Steel fibre concrete is it shut material by cement , water , thickness aggregate , steel fibre and mix the chemical admixture or mix and add the pharmaceutical in case of necessity to mix, compounded it in certain proportion, mixed and shut the correct choice that the material each made up the material , the physics mechanics performance and constructing to the steel fibre concrete has important influence.

First, shear the main performance of the section steel fibre

1, Tensile strength

In order to make the steel fibre concrete have good mechanics performance , require the steel fibre to have certain tensile strength. The tensile strength of the steel fibre is different from production technology according to the material of the steel fibre, its tensile strength is distinguished to some extent too. The tensile strength of shearing the section steel fibre is generally 38000MPa.

2, Glue the intensity of forming

Glueing the intensity of forming of steel fibre, but according to glueing the intensity of forming by drawing the law and determining between the steel fibre and cement mortar directly of " steel fibre concrete test method standard " (CECS13 : 89 ).

Because the destruction of the steel fibre concrete is mainly the pulling out and appearing but breaks of steel fibre, so the enhancement of the steel fibre depends on glueing the intensity of forming of the steel fibre concrete base body interface mainly. Improve and glue the intensity of forming besides relating to performance of the base body , as to steel fibre itself, should come to improve glueing the performance of forming of it and base body from the surface and form of the steel fibre . In order to improve glueing the intensity of forming of the steel fibre, often adopt: Make steel to be fibre surface coarse to take , being irregular in shape , section increase with contact area and frictional force , base of body; Pigeonhole mark steel fibre surface , keep wave form , increase machinery glue the strength of marrying; Make both ends dysmorphism , steel of fibre , make both ends the crotch or the major part shape wait for, by improving his firm strength of anchor and resisting the strength of capturing.

The test indicates , the special-shaped steel fibre can be improved by about one time than the enhancement result of the steel fibre of straight shape .

3, Hardness

The hardness of surface of different steel fibres is relatively high, when mix with the concrete, seldom discount alikly incident and curved. Steel fibre should be able to stand along steel excellent to bend 90 constant for 3mm diameter.

4, Able to bear corrosivity

Build the steel fibre within the steel fibre concrete, so long as it is closely knit to make firm by ramming or tamping, isolated with the air, the corrosion phenomenon seldom takes place in the steel fibre. Reveal on concrete surface or when the width of crack exceeds 0.25mm , is it connect in steel fibre , crack of office to step, incident to corrode the phenomenon.

Second , the geometry parameter of the steel fibre and volume rate

Show by the geometry parameters steel have steel the fibre lengths , diameter (diameter not equivalent ) and foot-path not long of than.

The fibre length of steel refers to the straight line distance between two extreme points of steel fibre, express with Lf, its size is 150mm .

Steel fibre sectional diameter or equivalent diameter (when for being non- with round section steel fibre, the diameter which Institute of Computing Technology receives when its section is accumulated and equivalent to the area with round section), show with df it is usually 0.3.2mm.

The long foot-path of the steel fibre compares with the diameter or equivalent diameter more than the length of refering to the steel fibre promptly, namely Lf/ df, is usually 3000.

The rate of volume of steel fibre, point the percentage of the volume of fibre concrete of steel that the steel fibre accounts for . Say with pf it indicate steel fibre in is it shut material mix amount of quantity to mix.

Third, the steel fibre concrete structure , to the steel fibre geometry parameter and exertion range of the volume rate

Compared with fibre length of steel, the diameter (equivalent diameter ) and long foot-path the enhancement result of the steel fibre is relevant. Steel fibre strengthen function with long foot-path than increase and raise. Steel fibre length too short to play a strengthening role, too long to construct relatively difficult, influence quality of mixture, the diameter is careful and is bent in the course of mixing and shutting, it is thick in the same volume rate to pass, it is relatively bad that it strengthens the result.

Experimental study and project practice indicate , the length of the steel fibre is 150mm , the diameter or the equivalent diameter is 0.3.2mm, the long foot-path is selected for use than on the range of 3000, it strengthens the result and construction performance and meets the demands. If beyond the scope of the aforesaid, through testing it when it can meet the demands to strengthen the result and construction performance, can adopt according to the need . According to the application experience of the domestic and international project, to different classifications steel fibre concrete structure, put forward commonly used steel fibre geometry parameter select range for use , rank on 1-1 form.

The volume rate of the steel fibre is too little to play a strengthening role until a certain degree in the steel fibre concrete, it is for variety not different, the different to be long foot-path than steel fibre,volume not minimum of it the getting more different slightly in rate, generally regard 0.5% as the minimum volume rate both at home and abroad. The rate of volume of steel fibre exceeds 2% o'clock, the mixture one is and easy to become bad, it is relatively difficult to construct, quality is difficult to guarantee . But in the special requirement, through testing and taking the essential construction measure, in case of ensuring the quality of products and strengthening the result, can increase the rate of volume of steel fibre .

