JP2000314108A - Bridge equipped with high-strength lightweight concrete floor slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make high-strength lightweight concrete floor slabs of the bridge floor of various kinds of bridges hardly being damaged or broken by wrecking heavy machinery during replacement work for the pavement of the concrete floor slab, thereby lengthening the life of the concrete floor slab and suppressing the progress of rusting of reinforcing steel bars and PC steel material inside the high-strength lightweight concrete floor slab. SOLUTION: Bridge floor of the bridge is constituted with a high-strength lightweight concrete floor slab 1 which is a cured, hardened body of hydraulic mixture of Portland cement, artificial lightweight coarse aggregate and artificial lightweight fine aggregate with a mix proportion ratio by weight of (9.5 to 10.5):(1.05 to 11.5):(11.5 to 12.5) and a polymer cement concrete layer having a thickness of 10 to 25 mm is adhered to the top surface of the pavement side of a precast prestressed concrete floor slab having a bulk density of 1.6 to 1.8 t/m3 after hardening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a road bridge, a railway viaduct,
The present invention relates to various bridges constructed by laying prestressed concrete slabs preliminarily precast and finished at a factory in a pedestal on a bridge floor in a pedestrian bridge or the like.

[0002]

2. Description of the Related Art When precasting ordinary concrete slabs in a factory, it has been conventionally used to improve the strength by introducing a necessary precast force and use the slabs as floor slabs of various bridges. The production of floor slabs off-line can be performed in near-ideal conditions, such as material selection, implantation control, curing, and quality inspection, in a near-ideal state. It is possible to supply an economically advantageous floor slab.

On the other hand, various bridges have recently been exposed to severe environments. In particular, road bridges are increasing in size and speed with the increase in vehicles, and their use conditions are becoming more severe every day. Inevitably, the pavement and floor slabs are severely damaged, and the frequency of repairs and slab replacements is increasing. In many road bridges, old pavements are often removed and re-paved due to damage such as wear, cracks, and delamination of the asphalt concrete layer of the pavement. However, as time passes, the concrete slab itself is damaged, and it is necessary to replace part or all of the slab.

[0004] Pavement replacement is carried out by first removing, demolishing and removing the asphalt concrete layer by using heavy equipment. However, the impact on the concrete slab cannot be avoided, and the concrete slab often breaks at the same time as the pavement is demolished. I do. In particular, reinforced concrete slabs using conventional lightweight concrete are susceptible to this effect. In addition to the physical damage caused by the heavy equipment, the concrete slab is inevitably deteriorated due to chemical aging.
This is a phenomenon caused by carbonation of cement, and various studies have been made in the past, but no definitive measures have been found.

[0005]

A bridge is generally constructed by laying a reinforced concrete slab on a traffic surface of a vehicle such as a vehicle on the bridge floor of a steel or concrete bridge, and paving asphalt concrete or the like on the upper surface thereof. Conventional bridges have used floor slabs made of ordinary concrete. However, one floor slab of ordinary concrete has a width of 1
When a precast concrete slab of 3.5 m in length, 3.5 m in length and 250 mm in thickness is employed, its weight exceeds about 2 t. Adding reinforcing steel, PC steel, fittings, etc. to this will further increase the weight.

If the weight of the concrete slab is reduced,
There is an advantage that the burden on the main girder due to the increase in the size of the vehicle can be reduced. This is particularly advantageous when replacing reinforced concrete slabs in steel bridges. In addition, the capacity of heavy machinery to handle concrete slabs during new construction and intermediate repairs will be reduced, and the load on the bridge itself will be reduced by the heavy machinery for facilities itself. It will work favorably. As described above, adopting lightweight concrete for the concrete slab has a great effect of reducing the unit weight.

