CN1240413A - Heavy duty concrete with improved ductility - Google Patents

Abstract

The present invention relates to heavy duty concrete with improved ductility and containing inorganic fibers. The aim of the invention is to substantially enhance ductility of said concrete by adding only a small amount of inorganic fibers. According to the invention, this is achieved by providing the heavy duty concrete with almost 30-200 kg/m<3> of inorganic fibers which are known to increase flexion tensile strength in concrete, and 1-10kg/m<3> of organic fibers with a low elasticity modulus.

Description

Has the strong concrete that improves ductility

The feature of the strong concrete that employing concrete additive and additional material are made is to have very high intensity.Use by flow promotor can reach identical workability at the proportional range of very low water-cement (W/Z).The adding of particulate filler mainly is to use the by product silicon dioxide microparticle in the ferro-silicon manufacturing to finely tune concrete structure here.This particulate filler can produce three kinds of effects, promptly all is that crucial effect is played in the raising of concrete strength.

The firstth, can fill up the hole between the cement granules by the small grain size (d=0.1 μ m) of silicon dioxide microparticle, thereby reach structure to close purpose.Next is the hydrate (CSH) that forms Calucium Silicate powder by the pozzuolana of silicon dioxide microparticle and calcium hydroxide (CH) reaction, and it has the effect that improves intensity equally.The calcium of zone of action between matrix and the additive and the content of ettringite have been reduced in addition.These bonded improve the tomography that causes known strong concrete and form, and it is different with the concrete of regular tenacity, and this tomography is to run through imbibition by adding particle.Can occur less coarse surface of fracture like this, the interlock of crack edge also greatly reduces.

Because the uniformity coefficient of the matrix of cement block according to the rules is greatly improved, the formation of microcrack only just forms under the situation of higher load.The concrete of common intensity demonstrates the linear elasticity state when center pressure load reaches about 40-60% of ultimate compression strength, strong concrete then reaches about 90% o'clock of ultimate compression strength at pressure load and also keeps linear stress-strain behavior.The tiny crack that occurs will develop along with the increasing of upsetting force with superproportional rate of rise, owing to be in high elastic energy state, so can unexpected structural failure occur in moment, the critical upset pressure degree that is reached will be starkly lower than the numerical value of normal concrete.

According to current state of the art, the method that tackles the problems referred to above is to strengthen hoop.Can prevent that crackle from spreading apart towards periphery or in hoop, form the triaxial pressure state with this horizontal reinforcement configuration to improve its ductility.Draw by compression member test to central concentrated load, in the tangible raising of the deformability of the step-down branch road part of stress-strain curves just at the hoop that must surpass 2 volume % under the square supporting condition or must just can achieve the goal above under the hoop of 3 volume % under the circular support condition.In order to stop concrete cover sudden failure to occur owing to cracking or oblique crackle (forming a kind of partial en-block construction displacement) then to occur, so laterally reinforcement degree is at least 6 volume %.Add under the intensity situation at this height, concrete uses very inconvenient, and peeling off still of concrete upper layer can not be avoided fully.

According to the present art, can see also that in the literature (for example DE-OS 2,314 352) add fiber, particularly steel wire in concrete, to improve the bending and tensile strength of strong concrete.

From above-mentioned experience, done overtesting, improve its performance by in brittle strong concrete, adding the steel wire that improves bending and tensile strength.But test is pointed out, add 10 volume % or more obvious raisings that just can reach in high-strength concrete compression member ductility to.Add many like this fibre weights and must adopt special method, this economically or building operation all do not have benefit.

Also see (DE 195 10 338 AI) in the literature, in strong concrete, be added with organic fiber to improve the performance of concrete in fire.

The purpose of this invention is to provide a kind of strong concrete, only added a spot of inorganic fibre, and its ductility and the contrast of common strong concrete improve significantly.

The present invention is that the strong concrete of the principle that proposes according to claim 1 solves to this purpose.

Being worth surprised is, with the well-known inorganic fibre (steel fiber that adds in order to improve concrete bending and tensile strength, carbon fibre, glass fibre) combines with the organic fibre that adds by the quantitative range that proposes in the claim 1 and can improve the ductility of strong concrete for certain.By adding the curve after this fibre blend can record hypotensive point with the similar stress-strain line of the concrete of regular tenacity, do not have to find because the adding of fibre blend and reduce the phenomenon of intensity significantly.

Add the strong concrete behind the fiber fracture behaviour can by increasing of forming of crackle and superproportional jolt ramming compressive strain be estimated.Because constantly increasing, the jolt ramming compressive strain make material reduce its supporting capacity.This process is stable having under the control distortion loading, unexpected structural failure can not occur.Its critical jolt ramming presses load corresponding with the concrete of regular tenacity.

The collapse of concrete under stress seen to be combined by two kinds of phenomenons from mechanical angle and caused, and is that the crackle of breaking property occurs on the one hand, is partial monolithic structures displacement on the other hand.The breaking property crackle impels member upset compressive strain scope to increase, and structural part is died down, up to partial monoblock crackle member displacement occurring so that construction system lost efficacy.

