JPS6282170A - Method for filling concrete gap with mortar in reverse casting construction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mortar filling method for filling concrete joints in the reverse pouring method.

[Conventional technology]

The reverse pouring method, in which concrete for pillars, walls, etc. is poured sequentially from top to bottom after the preceding concrete has been practically placed, has many advantages over the sequential pouring method when applied to large-scale underground construction, so it has become popular in recent years. As the number of these construction projects increases, the number of examples of its adoption has increased. However, this reverse pouring method tends to cause defects in the concrete joints, so one of the key technical points is to perform pouring construction to obtain defect-free concrete joints.

The direct method is used as a joint construction method for the reverse pour method.

Three methods are known: a filling method and an injection method, but the filling method is currently considered to be the most preferred. The filling method is a method in which post-cast concrete is poured below the preceding concrete, leaving a filling gap between it and the preceding concrete, and this gap is filled with mortar of large consistency to complete the pouring. This is a joint construction method.

The mortar used in this filling method (filling mortar) needs to adhere closely to the concrete at the joint and have a high adhesion strength to the concrete. Then, when it is press-fitted into the joint gap.

Good fluidity (flow value of 230 mm or more) for easy injection and filling without material separation.

preferably 2501 or more).

The present inventors previously proposed in Japanese Patent Application No. 15563/1987 a high-performance filled mortar that is completely integrated with the preceding concrete. That is, in order to achieve complete integration with the preceding concrete, the expansion rate must be 0.2 to 2.
It was discovered that it is necessary to satisfy the conditions of 0% (preferably 0.8 to 1.5%) and a breathing rate of 0.1% or less. We have obtained technical knowledge that it is better to appropriately mix these agents with other agents, and the content thereof is described in the specification.

[Problem that the invention seeks to solve]

According to the prescription described in the specification of Japanese Patent Application No. 60-15563, the breathing rate is set to 0.1% or less.

The thickening agent should be added in an amount of at least about 0.25% by weight based on the weight of cement in the mortar. It has been found that when such a large amount of thickening agent is added, the viscosity of one mortar increases, and the gluability becomes noticeable, causing problems in pumping, etc. That is, in the reverse pouring method, filling mortar is normally injected into the joint gap by pumping, but this poses a problem in pumpability.

Furthermore, addition of a large amount of thickening agent often results in an increase in the amount of air entrained, and at the above-mentioned high usage level, the physical properties of mortar deteriorate due to air entrainment.

In particular, there is a problem in that strength loss is likely to occur. If an antifoaming agent is used in combination, this problem can be substantially solved, but there are also disadvantages associated with this, and since the antifoaming agent itself is expensive, it is also economically disadvantageous.

Furthermore, thickening agents are normally added during mortar kneading, but since thickening agents are generally added in powder form, they tend to cause so-called "mamako" and are difficult to mix completely uniformly in one mortar. Since the dissolution rate of the thickening agent is also slow, much care and time are required when producing one mortar, and such problems become more apparent as the amount of the thickening agent added increases.

Additionally, when using gas-generating swelling agents.

There is a problem with the mixability, and there is also the problem that it is not possible to obtain mortar of the desired homogeneous quality unless careful consideration is taken.

The present invention has been made with the aim of solving such problems.

c. Means for Solving Problems] According to the present invention, as a filling mortar that effectively achieves the above object, a unit cement I; 500 to 1000 k
g/m3, water-cement ratio; 0.30-0.60.
For mortar with a sand-cement ratio of 1 to 2.5, a gas-generating expansion agent with an expansion rate of 0.2 to 2.0% is added to the mortar. 5-300g per mortar, 0.05-0.15% by weight of thickening agent based on the weight of cement in the mortar,
and mineral ultrafine powder having a specific surface area of 8000 cm27 g or more in an amount of 1 to 5% by weight based on the weight of cement in the mortar. A mortar composition for filling gaps in concrete in the reverse pouring method, which has a breathing rate of 0.1% or less and a flow value of 2301 or more, and further includes a water reducing agent with good dispersibility in this composition based on the weight of cement in the mortar. A mortar composition for filling is provided in which the compound is continuously added in a range of 0.5 to 1.5% by weight.

