Compressive Strength Of Cement-based Materials Research Articles

The Study of Effect of Carbon Nanotubes on the Compressive Strength of Cement-Based Materials Based on Machine Learning

The Study of Effect of Carbon Nanotubes on the Compressive Strength of Cement-Based Materials Based on Machine Learning

Predicting Compressive Strength of Cement-Based Materials Containing Hydroabsorbent Polymers Considering the Internal-Curing Region

Predicting Compressive Strength of Cement-Based Materials Containing Hydroabsorbent Polymers Considering the Internal-Curing Region

Water distribution and transport-kinetics model in fresh cement-based mixtures containing superabsorbent polymers based on 1H low-field NMR

Superabsorbent polymer (SAP) can be used as a curing agent in cement-based materials. Due to the replenish of humidity decline caused by the continuous consumption of water, the SAPs will contribute substantially to mitigating the shrinkage and obtaining the expected curing efficiency. Many studies have described the characteristics of water immigration in SAP-modified cement-based mixtures, but the travelled distance, volume, and transport-kinetics model of the water released from the SAP in cement-based materials still need to be investigated in detail. The paper focuses on the sustained water distribution of SAP at early-age cement-based mixtures. The swelling characteristics of SAP in different liquids and the water transport kinetics in hydrating cement-based mixtures were studied based on the ion concentration test and low-field Nuclear Magnetic Resonance (NMR) measurement. The results show that when SAP is in contact with water or cement filtrate, the exchangeable cations on the SAP structure will move freely to the solution and rapidly exchange with the metal cations in the solution within a few minutes (about 5 min). The most predominant form of water in fresh cement-based mixtures was the absorbed water (adsorbed on the surface of particles or in pores). Part of the adsorbed water or small capillary water on the surface of cement particles was consumed for hydration. The incorporation of SAP can prevent bleeding and segregation and promote the 28-day compressive strength of cement-based materials under the same total w/c ratio. Finally, the water-transport model in fresh cement-based mixtures was established and verified.

Effect of Nano-Si3N4 on the Mechanical Properties of Cement-Based Materials

In this paper, in order to improve the wear resistance of road cement, nano-Si3N4 (NSN) was incorporated into cement, and the effect of NSN on compressive strength and wear resistance of road cement was investigated. The main variable of the experimental investigation was the dosage of NSN. The experimental results showed that the addition of NSN could significantly improve the compressive strength and wear resistance of cement paste. Compared with the reference group, the wear resistance can be improved by 46.5% and the compressive strength of cement paste can be improved by 12.3% when the addition of NSN is 0.16% by weight. In addition, the improvement mechanisms of NSN on cement paste were revealed by hydration heat, XRD, DTA-TG, nanoindentation, nitrogen adsorption, and SEM for microscopic phase tests. Through the microscopic analysis, the addition of NSN can accelerate the hydration reaction and promote the hydration degree, optimize the pore structure, and make the cement paste more compact. Additionally, NSN can improve the performance of the interface transition zone (ITZ) and increase the content of HD C-S-H gel. The action mechanism of NSN is mainly dominated by the surface effect, filling effect, and larger surface energy of NSN thereby improving the mechanical properties of cement-based materials. These research results have guiding significance for the design of the high wear resistance and high compressive strength of cement-based materials.

Study on the Effects of Ultrasonic Agitation on CO2 Adsorption Efficiency Improvement of Cement Paste

To realize high-efficiency CO2 absorption by fresh cement paste, ultrasonic vibration technology is introduced into the CO2 absorption test device used in this study. Influences of ultrasonic frequency on the CO2 absorption rate (CO2 AR) and the ultimate absorption amount of fresh cement paste are analyzed. Furthermore, the influencing laws of the CO2 absorption amount (CO2 AA) on the fluidity, pore distribution, and mechanical properties of cement paste under ultrasonic vibrating agitation are analyzed by measuring the variations of the CO2 AA of cement paste. Results demonstrate that ultrasonic vibrating agitation not only can increase the CO2 AR and ultimate absorption amount of fresh cement paste, but also can optimize the internal pore structure of materials and compressive strength of cement-based materials.

