KR20120071000A - Fire-resistance of light-weight permanent form and method for preparing the same - Google Patents

Abstract

PURPOSE: A light weight refractory slope-type form composition and a manufacturing method thereof are provided to manufacture light weight refractory slope-type form which can be applied to high-strength concrete by mixing an optimal ratio of gypsum with the light weight mortar. CONSTITUTION: A light weight refractory slope-type form composition includes 10-15 parts by weight of gypsum. A volume ratio of light weighted refractory slope-type form composition to fine aggregate is 1:1.5-1:2. A manufacturing method of light weight fire-proof slope type form comprises a step of adding 10-15 weight% of gypsum. A combination ratio of binding material to fine aggregate of the light weighte refractory slope-type form composition is 1:1.5-1:2.

Description

Composition of light-weight fire-resistant slope formwork and its manufacturing method {Fire-Resistance of Light-Weight Permanent Form and Method for preparing the same}

The present invention relates to a composition of a lightweight fire-resistant slope formwork and a method for producing the same.

Lack of skills workers such as rebar workers and formwork, aging, foreign workers employment and low labor productivity due to the recent 3D industry evasion phenomenon are serious issues in the construction industry. In the past, the ratio of material costs was high, and rationalization was pursued to reduce material waste. However, these days, due to the rapid increase in labor costs, they are surviving the competition through air shortening, rationalization, and systemization. In addition, existing timber formwork generates a large amount of construction waste materials after concrete construction, generates noise and vibration during formwork, and steel formwork relies on equipment and manpower for excessive initial investment and assembly, disassembly, and transportation. The disadvantage is that it is late and sensitive to personnel supply and demand. In order to improve the shortcomings of the general formwork, the formwork is manufactured at the factory with a certain size and thickness, and the slope formwork which is only assembled in the field can be said to be efficient.

In addition, with the recent urbanization, large-scale, high-rise buildings and demand for such buildings are increasing, high-rise buildings with 30 or more floors have been generalized, and high-strength concrete is used for major structural members. However, high-strength concrete has been reported to have greater problems such as increased water vapor pressure and consequent explosion in concrete than fire due to low water-cement ratio, reduced internal voids, and reduced member cross-sectional size. Since such high strength concrete is vulnerable to fire and has various problems for the safety of residents, the importance of fire resistance performance of high strength concrete is increasing day by day. Accordingly, the Ministry of Land, Transport and Maritime Affairs has established the "Fire Resistance Performance Standard for High Strength Concrete Columns / Beams" to ensure that the concrete structures with a strength of 50 MPa or more are required to have the main reinforcing bar temperature of 538 ℃ on average and 649 ℃ or less within the prescribed time in case of fire. The fire resistance performance test of the structure is also required to be carried out in accordance with KS F 2257 (1-9) (Rules Revision on Standards for Evacuation and Fire Protection of Buildings, Ministry of Land, Transport and Maritime Affairs, 2008). As one of methods to overcome the problems of high-strength concrete related to fire, a method of preventing internal explosion by mixing various organic fibers in concrete to reduce the internal vapor pressure, but it is deteriorated in construction performance and repair after fire I have a problem with difficulty. In addition, this method is not economically effective because it is applied to all parts of the concrete structure. Therefore, in order to directly improve the fire resistance of high-strength concrete, a method that can directly block heat from the site where the high-strength concrete receives heat due to fire is more efficient.

In the beginning of the domestic slope-shaped formwork, when converting the wooden structure to the concrete structure in the 1970's restoration of cultural assets, PCs with various members were converted into PCs of 30mm thick, 300-500mm wide, and 3m long on the roof rafters. After manufacturing and installing, it is the first to reinforce the reinforcing bar on the upper part and cast concrete on the inclined roof, and there are many applied buildings such as Gwanghwamun and Youngchumun.

In 1998, Kim Woo-jae researched the properties of mortar with fine aggregate, glass fiber, and SBR latex in an experimental study on the mortar's properties for the development of slope type dies. In the study (focusing on column and beam member application), fire resistance test was carried out (60 minutes) based on KS F 2257-1 with coating thickness of 20mm and 40mm.

Overseas, most studies on slope formwork are being carried out in Japan, where topping concrete is placed on large unit formwork, precast column and half precast method on columns, and large unit formwork and partial precast members on beams. The integrated method is used. In the case of Germany, unlike Japan, on-site casting is mainly used to separate walls and slabs by using large formwork. The wall adopts a large slab slab method using a large table slab or slab, and the staircase uses a factory-made precast staircase almost at all sites.

