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A sophisticated characterisation of a porous material structure has been challenging in material science. Three-dimensional (3D) structure analysis allows the evaluation of a material's homogeneity, pore size distribution and pore wall properties. Micro-computed tomography (micro-CT) offers a non-destructive test method for material evaluation. This paper characterises a novel ternary binder's porous structure using micro-CT. Gypsum–cement–pozzolan (GCP) ternary binders are low-carbon footprint binders. Both natural and industrial gypsum were evaluated as a major components of GCP binders. Porous GCP binder was obtained by a foaming admixture, and the bulk density of the material characterised ranged from 387 to 700 kg/m3. Micro-CT results indicate that pores in the range from 0.017 to 3.0 mm can be effectively detected and described for porous GCP binders. The GCP binder structure proved to be dominant by 0.1 to 0.2 mm micropores. For GCP binders produced with natural gypsum, macropores from 2.2 to 2.9 mm are formed, while GCP binders with phosphogypsum possess pores from 0.2 to 0.6 mm. Micro-CT proved to be an effective instrument for characterising the homogeneity and hierarchical pore structure of porous ternary binders. [ABSTRACT FROM AUTHOR]

Background: "Obesity paradox" occurs in type 2 diabetes mellitus (T2DM) patients when body mass index (BMI) is applied to define obesity. We examined the association of visceral fat area (VFA) as an obesity measurement with arterial stiffness in seven ideal cardiovascular health metrics (ICVHMs). Methods: A total of 29 048 patients were included in the analysis from June 2017 to April 2021 in 10 sites of National Metabolic Management Centers. ICVHMs were modified from the recommendations of the American Heart Association. Brachial‐ankle pulse wave velocity (BaPWV) ≥ 1400 cm/s was employed to evaluate increased arterial stiffness. Multivariate regression models were used to compare the different effects of BMI and VFA on arterial stiffness. Results: Lower VFA was more strongly associated with low BaPWV than lower BMI when other ICVHMs were included (adjusted odds ratio [OR], 0.85 [95% confidence interval [CI], 0.80–0.90] vs OR 1.08 [95% CI, 1.00–1.17]). Multivariable‐adjusted ORs for arterial stiffness were highest in patients with the VAT area VFA in the range of 150‐200 cm2 (adjusted OR, 1.26 [95% CI 1.12–1.41]). Compared with participants with VAT VFA < 100 cm2, among participants with higher VAT VFA, the OR for arterial stiffness decreased gradually from 1.89 (95% CI, 1.73–2.07) in patients who had ≤1 ICVHM to 0.39 (95% CI, 0.25–0.62) in patients who had ≥5 ICVHMs. Conclusion: In patients with T2DM, using VAT for anthropometric measures of obesity, VFA was more relevant to cardiovascular risk than BMI in the seven ICVHMs. For anthropometric measures of obesity in the ICVHMs to describe cardiovascular risk VFA would be more optimal than BMI. [ABSTRACT FROM AUTHOR]

Navigation line extraction is critical for precision agriculture and automatic navigation. A novel method for extracting navigation lines based on machine vision is proposed herein using a straight line detected based on a high-ridge crop row. Aiming at the low-level automation of machines in field environments of a high-ridge cultivation mode for broad-leaved plants, a navigation line extraction method suitable for multiple periods and with high timeliness is designed. The method comprises four sequentially linked phases: image segmentation, feature point extraction, navigation line calculation, and dynamic segmentation horizontal strip number feedback. The a* component of the CIE-Lab colour space is extracted to preliminarily extract the crop row features. The OTSU algorithm is combined with morphological processing to completely separate the crop rows and backgrounds. The crop row feature points are extracted using an improved isometric segmented vertical projection method. While calculating the navigation lines, an adaptive clustering method is used to cluster the adjacent feature points. A dynamic segmentation point clustering method is used to determine the final clustering feature point sets, and the feature point sets are optimised using lateral distance and point line distance methods. In the optimisation process, a linear regression method based on the Huber loss function is used to fit the optimised feature point set to obtain the crop row centreline, and the navigation line is calculated according to the two crop lines. Finally, before entering the next frame processing process, a feedback mechanism to calculate a number of horizontal strips for the next frame is introduced to improve the ability of the algorithm to adapt to multiple periods. The experimental results show that the proposed method can meet the efficiency requirements for visual navigation. The average time for the image processing of four samples is 38.53 ms. Compared with the least squares method, the proposed method can adapt to a longer growth period of crops. [ABSTRACT FROM AUTHOR]

