Mortar Composites Research Articles

Dating of mortars from Kastelli Hill, Chania, Crete, Greece, based on their compositional analyses

Abstract The study of mortars plays a crucial role in determining the chronology of construction phases. According to the database of mortars analysed from historical monuments in Crete and other areas of Greece, significant differences in mortar composition are observed across historical periods. In the present study, 14 mortars from Kastelli Hill and Katre Street in Chania, originating from the fortified wall and neighboring buildings, are analysed. The physico-chemical and mineralogical analysis aims at clarifying the nature of mortars, their manufacturing technology, and, in particular, to compare different construction phases. In addition, comparing historically identified mortars with those under study reveals similarities and differences across construction phases. The indicators considered include the trace elements of aggregates and binder, the characteristics of aggregate grain size, the type of binder (hydraulic or aerial), and the presence of pozzolanic additives. The comparisons indicated that the mortars from the wall were manufactured during the Roman period, since they are successfully compared with the mortars of buildings dating back to that time. Graphical abstract

Experimental study on the flexural behavior of ferrocement slab panels with supplementary cementitious silica fume and fiber materials

Ferrocement is a composite construction material with slender sections or panels, a rich cementitious mortar, and steel wire mesh as its principal reinforcing agent. The mortar matrix is designed to achieve optimal strength, density, impermeability, and workability, minimizing void formation and preventing map cracking. A study evaluated the workability and flexural strength of mortars prepared using three types of fine aggregates: Badarpur sand, Yamuna River sand, and Kilned Brick Powder. The mortar classifications included conventional mortar compositions (MCS), mortars with flyash and Silica Fume (MFSS), and mortars with flyash, silica fume, and human hair (MFSHS). The results showed that mixes incorporating these materials significantly improved workability, with MFSS-2 (Portland cement, Yamuna sand, plus 10% FA and 6% SF) showing the highest increase (42.50%). The high-strength formulations with supplementary materials were superior in terms of stiffness and structural integrity, with MFSHS-1 (Portland cement, Badarpur sand, 10% FA, 6% SF, and 1% HH fiber) showing the least deflection for any given load. The addition of 1% human hair fibers in the mortar matrix improved flexural strength in panels, acting as micro-reinforcements, enhancing the tensile strength alongwith mortar ductility.

The Characterization of Properties of Hard Historical Renders

Abstract Rendering materials combine two fundamental functions – create protective layers on a substrate and provide decorative and architectural appear of a building’s facade. In particular, many historical buildings are unique with their facades due to the incorporation of different decorative elements, such as plinths, lining cronies, reliefs etc. The composition of mortars used for renders contained many different components in view of binders and filler materials in the past. This fact in combination with conditions which are facades exhibited (weathering, increased moisture and others) effect their appear and overall durability. This paper is focused on the collection procedure of historical renders from two buildings located in the South bohemian region, and further the description and discussion of physical and mechanical properties of rendering materials samples are provided. These pilot data showed that one of examined buildings to some repairs were subjected historically, and for the second one partially different materials from the point of in their quality were used, although the outer facade layer (stucco) was uniform. The mapping of historical renders properties is essential for obtaining important data set for formulation of compatible composites intended for renovation interventions and local repairs.

Enhancing mortar composite matrices with three-dimensional auxetic truss lattice materials for reinforced concrete structures

Auxetic architected materials have been at the forefront of developing materials with a wide range of negative Poisson’s ratios, tunable stiffness, and high ductility due to their novel deformation under uniaxial compression. Despite that, the adoption of auxetic materials in load-bearing applications has been challenged by the requirement that their bulk modulus is significantly less than that of the fully dense parent material. In this paper, we study whether using the same mechanism that provides a negative Poisson’s ratio can be mimicked in an interpenetrating phase composite to enhance its matrix’s peak strength and mechanical behavior. In this case, a brittle matrix can be enhanced with a small volumetric fraction of an auxetic truss lattice. The auxetic phase behaves as reinforcement, increasing the hydrostatic compression and confinement in the matrix caused by the externally applied load and bridging matrix cracking. Our work is focused on rapidly prototyping composites using a concrete/mortar matrix with 15-5 PH stainless steel auxetic truss lattice reinforcement. The families of re-entrant bowtie and double pyramid truss lattices were manufactured using laser powder bed fusion to study the effects of increasing the confinement pressure when embedded in composite mortar/steel matrices. The results of the experimental program with LPBF-manufactured truss lattices tested under axial compression embedded in mortar composites are presented and discussed. Analytical modeling is used to decompose the effects of stiffness and Poisson’s ratio on the confining pressure generated by the reinforcing phase. Numerical results on a perfectly bonded periodic unit cell of the composite material are illustrated, presenting the auxetic confinement pressures for different characteristic angles of the architectures with a maximum increase in confining pressure of 34.4%. Our findings reveal significant enhancements in ductility and peak strength using the proposed scheme, with gains reaching up to 240% and 165%, respectively, when compared to conventionally confined specimens and a non-rule-of-mixtures behavior in the composite.