As such, advanced countries in Japan and Europe are pursuing a systemic method that allows construction to be easily carried out with only a few skilled workers and a simple labor force, by assembling the parts produced at the factory with machines.

As the demand for artificial aggregates increases due to the difficulty of supplying natural aggregates, the development and manufacture of artificial lightweight aggregates based on fly ash or blast furnace slag, which are industrial by-products, are increasing. Accordingly, studies on lightweight aggregate and lightweight aggregate concrete have been actively conducted. In particular, recent studies on securing fire resistance of building materials using lightweight aggregate have been conducted according to the high strength of concrete. Has been made.

In 1978, Japan used nine types of rock aggregates, including lightweight aggregates, to investigate the thermal properties of concrete. (在 取 一 男, 各種 巖 質 の 骨材 ゑ 用 い た コ ン ク リ ト ト 熱 的 性質, Yukiri Tech Co., 20-11, Vol 20., 1978).

In Korea, in an experimental study on the properties of insulating concrete using artificial lightweight aggregates in 1994, Kim's pore structure influenced the thermal insulation of concrete, and lightweight aggregate using plastic expanded clay had better insulation properties than general aggregates. (Yu-Jae Kim, an experimental study on the characteristics of insulating concrete using artificial lightweight aggregate, master's thesis, Konkuk University Graduate School, 1994), Song-Hun in 2004, reviewed the relationship between heating temperature and concrete porosity. The relationship between the pore structure and the high temperature in concrete including concrete was presented (Songhoon, examining the relationship between heating temperature and concrete porosity, Proceedings of the Architectural Institute of Korea, Vol.24 No.2, 2004), 2006 In 2005, the characteristics of light aggregate aggregates under high temperature conditions were discussed. (Hun, Song, Structural Characteristics of Structural Lightweight Aggregate Concrete, Proceedings of the Korea Concrete Institute, Vol. 18 No.1, 2006).

The present invention has been made by the necessity of the above, an object of the present invention is to provide a lightweight fire-resistant slope formwork that can be applied to high-strength concrete.

Another object of the present invention is to provide a lightweight fire resistant mortar having fire resistance.

In order to achieve the above object, the present invention provides a composition for the slope type formwork, characterized in that it comprises 10 to 15% by weight of the gypsum in the lightweight refractory slope type formwork composition.

In one embodiment of the present invention, the lightweight refractory non-deformable formwork composition is preferably a binder: fine aggregate volume ratio of 1: 1.5 to 1: 2, but is not limited thereto.

In another aspect, the present invention provides a method for producing a lightweight fire-resistant slope formwork, characterized in that 10-15% by weight of the gypsum is added in the method for producing a lightweight fire-resistant slope formwork.

In one embodiment of the present invention, the lightweight refractory slope formwork composition is preferably a binder: fine aggregate volume ratio of 1: 1.5 to 1: 2, but is not limited thereto.

Accordingly, the present invention mixes gypsum into lightweight mortar using a light aggregate containing a large amount of voids as fine aggregate, to derive the optimum formulation of lightweight refractory mortar for slope type formwork that can be applied to high-strength concrete, and through fire resistance experiments The purpose is to evaluate the fire resistance performance of lightweight fire resistant mortar.

The present invention is intended to analyze the strength characteristics and fire resistance by incorporating gypsum into lightweight mortar using light weight aggregates as a study on the lightweight form mortar for slope formwork. For this purpose, the theoretical data on slope formwork, high-strength concrete properties under high temperature conditions, and theoretical studies on refractory methods were compared and analyzed. In addition, as a basic test for use as a lightweight refractory mortar for slope type dies, the flow, viscosity and board bending strength, compressive strength, and adhesive strength tests of mortar are carried out to check changes in physical properties and strength characteristics. And through the fire test to determine the temperature history of the structure in the case of fire, to verify the fire performance of the lightweight refractory mortar for the slope type formwork.

To this end, the present invention proceeds as shown in FIG. 1, and the scope and method of the present invention are as follows.

1) Property and strength test of light weight refractory mortar for slope type dies

Formulations were selected through preliminary experiments, and the mortar compressive strength, board flexural strength, slump flow, viscosity test, bond strength test, and thermal conductivity test were performed.

2) Fire resistance test of light weight refractory mortar for slope type dies

The fire resistance performance test was carried out by applying 70MPa class high strength concrete to the test specimens made of lightweight fire-resistant mortar beforehand to determine the temperature rise distribution and the explosion.

Hereinafter, the present invention will be described.

First, the type and characteristics of the formwork will be described.

