Mechanical Properties Of Cement Composites Research Articles

Durability and Mechanical Properties of Nano-SiO2 and Polyvinyl Alcohol Fiber-Reinforced Cementitious Composites Subjected to Saline Freeze-Thaw Cycles.

To investigate the effects of nano-SiO2 (NS) and polyvinyl alcohol (PVA) fibers on the durability and mechanical properties of cementitious composites subjected to saline freeze-thaw cycling, a series of PVA fiber-reinforced cementitious composite (PFRCC) specimens were prepared using various fiber contents, and a series of NS and PVA fiber-reinforced cementitious composite (NPFRCC) specimens were prepared using various combinations of NS and fiber contents. Durability and fracture toughness tests were subsequently conducted on the specimens after different numbers of saline freeze-thaw cycles. The results indicate that the degradation of material properties can be divided into slow and accelerated damage stages before/after 50 freeze-thaw cycles. The durability and fracture toughness of the specimen series tended to increase, then decrease with increasing NS and PVA contents, suggesting optimum levels. When the PVA fiber content was 0.5%, PFRCC specimens had the best durability after saline freeze-thaw cycles; when the NS and PVA fiber contents were 1.0% and 0.5%, respectively, NPFRCC specimens had the best durability and fracture properties, and the initiation toughness, destabilization toughness, and fracture energy after 100 saline freeze-thaw cycles were 120.69%, 160.02%, and 451.31%, respectively. The results of this study may guide future exploration of the durability and mechanical properties of concrete subjected to freeze-thaw action.

Predicting the compressive strength of carbon-enhanced cementitious composites using two-dimensional convolutional neural networks

This study addresses the limitations of traditional statistical methods and artificial neural networks (ANNs) in extracting relevant features from carbon-based cementitious composites to assess their dynamic behaviors under various environmental conditions. However, previous deep-learning methods were limited in making efficient predictions utilizing multiple factors. These shortcomings are not appropriate for predicting the properties of cement composed of various elements. In this study, these elements were converted into image form to handle efficiently the multiple factors that consist of cement, and the prediction was performed using a convolutional neural network (CNN)-based model. The concentration range of multiwalled carbon nanotubes (MWCNTs) used was 0.25 wt % to 1.0 wt %. Additionally, the specimens utilized were 50×50×50mm3 in size, and a total of 532 pieces of data were employed. Based on mean absolute error (MAE), performance was improved by approximately 25 % with ANN (MAE = 3.89) and 7.2 % with random forest (MAE = 3.14) compared with the proposed model (MAE = 2.92). The findings of this study are a novel and practical approach for predicting the mechanical properties of cementitious composites, enabling reverse application to optimize mixing ratios for CNT cement composites, and streamlining fabrication.

Effect of wet milling activation on mechanical properties and hydration process of cement composites with blast furnace slag

In this study, blast furnace slag (BFS) was activated using water- and ethanol-assisted milling (AM). BFS-cement composites (BFS-CC) were prepared using milled BFS and cement. The effects of the activation process on the mechanical properties and hydration of BFS-CC were investigated. Results showed that water- and ethanol-AM significantly reduced the median particle size (D50) and improved the particle size distribution of BFS compared to dry milling. Water-AM increased the compressive strength of BFS-CC at 3 days by 19.9 % and decreased the compressive strength at 28 days by 6.7 %. While ethanol-AM increased the compressive strengths at 3 and 28 days by 17.2 and 22.4 %, respectively. Water-AM improved the early strength of BFS-CC, whereas ethanol-AM contributed significantly to the late strength development of BFS-CC. This study provides an effective and convenient method for regulating the mechanical properties of cement composites containing high-volume BFS.

