Papers by Keyword: RPC

Abstract: This paper aims to evaluate mechanical behavior (compressive and flexural strength) of reactive powder concrete (RPC) with ferronickel slag (FNS) as quartz sand replacement. Standard laboratory tests were performed i.e. sieve analysis to determine the particle size distribution of the FNS, slump and density tests as well as compressive and flexural tests on the RPC. Promising results were obtained in this study. An increased consistency and density were observed upon increasing the FNS content. The utilization of FNS could lead to a compressive strength value of 86 MPa at 28 days. A higher strength enhancement in the early curing days (7 days) was observed than in the longer curing days (28 days), when FNS mixes were compared to reference mixes. The flexural strength result demonstrated two different phenomena at two different ages, where there was a slight rise at 7 days and relatively no increment at 28 days when FNS mixes were compared to the reference mixture.

Abstract: The impact resistance of micro-steel fiber-reinforced and hybrid fiber-reinforced reactive powder concrete is investigated in this study. Six groups of specimens were prepared with 2.5% volumetric contents of different combinations of fibers. For this purpose, micro-steel fibers with 6 and 15 mm length in addition to polypropylene fibers were used. Each group includes 12 identical specimens. The impact tests were conducted using the repeated drop-weight impact test of ACI 544-2R. However, higher drop-height (700 mm) and drop-weight (10 kg) were adopted to accelerate the failure and reduce the effort required to crack the specimens. The test results showed that the use of only 15 mm micro-steel fiber led to much higher impact resistance than other micro-steel fiber combinations. The recorded number of blows for the group with SF15 was 247, while those of SF6 and combined SF6 and SF15 were 127 and 112, respectively. The replacement of 0.5% of micro-steel fiber by 0.5% of PP fiber was found to reduce the impact resistance regardless of the type or combination of the used micro-steel fiber.

Abstract: An experimental program was directed in this study to evaluate the abrasion resistance of reactive powder concrete (RPC) under direct normal impact of water jet. Abrasion and compressive strength specimens were cast from six RPC mixtures using different single and hybrid distributions of 6 mm-length and 15 mm-length micros-steel fibers and 18 mm-length polypropylene fiber. Fixed mix proportions were used for the six RPC mixtures and with fixed total volumetric fiber content of 2.5%. In addition to the RPC mixtures, a normal concrete mixture was prepared for comparison purposes. All specimens were cured in the same conditions and tested at an age of 28 days. The test results showed that abrasion weight losses increase with time at rates that are independent of fiber type and fiber distribution. The results also showed that all RPC mixtures exhibited significantly lower abrasion losses than normal concrete. The lowest percentage abrasion weight losses were recorded for the mixture with pure 15 mm micro-steel, where after 12 testing hours, it was 0.41% of the total weight before testing. On the other hand, the mixture with pure 6 mm micro-steel fiber exhibited the highest percentage abrasion weight loss (0.98%) among the six RPC mixtures. Another conclusion is that the inclusion of polypropylene fiber to compose hybrid fiber distribution with micro-steel fiber led mostly to lower abrasion losses.

Abstract: The weakening of the behavior of reactive powder concrete (RPC) under high temperature is a major drawback; therefore, it is necessary to find an ingredient that improves their resistance under rising temperatures. The present work involves the use of metakaolin as a substitute for sand in a reactive powder concrete (RPC) in order to assess its effect on the mechanical strength at high temperatures. The test specimens are preheated up to 100°, 300°, 500°, 700° and 900°C, respectively following a well-defined cycle, thereafter subjected to a three-point bending followed by compression tests. Samples of the tested specimens were used for thermal, mineralogical and microstructural analyses using the thermogravimetric and differential thermal analysis (TG / DTA), the X-ray diffraction (XRD) and the scanning electron microscopic Analysis (SEM).The heating tests revealed that all the specimens exploded before reaching 500°C. However, they can withstand 300°C before exploding for different exposure durations depending on the metakaolin substitution ratio. Therefore, the mechanical tests were applied only on unheated specimens and those heated up to 100°C. The results showed that the use of metakaolin improves the mechanical strength of the RPC, both at room temperature (25°C±1°C) and at 100°C. This result is confirmed by the microstructure analysis, which revealed the absence of portlandite. The latter did react with the metakaolin silica to form new calcium silicate hydrates (CSH) enhancing the mechanical strength.