Improving Interlayer Adhesion of Cementitious Materials for 3D Construction Printing

The popularity of additive technologies in construction is increasing every year. At the same time, there are still a significant number of unresolved issues in this area related to the complexity of ensuring uniformity of printing due to technical difficulties with the mortar. One of the main issues is the adhesion of printed layers. This is especially true for continuing the printing process after it has been suspended with the formation of a cold joint. The authors consider the possibility of improving the technological properties of 3D construction printing (3DCP) mortars by introducing redispersible polymer powders (RPPs) and surface-active substances (SASs) into their composition. A comprehensive analysis of the effectiveness of various RPPs and SASs was carried out using standard testing methods to identify the most effective options and combinations of admixtures depending on their structure and mechanism of action. Laboratory tests of the mortar composition for 3DCP using the selected RPPs and SASs were carried out with the imitation of the formation of a cold joint. The most effective combination of RPPs and SASs was used to create the mortar for making the form-forming element using a construction 3D printer. Based on the results of the tests, the patterns of RPPs and SASs influence on the adhesive strength of such mixtures were determined.

Improving the strength and reliability of mortar composites with zeolite substitution

Clinoptilolite zeolite, a naturally occurring pozzolan, is a viable supplemental cementitious material (SCM) for reducing the carbon footprint generated by the cement industry. While previous literature has explored the use of natural zeolite as an SCM for cement composites, this investigation advances understanding on the effectiveness of natural zeolites as an SCM in three phases. In Phase I, two distinct forms of zeolite (Z1 and Z2) in relative mineralogical compositions and particle sizes were incorporated into mortar composites to replace ordinary Portland cement (OPC) at concentrations up to 20 wt% and characterized over a period of 28 days. Based on the superior performance of the higher clinoptilolite content zeolite (Z2), it was used in Phase 2 to evaluate the effect of zeolite substitution. In Phase 3, the reliability of the resultant composites prepared with Z2 were assessed using Weibull statistics. The inclusion of Z2 type zeolite at #200 mesh size and 10 % concentration yielded compressive strength and reliability comparable to the OPC control mortar at day 7, but significantly greater strength and reliability from day 14 onward. Porosity detailed by microCT suggests that increasing zeolite content to 15 % and greater results in unreacted zeolite that is detrimental to strength. The findings further establish the merits of natural zeolite as an SCM material and distinguish what is necessary for further improvements in mechanical properties of zeolite cement composites.

Hygrothermal characterization of cement mortar composites incorporating micronized miscanthus fibers

This work investigates both the moisture dependence of thermal properties and the hygric behavior of cement mortars incorporating different proportions of micronized miscanthus fibers up to ∼7 wt%. The experimental program encompasses thermal characterization at dry (10 % RH), moderate (50 % RH), and saturated (100 % RH) states of samples, along with hygric characterization of the various mortar specimens through sorption-desorption tests, water vapor permeability assessment, Moisture Buffer value (MBV) determination, and capillary absorption tests. Thermal measurements showed a significant decrease in thermal conductivity with the addition of fibers. For a given biobased mortar composition, conductivity values were almost identical at dry/moderate RH level but exhibited an increase at saturation. This shift was attributed to the fibers' absorptive properties, which lead to a higher water content within the samples in saturated humidity environments. Collectively, the moisture sorption, moisture buffering capacities, water vapor permeability, and capillary absorption properties demonstrated consistent enhancement with rising fiber content, confirming the significant impact of plant fibers on the material's hygrothermal properties. In addition, the GAB model (Guggenheim- Anderson- de Boer) was used to fit the sorption and desorption isotherms, yielding a good correspondence with experimental data. Finally, mortars with the higher fiber contents (M7.5 F and M10F with 5.70 wt% and 6.94 wt% of fibers, respectively) combined high hygroscopicity and low thermal conductivity values (even under moisture-saturated conditions), making them promising candidates for applications requiring both good hygric performance and effective insulation properties.