Predictive Modeling and Experimental Validation for Assessing the Mechanical Properties of Cementitious Composites Made with Silica Fume and Ground Granulated Blast Furnace Slag

Using sustainable cement-based alternatives, such as secondary cementitious raw materials (SCMs), could be a viable option to decrease CO2 emissions resulting from cement production. Previously conducted studies to determine the optimal mix designs of concrete primarily focused on either experimental approaches or empirical modeling techniques. However, in these experimental approaches, few tests could be performed for optimization due to time restrictions and lack of resources, and empirical modeling methods cannot be relied on without external validation. The machine learning-based approaches are further characterized by certain shortcomings, including a smaller number of data points, a less robust connection among the controlling factors, and a lack of comparative analyses among machine learning models. Furthermore, the literature on predicting the performance of concrete utilizing binary SCMs (silica fume (SF) and ground granulated blast furnace slag (GGBS)) is not available. Therefore, to address these drawbacks, this research aimed to integrate ML-based models with experimental validations for accurate predictions of the compressive strength (CS) and tensile strength (TS) of concrete that includes SF and GGBS as SCMs. Three soft computing techniques, namely the ANN, ANFIS, and GEP methods, were used for prediction purposes. Eight major input parameters, including the W/B ratio, cement, GGBS, SF, coarse aggregates, fine aggregates, superplasticizer, and the age of the specimens, were considered for modeling. The validity of the established models was assessed by using external experimental validation criteria, statistical metrics, and performance measures. In addition, sensitivity and parametric analyses were performed. Based on statistical measures, the ANFIS models outperformed other models with higher correlation and lower statistical error values. However, the GEP models exhibited superior performance compared to ANFIS and ANN with respect to the closeness of the RMSE, MAE, RSE, and R2 values between the training, validation, and testing sets for both the CS and TS models. Experimental validation showed strong evidence for the applicability of the proposed models with an R2 of 0.88 and error percentages of less than 10%. Sensitivity and parametric investigations demonstrated that the input variables exhibited the patterns described in the experimental dataset and the available literature. Hence, the proposed models are accurate, have better prediction performance, and can be used for design purposes.

THE INFLUENCE OF TOTAL WATER-TO-CEMENT RATIO ON THE MECHANICAL PROPERTIES OF CEMENTITIOUS COMPOSITES INTERNALLY CURED WITH POLYACRYLIC SUPERABSORBENT POLYMERS (SAP)

Superabsorbent polymers (SAP) allow for the introduction of changes to the pore network characteristics in cementitious composites and the course of binder hydration. Therefore, SAP addition contributes to significant changes in multiple properties of concrete. The effect of internal curing differs depending on its design process – the initial content of curing water in the concrete mix, polymer characteristics and water absorption properties, the state in which it’s added (nonsaturated/hydrogel), and the design method regarding curing water content in the entire water content. The authors investigated those variables’ influence on selected concrete properties – compressive strength, water absorption, and shrinkage. All independent variables significantly influenced the studied properties of concrete. The increase in the total water-to-cement ratio led to a significant decrease in the mechanical properties of cementitious composites. Modification with the use of SAP added in the form of hydrogel had the most positive influence on the properties of concrete.

Analysis of the influence of mechanical properties of cementitious composites using submerged arc welding (SAW) slag recycled aggregate

Concern about the environment and the scarcity of natural resources has led to the search for more sustainable alternatives that minimize the environmental impact of all segments of society. Solid waste recycling has been presented as a good alternative to reduce the impacts generated by the disorderly use of raw materials and the reduction of disposal areas, caused by the large volume of waste disposal generated throughout the year throughout the world. In this context, waste from industries in Brazil is included, especially submerged arc welding (SAW) slag. Waste from these activities is generally solid, with dense materials and variable characteristics in terms of their chemical composition, as they contain different types of elements with a specific function as a load element. These characteristics often present an obstacle to being reused in new materials (flows). Among the various waste generated by various industries, we can mention submerged arc welding (SAW) slag, as being one of the greatest potentials for use, due to often having knowledge of its basic characteristics and properties and its lower degree of contamination by other materials, when compared to other waste, such as construction waste. The objective of this research is to evaluate the mechanical performance characteristics of cementitious matrices made with submerged arc welding (SAW) slag residue and their possible use on a large scale. Cementitious matrices for mortars were manufactured by replacing 0%, 25%, 50% and 75% of the natural fine aggregate with submerged arc welding (SAW) slag residue and a water/cement ratio of 0.48. Through the compressive and tensile strength test, it was observed after 28 days that the cement matrices with replacements obtained increases in the mechanical properties of compressive and tensile strength, compared to the reference cement matrix.

