JPH0155225B2 - - Google Patents

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 columns and walls is poured sequentially from top to bottom after the preceding concrete has substantially hardened, has many advantages over the sequential pouring method when applied to large-scale underground construction projects. Therefore, as the number of these construction projects has increased in recent years, the number of cases in which they have been adopted 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. There are three known methods of pouring joint construction in the reverse pouring method: the direct method, the filling method, and the injection method, but the filling method is currently considered to be the most preferred. In the filling method, post-cast concrete is placed 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 being press-fitted into the joint gap,
Good fluidity for easy injection and filling without material separation (flow value of 230 mm or more,
(preferably 250 mm or more). The present inventors previously proposed in Japanese Patent Application No. 60-15563 a high-performance filled mortar that is completely integrated with the preceding concrete. That is,
We discovered that in order to achieve complete integration with the preceding concrete, it is necessary to satisfy the conditions of an expansion rate of 0.2 to 2.0% (preferably 0.8 to 1.5%) and a breathing rate of 0.1% or less. We have obtained technical knowledge that it is best to appropriately mix the gas-generating swelling agent and the thickening agent in order to achieve this, and the contents thereof are described in the specification. [Problems to be solved by the invention] According to the prescription described in the specification of Japanese Patent Application No. 60-15563, in order to reduce the breathing rate to 0.1% or less,
Approximately 0.25 thickening agent based on cement weight in mortar
Must be added in an amount of at least % by weight. It has been found that when such a large amount of thickening agent is added, the viscosity of the mortar increases and dilatancy 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. Additionally, adding a large amount of thickening agent often results in an increase in the amount of entrained air, and at the above-mentioned high usage level, the physical properties of mortar may 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, thickeners are usually added during mortar mixing, but since thickeners are generally added in the form of powder, they tend to cause so-called lumps, which makes it difficult to mix completely uniformly in the mortar, and the viscosity increases. Since the dissolution rate of the thickening agent is also slow, great care and time are required during mortar production, and such problems become more apparent as the amount of the thickening agent added increases. In addition, 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. [Means for Solving the Problems] According to the present invention, as a filling mortar that effectively achieves the above object, a unit cement amount; 500
~1000Kg/m ³ , water-cement ratio: 0.30-0.60, sand-cement ratio: 1-2.5 for mortar, add a gas-generating expansion agent with an expansion rate of 0.2-2.0% to 5-5 per m ³ of mortar. 300g, a thickening agent in the range of 0.05 to 0.15% by weight based on the cement weight in the mortar, and an ultrafine mineral powder with a specific surface area of 8000 cm ² / g or more in the range of 1 to 5% by weight based on the cement weight in the mortar. A mortar composition for filling gaps in concrete in the reverse casting method, which has a breathing rate of 0.1% or less and a flow value of 230 mm or more, and further includes a water reducing agent with good dispersibility added to this composition, and a cement in the mortar. A mortar composition for filling is provided, which is additionally added in an amount of 0.5 to 1.5% by weight on a weight basis. Here, the expansion rate and breathing rate are determined 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 a value measured according to JIS R 5201 "Physical Test Method for Cement", and the specific surface area is a value measured by Blaine air permeation method. The filling mortar according to the present invention has been disclosed in the patent application filed in 1983.
−Compared to what was proposed in specification No. 15563,
The basic difference is that ultrafine mineral powder with a specific surface area of 8000 cm ² /g or more is used, the amount of thickener added is small, and no antifoaming agent is included. 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, such as aluminum, that generates gas when it reacts with alkaline water in which a cement hydration product is dissolved. , magnesium, zinc, etc. powder. Aluminum powder, especially one that passes the first or second class of "aluminum powder for paints" of JIS K 5906, is preferred. Such an expanding agent needs to be added in such an amount as to give the mortar an expansion rate of 0.2-2.0%, preferably 0.8-1.5%. The amount necessary for this purpose varies depending on the type and brand of cement, mortar composition, temperature, etc., but is in the range of 5 to 300 g per 1 m ³ of mortar. 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, hydroxyethylcellulose, and hydroxypropylcellulose, with methylcellulose being preferred. In the present invention, such a thickening agent is used based on the weight of cement in the mortar.
0.05-0.15% by weight, preferably 0.07-0.13% by weight
Added. This amount is very low compared to the method of adding a thickening agent in an amount of 0.2 to 2.0% by weight relative to the amount of water in the mortar, which was proposed in the previous Japanese Patent Application No. 15563/1986. . Ultrafine mineral powder is an important component in the filling mortar composition of the present invention. The present inventors have conducted various tests and studies to solve the above-mentioned problems, and found that ultrafine mineral powder with a specific surface area of 8000 cm ² /g or more was added in an amount of 1 to 5% by weight based on the weight of cement in the mortar. Preferably, when it is added in the range of 1.5 to 3.5% by weight, even if the amount of the thickener 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. I found out that it can be done. Additionally, 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. This ultrafine mineral powder has a specific surface area of 8,000 cm ² /g or more, preferably 10,000 cm 2 /g or more.
It is necessary that the powder be ultrafine with a particle size of cm ² /g or more. Examples of such ultrafine mineral powder include silica fume and ultrafine blast furnace slag powder. The mortar composition of the present invention also has the effect of reducing the bleeding rate and increasing the adhesion strength with the preceding concrete by adding a water reducing agent with good dispersibility. Water reducing agents that can be used include lignin sulfonates, oxycarboxylate salts, naphthalene sulfonic acid formaldehyde condensate salts (abbreviated as NSF), melamine sulfonic acid formaldehyde condensate salts (abbreviated as MSF), There are polyol-based water reducing agents, polycarboxylic acid-based water reducing agents, etc., and these can be used alone or in combination. By adding these highly dispersible water reducers in the range of 0.5 to 1.5% by weight, preferably in the range of 0.8 to 1.2% by weight, based on the cement weight in the mortar, they can be uniformly dispersed in the mortar to meet the requirements of the mortar. It reduces the amount of water, reduces the breathing rate, and develops adhesive strength with the preceding concrete when it is filled into the gap 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 are each added separately during mortar kneading. However, from the viewpoint of simplifying work on site, it is recommended 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. good. A mixed composition prepared by pre-mixing a thickening agent, an ultrafine mineral powder, and a gas-generating swelling agent is used as a ternary admixture; If a mixed composition prepared by pre-mixing a highly dispersible water reducing agent is called a quaternary admixture, the ternary admixture contains 1 to 10 parts by weight of a thickening agent, preferably 2 to 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 is 0.2 to 2.0% depending on the condition of the mortar to be applied. It is blended in amounts. The amount of the ternary admixture added to the mortar is preferably such that the weight percentage of the thickening agent and the ultrafine mineral powder is 1.1 to 5.1% based on the total amount of the mortar. Although it is possible to achieve the object of the present invention only by adding this ternary admixture, a water reducing agent may be further added to the 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 a certain period of time after the ternary admixture is added (this is called the delayed addition method). ) may be done. The delayed addition method has the advantage that the mortar flow value is larger than the simultaneous addition method. However, in this case, so-called flow loss, in which the flow value decreases as time passes after the end of kneading, increases, so it is better 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 added in an amount of 10 to 50% by weight. More specifically, 1 to 3 parts by weight of thickener, 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.
The amount is preferably 20 to 30% by weight, and the gas-generating expansion agent is blended in an amount such that the expansion rate is 0.2 to 2.0% depending on the condition of the mortar to which it is applied. The amount of this quaternary admixture added to the mortar is such that the total amount of the thickening agent, ultrafine mineral powder, and water reducing agent is 1.6 to 6% by weight based on the total amount of mortar.
The content is 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, although the use of an antifoaming agent was necessary in the previous Japanese Patent Application No. 15563/1980, it can be omitted in the present invention. The cement used may be any conventional cement used for ordinary mortar or concrete, and any cement such as Portland cement, mixed cement, sulfate-resistant cement, etc. can be used. At that time, the water-cement ratio is 0.30-0.60
The sand-cement ratio may be in the range of 1 to 2.5. The filling mortar composition according to the present invention can generally be filled into a concrete joint by placing a formwork around the joint and injecting the filling mortar through an injection port. This injection is continued until the mortar overflows from the vent. The injection operation may be performed by using gravity to pour the filling mortar 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 pouring mortar for prepackaged concrete and expanding grout for filling void spaces. [Example] A filling mortar having the composition shown in Table 1 was prepared. In both formulations, the unit cement amount is 775
Kg/m ³ and the sand-cement ratio was kept constant at 1.5. No.1
The mortar No. 2 is a comparative example with a small amount of ultrafine mineral powder added, and the mortar No. 3 is an example of the present invention. be. Table 1 also lists various characteristic values of these filling mortars. The test temperature was 20°C.

