WO2020005183A2

WO2020005183A2 - Concrete reinforcement member

Info

Publication number: WO2020005183A2
Application number: PCT/TR2019/050239
Authority: WO
Inventors: Ilhan IZMIT; Ugur ALPARSLAN
Original assignee: Kordsa Teknik Tekstil A.S.
Priority date: 2018-06-25
Filing date: 2019-04-12
Publication date: 2020-01-02
Also published as: WO2020005183A3

Abstract

The present invention is a reinforcing member manufactured from synthetic fibers suitable for reinforcing concrete comprises synthetic nylon 6.6 fibers coated with polycarboxylic ether on which no surface treatment is applied and comprising a plurality of filaments wherein the diameter of each one is in range of 20-40 microns, and which are combined such that the linear density will be in range of 140-330 tex. By means of using the reinforcement member of the present invention in the concrete, ductility is provided to the plain concrete, brittle braking is transformed into ductile breaking, and thus deflection ability under load after first crack is provided. Polycarboxylic ether coated Nylon 6.6 three dimensionally distributed in concrete increases the durability of the concrete by minimizing both the plastic and drying shrinkage that may occur in the concrete. The said application provides advantage before the existing applications in terms of labor and cost.

Description

CONCRETE REINFORCEMENT MEMBER

Technical Field

The present invention relates to a reinforcement member which is suitable for reinforcing concrete and comprises synthetic fiber.

Background of the Invention

Concrete, which is a construction material that is commonly used in the construction sector, is widely preferred due to its easy formability, having wide application area and pressure resistance. However, in addition to these advantages, the concrete has disadvantages such as being brittle, not being flexible, homogeneous and linear, and thus having very low tensile strength. Due to the aforementioned reasons, it is common practice in the art to place steel rods in tensile regions so that the concrete can meet the stresses in the said regions. However, although the tensile strength of the concrete structure is increased by the use of steel rods as reinforced concrete fittings, due to the fact that steel is a heavy material, application difficulties are experienced and the steel rods that are applied being corroded in time due to the micro cracks occurring on the concrete cause technical problems in the said application in long term.

In the state of the art, there are various concrete reinforcement applications developed in order to overcome the abovementioned disadvantages. One of the said applications is to use synthetic fibers instead of steel rods. Reinforcing concrete with macro synthetic fibers is a preferred application since the said materials are lightweight relative to steel and they do not corrode. The fibers used in the said applications are generally acrylic, aramid, carbon, nylon, polyester, polypropylene and polyethylene based. Even though, in the state of the art, studies performed about the load bearing capacities of the fibers come to the fore, it will not be sufficient to focus only on the bearing capacities. The behavior of fresh concrete has importance in terms of both transferability and being able to giving the desired shape. This situation which is explained with the term processability is negatively affected by increasing the dosage of synthetic fibers used in order to increase the performance; as the amount of fiber increases, the processability of the concrete decreases and it tends to agglomerate as structure.

An example of the fibers used in the prior art for reinforcing concrete is disclosed US Patent document no US2001/051266A1. In the said document, applications on polypropylene based fibers are disclosed. However, the chemical structure of the fibers disclosed in the said document does not involve functional groups that will bond with the concrete; the compatibility of the disclosed fibers is provided completely with mechanical forces. For this reason, it is necessary to apply surface treatments such as embossing, crimping and waving.

US Patent document no WO2012174414A2 discloses an application in which polyolefin fibers are used as structural fittings. Due to the polyolefins being hydrophobic, not having reactive ends on its surface, and thus not being able to form chemical bond with the concrete, the strength should be increased in the said application by means of applying embossing or waving on the said fibers. In case the surface strength is not increased as stated, the fibers are peeled off after the first crack in the concrete.

Summary of the Invention

The present invention relates to a reinforcement member which is suitable for reinforcing concrete and manufactured from plasticizer coated synthetic fibers. The said plasticizer used in the present invention is a super-plasticizer. Reinforcing member which is developed with the present invention, manufactured from synthetic fibers suitable for reinforcing concrete comprises synthetic nylon 6.6 fibers coated with plasticizer and comprising a plurality of filaments wherein the diameter of each one is in range of 20-40 microns, and which are combined such that the linear density will be in range of 140-330 tex.

The reinforcing member developed with the present invention is used in concrete, it can be used instead of steel fittings which are conventionally used, as well as it can be used together with steel as hybrid by decreasing the amount of the said steel fittings within the concrete.

