Behavior Of Mortar Research Articles

Electro-mechanical behaviour of mortars reinforced with alternative electrically conductive inclusions

Abstract The incorporation of electrically conductive inclusions in structural materials can impart self-sensing functionalities, making them ideal for structural health monitoring applications. However, the use of more sustainable alternatives and their effect on key engineering properties remain largely unexplored, while the adoption of different testing protocols for the characterisation of electrical/self-sensing properties can lead to different results, thus questioning their reliability, even for existing smart composites. This paper investigates systematically the effect of recycled carbon fibres and graphite powder on the mechanical, electrical, transport properties and piezoresistive performance of cementitious mortars. Virgin carbon fibres, at dosages equivalent to those of recycled fibres, were also examined to establish a performance benchmark. Fibre content ranged from 0.05% to 1% vol., while graphite powder was added as sand replacement at contents varying from 0.3% to 3% vol. The effect of existing testing protocols and electrode layout on the piezoresistive performance was also examined, and the associated limitations and challenges are discussed in detail. The results demonstrate the potential of recycled carbon fibres as a cost-effective alternative in smart applications, without compromising electrical and piezoresistive performance. The use of 0.25%vol. of recycled or virgin carbon fibres was found to provide the desirable synergy between structural performance, cost and self-sensing properties, yielding a 50–60% increase in flexural strength, and good piezoresistivity with a gauge factor of 90–110. In contrast, the use of graphite powder resulted in composites with poor self-sensing ability even at the highest content examined (3%vol.), also accompanied by a reduction in compressive strength up to 33%.

Constitutive Relation of Polypropylene-Fiber-Reinforced Mortar Under Uniaxial Compression at High Temperature

Exposure to elevated temperatures leads to the deterioration of the mechanical properties of cementitious materials. However, the inclusion of fibers can mitigate, to some extent, the negative effects of high temperatures on these materials. Specifically, polypropylene (PP) fibers, a synthetic fiber type, have been demonstrated to improve the performance of cement-based composites. Therefore, it is essential to investigate the impact of temperature on the behavior of fiber-reinforced mortar for its broader application in construction. This study explores the effects of varying PP fiber contents (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1%) and different temperature exposures (25 °C, 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C) on the performance of cement mortar. The experimental results show that elevated temperatures significantly degrade both the mechanical and thermal properties of fiber-reinforced mortar. As the temperature and fiber content increase, both the quality and thermal conductivity of the mortar decrease. Between 25 °C and 200 °C, the incorporation of PP fibers (ranging from 0% to 0.2%) significantly enhances the compressive and flexural strengths of the mortar. However, this improvement becomes less pronounced as the fiber content exceeds 0.2%. At temperatures above 200 °C, further increases in temperature, coupled with higher fiber contents, consistently lead to a reduction in the compressive and flexural strengths. Based on the principles of continuous damage mechanics (which describes the degradation and fracture of materials under loading) and the dual-parameter Weibull distribution theory, a constitutive model is proposed to describe the damage behavior of high-temperature PP-fiber-reinforced mortar under uniaxial compressive stress.

Experimental study on early-age fracture behavior of cement mortar with the addition of fly ash

Experimental study on early-age fracture behavior of cement mortar with the addition of fly ash

Hardened properties and leaching behavior of mortars with activated mining tailings

Hardened properties and leaching behavior of mortars with activated mining tailings

Performance of Cement Mortar Mixtures Containing Fine Aggregate and Admixtures

The purpose of this study is to investigate the influence of the cement/sand (c/s) ratio on the behavior of cement mortar. The used c/s ratios in this study were 1:0, 1:0.45, and 1:0.83. The findings of this study showed that increasing the sand content reduces the compressive strength of the mortar mixture by 41.5 and 28.2% for the c/s ratios of 1:0.45, and 1:0.83, compared to the plain cement mortar (c/s: 1:0). The increase in sand content requires more water content to increase the workability and strength of the mixtures. However, the flexural strength slightly increased compared to the control mortar. In addition, to enhance sustainability, the cement was replaced with two waste industrial materials namely, micro silica (MS) and fume treatment plant (FTP) dust by 20% of cement weight. The modified mixtures (c/s: 1:0) also showed reduced strength at the testing age. The compressive strength of the modified mixtures was reduced by 50% and 19% for the FTP and MS-modified mixtures, respectively. On the other hand, the flexural strength was reduced by 19.1 and 30.2% for the FTP and MS-modified mixtures. This reduction can help achieve certain strength requirements by lowering the cement content in cement concrete mixtures.

