Explore the vast range of titles available.

Cement hydration kinetics, characterized by heat generation in early-age concrete, poses a modeling challenge. This work proposes a physics-informed neural network (PINN) named PINN-CHK designed for cement hydration kinetics, to predict early-age temperature rises in cement paste. PINN-CHK leverages data-driven solutions to craft a high-fidelity prediction model, encompassing material properties and maturity functions in cement hydration. Trained on heated cement paste data, it simultaneously fits experimental results and underlying physics, yielding a mesh-free simulation. Incorporating governing partial differential equations (PDEs), and initial and boundary conditions into its loss function, PINN-CHK architecture undergoes rigorous benchmark testing, demonstrating unparalleled predictive accuracy compared to conventional deep-learning methods. It excels in predicting complete temperature fields during spatial–temporal cement hydration, achieving a remarkable relative L2 error as low as 0.00341. PINN-CHK achieves exceptional convergence and accuracy with only 5% of the training data, ushering in a new era in this crucial field. This innovative approach bridges the gap between theory and practice, offering an attractive alternative to conventional finite element solvers for enhanced comprehension of cement hydration kinetics and concrete maturity and strength development in cement-based materials.

This study employed a full-scale cement sheath quality evaluation apparatus, along with a high-precision distributed fiber optic temperature sensing system, to perform real-time, continuous monitoring of the temperature change throughout the cement hydration process. The results of the cement annulus and cement bond defect monitoring during the hydration process indicated that the distributed fiber optic temperature data enabled centimeter-level resolution in defect identification. Defective regions exhibited significantly reduced temperature fluctuation amplitudes, and an inversion in temperature change at the early hydration stage, detected at the cement–defect boundary, facilitated the early detection of defect locations. The distributed fiber optic system was capable of conducting continuous and comprehensive monitoring of the sequential hydration temperature peaks of cement stages injected into the annulus. The results revealed the interdependence among different cement stages, as well as a phenomenon whereby an elevated annular temperature accelerates the progression of cement hydration. The experimental findings provide a reference for identifying the characteristic signals in distributed fiber optic monitoring of well-cementing operations, thereby establishing a foundation for the optimal and effective use of distributed fiber optics in assessing well-cementing quality.

The growing demand for sustainable building materials, amid escalating costs, has spurred interest in alternative solutions such as wood cement composites. This study explores the feasibility of producing wood cement boards (WCBs) using locally sourced cedar sawdust as a reinforcing agent. Boards with a thickness of 10 mm and a target density of 1200 kg/m3 were manufactured under pressures ranging from 2 to 6 MPa for 24 h. Cedar sawdust, used as raw and untreated material, was incorporated into the mixture as a partial substitute for cement in varying proportions, ranging from 10% to 25% (by weight). The WCBs were cured for 28 days under ambient conditions. Physical properties including density, water absorption (WA), and thickness swelling (TS) were assessed, along with mechanical properties through flexural tests. The results showed that increasing cedar sawdust content decreased both density and mechanical performance while increasing WA and TS. Microstructural analysis (SEM and EDS) revealed significant porosity at higher sawdust contents, while lower contents had better matrix–reinforcement cohesion. Additionally, substantial levels of calcium and silicon were detected on the sawdust surface, indicating stabilized cement hydration products. These findings, supported by thermal (TGA and DSC) and FTIR analyses, clearly demonstrate that cement boards with 10% cedar sawdust exhibit favorable properties for non-structural applications, such as wall and partition cladding.

The discharge of lead-contaminated effluents from industrial activities such as smelting, refining, and petrochemical operations poses a critical environmental challenge by polluting surface and groundwater resources. Among mitigation strategies, the use of cement-based materials for the stabilization and solidification (S/S) of lead contaminants offers a promising approach, integrating environmental management with construction applications. This study systematically investigates the long-term effects of lead-contaminated mixing water on the mechanical performance, durability, and pollutant immobilization capacity of concrete, with particular focus on microstructural evolution. A total of 210 concrete specimens were prepared using mixing water containing lead concentrations of 0, 0.001, 0.002, 0.005, 0.01, 0.02, and 0.05 M. Compressive strength tests were conducted at curing ages ranging from 3 to 730 days, and pollutant retention was assessed using the toxicity characteristic leaching procedure. Microstructural analyses through X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy revealed that lead contamination disrupted cement hydration by forming Pb(OH) 2 and Pb-C-S-H phases, which inhibited the nucleation and growth of primary hydration products, notably calcium silicate hydrate (C-S-H) and portlandite (CH). At 0.05 M lead concentration, a compressive strength reduction of 61% was recorded after 365 days, with further deterioration to 14 MPa after 730 days. Despite the mechanical degradation, the stabilization process significantly reduced lead leaching, maintaining compliance with environmental standards for non-structural applications. These findings highlight the feasibility of employing lead-contaminated water in controlled construction uses, while emphasizing the critical need to account for long-term mechanical performance reductions when designing S/S-based waste management solutions.