Estimating the Compressive Strength of Cement‐Based Materials with Mining Waste Using Support Vector Machine, Decision Tree, and Random Forest Models

To estimate the compressive strength of cement‐based materials with mining waste, the dataset based on a series of experimental studies was constructed. The support vector machine (SVM), decision tree (DT), and random forest (RF) models were developed and compared. The beetle antennae search (BAS) algorithm was employed to tune the hyperparameters of the developed machine learning models. The predictive performances of the three models were compared by the evaluation of the values of correlation coefficient (R) and root mean square error (RMSE). The results showed that the BAS algorithm can effectively tune these artificial intelligence models. The SVM model can obtain the minimum RMSE, while the BAS algorithm is inefficient in DT and RF models. The SVM, DT, and RF models can be used to predict the compressive strength of cement‐based materials using solid mining waste as aggregate effectively and accurately, with high R values and lower RMSE values. The RF algorithm can obtain the highest value of R and the lowest value of RMSE, demonstrating the highest accuracy. The solid mining waste to cement ratio is the most important variable to affect the compressive strength. Curing time was also an important parameter in the compressive strength of cemented materials, followed by the water‐solid ratio of mining waste and fine sand ratio.

Effect of diameter of multi-walled carbon nanotubes on mechanical properties and microstructure of the cement-based materials

This paper is intended to investigate the effects of multi-walled carbon nanotubes (MWCNTs) with different inner diameters on the mechanical properties (flexural strength and compressive strength) and microstructures of cement-based materials. Three kinds of multi-walled carbon nanotubes (MWCNTs) with diameter of 10–20 nm, 20–40 nm and 40–60 nm were ready to reinforce cement-based materials. And each batch incorporated 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt% MWCNTs by cement weight. To obtain a uniform distribution of MWCNTs in the cement-based materials, the effects of ultrasonic dispersion time and intensity on the properties of MWCNTs cement-based materials were studied. In addition, the relationships between mechanical properties, porosity and diameter of MWCNTs were investigated. Experimental results showed that the improvements of flexural strength and compressive strength of cement-based materials were altered by increasing the diameter of MWCNTs. Microstructure analysis by SEM and MIP tests indicated that MWCNTs with diameter of 10–20 nm have the best effect on optimizing pore structure. The results of this study were useful to determine the diameter and content of MWCNTs required for optimum pore structure and maximum strength enhancement of cement-based materials.

Hydrophobicity Improvement of Cement-Based Materials Incorporated with Ionic Paraffin Emulsions (IPEs).

Cement-based materials are non-uniform porous materials that are easily permeated by harmful substances, thereby deteriorating their structural durability. In this work, three ionic paraffin emulsions (IPEs) (i.e., anionic paraffin emulsion (APE), cationic paraffin emulsion (CPE), and non-ionic paraffin emulsion (NPE), respectively) were prepared. The effects of incorporation of IPEs into cement-based materials on hydrophobicity improvement were investigated by environmental scanning electron microscopy (ESEM), Fourier transform infrared (FTIR) spectroscopy, transmission and reflection polarizing microscope (TRPM) tests and correlation analyses, as well as by compressive strength, impermeability, and apparent contact angle tests. Finally, the optimal type and the recommended dose of IPEs were suggested. Results reveal that the impermeability pressure and apparent contact angle value of cement-based materials incorporated with IPEs are significantly higher than those of the control group. Thus, the hydrophobicity of cement-based materials is significantly improved. However, IPEs adversely affect the compressive strength of cement-based materials. The apparent contact angle mainly affects impermeability. These three IPEs impart hydrophobicity to cement-based materials. In addition, the optimal NPE dose can significantly improve the hydrophobicity of cement-based materials.

