from the MKPC matrix structure.

To solve the problem with the landfilling of waste ash coming from wood chips combustion and to develop construction composites with moderate strength and improved thermal performance, enriched wood chips ash/magnesium oxychloride lightweight composites were designed and thoroughly characterized. As the demand for the thermal effective materials composed of sustainable raw precursors remains a challenge, foamed glass produced from waste glass was used as lightweight aggregate. The experimental analysis of the prepared composites included assessment of phase composition, micro- and macrostructural parameters, mechanical strength, hygric properties, heat transport and storage parameters. The replacement of silica sand with foamed glass enabled the development of materials with high porosity and mechanical strength, moderate water absorption capacity rate, lowered thermal conductivity and high heat storage capacity. As the flexural and compressive strength of the lightened composites remained high, it was possible to further improve thermal insulation performance of the composites by the higher dosage of lightweight aggregate in composite mixture. The wood chips ash greatly improved the mechanical strength of the lightened composites and enabled the development of construction materials with lower environmental damage. The ash acted both as fine filler and reactive material positively influencing the formation of hydration products. The acquired data and results evince that an interesting alternative to Portland cement-based composites were obtained.

The topic of modification of magnesium oxychloride cement (MOC) using specific functional additives is very much pronounced in the research of alternative building materials. This study deals with the co-doping of MOC by 1D and 2D carbon nanomaterials in order to improve its mechanical properties while using tannic acid (TA) as a surfactant. Furthermore, the effect of TA on MOC also improves its water resistance. As a filler, three size fractions of standard quartz sand are used. The proposed types of MOC-based composites show promising results considering their mechanical, macro- and microstructural, chemical, and hygric properties. The use of 1D and 2D nanoadditives and their mixture enables the improvement in the flexural strength and particularly the softening coefficient, which is the durability parameter characterizing the resistance of the prepared materials to water. After immersion in water for 24 h, the compressive strength of all tested specimens of modified composites was higher than that of the reference composite. Quantitatively, the developed co-doped composites show mechanical parameters comparable to or even better than those of commonly used Portland cement-based materials while maintaining high environmental efficiency. This indicates their potential use as an environmentally friendly alternative to Portland cement-based products.

In past years, the study of magnesium oxychloride cement became fairly widespread, because of its good mechanical properties and environmental sustainability. One of its biggest advantages is its ability to work well with different types of fillers and aggregates. This paper deals with the synthesis and analysis of such material, namely the composite of magnesium oxychloride with diatomite. Three different phases varying in the amount of diatomite were prepared and analyzed using various analytical methods, namely X-ray diffraction, X-ray fluorescence, simultaneous thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The phase and chemical composition, morphology and thermal behavior were studied as well as the structural, mechanical, hygric, and thermal properties of the hardened materials. This sort of novel and alternative material shows wide-ranging application potential while being eco-friendly and providing great mechanical properties applicable in the extreme conditions.

In this study, three industrial by-products (ultrafine fly ash, ground granulated blast-furnace slag (ggbs) and circulating fluidized bed co-fired fly ash) were used to produce ternary cementless composites without using alkali activators. The finenesses of ultrafine fly ash, ggbs and co-fired fly ash were 33,800, 5830 and 5130 cm2/g, respectively. The composite material was developed by mixing supplementary cementing materials of different particle sizes and exploiting the high-alkaline properties of the co-fired fly ash to develop a substantial hardening property like cement. The test specimens were made in the form of pastes and the water-to-cementitious-material ratio for the test was fixed at 0.55. The test results show that the flowability of the six different mixtures could be up to 120% and the setting time could be controlled within 24 h. At 60% of the ggbs proportion, the setting time could be held for 8 h. The compressive strength of each proportion reached 7 MPa at 7 days and 14 MPa at 28 days. The water-cured specimens exhibited better strength behavior than the air-cured specimens. Scanning electron microscopy found the main components of strength growth of the specimens to be hydrated reactants of C-A-S-H or ettringite. The results of the XRF analysis show that the specimens responded to higher compressive strengths as the Ca/Si and Ca/Al ratios increased.

