DE1484125A1 - Reinforced concrete material and method of its manufacture - Google Patents

Description

DR. W. SCHALK · DIPL.-INC. PETER WlRTH DIPL.-ING.C. E.M.DANNENBERG DR.V.SCHMIED-KOWARZIK

Da / rk ί "" ΞΓ '-'. " \ -> ^J December 11, 1963

The Battelle Development Corporation Columbus, Ohio, USA

Reinforced concrete material and method of its manufacture

The invention relates to a method for the production of reinforced concrete, in particular to a two-phase material, with short pieces of reinforcing wire embedded in the concrete are, which have a certain critical distance from each other, as well as a method for producing this Materials.

The low breaking strength of concrete has been around for many years known and accepted as an inevitable fact to be considered when using concrete. Until now In attempts to remedy this lack of breaking strength in concrete, either (a) steel bars were used for reinforcement or (b) the concrete has been prestressed. With none of these processes, however, could the due to the low breaking strength difficulties caused are really overcome;

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they were simply bypassed. It is therefore a mark of conventionally reinforced concrete that cracks occur in stress zones that expand further. These cracks form with relatively little stress and then continue to spread until they are exposed Reach an area or a pressurized zone.

In addition, you can not rely on the building for construction work Known test methods determined breaking strength for conventionally reinforced concrete or pure concrete leave, since the formation of just beginning Rio. α en as a result of fatigue, thermal shocks or cavities reduce the breaking strength deodorant concrete significantly reduced. It has therefore long been expected that about half of what is normally reinforced Concrete carrier material used cannot serve as a resilient surface. The adverse effect of these cracks in reinforced concrete girders is not limited to the loss of resilient area. For example, it can be seen that Cracks caused by stresses severely impair the usefulness of concrete containers for holding liquids. The use of reinforced concrete for hydraulic structures is also made considerably more difficult, as salt water is used for reinforcement The steel used, which is exposed through the cracks, exerts a corrosive effect.

The invention therefore relates to the manufacture of a two-phase material of concrete and reinforcement steel wires, whose The breaking strength is about two to three times greater than that of the conventionally reinforced concrete. 909806 / 06S7

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The invention further relates to a two-phase material made of concrete and reinforcing steel wires, which extends through a is characterized by considerable resistance to the progression of stress cracks. The two-phase material from Concrete and steel wires should also have the properties of a homogeneous material and an extensive change in shape enable without signs of disintegration.

The invention also relates to a resilient and flexible two-phase material made of concrete and steel wires, the has a greater ability to absorb energy than conventional reinforced concrete.

The two-phase material of the present invention also has the ability to prevent fatigue cracks from forming and spreading to withstand repeated tension forces.

Finally, a material according to the invention is also essential more resistant to temperature stresses caused by sudden temperature changes.

The invention further relates to a method for producing a two-phase material with the properties described above.

Further features and properties of the invention result from the exemplary description below in conjunction with the drawing mouths; in these shows:

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Fig. 1 (a) shows an embodiment of the invention

Concrete material and Fig. 1 (b) a concrete beam * of another material according to the invention;

Fig. 2 is a comparative graphical representation of the

Breaking strength of materials according to the invention and those of conventional materials;

Fig. 3 is a graphical representation of the dependency of

Properties of the material according to the invention from the wire spacing, and

Fig. 4 is a graphical representation of the actual,

Stress causing bite formation as a function of the wire spacing in materials according to the invention.

In general, the invention relates to a method for producing a two-phase material from concrete and reinforcing steel wires, which are distributed in the concrete in such a way that the average distance between the wires is no more than 12.7 mm (0.5 inches), and preferably less than about 7.6 mm (0.3 inches). According to the method according to the invention is the material produced by a certain Share of short pieces of wire mixed directly with cement, sand, water and coarse aggregate. The coarse aggregate may consist of pieces with the greatest extension over 7.6 mm and even over 12.7 mm, but the mixture should be proportioned in this way

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. be that the average spacing of the wires in the slurry of sand, cement, and water that makes up the spaces fills in the coarse aggregate, is not larger than 12.7 mm and preferably smaller than 7.6 mm.