Ultra-high strength cement-based composites designed with aluminum oxide nano-fibers

The use of nanomaterials has become a popular way to improve the performance of cement-based composites. At the same time, ultra-high strength concrete is becoming more widely used. These materials provide superior durability to infrastructure elements, reducing the need for maintenance or early replacement. The performance boost is achieved by producing a denser microstructure and, in the case when nanofibers are used, may reduce the initiation of cracks. Aluminum oxide nanomaterials have the potential to provide a significant increase in compressive strength of cement-based materials. Here, the effect of incorporation of aluminum oxide nanofibers in oil well cement based mortars and composites is reported. The design of ultra-high strength concrete often requires a precisely tuned aggregate gradation, the use of specific cement types and high quantities of silica fume and superplasticizers along with high temperature and curing under elevated pressure. It was demonstrated that the use of small quantities of aluminum oxide nanofibers in an oil well cement based mortar could provide a compressive strength approaching 200 MPa. These levels were achieved at a considerably lower dosage of silica fume. It is envisioned that the high strength matrix is formed due to the reinforcing of calcium silicate hydrate layers which are formed around the nanofibers. This research demonstrated that due to a “shish kebab” effect the addition of well-dispersed aluminum oxide nanofibers at a very small dosage of 0.25% (by mass of cement) could provide up to 30% increase in compressive strength of cementitious systems, helping to meet the benchmarks for ultra-high strength cement-based composites.

Effect of Chelating Additive on Pore Structure and Mechanical Property of Mortar under Different Curing Conditions

Effect of chelating additive on microstructure, hydration products and mechanical property of mortar under different curing conditions was investigated. The microstructure was tested by nuclear magnetic resonance and scanning electron microscope. And the chemical composition of hydration products was analyzed by X-ray diffraction. The compressive strength was measured under different curing conditions at different curing age, including standard curing, water immersion, seawater immersion and salt mist curing. After curing for 28 days in water, compared to control mortar, the reduction ratio of harmful pores whose size larger than 0.1μm in mortar with chelating additive (CA mortar) was 14.6%, followed by 8.9%, 9.2% and 2.9% which was under standard curing, seawater immersion and salt mist curing, respectively. From the scanning electron microscope image, there were more needle-like and bar-like crystals in CA mortar making it more compact, which was mainly calcium silicate hydrate through component analysis. Besides, the raising percentage of compressive strength of CA mortar under water immersion is 28.6% compared to control mortar at the age of 28 days, followed by 26.8%, 21.8% and 16.3% which was under standard curing, seawater immersion and salt mist curing, respectively. The results indicate that chelating additive can enhance compactness and compressive strength of cement-based materials especially under water immersion by promoting the formation of calcium silicate hydrate.

An approach for predicting the compressive strength of cement-based materials exposed to sulfate attack.

In this paper, a support vector machine (SVM) model which can be used to predict the compressive strength of mortars exposed to sulfate attack was established. An accelerated corrosion test was applied to collect compressive strength data. For predicting the compressive strength of mortars, a total of 638 data samples obtained from experiment was chosen as a dataset to establish a SVM model. The values of the coefficient of determination, the mean absolute error, the mean absolute percentage error and the root mean square error were used for evaluating the predictive accuracy. The main factors affecting the predicted compressive strength were obtained by sensitivity analysis. A SVM model was calibrated, validated, and finally established. Moreover, the performance of the SVM model was compared to an artificial neural network (ANN) model. Results show that the prediction values from the SVM model were close to the experimental values; the main factors sensitive to concrete compressive strength were exposure time, water-cement ratio and sulfate ions; the performance of the SVM model was better than the ANN model. The SVM model developed in this study can be potentially used for predicting the compressive strength of cement-based materials servicing in harsh environments.

Microstructure, characterizations, functionality and compressive strength of cement-based materials using zinc oxide nanoparticles as an additive

Zinc oxide nanoparticles as a nanophotocatalyst has great potential for self-cleaning applications in concrete structures, its effects on the cement hydration, setting time and compressive strength are also important when using it in practice. This paper reports the effects of zinc oxide nanoparticles, as an additive material, on properties of cement-based materials. Setting time, compressive strength and porosity of mortars were investigated. Microstructure and morphology of pastes were characterized using scanning electron microscope and X-ray diffraction (XRD), respectively. Moreover, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectrometer (FTIR) were also used to determine the hydration reaction. The results show that Portland cement paste with additional ZnO was found to slightly increase the water requirement while the setting time presented prolongation period than the control mix. However, compressive strength of ZnO mixes was found to be higher than that of PC mix up to 15% (at 28days) via filler effect. Microstructure, XRD and TGA results of ZnO pastes show less hydration products before 28days but similar at 28days. In addition, FTIR results confirmed the retardation when ZnO was partially added in Portland cement pastes.