Towards development of cement-based composites reinforced with architected 3D-printed polymers

In the present work, mortar beams reinforced with polymeric reinforcing elements are manufactured using Polylactic acid (PLA), inspired by crack propagation deflecting architectures found in nature such as Sinusoidal and Bouligand architectures. Mechanical flexural properties of mortar beams are studied and compared with that of reinforcing elements with an architecture parallel to the direction of tensile stress as well as non-reinforced mortar beams. Furthermore, the reinforcement configuration and ratio are designed using principles from mechanics of materials. A Digital Image Correlation (DIC) technique is used to obtain the load-deflection curves during flexural evaluation. Results show that changing the microarchitecture of the reinforcement can enhance the flexural performance of the beam. Additionally, interface properties between the mortar and the reinforcing element are studied using pull-out tests. Interface properties were enhanced by introducing architectural patterns on the surface of the reinforcement. Finally, using material properties of the mortar, reinforcement and the interface obtained from experiments, a numerical model is developed and calibrated. The outcome of this study helps explore the opportunities of using novel nature-inspired reinforcement to enhance the mechanical properties of cementitious composites.

Shrinkage cracking and mechanical properties of cementitious composites produced with multiwall carbon nano tubes and different types of polypropylene fibres

This study was conducted to experimentally demonstrate the control the nano-, micro- and macro-scale cracking in cement-based composites by using nano-, micro- and macro-scale fibres. While micro, macro and hybrid system polypropylene (PP) fibres were used in concrete designs, micro-scale PP and multi-walled carbon nano tubes (MWCNT) were utilized in mortar mixtures. The progression of the cracks was monitored in accordance with a well-known standard and also with a modified method which enabled the investigation of plastic and restrained shrinkage. Fracture energy, flexural strength, compressive strength, modulus of elasticity and ultrasonic pulse velocity of the samples were also determined as the mechanical properties of the composites. Results showed significant improvements in the reduction of cracks, especially with hybrid fibres system.

Effects of a novel carbon nanomaterial on hydration, mechanics, and chloride binding of cement composites

Nanomaterials have made significant progress in the field of cementitious materials, but suffer from primary problems of high cost and poor dispersity. Carbon dots (CDs) as a novel low-cost and high-dispersity nanomaterial preliminarily demonstrate their potential for cement. Nevertheless, it lacks systematic research on their effects on cement properties. For the first time, this work comprehensively investigates the effects of CDs on the hydration, mechanics, and chloride binding of cement composites. More importantly, the relevant mechanisms are revealed in depth. Specifically, cost-efficient ($0.013/g) and well-dispersed (dispersed in simulated concrete pore solution for 7 d) CDs are directly prepared by a facile microwave approach. The CDs dramatically retard the early hydration, improve later mechanical performance, and obviously enhance chloride binding. In detail, 0.2 wt% CDs reduce the second exothermic peak value by 75%, but improve the chloride binding capacity of paste by 51%. And 0.1 wt% CDs enhance the compressive/flexural strength of mortar by 17%/21%. Crucially, related influence mechanisms are uncovered. Namely, CDs create a protective barrier to retard hydration through the complexation of their abundant surface groups with Ca2+; While CDs exert the nucleation effect to boost the formation of C–S–H and Friedel's salt, thereby playing a positive impact on chloride binding; Meanwhile, CDs with suitable dosages carry out nucleation effect to counteract their air-entraining effect, thus improving later mechanical properties of cement composites. This study is expected to provide a novel low-cost and high-dispersity CDs nanomaterial to advance the development of high-performance cementitious materials.

