Mortar System Research Articles

Applying Alkali Activator and Hydrophobic Agents in Clay-Based Mortars for Enhanced Properties

Clay-based mortars are susceptible to water intake and exhibit low mechanical strength, presenting challenges in their application within the construction sector. This research addresses these vulnerabilities by investigating the combination of alkali activators with waterproofing agents, specifically a nano-clay and an acrylic emulsion, to enhance the properties of clay mortars. Alkali-activated materials are known for their superior mechanical properties and sustainable potential, especially when derived from low-cost by-products. Recent studies have focused on alkali activation using clays and soils as precursors to improve their physical and mechanical properties while increasing durability. However, the high absorbency of these mortars remains a concern, as it can lead to matrix degradation. Therefore, to address these problems, this research studied the combination of a highly alkaline activator (potassium metasilicate) with hydrophobic agents, such as a nano-clay and an acrylic emulsion, using two different clayey soils. The results indicated that potassium metasilicate (PO) enhanced the mechanical properties and stability for both aluminosilicate systems, while nano-clay (PONC) significantly reduced the capillary absorption through time, especially in A2 systems. The addition of acrylic emulsion (POD) proved highly effective in both systems, significantly improving durability. By integrating these agents, the mortar systems were protected against water intake, while durable construction materials were formed.

Sustainable quaternary binders made from metallurgical wastes of northeast Mexico: strength, hydration products, and durability.

In this research, four industrial wastes were used for up to 80% as supplementary cementitious materials (SCMs) in cement mortar systems: ground granulated blast furnace slag, electric arc furnace slag, basic oxygen furnace slag, and waste limestone powder. Quaternary cementitious blends were prepared and studied for up to 120days. Workability, compressive strength, durability, microstructures, and sustainability studies were performed and compared with Portland cement references. Results showed that more than 30MPa in compressive strength can be achieved by > 50% replacement with SCMs; only 9% below the reference. Neither H2SO4 nor MgSO4 attacks resulted in critical damages; nevertheless, curing under NaCl solution showed detrimental behavior. C-S-H with a low Ca/Si ratio was identified in the mortars as the main hydration product, possibly intermixed with stratlingite, C-A-S-H and/or hydrotalcite. Environmental impact for the blended cements was determined as the CO2eq. factor from a simple life cycle assessment. The embodied greenhouse gasses varied in 260.2-541.4kg CO2eq./ton of binder depending on the formulation. This was 40-70% less than Portland cement (922.6kg CO2eq./ton). The production of the raw materials dominated the polluting emissions, while freight, grinding, and sieving had little environmental impact.

Constitutive relationship of soil in contact with mortar under continuous loading

Mortars will remain critical in future land wars due to their flexibility and versatility. When mortars are fired continuously, the contact soil is gradually compacted by the mortar base plate, and dynamic research into this process is the basis for innovative mortar design. However, the discontinuity and nonlinearity of soil contact absolutely necessitate the constitutive relationship of soil contact, which is difficult to study. Therefore, this study conducted experimental research and theoretical derivation to establish an accurate dynamic model of the mortar system. First, based on the nonlinear elastic–plastic theory and the stress–strain relationship of soil under cyclic loading, a theoretical analysis method for the constitutive relationship of contact soil under continuous loading was proposed. Second, an experimental and testing system was designed to simulate launch loads, and the stress–strain response of soil under continuous impact loads was obtained experimentally. Subsequently, based on theoretical analysis and experimental data, the stress–strain relationship during the gradual compaction of soil was established using the least squares method. Finally, a constitutive relationship model of the contact soil in the mortar system was established in ABAQUS using the VUMAT subroutine interface, and the calculated results were compared and analyzed with traditional calculation results. The results indicated that studying the constitutive relationship of mortar in contact with soil during continuous firing using this method can improve the accuracy of dynamically modeling mortar systems. Moreover, this study has practical value in the engineering design of mortar systems.

Effect of curing conditions on cement based self-compacting mortar produced with mortar waste aggregate

Concrete and mortar wastes, which have a large volume and economic value among construction demolition wastes, are the most targeted demolition waste group to be recycled. An important area where construction demolition waste can be utilized is self-compacting mortar (SCM) systems. SCMs are innovative and economical systems designed to minimize the labor requirements that are difficult to meet in the production process. In this study, mortar waste aggregate (MWA) obtained by mechanical crushing and grinding was used in SCM elements by substituting different ratios (5-10-20-30-40 %) by mass to aggregate. In this way, it was aimed to evaluate both the sustainability of MWAs and the usability of MWAs in SCMs, which are considered as a new production technology. The fresh and hardened mortar tests performed in the study are presented comparatively. The physical (dry unit volume weight, porosity), durability (capillary water absorption) and mechanical properties (flexural tensile, compressive strength) of the hardened SCM elements are based on the determinations made at 3, 7 and 28 test days and according to different curing conditions (water curing, air curing and heat curing).In addition, X-ray Diffractometer (XRD) analysis was performed on specimens obtained from 0 %, 10 %, 20 % and 40 % MWA substituted specimens after heat curing (after 7 days water curing) and 28 days water curing. In the light of the data obtained, it is reported that SCM production with 10 % MWA substitution is feasible in terms of sustainability and engineering properties evaluated in this study.

