1、Project application of the high-performance concrete of fly ash Every performance of this text to high -performance concrete of fly ash has done detailed research, and to the concrete respectively to person who mix of fly ash Kinds of influence of performance and fly ash concrete some questions that
2、 should notice carry on analysis and discussion in not constructing. 1. Summary Fly ash, as a kind of industrial waste material, resources are abundant , cheap, and contain a large amount of active composition , it is modern concrete Central Africa A often important component part . The high-quality
3、 fly ash is applied to the concrete rationally , not only can replace the cement partly , save the fabrication cost of the project, And, its peculiar performance can be used in the codncrete of various kinds of instructions for use very effectively, improve the performance of the concrete, It is the
4、 ideal in the high-performance concrete that admixes the material . Among it is at concrete not modern, whose name is already with cement in fly ash, collect material , water , admixture and Kind is important, become a component part in concrete. Fly ash high-performance concrete re】 gard durability
5、 as main goal go on design mix Congeal the soil . It regards excellent durability (instead of the high strength) as the main characteristic , that is to say, concrete capital of any grade of intensity Can make into the high durability concrete . In order to reach high durability, the performance tha
6、t the fly ash concrete】 should possess is: Mixing the state newly well Work,namely, without emanating, secreting by water, so that shaping the even , closely knit by mobility, harden not shrinking subsiding early water and Water shrink light, warm to rise low, harden course is it dwindle to do, in o
7、rder to reach having the initial crack, the permeability after hardenning is low. 2 function and effect of the fly ash are fly ash material technology and application foundation of the project. Mix and add the powder of t he conicrete Coal ash, in conformity with understanding that the function of t
8、he fly ash is made overallly, by volcanic ash react and economic component part general to fly ash originally Read , expand technological consciousness of fly ash effect to , make fly ash function can serve performance of concrete improve with quality raising better. The role in concrete of fly ash
9、has the following several points: (1) . Shape effect: It is spongy vitreous body , little pearl of silicate glass of alu minium that the main mineral of the fly ash makes up , smooth the body surface of these spherical glass, the grain size is thin, the quality is pre-pressing, inside smaller than t
10、he surface area, the strength of absorbing to water is small, this line of physical characteristics, reduce concrete rub obstruction inside , favorable to improvement , concrete of mobility not merely； And, have reducing water function in various degree on the concrete； (2) . Active effect: The acti
11、ve composition SiO2 of the fly ash and water result of AI2O3 and cement react in a situation that there is water, producing water silicic acid calcium (C-S-H ) and water sour calcium (C-A-S-H ) of sulphur aluminium, these responses nearly all go on in the grout hole, water that produce result pack ,
12、 cut apart the heavy original hole , make the hole thinning, can reduce the hole rate within the concrete , change the hole structure , improve glueing the function of forming of concrete every component part ； (3) . Collect the materi al effect a little: Very small particle of fly ash even to is it
13、 among cement particle , pack the hole to distribute, play a role in getting to thinning hole , meanwhile , prevent glueing gathering each other of the cement particle, and make it in state of dispersing , help water of the mixture to react, the fly ash will not be totally with reacting with water r
14、esult of the cement, can keep its collecting the material effect a little for a long time ； (4) . Effect of the interface: It is the weak link in the concrete structure to collect the interface between the material and cement stone, width of transition area as water for dust than, collect there aren
15、t material , transition area have than grout body more, heavy hole. Mixing can reduce the regional width of the transition to add the fly ash , interfere Ca (OH ) orientation of 2 crystal in the transition area, improve the intensity of interface and density in the concrete. (5) Performance of the f
16、ly ash concrete The change of the fly ash to concrete performance can be divided into three stages: 1 . Mix concrete stage newly: Influence the coagulation time of the concrete , is improving and easy , change rheology nature , can improve pump ,etc.； (6) . The concrete stage while hardenning: Regu
17、late the course of hardenning, reduce the heat of hydration； 3 . The concrete stage after hardenning: Raise the intensity on later stage , raise every durability, such as anti-permeability, resist the sulphate corroding, suppress the alkali - Collect the material and react etc. 3.1 Intensity The fly
18、 ash has three kinds of influence on the intensity of concrete: Reduce water consumption , increase glued material content and reflect through the long-term volcanic ash that raises his intensity. The particle in the fly ash of low calcium is the silicon oxygen tetrahedron structure, ones own activa