Utilizing industrial byproducts for the manufacture of clay-cellulose nanocomposite cements with enhanced sustainability

This study investigates the influence of different nano clay contents (0, 1, 3, and 5 wt% of cement) on the microstructure and the mechanical properties of cement composites reinforced with varying Nano cellulose fiber contents (0, 0.5, 0.75, and 1 wt% of cement). Unlike previous research that employed sonication to improve dispersion in the cement matrix, this study explores the effects of unsonicated nano-cellulose addition and the combined incorporation of nano-cellulose and nano-clay. The results demonstrate that these additions significantly enhance the compressive strength, abrasion resistance, and water absorption ratios of the cement composites. Furthermore, the inclusion of nano-clay improves the microstructure of the cement matrix, strengthening the interfacial transition zone and reinforcing the bond between nano-cellulose and the cement matrix. The microstructural analysis using scanning electron microscopy (SEM) reveals the presence of a dense interconnected structure characterized by rod-like crystals. This research contributes to the development of sustainable construction materials by examining the effects of nano-cellulose and nano-clay on the properties and microstructure of cement composites. The utilization of industrial byproducts, such as wood sawdust, for the extraction of nano-cellulose offers an eco-friendly approach to enhance the performance of cement-based materials. The maximum compressive strength obtained, after 28 days, was at mix with 0.75% NCL + 5%NC with a gain of 53.5% than that of the control mix. In mixes containing only nano-clay (NCL), the increase in NCL content led to a higher rate of water absorption in the cement matrix, which reaches 4%. Confirming the results obtained from compressive strength and water absorption, mix with 0.75% NCL and 5% NC had obtained the optimum values with an improvement of 20% than that of the control mix.

Analysis of the Influence of PET and Glass Packaging Waste Materials on the Physical and Mechanical Properties of Cementitious Composites

The limited availability of natural resources, such as sand, and the need to reduce CO2 emissions, which are produced in large quantities in the production of binding materials, indicate the need to look for alternative raw materials used in construction materials. At the same time, there is a strong need to utilise waste packaging materials, the global production of which is constantly increasing. This work aims to investigate the possibility of using recycled polyethylene terephthalate (PET), utilised as a partial substitute for fine aggregate, and waste glass, implemented as powder, serving as a partial substitute for cement in the manufacturing of the cementitious composites. An experimental study was carried out to evaluate the physical and mechanical properties of the resultant cementitious composites. The incorporated PET aggregate comprised 0%, 5%, and 10% by volume of silica sand and 0%, 10%, and 20% glass powder by weight of cement. The addition of waste raw materials augmented the flow of fresh mortars, predominantly subsequent to the introduction of PET recyclate. The deployment of artificial aggregate in mortars induces a decrease in the volumetric density. Concurrently, the mechanical properties of mortars enriched with waste materials exhibited a reduction, in terms of both compressive and flexural strength, with the detriment escalating in conjunction with the content of waste raw materials. An analysis of statistical significance of effects, grounded in an analysis of variance, is delineated within this document, pinpointing the quantities of waste raw materials that can be assimilated in mortars without inducing a substantial deterioration of strength properties. Through studies on phase composition, it has been demonstrated that the utilised glass waste, possessing a grain size analogous to cement, exhibited poor pozzolanic properties. The test results indicate that it is possible to partially replace cement with glass powder, up to 10%, and fine aggregate with PET waste, up to 5%, without a significant reduction in the mechanical properties of the material.