A multi-performance comparison between lime, cementitious and alkali-activated TRM systems: Mechanical, environmental and energy perspectives

The combined need to propose new solutions for the structural reinforcement of existing buildings and for the reduction of CO2 emissions is leading to the development of more sustainable composite materials, such as those based on alkali-activated mortars (AAM). In this study, different formulations of AAM, based on metakaolin or fly ash, have been evaluated as possible matrices for Textile Reinforced Mortar (TRM) systems. Two different bidirectional textiles, made of AR glass or basalt fibers, were used as internal reinforcement. The physical-mechanical properties of TRM systems based on AAM were evaluated and compared with those of commercial systems with cementitious or lime-based matrices. Direct tensile tests on TRM coupons and shear bond tests on clay brick substrates were carried out. Then, their energy and environmental-related performance have been compared. Results showed that alkali-activated matrices can be very promising and eco-friendly alternative solutions to traditional mortars in TRM systems.

Enhancing Load-Carrying Capacity of Reinforced Concrete Columns with High Aspect Ratio Using Textile-Reinforced Mortar Systems

Enhancing Load-Carrying Capacity of Reinforced Concrete Columns with High Aspect Ratio Using Textile-Reinforced Mortar Systems

Physically simulating the dispersion of chopped carbon fibres in mortar

Carbon fibre dispersion exerts a critical influence on the characteristics of carbon fibre-reinforced cement mortars (CFRCMs). This study accordingly investigated the dispersion of chopped carbon fibres (CCFs) in mortar using physical experiments with a transparent simulated mortar system comprising colloidal silica and silica sand as replacements for cement and aggregate, respectively, and evaluated the microstructures and conductive performances of corresponding CFRCM specimens. In the simulated solutions, bundled CCFs in order were more prone to disperse into single fibres than clustered ones in disorder due to no physical fixation, colloidal silica prevented the formation of CCF clusters during stirring, and the shear force of moving sand dispersed but also broke CCFs. In the CFRCMs, sand aggregates reaggregated dispersed CCFs while larger sand particles increased CCF dispersion and improved specimen conductivity. Thus, decreasing the amount of CCFs clusters before dispersion, and a short stirring time in a single direction should be provided to prepare CFRCMs with well-dispersed CCFs. Meanwhile, a more dispersible aggregate and less formation of void should be also essential.

Characterizing boron-enhanced one-part alkaline-activated mortars: Mechanical properties, microstructure and environmental impacts

Since alkali activators negatively effect the environmental impact assessment, it is necessary to develop the alternative activators from natural sources with low environmental impact. Therefore, in this study, the usage of boron refined products colemanite, ulexite and boron pentahydrate as activators in slag-based alkali-activated mortar systems was investigated in detail. Flexural and compressive strength tests, isothermal calorimetry measurement, thermogravimetric and differential thermal analysis, inductively coupled plasma mass spectrometry analysis, field emission scanning electron microscopy, and energy dispersive analysis and elemental mapping and X-ray diffraction analysis were carried out on the samples. In addition, sample production was subjected to life cycle analysis (LCA) with a cradle-to-gate approach using two different transportation scenarios. According to the results obtained, it was determined that colemanite, ulexite and boron penta hydrate, when used in optimum proportions, had a positive effect on strength (up to increase 40% compressive strength by 20% ulexite replacement) and could be used as an activator in slag-based alkali-activated systems. The positive results obtained in strength as a result of using boron-refined products are also supported by other test results conducted within the scope of the study. Furthermore, according to the LCA results, it was observed that there was a significant decrease in global warming potential with the substitution of 20% colemanite, ulexite or boron pentahydrate as activators, not only compared to the reference sample but also traditional cementitious systems.