The effect of two kinds of fibers can following simulation test be described:

Owing to compare with concrete matrix, the modulus of elasticity of organic fibre is very little, so this fiber works at the subsurface defect place.The dispersion that they have accelerated the microcrack of dissipation of energy around forms.The inorganic fibre that exists in the material then plays the effect with these microcracks " stitching ", and it constantly and stably broadens these crackles in continuing loading.The increase of crackle width will constantly reduce the rigidity of system.The friction of the microdefect flank of tooth that the upper state of strength range is produced by organic fibre on the one hand, the crackle suturing by inorganic fibre scatter on the other hand.This has not just been avoided the volatile inefficacy of strong concrete member, can in time estimate the inefficacy of compression member by the formation of tiny crack, and enough deformabilities are arranged to avoid excess load, in load larrying member, load might be added on the member of enough carrying reserve capacities thus.

From appended claims, also can draw other superior embodiments of the present invention.

Decapacitation of the present invention improves beyond the ductility, also has an important advantage, promptly, can in concrete mixing process, add, thereby be that with the existing known method difference of technology it can be undertaken by typical building operation because the shared deal of fibre blend is smaller.This just has an enormous advantage on expense and can make vertical vertical component for example building slab or both bonded building slabs of pillar and water.Can only the manufacture level building slab such as cover plate and so on according to currently known methods.

The also available following center applied voltage test of the present invention is further described, and appended stress-strain curve is:

The situation that Fig. 1 is added with steel wire and does not add the strong concrete of steel wire.

The situation that Fig. 2 is added with polypropylene fibre and adds the high-strength concrete of polypropylene fibre.

Fig. 3 adds the situation of steel fiber and polypropylene fibre mixture in strong concrete according to a kind of embodiment of the present invention.

The test that Fig. 1 did is to add steel wire in the mixing process of strong concrete B105, and deal is 120kg/m ³, be equivalent to 1.5 volume %.Used steel wire is the steel wire of the general supply in market, and promptly about 15-60mm is long, diameter 0.15-1mm.Stress-strain curve shown in Fig. 1 is that (solid line of band hollow square) after not adding the strong concrete (solid line) of any accessory fibers material and adding above-mentioned steel wire compares.The result points out that by adding steel wire, the capacity for work of concrete B105 obviously improves.But the stress-strain curves of strong concrete near normal concrete, therefore forecasts that with crackle the purpose of the failure behaviour of similar ductility does not but reach qualitatively.

The test-results of representing among Fig. 2 is to add 2kg/m in the batch mixing process of strong concrete B105 ³(0.2 volume %) polypropylene fibre.The length of plastic optical fibre is about 20mm and diameter is about 100 μ m.

As can be seen from Figure 2, behind the interpolation polypropylene fibre, concrete workmanship's ability improves little (solid line of band closed square).But the curve behind the stress-strain curve hypotensive point reaches about 40% of ultimate compression strength at load becomes more smooth later.

Add the Fig. 1 and 2 contrasts of the test-results of steel wire and polypropylene fibre respectively from expression, the conclusion that should draw is (120kg/m when adding the mixture of these two kinds of fibers ³Steel wire and 2kg/m ³Polypropylene fibre), the stress-strain curve position that obtains should be between above-mentioned two kinds of curves, but the result very can not be satisfactory.Being worth surprised is that the result draws the synergy of representing as Fig. 3 as shown in Figure 3 after adding above-mentioned fibre blend.Express the stress-strain curve of normal concrete B45 (dotted line) among the figure, not with the high-strength concrete B105 (solid line) of interpolation fiber and the stress-strain curve of the high-strength concrete B105 (with leg-of-mutton solid line) behind the interpolation fibre blend.These tests point out that the interpolation of steel wire and polypropylene fibre combination can produce and eliminate fragility later stage fracture behaviour in strong concrete.Can rupture by many separation crackle advance notices, and progress is stably.The stress-strain curve of " fibre blend " is equivalent to the concrete of regular tenacity under higher load.It reaches similar critical jolt ramming and presses.

Claims (7)

1. the strong concrete that improves ductility that has that contains inorganic fibre is characterized in that in order to strengthen concrete bending and tensile strength, it contains the 30-200kg/m that has an appointment ³Known inorganic fibre and about 1-10kg/m ³The organic fibre that very little modulus of elasticity is arranged.

2. the strong concrete in the claim 1 is characterized in that inorganic fibre is a kind of steel wire.

3. the strong concrete in the claim 2 is characterized in that it contains 120kg/m ³Steel wire.

4. the strong concrete in the claim 2 or 3, the length that it is characterized in that steel wire is about 15-60mm and diameter is about 0.15-1mm.

5. the strong concrete in one of aforesaid right requirement is characterized in that this organic fibre is a polypropylene fibre.

6. the strong concrete in the claim 5 is characterized in that containing the 2kg/m that has an appointment ³Polypropylene fibre.

7. the strong concrete in the claim 5 or 6, the length that it is characterized in that polypropylene fibre is about 50-525 μ m for about 5-20mm and diameter.

Images