Here, the expansion rate and breathing rate are the values measured by the "Test method for breathing rate and expansion rate of poured mortar for prepacked concrete" stipulated by the Japanese Society of Civil Engineers,
The flow value is measured according to JIS R5201 "Physical Test Methods for Cement," and the specific surface area is a value measured by Blaine air permeation method.

The filling mortar according to the present invention is disclosed in the earlier patent application published in 1986-15.
Compared to the one proposed in the specification of No. 563, it has a basic difference in that ultrafine mineral powder with a specific surface area of 8000 cm2/g or more is used, and the amount of thickening agent blended is small.
And does not contain antifoaming agents.

The content of the present invention will be specifically explained below.

The gas-generating expansion agent with an expansion rate of 0.2 to 2.0% used in the present invention is a fine powder that generates gas when it reacts with alkaline water in which cement Eiwa products are dissolved. 2. For example, refers to powders of aluminum, magnesium, zinc, etc. Aluminum powder, especially one that passes the first or second class of "aluminum powder for paints" of JIS K 5906, is preferred.

It is necessary that such swelling agents be added in such an amount as to give the mortar an expansion coefficient of 0.2 to 2.0%, preferably 0.8 to 1.5%. The amount of addition required for this depends on the type and brand of cement.

It varies depending on the mortar composition, temperature, etc.

It ranges from 5 to 300 g per mortar IITr.

The thickening agent used in the present invention is a water-soluble polymer substance that exhibits high viscosity when dissolved in water, and is sometimes called an organic thickening agent, a viscosity imparting agent, a thickening agent, etc. Thickening agents that can be used in the present invention include polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyethylene oxide, carboxymethyl cellulose, cellulose ethers, and the like. Examples of cellulose ethers include methylcellulose, hydroquine ethylcellulose, and hydroxypropylcellulose, with methylcellulose being preferred. In the present invention, such a thickening agent is used in an amount of 0.05 to 0.15% by weight based on the weight of cement in the mortar.
, preferably 0.07 to 0.13% by weight. This amount is very much higher than that proposed in the previous Japanese Patent Application No. 15563/1983, in which the thickening agent was added in an amount of 0.2 to 2.0% by weight to the amount of water in the mortar. The amount is low.

Ultrafine mineral powder is an important component in the filling mortar composition of the present invention. The inventors of the present invention have conducted various tests and studies to solve the above-mentioned problems.

Ultrafine mineral powder having a specific surface area of 8000 cm2/g or more is added in an amount of 1 to 5% by weight, preferably 1.5 to 365% by weight, based on the weight of cement in the mortar.

It has been found that even if the amount of the thickening agent added is reduced to the above-mentioned range, desirable characteristics as a filling mortar with a breathing rate of 0.1% or less and a high flow value can be obtained.

In addition, it has been found that when using a gas-generating expanding agent, the desired uniform expansion is achieved by assisting in uniform mixing of the gas-generating expanding agent into the mortar. The ultrafine mineral powder needs to have a specific surface area of 8,000 cm''/g or more, preferably 10,000 cm''/g or more. Examples of such ultrafine material powder include silica hneem and ultrafine blast furnace slag powder.

The mortar composition of the present invention also has the effect of reducing the rate of breathing and increasing the adhesion strength with the preceding concrete by adding a water reducing agent with good zero dispersibility. Water reducing agents that can be used include lignin sulfonates, oxycarboxylate salts, naphthalene sulfonate formaldehyde condensate salts (abbreviated as NSF),
Melamine sulfonic acid formaldehyde condensate salt (MSF
), polyol-based water reducing agents, polycarboxylic acid-based water reducing agents, etc., and these can be used alone or in combination. These highly dispersible water reducers are added in the range of 0.5 to 1.5% by weight based on cement in the mortar,
Preferably, it is added in an amount of 0.8 to 1.2% by weight, so that it is uniformly dispersed in one mortar to reduce the amount of water required for the mortar, reduce the breathing rate, and when filled into the gap with the preceding concrete. Develop adhesive strength with the preceding concrete.