The presented research is focused on the complex assessment of three different types of diatomaceous earth and evaluation of their ability for application as pozzolana active admixtures applicable in the concrete industry and the production of repair mortars applicable for historical masonry. The comprehensive experimental campaign comprised chemical, mineralogical, microstructural, and physical testing of raw materials, followed by the analyses and characterization of pozzolanic activity, rheology and heat evolution of fresh blended pastes, and testing of macrostructural and mechanical parameters of the hardened 28-days and 90-days samples. The obtained results gave evidence of the different behavior of researched diatomaceous earth when mixed with water and Portland cement. The differences in heat evolution, initial and final setting time, porosity, density, and mechanical parameters were identified based on chemical and phase composition, particle size, specific surface, and morphology of diatomaceous particles. Nevertheless, the researched mineral admixtures yielded a high strength activity index (92.9% to 113.6%), evinced their pozzolanic activity. Three fundamental factors were identified that affect diatomaceous earth’s contribution to the mechanical strength of cement blends. These are the filler effect, the pertinent acceleration of OPC hydration, and the pozzolanic reaction of diatomite with Portland cement hydrates. The optimum replacement level of ordinary Portland cement by diatomaceous earth to give maximum long-term strength enhancement is about 10 wt.%., but it might be further enhanced based on the properties of pozzolan.

In this study, the combined effect of graphene oxide (GO) and oxidized multi-walled carbon nanotubes (OMWCNTs) on material properties of the magnesium oxychloride (MOC) phase 5 was analyzed. The selected carbon-based nanoadditives were used in small content in order to obtain higher values of mechanical parameters and higher water resistance while maintaining acceptable price of the final composites. Two sets of samples containing either 0.1 wt. % or 0.2 wt. % of both nanoadditives were prepared, in addition to a set of reference samples without additives. Samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive spectroscopy, which were used to obtain the basic information on the phase and chemical composition, as well as the microstructure and morphology. Basic macro- and micro-structural parameters were studied in order to determine the effect of the nanoadditives on the open porosity, bulk and specific density. In addition, the mechanical, hygric and thermal parameters of the prepared nano-doped composites were acquired and compared to the reference sample. An enhancement of all the mentioned types of parameters was observed. This can be assigned to the drop in porosity when GO and OMWCNTs were used. This research shows a pathway of increasing the water resistance of MOC-based composites, which is an important step in the development of the new generation of construction materials.

The studies focusing on magnesium oxychloride cement (MOC) composites have recently become fairly widespread because of MOC’s excellent mechanical properties and environmental sustainability. Numerous fillers, admixtures and nano-dopants were studied in order to improve the overall performance of MOC-based derivatives. Some of them exhibited specific flaws, such as a tendency to aggregate, increase in porosity, aeration of the composite matrix, depreciation in water resistance and mechanical strength, etc. In this manuscript, MOC-based composites doped by multi-walled carbon nanotubes (MWCNTs) are designed and tested. In order to modify the final properties of composites, diatomite was admixed as partial substitution of MgO, which was used in the composition of the researched material in excess, i.e., the majority of MgO constituted part of MOC and the rest served as fine filler. The composites were subjected to the broad experimental campaign that covered SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), HR-TEM (high-resolution transmission electron microscopy), XRD (X-ray diffraction), OM (optical microscopy) and STA-MS (simultaneous thermal analysis with mass spectroscopy). For 28 days hardened samples, macrostructural and microstructural parameters, mechanical properties, hygric and thermal characteristics were experimentally assessed. The incorporation of MWCNTs and diatomite resulted in the significant enhancement of composites’ compactness, mechanical strength and stiffness and reduction in water absorption and rate of water imbibition. The thermal properties of the enriched MOC composites yielded interesting values and provided information for future modification of thermal performance of MOC composites with respect to their specific use in practice, e.g., in passive moderation of indoor climate. The combination of MWCNTs and diatomite represents a valuable modification of the MOC matrix and can be further exploited in the design and development of advanced building materials and components.

Rendering mortars with lightweight zeolite aggregates were designed and tested. The effect of the type of binder used was also researched. For the hardened mortars, macrostructural parameters, mechanical characteristics, hygric and thermal properties were assessed. Specific attention was paid to the analysis of the salt crystallization resistance of the developed rendering mortars. Quartz sand was fully replaced in the composition of mortars with zeolite gave materials with low density, high porosity, sufficient mechanical strength, high water vapor permeability and high water absorption coefficient, which are technical parameters required for repair rendering mortars as prescribed in the WTA directive 2-9-04/D and EN 998-1. Moreover, the zeolite enhanced mortars exhibit good thermal insulation performance and high sorption capacity. The examined rendering mortars were found to be well durable against salt crystallization, which supports their applicability in salt-laden masonry. Based on the compatibility of the repair materials with those originally used, the lime and natural hydraulic lime zeolite mortars can be used as rendering mortars for the repair of historical and heritage buildings. The cement-lime zeolite render is applicable for repair purposes only in the case of the renewal of masonry in which Portland cement-based materials were originally used.