Assessment of the fracture properties of mortars reinforced with synthetic fibers

AbstractThis paper investigates the post‐cracking behavior of mortars reinforced with synthetic polypropylene fibers. To three series of mortars, normal strength (NSM), high strength (HSM), and high strength with fly ash (HSMFA), short and long, was introduced at 0.6% and 1% by volume, respectively. Pre‐notched 4 × 4 × 16 cm were used for 3‐point flexural tests, and the digital image correlation (DIC) method was employed to assess the load‐CMOD curves. Based on the experimental curves, a tri‐linear stress‐crack opening (σ‐w) relationship was used to develop an analytical model for the Mode I crack propagation, and the inverse analysis method was applied to optimize the model's parameters. The obtained parameters were compared to the fib MC2010 characteristic values related to serviceability and ultimate limit states. The results show that short fiber‐reinforced mortars exhibit a softening behavior regardless of the fiber dosage after a rapid drop once the tensile strength has been achieved. The three mortars incorporating long fiber reinforcement exhibit a very high deformation capacity and hardening behavior. For NSM, fibers appear to be more effective than HSM and HSMFA. All materials achieve the ultimate fracture opening of 2.5 mm, as defined by the fib MC2010, except 0.6% long fiber‐reinforced HSMFA. Compared to the reference mixture (mixture without fibers), adding synthetic fibers to the mortar did not exhibit a significant environmental and health impact.

Rheological behaviour of cement mortar with recycled organic sand

Rheological behaviour of cement mortar with recycled organic sand

Efeito da autocicatrização no fechamento de fissuras decorrentes do ataque por sulfato em cimento Portland, supersulfatado e álcali ativado

Abstract Self-healing consists of closing cracks and recovering the watertight properties of cement-based materials and can occur by hydration of the materials of the mixture (autogenous) or by materials added to the mixture for this purpose (autonomous). This study consists of the use of stimulated self-healing as a way of mitigating sulfate attack (sodium and magnesium), with the evaluation of the influence of crystalline admixture in this process. For that, cycles of sulfate attack and self-healing (by wetting and drying cycles in water) were performed, aiming to evaluate the behavior of mortars with three types of cement: Portland, supersulfated, and alkali-activated. The results showed that self-healing was not sufficient to close cracks due to sulfate attack. This behavior was associated with the hypothesis that the high calcium content of the crystalline admixture reacted with the sulfates and formed expansive products, increasing the attack rate.

Rheological behavior of nepheline syenite beneficiation waste-based mortars

The valorization of mining waste through its application as a fine aggregate in mortar production offers significant environmental advantages. However, the rheological properties of this composite system must be thoroughly investigated to evaluate the technical viability of such use. To date, no studies have been reported on the consistency and flowability of mortars incorporating nepheline syenite beneficiation waste (NSW) as a fine aggregate substitute. Therefore, the aim of this study was to examine the rheological behavior of mortars where natural fine aggregate (NFA) was partially or fully replaced by NSW. The results indicated that incorporating NSW leads to a marked increase in mortar viscosity. Notably, when substitution rates exceed 50 %, there is a substantial decline in workability, adversely affecting mortar handling. This trend was evidenced by the consistency index test, where the consistency of mortars D75 (225 mm) and D100 (219 mm) decreased significantly compared to the control mortar D0 (280 mm). Additionally, at the reference rotational speed (190.98 rpm), the measured viscosities were as follows: 4.99 Pa s (D0), 5.96 Pa s (D25), 6.96 Pa s (D50), 8.07 Pa s (D75), and 8.78 Pa s (D100), further confirming the reduction in fluidity as NSW content increased. The key properties of NSW believed to influence these results include particle size distribution, surface area, and the shape, geometry, and surface characteristics of the particles. Based on the findings, it can be concluded that NFA can be replaced by up to 50 % with NSW without significantly compromising the rheological properties of the mortar, thus promoting sustainable development through waste utilization.