Tensile behavior of Textile Reinforced Mortars made with Flax fabrics

Nowadays, several industrial sectors are more and more motivated to develop and adopt sustainable solutions. In this context, the construction industry is not an exception: new materials, possibly obtained from renewable and locally available sources, are being worldwide developed and explored. As part of this common effort, special attention is being paid to an emerging class of materials generally referred to as bio-based composite systems. This study investigates the mechanical properties of a Textile-Reinforced Mortar (TRM) system produced with flax textiles embedded within a hydraulic lime-based mortar. The research also aims at analyzing the cracking patterns exhibited by the Natural TRM systems under investigation. The proposed analyses highlight the relevant mechanical response observed in the experimental results and allows to have a comprehensive overview of the feasibility of using natural textiles for strengthening existing structures.

Performance Evaluation of Hybrid Fiber‐Reinforced Inorganic Mortar for Textile‐Reinforced Mortar Applications

The need to improve existing structures has led to extensive research on strengthening techniques. Textile‐reinforced mortar (TRM) systems, which involve the integration of high‐strength fibers with inorganic matrix, have emerged as a highly promising and viable alternative. The objective of this research is to investigate the mechanical characteristics of inorganic mortar by examining different compositions involving sand, fibers, and cementitious materials. Various combinations were tested to evaluate their compressive strength, split tensile strength, and flexural strength. The findings indicated that a composite mixture (sample 12) comprising microsilica, silica sand, and optimized fibers demonstrated enhanced strength in all three assessments. Research highlights the significance of accurate mixing, additional components, and appropriate fibers to achieve intended performance of the mortar. The compatibility of the mortar is checked with substrate surface and textile sheet. Mortar is evaluated for splitting bond strength, slant shear test, direct pull‐off bond strength, and pull‐out strength. These results provide information about the strength and bonding characteristics of the mortar in different test scenarios. Values indicate how well the mortar performs with the substrate surface and the textile sheet under various types of stresses and loading conditions.

Natural Fiber Textile Reinforced Mortar (NFTRM) for Integrated Masonry Upgrading

The construction and building industry is responsible for a significant amount of carbon emissions due to its high energy consumption throughout the lifecycle of buildings. Many masonry buildings were constructed without following any seismic or energy standards, making them vulnerable to both natural and man-made disasters.This paper discusses the use of a Natural Fiber (NF) in the Textile Reinforced Mortar (TRM) system, to upgrade or retrofit masonry walls, addressing both structural and thermal issues.During this campaign, various jute fiber products have been used to upgrade or retrofit the masonry wall to achieve a balanced thermo-structural property for the NFTRM system. Notably, jute fiber nets (with mesh type “2.5 cm x 2.5 cm”) and diatons have been used to enhance the strength of the masonry wall. For the thermal upgrading of masonry walls, a combination of 30 mm jute fiber length and 1% jute fiber (based on the dry mortar mass) was chosen for composite mortar preparation.The use of the jute NFTRM system has resulted in an increased load-bearing capacity (kN) of more than 450% and whereas, an improved insulation capacity, with a reduction of thermal transmittance (W/m2K) of about 36% have been observed for the upgraded masonry wall, when compared to the un-strengthened masonry wall.

Influence of spike anchors in the bond behaviour of FRCM systems applied on concave masonry substrates

One of the methods that can be used for strengthening masonry arch structures is through the use of composite systems bonded to the external surfaces, preferably to the intrados, such as textile reinforced mortar systems (FRCM, TRM, SRG etc). The application of such systems to the intrados allows the ultimate load to be increased while keeping the structure in service. The load increment depends on the performance of the bond between the matrix and the masonry substrate and between the matrix and the fabric, and also the radial detachment stresses (normal for the strengthening system) that are generated when applying this technology to concave surfaces must also be taken into account, as they have a negative effect on the load transfer mechanism. Spike anchors are generally used to reduce the negative effect of curvature in order to postpone the debonding process of the strengthening system. This paper presents the results obtained from a direct shear test campaign on curved masonry specimens strengthened with a fiber-reinforced cement-based matrix (FRCM) with pozzolanic reaction and a carbon fiber fabric. In particular, the effects of spike anchors on the load transfer mechanism between FRCM and the masonry substrate are shown. The use of such spike anchors produced, on average, a higher maximum ultimate force than specimens without spike anchors.

Mechanical properties and microstructure of cement-fly ash-dacite powder composite cementitious system

This study used the indexes of fineness, pozzolanic activity, hydration heat, mortar fluidity and strength, and circular cracking degree, and combined the techniques of SEM, EDS, XRD, MIP, and TG-DSC. We investigated the effect of different finenesses and contents of dacite powder on the mechanical properties and microstructure of the composite cementitious system. The results showed that the median diameter of 12 μm of dacite powder has better basic properties, and can be used together with cement and fly ash as cementitious materials in mortar systems. The addition of dacite powder can effectively improve the crack resistance of the composite cementitious system. The microscopic test found that dacite powder has the "filling role" and "nucleation role" in the system, which is reflected in the optimization of the pore structure, improves the interfacial adhesion, reduces the evaporation of free and adsorbed water, and reduces the rate of quality loss.

