Key Engineering Materials Vols. 405-406

Abstract: Reactive powder concrete (RPC) is a new kind of material with very high mechanical behavior and durability, however, high cost and complex procedure to make RPC result in hardly apply to engineering in large scale. a new low-cost RPC that compressive strength exceeds 130MPa was prepared with the replacement of quartz sand, crushed quartz and partial of silica fume by fly ash, slag and natural fine aggregate in the paper. Manhole cover that made from the low-cost RPC can meets the requirements of different situations, such as special road, motorway, etc.

Abstract: The analysis of material variables and curing procedure design are the key techniques of UHPCC. Material variables include cement-water ratio, silica fume content, sand’s content and size, filling powder’s content and type. Based on the objective of compressive strength, UHPCC with compressive strength 180MPa was developed based on the influence analysis of material variables on its performances and the substitution of silica fume by lime stone powder. By the analysis of the influences of early curing method, initial time, duration time and high temperature curing, curing procedure design was proposed, i.e. early water curing at first after 24 hours of casting and then high temperature steam curing. Based the simplified constitutive relation of UHPCC, the ultimate flexural of UHPCC hybrid girder was analyzed. This paper can be a basis of UHPCC-NC hybrid structure analysis.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. It is concluded that, in order to achieve better understanding of fresh concrete, especially self-compacting concrete (SCC) and high-performance concrete (HPC), a clear methodology of research should be established as the first step. It is suggested that there is no unique workability test method suitable for all the range of fluidity of fresh concrete, and a specific method should be identified for a proper range of fluidity. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors. Most literature proved that the flow of concrete depends both on positive effect and negative effect, the former promote fluidity, such as dispersing, filling and lubricating, and the latter restricts fluidity, such as formation of particle coagulation, an increase of wettable surface of solid particles and mechanical interlock.

Abstract: A new technique for construction of steel tube-confined concrete (STCC), i.e., vacuum-assisted pumping technique was put forward in this paper, and the simulation research both in laboratory and on the building site had been done. The test results showed that the formation of air membrane between steel tube and core concrete could be effectively inhibited by controlling the air content of concrete through optimizing design for mix proportion of concrete and by regulating the vacuum pressure in steel tube during the process of concrete pumping, and thus the density of concrete was increased and the bond between steel tube and concrete was improved. Therefore, the performance of STCC structure such as the ultimate load-bearing capacity was enhanced. Moreover, this new technique can decrease the difficulty of concrete pumping. The technology had been applied in the construction of Yichang Yangtze River Bridge in Yichang-Wanxian railway.

Abstract: This paper studied rheological properties of fresh cement pastes and adsorption behavior of superplasticizers which are FDN-5R, a type of naphthalene sulfonic acid based condensate, 3350, a type of polycarboxylate superplasticizer, by R/S-SST rheometer and UV Visible Spectrometer. Results show that superplasticizers can reduce the flocculation structure of fresh cement paste obviously and reduce the yield stress and apparent viscosity. The turn of thixotropic property is: blank sample > FDN-5R > 3350, especially the sample with 3350’s curve of upward and downward almost match together and the thixotropic property drives to zero. Shearing stress, apparent viscosity and thixotropic property are decreased, adsorption capacity is higher by the superplasticizer adding. The bigger effectual adsorption, the better dispersive action of flocculation and rheological properties of fresh cement pastes. Therefore, we can understand the effect mechanism and properties of superplasticizer much better by combining the molecular structure, adsorption capacity, dispersive action and rheological properties.

Abstract: With the wide application of pumping concrete， and the increasing of pumping height and distance， more and more attention of researchers focus on the workability of pumping concrete. Traditionally， the research method of workability of pumping concrete is mainly experiment. With the increasing of pumping height and distance，experimental method for workability of pumping concrete becomes more difficult. Combining simulation computation and experimental method to solve pumping construction problems of concrete under complicated conditions is a feasible method. Research progress about experimental method and simulation computation of workability of pumping concrete are presented， which would provide research thinking and research method for combining simulation computation and experimental method.

Abstract: To super high-rise building, concrete pumping construction is an inevitable choice. This paper introduces the application status and development trend of concrete pumping construction in the super high-rise projects at home and abroad, introduces high-rise pumping concrete from the selection of raw material, mix design, performance evaluation and so on, sums up technical specification of concrete pump and pumping concrete pipe-laying method, in order to provide reference for the high-rise concrete pumping construction in Guangzhou West Tower.

Abstract: As large flow pattern lightweight aggregate concrete is float up easily, slump loss quickly under the pumping pressure, and pumped hard. Improving the homogeneous and Reducing the slump loss will be the key technology of pumping lightweight aggregate concrete. Researched on the technology of large flow pattern lightweight aggregate concrete, and prepared the concrete, whose strength is over 50MPa, was suitable for high-rise building. The concrete has been succeeded in pumping on high-rise building, and the height of pumping is 181.4m.

Abstract: This paper presents an investigation on the effects of self-combustible gangue powder on the water requirement of normal consistency and setting time of blended cement paste. It was observed that the water requirement of paste increased, when self-combustible gangue powder were substituted partially for cement. It was found that self-combustible gangue powder have little effect on the setting time of blended cement paste with dosage from 10% to 30%,and this means the range of dosage is a appropriate mix content.