Experimental study of advanced phase change materials to optimise the thermal storage performance of radiant floors: Towards a low-carbon energy system for grassland pastoral settlements

Building on the advancements in integrating phase change materials (PCM) within building envelopes to enhance thermal performance, this paper explores the use of slag cement combined with PCM to significantly improve the heat storage performance of radiant floors. The study involved the preparation of a heat storage composite mortar by mixing 0–10 % PCM into slag cement mortar using a specialized process. The thermal performance test shows that the thermal conductivity and thermal diffusivity of radiant floor decreased by 9 % and 10 % respectively with 1 % increase of PCM. Through SEM and DSC analysis, it was determined that incorporating more than 4 % PCM markedly enhances the mortar's thermal storage capacity, with 7 % identified as the optimal maximum addition. The utilization of an experimental platform within an environmental chamber to test a radiant floor module with a 5 % PCM replacement (3.26 wt%) demonstrated a 12.5 % increase in heating efficiency and a 15 min delay in peak heat flow during the exothermic process. Additionally, adding 10 % PCM increased the surface temperature of the radiant floor by 18 %, and a water supply temperature of 45 °C further elevated the surface temperature by 21 %. These findings suggest that the PCM improves the thermal insulation, the heat transfer efficiency and heat storage performance of the radiant floor, facilitates the integration of abundant renewable resources, and further integrates the system with the solar energy, thus providing a way to solve the energy-environmental balance of grassland pastoral dwellings.

Compositional Design of New Environmentally Friendly Geopolymer Mortar Based on Kaolin and Granite Residues.

The use of industrial residues in civil construction is an exciting alternative to mitigate environmental impacts and promote the circular economy. This work developed new compositions of geopolymer mortars activated by NaOH from fine kaolin residue (RCF), coarse kaolin residue (RCG) and granite (RG). All residues were benefited and characterized by chemical analysis (X-ray fluorescence), mineralogical phases (X-ray diffraction) and granulometry (laser granulometry). Additionally, the RCF was calcined at 650 °C for 2 h (RCFC) to produce metakaolin, which is the starting point for the geopolymer reaction. A mixture of experimental designs was accomplished to evaluate the water/binder factor (Wexp (%)) necessary for new geopolymer mortar compositions to reach the consistency index (260 mm, ASTM C1437-15) and the effect of different curing conditions on the simple compressive strength (SCS). The geopolymeric compositions with RCFCs, pre-cured at room temperature, exhibited the highest Wexp% values (>40%) and significant SCS, with curing conditions A and B reaching 6 MPa and 7 MPa, respectively. Such behavior can be explained by the fact that the pre-curing step at room temperature keeps the system humidity relatively high, favoring the dissolution of Si4+ and Al3+ ions and, therefore, increasing the Si/Al ratio, which positively influences the geopolymerization kinetics reaction.

Mortars in the Archaeological Site of Hierapolis of Phrygia (Denizli, Turkey) from Imperial to Byzantine Age

Hierapolis of Phrygia, an archaeological site in southwestern Turkey, has been a UNESCO World Heritage Site since 1988. During archaeological campaigns, 71 mortar samples from public buildings were collected, dating from the Julio-Claudian to the Middle Byzantine period. The samples were analyzed using a multi-analytical approach including polarized optical microscopy (POM), digital image analysis (DIA), X-ray powder diffraction (XRPD) and SEM–EDS to trace the raw materials and understand the evolution of mortar composition and technology over time. During the Roman period, travertine and marble were commonly used in binder production, while marble dominated in the Byzantine period. The aggregates come mainly from sands of the Lycian Nappe and Menderes Massif, with carbonate and silicate rock fragments. Variations in composition, average size and circularity suggest changes in raw material sources in both Roman and Byzantine periods. Cocciopesto mortar was used in water-related structures from the Flavian to the Severan period, but, in the Byzantine period, it also appeared in non-hydraulic contexts. Straw became a common organic additive in Byzantine renders, marking a shift from the exclusively inorganic aggregates of Roman renders. This study illustrates the evolving construction technologies and material sources used throughout the city’s history.

