Advanced Materials Research Vols. 785-786

Abstract: This study is to acquire the confirmation data regarding the cathodic protection (CP) characteristics for slabs in marine bridges and piers exposed to hash seawater environments. It was possible to confirm the performance of CP only by the measurement of CP potentials for the slab specimens applied with zinc mesh sacrificial anode CP system. The CP current density for the cathodic protection (CProt) that CP started after a repair of corrosion was 2 times higher than that for the cathodic prevention (CPrev) that CP commenced from the beginning of experiment, and the most of protection current density (87.0-91.5%) flew to the closer top rebar in slab specimens. 4 hour depolarization potentials were higher in the CPrev system than in the CProt one, and it was confirmed that the CPrev has more protection effect with less protection current, comparing to the CProt. It was also confirmed that the CP of both CPrev and CProt by means of zinc mesh sacrificial anode for reinforced concrete structures were very effective corrosion protection technology in marine environment.

Abstract: Corrosion of reinforcement steel is a major factor affecting the deterioration of reinforced concrete structures. During corrosion, steel undergoes several phases of chemical reactions with consequent variation in steel section geometry and mechanical properties. At ultimate corrosion stage, the effective cross section area of steel is reduced with equivalent decrease in load carrying capacity leading to unsafe structures. During initial phase of corrosion, chemical reactions generate new products which irregularly increase steel bar diameters. The resulted products induce additional stresses on the structural member, causing cracking and spalling of the concrete cover, and subsequently faster deteriorate the member strength. This paper presents the effect of the induced stresses of corrosion products on concrete cracking experimentally and numerically. Experimentally several pull-out specimens were tested to identify the effect of corrosion at different stages, and, numerically, a two dimensional finite element model was developed to study the crack initiation and propagation in concrete using nonlinear analysis and specific properties for both steel and concrete elements.

Abstract: In this study, response surface methodology (RSM) was used to optimize the medium based on the PlackettBurman and Central-Composite Designs for the production of pullulan using a strain of Auerobasidium pullulans A225. Peptone, K₂HPO₄, and MgSO₄ were found to have significant effects on pullulan production using the PlackettBurman Design. The steepest ascent experiment was adopted to determine the optimal region of the medium composition. The concentrations of the three above mentioned compounds were further optimized using the Central-Composite Design. Results showed that the final concentration of medium optimized using RSM was 6.34 g/L peptone, 7.91 g /L K₂HPO₄, and 0.46 g/L MgSO₄. Production of pullulan reached 72.56 g/L under the optimized medium.

Abstract: Measuring techniques for vertical deformation and horizontal deformation of concrete were introduced in the paper. Based on these techniques, concrete deformation about reference concrete and shrinkage-compensating concrete were studied. The results show that workability of concrete was almost not affected by expansive agent. Usually deformation testing began when the mold has been removed 24 hours after casting according to present standard, but the reaserch shows that the time of starting measurement has a little influence on deformation of reference concrete, while its vastly affected on those of shrinkage-compensating concrete with expansive agent. Thus, its essential to judge time-zero accurately for shrinkage-compensating concrete. Before final set, concrete is on the plastic stage when the concrete has no enough stiffness to store expansive energy, so the measurement results should be zeroed to the time of final set especially for concrete with expansive to evaluate expansive validity better.

Abstract: With the tunnel growing more long and deep,heat injury problems have become increasingly prominent.In order to analyze how would the environment of high ground temperature impact on compressive strength of shotcrete, experiment was designed to explore the compressive strength of C25 shotcrete at 28d age by simulating environmental. The test results show that: water tank and the oven can more accurately simulate the natural hot-humid and hot-dry environment; Compared to the standard curing conditions, Whether in the hot-humid environment or hot-dry environment, the compressive strength of shotcrete is decreased. Mixed with 25% fly ash can improve the compressive strength of shotcrete in hot-humid environment.

Abstract: Epoxy asphalt has been proposed for the steel bridge deck and the heavy traffic on the road because it shows excellent heat resistance, free from bleeding, low temperature cracking resistance. In this paper, the curing characteristics of epoxy resin system and epoxy asphalt system were studied. The curing time and the viscosity of different epoxy resin and epoxy asphalt systems were tested. Experimental results indicated that: In the pure epoxy system, the curing time was decreased with the content of curing agent and accelerator increasing, and increased with the diluents addition. Epoxy asphalt was prepared after asphalt system addition; the viscosity was increased with curing time increasing and accelerator content increase. The allowable reserved time was decreased with the accelerator content increase. The growth of the system viscosity was slowly and the curing of epoxy asphalt was hindered with the more asphalt addition.

Abstract: This paper reports that according to the principle of EMW-absorption, thermal insulating EMW-absorber for building was designed and theoretically simulated of the λ/4 type. The EMW-absorption properties of composites in the band of 2-4 GHz were examined, A maximum absorption of-20 dB at 3 GHz and 80% of bandwidth below-10 dB was achieved under following conditions: using 380Ω/□ resistive film, specimen thickness of 2 cm. Similarly, absorbing materials for 2.45 GHz have successfully designed and prepared,a maximum absorption of-17 dB at 2.45 GHz, and 65% of bandwidth below-10 dB can be reached. New materials can be used for electromagnetic interference protection for WLAN and indoor electromagnetic radiation pollution control.

Abstract: A novel foaming agent was prepared using animal hoof and horn as raw materials via calcium hydroxide as a catalyzer and the performanc of the product was measured. The results show that the expansion rate of foaming agent can be more than 20 times, and the stability of foaming is very excellent. The foaming agent was used for preparing foam concrete and the performanc of the foam concrete was also tested. The results show that the thermal conductivity can be kept between 0.055 and 0.234 W/(m·k), and the foam concrete possesses light masses, little density and well thermal insulation.

Abstract: One of the main objectives of this study was to activate the pozzolanic activity of sludge, produced by municipal sewage treatment plants (MSTP), make it become an admixture to replace a part of cement in concrete. Nowadays, a significant quantity of MSTP sludge is obtained in China. That is why this paper examines the possibility of adding this waste product to plain concrete with Portland cement. Preliminary studies are carried out on using MSTP sludge as an admixture by thermal (calcining) and mechanical (grinding) treatment. The pozzolanic activity of the calcined sludge ash (CSA) evaluated by Cement Mortar test. The CSA-blended cement concrete was formed into specimens of cubic concrete with 100 mm×100 mm×100 mm. They are with 30 wt. % cement replaced by CSA, which was prepared by the optimal activation conditions. The Cement Mortar test results revealed that the optimal activation conditions of CSA were as follows: calcined at 800°C for 2.5 hours followed by fast cooling in air and then ground until 60 minutes. Besides, the compressive strengths of concrete specimens with added 30% CSA were 103.6% and 105.3% of those of the ordinary Portland cement concrete specimens at 7 and 28 days, respectively. These results demonstrate the feasibility of recycling MSTP sludge as an admixture in concrete for construction engineering.

Abstract: In order to prove that the ability of the construction of the base course with cement-fly-ash-flushedby-seawater stabilized crushed-stones and the materials‘ spreading across the country in the future, the paper start to analyze and research the micro reaction and macro properties about the cement and fly-ash-flushed-by- seawater binder along with the cement and typical fly-ash binder, which based on a series of contrastive laboratory tests. When the mixture ratio of cement and fly-ash-flushed-by-seawater binder ,In addition, the key techniques indexes for construction ,which are controlled seriously ,It is unparalleled that the utilization of the cement and fly-ash-flushed-by-seawater stabilized crushed-stones in the construction of base course.