In this project, rimsa has collaborated successfully supplying 1,900 T of steel fibers of their reference r glued 60 /0, 75 which provides the maximum exponent of reinforcement and simple addition to concrete since the fibers are supplied glued.
The Port of Huelva construction, currently in process, consists of a total of 180,000 m2 divided into 6 phases of approximately 30,000 m2 each.
Port infrastructures require great capacities, both in design and execution, and that they are being led by experts who collaborate in detail with the knowledge that involves work and professionalism to adapt to the customer’s needs.
rimsa has collaborated in the construction of several ports, offering optimal proposals, adapting them to the needs of each project. In the case of port pavements, the solution contemplates the replacement of the traditional reinforcement by steel fibers, thus speeding up the time of installation and reducing the cost.
This format is excellent for high dosages since it allows greater ease in mixing the concrete avoiding the formation of hedgehogs. In addition, the fibers are distributed homogeneously once the glue dissolves on contact with water in the mixing phase of the concrete, achieving less distance and less dispersion between fibers within the network that forms the matrix of the concrete. The slenderness of these fibers provides a greater quantity of fibers/kg achieving an increase in benefits.
Our experience of more than 35 years focused on researching and developing innovative works, allows us to plan and generate optimal stocks to avoid causing delays in large-scale works.
We have a wide network of our own warehouses, strategically located in different points of Spain, which allow us to offer an excellent service, as well as to optimize the transport costs to avoid making the product more expensive and to reduce delivery times.
“To date, rimsa has reinforced around 300,000m2 of port pavements with our reference r glued 60 / 0.75, distributed in seven State Ports, in different phases of execution, and through 16 different contractors”
Silvia Russo – Construction Division
These reinforced slabs are executed on a specially designed and prepared sub-base and both the ground and the sub-base must be well-drained and compacted to provide adequate and uniform support to the slab.
The relevant design methods assume specific models for the interaction between slab and subbase. The rigid pavement is a concrete structure supported on the ground, whose main purpose is to resist the loads applied through the support provided by the ground. The steel fibers behave as suture points within the concrete, thus preventing the propagation of cracks towards the interior and delaying collapse.
The pavement or slab behaves in a linear elastic way until the first crack; while the elastic limit is exceeded, the load capacity increases but the system remains rigid even though the slab modulus softens slightly.
In the case of steel fiber reinforced concrete, there is a loss of strength after the crack appears (reaching the fLOP value), and the material doesn’t break brittle under any circumstances. In the case of high dosages, residual strengths higher than fLOP cracking strengths are achieved. In all cases, the residual resistance fR1 depends linearly on the fiber content.
To avoid or control the stresses caused by deformations due to immobilization, the surface on which the concrete is poured must be uniform and without relief. In addition to the dosage fiber, the proper formulation of the concrete and the appropriate subsequent curing must be taken into account.
The pavement must be disconnected from all other structural elements by means of properly dimensioned isolation joints. The retraction cuts, with a depth of usually 1/3 of the thickness of the slab, are made at regular intervals between working joints to remove stress from deformations. The requirements of flatness and leveling are met by the proper execution method.
Selecting the correct type and dosage of fibers depends on their effectiveness and their influence on the concrete consistency. Increasing the fibers’ slenderness and using high dosages lead to an increase in mechanical efficiency, but also, can lead to a consistency decrease and a greater risk of fiber hedgehogs formation that will segregate from the concrete, which is why it is necessary to dose the right amount.
The upper limit of the fiber content is set at 1.5% by volume of the concrete. The use of very high dosages requires significant modification of the granular structure of the concrete.
The kneading is a critical phase of concrete with fibers; therefore it is necessary to check the homogeneity of the mixture. The risk of hedgehogs is reduced with the correct dosage with enough content of fine aggregate; as a general rule, the fibers will be incorporated together with the aggregates, preferably with the coarse aggregate at the beginning of the mixing, being discouraged as the first component of the mix. The pouring of the fibers is carried out slowly to guarantee the homogeneous distribution of the fibers in the mass of the concrete.
The characterization of HRFA campaigns (in this case the reference r glued 60 / 0.75) by rimsa and Smart Engineering, Spin-Off of the UPC, were carried out in the Polytechnic University of Catalonia (UPC) in order to evaluate the potentiality of the application and to study the behavior of the fiber 1769.