Graphene nanoribbons as a novel nanofiller for enhancing the mechanical and electrical properties of cementitious composites

Several functional fillers have been used to modify the mechanical and electrical properties of cement-based materials. Graphene nanoribbons (GNRs) have attracted considerable attention as the next generation of carbon-based nanomaterials owing to their excellent properties. This paper aims to assess the influence of GNRs with varying incorporation amounts (0.05, 0.10, and 0.15 wt% of cement) on the mechanical properties, hydration behavior, and electrical properties of ordinary Portland cement paste via mechanical strength test, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, and alternating current electrochemical impedance spectroscopy. The enhanced performance of GNRs in cementitious composites was compared with that of carbon nanotubes (CNTs), which are one of the most popular and conventional nano-reinforcing agents for cement-based materials. The results of this study show that, compared to CNTs, GNRs significantly decrease the resistivity of cementitious composites owing to their excellent electrical properties. Furthermore, after the exfoliation of CNTs, GNRs possess a larger specific surface area and exhibit improved dispersibility. Thus, GNRs provide better nucleation and filling effects for cementitious composites to promote the hydration reaction of cement clinkers and modify the microstructure of the cement matrix, resulting in enhanced mechanical properties of the cementitious composites.

Effect of multi-walled carbon nanotube/Porous Carbon/SiO2 on reinforcing of cement mortar matrix: Modeling studies of effective parameters

The enhancement of the mechanical properties of cement composites by various nanomaterials is now a trendy subject. This study assessed the impact of three nanomaterials on the compressive and tensile strength of Portland cement mortar: biomass-derived porous carbon, MWCNT, and SiO2. These nanoparticles were developed using environmentally friendly, inexpensive technologies, and they underwent material characterization analyses using FESEM, N2 adsorption-desorption, contact angle, FTIR, XRD, and TEM. After 7 and 28 days, the compressive and tensile strength was assessed. According to the findings, among the samples, cement-SiO2 had the maximum compressive strength (19.32 MPa). The FESEM micrographs amply support the creation of the C-H-S gel and the presence of the bridge. The outcomes further showed that the nanoparticle's presence in the matrix does not significantly impact the tensile strength. SiO2-cement had the highest tensile strength, 1.45 MPa, matching the conclusions drawn from the compressive strength. Moreover, the compressive strength of cement was unaffected by the total pore volume of nanomaterials or the pore-filling mechanism of cement. Modeling (Linear regression-least square method) made it possible to predict the compressive strength for a period of 92 days and examine the influence of effective ingredients on it. Ultimately, the results indicate that porous carbon and silica can be viable alternatives for MWCNT.

Preparation of In(OH)3@GO with high surface roughness and its effect on the hydration performance, microstructures and mechanical properties of cement composites

The smooth surface of graphene oxide (GO) leads to a limited interaction with hydrated cement paste, which severely compromises its benefits to improve the properties of cement composites. In this study, GO dispersion (GOD) and indium chloride were employed to prepare In(OH)3 loaded GO (In(OH)3@GO) with high surface roughness and specific surface area. In(OH)3@GO obtained using indium chloride and GOD at a mass ratio of 4:100 (IG-4) exhibited increases in surface roughness and specific surface area of 67.6 % and 49.9 %, respectively, compared to GO without In(OH)3 (IG-0). In(OH)3@GOs were introduced into cement composites to analyse the impacts of varied In(OH)3 loading on mechanical properties, hydration performance and microstructure. Compared to IG-0, GO loaded with various amounts of In(OH)3 exhibited beneficial effects on cement composites. In particular, cement composite with IG-4 exhibited compressive strength improved by 26.4 %, flexural strength improved by 38.1 % and total pore volume reduced by 32.4 %.

The effects of apricot kernel shell nanobiochar on mechanical properties of cement composites