19、tion is very low. In the final result of the cement, high alkaline water silicic acid calcium and crystallization of 2 colloid of Ca (OH ) are very low in intensity, especially Ca (OH) 2 ask vigorous to come 1-2% , stone of intensity only, but Ca (OH) 2 volume account for whole cement 25% , stone of
20、 volume. A large number of silicon , aluminium oxide that contain in the fly ash, can and high alkaline water silicic acid calcium 2 responses take place with Ca (OH ) 2 progressively, produce intensity than high low alkaline water silicic acid calcium , so , make cement stone water glue congeal qua
21、ntity of material increase, and make its quality improved by a large margin , is favorable to the improvement of the intensity of concrete. Meanwhile, to is it can disperse cement particle to mix fly ash, make cement to be ink sufficient, improve closely knit degree of the grout , make the intensity
22、 of the interfaces of the aggregate and grout in the concrete improve. Fly ash is it draw intensity compare with contribution of the bending strength compression strength to be heavy to confront with each other, this is useful to resisting the performance of splitting of concrete. The elastic mould
23、amount of the fly ash concrete is similar to compression strength, it is early and on the low side, improve progressively later stage , get 28d the constant basic concrete is raised by 5-10%. With to hold strength of wrapping up in reinforcing bar, 28d , fly ash of concrete is it form intensity the
24、same with ,etc. basic concrete of grade basically to glue, but homogeneity, fly ash of concrete fine, is it form intensity person who test getting dispersed and kind than basic concrete to glue. Water two times of the fly ash reacts and generally starts after the concrete builds 14d, when temperatur
25、e is low , will reflect necessary time is longer. If strict with early intensity of the concrete, the mixing amount of the fly ash is unsuitable to exceed 30%, winter construction large volume at the concrete, the mixing amount of the fly ash is unsuitable to exceed 20% non-. Because modern concrete
26、 China and foreign countries add use of pharmaceutical, on one hand, reducible concrete mix and stir water consumption, it reduce by dust water than,of not lasting concrete density of cement； On the other hand, water-reducing agent can make cement silicic acid calcium ink Ca (OH ) produced 2 increas
27、e, help fly ash and water two times of 2 of Ca (OH ) to reflect , excites the activation of the fly ash, this effectual for early intensity to improve fly ash, in addition use fly ash activation excite pharmaceutical or in large volume use strong cement early among the concrete non-, can compensate
28、mixing the impact on early intensity of concrete of fly ash too. 3.2 and easy Whether fly ash there are the following several points to concrete and getting easy improvement function. .The high-quality fly ash contains more than 70% of the spherical vitreous bodies, too smooth to have raised angle t
29、he body surface of these spherical glass, performance is steady, play a kind of lubricated function which is similar to the bearing in the pump sending , shaking the course of smashing of the concrete； .Mix particle apt to gather group cement in the concrete newly, to is it can disperse cement parti
30、cle effectively to mix fly ash, release more thick liquid body is it lubricate aggregate to come , help concrete work the improvement of performance ； .Mix fly ash can compensate detailed deficiency of bits in the detailed aggregate , cut off mortar base body secrete continuity , water of channel, t
31、he fly ash that at the same time quality is good can reduce the mixing water consumption of the concrete under the same consistency, make water dust of concrete than reduce light level to , is it secrete ink and emanate the phenomenon to reduce. 3.3 shrinking The shrink of the concrete relates to th
32、e fact that the mixing water consumption and thick liquid body body of the concrete are accumulated, the less water consumption is, shrink the smaller. High-quality fly ash water requirement than smaller than 100% , mix and stir reduction , water of quantity make mix fly ash concrete after the 28d s
33、ince dry to shrink and not dry to shrink little. Fly ash concrete is it is it mix with fly ash improvement of quantity reduce too to contract to do. But because water , fly ash of concrete reponse slowly, moisture evaporate fast, so between fly ash and to do epitome to be loud and very much heavy in
34、 early days concrete. For prevent early shrink , fly ash of concrete from fracture , should strengthen in early days raising to it 3.4 creeps Issue in the past will it be age one day, intensity of concrete relatively low, issue is it it meets an emergency to be heavy than ordinary concrete too to cr
35、eep corresponding age, but with ordinary concrete fly ash in one age one creep and was smaller than the ordinary concrete after this concrete of intensity. 3.5 carbonization performance Fly ash co ncrete resist carbonization to be performance relatively poor. Cement consumption , fly ash of concrete
36、 reduce, cement water Ca (OH ) 2 too corresponding to reduce quantity that appear, and volcanic ash is it consume Ca (OH ) 2 of a certain amount too to react, make hydrogen ion index of the concrete reduce, will increase the speed of carbonization of the concrete. Unless especially at water in early days, fly ash the low in degree in response in volcanic ash,fly ash- there is the loose in structure in hole in system cement, CO2 , O2 , moisture ,etc. invade obstruction small, so carbonization is relatively large in depth. With the growth of one and gradual