1) Steel panel foam

One of the systemic formwork is also called "Eurofoam". It is a modular form developed for the purpose of improving productivity and reducing the number of materials by reducing manpower by assembling without deforming standard formwork.

2) gang form

Gangfoam is a formwork system that installs and dismantles small pieces of formwork without any assembly, disassembly and large size. It is a large wall formwork that mainly manufactures and uses exterior wall formwork and formwork installation and dismantling work and CAGE for plastering and decorating scaffolding in the same section structure of upper and lower planes as in high-rise apartments.

3) flying form

Formwork for placing concrete on the floor, also known as "table form".

It is a formwork made of formwork plate, joist, yoke, support, etc. in one piece.

4) climbing form

As a formwork for wall, it is used to assemble formwork and scaffolding for wall finishing work integrally and lift it at once. It is a formwork that manufactures scaffolding for installing formwork on gang form and scaffolding for finishing work of concrete first poured. Recently, the necessity is increasing as the high-rise building is constructed with a tube structure using concrete due to the high-rise and large-scale building.

5) slip form

The slip foam method is also called a sliding foam method. In order to construct a horizontally or vertically repeated structure in a uniform shape without construction joints, concrete is poured while continuously moving the formwork to construct the structure.

6) Tunnel form

It is a formwork that can be installed and dismantled at a time by integrally manufacturing wall formwork and slab formwork in order to enable concrete pouring of walls and floors at the time of constructing wall reinforced concrete structure. It is also applied to round tunnels or drainage culverts in civil engineering.

7) Traveling form

After placing concrete in one section by moving formwork supported by movable frame, the concrete is continuously poured while lowering the formwork and moving the formwork to the next concrete placing section. Formwork applied to horizontally continuous structures.

8) tie-less formwork

If it is difficult to install wall formwork on both sides, it is difficult to install form tie and it may cause water leakage when welding the form tie iron to the mother pile of the earth wall. The formwork method for solving this problem is a formless tie formwork. It is also called a "brace frame method" using a brace frame to support lateral pressure without using a form tie.

9) tie-less formwork

It is a method that uses wavy bone slate as formwork and is mainly used for underground beams. Although the material is relatively inexpensive and easy to handle, the volume of concrete is somewhat lost due to the wavy slates.

10) tie-less formwork

The metal lass formwork method is mainly used in underground beams as a method to shorten the dismantling process and reduce manpower even though the formwork is left without dismantling the formwork. In particular, it is easy to cope with the shape of curved surface, but when used for the part to avoid the rust caused by the exposure of metal lath or the part that needs to be finished, the surface is mortar coated.

11) Reinforcement Formwork

Among the basic composition of formwork consisting of formwork plate, joist, reinforcement, support and other accessories, it is a steelless formwork that can be assembled with only joist by integrating the functions of joist and reinforcement into one. Formwork system that simplifies assembly and disassembly of formwork by increasing the cross section and rigidity of joist wire to replace reinforcement.

12) Plain formwork

When placing concrete on the floor formwork, the work load and the concrete weight are burdened by the supporter. Solid formwork is a system for constructing floor formwork without support, and the truss-shaped beam is laid over the formwork or wall formwork and the bottom plate formwork is constructed.

13) air tube formwork

In general, a rubber balloon is used as a formwork for a structure having a circular interior. It is installed and disassembled with the air pressure removed, so it can be easily and quickly used for underground drains and domes.

As used herein, the "slope-shaped formwork" is to manufacture the precast formwork using inorganic materials in the factory to improve the shortcomings of the general formwork used in the concrete casting process only in the field, do not demoulding after concrete casting Say. There are two types of manufacturing process: fixed type and field type. In some sites, a temporary factory is installed in the site to produce and process the members. However, in most cases, a product is manufactured in a separate stationary factory and transported to a site by a vehicle.

The purpose of use of the slope type die used in the present specification is as follows.

Formwork during construction work is a temporary material for placing concrete. Most of the existing formwork is demoulded when certain required strength is secured after concrete is poured. When the formwork is classified by material, there are wood, steel, plywood, plastic, fiber, and the like, and recently, formwork using special materials has been developed and used. In particular, Nawang, the main material of wood formwork, which is widely used, is causing depletion of forest resources due to increased usage. Existing wood formwork is economically weak in strength and durability when the number of times of conversion is low or when the form is complicated. After the formwork is installed, dismantling work is required, and a large amount of construction waste materials are generated, and noise and vibration are generated during formwork.