In Fig. La and Ib are two schematic embodiments shown. Fig. La shows a cross section through a tensioned concrete beam 10 in which short reinforcing wires 12 are included. In Fig. Ib a similar concrete beam 10 is shown with reinforcement elements 14, which are parallel are arranged to one another, tfei the second embodiment the material is made by placing long continuous wires or wire mesh into the molds and then into them a very flowable mixture of sand and cement is poured.

Several Voltage tests carried out on two-phase materials made of concrete and short pieces of steel wire. The measurement of the tension forces was carried out in accordance with the method for indirect Tension test for brittle materials, in one Article by N.B. Mitchell Jr. entitled "Tension Test for Concrete" in "Material Eesearch and Standards," October

to 1961, pages 780-788. In this test, ° the specimen has the shape of a cylinder, which is at two diamtrically σ>

^ opposite edges are pressurized. The value

ro

o> This procedure is based on the fact that the stress in the Sighting perpendicular to the application of the pressure occurs as a train

and along the diameter of the specimen, which is along the Load line runs, is constant. The size of the stress is a function of the size of the specimen and the total loading. Table I below gives one Overview of the conditions and results of these investigations.

- Table I -

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TABLE I.

Cylinder ratio ratio age reinforcement average tensile stress p 'No. Water- sand- (days) length percentage lightening (kg / cm) breakage resp. Cement cement (mm) distance crack formation crack

(mm) (start)

28.7 76.3 84.7 66.1

1 1: 2.67 1: 2.00 12th - - - - - __ 28.7 2 1: 2.67 1: 2.00 12th 28 ,8th 3 , 16 1 , 65 64.7 3 1: 4.00 1: 2.15 21 18th , 9 2 “70 1 , 77 72.4 4th 1: 2.67 1: 2.00 9 25th , 4 1 , 91 2 , 10 61.9

NOTE: All cylinders 98.4 mm in diameter

All wires size 34 (diameter = 0.26 mm)

OO O CT)

- σ -

These findings show a significant encryption \ improvement in tensile strength for reinforced with closely spaced short wire pieces concrete. The unreinforced concrete broke under the expected stress, namely at 28.7 kg / cm. The specimens with short, closely spaced pieces of wire withstood loads more than double. In addition, the wire-reinforced material did not show any of the disintegration phenomena that normally occur in conventionally reinforced concrete under stresses after the formation of cracks, but deformed like a homogeneous plastic material, with the cracks only widening slightly.

Further attempts were made with wire grids in order to also illustrate this embodiment of the method according to the invention.

The wires used for this consisted of highly polished steel of great strength. The wire sizes and properties are listed below:

LARGE AND CHARACTERISTICS OF THE STEEL WIRES

Wire diameter yield point breaking strength elasticity (mm) (kg / cm2) (kg / cm2) modul

16 1.58 6440 7280 28 χ 10 ⁶ 20 0.88 7700 10290 32 χ 10 ⁶

The wire reinforcement was, with two exceptions, which will be added later

are described, processed into a grid to the

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Ease of installation in the molds. Details of these wire mesh are given below:

DHAHTGITTBRDIMENSIONBN

Wire size Lattice designation Distance of the wires from

Center to center (mm)

16 2x2 12.7

16 3x3 8.5

20 6x6 4.2

The wire mesh was made so that the wires are straight in one direction and bends in the other was. In each case the straight wires were parallel to the longitudinal axis of the beam.

In all cases the concrete was made from slag cement, the mixtures were thin to allow pouring through the Lattice to facilitate; a densifying agent was also used to retard setting and shrinkage to decrease. The only aggregate used was good quality sand. The ratio of water to cement was 0.45 and that from sand to cement 2.50. Printing cylinders were created from all mixtures.

