Seawater sea-sand cement matrix [SSCM] is an abundant, cost-effective material with favorable mechanical properties, making it a promising eco-friendly building material. In this study, modified SSCM is prepared by incorporating superabsorbent polymers [SAP]. The durability characteristics, including drying shrinkage, impermeability, and freeze-thaw resistance, are systematically investigated. Additionally, the underlying mechanisms and micro-structural characteristics of SSCM are examined through hydration degree analysis and scanning electron microscopy [SEM]. The experimental results indicate that the incorporation of SAP can significantly improve the anti-drying shrinkage behavior and anti-freeze-thaw of SSCM. When the SAP content reaches 1.0 %, the drying shrinkage is reduced by 18.0 %. Meanwhile, when the SAP content is 0.5 %, the modified SSCM exhibits the strongest impermeability, reaching 4.95 MPa an increase of 86.8 % compared to the control SSCM. In addition, the hydration degree and SEM analysis indicates that the incorporation of SAP enhances cement hydration of SSCM, with a 1.0 % SAP dosage increasing the 14-day hydration degree by 7.3 % compared to the control SSCM. Additionally, higher SAP content promotes the formation of C-S-H and AFt hydration products.
As an indispensable component of ceramsite concrete [CC], the particle size of coarse aggregate affects the performance of concrete to a certain extent. To further investigate the effect of particle size of ceramsite on mechanical properties and freeze-thaw resistance of CC simultaneously, seven series of CC containing ceramsite with various particle sizes were designed based on three different particle sizes of coarse aggregate which were 5 similar to 6 mm, 10 similar to 11 mm and 15 similar to 16 mm respectively. The results showed that the compressive strength of CC at 28 days increased with the decrease in the average particle size. When the ceramsite with different particle sizes was incorporated, the compressive strength of CC increased faster in the early and middle curing stages. The splitting tensile strength and flexural strength of CC at 28 days also exhibited the same change trend as that in the compression test. However, incorporating ceramsite with large particle size could improve the freeze-thaw resistance of CC. After 100 freeze-thaw cycles, the mass loss rate of CC containing ceramsite with a particle size of 5 similar to 6 mm was 3.7 %, whereas that of 15 similar to 16 mm was only 2.1 % which was the lowest. Meanwhile, the former's relative dynamic elastic modulus [RDEM] was 62.8 %, reaching the minimum value. By comparing the scanning electron microscopy images, the cracks of cement paste and interfacial transition zone [ITZ] of CC containing ceramsite with smaller particle size were wider after freeze-thaw cycles.
Ensuring the long-term integrity - particularly zonal isolation and durability - of CO2 injection wells constitutes a major scientific and technological challenge, as it is essential for preventing undesirable gas migration from the wellbore into overlying formations or to the surface. The integrity of wells designed for CO2 injection depends, among other factors, on well depth, temperature and pressure conditions, injection rate and the composition of the injected CO2, as well as on the applied casing and cementing technologies and the type of sealing cement slurries used. Equally important are the quality and composition of the slurries, their rheological and technological properties, as well as their mechanical, phase, and microstructural characteristics, including permeability and porosity. This paper presents the results of laboratory-scale experimental investigations on the incorporation of highly concentrated graphene oxide into ordinary Portland cement-based slurries. The hardened cement slurries were examined over a nine-year period. The results indicate that graphene oxide-modified cement slurries exhibit two mechanisms that enhance their durability and performance. These improvements result from the combined effect of reduced microporosity and enhanced mechanical resistance associated with a decrease in the content and dispersion of the weakest hydration product - portlandite within the C-S-H matrix. To the best of the authors' knowledge, this study provides the first assessment of the microstructural properties of cement slurries containing graphene oxide subjected to long-term curing over a period of nine years.
