Incorporation of Nanochitin in Cement Mortars: An Approach to Enhancing Durability and Sustainability

Coal-derived char as new sand replacement material in cement mortars: A comprehensive experimental study

This study investigates the effect of Alx and Tix content (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) on the microstructural evolution and mechanical properties of Co-free high-entropy AlxTixCrFe2Ni alloys in both as-cast and homogenized conditions. The research focused on the characterization of structural features, melting behavior, and mechanical performance. Microstructural characterization was carried out using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and differential thermal analysis (DTA). Mechanical properties were evaluated through Vickers hardness testing and uniaxial compression tests. Increasing the Al and Ti content induced a transformation from a single-phase FCC structure to a dual-phase BCC structure, with the primary BCC phase strengthened by spherical precipitates rich in Al, Ti, and Ni. Homogenization annealing at 1100 °C led to an overall improvement in the mechanical properties. The Al0.3Ti0.3CrFe2Ni alloy exhibited the most balanced combination of strength and ductility after annealing, achieving a compressive yield strength of 1510 MPa, a compressive strength of 3316 MPa, and a compressive plastic strain of 45%.

In this study, the effect of thermal exposure on the mechanical, physicochemical, microstructural and self-cleaning properties of photocatalytic cement mortars was investigated. 1%, 2%, 3% and 4% of the ordinary Portland cement weight was replaced with nano-TiO2 particles. Mortars were heated at a rate of 2 °C/min to 200 °C, 400 °C, 500 °C, 600 °C, 700 °C and 800 °C. Compressive and flexural strengths, mass, water porosity, ultrasonic pulse velocity, optical microscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis tests were conducted before and after heating the mortars. The experimental results showed that nano-TiO2 particles have a significant influence on the residual properties of the mortars. The addition of TiO2 increased the resistance of the mortars to thermal deteriorations and preserved the residual mechanical, physicochemical and microstructural properties of the mortars. Additionally, for the first time, the influence of thermal exposure on the photocatalytic performance of cement composites was evaluated in this study by evaluating the degradation of rhodamine B. The photocatalytic performance was unaffected up to 400 °C, however, further heating deteriorated the photocatalytic performance of cement mortars.

This study investigates the use of untreated coconut coir fibers as a sustainable reinforcement in cement mortars, with emphasis on the combined effects of fiber content (0.5–2.0% by volume) and length (10–25 mm) on mechanical performance and water absorption. Sixteen mortar mixes were tested for water absorption, flexural and compressive strength, and microstructural characteristics. Results showed that moderate fiber addition significantly improved both strength and durability. The optimal mix (1.0% fiber, 15 mm length) achieved 8.36 MPa in flexural and 29.28 MPa in compressive strength, representing 61% and 131% improvements over the control, respectively. It also recorded the lowest water absorption (8.38%), attributed to improved fiber–matrix bonding and densification of the interfacial transition zone, as confirmed by Scanning Electron Microscopy. In contrast, excessive fiber dosages led to agglomeration, reduced workability, and diminished performance. A third-degree polynomial regression model was developed to predict mechanical properties based on fiber parameters. The findings demonstrate the feasibility of using untreated coconut waste fibers to enhance mortar performance while contributing to sustainable construction practices aligned with circular economy principles and SDGs. This work provides practical insights into fiber optimization and supports broader adoption of bio-based materials in cementitious systems.

Cement is importance as one of the strategic construction of any civilization depends, and its paramount significance in the construction of building, roads, bridges and infrastructure, which requires the use of cement with special specification and thus the use of polymers as additives to increase the compressive, flexural and tensile strength of the cement used in construction. Cement producing can possibility with high specification and for multiple uses, some studies be carried out on the use of some available additives in small quantities so as to give the cement high desirable specification in terms of color, compressive strength, tensile and permeability compared to ordinary cement. This research aims to know the extent to which some of the physical and mechanical properties of cement mortar, such as compressive strength, flexural and tensile strength, are improved upon weight substitution of specific polymeric materials with high efficiency, such as, silica fume .styrene-butadiene, styrene- acrylic in low weight ratio so that it does not add a high economic cost to the production of therequired concrete .for specific uses and sheds light on the effect of different temperatures on the properties where studied in this study . The study showed that the addition of polymeric materials (Glenium 51, silica fume, styrene –butadiene) with different weight ratio of cement weight at 20°C led to obtaining the highest compressive strength, flexural and tensile strength at the optimum level to the development and improvement of properties. Mechanical and physical cement mortar compared to the reference cement free of additives .As for the use of styrene –acrylic, it had a negative effect and led to a decrease in the compressive and tensile strength .especially in the later ages compared to the reference cement. The optimum ratio of Glenium51 was added to the optimum ratio of each material separately and the mixture was added to the cement mortar at different temperatures( 7, 20, 55 )°C .The effect of additives on the properties of the cement mortar was studied. Also, a mixture (Glenium51, silica fume, styrene-butadiene, styrene-acrylic) was added in the optimum proportions for each material to the cement mortar at different temperatures, and this addition led to increase on compressive, flexural and tensile strength at all temperatures compared with reference cement. Silica fume, styrene-butadiene rubber and styrene acrylic were added separately to the cement mortar without Glenium51, then a mixture of silica fume, styrene-butadiene, and styrene-acrylic was added to the cement mortar .The results showed that the compressive, flexural and tensile strength of cement mortar increase while styrene acrylic decrease these properties when compared with the reference mixture.In addition, the study showed the effect of temperature to the properties of added polymers with cement mortar, All experiments were performed at different temperatures (The temperature which Iraq's climate is exposed under natural conditions.All experiments were conducted at different temperatures (7, 20, 55)°C respectively, to show the effect of degrees on cement compressive strength, which the degree7 represents in winter, 20 in spring and autumn, and 55 in summer.