This study aims to investigate the influence of CO2-mixing dose (mass fractions of 0.3%, 0.6%, and 0.9%) and prolonged mixing time on the fresh and hardened properties of cement pastes. The CO2-mixing can act as coagulant in fresh cement mixtures, resulting in a significant reduction in workability associated with the formation of a rich calcium carbonate network on the surface of cement particles. The CO2-mixing cement pastes were found to be much stiffer and more difficult to handle, place, and compact than the control mixture, which had a negative effect on the mechanical strength performance of the hardened pastes. However, prolonging the mixing time for 1 min (immediately after CO2-mixing) can effectively improve the workability (by ∼53%–85%) by breaking up the flocculation network of deposited calcium carbonates. As a result, the presence of detached calcium carbonate accelerated early cement hydration and densified the microstructure; this improved early-age compressive strength by ∼6%–32%, depending on the CO2-mixing dose used. Therefore, it seems that the CO2-mixing dose should be controlled at ⩽0.6% with the mixing time prolonged in order to attain satisfactory workability and mechanical strength.

This study investigates the early-age cracking behavior of continuously reinforced concrete beams restrained at their ends. It focuses on casting a 30m-long reinforced beam, utilizing concrete mixes with identical compressive strengths but different cement types. Recent research has overlooked how ambient temperature and internal temperature variations from cement hydration affect crack formation in outdoor environments during the early stages. Consequently, it compares the heat evolution during the early stages for the 30-meter beam against that of a 150mm cube specimen, examining the effects of the two types of cement employed. Test results demonstrate that using sulfate-resisting cement (SRC) results in a more significant occurrence of early-age cracks comparing ordinary Portland cement (OPC), with crack widths 33% to 50% wider for SRC. Additionally, the peak temperature resulting from the cement hydration in the cube specimens was 5 to 6 degrees higher than in the 30 m long beam for both cements. Lastly, Since the fineness of SRC is higher than that of OPC, its compressive strength at 7 days was 8% greater than that of OPC; however, the 28-day strengths were nearly the same.

Does addition of lignocellulosic fibers alter the rate of hydration of fiber-reinforced cementitious composites? This question is being probed in this paper through a series of tests involving thermal analysis, Fourier transform infrared (FTIR) spectra, and X-ray diffraction (XRD) investigations along with standard setting time tests. It could be observed that retardation of hydration rate can be achieved with addition of increasing percentage of fibers (irrespective of the source: jute or ramie). It is also observed that treated jute has more hydration rate retardation capability in comparison to that of treated ramie. The probable reason for this effect is that the amorphous part of cellulose (obtained more in treated jute in comparison to that of treated ramie) attaches to the C[a.sup.2+] ions (thereby decreasing the amount of Ca[(OH).sub.2] released in fiber-reinforced cement paste) in the calcium silicate hydrate (CSH) gel to result in this retardation effect. Keywords: cellulose; hydration rate; jute fiber; lignin; ordinary portland cement hydration; ramie fiber.

This research proposes a new pixel-based model called the hydration-pixel probability model which aims to simplify cement hydration as a probability problem. The hydration capacity of cement, the solution within pores, and the diffusion of solid particles are represented by three probability functions derived from experimental data obtained through electrical resistivity and hydration heat measurements. The principle of the model is relatively simple, and the parameters have clear physical meanings. In this research, the porous structures of different cement pastes with w/c ratios of 0.3, 0.4, and 0.5 are investigated. The results indicate that the porosity of the cement paste decreases during the first few hours, followed by a rapid decline, and eventually reaches a steady state. The porosity of the paste decreases as w/c ratio decreases, and the rate of decrease is more rapid in the early stages. Referring to the porosity curves, the average degree of hydration and depth of hydration can be derived. The simulation results show that the hydration degree of paste composed of irregular particles is higher than that of the paste composed of round particles. The trend in the development of the average hydration depth is similar to that of the average hydration degree. Upon analyzing the average growth rate of the hydration depth, it is observed that there are two peaks in the curves, which correspond to the three characteristic points in the electrical resistivity test.

Calcium silicate hydrate seeding is a promising accelerator for cement hydration. In this work, calcium silicate hydrate nanoparticles with various CaO/SiO2-ratios were prepared by means of mechanochemical approach. X-ray diffractometry, scanning electron microscopy and laser granulometry were used to study the properties of the calcium silicate hydrate particles. The evaluation of the effectiveness of calcium silicate hydrate seeds on the cement hydration was conducted by heat flow calorimetry and compressive strength tests using ordinary Portland cement and early strength white cement. Results show that the main crystalline phase in the final product is crystalline calcium silicate hydrate (Ca1.5SiO3.5·xH2O). An acceleration of 6.08 h or 28.03% on the hydration of P.O 42.5 type Portland cement as well as a 78% increment of compressive strength 24 h after water addition can be achieved using calcium silicate hydrate seeds. Compared to the P.O cement, calcium silicate hydrate nanoparticles are less effective in the P.W white cement, which indicates the nature of the cement is a crucial factor to influence the effectiveness of the calcium silicate hydrate seeds as well.

The temperature difference between the inside and outside of the concrete bridge causes the appearance of early cracks in the concrete bridge. The thermal cracks are appeared on surfaces or inside the bridge body. The sources of the thermal loads come from solar radiation, air temperature, wind speed, and the heat of hydration of cement after pouring concrete (at the early edge of concrete). Concrete T-section used to study the temperature distribution at the early edge, fourteen thermocouples used to measure the temperature during the day; these thermocouples were placed in the different location inside the concrete bridge as well as on its surface. The temperature-time curves were obtained for each thermocouple, from these curves it was found that the effect of cement hydration on the internal temperature was during the first 48 hours, while the effect of solar radiation was evident during daylight hours on the top surface of the model. The effect of solar radiation continues while the effect of cement hydration vanished after 48 hours.