Valorization of agricultural wastes is important both economically and environmentally. This study aimed to investigate the use of biochar as a filler to improve the mechanical properties of mortar and to help sequestrate CO2. The biochar was produced by pyrolysis of apricot kernel shell at 500 °C. Nanobiochar particles with dimensions less than 500 nm were obtained by high-energy ball milling process. Scanning electron microscope was used for determining the morphology of nanobiochar. The nanobiochar at different volume percentages [0.00-0.04-0.06-0.08-0.12-0.15%] was added to mortar. The mortar was casted into 40x40x160 mm molds. After water curing at 20°C for 28 days, compressive strength and flexural strength tests were performed. The mixture containing 0.04% nanobiochar by volume had an increase in flexural and compressive strengths by 5% and 15% respectively, while its fracture energies for flexure and compression increased by 98% and 38% respectively compared to the reference mortar. Furthermore, the mixture having 0.12% volume had an increase in flexural and compressive strengths by 32% and 11%, respectively, while the increase in fracture energies for flexure and compression was 52% and 25%, respectively, compared to the reference mortar. The mechanisms of nanobiochar effect on flow, strength, and fracture energy were enlightened. The nanobiochars bridge the cracks, divert the cracks, act as hydration nucleation sites, enhance the matrix by its porous structure, and developed internal curing that led to increase in strength and fracture energy. This study suggests that the biochar produced from the apricot kernel shell has the potential to be used as a carbon sequestering mixture to improve performance of mortar and thereby utilizing waste as a construction material, contributing to the economy and environment.

Multifunctional properties of carbon fiber integrated cement composite – A review and insights

This article examines the strength characteristics of carbon fiber-reinforced cement composite (CFRCC). The research explores the residual mechanical characteristics and microstructure of concrete reinforced with carbon fiber. The review also focused on the determination of the effect of CFRCC on the improvement of strength, microstructure, crystalline phase shift, and hydration products of the cement composites. The review indicates that the inclusion of carbon fibers can intensify the flexural and splitting strengths of CFRCC, but the compressive strength is magnified to a lesser extent. In addition to the initial elastic modulus and peak stress of carbon fiber-reinforced cement composite, a discernible strain-rate hardening effect was also observed. This indicates that carbon fiber-reinforced cement composite has a promising future as cement composite reinforcements. The review of the characteristics of the composites also suggests their applicability in tunnel building in the cement composite. It is determined that carbon fiber-reinforced cement composite has a stronger capacity to withstand impact loads, and further information about its features will be supplied. The scanning electron microscopy (SEM) result demonstrates that the single and most significant failure mode under stress is carbon fiber breaking and the pull-out of carbon fibers. Thus, the review reveals that carbon fibers have a limited but positive act on enhancing the mechanical properties of cement composites.

Carbon nanotubes-coated cement particles for cement-based sensors with excellent piezoresistivity

Typically, self-sensing cement composites are prepared by directly mixing cement particles with conductive additives, such as carbon black, carbon nanotubes (CNT), and graphene. This study proposes a novel approach to directly coat cement particles with CNT as the conductive filler (CNT@cement) before contact with water, aiming to develop a high-performance self-sensing cement-based sensor. CNT@cement nano/micro hybrid fabrication relies on a simple and efficient method that enables the uniform absorption of CNT on the surface of cement particles without any surfactants, thereby not diminishing the workability and mechanical properties of cement composites. This cement composite exhibits improved microstructure, bending strength, and electrical conductivity. Remarkably, the formulation with the addition of 0.1 wt% CNT@cement hybrid increases the bending strength by about 23% and improves the electrical conductivity by approximately two orders of magnitude, outperforming previously reported cement composites with similar CNT content. Additionally, outstanding piezoresistivity with a fractional change in resistivity of 1.26 is achieved for our cement-based sensor. These findings represent a major step toward the practical application of CNT in structural health monitoring.

Flexural creep of multi-wall carbon nanotube reinforced cement based composites under high stress level

Different concentrations (0–0.2 wt.%) of multiwall carbon nanotubes (MWCNT) was used to improve the mechanical properties of cementitious composites. The first part of the work showed that adding 0.05 wt.% of MWCNT produced a maximum reinforcement in terms of flexural and compressive strength. The second, the role of MWCNT on mechanical strength improvement was investigated. MWCNTs can absorb water to weaken the cement hydration at the beginning, and then, release water to promote the hydration of cement. The third part focused on using a home-made four-point bending testing device to study the flexural creep behavior under high stress levels (70, 80 and 90% of the flexural strength) and the results are discussed in terms of creep strain and Poisson ratio difference. The data obtained were also compared with the empirical creep models and the creep coefficients obtained were agreement with that from the AASHTO model. Finally, a regression analysis was used to fit the creep compliance of MWCNTs reinforced cementitious composites for the range of conditions studied. The results showed that the creep compliance can be fitted by a power-law for a stress level below 0.85, while a linear function was obtained above.