This study aims to produce pure titanium with differing porosity levels for use as a load-bearing implant material that can mimic natural bone structure. Ti + x space holder agent (x: 0, 5, 15, and 20 wt.%) samples were prepared via powder metallurgy route, employing a pressure of 300 MPa followed by sintering at 1200 °C for 6 h. Effect of the space holder agent on the pore characteristics, phase constituent, and mechanical performance, including elastic modulus and ultimate compressive strength, were investigated. Microstructural characterizations were conducted, employing an optical microscope, scanning electron microscopy and energy dispersive spectroscopy. The phase structure was characterized by X-ray diffraction. Additionally, the mechanical behaviour of the samples achieved was assessed by uniaxial compression test at room temperature. The results from the current studies revealed that adding space holder agent effectively modified the porosity level and pore characteristics without altering the phase constituent of the samples. As the space holder agent content was increased from 0 to 20 (wt.%), the porosity level of the samples increased from 18 % to 56 %, while the ultimate compressive strength values reduced significantly from 1,236 MPa to 112 MPa.

ZA-27 hybrid metal matrix composites reinforced with lamb bone ash (LBA) and boron carbide (B4C) were fabricated by employing stir casting route. Single-reinforced composite with 5 wt.% of LBA and hybrid composites reinforced with LBA/B4C in the ratio of (3.75:1.25, 2.5:2.5, 1.25:3.75) were developed. Composites were processed as per ASTM standards and subjected to physical characterization (density and porosity), microstructural characterization, and mechanical characterization (hardness, compressive strength, tensile strength, and impact strength). Microstructural studies of ZA-27 composites using a scanning electron microscope (SEM) revealed the uniform dispersion of reinforcements. X-ray diffraction (XRD) patterns and energy-dispersive X-ray spectroscopy (EDS) of the developed composites confirmed the existence of LBA and B4C particles in the matrix. The density of the composites declined, and porosity increased with the increment in B4C wt.% compared with base alloy. Mechanical properties like hardness, compressive strength, and tensile strength improved significantly in the case of hybrid composites than single-reinforced composite. Hardness, compressive strength and tensile strength of the hybrid composites increased to a maximum of 41.12%, 24.40%, 61.08% respectively compared to the base alloy, whereas single-reinforced composite showed maximum improvement of 19.26% (hardness), 11.16% (compressive strength), and 28.38% (tensile strength) compared to the base alloy. Ductility of the composites decreased with the addition of reinforcements. Impact strength of the composites showed a marginal reduction; however, the reduction was higher in the single-reinforced composite than hybrid reinforced composites. Fractured morphology showed dimples, cracks, tear ridges, and voids.

In this study, the relationships among compressive strengths with hydration mechanisms, microstructure characterizations and physical properties of diatomite-substituted cement pastes and mortars were researched. In order to determine the properties of cement pastes and mortars, X–ray diffraction, fourier transforms infrared spectroscopy, thermal analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques and standard cement tests were utilized at 2, 7, 28 and 90 days. The results revealed that portlandite content decreased gradually as a consequence of increasing age and addition of diatomite, and diatomite-substituted cements have high degree of hydration. Furthermore, the diatomite substituted cements had more compact structure by creating more hydration products at 28 and 90 days. This compact structure also positively contributed to the compressive strength of cement mortars at later ages.

Study of the effects of fine coral powder and salinity on the mechanical behaviour of coral sand-seawater cement mortar

Enhancing mechanical and thermal properties of sustainable cement mortar through incorporation of olive solid waste aggregates

