【正文】 craters on their surface and clear,small ones (approximately 10 um)with smooth surface. In the present work ,AFM was used to observe particle shape and surface texture details of cement silica fume,fly ashes ,and hydrated micrographs of 1um1um were taken ,providing information on the particle shape of the additions and microstructure of the hydrated same materials were examined under SEM to obtain a general overview,and the parative use of these two methods(SEMAFM) is ,the correlation between the microstructure and the macroscopical engineering and durability properties of cement products is discussed. procedure and sample preparationThree typical cementitious and/or pozzolanic additions were examined。a silica fume ,a lowcalcium fly ash,and a highcalcium fly silica fume (SF)originated from Norway(Elkem Materials A/S,Kristiansand )and is a typical highly pozzolanic lowCa fly ash (FL) was produced is Denmark (distributed by Danaske I/S,Aalborg)and is categorized as normal pozzolanic high –Ca fly ash (FH)was produced in Greece(Public Power Corporation,Ptolemais)and is a cementitious mineral ,the choice of these materials covers almost all the range of cementitiouspozzolanic byproducts used in and FL were used as they were delivered from the producers,whereas FH was pulverized prior to use,to meet the FL mean particle normal portland cement (350m2/g Blaine’s fineness) was used.The main physical properties and chemical analyses of the materials ,determined by Xray sedimentation technique,showed that the mean particle diameter of fly ashes was 13um,similar to the cement particles,as reported in the literature,are about 100 times smaller in size( average diameter).Four paste specimens were cast in small plastic pastes were made of normal portland cement(control),cement plus 10% silica fume,cement plus 20% lowcalcium fly ash ,and cement plus 20% highcalcium fly watertocement ratio(W/C)of was retained for all ,the cement amount (10g)was added and then the corresponding amount of the materials were mixed by hand for two min。then the corresponding amount(5g) of the water was added and the fresh paste was further mixed for 2 day after the casting,1ml of water was added to all containers were hermetically sealed and placed at 20℃ constant analyses were performed after six months. force microscopyMaterial particles and paste samples were examined by atomic force microscope(RasterscopeTM 4000,Danish Micro Engieering A/S)running in noncontact mode ( force).The particles in the cement ,silica fume,and fly ashes were dispersed by ultrasonic treatment。the silica fume in distilled water and the other ponents in acetone in order to avoid specimens were prepared by leaving one drop of the suspension to dry at room conditions on a block of highly oriented pyrolytic graphite(HOPG).The samples from te pastes were removed by hammer stroke from the paste specimens,ovendried at 105℃ for pieces of material were then glude onto AFM sample holders and slightly polished in dry specimens were examined at room conditions (～20℃,1atm and 4060% relative humidity). electron microscopy All of the above particles and pastes were also examined by means of scanning electron microscope(LEO 435 VP).Surface micrographs of 8,000 magnification size were obtained and can be used as a general overview of the materials. and discussion ,silica fume ,and fly ash particlesTypical SEM micrographs in Figs 25.As observed by SEM(),cement particles have and irregular polygonal sizes range from 15 to less than AFM (),some particles of size 1 to n diameter are rounded,with a globular surface,whereas others are ,some irregular particles of size less than in diameter were observed(,right). Silica fume particles are too small in size to be imaged in detail by SEM().From AFM(),the silica fume investigated has particle diameters of about ,in agreement with previous reported particle shapes are present,one spheroid and one is very characteristic of the material that all particles are posed of two plimentary parts(hemispheres or semicylinders).This feature can be explained from the production of silica fume,where the reduction of quartz to silicon at about 2000℃ produces a gaseous SiO,which is transported to lower temperatrues,where it is oxidized and condensed. This particular shape can help in SF identification in cement paste during the hydration process. In general,fly ashes consist of glassy spheres of various to the lower proportion of surface deposits consisting of alkali sulphate crystals,FL tends to show a cleaner appearance in SEM ().For the FH,many of the particles are plerospheres containing numerous smaller particles,but after grinding,smaller size particles are produced having an irregular shape like the cement particles ().Using AFM technique,it is observed ()that the FL consists primarily of large spheroid particles (approximately 3um)with a smooth surface,like found previously,and of smaller(in one dimension).These nanosize particles may be correlated with the early pozzolanic activity of the fly ashes. microstructure SEM micrographs for all mature pastes are summarized in the control sample,very large Ca(OH)2(CH)crystals and a porous posite mass of calcium silicate hydrate(CSH)and monosulphate are observed ().In the SFcement paste ,the CH has been pletely converted ,and a very dense structure of CSH and monosulphate has been formed ().Because of the significant pozzolanic reaction during the period of six months,the fly ash particles are difficult to identify ,as they are covered by the reaction products ( and d).Few entire round particles are still distinguished .Similarly ,for the fly ashcement mixtures,a very dense structure has been formed paring to the control.AFM micrographs for the corresponding pastes are shown in figs 710For the control paste,the roughness is