Experimental study on waterproof performance and freeze-thaw resistance of cement mortar using stearic acid modified mica powder

In this study, stearic acid modified mica powder (SAMMP) was formulated to enhance the water and corrosion resistance of cement mortar. The investigation focused on assessing the freeze-thaw (F-T) resistance of SAMMP modified mortar, including the water absorption, surface morphology, relative dynamic elastic modulus (RDEM), compressive strength, and uniaxial compression. The findings suggested that the water absorption of SAMMP modified mortar decreased by 53.9%–64.4%. In addition, the modified mortar exhibited excellent freezing resistance, with RDEM remaining above 90% after 90 F-T cycles, while the RDEM of the control specimens decreased to 60%. Concurrently, the compressive strength of unmodified specimens experienced a loss rate of 9.74%, which was 3.7 times, 4.29 times, and 1.92 times higher than the modified specimens, respectively. Furthermore, a uniaxial compression constitutive model was established to account for the effects of the F-T cycles and SAMMP contents on uniaxial compression behavior of cement mortar, demonstrating a strong and reliable correlation with the experimental data.

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.

Mechanical Behavior of Masonry Mortars Reinforced with Disposable Face Mask Strips.

This research presents an experimental analysis of the mechanical behavior of masonry mortars incorporating disposable face masks (FMs) cut into two different sizes. The objective is to provide experimental data contributing to the consolidation of recycling FMs in mortar mixtures. To achieve this, two types of mixtures were prepared: one with strips of 3 × 3 mm and another with strips of 3 × 10 mm. These FM strips were added in different proportions by the volume of mortar (0%, 0.2%, 0.5%, 0.8%, 1.0%, and 1.5%). In all mortars, the dry bulk density, volume of permeable voids, and water absorption, as well as compressive, flexural, and tensile strengths, were evaluated after a 28-day water immersion curing period. Additionally, two essential properties in masonry mortars were analyzed: air content and shear bond strength. The results indicated that, for both strip sizes, adding FMs up to 0.2% positively affected the flexural and tensile strengths; concerning control mortar, increases of 6% and 1.4%, were recorded, respectively, for the longer strips. At this percentage, the density, air content, and compressive and shear bond strengths are not significantly affected. The results demonstrated that incorporating FMs into mortar mixtures is a promising avenue for sustainable recycling and helps reduce microplastic environmental contamination.

Thermal analysis of mortar based on crushed dune sand

This study investigates the thermal decomposition behavior of mortars formulated using crushed dune sand and thixotropic polyester resin. Thermal analysis techniques, including Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA), and Gravimetric Thermal Analysis (GTA), were employed to characterize the thermal transitions, decomposition stages, and stability of these mortars. Results indicate that crushed dune sand maintains consistent glass transition (Tg) and crystallization temperatures (Tc) when integrated into the mortar matrix, highlighting its thermal stability. However, the melting point (Tm) varies due to the presence of the resin, which significantly influences the composite’s thermal behavior. Decomposition analysis reveals two major weight loss stages: water evaporation between 200°C to 400°C and organic decomposition of the resin between 700°C to 800°C, with minimal weight change beyond 800°C, indicating thermal stability. The DTA results exhibit distinct endothermic reactions related to dehydration and dehydroxylation, along with a pronounced exothermic peak around 400°C, signifying resin decomposition. Elemental analysis confirms that the crushed dune sand is predominantly silica with minimal impurities, making it suitable for construction applications. This research contributes to a deeper understanding of the thermal behavior of polymer-modified mortars, with implications for enhancing thermal and mechanical properties in construction materials.