Portland cement can be considered as the most important building materials because it is serving as the primary component in the manufacturing of mortar and concrete for diverse buildings., but cement production is associated with high carbon dioxide emissions when compared with other building materials. Therefore, it has a high impact on climate change around the world. Many types of materials were added to cement mortar and concrete to improve their properties and reduce the amount of cement in their mixtures. In this research to produce sustainable cement mortar, the effect of adding various siliceous materials (Silica (SiO2) is the main constituent) as pozzolanic materials on the properties of cement mortar with and without waste fine aggregate was investigated. The silica fume, silica powder, and waste glass powder were used to replace (2.5, 5, and 10) weight percentages of cement in the cement mortar mixture with natural sand. While 5% silica fume, 10% silica powder, and 5% waste glass powder were used to replace cement in cement, a 25-weight percentage of waste mortar was used as a fine aggregate to replace virgin aggregate in mortar mixtures. The flexural and compressive limits were evaluated for all cement mortar samples, while scanning electron microscopy (SEM) was characterized for some samples (control and high compressive strength). The findings indicate that the siliceous materials used in this study enhanced the compressive strength of cement mortar by altering its microstructure. The maximum compressive strength of 36.16 MPa was achieved. in samples that contained 5% silica fume in a standard cement mortar, while samples that contained 100% waste fine aggregate and 2.5% waste glass had a lower compressive strength ( 17.89 MPa) than all samples of cement mortar prepared by this research for 28 curing days.

Portland cement consists essentially of compounds of lime mixed with silica and alumina whereas zeolite is a kind of minerals containing high content of reactive silica and alumina. Therefore, there is a probability to apply zeolite in cement mortar in order to develop mortar properties. The purpose of this research was to study and analyze the efficiency of zeolite addition on properties of cement mortar. X-ray diffraction (XRD), universal testing machine (UTM) and scanning electron microscope (SEM) were used to characterize for mortar specimens. Mechanical property test was compressive strength according to ASTM C109 and carried out on 5 x 5 x 5 cm3 cube specimens at 1, 7 and 28 curing days. In this research, cement mortars were prepared by mixing type I Portland cement, fly ash, sand and zeolite. Zeolite was varied as 0, 0.25, 0.50 and 0.75 wt.% to cement and w/b (water to binder ratio) was 0.48. The results presented that the compressive strength of mortar with small amount of zeolite was improved since 1day age obviously comparing to that of mortar without zeolite. It was confirmed that zeolite would help strengthening the cement mortars at early strength.

Investigation of the effect of waterborne epoxy resins on the hydration kinetics and performance of cement blends

Concrete with high levels of Pozzolan suffers from poor early age strength development and an extended setting time and may therefore lead to construction delays thus limiting its use in the concrete industry. The main objective of this study has been to evaluate the effectiveness of calcium carbonate nano-particles (CCNPs) on improving the fresh and mechanical properties of high volume natural Pozzolan (HVNP) cement mortars. At the beginning, CCNPs have been synthesized in a simple and inexpensive way, and then the optimum content of nano-CaCO3 has been determined based on the highest compressive strength achieved by ordinary Portland cement mortar with different proportions of CaCO3 nanoparticles. In the end, the determined optimum content has been used in order to evaluate the effect of nano-CaCO3 on the properties of HVNP mortars containing 40% and 60% natural Pozzolan as partial replacement of cement. Scanning electron microscopy (SEM) and X-ray diffractometery (XRD) techniques have been used in order to investigate the microstructure, the properties, and the compositions of the synthesized nano-particles and the cement-Pozzolan mortars. CCNPs have been synthesized efficiently via the simple precipitation method and suitable sonication process has been used to disperse CaCO3 nanoparticles. The results have indicated that nano-CaCO3 has increased the compressive strength of the Pozzolan-cement mortars, and the best result has been obtained at an optimum content of 1% nano-CaCO3. The addition of nano-CaCO3 to the HVNP mortar improved its setting behavior; on the other hand, it has decreased its workability. However, this reduction in the workability has been offset by an increase due to partial replacement of cement by HVNP. Blending nano-CaCO3 with HVNP (40 and 60% replacement levels) has compensated for the low compressive and flexural strength at early ages of HVNP mortars. Thus, it has proved to be an effective way for improving the mechanical properties of high volume natural Pozzolan-cement mortars. The XRD and SEM results have confirmed that nano-CaCO3 has improved the early strength development and the microstructure of HVNP mortars by making it denser with less pores.

The aim of this study was to investigate the effect of montmorillonite as additive on the properties of cement paste and mortar. Montmorillonite was used at 0%, 5%, 10% and 15% additive by weight of cement, and the water/cement ratios of 0.45 and 0.55 are considered for the cement pastes and cement mortars with the sand/cement ratio of 1, respectively. Experimental results indicate that the use of montmorillonite as cement additives increases the compressive strength except the specimens containing 15% montmorillonite at the age of 28 days. The water absorption and initial surface absorption decreased with the increase of montmorillonite additives for the cement pastes. However, the cement mortars had an opposite test result in water absorption and initial surface absorption. The cement pastes and mortars containing montmorillonite have higher adsorption-desorption values than those of the plain cement pastes and mortars. Meanwhile, scanning electron microscopy and mercury intrusion porosimetry tests indicate that the cement paste containing montmorillonite are denser than that of the plain cement paste. X-ray diffraction analysis showed that the main hydration products are portlandite, hatrurite and calcite in cement paste and quartz and portlandite in cement mortar.