Steel formwork is a formwork that is widely used in recent years. The concrete finished surface is clean, the rigidity and thermal conductivity are high, but the initial investment is excessive, and the construction speed is slow because the assembly, disassembly, and transportation of members depend on manpower. It is sensitive and difficult to process in the field, and the dismantling work is necessary. Plywood formwork has the disadvantages that the finished surface of concrete is clean, the installation speed is faster than wood, and the workability and utility are good, the water resistance is insufficient, the surface of the plywood is fragile and easily damaged, and requires dismantling. Plastic formwork is easy to handle because it is lightweight, so it can be used a relatively large number of times, but it is weak to shock and heat, and has a disadvantage in that it is restricted in use. The lath formwork which improves the disadvantages of the conventional formwork uses a special material called Libras instead of plywood.The combination of copper materials and wood is fixed with attached hardware, and then concrete is placed, which does not require dismantling compared to conventional formwork. On the other hand, in the early concrete curing in Korea, China and West China, special care is required for temperature control, and construction is not possible in places where rust is a concern. Therefore, considering the advantages and disadvantages of existing formwork, the slope formwork method, which can reduce air, reduce manpower, reduce cost, reduce noise and vibration, and protect nature, is a useful method.

As used herein, "high strength concrete" The demand for high-strength concrete is increasing as society demands on buildings. Such high-strength concrete manufacturing method generally has a method of increasing the strength using the admixture and a method of manufacturing by lowering the water-binder ratio (W / B) by using a chemical admixture such as a high performance water reducing agent.

The definition of the strength range of high strength concrete has changed to this day with the development of materials and processes. The US specified the range of high-strength concrete above 41 MPa in ACI Commitee 363, while Japan specified 36-120 MPa in specification JASS 5, and broadly defined the range of high-strength concrete. The UK mandates over 40 MPa in BS 8110.

In Korea, the strength range of high-strength concrete is 28 days old, general aggregate concrete is 40MPa or more, lightweight concrete is 27MPa or more. In addition, it is a fire resistant regulation of concrete concrete in Korea, and it is announced that concrete structures with a compressive strength of 50MPa or higher on the 28th should be 538 ℃ on average and less than 649 ℃ in average within a prescribed time in case of fire.

In addition, the physical properties of high-strength concrete under high temperature conditions are as follows.

High-strength concrete generally exhibits the properties of elastic materials under low temperature conditions, but under high temperature conditions, it exhibits properties of plastic materials according to changes in the hydrated composites (C-S-H, Ca (OH) 2, etc.) of cement paste. The mechanical properties of high-strength concrete at high temperatures are known to be affected by the water-binder ratio (W / B), aggregate form, moisture content, and porosity. When the high-strength concrete receives heat, the bound water in the cement matrix begins to evaporate, resulting in the water evaporation of hydration products such as CSH hydrate, ethrinzite, mono sulfate, aluminate, and alkalinity of the concrete above about 500 ° C. Ca (OH) 2, a typical hydrate, is expanded and decomposed to neutralize concrete.

Table 1 shows the deterioration process of concrete with temperature.

The mechanical properties of high strength concrete under high temperature conditions are as follows.

1) decrease in compressive strength

The strength of high-strength concrete affected by high temperature condition decreases the concrete's performance simultaneously with the change of thermal stress in the concrete. In concrete, which is a composite of various materials, aggregates expand under high temperature conditions, and at the same time, the cement hydrate shrinks around 100 ° C., and thus the magnetostrictive stress is generated due to its heterogeneity. Due to this magnetostrictive stress, microcracks increase in the interior of concrete, thereby reducing the overall compressive strength of high-strength concrete. In addition, the compressive strength is also affected by aggregates, and even in the case of ordinary strength concrete, the strength of aggregates decreases from room temperature to 480 ℃ regardless of the type of aggregates.In particular, silica-based aggregates show that the strength decrease after 480 ℃ is greater than that of other aggregates. It has been reported.

2) decrease in elastic modulus

The modulus of elasticity refers to the initial elastic deformation slope corresponding to 1/3 or 1/4 of the stress-strain curve in the compressive strength test. The modulus of elasticity of high-strength concrete at high temperature decreases with increasing temperature, and the factors influencing this are known as aggregate and cement matrix. In concrete, water vapor vaporizes around 200 ° C to form voids, and the deformation recovery capacity is drastically reduced. Thereafter, at 600 ° C., the cement paste of the concrete, aggregate, and the adhesion strength between the cement paste and the aggregate are lowered, thereby reducing the elastic modulus.