Effect of particle size and replacement ratio on mechanical performance of cementitious mortar containing ground recycled acrylonitrile butadiene styrene (GRABS) waste plastics

While waste plastics have been used as a natural sand aggregate replacement in cementitious mortar as a sustainable option to mitigate global accumulation of plastic waste in landfills, fundamental mechanical properties like compressive, tensile, and shear must be known to advance design and practical application of these cement-concrete composites as suitable building construction materials. Experimental testing is conducted to reveal to what extent the cementitious composite properties are altered, thereby influencing their overall mechanical performance, when both ungraded and graded ground recycled acrylonitrile butadiene styrene (GRABS) plastic are employed as substitutes for natural aggregates. The novelty of this research lies in its pioneering investigation to quantify the effects of varying particle sizes and volume fractions of waste plastics acquired through mechanical recycling and their influences on the mechanical properties of mortars containing plastics as a composite material. The results from fresh and hardened material properties are compared to conventional mortar properties to examine the impact of various GRABS particle sizes and volume fractions on the overall material strength. While replacing sand with waste plastic generally reduced mechanical properties, the resulting mixes still met the minimum compressive strength (4060 psi [28 MPa]) as per ASTM C150 standards for Portland cement. Notably, graded plastic particles with sizes less than 0.024 in [0.6 mm] demonstrated an overall improvement in mechanical properties compared to ungraded particles. Failure mechanisms responsible for compressive, tensile, and shear damage development are discussed by analyzing the fracture surfaces, which provide insight into the intricate relationship between waste plastic size and distribution on the mechanical behavior of mortar. The findings indicate that GRABS waste plastics, when combined with sand at appropriate particle sizes and volume fractions, have the potential to create tailored mixes to meet minimum mix design standards for construction applications.

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.

Three-dimensional mesoscopic investigation on the dynamic compressive behavior of coral sand concrete with reinforced granite coarse aggregate (GCA)

In the construction of island and reef engineering, coral concrete shows a good application prospect due to its abundant raw materials. However, the porous and fragile mechanical characteristics of coral reefs limit their use as coarse aggregate in the preparation of coral concrete materials. This study utilized hard and dense granite as the coarse aggregate and regarded coral sand concrete as a two-phase composite material consisting of spherical granite coarse aggregate (GCA) and coral mortar. It investigated the enhancement effect of granite on coral concrete from a microscopic perspective. Five 3D mesoscopic models with different GCA contents and randomly distributed aggregates were established to reveal the variation patterns and failure mechanisms of coral sand concrete under impact loading with GCA. The findings demonstrate that the K&C model can effectively simulate the dynamic compression behavior of coral mortar and granite materials. Under the action of a half-sine incident wave, the dynamic compressive strength of the samples increases with the increase in GCA, demonstrating that the addition of GCA can effectively enhance the impact resistance of coral sand concrete. As the content of GCA increases, the sensitivity of the samples to the loading wave amplitude also increases accordingly.

Influence of polyethylene terephthalate (PET) flakes coating on the microstructure and mechanical properties of alkali activated composites

The objective of this research is the improvement of the mechanical strengths of the alkali activated slag composites with polyethylene terephthalate (PET) flakes content. The main drawback when large PET flakes (2–9 mm) are used in these composites is reduced adhesion between plastic surface and binding matrix. Therefore, the PET flakes were coated with two types of adhesives – based on polyvinyl acetate or sodium silicate solution, and then covered with fly ash, waste glass or slag powders. The microstructure (assessed by scanning electron microscopy) of interfacial transition zone between the PET flakes coated with waste glass and slag powders is denser than for uncoated PET flakes; this explains the improvement of the compressive strength of these mortars especially after longer curing times (28 days). The flexural strengths of the mortars with PET flakes are higher than for reference mortar (with sand aggregate) and the apparent density of the alkali activated composites with PET flakes are in general smaller than for the reference mortar. Thus, the coating of PET flakes improves the mechanical behaviour of mortars, preserving also a low apparent density. These results can lead to a wider recycling of PET waste, slag and waste glass powder, promoting circular economy and reducing the CO2 footprint without compromising the critical mechanical strength of mortars.