This paper discusses the possibility of replacing fine aggregates in high performance concrete [HPC] with waste material from CETRIS boards production [WCM]. CETRIS boards are made from a combination of fine wood chips and cement mortar, and a large amount of waste material is generated during their production - cutting and grinding of the boards. In this research, fine waste material from CETRIS boards was used as a potential replacement for fine aggregate in concrete. The high-performance concretes were designed with a maximum size of aggregates of 8 mm, water to binder ratio of 0.25 and 28-days compressive strength around 140 MPa. These types of concrete do not contain enough water for hydration of the cement, so an internal curing process carried out by pre-wetting aggregates can improve this situation. Influence of WCM substitution on workability, bending and compressive strength and modulus of elasticity of concrete are discussed in this paper. The frost resistance of concretes is discussed as well.
The efficacy of cementitious grouts in micro-crack remediation is contingent on a delicate balance of rheological, mechanical, and volumetric properties. This study critically investigates the multifunctional role of nano-CaCO3 [n-CC] in a high-volume fly ash [HVFA] [29 % by binder weight] cementitious system. By systematically varying n-CC dosage from 0% to 4.88 %, we quantify the complex performance trade-offs inherent to nano-modification. Microstructural analyses, including scanning electron microscopy, reveal that n-CC acts as a nucleation catalyst, accelerating hydration and densifying the calcium-silicate-hydrate [C-S-H] gel structure. While this mechanism enhances mechanical performance - culminating in a 19 % increase in 28-day compressive strength at 2.23 % n-CC - it concurrently impairs workability and volumetric stability. Grout fluidity diminished with n-CC content above 0.20 %, and drying shrinkage increased by up to 108.5 %, a consequence of pore structure refinement explained by the Kelvin-Laplace principle. Critically, the optimal dosage for strength [2.23 %] did not align with that for toughness, where the flexural-to-compressive [F/C] strength ratio was maximized at a 1.33% dosage. Through a multi-criteria performance analysis, we identify a 1.33 % n-CC dosage as the optimal content, offering a superior balance of enhanced toughness and manageable shrinkage. This work elucidates the intrinsic performance conflicts in nano-modified, HVFA systems and provides a mechanism-driven framework for designing high-performance grouting materials for precision engineering applications.
Graphene Oxide [GO] has emerged as a promising nano-additive for enhancing the properties of cement-based materials. In this paper, five plastering mortar formulations with varying GO dosages [0 %o, 2 %o, 4 %o, 6%o, and 8 %o of the mass of Portland cement] were prepared to investigate the effects of GO on mechanical performance, durability, and microstructural evolution. The results indicate that, although GO contributes only a limited improvement to compressive strength, it significantly enhances bond strength by up to 200 % under diverse curing conditions. Moderate GO dosages [e.g., 4 %o] also improve water retention and abrasion resistance, while higher dosages disrupt the internal microstructure, leading to reduced performance. GO incorporation increases the proportion of <= 30 nm pores and improves thermal stability. Additionally, a preferential formation of calcium silicate hydrate at the expense of calcium hydroxide, yielding a denser microstructure. These findings highlight the importance of dosage optimization in leveraging GO's potential to enhance key performance attributes of plastering mortars, providing insights forthe development of high-performance cementitious coatings in construction applications.
Accurately predicting the compressive strength of concrete is crucial for quality control and structural safety assessment in civil engineering. However, traditional machine learning methods often struggle to capture the complex nonlinear interactions and strong feature correlations inherent in concrete mix design, thereby limiting their predictive accuracy and generalization ability. To address these challenges, this study proposes a deep learning model [AM-ResNet] that combines attention mechanisms with residual networks. The residual architecture effectively mitigates the vanishing gradient problem in deep networks, while the attention mechanism enhances the ability to identify key influencing factors by dynamically assigning feature weights. The experiments utilized a standard concrete compressive strength dataset from the UCI Machine Learning Repository, which contains 1,030 samples and 8 input variables. The study conducted a comprehensive, multidimensional comparative analysis of Support Vector Regression [SVR], Random Forest, and Backpropagation Neural Network models. The proposed AM-ResNet model achieved a coefficient of determination [R2] of 0.790, a root mean square error [RMSE] of 3.21 MPa, and a root mean square percentage error [RMSPE] of 8.9 %. Over 92 % of the prediction errors fell within the +/- 10 MPa range, meeting typical engineering quality control standards. Under 20 % input noise, AM-ResNet still maintains an R-2 value of 0.674, with a performance decline of only 14.7 %, significantly outperforming baseline models. Using only 10 % of the training samples, its R-2 value reaches 0.621, demonstrating exceptional data efficiency. Five-fold cross-validation confirmed its stability and demonstrated the lowest variance [sigma = 0.021]. The proposed AM-ResNet framework provides a robust, accurate, and interpretable solution for concrete strength prediction, holding great potential for applications in intelligent quality control and material design within the civil engineering field.