19 carriers were manufactured and tested. The straps were 7.6 cm wide, 12.7 cm high and 198 cm long. The clear span at the test was 183 om, and the carriers were on

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at the third points. This created a section between the loading points pure bending stress.

Two girders were reinforced with two 6.6 mm thick, round, deformed bars for building purposes, and layers were made in 15 girders cast in wire mesh.

The grid inlay for the molds was made by arranging grid strips on top of each other and using short pieces of wire, which were soldered to the individual layers, were kept at a distance from each other. This created a three-dimensional one Grille that was easy to handle. These grids were placed in the wooden molds. The two wire-reinforced girders were made in the same way, but here the wires were passed through templates at the end of the molds and attached after tightening. In the case of these girders, the grille was only used in the end sections for reinforcement against shear forces intended.

The carriers were tested until they were destroyed; the values for deflection, deformation (strain) and load were thereby measured at short intervals. Table II contains the most important information about each carrier and gives an overview

■ slose.?

the bending moments at break. The dimensional ratio M / f ^ bd was also calculated, where

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M = breaking moment

f β compressive strength of the concrete

Id = beam width

d = depth of the transverse center of gravity of the girder.

The wire-armored girders broke suddenly, the only prior warning being a slight crack. The effectiveness dejr transverse curved wires of the grid stands however in embossing. Because these wires are not welded together they could not have contributed to the connection between the grid and the reinforced concrete. However, to confirm this, two girders (No. 18 and No. 19 in Table II) were only provided with a reinforcement of smooth wires, which in exact Distances from each other in the longitudinal direction of the carrier were arranged.

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TABLE II INFORMATION ABOUT THE CARRIERS AND MEASURES

sample
No.
! Reinforcement Steel surface
cw ρ distance seruc- * »-__-»,
Law kg / cm ² kg / cm ² d
cm M.
υ! 0.2 ι / Y
mm scale
Law well . * ■ ο ι ϊ 'bd ² ! • j ' 1 ; 2 - # 3. ' ι, α 1.47 j well ___ ·, s inOO i 2800 500.5 11.8 O, S2 —-. ! 2: 3x3 ι, α ι 1.47 j __, 12.7 uooo 6440 539.0 8.2 O. 104 10.4 ^: 3 6x6 ι ι, α ι 1.47, 8.3 6 ^ 3, «ISOOÖ; 7700 539.0 8.2 0.256 5.0 4th 2x2 ί 1.54 1.60 4.0 6.3 at ii2 j 6440 530.0 8.5 0.341 O ₁ ** Q, 4 5 2x2 0.70! 0.73 12.7 12.7 3 * o ** 6440 483.0 8.7 0.228 O, Z 4 12.7 6th 2x2 : 1.41 1.47 12.7 4,8 'itiol 644Ο 483.0 9.6 0.132 o _v te 8.6 7th 3x3 0.70 0.73 12.7 25.4 3S661 644Ο 483.0 7.9 0.227 I. 16.8 8th 6x6 0.70 0.73 8.3 15.7 moot 7700 483.0 8.7 . 0.153 o, IS 0.9 9 3x3 1.41 1.47 4.3 4.8; WISH 7700 483.0 9.9 O, 172 0.5+ 6.6 ■ 10 2 - # 3 ι, α 1.47 8.3 50 1 ^ L 2800 413.0 11.8 : 0.246 - ! 11 3x3 ι, α 1.47 6.3 "1 * 644Ο 413.0 10.1 0.114 7.3 ί 12 6x6 ι, α 1.47 8.3 4.8 ΐίίίί 7700 α3, ο 10.0 i 0.254 4.5 '13 2x2 0.83 0.87 4.3 13.7 '- ^ t - »* 644Ο 395.5 8.4 .0.310 O 60 13.2 • 14 6x6 1.41 1.47 12.7 4.0 ι% · + - <ϊ \ Oy 7700 395.5 9.8 • 0.155 o _v co 4.1 i 15 3x3 ι, α 1.47 4.3 10.4 i e ° i € C ^ 644Ο 395.5 8.8 j 0.290 Oil o, 3 16 3x3 ι, α 1.47 8.3 10.9 j 5 HiOO 6440 395.5 8.5 ι 0.250 0.50 α, 6 I 17 6x6 1.41 1.47 8.3 4.0 j e »> 53 7700 "395.5 9.6 ! 0.250 0.65 4.1 I IF ^ smooth ")
ίWires J.
A. ι, α 1.47 4.3 3.1 j S5153 644Ο 463.4 ^Q , 5 ι 0.290 8.1 k 1.41 1.47 8.3 4,3 '/ ti «S" »6 7700 437.5 0.8 0,? 70 ! 4.3 4.3 0.380

