Papers by Author: Shu Lin Zhan

Abstract: Mixing chlorine is one of the ways to ensure the theory and practical steel bars corrosion rate closer when mixing concrete for laboratory electrochemical accelerated corrosion and appropriate chloride dosage should guarantee the steel bars are in the critical corrosion state when we start to accelerated corrosion. By comparing the specimens’ experimental compressive strength, chloride-permeation resistance, corrosion potential measured by the half-cell potential method and polarization potential curves measured by the linear polarization potential method with different Nacl dosage, we get the appropriate Nacl dosage is nearly 1.90%, namely cl^- content is about 1.15%.

Abstract: To improve the accuracy of parameter identification and to reduce the test cost in the high-rise structure health monitoring systems , the paper proposes an optimal placement method combines genetic algorithms with improved information matrix criterion (GA-IIM). With traditional improved effective independent method (EFI-DPR), it is easily trapped into bureau of optimum solution, and the proposed method can resolve this problem. The solutions were coded by a two-dimensional integer array, each line stored a feasible solution and compulsory mutation was adopted to avoid the solution reappeared in the same position. To improve the convergence speed, each generation of optimal group was kept to the next one to participate in the competition. With the improved information matrix criterion embedded in the genetic algorithms, the placement design was produced. This technique was used to optimize the sensor placement of a nineteenth layer frame structure. Comparing the optimized sensor placement of the proposed method with that of improved effective independent method by the modal assurance criterion and the mean square error, the proposed method performs better.

Abstract: In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Abstract: Concrete durability is one of the most important considerations in the design of new structures in aggressive environments. It generally depends on the quality of the concrete surface and the cracks of concrete. In this paper, the rebound numbers of concrete cast using controlled permeability formwork (CPF) and ordinary steel formwork were determined. And the early age shrinkages of concrete cured in dry environment of 20±2°C, 75±5% RH, in sealed condition with plastic film and in covered condition with CPF liner were measured. Testing results indicated that CPF could improve the concrete surface hardness and reduce the early age shrinkage of concrete. So CPF can enhance concrete durability and prolong its life-span.

Abstract: Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.

Abstract: The influence of superplasticizer (SP) and shrinkage-reducing admixtures (SRA) on the early age shrinkage of concrete with a controlled slump of 80±10 mm was investigated using a measuring apparatus developed specially. In addition, the influence of early age curing methods on the early age shrinkage of concrete was also studied. The early age shrinkage was increased sharply by the addition of SP when the concrete was exposed to the drying environment after initial setting. While under the same conditions the addition of SRA could reduce the early age shrinkage effectively. However, under sealed curing conditions at the early age, concretes with or without chemical admixtures all exhibited low early age shrinkage, which implies if a good method for curing could available then the addition of SRA will be unnecessary and the adverse effect of SP in enlarging shrinkage could also be eliminated.

Abstract: A series of water-soluble polycarboxylate-type superplasticizer (PCA) were synthesized by free-radical copolymerization of methyl acrylic acid and methoxy poly(ethylene glyco1) monoacrylate macromonomers in water solutions．Micelles were formed from the resultant PCA with predetermined hydrophobic and hydrophilic blocks in water. The hydrodynamic diameter and size distribution of micelles were determined by dynamic light scattering. The change of the concentration of the electrolyte results directly in the variation of the dispersing force of PCA in cement paste. The dispersing force degrades with increasing electrolyte concentration.

Abstract: Based on designed and manufactured test equipment of concrete early age shrinkage, the influence of shrinkage reduce agent (SRA) on early age autogenous shrinkage of concrete was researched. The test results show that early age autogenous shrinkage of concrete was reduced with SRA added and the shrinkage-reducing ratio increased with concrete strength grade heightened. SRA could also greatly reduce early age autogenous shrinkage of concrete added with pulverized ly ash or slag. Superplasticizer would increse early age autogenous shrinkage of concrete, and the shrinkage was larger than those without superplasticizer, even the SRA mixed into. Furthermore, early age curing should be enhanced for concrete with superplasticizer.