This study examines the impact of replacing dune sand [DS] with fine recycled concrete aggregate [FRCA] on the properties of self-compacting mortar [SCM] at incorporation rates of 0 %, 25 %, 50 %, 75 %, and 100 %. The methodological approach is based on the mini-cone test [slump-flow] and the measurement of flow time using the V-funnel, complemented by yield stress [tau 0] estimations through the inclined plane test [IP], the Coussot-Roussel model, and the Chateau-Ovarlez [C-O] model. The effect of structural build-up with rest periods of 10, 20, and 30 minutes was also examined. A reference mix containing 1 % superplasticizer and meeting EFNARC criteria was first selected before the progressive substitution of DS by FRCA. The results highlight, on the one hand, a granular densification related to the presence of fines and the broader particle size distribution of FRCA, leading to an increase in dry packing density [Phi] from 0.55 to 0.62 as FRCA content increased from 0 % to 100 %. On the other hand, workability decreased with higher FRCA content; the slump flow diminished, while the V-funnel flow time tended to increase. From a rheological perspective, the yield stress tau 0 increased both with the FRCA content and with rest time. The C-O model, which integrates packing density and aggregate volume fraction, provided estimations close to those of the IP test, while the Roussel-Coussot model proved more sensitive to variations in the spread diameter. Finally, in the hardened state, compressive strength decreased significantly with substitution. Compared to the reference sample [0 % FRCA], losses reached about 9 % at 50 % and 33.8 % at 100 %, with a similar trend observed in flexural strength.
The first cementing interface refers to the interface between the cement sheath and the casing after the cement injection is completed. The bonding strength of the first cementing interface is mainly generated by the interaction between the outer surface of the casing and the cement sheath. This article explores the influence of cement strength on the first interface of cementing by changing the water-cement ratio of the cement slurry system, adding ultra-fine materials, and changing the type of fluid loss control additive. Cement slurry types were selected in the form of progressive experiments, including pure cement slurry systems [L1, L2] under different water-cement ratios, cement slurry systems [L3] based on pure cement systems mixed with nano-silica, and the addition of different types of fluid loss control additives [S2-S4] and cement slurry system [S5] with fluid loss control additives and latex added together. Through the self-developed cementing strength evaluation mold and the microscopic characterization of the cementing interface, the influencing factors of the cementing strength of the first interface of the cement sheath were explored. The results show that increasing the water-cement ratio or adding nano-silica can promote the formation of hydrated calcium silicate [C-S-H], with lower early strength but higher later strength; adding a fluid loss control additive can increase the content of calcium hydroxide crystals [CH], the close packing of CH and without hydration reacting cement particles can provide the first interface cementing strength; the reaction of the latex particles themselves to form a three-dimensional network structure can improve the cementing strength, but it is not suitable for high-temperature environments. This research is of great significance to the summary of cementing-interface cementing laws and the cementing construction process.
In the process of geological carbon sequestration, the CO2 injected into the formation will react with the hollow cement ring orwellbore cement plug, and reduce the sealing performance of the cement body to further destroy the integrity of the wellbore, causing CO2 leakage and seriously affecting the efficiency of CO2 storage. This study aimed to investigate the effect of CO2 on the sealing performance of cement stone in the wellbore under the condition of CO2 geological storage. For this purpose, a reaction transport model of CO2-corroded cement stone was created and calibrated based on laboratory tests. The results show that the corrosion area of cement stone is a layered structure, resulting in anisotropy of sealing performance of cement stone. The permeability of cement stone perpendicular to the corrosion direction increases with the increase of corrosion depth, while the permeability along the parallel corrosion direction first decreases and then increases. After 2000 hours of corrosion, the permeability increase of cement stone perpendicular to the corrosion direction is greater than that parallel to the corrosion direction by 12 %.