^M u ^f y ^f c d

I _

Breaking load moment

Steel yield point

Concrete ultimate strength

Depth from the top of the beam to the center of the beam ( steel; j

Average vertical and horizontal distance aer Pewehruf

The test results given in Table II clearly show the greater breaking strength of those with dense wire mesh reinforced girders compared to the conventionally reinforced concrete girders. This can also be seen from FIG. 2, in which the dimensional relationship M / f'bd as a function of the

u c

ratio p / p _{u is} shown. In this representation, ρ stands for the percentage of reinforcement and p _u corresponds to 0.4f / f. The test results, in a representation according to FIG. 2, show the greater strength of the carriers produced in accordance with the invention, but this representation shows the significance of the distance between the wires from one another

t ρ not apparent. However, if the ratio i ^ / f bd as Function of the average distance between the wires is shown, the meaning of this distance becomes apparent. This is the case in FIG. 3. In the representations (e.g. in Fig. 2) the solid lines stand for the breaking strength conventional concrete beam, as it is based on the empirical equation

M / f'bd ² = 0.40-1- (1.0-0.236 JL}. ^P u P _u

can be calculated (see the report of the joint committee the ASOE-AGI for ultimate strength determination, "Proc. American Society of Civil Engineers "Volume 81, Report No. 809, October 1955). An average yield strength of

101,000 psi (7070 kg / cm) is assumed as the yield point of the Grids between about 92,000 psi and 110,000 psi (6440 and

7700 kg / cm) varied. The graph of FIG. 3

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shows a clear relationship between the breaking strength and the spacing of the reinforcement. A noticeable increase in strength is seen at a distance of about 0.5 in. (12.7 mm), which becomes more pronounced at 0.3 in. (7 »6 mm) · At an average of 0.2 in. (5th) »0 mm) the increase in strength is about 50 percent, and the values indicate that an increase of 100 per time can be expected when the average distance is only 0.1 inches (2.5 mm).

No attempts were made to compete in these exams precisely locate and measure cracks that occur. However, upon careful observation with the naked eye, it could be seen that hairline cracks appeared in the wire-reinforced girders quite late. Besides, the cracks were wide apart and their appearance was on the lower part of the tension zone limited, not penetrating to the area of the neutral axis, except in the event of an imminent rupture.

The test results of FIGS. 2 and 3 are given as the bending moment at break which increases as the tensile strength of the concrete increases. Further attempts were made on several Carriers made a direct measurement of tensile cracking strength. The carriers were covered with short, evenly distributed pieces of wire reinforced. The results of these investigations are shown in FIG. 4 and represent the tensile strength of closely spaced pieces of wire

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■ reinforced concrete of those mixed at the same time compared to pure concrete. The clear influence of the wire spacing on the breaking strength is readily apparent.

In addition, repeated stress tests were carried out with concrete samples, which were carried out with pieces of wire close to each other or continuous Wires were reinforced at a short distance. The distances for breaking loads under tensile loading were in the order of magnitude of about 900 psi (63 kg / cm). The specimens withstood up to 10 million repetitions of the load

p "

with loads of up to 800 pai (56 kg / cm) without formation or crack propagation.