Abstract: RPC(Reactive Powder Concrete) is a kind of high performance concrete which has many excellent mechanical properties, e.g. ultra-high-strength, high tenacity and good durability, and it has been applied in engineering practice. However, at present the economic research about RPC bridge is few at home and abroad, which has hindered the development of RPC bridge to some extent. By means of the mechanical analysis and economic research about NC(normal concrete ) beam bridge of pre-stressed steel strand (the span is 40m), RPC beam bridge of pre-stressed steel strand and RPC beam bridge of pre-stressed CFRP(Carbon Fiber Reinforced Polymer) tendon after the sectional optimization has been done, this paper reach the conclusion that the RPC beam bridge can greatly reduce the sectional size of beam bridge and reduce the weight by 23.7% , besides, the total cost of RPC beam bridge of pre-stressed steel strand is almost same with the total cost of NC beam bridge during the entire service period of bridge. Therefore, considering the long-term perspective, the integrated economy of RPC beam bridge of pre-stressed steel strand is good.

Abstract: The possibility of obtaining and using technetium-99m-labeled glucose derivatives for the diagnosis of malignant tumors by the method of single photon emission computed tomography (SPECT) has been considered. The level of international and domestic developments on this topic has been analyzed. The authors made an attempt to develop pilot batches of lyophilizates on the basis of various glucose derivatives for further obtaining appropriate radiopharmaceuticals (RPC).

Abstract: In the original to remove steel and steel fiber reinforced concrete coarse aggregate in quartz powder and a small amount of activator, can boost steel fiber content, and its application in construction makes it more convenient, but how the penetration resistance works is not particularly clear. Through the penetration resistance experiment, found that when joined the SF and BF, RPC can still keep complete even after three times by penetration ,indicating the good performance of penetration resistance.

Abstract: The traction power supply system of electric railway has the disadvantages of heavy unbalanced three phase, large harmonics and reactive power. Based on back-to-back converter, railway static power conditioner (RPC) can effectively balance the load between two arms, compensate the harmonic current and reactive power. As the conventional PI control is difficult to trace the waveform, a dual-loop control scheme was applied. The control scheme reduces the influences of the factors, such as sampling and calculation delay, dead-zone, parameters’ shift, on the system stability and enhances the robustness of the whole system. It can also eliminate the negative sequence current and three-phase voltage fluctuations of the primary side, improve the power factor and harmonic filter, so that electrified railway power quality problems can be resolved perfectly. The whole design was provided. Analysis and simulation results testify the effectiveness of the proposed control scheme.

Abstract: To produce 130MPa reactive powder concrete with iron tailing sands as aggregation in an economic hot curing system, the effects of curing temperature, curing time and curing conditions on the reactive powder concrete was studied, the reasons of the strength of reactive powder concrete in different curing systems has the difference from the submicroscopic structure point of view was analyzed. The results show that use 90°C hot water to cure reactive powder concrete for 48h can lead it’s 28 day compressive strength reaches 140MPa, the flexural strength reaches 28MPa.

Abstract: Explicit finite element code was applied to simulate the steel fiber reinforced concrete (SFRC) and reactive powder concrete (RPC) target penetrated by kinetic energy projectile. Crater formation, spall of concrete target in penetration process was simulated very well. The numerical results of penetration depths are in good agreement with recent experimental results obtained from ballistic gun with 57mm caliber. The factors effecting on anti-penetration property of SFRC and RPC are analyzed. The results show that: the compressive strength and toughness of the target body have greater impact on anti-penetration performance in the range of projectile velocity 300m/s-600m/s. Anti-penetration capability of RPC concrete is stronger than that of ordinary steel fiber at the higher speeds.