This paper describes the steel fiber effect on the crack permeability and crack surface topography of concrete subjected to freeze-thaw damage. The sequential crack permeability of steel fiber ...reinforced concrete are investigated by a vacuum permeability set-up. The topographical analysis is applied on the crack surface by an invented 3-D laser scanning equipment. The results show that the crack permeability of concrete is less than the value predicted by the Poiseuille flow model and their difference decreases gradually with the crack widening. With increment of steel fiber dosage and freeze-thaw damage level, the effect of steel fiber on reducing the crack permeability becomes strong. Topographical analysis illustrates that both steel fiber and freeze-thaw damage enhance the roughness of concrete crack surface. The relationship between roughness number of crack surface and material permeability parameter α follows an exponential function, which can be employed to quickly estimate the crack permeability of concrete.
•Steel fiber and freeze-thaw damage enhance the roughness of concrete crack surface and reduce the crack permeability.•The difference between crack permeability of concrete and Poiseuille flow model decreases with crack widening.•The vacuum permeability set-up are successfully applied to evaluate the sequential crack permeability.•The relationship between roughness of crack surface and crack permeability is suggested for durability evaluation of SFRC.
•Crack self-sensing ability of concrete beam added with SF, CB and CF is studied.•Two models for FCI-COD curve are found for deflection softening/hardening beam.•Signal noise of FCI-COD curves has ...been analyzed by the fractal geometry method.•Hybrid use of CB and SF is an optimization option for crack self sensing concrete.
This work explores the mechanical and self monitoring performance of concrete beams containing steel fiber (SF), carbon black (CB) and carbon fiber (CF), when subjected to bending. The effect of the utilization of multiphase conductive materials on the compressive strength of the concrete and the load - deflection - fractional change in impedance (FCI) relationship of the concrete beam are investigated. The relationships between FCI and crack opening displacement (COD) and sensitivity (gauge factor) are also studied. Moreover, the quantitative analysis of signal noise in FCI-COD curves has been accomplished by the fractal geometry method. The result shows that a monotonic linearity and bi-linearity increasing relationship between FCI and COD can be observed for beams with deflection-softening (Group A and Group B specimens) and deflection-hardening (Group C specimens) behavior, respectively. The diphasic conductive admixture (SF + CB) improves the FCI-COD curve with higher sensitivity and lower noise signal compared to the monophasic conductive admixture (SF) and the triphasic conductive admixture (SF + CB + CF) specimen.
Based on the investigation of the influence of steel fibre on the workability of fresh self-consolidating concrete (SCC), this paper presents the experimental results carried out on a series of ...simply supported SCC rectangular beams, using steel fiber reinforcement with and without stirrups, and subjected to four-point symmetrically placed vertical loads. The major test variables are the steel fibre content and stirrup ratios. The current study on the shear strength of conventional reinforced concrete (RC) beams verifies the shear strength of SCC beams with steel fibres. The investigation indicates that the shear strength significantly increases by increasing the fibre content; the addition of steel fibres in an adequate percentage can change the failure mode from a brittle shear collapse into a ductile flexural mechanism. The stirrups can be partially replaced by steel fibres. The combination of steel fibres and stirrups demonstrates a positive composite effect on the mechanical behaviour. The shear strength recorded experimentally is compared with the value obtained from the proposed formula, and the correlation is satisfactory.
•Pore pressure of FRSCC during fire was investigated.•Influence of different fibers on the change of pore pressure was analyzed.•An empirical formula was proposed to predict the relative maximum pore ...pressure of FRSCC exposed to fire.
The focus of this paper is given to investigate the effect of different fibers on the pore pressure of fiber reinforced self-consolidating concrete under fire. The investigation on the pore pressure-time and temperature relationships at different depths of fiber reinforced self-consolidating concrete beams was carried out. The results indicated that micro PP fiber is more effective in mitigating the pore pressure than macro PP fiber and steel fiber. The composed use of steel fiber, micro PP fiber and macro PP fiber showed clear positive hybrid effect on the pore pressure reduction near the beam bottom subjected to fire. Compared to the effect of macro PP fiber with high dosages, the effect of micro PP fiber with low fiber contents on the pore pressure reduction is much stronger. The significant factor for reduction of pore pressure depends mainly on the number of PP fibers and not only on the fiber content. An empirical formula was proposed to predict the relative maximum pore pressure of fiber reinforced self-consolidating concrete exposed to fire by considering the moisture content, compressive strength and various fibers. The suggested model corresponds well with the experimental results of other research and tends to prove that the micro PP fiber can be the vital component for reduction in pore pressure, temperature as well spalling of concrete.
•A new model for shear strength prediction of SFRC was proposed.•Fiber contribution was introduced by a theoretical method.•The predicted shear strength is in good agreement with the test ...results.•The proposed model can reflect the studied parameters well.
This study proposes a theoretical approach based on modified compression field theory to predict the shear strength of steel fiber-reinforced concrete (SFRC) beams without stirrups. The tensile contribution of the steel fibers is considered in the tensile stress–strain constitutive equations, which take into account the distribution of the fibers. The proposed strength model is verified by comparing it with 139 shear failure tests previously conducted on SFRC and reinforced concrete beams without stirrups. The influences of concrete strength, fiber volume, shear span-to-depth ratio, and longitudinal steel ratio on predicted shear strength are also discussed. Comparisons between the predicted and experimental results show that the proposed model can estimate shear strength accurately.