In preparing the filling mortar composition according to the present invention, a thickening agent, an ultrafine mineral powder, a gas-generating swelling agent, and a highly dispersible water reducing agent may be added separately at the time of mortar kneading. However, from the viewpoint of simplifying work at the site, it is preferable to mix all of the first three or four components in advance to make one powder mixture composition, and then add this powder mixture composition to the mortar.

A mixed composition prepared by pre-mixing a thickening agent, an ultrafine powder of a tfL substance, and a gas-generating swelling agent is used as a ternary admixture, and a thickening agent, 112: an ultrafine powder of a substance, a gas-generating swelling agent. A mixed composition prepared by pre-mixing a highly dispersible water reducing agent is called a quaternary admixture.

The ternary admixture is a thickener containing 1 to 10 parts by weight, preferably 2 to 10 parts by weight.
6 parts by weight; 99 to 90 parts by weight of ultrafine mineral powder, preferably 98 to 94 parts by weight, and for gas-generating expansion agents, the expansion rate may vary from 0.1 to 0.5 parts by weight depending on the state of the mortar to be applied.
It is blended in an amount of 2 to 2.0%. The amount of this ternary admixture added to the mortar is such that the weight percentage of the thickening agent and ultrafine mineral powder is 1.1 to 5.1% based on the total amount of mortar.
It is better to make it so that Although it is possible to achieve the object of the present invention only by adding this ternary admixture, a water reducing agent can be further added to this ternary admixture. In this case, the ternary admixture and the water reducing agent may be added at the same time, but the water reducing agent is added after the time elapses after the ternary admixture is added (referred to as delayed addition method). You may. The delayed addition method has the advantage that the mortar flow value is larger than the simultaneous addition method. However, in this case, the so-called flow loss, in which the flow value decreases as time passes after the end of kneading, increases.
It is best not to take too much time after kneading until filling.

The quaternary admixture is composed of the above-mentioned ternary admixture and the aforementioned water reducing agent mixed in an amount of 10 to 50% by weight. More specifically, 1 to 3 parts by weight of the thickening agent, preferably 1.5 to 2.
5 parts by weight; 85 to 65 parts by weight of ultrafine mineral powder, preferably 75 to 70 parts by weight - 14 to 32 parts by weight of water reducing agent, preferably 20 to 30 parts by weight, applicable to gas-generating swelling agents. Depending on the condition of the mortar, the expansion rate may be 0.
It is blended in an amount of 2 to 2.0%. The amount of this quaternary admixture added to mortar is such that the total amount of thickener, ultrafine mineral powder, and water reducing agent is 1% to the total amount of mortar.
．． The amount is preferably 6 to 6% by weight, preferably 3 to 5% by weight.

It is also possible to add other admixtures known as mortar admixtures to the composition of the present invention to enjoy the effects of adding the well-known admixtures. However, regarding the use of antifoaming agents, although it was required in the previous Japanese Patent Application No. 15563/1980,
In the present invention, it can be omitted.

The cement used may be any ordinary cement used for ordinary mortar or concrete, such as Portland cement, mixed cement, sulfate-resistant cement, etc.
Any cement can be used. At that time, the water-cement ratio is in the range of 0.30 to 0.60, and the sand-cement ratio is 1.
It is sufficient if it is in the range of ~2.5.