Mechanical Characterization of Sustainable Mortars with Recycled Aggregates from Construction and Demolition Wastes: An Experimental Investigation.

The use of recycled aggregates in the production of concrete and mortar represents a sustainable way to reintroduce these constituents-which are typically treated as waste and disposed of-in the production chain, providing new value to potentially polluting materials. The effect of recycled aggregates has been widely studied in the production of concrete due to the directions of National Standards in Italy; however, their role in the manufacturing of mortar must be investigated further due to the high variability that can be observed in the literature. In particular, the aim of this paper is the mechanical characterization of sustainable mortars defined by different mix designs and different binders, in which the aggregates are gradually replaced by a recycled sand obtained from the grinding of construction and demolition wastes, which could include old concrete, clay bricks, and minimal amounts of other kinds of residual materials. This investigation is carried out through experimentation, taking into account four different mortar compositions defined by an increasing percentage of recycled constituents. Virgin aggregates are also studied for the sake of comparison. The results, accomplished through a three-point bending test and an unconfined compression test, show that it is still possible to maintain acceptable mechanical properties by using these wastes as aggregates in spite of a decrease in the analyzed values. In general, the mean reductions with respect to the use of natural aggregates are about 30-40% and 35-55%, respectively, for compressive and flexural strengths. It should be highlighted that some experimental sets provide a maximum reduction of 70-80%, but the results are still within the limitations of the standards. This aspect can be considered to be a good compromise since the production of this sustainable construction material can represent a solution that is able to reduce the extreme exploitation of natural resources, the pressure on landfills, and the consumption of energy, which are related to the construction industry.

Enhancing energy efficiency of buildings located in the Mediterranean area using Phase Change Materials (PCMs) integrated into mortar formulations.

Abstract Phase Change Materials (PCMs) in building materials can significantly reduce energy consumption in heating and cooling systems. PCMs absorb, store, and release thermal energy by transitioning between solid and liquid states based on external temperatures, helping to regulate indoor temperatures and lower energy use. This study evaluates the thermal performance of various mortar compositions containing PCMs made from hydraulic lime and cement. The PCMs were developed using the “form-stable” method, incorporating a porous matrix of Lecce Stone (LS), known for its high porosity, and sourced from processing waste, supporting sustainability principles. The selected PCMs were Polyethylene Glycol (PEG) with molecular weights of 800 and 1000 g/mol, suitable for Mediterranean climate temperatures. The temperatures that characterize this geographic area were simulated in a climatic chamber to assess the thermal behavior of the mortars containing the PCMs across all four seasons. The results showed that mortars with composite form-stable PCMs effectively mitigated indoor temperature fluctuations, reducing the need for heating and cooling. Additionally, energy savings calculations demonstrated significant reductions in heating and cooling costs, underscoring the potential of the PCMs to enhance building energy efficiency.

Effect of organic corrosion inhibitors on the behaviour of repair mortars and reinforcement corrosion

Repairing concrete structures affected by reinforcement corrosion is vital to ensure their durability and safety. Organic corrosion inhibitors (OCIs) are widely used in the construction industry to prevent steel corrosion due to their effectiveness, sustainability, and health and safety benefits. However, the effects of these OCIs on different types of repair mortars have not been extensively studied. This study evaluated the fresh and hardened properties, as well as the corrosion resistance, of four types of repair mortars (polymer-modified, general cementitious, fine-grained, and alkali-activated) incorporated with two types of OCIs (amino alcohols and sodium gluconate-based) at dosages of 0.5 %, 1 %, and 2 %. Additionally, the corrosion kinetics of mortars under the influence of OCIs were analysed using the impressed current technique. The results indicated that OCIs generally enhanced workability and increased void content across all repair mortars. The amino alcohol inhibitor increased the drying shrinkage of general cementitious and fine-grained mortars by up to 33 % and 39 %, respectively, and reduced compressive strengths by 47 % and 26 %. However, it did not significantly affect water absorption. In contrast, the sodium gluconate inhibitor increased water absorption in all repair mortars but notably decreased drying shrinkage by up to 47 % in polymer-modified mortar and 66 % in alkali-activated mortar. Despite the variations in the properties of repair mortars, OCIs effectively resisted corrosion and delayed crack formation time by up to 400 %. The resistance to corrosion improved with increasing amounts of the inhibitor. The results of this study were used to develop a technical guide for the construction industry, facilitating the selection of appropriate mortar compositions to effectively repair corroded concrete structures and reduce the risk of further corrosion.

