Zong Hui Zhou

Influence of Slag and Fly Ash on the Self-Healing Ability of Concrete

The influence of slag and fly ash on the self-healing ability of concrete was researched by strength measurement and SEM analysis. The self-healing ratio was measured by the increase of compressive strength before and after self-healing. The optimal mixing amount of slag and fly ash were determined, and the reasonable sand ratio was obtained. Analyzing results show that the self-healing ability of concrete was the strongest when the mixing content of slag and fly ash were 30% and 40% respectively. The appropriate sand ratio was also obtained, when the sand ratio is 33%, the self-healing ability of concrete is the strongest.

Preparation and Properties of Concrete Containing Iron Tailings/Manufactured Sand as Fine Aggregate

High performance concrete was prepared by using iron tailings mixed with manufactured sand. Effects of the content of iron tailings on the performance of concrete were studied. The results show that the slump of concrete containing iron tailings is equal to concrete with river sand when the content of iron tailings is 60%. With the increase of the content of iron tailings, compressive strength of concrete shows a trend of decrease at same age; meanwhile drying shrinkage decreases and is less than the concrete prepared river sand. After 200 times of freeze-thaw cycle, mass loss of concrete with mixed sand is less than 5% and compressive strength loss is less than 25% which are close to concrete with river sand.

Effects of CaF2 on the Formation Kinetics of Portland Cement Clinker

Through testing the amount of the free lime and the Loss ignition, the clinker formation rate, the reaction-rate constant (K) and the activation energy (Ea) were calculated according to the Gentling equation and Arrhenius equation. The effects of CaF2 on the formation kinetics of Portland cement clinker were investigated by analyzing the K and Ea. X-ray diffraction (XRD) and scanning electron Microscope (SEM) were used to characterize the phase composition and the morphology of the resulting samples. The results show that the silicate minerals formation is promoted when a proper amount of CaF2 is doped into the raw meal. The K increased from 0.7450 ×10-5s-1 to 7.1588 ×10-5s-1 and the Ea decreased from 386 kJ/mol to 122 kJ/mol when the amount of CaF2 increased from 0.0% to 2.0% in mass. However, the results were reversed at the amount of CaF2 exceeding 2%.

Exploration on Feasibility of Preparing Cement Clinker with Artificial Aggregate Concrete

Combining with the utilization of waste, an new idea of using the waste to prepare high-strength artificial aggregates was put forward in this paper. The concrete was also prepared by using these aggregates. The demolished concrete could be recovered and used as cement raw meal to produce new cement clinker. In this study, the feasibility of making cement clinker with this kind of demolished concrete was studied. The concrete aggregates composed of steel slag, blast furnace slag, coal gangue and fly ash were prepared. The concrete was prepared using these aggregates with the water-cement ratio of 0.45, 0.50 and 0.55 respectively. The compressive strength of the concrete in 28 days is 52.8MPa, 46.4.2MPa and 42.6MPa, respectively, higher than that of ordinary concrete. In accordance with the ratio of cement raw meal, the cement clinker is produced by adding appropriate limestone, clay and other correction materials. After hydrated for 3 days, 7 days and 28 days, the cement paste compressive strength is 47.1 MPa, 59.8 MPa, 75.6 MPa, respectively, which reach the requirements of ordinary 42.5 Portland cement.

Influence of Cement Coarse Particle on the Self-Healing Ability of Concrete Based on Ultrasonic Method

The influences of particle size and mixing content of coarse cement on the self-healing ability of concrete were researched by ultrasonic method. Damaged degree was measured through the decrease of ultrasonic head wave amplitude (UHA) before and after loading. The relationship between damaged degree and self-healing ratio of concrete was built based on the experimental results as well as the relationship between cement diameter and self-healing ratio of concrete. Analyzing results show that UHA can evaluate the damaged degree of concrete clearly. There exists a damaged threshold of the concrete during loading. Under the same mixing content of coarse cement, when the damaged degree is higher than the threshold, the self-healing ratio of concrete decreases with the increase of damaged degree and increases with the increase of coarse cement diameter, however, while the damaged degree is less than the threshold, the self-healing ratio of concrete increases with both the increase of damaged degree and coarse cement diameter.

Prodution of Concrete Aggregates with High Strength by Using the Wastes

Several series of concrete aggregates with different content of steel slag, blast furnace slag, coal gangue and fly ash were prepared. The reasonable ratio of raw materials and process parameters to prepare the aggregates were determined by measuring the water absorption, crush indicators and apparent density of the aggregates. The mineral composition and morphology of the aggregates were analyzed by XRD, SEM and EDS. The results showed the aggregate with about 30% steel slag, 50% slag, 20% gangue, and calcined at 1300°C for 90 minutes had the best performance. The water absorption of the aggregate is about 1.55% which is lower than that of the natural aggregates (about 2.2% on average). Both the crushing index (about 11.39%) and the apparent density (2672 kg/m3) of the aggregate meet the requirements of national standards.

Existence Forms of Magnesium Oxide in Steel Slag by Chemical Phase Separation

Magnesium oxide solid dissolved in silicate phase, mesophase and RO-phase which are the major constituents of steel slag. The MgO exists in the steel slag with complex forms, which results in the bad soundness of the steel slag. In this paper, the silicate phase and mesophase were separated by salicylic acid methanol solution and potassium hydroxide-sucrose solution respectively and were studied combining with the XRD and SEM. The results show that the silicate phase and mesophase can be fully dissolved, however, the RO phase is not influenced by the two solutions in this process. The content of magnesium oxide existed in different minerals can be detected by chemical analysis. It can be found that the magnesium oxide mainly exists as RO-phase in steel slag, and some of them exist as free state, while only a small quantity of solid dissolve in the silicate phase and mesophase.

Effects of Sol Viscosity on Properties of BST Thin Films Prepared by Sol-Gel Method

A series of BST(Ba0.65Sr0.35TiO3) sol with different viscosity were prepared by using Ba(CH3COOH)2, Sr(CH3COOH)2 and Ti(OC4H9)4 as raw materials. The BST thin films were fabricated by sol-gel method and spin-coating process on Si(100) substrates. The effect of sol viscosity on crystallization, microstructure and dielectric properties of BST thin films were analyzed by using X-ray diffractometry, scanning electron microscopy and impedance phase analyzer. The results show that the BST films coated by sol with viscosity of 3.0cp and annealed at 750°C for 1h are basically non-crystalline. The crystallization degree increases with the increase of sol viscosity at the same annealing temperature. The ABO3 perovskite structure is formed when the sol viscosity increases to 3.5cp. With further increasing sol viscosity to 6.0cp, the crystal grains of the film grow well and range very compact, the surface become smooth, and the films have optimal dielectric properties.