The materials according to the invention can be broken down into the following Characterize properties:

a) A tensile strength (initial cracking under load) of at least about 1000 psi (70 kg / cm) versus about 350 450 psi (24.5 to 31.5 kg / cm ² ) for conventionally reinforced concrete;

b) Tensile strengths that are inversely related to the square root the reinforcement spacing increases when the spacing be less than about 0.5 inches (12.7 mm);

c) increased resistance to the formation and spread of lakes under repeated exposure to

Tensile stresses;

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d) greater resistance to splintering of the Surface and cracking when exposed to sudden heat;

e) the ability to · even after the occurrence of stress cracks remain usable;

f) the properties of homogeneous materials that instead of Brittleness of the conventionally reinforced concrete enables extensive plastic deformation before disintegration, and

g) Compliance and flexibility with greater energy absorption capacity than conventionally reinforced Concrete.

The advantages of the invention are numerous; they can be summarized as follows:

1) Concrete girders reinforced in accordance with the invention have a Bending strength at break, which is twice as great as that of a conventionally reinforced beam of the same size and same amount of steel. Cracks only appear when much higher tensile forces are reached, and such cracks only arise the size of hairline cracks and do not expand over time.

2) The method and material according to the invention make a reinforcement to be arranged and shaped by hand unnecessary.

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The problem of arranging the usual steel reinforcement in de? The direction of the main tensile stress is omitted.

3) The materials according to the invention are almost homogeneous and isotropic. They are flexible and can be more deformed before cracks occur than conventionally reinforced concrete.

4) Adaptability without limitation of use by the arrangement of the reinforcing steel.

Materials made by the process of the invention can be used for many purposes. These include, for example, motorways or Pernstraßen, where the higher breaking strength has a Concrete savings of around 10 to 20 percent are made possible, and shrinkage cracks can be removed, which extends the service life of the surface especially in those areas that are exposed to Prost and Tau. Another possible use can be found in the heavily used runways on plug areas, the thickness of which is reduced with the help of the materials according to the invention and in which the chipping of the surface is prevented. Among other things, the materials can be used for example wise also for shell roof constructions, prefabricated building elements,

Sewage and irrigation pipes, railway sleepers, sidewalks,

^ Building foundations and solid foundation ceilings are used.

or> They are also suitable for buildings on the coast and in

■ ^ harbors, since then the elimination of the propagation of cracks is a Will avoid corrosion of the reinforcing steel by salt water.

Claims (10)

Claims ! 1t two-phase material of concrete and reinforcement steel wire s which are as Ln distributed learning concrete, that the average distance between them is not _(? 0 5 inches) is more than 12.7 mm, 2. Material according to claim 1, characterized in that the Darren average distance between wires less than is approximately 7.6 mm (0.3 inches). i). Material according to Claim 1 or P _1, characterized in that short pieces of wire are randomly distributed in the concrete in such a way that their double-cut distance is no more than 12.7 mm, preferably less than about 7.6 mm. 4. Material according to one of claims 1-3 »marked ρ by a breaking strength of at least 70 kg / ~ m (1000 psi). 5. Material according to any one of claims 1-4, characterized in that continuous reinforcement wires in the concrete are arranged whose average distance is less than 12.7 mm, preferably less than about 7.6 mm, - Claim 6 909806/0667 6. Material according to claim 5, characterized in that the continuous wires are arranged in the form of a grid. 7. A method for producing a material according to one of the Claims 1-6, characterized in that a reinforcing steel mixture is produced and this has such an amount of reinforcement seams it is admitted that the average distance between these wires is not more than 12.7 mm. 8. The method according to claim 7 »characterized in that the wires added to the concrete mix consist of short pieces of wire that are randomly distributed in the concrete 9. The method according to claim 7, characterized in that the long, continuous wires added to the concrete mix There are wires that are no more than 12.7 mm apart be arranged remotely 10. The method according to claim 9, characterized in that the long, continuous wires in the form of a grid in the concrete mixture be introduced. Patent attorney CX--