【table】

[Effect]

The filling mortar to which the ultrafine mineral powder of the present invention is added reduces the amount of thickening agent used and achieves a high flow value and low breathing rate even without adding an antifoaming agent, and is suitable for filling construction using the reverse pouring method. It has excellent properties as a mortar. More specifically, in addition to reducing the amount of expensive thickening agent used and not adding antifoaming agents, it is highly economical, and reducing the amount of thickening agent used reduces mortar viscosity, resulting in the development of dilatancy. This problem has been solved, and workability such as pumping is improved, and since the amount of entrained air does not become excessive, mortar of stable quality can be obtained. In addition, thickening agents 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 is used to mix these thickening agents and gas-generating expanding agents into mortar. It acts as a carrier for uniformly mixing the ingredients, making it possible to obtain a high-quality mortar as a filling mortar. In addition, by using a highly dispersible water reducing agent, the filling mortar is given unique rheological properties that homogenizes the additive components in the system and makes filling operations easier even with the same consistency. Can be done.

Claims (1)

[Claims] 1. When filling concrete joints in the reverse concrete pouring method, unit cement amount: 500 to 1000 Kg/m ³ , water-cement ratio: 0.30 to
0.60, sand-cement ratio; for mortar of 1 to 2.5,
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; a thickening agent of 0.05 to 0.15% by weight based on the weight of cement in the mortar;
and ultrafine mineral powder with a specific surface area of 8000 cm ² /g or more in the range of 1 to 5% by weight based on the weight of cement in the mortar, with a breathing rate of 0.1%.
A method for filling mortar into concrete gaps in a reverse pouring method, characterized in that the concrete gaps in the concrete joint are filled with mortar having the following properties and a flow value of 230 mm or more. 2 When filling concrete joints in the reverse concrete pouring method, unit cement amount: 500 to 1000 Kg/m ³ , water-cement ratio: 0.30 to
0.60, sand-cement ratio; for mortar of 1 to 2.5,
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; a thickening agent of 0.05 to 0.15% by weight based on the weight of cement in the mortar;
Ultrafine mineral powder with a specific surface area of 8000 cm ² /g or more is added in an amount of 1 to 5% by weight based on the weight of cement in the mortar, and a water reducing agent with good dispersibility is added in an amount of 0.5 to 1.5% by weight based on the weight of cement in the mortar. The breathing rate is 0.1% or less and the flow value is
A method for filling mortar into concrete gaps in a reverse pouring method, characterized by filling mortar of 230 mm or more into the concrete gaps at the joint.