The article presents a review of research findings on the properties of concrete intended for radiological shielding in nuclear power plants. New results obtained in recent years within the framework of the international RADCON project are discussed in the context of other publications. The effects of gamma irradiation on hardening mortar and concrete are presented, revealing the temperature-equivalent nature of the radiation. The observed radiation-induced damage in hardened concrete exposed to gamma rays included an acceleration of carbonation under controlled environmental conditions, an increase in the size of calcite crystals and their micromechanical properties, and a loss of stability of the passive layer on reinforcing steel embedded in the concrete. Neutron activation analysis revealed the presence of radioactive isotopes, particularly long-lived 60Co, 152Eu, and 134Cs, in domestic Portland cements and mineral aggregates. Given the significant influence of concrete homogeneity on shielding performance, new experimental-numerical tools for digital microstructure reconstruction and for predicting the temperature field in hardening concrete are discussed. Based on the developed mix designs for heavy self-compacting concrete, the issue of their pressure on formwork is addressed. The new knowledge concerning radiation-induced damage in concrete and the research tools described may be useful for optimizing the composition and technology of concrete in new nuclear energy facilities.
The cementing quality at the wellbore interface is critical to wellbore integrity and long-term safety. In this study, Al2O3 modulates hydration products to enhance interfacial bond strength between cement slurry and casing. The influence of Al2O3 on primary cement interface bonding strength was investigated using characterization techniques including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, backscattered electron microscopy, and mercury intrusion porosimetry. Interfacial bond strengths were tested at varying curing temperatures and durations. Analysis of hydration products, microstructure, and pore distribution in the interfacial transition zone revealed that Al2O3 promotes the formation of calcium aluminosilicate hydrate. These hydrates interlock with other hydration products to form a dense, interwoven packing structure, significantly optimizing the interfacial microtopography. Simultaneously, it effectively filled the primary pores and microcracks in the interfacial transition zone, reducing porosity and refining the pore size distribution. These combined effects enhanced the bonding performance at the cement ring-first interface. The optimal interfacial bond strength was achieved when the alumina content was 1.8 %.
The utilization of concrete in construction has seen a rapid increase due to its widespread use. However, the cement industry's significant contribution to CO2 emissions and cli-mate change has prompted the exploration of alternative materials. Geopolymer concrete has emerged as a promising substitute to Portland cement in the construction industry in the wake of sustainability. In this study, the advantage of incorporating PVAfibers in geopolymer composites in optimum proportions to improve the overall mechanical proper-ties resulting in ductile concrete is being investigated. By systematically varying the PVA fiber dosage from 0 % to 1.5 % in increments of 0.5 %, along with different molarities ranging from 8 to 12 in two Mixes 1:1 and 1:3, several key properties, including compressive strength, tensile strength, flexural strength, and load-deflection curve were evaluated. The experimental results indicated that the addition of fibers had a negligible im-pact on compressive strength. However, a significant improvement was observed in flexural strength, energy absorption and ductility factor. Subsequently, a mix design model for geopolymer composites was developed, considering the influence of PVAfiber dos-age and molarities. The model was validated using a statistical technique called Response Surface Methodology [RSM], ensuring its accuracy and reliability. Overall, the study provides valuable insights into optimizing the dosage of PVAfibers in geopolymer composites, enabling production of sustainable and reinforced bendable concrete.
