Ultimate Crack Resistance Research Articles

Research on the Development and Joint Improvement of Ceramsite Lightweight High-Titanium Heavy Slag Concrete Precast Composite Slab

Despite the continuous improvement in the research and development of concrete precast composite slab technology, problems like easy cracks and excessive weight at the joints remain. In this study, high-titanium heavy slag was mixed with different kinds of ceramsite to prepare ceramsite lightweight high-titanium heavy slag concrete. The joint of the composite slab was optimized to develop a novel ceramsite lightweight high-titanium heavy slag concrete precast composite slab, hereinafter referred to as “CLHCPCS”. Two CLHCPCS and one ordinary concrete composite slab were prepared. This study analyzed the effects of new materials and improved joints on the flexural capacity and crack resistance of CLHCPCS. It concluded that the density of high-titanium heavy slag concrete with shale ceramsite decreased by 12.0%, and the density of high-titanium heavy slag concrete with fly ash ceramsite decreased by 10.6%. At a 30% dosage of fly ash ceramsite, the compressive strength and splitting tensile strength of concrete reached the maximum. At a 20% dosage of shale ceramsite, the mechanical properties were optimal. Finally, fly ash ceramsite was selected as part coarse aggregate of CLHCPCS. CLHCPCS 1 and 2 demonstrated superior ultimate bearing capacity and crack resistance than ordinary concrete composite slab DBS1, with its ultimate bending capacity test value higher than the average value of ordinary concrete composite slab. ANSYS established the joint model of CLHCPCS for a bending simulation test. The stress and strain distribution of the model and the ultimate bending capacity under the plastic line method were obtained, consistent with theory and experimental analysis results.

Flexural behavior of wet joints in steel-UHPC composite deck slabs under hogging moment

A new type of steel-UHPC composite slabs (SUCS) with PBL shear connectors are used as bridge decks in an ultra-long-span composite cable-stayed bridge under construction in China. SUCS can be prefabricated in the factory and then transported to the construction site for assembly. The steel parts of the adjacent SUCS shall be welded together and UHPC wet joints, which are the weak parts of the bridge deck, shall be cast in-situ to finish the assembly. Full-scale tests of three SUCS with dovetail-shaped wet joint or newly-proposed construction-friendly rectangular wet joint were conducted to investigate the flexural behavior under hogging moment. Flexural failure of the interface section occurred in all specimens. The ultimate capacity and crack resistance of rectangular wet joints can be close to the dovetail-shaped wet joints with the same notch length. The phenomenon that tenons were pulled out from the rectangular notch appeared in rectangular wet joints during loading, which was especially prominent when the notch length was short, and the ultimate capacity and crack resistance would be reduced. Experimental results showed significant differences between cracking behavior of the interface and the non-interface, revealing the importance influence of wet joints on durability. The ultimate capacity was analyzed theoretically, and discussions were made on the reduction of ultimate capacity caused by wet joints. In addition, a crack width prediction model was obtained by modifying the model in GB50010-2010, which was based on the comprehensive analysis method combining bond-slip method and non-slip method. The modified model can give satisfactory prediction results of crack width for both interfacial and non-interfacial cracks.

BEHAVIOUR OF TERNARY BLENDED CEMENT CONCRETE SLAB WITH STEEL FIBER UNDER IMPACT LOADING

Statement of the problem. An experimental investigation of impact strength of ternary blended cement concrete slab with steel fiber under impact loading was carried out. The amount of replacement of binder with Fly ash varies from 10 to 30 % in step of 10 %, glass powder from 20 to 40 % in step of 10 % and fiber volume fraction from 0.75 to 2.25 % in step of 0.75 %. Parametric performance of ten 600 × 600 mm, 60 mm thick reinforced concrete slabs was evaluated. The impact test on the slab was conducted by dropping a steel ball from a height of 457 mm under impact setup. The parameters like failure mode, the impact energy of first crack and ultimate crack failure, ductility index, failure pattern, ultimate crack resistance, crack resistance ratio were investigated when subjected to impact load. Results. The test results reported that the slab specimen S7 shows better performance in strength.

Structural Behavior of Fibrous-Ferrocement Panel Subjected to Flexural and Impact Loads.