In usage of plasticizer coated nylon 6.6 multifilament fibers for load bearing in concrete, the negative effect of fiber amount experienced in applications known in the state of the art on processability of the concrete is decreased by means of the present invention (for example up to 25%).

Summary of the Invention

The objective of the present invention is to provide a reinforcing member which is suitable to be used in concrete and comprises synthetic fiber.

Another objective of the present invention is to provide a reinforcing member which is suitable to be used in concrete, does not require surface treatment and comprises synthetic fiber.

A further objective of the present invention is to provide a reinforcing member which increases the residual strength value, momentum capacity and tensile strength of the concrete. Yet another objective of the present invention is to provide a reinforcing member in which momentum carrying capacity used for service limit state calculation is increased.

Another objective of the present invention is to provide a reinforcing member which makes the concrete safer by limiting the crack width that will occur in the concrete during its service period, thereby increasing the durability of the concrete (change in strength occurring over time).

Description of the Figures

The results of the experiments carried out on the concrete on which the reinforcing member of the present invention is applied and on a reference concrete which does not comprise any reinforcing member are shown in the graph illustrated in FIG. 1, in which:

Figure 1 is a comparative graph of EN 14651 load-crack mouth acquired as a result of the experiment 1 and the experiment 2 on a concrete in which the reinforcement member of the invention is used at a ratio of 4 kg/m³ and on a simple (reference) concrete.

Description of the Invention

Since the tensile strength of the concrete, which is a widely used construction material in construction sector, is quite low, it is common practice in the art to place steel rods in the tensile regions of the concrete. However, due to the fact that the steel is a heavy material, the application difficulties are experienced and the fact that the steel rods oxidize in time due to the micro cracks occurring on the concrete, the said application causes technical problems in the long term. In applications for increasing the tensile strength of the concrete by means of synthetic fibers as structural fittings, the compatibility of the said fibers is completely provided with mechanical forces, and therefore surface treatments such as embossing, crimping and corrugations or a coating should be applied on the said fibers. In addition, the processability of concrete is adversely affected by increasing the dosage of synthetic fibers; as the amount of fiber increases, the processability of concrete decreases and it tends to structurally agglomerate.

A reinforcing member manufactured from synthetic fibers suitable to be used for reinforcing concrete is developed with the present invention; wherein the said reinforcing member is manufactured from nylon 6.6 fibers on which no surface treatment is applied, the filament diameter of which is in range of 20-40 microns and which are coated with plasticizer material combined such that the linear density will be in range of 140-330 tex (unit for linear density). The said plasticizer is preferably super-plasticizer.

Plasticizers and superplasticizers are used to reduce the amount of water required to produce concrete in a certain consistency, to provide the necessary fluidization and to decrease the water/cement ratio. Plasticizers are formulated from modified lignosulfonates and hydroxycarboxylic acids. Lignosulfonates may be derived from fermented wood, for example spruce.

Superplasticizers are generally classified in the categories of sulfonated melamine-formaldehyde (SMF) condensates and sulfonated naphthalene- formaldehyde (SNF) condensates; and they comprise modified lignosulfonates; acid amide/polysaccharide mixtures and other high molecular weight hydroxylated polymers and copolymers.

SMF and SNF superplasticizers function by electrostatic repulsion, which causes rapid dissolution of cement particles; this situation increases the mobility of the cement paste, which does not require additional water for a significant increase in the processability of concrete. When the concrete is compressed, extra gaps are formed with the air entrained therein Since the superplasticizers reduce the gaps formed by air by means of increasing the mobility of the cement paste, coating the fiber material used to reinforce the concrete with the said superplasticizer material prevents the formation of extra gaps around the reinforcing fibers and provides solution to the problem of gap formation during the generation of concrete resistance.

In the present invention, preferably the superplasticizers are polycarboxylate polymers. In particular, they are polyacrylate copolymers and derivatives thereof, (co)-polymerized acrylic acid and/or maleic acid or derivatives thereof. According to a more preferred embodiment, the said copolymerized units comprise a poly ether side chain such as polyethylene oxide.

In a preferred embodiment of the invention, the said reinforcing member is applied inside the concrete with a usage ratio of 1,5-12 kg/m³.

In another preferred embodiment of the invention, the thickness of the plasticizing coating on the said nylon 6.6 fibers is 0.3mm-0.5mm.