In this paper, the rheological parameters of alkaline activated cement (AAC) paste tailored for continuous extrusion using the non-traditional test method of the direct shear box test are presented. Characteristic changes of the material’s rheological behaviour are estimated in response to variations in the water-to-solid ratio and addition of a cellulosic rheology aid. The results indicate that the increase of the water-to-solid ratio from 0.18 to 0.19 does not impact the internal angle of friction (φ) but does, however, reduce the shear yield strength, or cohesion (c), by 85%. For mixes containing cellulosic rheology aid, the internal angle of friction shows no significant change also. However, the shear yield strength for the mix with a water-to-solid ratio of 0.18 is 51% higher. The shear yield strength increases by a further 28% for the mix with a water-to-solid ratio of 0.19. These results indicate that the cellulosic rheology aid does not necessarily increase the "flow-like" characteristics of the mix which provides it plasticity and the ability to move through the extruder. It does however significantly improve its ‘green strength’, even at an increased water-to-solid ratio of 0.19, which would ultimately assist with lowering the binder density.

In this paper, first, the technical aspects for applications of finite-element method (FEM) in modeling material forming processes are reviewed, with a final determination of employing the solid formulation explicit finite element code, ANSYS/LS-DYNA, with the arbitrary Lagrangian--Eulerian mesh to simulate upsetting process, which is the uniaxial compression of a cylindrical specimen between two flat platens, of the fresh fiber-cement paste. After combining a previously proposed elasto-viscoplastic constitutive model for the fresh fiber-cement paste into the numerical procedure, satisfactory agreement between experimental and simulated results is observed for the upsetting force-imposed displacement data. The evolution of the deformation within the material flow in the upsetting process is then interpreted based on the calculated results. The study indicates that the present finite-element procedure, as well as the material constitutive model and the boundary condition treatment, are appropriate for modeling the upsetting process of the fresh fiber-cement paste. DOI: 10.1061/(ASCE)0733-9399(2007)133:11(1192) CE Database subject headings: Simulation; Fiber reinforced materials; Cements; Finite element method; Strain rate.

Upsetting tests were conducted on cylindrical specimens made of a typical fresh short fiber-reinforced cementitious composite (SFRCC) paste for extrusion at various boundary conditions to derive the paste's constitutive behavior. Due to friction present at the specimen and the equipment platens interfaces, stress was not uniformly distributed in the specimen and had to be corrected. In this study, two analytical methods were utilized to derive the true flow stress of the fresh SFRCC paste through correcting the nominal yield stress obtained from the upsetting test. One of them was the stress extrapolation method, which required a large number of experimental data and predetermined boundary friction, lt was found that the results corrected by this method from experiments at the lubricated boundary were more reliable than those at the dry boundary and this method could also give an approximate estimation of the boundary friction coefficient. As comparison, the flow stress correction method required only a small amount of experimental data and no predetermined boundary friction. It was found that this method provided better results at the dry boundary than at the lubricated boundary. The fresh SFRCC paste exhibited both strain and strain rate hardening characteristics whereas strain rate hardening effect was more significant and dominated. DOI: 10.1061/(ASCE)0733-9399(2006)132:2(149) CE Database subject headings: Cementation; Strain rate; Fiber reinforced materials; Boundaries; Composite materials.

Geopolymer composites reinforced with short polyvinyl alcohol (PVA) fibers have been manufactured using the extrusion technique. The extruded products were thin plates with 6 mm thickness. It was demonstrated that short fiber reinforced geopolymer composites (SFRGCs) could be extruded without additional theological modifier. Bending tests have been conducted with the extruded samples to investigate their mechanical properties. The fiber failure patterns in SFRGCs with various formulations were examined by scanning electron microscope and energy dispersive x-ray analysis techniques. The experimental results showed that the addition of PVA fiber could largely increase the ductility of SFRGCs, resulting in fiber failure modes changing from brittle to ductile. The effects of varying the amount of fly ash on the flexural behavior of various SFRGCs were also investigated. The SFRGCs incorporating small percentage of fly asia showed higher flexural strengths but smaller detections, while the SFRGCs incorporating a large percentage of fly ash had lower flexural strengths, but larger deflections. This could be attributed to the change of the bonding between fiber and matrix that led the change of failure mode from fiber fracture to fiber pullout. CE Database subject headings: Fiber reinforced polymers; Composite materials; Fly asia; Failure modes.

