Investigation of the strength and toughness of FRHPC after exposure to high temperature

The investigations on different fibre influences on the compressive strength, the flexural strength and ductility as well as failure pattern of fiber reinforced high-performance concrete (FRHPC) after exposure to various high temperature were carried out. The results indicated that the compressive strength of HPC without fibres declined strongly after high temperature at 900oC, the residual compressive strength was only 10% compared to the original strength. However, both steel fiber (SF) and polypropylene (PP) fiber can reduce the negative effect of high temperature on the strength. The micro PP fiber can mitigate the surface spalling of HPC member significantly, but did not show clear effect on the flexural toughness of concrete matrix. In contrary, the HPC reinforced with macro steel fiber illustrated higher flexural toughness and ultimate load bearing capacity before and after high exposure temperatures. The mechanical properties of HPC reinforced with fibre cocktail (SF + PP) were better than that of HPC reinforced with mono-fibre. Besides, the failure mode of FRHPC beams changed from pull-out of steel fibers at lower temperature to tensile failure of steel fibers at higher temperature (900 oC).Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/22680/2005National Natural Science Foundation of China - Bolsa 5027801

Properties and durability of concrete containing polymeric wastes (tyre rubber and polyethylene terephthalate bottles): an overview

The volume of polymeric wastes like tyre rubber and polyethylene terephthalate bottles (PET) is increasing at a fast rate. An estimated 1000 million tyres reach the end of their useful lives every year and 5000 millions more are expected to be discarded in a regular basis by the year 2030. Up to now a small part is recycled and millions of tyres are just stockpiled, landfilled or buried. As for PET bottles annual consumption represent more than 300,000 million units. The majority is just landfilled. This paper reviews research published on the performance of concrete containing tyre rubber and PET wastes. Furthermore it discusses the effect of waste treatments, the size of waste particles and the waste replacement volume on the fresh and hardened properties of concrete

Experimental investigation on the composite effect of steel rebars and macro fibers on the impact behavior of high performance self-compacting concrete

In this study, the impact behavior of ten types of high performance self-compacting concrete (HPSCC) was explored using the drop-weight method. The HPSCC specimens were reinforced with steel rebars and different fibers for comparison with plain concrete. The reinforcement mechanism of the influences of steel rebars and different fibers on failure impact energy was explained. The composite effects of hybrid use of steel rebars with different fibers on the failure impact energy were also compared. The penetration depth for each mixture was analyzed. Test results showed that the macro fibers could greatly improve the failure impact energy both in plain and reinforcement concrete. Moreover, the toughness, penetration depth, stress redistribution could be improved obviously due to the positive hybrid effect of rebars and macro fibers in reinforced concrete. The statistical analysis technique was introduced to evaluate the experimental data, and the goodness of fit tests showed that the distribution of the blow numbers to the first crack and up to the final failure followed the two-parameter Weibull distribution.The authors gratefully acknowledge the National Natural Science Foundation of China: Grants: 51578109 and 51121005.DUT and Fundação para a Ciência e a Tecnologia(SFRH/BPD/22680/2005).info:eu-repo/semantics/publishedVersio

Possible reusing of household ceramic wastes as mineral admixtures in ecological cement/concrete

Both the Ceramic wastes and the pollution of the cement industry can cause strong damage to the environment and the sustainable development. In the present study, the pozzolanic activity of household ceramic waste powder was investigated by SAI test and Frattini Test; the possibility of the partial substitution of Portland cement blended with ceramic waste powder was analyzed. The results indicate that the compressive strengths of mortar containing ceramic waste at both early age and after 28 days were generally increased as the ceramic waste ratio increased up to at least 15\% replacement, and the ground ceramic waste show clear pozzolanic activity.The authors acknowledge the National Natural Science Foundation of China (Grant: 51578109), and Fundação para a Ciência e a Tecnologia (SFRH/BPD/22680/ 2005).info:eu-repo/semantics/publishedVersio

Effect of macro polypropylene fiber and basalt fiber on impact resistance of basalt fiber‐reinforced polymer‐reinforced concrete

First published: 07 April 2020In this paper, the effect of macro non-metallic fibers (i.e. polypropylene fibers and basalt fibers) on the impact response of basalt FRP-reinforced concrete discs is experimentally investigated using a self-developed drop-weight impact test device. The plain concrete and conventional steel reinforced concrete samples are explored as references. The impact resistance and failure behaviors are analyzed. Statistical analyses for first-crack strength and failure strength are performed. The composite effect of basalt FRP bars and macro non-metallic fibers on the impact energy at failure is also compared. The results indicate that the behaviors under impact load, i.e. failure strength, crack number, the indent diameter and penetration depth of the shriveled area, are greatly improved by adding of macro non-metallic fibers, in particular macro polypropylene fibers. Additionally, the incorporation of these fibers into the basalt FRP-reinforced concrete transforms the brittle failure mode into a well ductile failure mode. Two-parameter Weibull models are fitted by graphical methods and used to characterize the first crack strength and failure strength distributions. Reliability functions for first crack strength and for failure strength are estimated and failure strength can be predicted from first-crack strength by using a linear regress model. The hybrid use of basalt FRP bars and macro non-metallic fibers demonstrates a positive synergetic effect on the impact energy at failure.The authors gratefully acknowledge the National NaturalScience Foundation of China (Grant: 51578109), the Por-tuguese Funds through FCT, within the Project UID/MAT/ 00013/2013