Three types of lightweight plasters for building repair were prepared and tested. The composition of plasters was designed in respect to their compatibility with materials used in the past in historical masonry. For the hardened plasters, detailed testing of microstructural and macrostructural parameters was realized together with the broad experimental campaign focused on the assessment of mechanical, hygric, and thermal properties. As the researched plasters should find use in salt-laden masonry, specific attention was paid to the testing of their durability against salt crystallization. The mechanical resistance, porosity, water vapor transmission properties, and water transport parameters of all the researched plasters safely met criteria of WTA directive 2-9-04/D and standard EN 998-1 imposed on repair mortars. Moreover, the tested materials were ranked as lightweight plasters and due to their low thermal conductivity they can be used for the improvement of thermal performance of repaired masonry. The salt crystallization test caused little or no damage of the plasters, which was due to their high porosity that provided free space for salt crystallization. The developed plasters can be recommended for application in repair of damp and salt masonry and due to their compatible composition also in historical, culture heritage buildings. The added value of plasters is also their good thermal insulation performance.

The ongoing tendency to create environmentally friendly building materials is nowadays connected with the use of reactive magnesia-based composites. The aim of the presented research was to develop an ecologically sustainable composite material based on MOC (magnesium oxychloride cement) with excellent mechanical, chemical, and physical properties. The effect of the preparation procedure of MOC pastes doped with graphene nanoplatelets on their fresh and hardened properties was researched. One-step and two-step homogenization techniques were proposed as prospective tools for the production of MOC-based composites of advanced parameters. The conducted experiments and analyses covered X-ray fluorescence, scanning electron microscopy, energy-dispersive spectroscopy, high-resolution transmission electron microscopy, sorption analysis, X-ray diffraction, and optical microscopy. The viscosity of the fresh mixtures was monitored using a rotational viscometer. For the hardened composites, macro- and micro-structural parameters were measured together with the mechanical parameters. These tests were performed after 7 days and 14 days. The use of a carbon-based nanoadditive led to a significant drop in porosity, thus densifying the MOC matrix. Accordingly, the mechanical resistance was greatly improved by graphene nanoplatelets. The two-step homogenization procedure positively affected all researched functional parameters of the developed composites (e.g., the compressive strength increase of approximately 54% after 7 days, and 37% after 14 days, respectively) and can be recommended for the preparation of advanced functional materials reinforced with graphene.

Lightweight Sorel’s cement composites doped with coal fly ash were produced and tested. Commercially available foam granulate was used as lightening aggregate. For comparison, reference composites made of magnesium oxychloride cement (MOC) and quartz sand were tested as well. The performed experiments included X-ray diffraction, X-ray fluorescence, scanning electron microscopy, light microscopy, and energy dispersive spectroscopy analyses. The macro- and microstructural parameters, mechanical resistance, stiffness, hygric, and thermal parameters of the 28-days matured composites were also researched. The combined use of foam glass and fly ash enabled to get a material of low weight, high porosity, sufficient strength and stiffness, low water imbibition, and greatly improved thermal insulation performance. The developed lightweight composites can be considered as further step in the design and production of alternative and sustainable materials for construction industry.

In this contribution, composite materials based on magnesium oxychloride cement (MOC) with multi-walled carbon nanotubes (MWCNTs) used as an additive were prepared and characterized. The prepared composites contained 0.5 and 1 wt.% of MWCNTs, and these samples were compared with the pure MOC Phase 5 reference. The composites were characterized using a broad spectrum of analytical methods to determine the phase and chemical composition, morphology, and thermal behavior. In addition, the basic structural parameters, pore size distribution, mechanical strength, stiffness, and hygrothermal performance of the composites, aged 14 days, were also the subject of investigation. The MWCNT-doped composites showed high compactness, increased mechanical resistance, stiffness, and water resistance, which is crucial for their application in the construction industry and their future use in the design and development of alternative building products.

A high-performance magnesium oxychloride cement (MOC) composite composed of silica sand, diatomite powder, and doped with graphene nanoplatelets was prepared and characterized. Diatomite was used as a 10 vol.% replacement for silica sand. The dosage of graphene was 0.5 wt.% of the sum of the MgO and MgCl2·6H2O masses. The broad product characterization included high-resolution transmission electron microscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy analyses. The macrostructural parameters, pore size distribution, mechanical resistance, stiffness, hygric and thermal parameters of the composites matured for 28-days were also the subject of investigation. The combination of diatomite and graphene nanoplatelets greatly reduced the porosity and average pore size in comparison with the reference material composed of MOC and silica sand. In the developed composites, well stable and mechanically resistant phase 5 was the only precipitated compound. Therefore, the developed composite shows high compactness, strength, and low water imbibition which ensure high application potential of this novel type of material in the construction industry.