Modeling and Optimization of Date Palm Fiber Reinforced Concrete Modified with Powdered Activated Carbon under Elevated Temperature

Date palm fiber (DPF) is one of the abundant solid waste materials in the agriculture sector in Saudi Arabia, and it is gaining great attraction due to its advantages compared to synthetic and other natural fibers. For proper utilization of DPF in cementitious composites, its performance under high temperatures needs to be understood. This is because DPF is a cellulose-based agricultural fiber material and is expected to degrade when subjected to high temperatures. This will cause a significant loss in strength and structural integrity of the composites. The use of Pozzolanic materials has been reported to reduce the loss in mechanical properties of cementitious composites under high temperatures. With powdered activated carbon (PAC) being a low-cost material compared to other Pozzolanic materials, this study utilized PAC as an additive to the DPF-reinforced concrete to mitigate its loss in mechanical strength when exposed to elevated temperature. The experiment was designed using response surface methodology (RSM), which was used to construct mathematical models for estimating the strengths of the concrete exposed to high temperatures. The DPF was added at proportions of 1%, 2%, and 3% by weight of cement. Similarly, the PAC was added at 1%, 2%, and 3% by weight of cement to the concrete. The concrete was subjected to elevated temperatures of 300 °C, 600 °C, and 900 °C for a 2 h exposure period. The degradation of the concrete in terms of mass loss and the compressive strength of the concrete after heating were measured. DPF in the concrete led to an escalation in weight loss and reduction in strength, which was more pronounced at a temperature of 600 °C and above. The addition of PAC resulted in an enhancement in the strengths of the concrete containing up to 2% DPF at 300 °C, while at 600 °C the improvement was minimal. The models developed for predicting the mass loss and strengths of the DPF-reinforced concrete under high temperatures were statistically significant with a high correlation degree. Based on the optimization results, DPF-reinforced concrete produced with 1% DPF, and 2.27% PAC as additives and subjected to a temperature of 300 °C for 2 h yielded the lowest mass loss of 2.05%, highest residual compressive strength and relative strength of 45.85 MPa and 106.7% respectively.

Date and doum palm natural fibers as renewable resource for improving interface damage of cement composites materials

BackgroundVarious recent studies have investigated the use of traditional fibers (metallic or synthetic) as reinforcement in mortar. In recent times, there has been growing interest in using natural fibers as reinforcement in cement composites. This study was conducted to assess the impact of date palm, doum palm, and sisal fibers on the mechanical properties of cement composites. Genetic modeling was chosen to find the shear damage at the fiber-matrix interface of the three cement composites using genetic crossing operator, which allows us to calculate the damage at the interface using two damages of the matrix and the fibers, respectively.ResultsOur objective is to examine and evaluate the interface damage of date palm/mortar, doum palm/mortar and sisal/mortar under different mechanical tensile stresses ranging from 25 to 37 MPa with fiber volume fraction from 1 to 5%. It was found that the interface damage of date palm/mortar and doum palm/mortar cement composites was minimal compared to that of sisal/mortar. However, several researchers found that an increase in fiber volume fraction leads to decrease in mechanical properties and density in cement composites what we confirmed in this study that interface damage increases when the volume fraction increases.ConclusionsThe results are in line with the findings of a recent experimental study on the use of other plant fibers. Their results showed that incorporating ramie fibers resulted in a 27% increase in compressive strength, whereas the use of synthetic fibers resulted in 4% decrease in tensile strength in compression. It is recommended the use of doum and date palm natural fibers in the composition of mortars with a fiber volume fraction of 1 to 5% in order to reduce and avoid interface damage and limit the negative impact of synthetic fibers on the environment.