According to the domestic and international project and application experience, different steel fibre concrete structure projects, the daily volume rate selects the range for use and arranges in form 1-2. To the demand for strengthening the result according to the performance , structure of the steel fibre while selecting for use, and the principle of economy and rationality is selected. When the performance of the steel fibre is better or the structure demands to be lower in strengthening , can select low value for use , to strengthen expect much or steel fibre performance than available high value when being poor structure.

1-1-2 The cement cement is a kind of cementing material in the steel fibre concrete, mix and form the grout with water jointly, having very high glueing the strength of forming, it becomes gluedly a whole of the sand , stone and steel fibre, harden through condensing, have steel fibre concrete of certain intensity. So the cement is a important composition material of the steel fibre concrete.

The commonly used cement is 425 and ordinary portland cement No. 525 in the steel fibre concrete at present. Steel fibre concrete consumption consumption heavy than ordinary cement cement have, 36050kg/m3 generally.

1-1-3 sand call detailed aggregate often, is it pack broken stone or gravel thick space of aggregate and make up steel skeleton , fibre of concrete together to use for.

The thickness degree of the sand is expressed with the detailed degree of moduluses of the sand. Detailed degrees of modulus of sand to steel fibre concrete with have a certain influence while being getting easy intensity, the same thick sand of quantity compared with fine sand, thick sand relatively little than the surface area, therefore in guarantee when steel fibre concrete intensity the same , thick cement that sand need consumption little than fine sand. Obviously, when cement consumption is the same, with thick steel fibre concrete intensity that sand compound being than intensity high with steel fibre concrete that fine sand compound. In addition is it shut as steel fibre concrete material and when being getting easy and the same , fine sand concrete is it equal to material to be more in water requirement to mix to mix, but if with pass thick sand is it make easy to is it emanate and secrete ink phenomenon to produce to mix; If mix and make the careful sand, although does not produce emanating and secrete water phenomenon , need more grout to wrap up the surface of the sand, cement consumption is great. For this reason, detailed degrees of modulus of sand moderate, compound steel sand thick sand of should spending , fibre of concrete.

Grade of the sand mixes and should fulfil requirements . The density of the sand is generally 2.5.7g/cm3.

1-1-4 building stones broken stone or gravel are the skeleton material which make up the steel fibre concrete, often call the thick aggregate. Building stones that the steel fibre concrete uses, usually select the broken stone for use. Because drops of material of broken stone surface relatively coarse, rich raised angle, can produce good machinery inlay the function of locking, have stronger glueing the strength of forming with the grout. So, it is high than with the intensity of fibre concrete of steel that the gravel compounds with the broken stone under the same condition , but need more grout.

Steel fibre building stones grains of foot-path that concrete spend, unsuitable to greater than 2/3 , steel of fibre length, it is generally 50mm, the largest foot-paths are unsuitable to be greater than 20mm, if a foot-path of building stones is too big, have weakened the enhancement function of the steel fibre, and apt to concentrate on big building stones, inconvenient scattering to the steel fibre.

Grade of building stones mix and should fulfil requirements , otherwise will influence mobility of the steel fibre concrete mixture and cement consumption .

Water can be drunking of 1-1-5 water and clean natural water, are used in the steel fibre concrete, because the sea water has corrosion function on the steel fibre, seldom allow to mix and make steel fibre concrete with the sea water.

1-1-6 admixture while the steel fibre concrete is mixed and shut, for is it shut material and getting easy and reducing cement consumption or raising the intensity to mix to improve, can mix the admixture of a certain amount .

Admixture divide into water-reducing agent , pilot a ship into harbour pharmaceutical , antifreeze , expand pharmaceutical , is it congeal pharmaceutical ,etc. to urge according to result of use. Use more one to be the water-reducing agent in the steel fibre concrete (ordinary water-reducing agent and high-efficient water-reducing agent), in order to improve it and easy.

The item that should notice while using the admixture is:

1)According to the purpose of using , choose the variety , and relatively confirm according to technological economy.

2)Add person who mix should according to variety used , and according to instructions for use , execution conditions, mix such factors as the raw materials shut ,etc. and fix by the test. The mixing amount is expressed with percentage of cement weight.

3)The mixing amount should be mixed for the admixture (such as the high-efficient water-reducing agent ) under 1% with the aqueous solution.

4)Pay attention to the adaptability of the admixture and cement.

5)The performance of the admixture should accord with the regulation that " the concrete admixture uses the rules " of the current standard .