Investigating the interfacial vertical shear behavior of BFPMPC mortar and cement concrete with pothole repair

Magnesium phosphate cement (MPC) has both traditional cement properties and ceramic properties with fast setting and hardening characteristics. To rapidly reopen traffic and extend its service life, MPC has been widely used in the rapid repair of highway and airport cement concrete pavement. This study utilizes basalt fiber-reinforced polymer-modified magnesium phosphate cement (BFPMPC) developed in previous research to rapid repair the typical potholes on cement concrete pavement, aims to reveal the interface properties between BFPMPC mortar and cement concrete and further investigate the underlying mechanisms for such properties. Firstly, the optimal mixture ratio was determined by orthogonal test design. Then, the shear strength of the repair interface was measured by composite BFPMPC mortar and cement concrete specimens. The mechanical characteristics of the repair interface and the microscopic mechanism were characterized by nano-indentation technology and SEM/EDS. Finally, the interface constitutive model was established by DIGIMAT and finite element model was developed to simulate the interface failure. Results showed that the no new hydration products were produced by the addition of polymer in BFPMPC. BFPMPC matrix became denser with the increase of age, resulting in the better bonding between fiber and paste. The interface vertical shear strength at 6 h and 3 d were 3.1 MPa and 3.9 MPa, respectively. SEM/EDS results showed that polymer has a certain self-healing ability to decrease the crack width with increase of curing age, and a variety of inclusions in the repair interface were observed. The elastic modulus of each inclusion phase can be effectively analyzed by nanoindentation. The simulation results showed that the pressure on upper surface of BFPMPC mortar transfers to the bottom through the repair interface. As the tensile stress on the bottom over the maximum interface tensile stress, the cracks were extend from the bottom to upper, then the structure was failed. Interface vertical shear strength of numerical simulation was, respectively, 3.149 MPa and 3.957 MPa. It is close to the plain shear strength experimental value, validating the proposed interface constitutive relationship.

Characterization and Classification of Mortars for Underlayment with PCR-PET Artificial Aggregate in Partial Replacement of Natural Sand Aggregate in the Mix

This study investigated the feasibility of using Post-Consumer Recycled Polyethylene Terephthalate (PCR-PET) as an alternative aggregate in mortar for civil construction, aiming to evaluate its properties and impact on the sector's sustainability. Compressive strength, substrate adhesion, workability, and water retention tests were conducted on mortars with PCR-PET addition, and the results were compared with conventional mortars and the requirements of the ABNT NBR 13281 standard. The results showed that adding PCR-PET to mortars led to a slight reduction in compressive strength and substrate adhesion; however, the values remained within the limits set by the standard. Workability and water retention of mortars with PCR-PET were similar to conventional mortars. This study contributes to the field of civil construction by presenting PCR-PET as a viable and sustainable alternative for the use of plastic waste in civil construction, contributing to the reduction of demand for natural resources and waste generation. However, further studies are needed to assess the mechanical behavior and durability of mortars with PCR-PET in the long term, as well as their complete environmental impact.

Influence of enforced carbonation on alkali-silica reaction: Performance and multi-scale mechanisms

Alkali-silica reaction (ASR) has emerged as one of the major concrete deterioration issues. Despite the extensive effort investments in ASR mitigation, the interaction between ASR and carbonation remains unclear. To investigate the role and mechanisms of early-age enforced carbonation in ASR, enforced carbonation conditions at 50 °C and 95 % RH with different CO2 concentrations up to 20 % were employed at two stages. The ASR mitigation efficacy was evaluated by monitoring the volume expansion and cracking behavior of mortars containing reactive aggregates. A comprehensive understanding was obtained by analyzing the evolutions of ASR gel's composition, molecular structure, and hygroscopicity. The results indicate that ASR can be effectively suppressed under carbonation with a 97.9 % decrease in ASR-induced volume expansion and fully suppressed cracking when the mortars were cured at 20 % CO2 for 30 days. The decreases in the Q3 polymerization sites and [K + Na]/Si ratios of the ASR products, as well as the 30.3 % reduction in water uptake capacity of ASR gels under carbonation, uncovered the underlying mechanisms for the mitigated ASR at multiple length scales.