The most widespread test for characterizing the post-cracking behavior of HRF is the bending according to UNE-EN 14651. The residual strengths of the HRF used with the testing machine INSTROM 8505 are obtained.
The test UNE-EN 14651 was carried out to determine the values of residual resistance to bending fR, 1, m and fR, 3, m at 28 days of age. In each kneading, the fiber content was also determined according to UNE 83512-1 or UNE 83512-2.
In steel fiber reinforced concrete there is a loss of strength after the crack appears (reaching the fLOP value), not produced in any case the brittle breakage of the material. Even with high dosages, residual strengths higher than fLOP cracking strengths are achieved. In all cases, the residual resistance fR1 depends linearly on the fiber content.
The relationship between both residual resistances (fR1 and fR3) is also linear, with a slope value between 0.80 and 1.16; showing that the material maintains a stable behavior for both small and large crack widths.
The results of the residual strengths obtained in this test are valid and recommended for the incorporation of this reference in this type of work.
Another test carried out is the Barcelona Test, this is an alternative test to the notched beam test. This type of test is especially interesting and recommended for quality control during production, particularly in high volume concrete works.
- The dispersion of the results is less, and therefore the number of discarded batches is reduced and the characteristic values of the residual resistance are increased.
- It is a faster and cheaper test compared to the notch beam test.
- It can be carried out in any quality control laboratory, as only a conventional press is required to carry out compression tests.
- Constitutive equations have been developed for the design of HRF structures obtained with this test.
- It can be correlated with the beam test, therefore, establish the Barcelona test as the reference test during production control.
Traction resistance: In the direct tensile stress-strain diagram of HRFA, the fibers significantly stiffen the response in the pre-crack phase compared to that of traditional concrete, in an outstanding way, provide a residual post-crack resistance capacity due to the stitching effect between the two sides of the crack.
The most important effect on the mechanical behavior of concrete, due to the presence of the fibers, is manifested in the post-cracking tensile strength.
Compressive strength: The compressive strength of concrete does not vary significantly by the addition of fibers, although there may be a modest increase in relevant percentages of metallic fibers, there is a difference over simple concrete in ductility, this being higher when the concrete is reinforced with fibers.
Flexural strength: The increase in flexural strength when adding steel fibers are added to concrete is considerably greater than that of compressive and tensile strength. This is due to the ductile behavior of HRFA in the tensile cracked area, developing residual strengths.
Typically, the first crack strength, the resistance to breakage by flex traction, and the residual resistance to flex traction are determined. The increase in the resistance to the first crack obtained with the addition of steel fibers is minimal, which indicates that this property depends basically on the matrix and very little on the fiber content, size, and shape of these.
The breaking strength depends mainly on the volume of fibers and their slenderness, achieving important increases with respect to the resistance of the matrix if fibers with shaped ends are used.
Greater resistance to dynamic loads (impact): One of the main characteristics of HRFA is its resistance to impacts due to energy absorption, being in this case its resistance from 3 to 10 times the resistance of mass concrete. Additionally, the HRFA has a lower tendency to defragment and detach. All of the above is due to the sensitivity of the matrix, the resistance of the fibers to tearing and deformation.
Greater Tenacity: The variable that most influences the tenacity is the adherent capacity of the fibers.
Fiber-matrix adhesion: Fiber-matrix adhesion is the phenomenon that governs the behavior of HRFA after cracking when the fibers stitch the cracks delaying and making more ductile the phenomenon of composite exhaustion. Then it is understood the importance of the chemical, mechanical, and friction adhesion that starts after the total take-off of the fibers. In order to increase energy absorption, pull-out phenomena must be encouraged and the breakage of the fibers must be avoided.
Adhesion increases with the slenderness of the fibers and it has been proven that using fibers with shaped ends.
Steel fiber reinforced concrete durability: The addition of steel fibers in concrete generates mechanical behavior characterized by presenting a greater number of cracks with lower values of crack opening, an important factor in durability requirements.
In concrete without fissures it has been verified that the corrosion of the fibers is limited to the surface of the concrete. Once the surface is corroded, the effect of corrosion does not spread more than 2mm from the surface. The fibers show good resistance to corrosion in uncracked elements, even when the elements are exposed to seawater. Through X-ray analysis and electron microscopy, it has been observed that the reactions between HRFA and seawater are limited to a few millimeters below the concrete surface. These microchemical changes appear to have no negative effect on the durability and performance of concrete under sustained loads in a marine environment.
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