3) stress-strain curve

The stress-strain curve of high-strength concrete under normal conditions rapidly reaches the maximum stress compared to the normal strength concrete and appears to be a sharp drop after the maximum stress. When heat is applied, the normal strength concrete shows the characteristics of the plastic material after reaching the maximum stress at 200 at the characteristic of the elastic material up to 100 ℃, while the high strength concrete shows the characteristics of the elastic material up to 200, but at 300 ℃ or higher. It is reported that the properties of the plastic material, and because the residual strength after the maximum stress is less than that of ordinary strength concrete, it may be more dangerous as a structure.

The explosion of high strength concrete is as follows.

When the high-strength concrete is exposed to high temperature conditions due to a fire, some of the concrete structures fall off in the form of cracks and debris. The type and moisture content of the concrete, the type of aggregate and the size and temperature rise pattern of the structure, and reinforcement It can be caused by various factors such as Eure. In addition, the concrete under high temperature conditions, the explosion appears in various forms of destruction according to the mechanism of occurrence, the fracture form can be represented by subdividing as shown in Table 2.

Table 2 is a table showing the concrete fracture mode under high temperature conditions according to the mechanism.

1) crack

The crack is an initial phenomenon in which the expansion and contraction of heat inside the concrete under high temperature conditions and the chemical change of the symene hydrate occurs, mainly from the surface and corners, and continuously occurs in a fire.

2) Downfall

Exfoliation is a phenomenon in which a portion of concrete fragments are continuously dropped due to chemical degradation and internal cracking of cement cement in concrete, which occurs when concrete reaches a certain temperature at which chemical degradation occurs. When the temperature is higher than 300 ℃, concrete causes thermal expansion, which causes dehydration, which causes shrinkage inside the concrete and internal stress. And when the temperature is above 500 ℃, the concrete structure starts to neutralize in earnest. At a temperature of 573 ° C, a sudden change of the SiO2 series proceeds and starts to decompose at 900 ° C. In addition, cement hydrates are also affected. At temperatures between 450 and 550 ° C., calcium-based hydrates including calcium hydroxide (Ca (OH) 2) begin to decompose, leading to full-scale deterioration of concrete. Delamination is caused by the dehydration and decomposition of cement hydrate due to the chemical deterioration of concrete, resulting in a decrease in strength and modulus of elasticity and falling below the bond strength as part of the structure.

3) pop-out

The popout phenomenon occurs mainly on the surface of the concrete structure in the early stage of fire, and is caused by the difference in specific heat between cement matrix and aggregate or semantic matrix and reinforcing bars. In the concrete under high temperature condition, thermal expansion and contraction phenomenon occurs. When this simultaneous behavior occurs, cracks occur at the interface of each material, and at the same time, popout phenomenon occurs due to this stress difference.

4) explosion

The mechanism by which the explosion occurs is largely divided into water vapor and thermal stress snow. The water vapor snowfall is a sudden temperature change at the surface of the concrete under high temperature conditions, resulting in a supersaturated void pressure called "moisture clog", and the pressure inside the concrete If the rate of steam generation is faster than the discharge rate, explosive explosion of concrete occurs. This explosion occurs especially in high-strength concrete, because the structure is so dense that internal water increase is difficult to move, resulting in tensile stresses exceeding tensile strength by vapor pressure.

On the other hand, the thermal stress theory expands as concrete members are heated under high temperature conditions, but members such as columns and beams are constrained at both ends, so that the temperature difference between the surface parts of the concrete members increases, causing stress. New Year

In recent years, it has been convincing that this is caused by the combination of two mechanisms that cause such explosions.

Next, the fire resistance performance reinforcement method of high strength concrete is described.

Types of fireproof performance reinforcement

Refractory performance reinforcement method of the high-strength concrete can be divided into a method of incorporating organic fibers into the water vapor pressure reduction method in the concrete, a method of preventing explosion scattering, and a fireproof coating method, surface layer temperature suppression coating method as shown in FIG.

The method of incorporating organic fibers for the purpose of reducing the internal water vapor pressure of the method of FIG. 3 is deteriorated in the workability of the concrete and applied to the entire structure, ambiguous economic efficiency and difficult to repair and reinforce after the fire. In addition, the method of preventing explosion scattering is also not easy to satisfy the fire resistance required for high-strength concrete structure in addition to the effect of preventing scattering. Fireproof coating method to suppress the temperature rise of the surface layer can directly block the concrete from the heat caused by the fire, but there is a disadvantage that requires an additional process.

On the other hand, it is an advantage that the non-deformable formwork is excellent in fire resistance like a fireproof coating method and does not have any additional process.

Surface temperature rise suppression method

Although the material of the surface temperature rise suppression method varies depending on the use, it will be described below with respect to the gypsum and lightweight aggregate material of the slope type formwork used in the present invention.