Evaluating fresh and hardened properties of mortar composite with different types of modified polyethylene terephthalate (PET) materials as additives: Modification effects, surface properties, shape factors

Plastic disposal has become a challenge due to its challenging degradability, and plastics recycling is one of the ideal methods. The utilization of recycled plastic in building materials has been widely researched as a possible way to store plastics permanently. An investigation on the modification and incorporation of polyethylene terephthalates (PET) on fresh and hardened properties of mortar composites (MCs) is performed in the study. The work provides understanding of the synergistic effects of plastic modification methods with different types of PET additives on MC properties and to explain behavior of modified PET in mortar composites. Modification methods include microwave radiation, chemicals oxidation and alkaline hydrolysis. These methods are applied on three types of structural PET materials (hard particles, hard strips and soft yarns). The properties of 0.5%–3% PET added MCs include workability, compressive strength (CS), flexural strength (FS) and toughness are determined. At 28 days, 3% hydrolysis-treated PET yarns significantly increased FS by 69.6% and improved toughness by almost 15 times while CS with 3% PET particles modified by microwave radiation and chemicals oxidation were comparable to the control.

Study on the chloride ion binding rate of sulfoaluminate cement mortars containing different mineral admixtures

In this study, the chloride ion (Cl−) binding rate of sulfoaluminate cement (SAC) mortars containing different mineral admixtures was investigated. This is essential to improve the durability of concrete structures in high Cl− environments, especially where they are susceptible to Cl− attack such as coastlines and marine structures. The effects of Cl− concentration, curing age, and the type and amount of mineral admixture on the Cl− binding rate of SAC mortars were analyzed. It was found that the content of water-soluble Cl− in SAC mortars decreased with the increase of curing age, while the Cl− binding ratio increased accordingly, indicating that its resistance to internal Cl− permeation increased. The addition of fly ash (FA) and ground granulated blast furnace slag (GGBS) can significantly improve the Cl− binding rate of SAC mortars, and the Cl− binding rate increases to 46.6% with 20% of FA and 38.7% with 40% of GGBS. The effects of mineral admixtures on the microstructure and phase composition of SAC mortars were further investigated by X-ray diffraction (XRD) analysis. The results showed that the addition of FA and GGBS promoted the formation of C-S-H (calcium silicate hydrate) gels and improved the resistance of SAC mortars to Cl− penetration. On the other hand, the excessive addition of silica fume (SF) decreased the Cl− binding rate, whereas a moderate amount of limestone powder (LP) improved the Cl− binding rate. The study of the Cl− binding rate of SAC mortars can help to evaluate their resistance to Cl− erosion in real projects, thus guiding the optimization of concrete formulations and the improvement of durability.

Effect of the combination of polyvinyl chloride (PVC) and steel slag waste on the durability and mechanical properties of composite mortars

Effect of the combination of polyvinyl chloride (PVC) and steel slag waste on the durability and mechanical properties of composite mortars

PH–Assisted Strength Gain Projection for Green Cement Mortar Composite Containing Marble Powder By-Product: Substitution and Intergrinding Methods

This manuscript reports the effects of substitution and interground of MP on the pH of cement and bending and compressive strengths of mortar composite as well as strength projection of green mortar composite from pH of green cement. It also presents the relationships between pH of cement and strength of mortar composite to compute strength gain from pH of cement. The feature of sample made with MP–cement is examined and compared to those made with pure Portland cement– including bending and compressive strengths at 7d, 28d, and 90d, and pHs of cement. Projection of strength gain from pHs of cement is also discussed, and the numeric equations, the coefficients, and the r squares, which are essential elements of the strength projection, are given in the experimental study proficiently. Regularly, this study results indicate that the projection for strength gains of green mortar composite could be computed from pHs of green cement properly.