Biomineralized cement-based materials: Impact of inoculating vegetative bacterial cells on hydration and strength

Biomineralization in cement-based materials has become a point of interest in recent years due to the possibility that such an approach could be used to develop a self-healing cement-based system. The objective of this study was to investigate the impact of vegetative cells of Sporosarcina pasteurii on the hydration kinetics and compressive strength of cement-based materials. The hydration kinetics were greatly influenced when a bacterial solution consisting of urea-yeast extract nutrient medium and vegetative cells was used to prepare bacterial cement pastes; specifically, severe retardation was observed. In addition, an increase in calcium carbonate precipitation, particularly calcite, occurred within the bacterial pastes. Furthermore, after the first day of hydration, the bacterial mortar displayed compressive strength that was similar to or greater than the compressive strength of the neat mortar.

A New Method for Predicting Compressive Strength of Cement-Based Materials

As a porous medium, the strength of cement-based materials is significantly affected by its porosity. This paper presents a new method to describe the strength development of cement-based materials as a function of porosity based on a developed microstructure hydration model of cement. The hydration model deduces the relationship between the diameter change of cement particle and time based on Krstulović-Dabić hydration kinetics formulas and extends a broader version by considering the effect of water reduction, temperature variation, interfacial contact area between hydration products and free water on the hydration rate. Using the hydration model, the time-varying development of porosity can be obtained. Then, based on the strength model proposed by Maekawa et al, in which both the present and initial porosity are taken into account, a new method was established to predict the strength evolution with the porosity calculated by the hydration model.

A neural network approach for compressive strength prediction in cement-based materials through the study of pressure-stimulated electrical signals

This paper presents a non-destructive method for predicting the compressive strength of cement-based materials by studying the appearance of weak electrical signals at specimens that are under mechanical stress. A series of lab experiments have been conducted in order to record the pressure-stimulated electrical signals in cement mortar specimens. Selected signal characteristics were correlated with the ultimate compressive strength of each specimen through the use of a neural network, employing a special training algorithm that offers increased predictive abilities. Results showed that the ultimate compressive strength can be successfully predicted without destroying the specimen.

Quasi-static compressive strength of cement-based materials

Wet cementitious materials show a noticeable dependence on the rate of quasi-static loading. While dry cementitious materials are almost independent of loading rate in the quasi-static region, the mechanical strength of wet materials increases with increasing rate of loading. Therefore, the Abrams' formula for the static mechanical strength cannot provide reliable values with wet materials at higher rates and should be corrected. Some possibilities for its improvement have been discussed.

Metakaolin, a solution for the precast industry to limit the clinker content in concrete: Mechanical aspects

The current trend to decrease the clinker content in cements through the use of mineral additions in order to limit CO 2 emissions into the atmosphere is of major concern for the precast industry as the resulting binders are generally not very reactive at early ages. Here, composed cements (clinker + slag) or combinations between clinker and mineral admixtures are studied with a view to investigating the compressive strength of cement-based materials at both early (1 day) and later (28 days) ages under steam curing conditions. Limestone and siliceous fillers, silica fume and four metakaolins differing in their production process and impurity content were investigated. Considering performance, economic and environmental criteria, results in the laboratory showed that metakaolin (MK) is a very promising solution at a clinker replacement rate of 12.5–25% by mass. Compressive strength was significantly increased (1-day age) or practically the same as for reference mortars incorporating cement only (28-day age). Thus, in comparison with a reference concrete containing no MK and for an identical granular skeleton, the combination clinker/MK was validated in the precast factory in full-scale trials for slip-forming (25% replacement) and self-compacting (17.5% replacement) concrete applications: compressive strength and porosity were not affected.