1) plaster

The chemical component is CaSO4, which forms ridges or columnar crystals, and is a monocyte-like fibrous form. The hardness is 2 and the density is 2.2-3.0 depending on the number of crystals. It is mainly used as a mixture of cement, fertilizer and white pigment. Gypsum has a variety of forms according to the amount of crystallized water, and the types and characteristics of gypsum according to the change of the crystallized water are shown in Table 3.

(1) Isu plaster

Isu plaster is the general state of gypsum and is produced in nature or as a by-product of the chemical industry. Since it does not cure even when water is added, it is used by producing half water or anhydrous gypsum by wet or dry heating and reacting with water.

(2) Half gypsum

Hemihydrate gypsum is also known as hydrated gypsum, and has a chemical formula of CaSO 4? 1 / 2H 2 O. When the dihydrate gypsum is heated to 80-140 ° C. to evaporate 3/4 of the crystallized water, hemihydrate gypsum in powder form can be obtained. When water is kneaded with half water gypsum, it becomes the original dihydrate gypsum (CaSO4? 2H2O) containing 2 molecules of crystallized water, and when it hardens, volume expansion occurs. In addition, hemihydrate gypsum can vary in strength depending on the amount of water. Hemihydrate gypsum is divided into α type and β type, while α type can obtain great strength with less water, while β type is relatively hard to obtain large strength regardless of the amount of water. In the cement mortar or gypsum mortar using semi-hydrated gypsum, the modulus phenomenon in which the strength expression rate decreases for a certain period of time at early ages and then rises to long-term ages occurs.

(3) anhydrous gypsum

Anhydrous gypsum has the chemical formula CaSO4 and is classified into type I, type II, and type III according to the composition. It is soluble in hydrochloric acid in transparent or translucent fibrous form. In addition, when water is absorbed, it becomes semi-hydrated gypsum.

Gypsum produced in Korea is not a natural gypsum but is mainly a chemical gypsum and is produced as a by-product during the manufacturing process of phosphate fertilizers in fertilizer factories. Gypsum has 20 ~ 30% of its internal weight as crystal water, and when the temperature rises above 120 ℃, the water is released and becomes half or anhydrous. Due to this action, the endothermic amount is very large in the early stage of fire, which shows excellent fire resistance. Gypsum also prevents instant freezing when mixing cement and water and affects the strength and dry shrinkage of the hardened cement.

2) lightweight aggregate

Lightweight aggregate is for the case of concrete weight reduction and an improvement in heat insulating properties to the aggregate used for the purpose of unit mass in the KS F 2534 structural lightweight aggregate is fine aggregate 1,120 kg / m is less than ^{3, the} coarse aggregate defined to be less than 880kg / m ^3, and have. In addition, KS F 1004 concrete terminology defines aggregates of less density than ordinary aggregates.

Natural lightweight aggregates are volcanic rocks that can be obtained from nature by volcanic action, or processed products that have been crushed to adjust their size. Natural lightweight aggregate is a porous structure with volatilization by volcanic action, and it is open pores and is often used for low quality concrete aggregate.

Busan lightweight aggregate is used as concrete aggregate by adjusting the particle size of industrial by-products such as expanded slug or coal ash. Artificial lightweight aggregate is manufactured by firing at high temperature with shale, clay, slate, pearlite, fly ash, industrial by-products as main raw materials.

Artificial lightweight aggregates can be divided into crushed lightweight aggregates crushed raw materials such as shale and clay, and crushed lightweight aggregates pulverized into raw materials, and granulated lightweight aggregates assembled by extrusion molding or ferretizer. In some cases, the two materials are mixed in a predetermined ratio. Minerals after firing are called expanded shale, expanded clay, calcined fly ash and the like. In recent years, lightweight aggregates processed from waste glass or foamed styrofoam are also manufactured.

In general, lightweight aggregates are known to exhibit lower thermal conductivity than ordinary aggregates and thus have excellent thermal insulation and fire resistance. The reasons for this are summarized in two. The first is that lightweight aggregate itself has relatively more voids than ordinary aggregates, and thus has low thermal conductivity, and is thus reported to have excellent fire resistance since it can prevent the explosion phenomenon due to a large amount of voids. Second, because the lightweight aggregate itself is calcined and manufactured at high temperature, it shows relatively stable properties even when exposed to high temperature. Aggregates affected by fire are damaged, and when light aggregates are used, they are more stable at relatively high temperatures, which may be advantageous to fire resistance than ordinary aggregates.