Discovery and Reconstruction of the Remains of the Beacon-Equipped Hollow Enemy Towers along the Ming Great Wall

Hollow Enemy Towers, as iconic structures of the Ming Great Wall, are renowned for their roles in defense surveillance, weapon storage, and firearm operation. Recent studies have indicated that certain Hollow Enemy Towers along the Ji Town section of the Ming Great Wall also serve the function of Beacon Towers for beacon signaling. However, previous studies have not definitively determined if these towers were distinctively marked, nor have they provided a comprehensive account of their current distribution and original historical appearance. This paper initially examined the historical documentation of white lime markings employed on the outer walls of certain Hollow Enemy Towers, which served as Beacon Towers during the middle and late Ming periods. Utilizing multidisciplinary methodologies, this research identified remains of lime markings of the Beacon-Equipped Hollow Enemy Towers along the Ji Town section of the Ming Great Wall, illustrating their extensive distribution. We analyzed the material composition and construction techniques of the lime mortar. This analysis clarifies the scope of lime plastering on the exterior walls of these towers and offers a point of reference for restoring their original historical appearance. The results make a significant supplement to the types of signaling structures on the Great Wall, enriching existing understanding of the original appearance of the Great Wall’s historical landscape.

Electromagnetic absorption properties of composite mortar with graphene and manganese-zinc ferrite

Electromagnetic wave absorption of building structures plays a crucial role in safeguarding information and mitigating electromagnetic radiation. This study delves into the absorption capabilities of composite mortar made with graphene (GR) and manganese-zinc ferrite (MFO) across frequencies of 1–18 GHz. The mechanical strength, microstructural examinations, and numerical simulations to elucidate the underlying mechanisms of wave absorption in the composite mortar are investigated. The results indicate that incorporating 30 % MFO reduces the strength of mortar due to its low bonding capacity and diluting effects, whereas GR enhances the strength of mortar by facilitating cement hydration. Electromagnetic examinations reveal that MFO boosts the magnetic loss performance, while GR augments dielectric loss properties. In addition, the presence of needle, rod, mesh, and flake hydration products in the pores of composite mortar also contributes to increased wave depletion. According to the simulation of electromagnetic absorption based on the finite difference time domain (FDTD) method, the composite mortar with GR and MFO exhibits a superior performance of electromagnetic wave absorption. With the 25 mm thickness of composite mortar with 30 % MFO, an absorption below −10 dB, covering a bandwidth of 1.68–4.34 GHz are obtained, with a peak reflection loss of −22.13 dB at 3.23 GHz. Thus, by combination magnetic loss of MFO, dielectric loss of GR, and the reflective capabilities of porous mortar, a composite mortar with a better electromagnetic wave absorption can be achieved.

Feasebility of using waste hydrated cement paste and luminescent glass as aggregates for the production of mortar

This study examines feasibility of incorporating waste hydrated cement paste (WHCP) and luminescent glass (LG) as sand replacements in conventional mortars. Luminescent glass aggregates (LG) were produced by initially mixing luminescent powder with adhesive resin and subsequently adding glass pellets with size smaller than 2 cm. WHCP was produced by mixing cement and water and then cured at room temperature prior to be ground into aggregate with size smaller than 2 mm. Luminescent composite mortars (WLM) were produced by replacing 50–70% of sand by WHCP and LG in which LG replaced 40% of the sand content while WHCP replaced the remaining 10–30%. The feasibility of WLM samples were assessed by their physical and luminescent properties. As results, WLM samples met requirements for constructive mortar such as flowability, drying skrinkage and porosity. At 28d, all WLM samples achieved a strength of around 45 MPa at 28 days, satisfying the strength requirements for constructive mortar. Regarding luminescence properties, all WLM samples exhibited luminescent intensity higher than the threshold of human eyes up to 8h. Luminescent decay curves followed the trend observed in luminescent powders. As such, WLM can be utilized in building projects, particularly for the auxiliary tasks related to road and bridge structures.