Ferrocement panels, while offering various benefits, do not cover instances of low and moderated velocity impact. To address this problem and to enhance the impact strength against low-velocity impact, a fibrous ferrocement panel is proposed and investigated. This study aims to assess the flexural and low-velocity impact response of simply supported ferrocement panels reinforced with expanded wire mesh (EWM) and steel fibers. The experimental program covered 12 different ferrocement panel prototypes and was tested against a three-point flexural load and falling mass impact test. The ferrocement panel system comprises mortar reinforced with 1% and 2% dosage of steel fibers and an EWM arranged in 1, 2, and 3 layers. For mortar preparation, a water-cement (w/c) ratio of 0.4 was maintained and all panels were cured in water for 28 days. The primary endpoints of the investigation are first crack and ultimate load capacity, deflection corresponding to first crack and ultimate load, ductility index, flexural strength, crack width at ultimate load, a number of impacts needed to induce crack commencement and failure, ductility ratio, and failure mode. The finding revealed that the three-layers of EWM inclusion and steel fibers resulted in an additional impact resistance improvement at cracking and failure stages of ferrocement panels. With superior ultimate load capacity, flexural strength, crack resistance, impact resistance, and ductile response, as witnessed in the experiment program, ferrocement panel can be a positive choice for many construction applications subjected to repeated low-velocity impacts.

Comparison of Fracture Test Methods for Evaluating the Crack Resistance of Asphalt Mixture

For the better understanding of fracture test method to evaluate the crack resistance of asphalt mixtures, the current test methods and evaluation indexes were theoretically and experimentally compared, including the indirect tensile test, single edge notch beam test, semicircular bending test (SCB) and disk-shaped compact tension test. The stress intensity factors for different tests were compared, and the appropriate range of notch depth was determined. The SCB was finally selected as the test method for evaluating the crack resistance of the asphalt mixtures. According to the relationship between the fracture energy and notch depths, the essential fracture energy of asphalt mixtures was calculated, and it was recommended as the evaluation index of asphalt mixtures for crack resistance. Furthermore, the failure process of the SCB was analyzed, and the contraflexure point on the load–displacement curve was found and defined. The fracture energy at the contraflexure point could be used to evaluate the ultimate crack resistance of the asphalt mixtures. The application of the essential fracture energy and the contraflexure point can correspond to the actuality of the asphalt pavement, which provides a reference for the crack resistance research of asphalt mixtures in the future.

Impact Testing on Reinforced Concrete Slab with Bfrp Bars as Reinforcement

Basalt Fibre Reinforced Polymer (BFRP) bar is an alternative to steel and glass fibre for reinforced concrete. Their unique characteristics makes them favourable compared to the other alternative materials. According to previous studies the BFRPbars are lighter and stronger than steel and has higher bending strength. But the research regarding the impact strength of BFRP bars are very limited. But the impact strength of materials is very important for many critical designs due. Thus, prompting the study of impact strength of BFRP bars. Basic tests were done to determine the strength of the materials to be used. Slabs of 550mm ×550mm ×50mm are made with varying centre to centre distance between bars in both cases of steel and basalt bars. The slabs are subjected to impact loading through the drop weight impact and the values such as crack length, width and depth are observed, and the result is observed in the form of ultimate crack resistance. Even though slabs with maximum centre to centre distance between bars failed very easily in both cases, the slabs with minimum centre to centre distance between bars gave considerable impact strength.

Impact of shear connectors on the behaviours of box-girders with corrugated webs

The impact of different shear connectors (perfobond leisten (PBL) shear connectors and stud shear connectors) on the mechanical performances of prestressed concrete (PSC) composite box-girders with corrugated steel webs was studied. Mechanical properties were researched by conducting experiments on two specimens with PBL shear connectors or stud shear connectors; these properties included the ultimate bearing capacity, the flexural stiffness, crack resistance and the efficiency of prestressing of the girder. The test results showed that, compared with the stud shear connectors, PBL shear connectors greatly improved the ultimate bearing capacity, flexural stiffness and crack resistance of PSC composite box-girders with corrugated steel webs. However, regarding the efficiency of prestressing, the PBL shear connectors did not perform as well as the stud shear connectors.

On low-velocity impact response of SIFCON slabs under drop hammer impact loading

The response of thin slabs of Slurry-Infiltrated Fibrous Concrete (SIFCON) with and without reinforcement under low velocity impacts is explored via drop-hammer impact experiments. For comparison purpose, plain cement concrete (PCC) and reinforced cement concrete (RCC) slabs were also cast and tested. To produce SIFCON slabs made with binary cementitious materials, the pre-determined concrete mixtures were designed with 15% of silica fume, 30% of blast furnace as a partial substitute of cement along with a constant 10% of hooked end steel fibres by volume fraction. The replication of a low-velocity impact on slab was achieved by dropping a steel ball (weighing 4.5 kg), with fall height of 457 mm, via the utilization of a self-fabricated drop-hammer impact test device. The parameters like first crack and ultimate failure energy absorption capacity, ultimate crack resistance, crack resistance ratio, ductility indices, and failure pattern were examined. The test results reported that the incorporation of binary blends of silica fume and slag in SIFCON matrix shows better performance in terms of strength and durability characteristics.