As such, the lightweight mortar using lightweight aggregate having heat insulation, fire resistance, and light weight exhibits different thermal characteristics from those of ordinary mortars. The thermal conductivity of mortar is affected by the compounding ratio, strength, aggregate, water content, etc., and the smaller the density of mortar and the smaller the amount of unit cement, the smaller the mortar. The thermal conductivity is generally the highest in the wet state at room temperature, because the voids in the aggregate are filled with moisture to increase the thermal conductivity.

In general, the thermal conductivity of aggregates containing a large amount of voids is low, and the smaller the independent voids contained in the aggregate, that is, the closer to the open pore structure, the lower the thermal conductivity because of free movement of moisture in the voids.

The thermal conductivity of lightweight mortar is determined by the voids inside the aggregate. This is due to the multi-pore structure of the lightweight aggregate, which is why the thermal insulation performance is lowered when the pore of the lightweight aggregate is absorbed. In addition, the thermal conductivity of lightweight mortar is closely related to the density. Generally, as the density increases, the thermal conductivity tends to increase proportionally. Therefore, considering the difference in density between ordinary mortar and light mortar, it is common that the thermal conductivity of light mortar is about 55% lower than that of ordinary mortar.

The present invention as an experimental study on the lightweight refractory mortar for the slope type formwork, the following conclusions were obtained through the basic physical properties test, adhesion strength test and fire resistance test of lightweight refractory mortar.

1) The slump flow of lightweight refractory mortar, which can confirm the workability of light weight refractory mortar for slope type formwork, increased with increasing gypsum incorporation rate. In the mixing ratio 1: 1.5 and 1: 2, the gypsum incorporation rate was slightly decreased when the gypsum incorporation rate was 15%. The light refractory mortar viscosity was found to be inversely proportional to the slump flow.

2) The higher the blending ratio, the higher the gypsum incorporation rate, the lower the unit volume mass. The decrease in the unit volume mass was more affected by the increase in the blending ratio than the increase in the gypsum incorporation ratio. The compressive strength of the lightweight fire resistant mortar and the board flexural strength, which can determine whether the formwork is able to withstand the lateral pressure of the cast concrete, decreased as the mixing ratio increased.

The strength increase rate was relatively more affected by the gypsum incorporation rate than the compounding ratio, and the gypsum-free mixture showed a rapid increase in strength expression rate at the early stage of age, but the expression rate decreased as the age was reached. On the contrary, the gypsum-incorporated formulation showed a relatively low intensity expression rate in the early stages of aging, but the gradation of the intensity development was slow.

3) The adhesion strength of lightweight refractory mortar is an experiment to investigate the adhesion relationship between pour concrete and slope formwork when constructing slope formwork. All 8 of 8 formulations planned in this study are 0.12MPa The above results were satisfied and generally proportional to the compressive strength.

The thermal conductivity was able to determine the fire resistance performance, and six of the eight formulations, 75% of which were satisfied with the standard value of 0.093W / m ~ K or less, and the thermal conductivity decreased with increasing the mixing ratio and the gypsum mixing ratio.

4) In the refractory test of light weight refractory mortar for slope type dies, explosion occurred in 4 specimens, which is 50% of 8 specimens. The first specimen to be exploded was the specimen with a mixing ratio of 1: 1.5 gypsum mixing rate of 0%, and the average temperature of the main reinforcing bar was average among the "High Strength Concrete Column / Beam Fire Retardant Performance Standards" published by the Ministry of Land, Transport and Maritime Affairs. Satisfying the following criteria at 538 ° C and up to 649 ° C.

As a result of analyzing the strength, physical properties, and fire resistance of the lightweight refractory mortar including the gypsum of the present invention through the present invention, it was confirmed that the present invention can be utilized as a slope form.

