Key Engineering Materials Vols. 302-303

Abstract: A series of polycarboxylate-type water-reducers (MPCs) had been developed and tested. Through molecular design, macromers of polyethylene glycol unsaturated carboxylic esters, and other derivative of unsaturated vinyl monomer containing the carboxylic groups，sulphonic groups， graft groups of alkyleneglycol was introduced as the chemical structure unit of MPCs. The copolymers MPC-2 contained long and short PEO chains and ionic groups, possessed a high dispersing and good slump retaining behavior. Therefore, MPCs can be used as high range water-reducers to prepare high-flowing concrete, high-strength high performance concrete and high-durability concrete.

Abstract: This paper investigates the effects of vitreous slag powders on the rheological properties of fresh concrete. It was observed that the fluidity of concrete increased noticeably, and the plastic viscosity decreased when vitreous powders were substituted partially for cement. It was demonstrated in the experiments that the fluidity effect of vitreous powders on fresh concrete can be correlated with the vitreous content of the powders.

Abstract: To investigate the strength efficiency of fly ash in concrete, the contribution of fly ash to strength, k value was calculated with the equation: the strength difference between fly ash concrete and control concrete with no fly ash due to the different fly ash content divides by the strength difference between both control concrete with no fly ash due to the different cement content which equals to the former different fly ash content. The k values were organized with fly ash specific surface area, concrete curing condition and age of specimens. Based on a large number of data collected from several proceedings and journals published in Japan during 1981 to 2003, the influences of fly ash property, mixture proportion and curing condition on k value were investigated. Within the range of study the following observations were made: (1) When fly ash concrete kept in moist curing, the k value of fly ash with specific surface area from 250 to 500 m2/kg is averagely 0.5 to 0.6 or higher at an age of 91 days and later, whereas that of fly ash with specific surface area from 150 to 250 m2/kg is around 0.4 to 0.5, and with some cases contributing little to the strength. (2) In the range of a portland cement content of 250 to 450 kg/m3, the strength contribution tends to increase as the cement content increases. (3) The contributions of fly ash to strength at 91 and 364 days are 1.44 to 1.97 times as large as those at 28 days, respectively, by standard curing, but conversely decrease to 0.75 to 0.79 times those at 28 days by air curing.

Abstract: Ultrafine slag, which is ground with the process of vertical mill, is tested with the laser granulometric distribution apparatus quickly. The characteristics of granulometric distribution of ultrafine slag are analyzed using fractal theory. The fractal dimension of different fineness powders is tested and counted. The result shows that ultrafine slag powders have self-similar characteristics. With the laser granulometric distribution apparatus, the fractal dimension of its powders might be tested and counted with the fractal theory and its characteristics might be fast evaluated. The inherent law between powders fineness and activity is studied, and the mathematical model is built with the results. The fractal characteristics of powders might be used to meticulously evaluate fineness of ultrafine powders and be used to describe complexity of powders. The test of activation indicates that the slag fineness appraised by fractal dimension has fine linear relevant characteristic with its 7 d, 28 d activity.

Abstract: This paper deals with the effect of mineral admixtures and Geopolymer on preventing excessive expansion due to alkali-silica reaction (ASR). The test method used was ASTM C 441-97. Expansions of mortar-bars were measured at 14, 56, 90 days. The results prove that mineral admixtures can effectively restrain ASR. When three kinds of mineral admixtures, silica fume, fly ash, and ground granulated blast-furnace slag (GGBS), were used together, they bring about a compound effect which is more effective to restrain ASR. Mortar expansion can be reduced 81.9 % by this compound effect. Chemical analysis of the pore solution shows that mineral admixtures reduced concentrations of hydroxyl, potassium and sodium ion, so that damages from ASR decreases. Geopolymer, an amorphous inorganic material, was prepared with metakaolin and other mineral admixtures in the condition of high pH. Alkalis fixed in the framework of Geopolymer, there are no enough alkalis to react with active aggregates. Geopolymer does not generate any dangerous alkali-silica reaction even with alkali contents as high as 12.1 %.

Abstract: To solve existing problem of cement concrete pavement destruction in China, the cement-based highway repair materials with Ultra-fine Fly Ash (UFA)—Fluoro gypsum as the main ingredients, which are all industrial wastes, are researched by employing UFA for both water-reducing and strength-enhancing. The mutual motivating effect of Fluoro gypsum and UFA during cement hydration is also explored. According to data analysis of experimental results, UFA-Fluoro gypsum high-performance highway repair materials are optimized, and then applied to production of highway rapid repair concrete where mechanical properties and partial long-term properties of the concrete are measured. The results indicate that the 1-day concrete strength closes to or reaches 30MPa, which meets the requirements of highway rapid repair project. The long time performance of concrete is also favorable. Finally, its hydration mechanism is analyzed preliminarily.

Abstract: Aerated concrete is a new type of building materials. Clayish crushed stones are regarded as solid waste disposals in China. This paper reports the research outcomes of an experimental study on using clayish crushed stone for the production of aerated concretes of B05 and B06 grade. Hydro-thermal synthesis reaction, mixing proportions, gas-forming and their influences on the concrete performance are investigated. Proper mixing proportions and some important technical parameters are proposed for material design. The microstructure of aerated concrete made with clayish crush stone is analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the hydration products of clayish aerated concrete are composed of poor crystallized C-S-H (B), blade- and needle-shaped Tobermorite and a small amount of granular Hydrogarnet. A homogeneous and densified microstructure was obtained in the aerated concretes with negligible amount of clay after the hydro-thermal reaction in the mixture.

Abstract: The magnesium phosphosilicate cement (MPSC) is a novel inorganic binder, it sets quickly and has very high strength. Also, it is a promising material for the sustainable development. In the present study, the durability of MPSC were investigated, including deicer scaling resistance under freezing-thawing cycles, chemical corrosion resistance in sodium sulfate and magnesium sulfate solutions, and wet-dry resistance in fresh and natural sea water. For comparison, Portland cement samples were also prepared for parallel tests. Test results showed that the chemical durability of MPSC is superior that of Portland cement. The causes of the high performance may be attributed to the low water demand and a reasonable microstructure of hardened paste matrix.