In this paper, light burned magnesia dispersed in the magnesium chloride solution was used for the manufacturing of magnesium oxychloride cement-based composites which were lightened by granulated scrap tires and expanded glass. In a reference composite, silica sand was used only as filler. In the lightened materials, granulated shredded tires were used as 100%, 90%, 80%, and 70% silica sand volumetric replacement. The rest was compensated by the addition of expanded glass granules. The filling materials were characterized by particle size distribution, specific density, dry powder density, and thermal properties that were analyzed for both loose and compacted aggregates. For the hardened air-cured samples, macrostructural parameters, mechanical properties, and hygric and thermal parameters were investigated. Specific attention was paid to the penetration of water and water-damage, which were considered as crucial durability parameters. Therefore, the compressive strength of samples retained after immersion for 24 h in water was tested and the water resistance coefficient was assessed. The use of processed waste rubber and expanded glass granulate enabled the development of lightweight materials with sufficient mechanical strength and stiffness, low permeability for water, enhanced thermal insulation properties, and durability in contact with water. These properties make the produced composites an interesting alternative to Portland cement-based materials. Moreover, the use of low-carbon binder and waste tires can be considered as an eco-efficient added value of these products which could improve the environmental impact of the construction industry.

Worldwide, Portland cement-based materials are the most commonly used construction materials. As the Portland cement industry negatively affects the environment due to the excessive emission of carbon dioxide and depletion of natural resources, new alternative materials are being searched. Therefore, the goal of the paper was to design and develop eco-friendly, low-cost, and sustainable magnesium oxychloride cement (MOC)-based building material with a low carbon footprint, which is characterized by reduced porosity, high mechanical resistance, and durability in terms of water damage. To make new material eco-efficient and functional, silica sand which was used in the composition of the control composite mixture was partially replaced with coal fly ash (FA), a byproduct of coal combustion. The chemical and mineralogical composition, morphology, and particle morphology of FA were characterized. For silica sand, FA, and MgO, specific density, loose bulk density, and particle size distribution were measured. Additionally, Blaine specific surface was for FA and MgO powder assessed. The workability of fresh mixtures was characterized by spread diameter. For the hardened MOC composites, basic structural, mechanical, hygric, and thermal properties were measured. Moreover, the phase composition of precipitated MOC phases and their thermal stability were investigated for MOC-FA pastes. The use of FA led to the great decrease in porosity and pore size compared to the control material with silica sand as only filler which was in agreement with the workability of fresh composite mixtures. The compressive strength increased with the replacement of silica sand with FA. On the contrary, the flexural strength slightly decreased with silica sand substitution ratio. It clearly proved the assumption of the filler function of FA, whereas its assumed reactivity with MOC cement components was not proven. The water transport and storage were significantly reduced by the use of FA in composites, which greatly improved their resistance against moisture damage. The heat transport and storage parameters were only slightly affected by FA incorporation in composite mixtures.

Today, low-energy and low-carbon footprint alternatives to Portland cement are searched because of huge CO2 emissions coming from Portland clinker calcination. Because of some superior properties of magnesium oxychloride cement (MOC) and the lower carbon footprint of its production, MOC became an intensively studied material with high application potential for the design and development of construction products. In this contribution, magnesium oxychloride with stoichiometry 5Mg(OH)2∙MgCl2∙8H2O (Phase 5) was prepared and characterized. The kinetics of formation and the phase composition of the material were determined using X-ray diffraction and consequent Rietveld analysis. The morphology was studied by scanning electron microscopy, and the chemical composition was determined by both energy-dispersive spectroscopy and X-ray fluorescence. Moreover, the simultaneous thermal analysis in combination with mass spectroscopy and Fourier-transform infrared spectroscopy was employed to study the thermal stability. Using mass spectroscopy, we were able to clarify the mechanism of water and hydrochloric acid release, which was not previously reported. The observed structural and chemical changes induced by exposure of studied samples to elevated temperatures were linked with the measured residual macro and micro parameters, such as bulk density, specific density, porosity, water absorption, compressive strength, and pore size distribution. The Phase 5 revealed a needle-like crystalline morphology which formed rapidly and was almost completed after 96 h, resulting in relatively high material strength. The four-day compressive strength of magnesium oxychloride cement was similar to the 28-day compressive strength of Portland cement. The thermal stability of Phase 5 was low as the observed disruptive thermal processes were completed at temperatures lower than 470 °C.

