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In 2004, the Canadian Centre for Mineral and Energy Technology (CANMET), in association with the American Concrete Institute, the Electric Power Research Institute, Palo Alto, CA, UWM Center for By-Products Utilization, Milwaukee, WI, and several other organizations in Canada, sponsored the Eighth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete. The conference was held in Las Vegas, Nevada, U.S.A., May 23-29, 2004. The proceedings of the conference containing 56 refereed papers from more than 20 countries were published as ACI Symposiuml Publication SP-221. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP221

The objective of this research is to study the compressive strength of mortar due to pozzolanic reaction of fly ash with different particle sizes. Fly ash and river sand which were ground to have median particle sizes of 19.4, 13.8, 6.3 pm and 20.6, 11.7, 6.4 µm, were used to replace portland cement type I at the rate of 10, 20, 30, and 40% by weight of cementitious materials to cast mortar. The pozzolanic reaction, without packing effect, of fly ash mortar is obtained from the difference of compressive strength between ground fly ash mortar and ground river sand mortar which have approximately the same particle size (19.4 and 20.6 pm, 13.8 and 11.7 µm, 6.3 and 6.4 µm) and the same replacement. The results showed that the pozzolanic reaction of fly ash mortar in-creases with the increase of fly ash fineness, age of mortar, and percent replacement of fly ash. Ground fly ash with particle sizes between 6.3 to 19.4 µm have slight packing effect on compressive strength of mortar. At early ages, the contribution to compressive strength of fly ash mortar due to pozzolanic reaction is slight, but it significantly in-creases at later ages. With 40% replacement of 6.3 pm particle size of fly ash, the compressive strength of mortar due to pozzolanic reaction at the age of 90-day is more than 50% of the total compressive strength of mortar.

Alkali activation of fly ashes is a chemical process through which the glassy structure of the material is transformed into a very well compacted cement. In general terms a variety of natural materials and industrial by-products rich in S'02 and Al2O3 may be activated with certain alkaline compounds to produce cementitious systems when cured under mild temperature conditions. The activation process may be considered as a set of destruction-condensation re-actions that initially lead to a series of unstable structure units and later produces the formation of tixotropic coagulation structures, which can condense to form the hydrated products. This paper describes a micro-structural study of a number of alkali activated fly ash matrices. MAS-NMR results has shown that the main reaction product in the activation of fly ashes is an amorphous aluminosilicate gel having a 3-dimensional structure in which the Si evolves in a variety of environments with a predominance of Q4(3Al) units when curing time is short, and Q4(2Al) units when curing time is long. Aluminium is essentially tetrahedrally co-ordinated. Microanalysis has provided additional information on the Si/AI ratio of the mentioned aluminosilicate gels too.

High fluidity concrete needs appropriate amount of powder for preventing concrete segregation. But slump flow often decreases because of the properties of powder. It is important to investigate qualities of the powder influencing rheological properties of concrete. So, the purpose of this study is to investigate an evaluation index for segregation resistance and the qualities of powder relating to the index. Firstly, the evaluation indices for segregation resistance were examined. And the best proposed as the ratio between coarse aggregate weight in concrete contained in the lower part of cylindrical vessel and that in upper part after tamping by a steel rod. This index more accurately ex-pressed the segregation potential under construction. Plastic viscosity of mortar and volumetric percentage of coarse aggregate in concrete mainly influence the index. Next, we investigated the influence of fly ash, Blast-furnace slag powder, limestone powder, crushed stone powder and recycled concrete powder on properties of a mortar. If the surface of powder was rough, the mortar flow with the powder largely decreased with in-creasing plastic viscosity when quantity of the powder was increased.

Studies on the viability of high calcium fly ash from coal combustion are being conducted in our laboratory to produce a new kind of low-energy cement. The process presents important environmental advantages, such as a reduction of CO2 emission compared to that produced by the conventional technology of portland cement manufacture. Furthermore, the processing temperature is also considerably reduced. The low-energy cement shows potential for good hydraulic activity for application in construction. The changes of fly ash composition were followed by X-Ray Diffraction (XRD), FT Infrared (FTIR) spectroscopy and BET surface area analysis.