The coating on the reinforcing member of the present invention can be carried out by the heat treatment, dipping, spraying or impregnation methods. In a preferred embodiment of the invention, the plasticizer is coated on nylon 6,6 by heat treatment; in this embodiment, plasticizer prepared as the aqueous solution is suspended in a metal container while the nylon 6,6 fibers are passed through this solution in order to allow said fibers to absorb said solution, then to be cured by passing through a furnace. When the plasticizer coated nylon 6.6 filaments used as reinforcing member with a filament diameter in range of 20-40 microns are combined together such that they will have a linear density value of 140-330 tex, the equivalent diameter of the multifilament structure formed by said filaments will be over 0.3 mm. For this reason, the structure which is formed is considered as macro-synthetic fiber.

Nylon 6,6 fibers can be coated with solutions containing plasticizers at different concentrations. These concentrations may be solutions having solid content in range of 5% and 70%. The values obtained by crushing the samples, in which fibers coated with chemical solution at 2 different concentrations (5%-l5%) with 4 kg/m³ dosage are used, are shown in Table 1. It is seen that both fibers carry a load even in the case of being coated at different concentrations. In addition to this, with the increase in the concentration of the coating solution, it is seen that the mechanical performance of the concrete is improved as well as the improvement of the processability of concrete.

Table - 1

In using Nylon 6.6 multifilament fibers coated with plasticizer in concrete for the purpose of load bearing, unlike the applications known in the state of the art, no surface treatment is required on the said reinforcement member.

In EN 14889-2 (fiber for concrete) standard, it is stated that it should meet frl = 1.5 N / mm2, fr4 = 1.0 N / mm2 values for the use of fibers as reinforcement in concrete frl is the residual strength value in the crack width of 0.5 mm and the service limit state is used for moment calculation in structural systems. Fr4 is the residual strength value in the crack width of 3.5 mm and the bearing capacity limit state is used for moment calculation in structural systems.

Comparative experiments have been carried out on concrete in which the reinforcing member developed with the present invention is added and a reference concrete in which no reinforcing member is added, and in these said experiments frl (bending stress occurring in 0.5 mm crack mouth) and fr4 (bending stress occurring in 3.5 mm crack mouth) values of both concretes are compared. The values for the concrete to which the reinforcing member according to the invention is added and the reference concrete compared in the said experiment are presented in Table - 2.

Table - 2 As shown in Table 2, the reinforcement member of the present invention, which comprises a 54 mm polycarboxylic ether coated nylon 6.6 fiber, is applied into the said sample concrete at a ratio of 4 kg/m³ in experiment 1. Plain concrete is used in experiment 2. For each experiment, 2 samples are used and the experiment is repeated in the specified number.

The water/cement ratio for the produced concrete is 0.40-0.65, and aggregate sieve analysis and material information are shown in Table-3, Table-4 and Table- 5. The amounts in Table 3 show the quantities passing through the sieve in Aggregate sieve analysis. The material referred to in Table 4 as“CEM I 42,5 R” is a type of cement with a minimum strength of 42.5 MPa in 28^th day. Table 5 shows the amounts used for the production of 1 m³ of concrete; the first three lines from the percentages in the third column contain the ratio of aggregates to the total aggregate and constitute a total value of 100%. The ratio for the plasticizer indicated in the fourth line indicates the ratio of the said plasticizer to the total amount of cement.

Table - 4

Table - 5

The aggregates used in concrete production have been designed to have maximum aggregate 16-20 mm in compliance with EN 1766-2000 standard.

The structural properties of the Nylon 6.6 synthetic fibers used in the reinforcement member of the present invention are given in table 6.

The diameter calculation of the samples cut using 140 and 210 tex is given in Table 7.

Table - 7

The dimensions of the sample concrete beams produced according to the specifications indicated in Table 1-7 are 15*15*60 cm. Three point beam bending experiment has been applied on the said samples, and the support range is 50 cm.

In experiment 1, the values of the concrete beam in which the reinforcing member of the invention (polycarboxylic ether coated Nylon) is used in ratio of 4 kg/m³ have been determined and the results of the said experiment are given in Table-8.

Table - 8

In experiment 2, the values for the plain concrete beam wherein no reinforcement member is used are determined and the results of the said experiment are given in Table-9.

Table - 9

According to the Experiment 1 and Experiment 2, the comparative graph of the load-crack mouth curve for the plain concrete and the concrete on which the reinforcement member according to the invention is applied is shown in figure 1. When the load-crack mouth graph shown in Figure 1 is examined, it is seen that Nylon 6.6 synthetic fibers coated with 54 mm long polycarboxylic ether provide to the concrete the ability to change form under load. By this way, concrete can absorb energy by gaining ability of deflection and the said application gives toughness to concrete under sudden and dynamic loads. It is also seen from the graph in Figure 1 that the adherence provided by the polycarboxylic ether material coated on the nylon 6.6 fibers to the concrete is effective. During the experiment, in the part after the 0.5 mm value, in other words, in the part after deformation softening, the fibers were effectively attached to the concrete matrix and the load carried by the concrete has increased despite the cracking of the concrete.