On the other hand, in a road bridge, when the vehicle traffic exceeds a certain level, the pavement becomes a mechanical slab such as wheel load of vehicle, impact, tire abrasion and the like, and concrete floor slab caused by climate change and temperature fluctuation. Due to weathering and thermal expansion and contraction, cracks and wear occur. If the damage exceeds a certain level, it is necessary to replace the asphalt concrete pavement. Heavy equipment for crushing is used to remove the pavement.
When the concrete slab is reused and only the pavement is replaced, damage to the slab surface is inevitable. In particular,
This effect is significant for lightweight concrete. In addition, the damage of the concrete layer on the floor slab surface due to the heavy equipment leads to a reduction in the amount of covering of the reinforcing steel bar and the PC steel material, which is a problem in the strength of the floor slab. Further, cracks are promoted by impact or the like, and the carbonation of the concrete is further accelerated, thereby causing a problem that the life of the concrete slab itself is shortened.

[0008] As described above, adaptation of the lightweight concrete slab to the bridge floor of various bridges is required to realize the weight reduction.
Despite the many benefits, the use of lightweight aggregates makes them less resistant to the movement of heavy equipment, such as breaking the surface of a slab. This issue is a situation that could hinder the spread of lightweight concrete slabs.

Next, the problem of the concrete slab itself will be described. The concrete structure solidifies by the hydration reaction of cement and develops high strength. However, in the process of producing a concrete structure, fine cracks are often incorporated. This is due to a temperature difference inside and outside the structure when the concrete slab after molding is dried, and breathing on the surface layer during construction.

When these concrete slabs are used in an actual bridge, they gradually develop into a cracked state due to the expansion and contraction caused by the rise and fall of the temperature and the repetition of the freeze-thaw cycle of rainwater invading from cracks. As a result, carbon dioxide gas in the air penetrates through the crack opening to induce a so-called neutralization phenomenon of the concrete, which leads to the outflow of the cement component and the rusting of the reinforcing steel and the PC steel. Leaving it in this state will accelerate the deterioration of the concrete slab. In particular, rusting of steel material involves volume expansion on the surface of the steel material and generates tensile stress inside the concrete structure, which further promotes cracking and causes a vicious cycle of neutralization. The present invention seeks to provide a solution to the above problems.

[0011]

[Means for Solving the Problems] The above problems are achieved by the present invention having the following configuration.
Solved by Ming. (1) Portland cement and artificial lightweight coarse aggregate and artificial
The weight ratio of the lightweight fine aggregate is 9.5 to 10.5: 10.5
~ 11.5: water-curable mixture consisting of 11.5-12.5
The cured product is a cured product having a unit volume weight after curing of 1.
6 to 1.8 t / m ³Precast prestressed concrete
On the upper surface of the pavement side of the cleat deck, polymer cement
High strength in which the reed layer is deposited with a thickness of 10 to 25 mm
The bridge deck is composed of lightweight concrete slabs.
With a high-strength lightweight concrete floor slab
Bridge. (2) Portland cement and artificial lightweight coarse aggregate and artificial
The weight ratio of the lightweight fine aggregate is 9.5 to 10.5: 10.5
~ 11.5: water-curable mixture consisting of 11.5-12.5
Cured product, having a unit weight of 1 after curing.
6 to 1.8 t / m ³Precast prestressed concrete
On the upper surface of the pavement side of the cleat deck, polymer cement mortar
High-strength lightweight with a metal layer deposited with a thickness of 5 to 10 mm
Note that the bridge deck is composed of concrete slabs.
Bridge with high strength lightweight concrete slab
Beams. (3) The precast prestressed concrete floor
Nitrite is present on the surface of reinforcing steel inside the plate and in the vicinity.
3. The method according to claim 1, wherein the components are dispersed.
Bridges with high-strength lightweight concrete slabs. (4) The precast prestressed concrete floor
Nitrite is present on the surface of the PC steel inside the plate and in the vicinity.
Any of the preceding items 1 to 3, characterized by being dispersed
A high-strength lightweight concrete slab according to item 1 is provided.
Bridge.