In this paper, crushed lava granulate was used as full silica sand replacement in composition of repair mortars based on hydrated lime, natural hydraulic lime, or cement-lime binder. Lava granules were analyzed by X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Particle size distribution of both silica and lava aggregates was assessed using standard sieve analysis. Hygrothermal function of the developed lightweight materials was characterized by the measurement of complete set of hygric, thermal, and structural parameters of the hardened mortar samples that were tested for both 28 days and 90 days cured specimens. As the repair mortars must also meet requirements on mechanical performance, their compressive strength, flexural strength, and dynamic Young’s modulus were tested. The newly developed mortars composed of lava aggregate and hydrated lime or natural hydraulic lime met technical, functional, compatibility, and performance criteria on masonry and rendering materials, and were found well applicable for repair of historically valuable buildings.

Mechanically-activated wood-based biomass ash (WBA) was studied as a potential active admixture for design of a novel lime-pozzolan-based mortar for renovation purposes. The replacement ratio of lime hydrate in a mortar mix composition was 5%, 10%, and 15% by mass. The water/binder ratio and the sand/binder ratio were kept constant for all examined mortar mixes. Both binder constituents were characterized by their powder density, specific density, BET (Brunauer−Emmett−Teller), and Blaine specific surfaces. Their chemical composition was measured by X-ray fluorescence analysis (XRF) and mineralogical analysis was performed using X-ray diffraction (XRD). Morphology of WBA was investigated by scanning electron microscopy (SEM) and element mapping was performed using an energy dispersive spectroscopy (EDS) analyzer. The pozzolanic activity of WBA was tested by the Chapelle test and assessment of the Portlandite content used simultaneous thermal analysis (STA). For the hardened mortar samples, a complete set of structural, mechanical, hygric, and thermal parameters was experimentally determined. The mortars with WBA admixing yielded similar or better functional properties than those obtained for traditional pure lime-based plaster, pointing to their presumed application as rendering and walling renovation mortars. As the Chapelle test, STA, and mechanical test proved high pozzolanity of WBA, it was classified as an alternative eco-efficient low-cost pozzolan for use in lime blend-based building materials. The savings in CO2 emissions and energy by the use of WBA as a partial lime hydrate substitute in mortar composition were also highly appreciated with respect to the sustainability of the construction industry.

The goal of the paper was development and testing of a novel type of ternary blended binder based on lime hydrate, metakaolin, and biomass ash that was studied as a binding material for production of lightweight mortar for renovation purposes. The biomass ash used as one of binder components was coming from wood chips ash combustion in a biomass heating plant. The raw ash was mechanically activated by grinding. In mortar composition, wood chips ash and metakaolin were used as partial substitutes of lime hydrate. Silica sand of particle size fraction 0–2 mm was mixed from three normalized sand fractions. For the evaluation of the effect of biomass ash and metakaolin incorporation in mortar mix on material properties, reference lime mortar was tested as well. Among the basic physical characterization of biomass ash, metakaolin and lime hydrate, specific density, specific surface, and particle size distribution were assessed. Their chemical composition was measured by X-Ray fluorescence analysis (XRF), morphology was examined using scanning electron microscopy (SEM), elements mapping was performed using energy dispersive spectroscopy (EDS) analyser, and mineralogical composition was tested using X-Ray diffraction (XRD). For the developed mortars, set of structural, mechanical, hygric, and thermal properties was assessed. The mortars with ternary blended binder exhibited improved mechanical resistance, lower thermal conductivity, and increased water vapor permeability compared to the reference lime mortar. Based on good functional performance of the produced mortar, the tested biomass ash could potentially represent a novel sustainable alternative to other pozzolans commonly used in construction industry. Moreover, reuse of biomass ash in production of building materials is highly beneficial both from the environmental and economic reasons especially taking into account circular economy principles. The ternary blended binder examined in this paper can find use in both rendering and walling repair mortars meeting the requirements of culture heritage authorities and technical standards.

Polypropylene (PP) is one of the most widely produced types of plastic worldwide, but its recycling is limited. This work presents a study of the utilization of expanded polypropylene (EPP) waste in a magnesium oxychloride cement (MOC) composite usable in the building industry. MOC is formed by mixing magnesium oxide powder and a concentrated solution of magnesium chloride and is characterized by excellent bonding ability to large quantities of different types of aggregates. A developed air-cured MOC composite, where an EPP-based aggregate was used for the full replacement of natural aggregate, was investigated in terms of its basic physical, mechanical, thermal and water resistance properties. The results demonstrate that incorporation of EPP waste greatly improved the thermal insulation properties, while the mechanical resistance was reduced to an acceptable level. The developed MOC composite containing EPP waste can be considered as an alternative thermal insulation material applicable for the construction of floor or envelope construction systems.