In this study, the most suitable locations for cement factory are identified by using the Geographical Information System and Multi-Criteria Decision Analysis [MCDM] in the Konya Plain Project [KPP] [Aksaray, Karaman, K & imath;r & imath;kkale, K & imath;r & scedil;ehir, Konya, Nev & scedil;ehir, Nigde, Yozgat] provinces. The physical conditions of the region were determined based on the Environmental Impact Assessment Reports and expert opinions, and the suitable areas were chosen with technical, social, cultural, and economic criteria. In order to determine the most suitable regions, Athree-stage decision-making process and Scoring System has been used for KPP Provinces. Overall, 56 suitable regions were decided among these provinces. The most suitable facility locations were chosen 7th and 6th region of Karaman province, 5th region of K & imath;r & imath;kkale province, 1st and 4th region of Konya Province.
An analysis of current trends in concrete technology has been conducted. The feasibility of integrating digital methods into the "composition-structure-process-properties-functions" system has been established on the basis of fundamental concrete science principles. The discussion focusses on the role of functional-kinetic monitoring of heat evolution data, which serves as a carrier of technological information about the reactivity, directionality, intensity, and completeness of the progression of various thermodynamically substantiated spontaneous hardening reactions. The efficacy of using calorimetric data to evaluate the interaction parameters of functionally integrated components during the design of concrete compositions and the operational control of hardening regimes has been confirmed. In addition, the effectiveness of the suggested functional-kinetic approach in addressing technological challenges through adaptive [self-adjusting] algorithms for calorimetric monitoring is explored. Methods for digitising calorimetric information, which involves converting analogue thermokinetic and/ortemperature dependencies into a digital format in real time, are also proposed.
Carbon-based nanomaterials, such as carbon nanotubes [CNTs], graphene, and graphene oxide [GO], have been widely investigated for enhancing the properties of cement-based materials. However, their high cost, dispersion challenges, and compatibility issues with cement matrices limit their practical applications. In contrast, carbon dots [CDs], a novel class of carbon-based nanomaterials, offer a promising alternative due to their low cost, non-toxicity, excellent water solubility, and facile synthesis. This study investigates the effects of CDs on the performance of self-leveling mortar [SLM], with a focus on fluidity, mechanical properties: compressive and flexural strengths, shrinkage, and abrasion resistance. CDs were synthesized via a one-step hydrothermal method and incorporated into SLM at varying dosages. The experimental results show that the addition of CDs significantly improves the fluidity and mechanical properties of SLM, with the optimal dosage [3 o/ooo] yielding the highest compressive and flexural strengths. Furthermore, CDs effectively reduce the shrinkage and enhance the abrasion resistance of SLM. Microstructural analysis revealed that CDs promote the formation of calcium silicate hydrate C-S-H gel, leading to a denser and more stable matrix, which contributes to improved mechanical performance and durability. Overall, this study highlights that CDs are a cost-effective and sustainable additive for enhancing the performance of cement-based materials, offering a viable alternative to more expensive nanomaterials.
This study presents the results of research on the influence of the water-to-cement ratio [w/c] on the electrical properties of cement composites with expanded graphite [EG]. The analysis was conducted on samples containing 2 % to 6 % EG, with w/c ratios ranging from 0.40 to 0.60. The experimental program included four-point probe resistivity measurements, impedance spectroscopy, as well as evaluation of the thermoelectric and self-heating properties of the composites. The results indicate that increasing the w/c ratio leads to a reduction in the electrical conductivity of the studied composites, regardless of the EG content. Impedance spectra analysis showed that, within the investigated w/c range, the percolation threshold is exceeded in composites containing more than 4 % EG. The higher the EG content, percolation threshold is exceeded at higher w/c. An important observation is weakly formed semicircles in Nyquist plot for composites in the percolation zone. The closer conductivity of the composite is to the percolation threshold, the less distinct the semicircle. This characteristic spectrum shape allows for the determination of the conductive additive content in the percolation zone. Furthermore, the findings confirm that the w/c ratio significantly influences the self-heating properties of the investigated cement composites. In contrast, the w/c ratio does not appear to affect the magnitude of the Seebeck coefficient above the percolation threshold. The obtained results clearly indicate the significant role of water-to-cement ratio shaping the functional properties of these materials.