(5) Portland cement and artificial lightweight coarse
9. The weight ratio of the aggregate and the artificial lightweight fine aggregate is 9.5 to 10.
5: 10.5-11.5: 11.5-12.5
Cured cured product of water-curable mixture, unit volume after curing
Loading weight is 1.6 to 1.8 t / m ³Concrete floor slab
Precast prestressed conc that constitutes the bridge deck
A nitrite solution is supplied from the surface of the reed floor slab,
Reinforced iron inside cast prestressed concrete slab
Nitrite is dispersed in the bar and its vicinity,
Concentrate characterized by forming a passivation layer in the layer part
High-strength lightweight concrete that constitutes the bridge floor of the REIT floor slab
Floor slab processing method. (6) The precast prestressed concrete floor
Nitrite is dispersed in the PC steel inside the plate and in the vicinity.
To form a passive layer on the surface of PC steel.
The bridge floor of the concrete slab bridge described in the preceding item 5
A method for treating high-strength lightweight concrete slabs.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the basic characteristics of the lightweight concrete slab to which the present invention is applied are as follows: the unit volume weight is 1.6 to 1.8 t / m ³ ; Compared with the unit volume weight (about 2.35 t / m ³ ), a weight reduction effect of 20 to 30% is possible. Usually, in order to reduce the weight of the concrete slab, artificial lightweight aggregates are used as coarse aggregates and fine aggregates in concrete mixing. The artificial lightweight aggregate is desirably a porous, low water-absorbing, high-strength material such as a fired product of expanded shale or expanded clay or fired fly ash. In addition, a synthetic resin foam or the like can be partially used. Furthermore, in order to improve the strength of the slab, the reinforced slab structure will be used when the slab is manufactured, and a pretension type PC structure in the direction perpendicular to the bridge axis will be used. When laying the floor slab, the post-tension PC structure or reinforced concrete (R)
C) The structure is adopted. By introducing this prestressing force,
The punching shear strength, which is a weak point of lightweight concrete slabs, is greatly improved (hereinafter, lightweight concrete slabs that have been precast and improved in strength by introducing prestressing force are referred to as high-strength lightweight concrete slabs. ).

While the bridge floor of various bridges is installed and used with a high-strength lightweight concrete slab, the asphalt concrete on the pavement surface is replaced. There is a problem that the surface of the lightweight concrete slab is damaged. However, as a solution to this problem, when a high-strength lightweight concrete slab is manufactured in a factory, this problem can be solved by forming a surface protective layer on the surface in contact with the asphalt concrete pavement. This protective layer is manufactured by driving the high-strength lightweight concrete layer into the formwork during the manufacturing process of the high-strength lightweight concrete slab, and then driving the protective layer material to provide an additional layer. It is formed so as to be deposited. The material used for the protective layer is preferably polymer cement concrete or polymer cement mortar. In order to reliably achieve the purpose of protecting high-strength lightweight concrete slabs, in the case of polymer cement concrete, the thickness is 10 mm or more, preferably 1 mm or more.
0-25mm, thickness 5m with polymer cement mortar
m or more, preferably 5 to 10 mm.

The effect of the protective layer is not only to prevent the concrete slab from being damaged by heavy equipment when replacing the pavement material, but also to prevent rainwater entering from a damaged portion of the pavement material or a seam when used as a bridge floor. Also acts as a waterproof layer.

Next, a description will be given of an invention in which nitrite is permeated into a high-strength lightweight concrete slab to prevent corrosion of a reinforcing steel bar and a PC steel material provided therein. It is considered that most of the rusting phenomena occurring on the reinforcing steel inside the concrete slab and on the surface of the PC steel material are caused by cracks generated on the concrete slab except for the electrode phenomenon.

During the hardening process of the concrete floor slab, after the hydration reaction of the cement is completed, the concrete shows alkalinity, and a passive state is formed on the surface of the reinforcing steel bar and the PC steel, thereby preventing rusting. However, small and large cracks gradually occur due to the occurrence of surface microcracks due to the bleeding phenomenon that occurs during the hardening process after concrete is poured, and the expansion and contraction of the concrete slab caused by temperature fluctuations due to climate change and shrinkage during drying. The carbon dioxide gas and rainwater in the air infiltrate through the voids created by the cracks, neutralization progresses inside the concrete, the pH value decreases, and rust occurs on the reinforcing steel bars and the PC steel. When steel rusts, it undergoes volume expansion in the process of producing iron oxide,
It progresses with a vicious cycle of further promoting cracks. Most concrete slabs of slab bridges are exposed to open-air, and this process is in an environment where rusting cannot be avoided. Therefore, measures to prevent rust of reinforcing steel and PC steel inside the high-strength lightweight concrete slab are indispensable issues for maintaining the strength of the concrete slab.