Accelerated durability assessment is one of the promising ways to provide a sound basis for service life prediction of concrete. To follow the rapid pace of research in modern concrete technology, an effective accelerated assessment system for concrete durability with automatic control and consistent working performance is highly desired. In this paper, the general concepts and ways of implementing computerized feedback control of a multipurpose accelerated concrete durability test system are first presented and applied to frost-resistant (one of the main durability factors of concrete structures in cold regions) assessment of different concretes. The experimental investigations showed that the newly developed automatic feedback controlled system was reliable and had a promising future for the accelerated durability assessment of concretes. Second, based on the premise that the deterioration mechanisms and the surrounding aggressive environment of the concrete under consideration cannot be precisely described by classical logic, it is believed that durability assessment of concrete is indeed a decision-making process and belongs to the fuzzy logic field. Following this line of thought, a general framework of synthetic concrete durability evaluation was developed by combining the principles of various individual accelerated durability tests, such as frost resistance, water permeability, crack width, and carbonation penetration and concepts of fuzzy logic. The working examples showed that the fuzzy synthetic evaluation developed agreed well with the experimental results for concrete durability investigated. CE Database subject headings: Acceleration; Concrete durability; Feedback control; Freeze-thaw; Permeability; Carbonation; Fuzzy sets; Performance evaluation.

The rheology behavior of fresh short fiber reinforced cementitious composite (SFRCC) for extrusion purpose was investigated through capillary extrusion. It was found that the classical capillary theory for single-phase fluid was not appropriate to interpret the flow behavior of fresh SFRCC due to the large pressure loss occurring at the capillary entrance and the significant slip effect happening in the capillaries. By using a set of capillaries with the same diameter but different lengths, the true shear stress was derived on the basis of Bagley's end correction while the slip effect was calibrated through a series of capillary extrusion tests with different capillary diameters. It was found that the slip velocity could be determined by the Jastrzebski model. Further studies showed that the intrinsic rheology behavior of fresh SFRCC could be modeled by the Herschel-Bulkley equation and the associated parameters could be determined through the experimental and the data interpretation method described in this paper. The fresh SFRCC flow in capillary extrusion was dominated by slip, and the velocity profile could be determined through a superposition of an internal shear flow with a plug flow. The slip layer thickness developed in the capillaries was also estimated based on the calibrated theory and experimental data. DOI: 10.1061/(ASCE)0899-1561(2005)17:1(28) CE Database subject headings: Rheology; Cements; Slip; Fiber reinforced materials.

Short fiber reinforced cement composites with large volumes of perlite have been investigated for their resistance to high temperature exposures. The composites were manufactured by the extrusion technique. The extruded products, thin plates and cylinders, were subjected to different thermal treatments with the maximal exposure temperatures, [T.sub.m], of 200, 300, 450, and 600[degrees]C, and exposure periods, [T.sub.j], of 1 and 10 h. After that, the residual mechanical properties of those extrudates, such as flexural strength, [f.sub.t], compressive strength, [f.sub.c], and modulus of elasticity, E were measured and normalized to the corresponding values obtained from specimens without thermal treatments. The weight loss ratios, [omega], of the composites were also monitored during the thermal treatment process. In addition, the microstructure of these composites was studied using a scanning electron microscope and the pore structure was examined by mercury intrusion porosimetry. It was found that [f.sub.t], [f.sub.c], and E significantly decreased as [T.sub.m], [T.sub.h] , or both increased. The property deterioration could be attributed to fiber melting or softening, dehydration of cement hydrates, and porosity increasing during the heating process. Flexural strength, [f.sub.t], decreased more remarkably than compressive strength, [f.sub.c], and modulus of elasticity, E. The thin sheets reinforced by polyvinyl acetate (PVA) fibers showed more significant reduction in flexural strength than those reinforced by glass fibers due to the much lower melting point of PVA fiber. The composites, incorporating silica sand as aggregates, showed greater degeneration of mechanical properties than those using perlite as aggregates. The improvement of thermal resistance of perlite specimens could be attributed to the greater specific heat, lower thermal conduction coefficient, and the better thermal insulation property of perlite. CE Database subject headings: Fiber reinforced materials; Residual strength; Temperature; Thermal insulation; Microstructure; Porosity; Cements.