Experimental study and prediction model for flexural: behavior of reinforced SCC beam containing steel fibers

Seven full-scale steel fiber reinforced self-consolidating concrete (SFRSCC) beams were tested to study the effects of macro steel fibers on the flexural behavior of reinforced self-consolidating concrete beams. The major test variables are fiber contents and longitudinal reinforcement ratios. The ultimate load, midspan deflections, steel reinforcement strains, crack width and crack spacing were investigated. The enhanced ultimate flexural capacity and reduced midspan deflection due to the addition of steel fibers were observed. With the increasing of fiber contents, the strain in longitudinal reinforcement, crack width and crack spacing decreased significantly. The possibility of using steel fibers for partial replacement of the conventional longitudinal reinforcement is estimated, which is meaningful for extending the structural application of SFRSCC. A method incorporating fiber contribution to the post-cracking tensile strength of concrete in the flexural analysis of SFRSCC beam is also suggested. Comparisons are made between the suggested model and the fib Model Code 2010 model with experimental data. The results showed that the suggested model can estimate ultimate flexural capacity accurately.National Natural Science Foundation of China: Grants: 51078058 and 51121005

Topographical analysis of fractured surface roughness of macro fiber reinforced concrete and its correlation with flexural toughness

Macro fibers reinforcement is considered to be an effective way to improve the flexural toughness of the concrete. With growing public interest in the wide-spread use of fiber reinforced concrete (FRC), the need for understanding and evaluating micro fiber reinforcement mechanism is on the rise. In this study, concretes were reinforced by various dopant amounts of macro polypropylene (PP) fiber or steel fiber (SF) or their mixtures, topographical analysis was applied on a fractured concrete surface by using a custom-built 3-D laser scanning equipment, and the tested surface was fractured by using a three-point bending beam test. The topographical analysis results were evaluated quantitatively by roughness parameters of roughness number (RN), fractal dimension (D), standard deviation of height distribution (σz), and arithmetic mean deviation of the surface topography (Ha). Multivariate analysis suggests the most effective of roughness number (RN) for evaluating the roughness of fractured surface. Furthermore, the RN of fractured surface was further correlated to the flexural toughness of the concrete, the relation between the fractured concrete surface roughness (RN) and flexural toughness follows an exponential function, which can be employed to quickly estimate its roughness of fractured surface by flexural toughness of the FRC. In conclusion, from the developed topographical analysis method, the hybrid fibers reinforced concrete shows the most significant improvement of the flexural toughness of the concrete, which suggests hybrid fiber reinforcement shall be a future solution for commercialization of the FRC in terms of high toughness and high durability.National Natural Science Foundation of China (Grant: 51578109

Research on the Evaluation of Green Logistics Based on Cloud Model

Businesses According to the theory of sustainable development, combining with the current development status of the social logistics industry and the characteristics of green logistics, constructing a green logistics evaluation index system. Using cloud model and Delphi method to calculate the cloud weight of green logistics evaluation index, qualitative and quantitative conversion of evaluation index is realized by cloud generator. Take Jiangsu Province as an example to do empirical research, using the cloud model and its algorithm to get the evaluation cloud of green logistics, observing the evaluation result directly and discovering problem easy by comparing the evaluation cloud chart with ruler cloud chart. The evaluation results show that the cloud model is more reasonable, and the credibility of the evaluation results is improved

Effect of steel fiber on the crack permeability evolution and crack surface topography of concrete subjected to freeze-thaw damage

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.National Natural Science Foundation of China (Grant: 527 51578109

Effect of fibers on the temperature field and radialdeformation behavior of self-compacting concrete pipesunder cyclic fire condition

In this paper, the radial deformation of fiber reinforced self-compacting con-crete (SCC) pipes under cyclic fire conditions is studied. A series of experimen-tal study on the temperature fields and radial deformation properties of steelmesh, polypropylene fiber (PP fiber), and macro steel fiber (SF) reinforcedSCC pipes subjected to fire is carried out. A novel method for measuring thedeformation of pipes under high temperature has been proposed. The resultsindicate that both micro PP fiber and macro SF are effective in decreasing thetemperature difference and reducing the radial deformation in each thermalcycle. A significant positive synergistic effect on decreasing the residual radialdeformation can be achieved by combined use of macro SF and micro PP fiber.The elastic theory is used to estimate the elastic portion in the total radialdeformation, and the elastic radial deformation is about 22.3% of the maxi-mum radial deformation in the first thermal cycle. Based on the elastic calcula-tion and observed experimental results, a simplified method for estimating themaximum radial deformation in the first thermal cycle is proposed.National Natural Science Foundation of China, Grant/Award Number: 5157810