The civil engineering sector accounts for a significant percentage of global material and energy consumption and is a major contributor of waste material. The ability to recycle and reuse concrete ...and demolition waste is critical to reducing environmental impacts in meeting national, regional and global environmental targets. Handbook of recycled concrete and demolition waste summarises key recent research in achieving these goals.Part one considers techniques for managing construction and demolition waste, including waste management plans, ways of estimating levels of waste, the types and optimal location of waste recycling plants and the economics of managing construction and demolition waste. Part two reviews key steps in handling construction and demolition waste. It begins with a comparison between conventional demolition and construction techniques before going on to discuss the preparation, refinement and quality control of concrete aggregates produced from waste. It concludes by assessing the mechanical properties, strength and durability of concrete made using recycled aggregates. Part three includes examples of the use of recycled aggregates in applications such as roads, pavements, high- performance concrete and alkali-activated or geopolymer cements. Finally, the book discusses environmental and safety issues such as the removal of gypsum, asbestos and alkali-silica reaction (ASR) concrete, as well as life-cycle analysis of concrete with recycled aggregates.Handbook of recycled concrete and demolition waste is a standard reference for all those involved in the civil engineering sector, as well as academic researchers in the field. * Summarises key recent research in recycling and reusing concrete and demolition waste to reduce environmental impacts and meet national, regional and global environmental targets * Considers techniques for managing construction and demolition waste, including waste management plans, ways of estimating levels of waste, the types and optimal location of waste recycling plants * Reviews key steps in handling construction and demolition waste
In this paper, a newly developed method of evaluating the shear toughness of fiber reinforced RC beams in terms of its post-peak nominal average equivalent shear strength was investigated. This ...method is simple and the advantages are significant.
Based on the investigation on the workability of hybrid fiber reinforced self-compacting concrete (HFRSCC), this paper analyzed the influence of various fiber types, including steel macro-fiber and hybrid fiber (macro-steel fiber+macro plastic fiber) on the shear strength and shear toughness of RC beams. The major test variables are the fiber contents, fiber types and stirrup ratios. The effects of stirrups and hybrid fibers on improving of beam toughness by the novel method are compared. The results indicate that hybrid fibers can evidently enhance both the shear toughness and the ultimate shear bearing capacity.
Numerous investigations have been conducted on self-compacting concrete (SCC) and lightweight aggregate concrete (LWAC), but there are relatively very few studies on self-compacting lightweight ...concrete (SCLC). This paper deals mainly with the mix proportion design for SCLC and its workability. By considering the water absorption of lightweight aggregate (LWA), two mix proportions for SCLC are designed by the overall calculation method with fixed fine and coarse aggregate contents. The workability of the two types of fresh SCLCs is quantitatively evaluated by the slump flow, V-funnel, L-box, U-box, wet sieve segregation, and surface settlement tests. The uniformity of distribution of LWAs along the specimen is also evaluated by the column segregation test and the cross-section images. Based on the experimental results, a detailed analysis is conducted. It is found that the two types of fresh SCLCs have good fluidity, deformability, filling ability, uniform aggregate distribution and minimum resistance to segregation. It can be concluded that the two mix proportions for SCLC presented in this paper satisfy various requirements for workability and can be used for the design of practical concrete structures.
Despite the well-established findings of a higher incidence of retina-related eye diseases in patients with diabetes, there is less investigation into the causal relationship between diabetes and ...non-retinal eye conditions, such as age-related cataracts and glaucoma.
We performed Mendelian randomization (MR) analysis to examine the causal relationship between type 2 diabetes mellitus (T2DM) and 111 ocular diseases. We employed a set of 184 single nucleotide polymorphisms (SNPs) that reached genome-wide significance as instrumental variables (IVs). The primary analysis utilized the inverse variance-weighted (IVW) method, with MR-Egger and weighted median (WM) methods serving as supplementary analyses.
The results revealed suggestive positive causal relationships between T2DM and various ocular conditions, including "Senile cataract" (OR= 1.07; 95% CI: 1.03, 1.11;
=7.77×10
), "Glaucoma" (OR= 1.08; 95% CI: 1.02, 1.13;
=4.81×10
), and "Disorders of optic nerve and visual pathways" (OR= 1.10; 95% CI: 0.99, 1.23;
=7.01×10
).
Our evidence supports a causal relationship between T2DM and specific ocular disorders. This provides a basis for further research on the importance of T2DM management and prevention strategies in maintaining ocular health.
The antimicrobial peptide LRGG (LLRLLRRGGRRLLRLL-NH2) was designed and chemically synthesized in a study conducted by Jia et al. Gram-negative bacteria were found to be sensitive to LRGG and ...exhibited a high therapeutic index. Genetic engineering methods were used to create the prokaryotic fusion expression vector pQE-GFP-LRGG, and the resulting corresponding fusion protein GFP-LRGG was subsequently expressed and purified. The precursor GFP was then removed by TEV proteolysis, and pure LRGG was obtained after another round of purification and endotoxin removal. The prokaryotic-expressed antimicrobial peptide LRGG displays a broad-spectrum antibacterial effect on Gram-negative bacteria, and its minimum inhibitory activity (MIC) against Escherichia coli can reach 2 μg/mL. Compared to the chemically synthesized LRGG, the prokaryotic-expressed LRGG exhibits similar temperature, pH, salt ion, serum stability, and cell selectivity. Furthermore, prokaryotic-expressed LRGG showed excellent therapeutic effects in both the infection model of cell selectivity and no embryotoxicity in a Galleria mellonella infection model. The mechanism by which LRGG causes bacterial death was found to be the disruption of the Gram-negative cell membrane.
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