Impact resistance of oil palm shells concrete reinforced with polypropylene fibre

This study examines the results from an investigation on the impact resistance of oil palm shells (OPS) concrete. The use of OPS as a substitute for regular aggregate in lightweight concrete will help reduce its negative environmental influence. There is a lack of research on the impact resistance and crack behaviour of concrete; specifically in OPS lightweight concrete reinforced by polypropylene (PP) fibre. The replication of a low-velocity projectile effect on slab samples was achieved by dropping two types of steel ball (weighing 0.380kg and 1.25kg), with drop height of 360mm, through the utilization of a self-fabricated drop-weight impact test rig. A total of 12 cube specimens, with dimensions 100×100×100mm, were used to prepare 36 slabs with various thicknesses. The 36 slabs were prepared using a concrete cutting machine to excise the three cube specimens from each mixture, into 20, 30 and 40mm thicknesses. Impact resistance tests were then performed on them. The results demonstrate that there was a strong linear relation between volume fraction of PP fibre and impact resistance; as well as crack resistance ratio. This relation was indefeasible by changing the thickness from 20mm to 30mm and 40mm. Although increasing the thickness improved the impact resistance significantly, the effect was more pronounced for ultimate failure crack resistance than for first crack resistance.

Impact Resistance Behaviour of Banana Fiber Reinforced Slabs

This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

Impact Resistance Behaviour of Light Weight Rice Husk Concrete with Bamboo Reinforcement

This paper investigate the performance of lightweight rice husk concrete (LWRHC) with varied bamboo reinforcement content for the concrete slab of 300mm × 300mm size reinforced with varied slab thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.65 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter and slab thickness. 5% RH content exhibit better first and ultimate crack resistance up to 1.80 times and up to 1.72 times respectively against 10% RH content.

Impact Resistance Performance of Kenaf Fibre Reinforced Concrete

This paper investigate the performance of kenaf fibre mesh reinforced concrete (KFMRC) with varied kenaf fibre mesh reinforcement content for the concrete slab of 300mm × 300mm size reinforced with different mesh diameter at constant spacing with varied slab thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.40 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of mesh reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against kenaf fiber diameters by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the slab thickness. The threshold (highest) values for service crack and ultimate crack is 47.9 N/mm2 and 130.58 N/mm2 respectively observed and computed for 50 mm slab with 7 mm diameter mesh.

Impact Strength of Oil-Palm Shell on Lightweight Concrete Slabs Reinforced with a Geo-Grid

AbstractThis paper focuses on the biotechnology of concrete. Oil palm shells (OPSs) are a main solid pollutant of the environment and can be used as a replacement for the conventional aggregate in lightweight concrete. An experimental investigation on the impact resistance of OPS lightweight concrete with a geo-grid was performed. A mix design was determined through various trial mixes to ensure the OPS lightweight concrete could achieve the required structural performance. A self-fabricated drop-weight impact test rig was used to simulate a low-velocity projectile impact on the slab specimens. Three parameters were tested for impact resistance on specimens with and without geo-grid reinforcement, as follows: (1) OPS content, (2) geo-grid types, and (3) geo-grid layers. Inclusion of OPS reduces the impact resistance of concrete and a geo-grid layer improves the impact resistance, but the effect is more pronounced for ultimate crack resistance than the first crack resistance. A comparison between geo-grid ...

Impact resistance performance of green construction material using light weight oil palm shells reinforced bamboo concrete slab

This paper investigate the performance of lightweight oil palm shells (OPS) concrete with varied bamboo reinforcement content for the concrete slab of 300mm x 300mm size reinforced with different thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.2 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter for a constant spacing for various slab thickness using 0.45 OPS and 0.6 OPS bamboo reinforced concrete. The increment in bamboo diameter has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Increment in slab thickness of the slab has more effect on the crack resistance as compare to the increment in the diameter of the bamboo reinforcement.

Impact resistance of sustainable construction material using light weight oil palm shells reinforced geogrid concrete slab

This paper investigate the performance of lightweight oil palm shells (OPS) concrete slab with geogrid reinforcement of 300mm × 300mm size with 20mm, 30mm and 40 mm thick casted with different geogrid orientation and boundary conditions subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.2 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance the slab thickness, boundary conditions and geogrid reinforcement orientation. Test results indicate that the used of the geogrid reinforcement increased the impact resistance under service (first) limit crack up to 5.9 times and at ultimate limit crack up to 20.1 times against the control sample (without geogrid). A good linear relationship has been established between first and ultimate crack resistance against the slab thickness. The orientation of the geogrid has minor significant to the crack resistance of the OPS concrete slab. OPS geogrid reinforced slab has a good crack resistance properties that can be utilized as a sustainable impact resistance construction materials.

