Papers by Author: Lin Hua Jiang

Abstract: The mechanical properties of C100 high-strength concrete used for frozen shaft were studied in this research. The results demonstrate that: The cementitious materials 570kg/m3 concrete 28 strength is only 104.5MPa, which is lower than the C100 requirements; the early strength (3d) of the concrete doped with 30% admixture is less than 20% admixture concrete, but with the age increase, its strength gradually reaches close to concrete doped with 20% admixture, and eventually exceeds the concrete doped with 20% admixture.The tension-compression of high strength concrete doped with 15% fly ash and 15% slag is the smallest, while the tension-compression of the concrete doped 10% fly ash and 10% slag reaches the maximum.The Poisson's ratio of C100 concrete is between 0.20 and 0.24; the compressive elastic modulus is about 50GPa; and the tensile elastic modulus is about 110GPa.

Abstract: The chloride binding mechanisms of different mineral admixtures under the condition of stray current and NaCl solute were researched. The electric potential titration was used to measure the content of total chloride ions and free chloride ions. The results show that using of mineral admixture could effectively inhibit the destructive action of the stray current to the stability of bound chloride ion in cement paste. Among all, the most effective mix proportion on chloride-induced corrosion is the mixture with only slag, then the double mixing of fly ash and slag, the last comes the mixture with only fly ash.

Abstract: Non-structural cracking of concrete is a serious problem and the underlying phenomena, namely, shrinkage and creep, need to be better understood. Much research has been devoted to this complex problem. However, despite major successes, the phenomenon of autogenous shrinkage is still far from being fully understood. The paper discusses the main aspects of concrete shrinkage, with a focus on autogenous shrinkage, which are especially important in low water/binder ratio concrete. These aspects include the theories of physical mechanism, prediction models and future research trends. Shrinkage of concrete due to moisture changes, which result in surface and capillary tension, was reviewed. The mechanisms often cannot be directly linked to the macroscopically observed dilatation/contraction. An overview of recent model developments is also presented.

Abstract: An experimental program was carried out to obtain the density and compressive strength of lightweight expanded polystyrene (EPS) concretes. Tauchi’s approach was adopted to reduce the numbers of experiment. Four control factors and two responses were used. The results show that EPS dosage had the most significant effect on density and compressive strength. The density value of EPS concrete showed an almost linear decrease as the volume of EPS and W/C parameters increased, but results in a decrease in compressive strength.

Abstract: In this article, some empirical and theoretical models accounting the relationship between the strength and pore structure of cement-based materials is reviewed and analyzed. From the literature review and analysis, it can be found that the total porosity can be singly used to characterize the relationship between compressive strength and pore structure, but can not be applied into describe the relationship between pore structure and tensile strength. Another major parameter of pore structure - pore size distribution, will have a major impact on strength; the relationship between pore structure and tensile strength is for most models of cement paste, without the consideration of aggregate, and the application of the model must comply with the relevant assumptions. The research on the relationship between the tensile strength of concrete is still at a preliminary stage, requiring more theoretical and experimental study.

Abstract: A new method was presented to study the content of the soluble alkali in mortar. The method was based on mixing powdered sample with distilled water with two water-solid ratios and measur-ing the pH of the suspension. According to the measurement result of the suspension, the content of soluble alkali in mortar was calculated. The parameters such as water-solid ratio and measuring ac-curacy which affected the calculated result were investigated. The calculated result of the content of soluble alkali in mortar was compared with the result of flame photometry. The calculation was in good agreement with the result of flame photometry.

Abstract: In this study, the effects of fiber types on the mechanical properties of lightweight aggregate concretes were investigated. Three types of fibers, namely, polypropylene fiber, steel fiber and water hyacinth (Eichhornia crassipes) fiber, and two types of lightweight aggregates, namely, expanded polystyrene and ceramsite were used. The compressive strength and splitting tensile strength of concretes were tested. The results show that both the compressive strength and the splitting tensile strength were improved by adding a reasonable volume of steel fiber and polypropylene fiber into LWAC. The addition of water hyacinth fiber had little effect on the compressive strength of LWAC, while a little increase was observed in the splitting tensile strength.

Abstract: The damage process of pure cement pastes with water to cementing material ratios of 0.30, 0.40, 0.50 and 0.60 and fly ash modified pastes with mass fraction of 10%, 30%, 40% and 55% were studied by using ammonium chloride solution with concentrations of 6 mol/l. The total leaching depth, leaching depth, porosity and compressive strength of these pastes leached for 14, 28, 56, 91 and 140 days were tested. The influences of W/C ratio and fly ash content on these properties were analyzed, the relationship between the two factors and the corrosion resistance of pastes was summarized. The results show that the total leaching depth of fly ash modified paste is larger than that of pure cement paste. However, the fly ash modified paste suffers various degree of lowered increment in porosity and strength loss (in percentage) in connection with the added content.