Autogenous self-healing induced by compressive fatigue in carbonated hydraulic lime mortars

This study investigates the autogenous self-healing mechanisms in carbonated natural hydraulic lime mortar exposed to cyclic compressive loads. We sought to explain the observed 40% surge in residual compressive strength compared to the quasi-static compressive strength following fatigue testing at frequencies of 5 Hz, 0.5 Hz, and 0.05 Hz [Theoretical and Applied Fracture Mechanics 118 (2022) 103201]. Central to our investigation is the hypothesis that cyclic loads mobilize the embedded water in the mortar, catalyzing chemical reactions that foster autogenous self-healing. To substantiate this, intact and post-compressive fatigue specimens were analyzed using differential thermal analysis (DTA), thermogravimetric assessments (TGA), mercury intrusion porosimetry (MIP), and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). The TGA-DTA highlighted the evolution of new hydration pathways, characterized by C–S–H gel and portlandite formation. The MIP results indicated a decline in pore volume, particularly in fine pores, affirming the synthesis of novel hydration compounds. The SEM-EDX analysis further authenticated the composition of these emergent microstructures. This work, therefore, presents a comprehensive understanding of the factors influencing autogenous self-healing in lime mortar systems.

Study of dynamic characteristics of a new suggested recoiling mortar system

The purpose of this paper is to study the characteristics of recoil motion of a new suggested recoil system designed for the Russian 120- mm PM-38 mortar, rather than the conventional fixed-barrel mortar system. The new recoil system enables to reduce the total force imparted by the mortar system to the carriage, with the purpose of the mortar can be mounted on tracked/wheeled vehicles. The paper presents the suggestion of the new recoiling mortar system along with the discussion of the presentation of constructional considerations and constraints. The dynamic characteristics of recoil motion have been modelled with the aid of a new mathematical model that have been established using MATLAB software. As a result of the suggestion of the new recoiling mortar system, the maximum recoil resistance force is predicted to be reduced by more than 60% compared to that in the traditional fixed-barrel mortar system. In addition, the maximum recoil distance was predicted to be around 26 cm.

Full-scale cyclic tests on a stone masonry building to investigate the effectiveness of a one-side application of the composite reinforced mortar system

The results of an experimental study on a full-scale, two-storey rubble stone masonry building, strengthened with a Composite Reinforced Mortar (CRM) system applied on the external face of the walls, are herein presented. The CRM system consisted of a mortar coating reinforced with Glass Fiber Reinforced Polymer (GFRP) mesh and injected steel transverse connectors, which connect the separated wythes of the masonry. The aim of the research is to investigate the effectiveness of this strengthening technique. The study concerns two cyclic experimental tests: the first was carried out on the unreinforced masonry building up to a damage level not far from the ultimate limit state. Then, the building was repaired, strengthened with the proposed technique, and tested again. The second test was carried out up to a near-collapse condition. This allowed to evaluate the effectiveness in terms of seismic performances provided by the reinforcement.The cyclic horizontal load, with increasing amplitude, was applied to each of the two longitudinal walls of the building by means of servo-controlled hydraulic jacks pinned to a vertical steel beam. This beam allowed the distribution of the total lateral force between the first floor and roof level, in the fundamental mode shape. The experiments proved the effectiveness of the proposed strengthening method: with respect to the unreinforced masonry building, the resistance increased by 2.4 times, the displacement capacity by 4 times and the total dissipated energy by about 7.2 times. These benefits were due to the GFRP mesh reinforced coating’s capability to prevent the formation of isolated thick cracks, instead promoting a wider dispersion of many closely spaced thin cracks. Moreover, the importance of transverse connectors in preventing the separation of the masonry leaves in the strengthened walls was also clearly observed.

20th Century Mortars: Physical and Mechanical Properties from Awarded Buildings in Lisbon (Portugal)—Studies towards Their Conservation and Repair

This paper addresses the study of renders and plasters’ physical and mechanical characteristics from selected buildings awarded during the 20th century with a renowned architectural prize in Lisbon, Portugal. The characterisation was done to understand mortars’ physical and mechanical properties and their evolution during the 20th century. These characteristics will also help determine compatibility requirements for future conservation and restoration interventions. Since these buildings have a heritage great interest status, the need to preserve them is a paramount issue. Fifty-three samples from nine case studies were studied via capillary water absorption, drying rates, open porosity, dynamic modulus of elasticity, and compressive strength. There were limitations in sample collection due to the buildings being in service and technical constraints regarding sample quantity for testing and separating layers of the multi-layer mortar system. Nevertheless, the results showed different ranges of quantitative values for these tests, whether the mortars were lime, gypsum, cement-based or had lime–cement blended formulations.