A study of the high-temperature strength and crack resistance of the metal of the body of stop valve from high-chromium steel 15Kh11MFBL after long-term operation

The applicability of the rapid method for determining the ultimate long-term strength, endurance, and crack resistance of cylindrical specimens with three sharp notches, which has been developed by V. I. Gladshtein for pearlitic steels, to chromium steel 15Kh11MFBL is considered. It is shown that the results of evaluation of high-temperature strength by the standard method and with the use of notched specimens supplement each other. Prediction of the time before failure of smooth specimens from notched specimens makes it possible to perform the evaluation for 100,000–300,000 h, which is impossible by direct testing at operating temperatures.

ZIRCONIUM CERAMICS AND ITS FUTURE PROSPECTS IN UKRAINE

Ceramics, it seems, are among the first artificial materials created and utilized by people. The range of their application is widening continuously. Considerably novel varieties of ceramics, such as technical or fine ceramics, are becoming more and more significant in our life. They are used not only in households, industry, communications, transport, and agriculture, but in man himself, replacing some parts of his body. According to H. Yanagida [1], the production of technical ceramics based on complex knowledge can determine the prosperity or decline of a country [1]. Zirconia-based materials occupy a special place in the list of the most promising ceramics that can be produced on a large scale. In addition to the high mechanical properties predominantly resulting from the effect known as transformation toughening, the high strength and crack resistance, and the refractoriness and other properties possessed by all ceramics, which are hard, abrasion-resistant, and corrosion-resistant materials, the latter have a unique capacity to be a direct efficient transformer of the energy of organic fuel into electrical energy by the method of fuel elements. The Ukraine Zirconia Company has developed a simple technology for fabricating ceramic (zirconia-based) parts from sand, i.e., zircon of the Volnogorsk deposit. Using zirconium hydroxide produced by the Volnogorsk State mining and metallurgical works (Fig. 1), special milling, cold isostatic pressing, and appropriate sintering regimes, the Ukraine Zirconia Company produces zirconia ceramics with a structure stabilized by yttrium and magnesium oxides (Y-PSZ and Mg-PSZ, respectively). The typical properties of the ceramics are presented in Table 1. At the Hannover Messe-98 exhibition, the company presented such articles as – cutting tools, cutting edges, knives, surgical scalpels; – artificial joints and other biological implants; – friction and frictionless bearings, etc.; – valves, gaskets, and pump parts; – tools for pressure treatment and cutting of metals; – powders for plasma deposition of heat-insulating coats; – ingots for electron-beam spraying; – jewelry; – other articles. The exhibited specimens showed that zirconia ceramics are among the most widespread structural materials. Parts from zirconia ceramics are quite marketable; the demand for them throughout the world increases by 15 – 20% every year. We are convinced that the understanding of the mechanism of transformation toughening and the ability to realize it in the long-term process of the creation of a ceramic part, beginning with the synthesis of the powder and ending with the mechanical treatment of ready ceramics, provide a high level of properties and a wide range of products. After the discovery of the effect of transformation toughening [2], numerous works appeared throughout the world concerning the physical phenomena responsible for the high mechanical properties of ceramics based on ZrO2 and the creation of ceramic materials with record-breaking values of strength and crack resistance exceeding 2 GPa and 15 MPa m 2 (!), respectively, in the system of tetragonalstabilized zirconia polycrystals (Y-TZP). The typical values of the ultimate bending strength and crack resistance (1 GPa and 7 – 10 MPa m , respectively) for ZrO2 partially stabiRefractories and Industrial Ceramics Vol. 41, Nos. 9 – 10, 2000

Effect of Reinforcement of a Silicon Nitride Matrix by Silicon Carbide Whiskers

A fine-grain high-density tough matrix is a general prerequisite for synthesis of high-strength and crack-resistant composite materials, as well as its self-reinforcement with extended grains of β-Si3N4 and reinforcement with β-SiC crystals. Both approaches are used simultaneously in the present work. It is shown that the reinforcement of a silicon nitride matrix based on ultradisperse powder compositions by SiC whiskers of grade TWS provides hot-pressed ceramics with a high ultimate bending strength (950 MPa) and crack resistance (10 MPa · m1/2). Reinforcement by fine or coarse whiskers increases the crack resistance by 30% with respect to monolithic Si3N4. Composites reinforced by TWS silicon carbide whiskers preserve their high strength up to 1500°C.

An ultimate crack resistance concept

A two‐parameter fracture criterion is discussed in terms of an ultimate crack resistance concept. The difference is found between the failure assessment diagram and the ultimate crack resistance. The concept of an ultimate crack resistance provides one with the ability to estimate crack resistance behaviour in cases of brittle, ductile and intermediate fracture states with the customary use of stress intensity factors.

A concept of ultimate crack resistance

The ultimate crack resistance is regarded as a two-parameter fracture criterion. The concept of ultimate crack resistance enables one to estimate the state of a material and to compute the crack resistance of machine parts in the processes of brittle, transient, and viscous fracture. In relations used for numerical analysis, the stress intensity factors are preserved but the corresponding characteristic of the material is made more complicated.