In the present invention, this problem has been solved by using a nitrite solution having excellent oxidation characteristics. When the nitrite ion adheres to the surface of the reinforcing steel bar and the PC steel material, it causes an oxidation reaction with the steel material, and the iron oxide generated as a result becomes inactive and acts to hinder the further progress of rusting.

The actual infiltration operation is performed as follows. That is, the nitrite solution is permeated from the surface of the high-strength lightweight concrete slab, and the permeation is repeated as necessary at least until the surface of the reinforcing steel bar and the PC steel material is covered with this solution. A widely used method is to spray a nitrite solution onto the surface of a concrete floor slab using a sprayer and adhere the solution to the surface by using capillary action.

In order to perform this infiltration work more uniformly and effectively, a vacuum impregnation method is effective. When the concrete slab is placed in a vacuum vessel and evacuated, minute voids inside the concrete slab are evacuated. As it is,
When the nitrite solution is poured into a vacuum vessel and the concrete slab is impregnated with the nitrite solution, the concrete slab penetrates through the fine cracks in the concrete slab and can easily penetrate into the interior of the slab. After the infiltration, return to atmospheric pressure, and then apply a sealing paint such as epoxy resin to the concrete floor slab to prevent the outflow of the impregnated nitrite. Can be prevented.

[0021]

[Function] In general, a concrete structure has a large resistance to compressive stress, but is relatively weak to tensile stress. The high-strength lightweight concrete slab, which is the object of the present invention, greatly reduces unit weight and provides great advantages such as workability and economic efficiency. The decline is inevitable. Therefore,
The prestressing force is effectively introduced into the concrete slab to supplement this strength drop.

Normally, a road bridge has a structure in which asphalt concrete is paved above a concrete slab to directly support wheel loads of a vehicle. Abrasion by wheels due to traffic,
Replacement work is required due to damage such as pressing load and weathering. At this time, since the asphalt concrete layer is removed and removed by the heavy equipment, damage to the surface layer of the concrete slab constituting the lower layer of the pavement is inevitable. Particularly, in the case of lightweight concrete slabs, the hardness of the coarse aggregate is generally low and the abrasion resistance is small, so that it is easily damaged by the impact of heavy equipment, dropping, and the like. Another problem is that during the precasting of the concrete floor slab, the surface layer structure tends to become brittle due to the bleeding phenomenon in which fine particles tend to accumulate on the surface layer.

In order to solve these problems, it is effective to form a reinforcing layer on the surface in advance when manufacturing a precast concrete slab. This surface strengthening layer is formed by applying a protective layer having a constant thickness to the surface of the concrete slab and integrating it with the slab. In consideration of the mechanical strength, the degree of adhesion to the floor slab, and the like as characteristics required for the protective layer, polymer cement concrete or polymer cement mortar is suitable for the material.

FIG. 1 is a sectional view of a high-strength lightweight concrete slab having a protective layer formed thereon. The structure is such that a protective layer 2 is deposited on the upper surface of a high-strength lightweight concrete slab 1.
Part of the prestressed steel material 3 penetrates the high-strength lightweight concrete slab 1. FIG. 2 shows a molding step of the protective layer.
(A) is a form preparation step, in which the form 4 is installed and the reinforcing steel 5
2 shows a state in which the prestressed steel material 3 is attached to the reaction table 6. (B) shows a high-strength lightweight concrete casting process, in which a high-strength lightweight concrete material 7 having a predetermined composition is cast into a formwork. (C) shows a protective layer finishing step. The protective layer material 8 is deposited on the surface of the high-strength lightweight concrete after the casting to form a protective layer. (D) shows a steam curing step. The entire form 4 is covered with a curing sheet 9 and the steam supply port 1 is provided.
Steam is supplied from zero, and the high-strength lightweight concrete and the protective layer are cured integrally. (E) is a prestress introduction step, in which the tension is gradually relaxed from the reaction table 6 and the prestress force is introduced into the high-strength lightweight concrete slab. Thereafter, through an inspection process, a multi-layer slab integrally molded with the protective layer is completed.