In order to fill a concrete joint with the filling mortar composition according to the present invention, generally a formwork is placed around the joint,
This can be done by injecting filling mortar through an injection port. This injection is continued until the mortar overflows from the vent hole. The injection operation may be carried out by using gravity, in which filling mortar is poured from a position higher than the filling position of the gap, by injection using a pump, or by other known injection methods. The filling mortar of the present invention is very suitable as a mortar for filling joints in the reverse pouring method, and was developed to solve the aforementioned problems in the reverse pouring method. However, the mortar composition according to the present invention can also exhibit effects not found in conventional mortar compositions in other applications such as injection mortar for prepackaged concrete and expansion grout for filling void spaces.

〔Example〕

A filling mortar having the formulation shown in Table 1 was prepared. In both formulations, the unit cement amount was 775 kg/d and the sand-cement ratio was constant at 1.5. The mortar in No. 1 corresponds to the one described in Japanese Patent Application No. 60-15563, the mortar in No. 2 is a comparative example in which the amount of ultrafine mineral powder added is small, and the mortar in No. 3 is an example of the present invention. be. Table 1 also lists the characteristic values of these filling mortars. The test temperature was 20°C.

[Effect]

The filling mortar to which the ultrafine mineral powder of the present invention is added is
A high flow value and low breathing rate are achieved even with a reduced amount of thickening agent and no antifoaming agent added, and it has excellent properties as a mortar for filling in the reverse casting method. More specifically, in addition to reducing the amount of expensive thickening agents used and not adding antifoaming agents, it is highly economical, and reducing the amount of thickening agents used reduces mortar viscosity and eliminates problems caused by dilatancy. This improves construction efficiency such as pump pressure feeding, and since the amount of entrained air does not become excessive, mortar of stable quality can be obtained. In addition, thickeners and gas-generating expanding agents originally had the problem of being difficult to mix uniformly into mortar, but in the present invention, ultrafine mineral powder allows these thickening agents and gas-generating expanding agents to be uniformly mixed into mortar. It acts as a carrier for mixing, making it possible to obtain a high quality mortar as a filling mortar. In addition, by using a highly dispersible water reducing agent, it is possible to impart unique rheological properties to the filled mortar, such as homogenizing the additive components in the system and making the filling process easier even with the same consistency. can.

Claims (2)

[Claims] (1) When filling concrete joints in the concrete reverse pouring method, unit cement amount: 500~
1000kg/m^3, water-cement ratio: 0.30-0.
60, Sand-cement ratio: For mortar with a ratio of 1 to 2.5, add 5 to 300 g of a gas-generating expansion agent with an expansion rate of 0.2 to 2.0% per 1 m^2 of mortar, and a viscosity agent. 0.05 to 0.15% by weight based on the cement weight in mortar,
and 1 to 5% by weight of ultrafine mineral powder with a specific surface area of 8000 cm^2/g or more based on the weight of cement in the mortar.
Filling the concrete gap with mortar in the reverse pouring method, which is characterized by filling the concrete gap of the concrete joint with mortar having a breathing rate of 0.1% or less and a flow value of 230 mm or more, which is mixed in the range of Law. (2) When filling concrete joints in the concrete reverse pouring method, unit cement amount: 500~
1000kg/m^3, water-cement ratio: 0.30-0.
60, Sand-cement ratio: For mortar with a ratio of 1 to 2.5, add 5 to 300 g of a gas-generating expansion agent with an expansion rate of 0.2 to 2.0% per 1 m^3 of mortar, and a viscosity agent. 0.05 to 0.15% by weight based on the cement weight in mortar,
Ultrafine mineral powder with a specific surface area of 8000 cm^2/g or more is 1 to 5% by weight based on the cement weight in the mortar, and a water reducing agent with good dispersibility is 0.5 to 1% by weight based on the cement weight in the mortar. A concrete gap in the reverse pouring method, characterized in that the concrete gap of the concrete joint is filled with mortar having a breathing rate of 0.1% or less and a flow value of 230 mm or more, which is mixed in the range of .5% by weight. mortar filling method.