The size control of 3D printed concrete filament limits application of 3D printed concrete technology. The accuracy of 3D printed concrete will benefit from stability of extrusion flow. Therefore, it is necessary to study the effective factors on extrusion flow. In this paper, the effects from fluidity and mass of loading in material tank on extrusion flow were discussed. The special phenomenon effective on extrusion flow during the printing process was discovered and named as 'collapse' and 'critical loading'. Meanwhile, the liner relationship between fluidity and extrusion flow per unit mass of initial loading in material tank was observed. A feasible method for extrusion flow prediction was proposed based on mathematical results in this study. And some advices were provided according to the experience from this research.
Mining exploitation of cement/concrete components experience sometimes problems caused by tectonic process and water hazards during mining of polyhalite-bearing sulphate rocks. Poly-halite is a hydrated K-Mg-Ca sulphate mineral of high economic significance, including construction materials industry. On the other hand, traditional tectonic analyses for seismic/water events prediction, often emphasize external forces and mining-induced stress relaxation. They rarely arise questions on primary origin such forces. Potential cumulation of stress, resulted from internal geochemical-mineralogical origin of such forces, of large-scale compression/tension and mass-movement are often neglected. A universal, approach here concerns the role of geochemical control of volume-temperature variations combined with post-sedimentary transformation of anhydrite to polyhalite what apparently implicates substantial problems during any mining carried out in anhydrite bodies. Such 100%transformation: a) increase volume of elemental cells by c.a. +137,76 %, b) is exothermic, c) elevates pressure d) results stress, e) implicates deformations: compressive inside and tensile outside, f) forms elevations, g) results chaotic K/Ar ages with millions of years discrepancies, h) may result sesim-tectonic-water-H2S combined hazards and apparent subsidence. Such transformations have critical implications for general view in tectonic forces and formation of deposits, geological documentation and mining of them, particularly in addressing water, stability hazards during resource extraction and environmental issues [subsidence/deformations, earthquakes, water regime/pollution/ salinisation, H2S etc]. The geochemical reactions, accelerated by deep-mine drainage activity, may result in fast [even days/years] geochemically negligible anhydrite-to-polyhalite volume-grow transitions, which however results in seismotectonic-water-and H2S-hazars, especially in anhydrite-dolomite-halite mining systems. They are pivotal in shaping mechanical properties of rocks and their deformations and movement. The study underscores the need for integrated geochemical and structural analyses to better understand these phenomena and mitigate associated risks from exploration to resource extraction [economy, safety, water-brine-subsidence environmental hazards] and geoengineering.
Cementitious composites are prone to microcracks due to shrinkage in the early stage of curing. During service, they develop microcracks due to mechanical loads, temperature cycling and other factors. These microcracks will lead to a decrease in their durability, which is a common problem in the engineering field. To enhance the durability of cementitious composites and enable crack self-healing, this study innovatively proposes a preparation method for cementitious composites using polymer microcapsules, which are synthesized by in-situ polymerization. Under acidic conditions [pH = 2], polymer microcapsules, with a particle size of around 100 μm, uniform morphology, and excellent thermal stability, are synthesized and uniformly integrated into the cement matrix. The performance of the microcapsules and the composite materials is characterized and tested to evaluate the effectiveness of the method. The results show that under specific acidic conditions [pH = 2], the synthesized microcapsules display a uniform spherical shape, with a particle size of approximately 100 μm and strong thermal stability [main decomposition temperature above 200 °C]. Mechanical tests reveal that when the microcapsule content is 2 % [by the mass of cement], the 28-day compressive strength of cementitious specimens reaches 35.24 MPa. After damage, the recovery rate of the specimens reached 103.46 %. Crack healing experiments showed that the initial cracks of the specimens in the study group had a significant healing effect by reducing the crack width by 85% within 16 days under specific maintenance conditions. The study preliminarily confirms that the cementitious composites with microcapsules have good self-healing potential and mechanical properties, providing evidence for the engineering application of self-healing concrete.