This protective layer can also have an effect as a rainwater waterproofing layer on the concrete slab after construction on site. Usually 5mm for polymer cement mortar
Above, 10mm for polymer cement concrete
The above layer thickness is desirable.

Next, a rust-prevention mechanism for reinforcing steel and PC steel of a high-strength lightweight concrete slab using a nitrite solution,
As an incidental effect, a mechanism for preventing deterioration of the concrete matrix will be described. In general, the pH inside concrete after the hydration reaction of cement is about 12 which is strongly alkaline, and the reinforcing steel or the surface of PC steel is in a state where the passivation of iron oxide is formed and the progress of rusting is suppressed. Has become. However, with the passage of time, the minute cracks gradually crack and the carbonic acid gas in the atmosphere infiltrates, neutralizing the alkaline environment inside the concrete and lowering the pH below 11. The active layer is damaged and red rust such as iron hydroxide starts to form.

This rusting phenomenon promotes the swelling of the reinforcing steel bar and the surface of the PC steel and induces a vicious cycle of further promoting cracking. However, in this state, if nitrite ions are interposed, the nitrite ions and divalent iron ions cause an oxidation reaction on the surface of the reinforcing bar, and the passive state of iron oxide generation is regenerated. The maintenance of this passive state is due to swelling due to rust,
Cracking and the progress of neutralization will be suppressed.

Next, as an additional effect on high-strength lightweight concrete slabs when lithium nitrite is impregnated as nitrite, there is prevention of deterioration of the concrete matrix, and its mechanism will be described. The concrete body in which the aggregates are firmly bonded by the hydration reaction of the cement, the sedimentation of the rainwater and the neutralization of the aggregates progress with the aging, and the silica component of the aggregate reacts with the alkali component of the cement. To form alkali sodium silicate. This compound absorbs moisture and swells, causing numerous cracks in the concrete, causing salt damage and secondary deterioration of accelerated neutralization. However, when lithium ions are present, the reactive silica component from the aggregate reacts with lithium to form lithium silicate. This lithium silicate is insoluble and does not cause moisture swelling like sodium silicate, and acts to fix silica.

Further, since lithium ions react with a water-soluble gel product as sodium silicate to be converted into an insoluble substance, the effect of suppressing outflow and deterioration of concrete components is great. In particular, since the ionic radius of lithium ions is smaller than that of other alkali ions, they penetrate well into a fine matrix and increase the effect of suppressing deterioration. That is, the ionic radius of sodium is 0.95 °, the ionic radius of potassium is 0.99 °, and the ionic radius of potassium is 1.33 °, all of which are larger than the ionic radius of lithium, 0.60 °, and lithium ions have excellent permeability. ing.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples. A prototype model similar to the actual model in which a protective layer was provided on the pavement surface of the high-strength lightweight concrete slab, which was the object of the present invention, was manufactured, and its practicability was confirmed by investigating its characteristics. Among the lightweight aggregates used for the production of the lightweight concrete slab as the base material, the coarse aggregate has a surface specific gravity of 1.65 and an absolute dry specific gravity of 1.30.
As the fine aggregate, ordinary fine aggregate having a surface dry specific gravity of 2.53 was used. Design standard strength 500kgf / c
m ² , slump value 12 or more, air volume 5.0 ± 1.
The blend was determined by trial kneading so as to be 0%. As a result, the optimum mixing ratio of concrete was coarse aggregate 609, fine aggregate 735, Portland cement 500, and water 130 (all units are kg / m ³ ). Unit volume becomes the degree of weight reduction weight at 2.00t / ^{m 3,} it showed 2.35 T / ^{m 3} to 15% of the weight reduction effect of the ordinary concrete.

Next, based on the above composition,
0mm, length 3,500mm, thickness 250mm real floor
Introduce prestressing force by precasting plate-size specimens
Further, the protective layer of the present invention is coated on the surface of the specimen with a polymer.
-Protective layer by precasting 30mm with cement mortar
Prototype of high-strength lightweight concrete slab with
The strength properties were investigated. As a result, the compressive strength was changed to material age 28.
53.8 N / mm per day ²Becomes almost the design standard value 50N
/ Mm²Achieved. With a span of 3.0m and a bending strength of 9.8
kN or more. Furthermore, the punching shear strength was measured.
As a result, it showed 750kN or more, and it was
Enough for the wheel load of 98 kN used in the design of
It was confirmed that it had shear force. That is, protection
The strength of the high-strength lightweight concrete slab body
It was found that there was no effect on the degree characteristics. More than
As a result, the realization of a high-strength lightweight concrete slab with a protective layer
The utility was fully proved.

