Advanced Materials Research Vols. 194-196

Abstract: On the basis of the principle for the highest filling degree of cement hydrates, it is synthetically considered that a matching connection between hydration of cement, volume increment of solid phase and packing density of cement paste, a calculation method for a connection between cement continuous particle size distribution and strength of cement paste is developed and tested by experiment. Based on above-mentioned analysis, a tentative research on the effect of particle size distribution of cement on strength is carried out.

Abstract: Alkali aggregate reaction (AAR) is known leading to great damage in concrete, both in compressive strength and in durability. In this study, a backscattered scanning electron microscopy with energy dispersive spectroscopy is adopted to diagnose AAR reaction. The results show that the type of AAR reaction and reaction products can be easily identified and the method is precise and fast.

Abstract: The disposal and reuse of waste combustion residues has become a critical topic recently in view of the method of treating household wastes in a city, which has gradually changed to be incineration (major) and landfill (minor) in densely populated Taiwan, plus the difficulty of various wastes disposed by the Refuse Incineration Plant at Yilan County. To propose concrete recommendations as references for the local competent authorities’ policy for reuse of bottom ash, we researched and analyzed compositions of wastes and ingredients as well as leaching toxicity of bottom ash (accounting for 70% of waste combustion residues) which had been collected from the Li-Ze Incineration plant at Yilan, and transported bottom ash to a cement plant also at Yilan as an alternative material for Portland cement. The results in this study indicated quite a few products, with ingredients of bottom ash from an incineration plant, can be taken as principal compositions used in production of cement, and the capacity of bottom ash treated by the cement plant can be further expanded according to the quality of produced cement and bottom ash properly processed.

Abstract: Styrene-acrylic emulsion was selected to modify the cement mortar which was prepared as the crack mending material for the concrete pavement. The results indicated when the percentage of the styrene-acrylic emulsion was from 15% to 20%, the flexural strength and the bent bond strength increased by 39.00%~48.23% and 45.01%~49.60% respectively at 28 days, compared to the reference mortar. The morphology of the cement mortar modified with styrene-acrylic emulsion was observed by SEM. The modification mechanism of the styrene-acrylic emulsion to the mortar was discussed.

Abstract: The composite cementitious material was prepared with soda residue and fly ash. The mechanical properties were improved by mixing calcined lime and Portland cement, and the mechanism of admixture was researched. The results showed that the 28d flexural strength reached 3.59MPa and the 28d compressive strength reached 9.71MPa., when the proportion of soda residue and fly ash was 40:60 with 9% Portland cement and 7% calcined lime added.

Abstract: This paper made experimental research on the compressive strength, axis compressive strength and splitting tension strength of polypropylene fiber-reinforced concretes at a fiber content of 0.9Kg/m³ in different ages which showed that: in the experiment of compressive strength, the strengths of C20 polypropylene fiber concretes in the ages was lower; the strength of C30 polypropylene fiber concretes in the age of 7 days was lower, the strengths in the ages of 14 days and 28 days were basically equal to; the strength of C40 polypropylene fiber concretes in the age of 7 days was basically equal to and in 28 days was higher than the strengths of ordinary concretes. In the experiment of axis compressive strength, the strengths of C20 polypropylene fiber concretes in the ages were lower; the strengths of C30 polypropylene fiber concretes in the age of 7 days and 14 days were lower and in the age of 28 days was basically equal to; the strengths of C40 polypropylene fiber concretes in the ages were basically equal to the strengths of ordinary concretes. In the experiment of splitting tension strength, the strengths of C20 and C30 polypropylene fiber concretes were lower; the strength of C40 polypropylene fiber concretes in the age of 28 days was basically equal to the strengths of ordinary concretes. Conclusion: the relationships between the strength of fiber concretes and ordinary concretes are correlated to the strength grades of concretes, namely, When the strength degrade of concretes is low, the strength of polypropylene fiber concretes is lower, but the strength reaches closer to or exceeds the strength of ordinary concretes along with the increase of the strength grade of concretes.

Abstract: In the ternary system of hydroxy carboxylate (HC), sulfonation-polyol (SP) and carboxylic-vinyl copolymer (PC), HC and SP preferentially adsorb on the surface of particles to shield the initial hydration. In this way, the ternary system has excellent dispersibility and holding dispersibility, and it has little effect on later hydration. By means of the chemical shrinkage, SEM and XRD analysis, the hydration mechanism of the hydroxy carboxylate (HC) and sulfonation-polyol (SP) has been discussed and the preferential adsorption model (PAM) has been established. The results show that HC delays the initial hydration of C₃S and accelerates both the hydration of C₃A and the formation of AFt; HC reduces the strength for 28 d with the addition of 0.2%; SP delays initial hydration of C₃S and C₃A; the ability of shielding hydration becomes weaker along with cement hydrating and the development of strength is normal. In the ternary system of HC, SP and PC, HC and SP with the electrostatic attraction of -SO₃- and COO^- and complexation of OH^- preferentially adsorb on the surface of particles and active hydrating points. Then, reaction of active hydrating points was shielded and the growth of the hydration products slows. In this way, hydration of C₃A and C₃S are delayed, and the holding dispersibility of PC becomes better. The PC preferentially adsorbs on inert hydrating points and consumes slowly to provide dispersibility with steric hindrance. Along with hydrating going on, organic compounds are enwrapped by hydration products and the shielding ability becomes weaker and weaker. Then, the hydration becomes normal.

Abstract: In this paper, The GDS unsaturated soil triaxial apparatus are employed for experimental tests to obtain the main characteristics of the drying paths for compacted clay. In order to study the soil water characteristic curve and shrinkage coefficient under deferent net mean stress. The results show that shrinkage index and the soil-water characteristic curve are dependent on net mean stress. At a given matric suction, with the increase of net mean stress, the void ratio and water content of soil sample is decrease, but the degree of saturation is increased.

Abstract: By using of shrinkage curve, the empirical relationship between the degree of saturation and the void ratio on drying path was established for four types of soils including sand, silt, clay and soft clay. It was indicated that during the process of drying, the soil samples continuously shrunk with the decrease of saturation degree. For test samples of sand and silt, the curve of saturation degree and void ratio is flat; For test samples of clay and silt clay, however, the shrinkage of the soil samples was almost fulfilled when the degree of the saturation of soil samples decreased to 90% and the void ratio of the soil samples almost kept unchanged while the degree saturation of soil was reduced to 70%.

Abstract: The water-cement ratio and cement content are key factors which reflect the anti-penetration of the concrete. To study the slag cement concrete against sulfate attack, make two types of the slag cement concrete test blocks of which one type has the same concrete content and different water-cement ratio, while the other type has the same water-cement ratio and different concrete contents; then test the concrete test blocks on compressive strength, folding strength and weight changing after dipping them into sulfate solution and drying them for thirty and sixty times .At the same time non-damage ultrasonic test was carried out. The results show the durability of the slag cement concrete is improved with the decrease of water-cement ratio; in concrete design, there is optimum cement content which theslagcement concrete has the best resistance sulfate erosion.