Durability, workability, and setting time of cementitious systems containing chloride-rich oil and gas production wastewater

The application of alternative non-potable water sources can be leveraged to build infrastructure components that support sustainable industrial operations in regions that experience high frequency of freshwater shortages. This study examines how the use of highly saline produced water (as mixing water) in portland cement mortar impacts workability, setting time, electrical resistivity, pore formation, and microstructure. The results show that produced water decreases both mortars setting time by 30% and workability by 20%. Alkali solubility and pore solution conductivity are also influenced by the produced water-increasing pore solution conductivity by approximately 100 mS/cm. The produced water reacts with the cementitious material to form small deposits of Friedel's salts and calcite that primarily fill the smaller pores in the matrix-thus primarily influencing the pore structure of low w/c mortar systems. In the low water/cement (w/c) produced water mortar systems (0.4), both the pore formation factor (∼2X) and resistivity (∼1.5X) are significantly higher than the control (tap water mortar systems), but in the high w/c systems (0.6) both are slightly lower. The produced water mortar systems also tend to retain more moisture during dry cycling which leads to significantly lower resistivity than the control in air-dried conditions. Diluting the produced water with tap water will reduce moisture retention during dry cycling and increase resistivity.

Numerical Modeling of Single-Lap Shear Bond Tests for Composite-Reinforced Mortar Systems

The large demand of reinforcement systems for the rehabilitation of existing concrete and masonry structures, has recently increased the development of innovative methods and advanced systems where the structural mass and weight are reduced, possibly avoiding steel reinforcements, while using non-invasive and reversible reinforcements made of pre-impregnated fiber nets and mortars in the absence of cement, commonly known as composite-reinforced mortars (CRMs). To date, for such composite materials, few experimental studies have been performed. Their characterization typically follows the guidelines published by the Supreme Council of Public Works. In such a context, the present work aims at studying numerically the fracturing behavior of CRM single-lap shear tests by implementing a cohesive zone model and concrete damage plasticity, in a finite element setting. These specimens are characterized by the presence of a mortar whose mechanical behavior has been defined by means of an analytical approximation based on exponential or polynomial functions. Different fracturing modes are studied numerically within the CRM specimen, involving the matrix and reinforcement phases, as well as the substrate-to-CRM interface. Based on a systematic investigation, the proposed numerical modeling is verified to be a useful tool to predict the response of the entire reinforcement system, in lieu of more costly experimental tests, whose results could be useful for design purposes and could serve as reference numerical solutions for further analytical/experimental investigations on the topic.

Effects of mono and binary recycled aggregates on the rheological properties of geopolymer mortars synthesized with construction and demolition waste-based binders

This study comprehensively investigated the effect of different types of fine construction and demolition waste (CDW)-based aggregates, including recycled concrete aggregate (RCA), recycled ceramic tile aggregate (RTA) and recycled brick aggregate (RBA) on the fresh rheological properties of geopolymer mortars (GPMs) derived from CDW-based aluminosilicate binders. The results were compared to those of silica sand (SSA) and natural sand (NSA) with equivalent particle size distribution. In addition, the binary inclusion of RCA, RTA and RBA with 50% SSA or NSA fine aggregates was also considered in an attempt to reach rheological behavior closer to that of SSA and NSA-based GPMs. All mortars were blended with a CDW-binder composed of a ternary mixture of brick (RBP), ceramic (RTP) and concrete waste (RCP) powders optimized at pre-targeted chemical parameters of SiO2/Al2O3 and Na2O/SiO2 of 5.7 and 0.18, respectively. The geometrical shape parameters and packing densities of RCA, RTA, RBA, SSA and NSA aggregate skeletons and geopolymer mortar systems were also evaluated to examine their relationship with the rheological parameters of static and dynamic yield stresses, apparent and plastic viscosities, shear stresses and strains and thixotropy of GPMs. Although the incorporation of CDW-based aggregates resulted in enhanced rheological parameters, they exhibited shear-thinning or pseudoplastic behavior similar to SSA and NSA-GPMs. Yet the addition of RCA with a lower consumption of suspending fluids and reduced non-colloidal interactions than RBA and RTA resulted in overall rheological properties closer to those of SSA and NSA-GPMs, which further improved when combined with SSA or NSA in binary-aggregate-based GPM systems.