[0032]

Since the present invention is configured as described above, it has the following effects.
The light-weight concrete floor by a weight-lifting machine etc. generated at the time of pavement replacement work by applying a protective layer of polymer cement concrete or polymer cement mortar on the surface of the high-strength lightweight concrete slab constituting the bridge floor of various bridges. The plate can be prevented from being damaged or damaged, and a longer life can be achieved. In addition, by infiltrating the nitrite solution into the high-strength lightweight concrete slab and dispersing it on the surface of the reinforcing steel and the PC steel and in the vicinity thereof, it is possible to suppress the progress of rusting of the reinforcing steel and the PC steel. it can.

[Brief description of the drawings]

FIG. 1 is a partially sectional perspective view of a high-strength lightweight concrete slab provided with a protective layer according to the present invention.

FIG. 2 is a manufacturing process diagram of a high-strength lightweight concrete slab having a protective layer according to the present invention.

[Explanation of symbols]

1 High-strength lightweight concrete slab, 2 Protective layer, 3 Prestressed steel,
4 formwork, 5 reinforcing bars,
6 Reaction table, 7 High-strength lightweight concrete,
8 protective layer material, 9 curing sheet,
10 steam piping,

Claims (6)

[Claims] The weight ratio of Portland cement to artificial lightweight coarse aggregate and artificial lightweight fine aggregate is 9.5 to 10.5: 1.
0.5 to 11.5: A curing cured product of water-curable mixture comprising 11.5 to 12.5, the unit volume weight after curing of 1.6~1.8t / ^{m 3} precast prestressed concrete A high-strength lightweight concrete slab characterized in that a bridge deck is constituted by a high-strength lightweight concrete slab in which a polymer cement concrete layer is deposited to a thickness of 10 to 25 mm on the pavement side upper surface of the slab. A bridge comprising: 2. The weight ratio of Portland cement to artificial lightweight coarse aggregate and artificial lightweight fine aggregate is 9.5 to 10.5: 1.
0.5 to 11.5: A curing cured product of water-curable mixture comprising 11.5 to 12.5, the unit volume weight after curing of 1.6~1.8t / ^{m 3} precast prestressed concrete A high-strength lightweight concrete slab comprising a high-strength lightweight concrete slab in which a polymer cement mortar layer is deposited with a thickness of 5 to 10 mm on the pavement side upper surface of the slab. A bridge comprising: 3. A nitrite is dispersed on a surface of a reinforcing bar inside the precast prestressed concrete slab and a portion in the vicinity thereof.
A bridge comprising the high-strength lightweight concrete floor slab as described. 4. The high-strength, lightweight structure according to claim 1, wherein nitrite is dispersed on the surface of the PC steel material inside the precast prestressed concrete slab and in the vicinity thereof. Bridges with concrete slabs. 5. The weight ratio of Portland cement to artificial lightweight coarse aggregate and artificial lightweight fine aggregate is 9.5 to 10.5: 1.
0.5 to 11.5: consisting of 11.5 to 12.5 a curing cured product of water-curable mixture, unit volume weight after curing of 1.6~1.8t / ^{m 3,} a concrete floor A nitrite solution is supplied from the surface of the precast prestressed concrete slab constituting the bridge deck of the slab bridge, and the nitrite is dispersed in the reinforcing steel inside the precast prestressed concrete slab and a portion in the vicinity thereof. A method for treating a high-strength lightweight concrete slab constituting a bridge deck of a concrete slab slab characterized by forming a working layer. 6. The concrete floor according to claim 5, wherein nitrite is dispersed in the PC steel inside the precast prestressed concrete slab and in the vicinity thereof to form a passive layer on the surface of the PC steel. A method for treating high-strength lightweight concrete slabs that make up the bridge deck of a bridge.