Plain concrete breaks suddenly after the first crack and there is no deflection capability. When the reinforcement member comprising polycarboxylic ether coated Nylon 6.6 is added into the concrete, it provides the ability to change form to the concrete.

When the moments in stress distributions are matched, the following equations are acquired:

ofl = 0.45M

of4 = 0.37&4

The moment capacity calculated for service limit state is calculated as follows:

M_p = fn* h²/6.

In the said equation,

fn: Residual strength corresponding to 0.5mm crack mouth (N/mm2)

h: shows concrete cross section, height (mm).

According to the results obtained in Experiment 1 and Experiment 2, the comparison of the frl residual strength values of the concrete to which the reinforcement member of the invention is applied and the reference concrete (plain concrete) is given in Table 10.

Table - 10

In the column indicated by % in the aforementioned table, frl value of said reference concrete is matched to 100 and it is seen that the frl value of the concrete in which the reinforcement member comprising polycarboxylic ether coated nylon 6.6 of the present invention is used in ratio of 4 kg/m³ brought to the same value accordingly has increased 362% relative to the reference concrete.

The moment capacity calculated for bearing capacity limit state is calculated as follows:

Mp = fr4* h2/6.

According to the results obtained in Experiment 1 and Experiment 2, the comparison of the fr4 values of the concrete to which the reinforcement member of the invention is applied and the reference concrete (plain concrete) is given in Table 11.

Table - 11

As it is seen in Table 11, plain concrete has no fr4 value. The concrete wherein the reinforcement member comprising the polycarboxylic ether coated Nylon 6.6 of the present invention is used in ratio of 4 kg/m3 in the concrte provides a strength of 1,985 N/mm2. By means of using the reinforcement member of the present invention in the concrete, ductility is provided to the plain concrete, brittle braking is transformed into ductile breaking, and thus deflection ability under load after first crack is provided. Polycarboxylic ether coated Nylon 6.6 three dimensionally distributed in concrete increases the durability of the concrete by minimizing both the plastic and drying shrinkage that may occur in the concrete. In terms of labor and cost, the said application is advantageous before the existing applications, and the negative effect of the fiber amount on the processability of the concrete is reduced by the present invention (for example up to 25%).

Claims

1. A reinforcement member manufactured from synthetic fibers suitable for reinforcing concrete, characterized in that the said reinforcement member comprises synthetic nylon 6.6 fibers coated with a plasticizer.

2. A reinforcement member according to claim 1, characterized in that the said plasticizer is a superplasticizer.

3. A reinforcement member according to claim 1 or 2, characterized in that the said plasticizer comprises polyacrylate polymer or its derivatives.

4. A reinforcement member according to claim 1 or 2, characterized in that the said plasticizer comprises polycarboxylic ether or its derivatives.

5. A reinforcement member according to any one of the preceding claims, characterized in that the said synthetic nylon 6.6 fibers comprises a plurality of filaments wherein the diameter of which is range of 20-40 microns, and which are combined together such that it has a linear density of 140-330 tex.

6. A reinforcement member according to any one of the preceding claims, characterized in that the length of the nylon 6.6 fibers coated with the said plasticizer is in range of 30-60 mm.

7. A reinforcement member according to any one of the preceding claims, characterized in that the plasticizing coating on the said nylon 6.6 fibers has a thickness of 0,3mm-0,5mm.

8. A production method for the reinforcement member according to any one of the preceding claims, characterized in that the plasticizing coating on the said nylon 6.6 fibers is applied by one of the following methods such as heat treatment, dipping, spraying or impregnation.

9. A production method according to claim 8, characterized in that it comprises the steps of suspending the aqueous solution of plasticizers into a metal container; passing the said nylon 6.6 fibers through the said aqueous solution and enabling the said fibers to absorb the said solution, and then curing the said nylon 6.6 fibers by passing through a furnace.

10. A production method for a concrete comprising a reinforcement member according to any one of the claims 1-7 or produced according to the method according to claims 8-9, characterized in that it comprises the step of adding reinforcement member in an amount of 1.5-12 kg in each 1 m³ concrete.