1 shows a flowchart of the present invention;
2 is a graph showing the stress-strain curve of various concrete;
3 is a table showing the types of fire resistance reinforcement scheme;
Figure 4 is a photograph showing the microstructure of the light fine aggregate;
5 is a photograph showing the microstructure of the plaster;
Figure 6 is a photograph showing the thermal conductivity and adhesion strength experiment;
7 is a photograph showing the board bending strength test;
8 is a graph showing the slump flow according to the gypsum incorporation rate;
9 is a graph showing the unit volume mass according to the gypsum incorporation rate;
10 is a graph showing the viscosity according to the gypsum incorporation rate;
11 is a graph showing the adhesive strength according to the gypsum incorporation rate;
12 is a graph showing the thermal conductivity according to the gypsum incorporation rate;
13 is a graph showing the compressive strength according to the gypsum incorporation rate;
14 is a graph showing the board bending strength according to the gypsum mixing ratio;
15 is a diagram showing the details of the high-strength concrete test specimen and the thermocouple position for the refractory test;
Figure 16 is a photograph showing the production of high-strength concrete specimen formwork for fire resistance testing.
17 is a graph showing the standard time-temperature heating curve of KS F 2257;
18 is a photograph showing a furnace interior and a data logger;
19 is a graph showing a compounding history of 1: 1.5 gypsum incorporation rate of 0% of the specimen temperature history;
20 is a graph showing a compounding ratio of 1: 1.5 gypsum incorporation rate of 5% of the specimen temperature history;
FIG. 21 is a graph showing a compound temperature history of 1: 1.5 gypsum incorporation rate 10%;
22 is a graph showing the compound temperature history of 1: 1.5 gypsum incorporation rate 15% specimen;
23 is a graph showing a compounding ratio of 1: 2 gypsum incorporation rate of 0% of the specimen temperature history;
24 is a graph showing a compounding history of 1: 2 gypsum incorporation rate of 5% of the specimen temperature history;
25 is a graph showing a compounding history of 1: 2 gypsum incorporation rate 10% of the specimen temperature history;
FIG. 26 is a graph showing a compound temperature history of 1: 2 gypsum incorporation rate 15%.

The present invention will now be described in more detail by way of non-limiting examples. The following examples are intended to illustrate the invention and the scope of the invention is not to be construed as being limited by the following examples.

In the present invention, the ordinary cement of the S company product (please specify the specific company) that satisfies the KS L 5201 specification , its physical properties and chemical properties are shown in Tables 4 and 5.

Table 4 is a table showing the physical properties of the cement.

Table 5 is a table showing the chemical properties of the cement.

Aggregate used in the present invention is a lightweight aggregate aggregate produced in Spain having a particle diameter of 4mm or less and has an open pore structure. Mortar using lightweight aggregate with open pore structure generally has lower thermal conductivity than mortar using lightweight aggregate with closed pore structure. This is because the closed lightweight aggregate contains a large amount of moisture in the aggregate voids even after the mortar curing, and because the moisture contained in the interior voids after drying, the mass change during the drying of the mortar shows a high thermal conductivity. On the other hand, lightweight aggregate having an open pore structure has a small change in mass even after drying because the moisture inside the aggregate easily escapes during curing of the mortar during drying, resulting in a small change in thermal conductivity. Therefore, it is considered that the open lightweight aggregate used in this experiment is more advantageous than the closed lightweight aggregate in terms of fire resistance and thermal barrier properties.

The physical property test of lightweight fine aggregates used in the present invention was carried out according to the density and water absorption test method of KS F 2529 structural lightweight aggregates, the sifting test method of KS F 2502 coarse aggregate and fine aggregates, and the unit mass test method of lightweight concrete for KS F 2462 structure. The results are shown in Table 6.

division density
(g / cm ³⁾ Absorption rate (%) Assembly rate Unit volume mass
(kg / m ³ ) Spain 0.81 17.33 4.56 487

Table 6 is a table showing the physical characteristics of the light fine aggregate.

The gypsum used in the present invention is a building-type hemihydrate gypsum produced by domestic company C (please specify a specific company) , and the physical properties are shown in Table 7.

density
(g / cm ³⁾ moisture
(%) Powder
(cm ² / g) Condensation (min) # 170
Passage
(%) 2 hours
Expansion rate
(%) 1 day
Wet strength
(kgf / cm ² ) First closing 2.95 0.07 1,367 7 16 88 0.38 250

Table 7 shows the physical properties of gypsum.

Fly ash (F / A) uses Youngheung thermal acid and its physical and chemical properties are shown in Table 8.

density
(g / cm ³⁾ Powder
(cm ² / g) Ignition loss
(%) Compressive strength ratio
(%) moisture
(%) SiO ₂
(%) 2.2 3,368 2.50 89 0.04 46.80

The water used as the blended water in the present invention uses a clean enough to be suitable for the beverage. If water containing harmful amounts of oil, acid, alkali, corrosive substances, etc. is used, there is a fear that cement condensation and hardening are lowered or the durability of concrete is lowered. Therefore, the water used in the present invention used tap water in accordance with the standard of the building construction standard specification.

Example

design

The present invention relates to a light-weight fire-resistant mortar for slope type dies through preliminary experiments (cement: fine aggregate) Please make sure that the volume ratio ( )) is set to 1: 1.5, 1: 2, respectively. When the compounding ratio exceeded 1: 2, more cement paste was needed, which led to an increase in the water-binder ratio (W / B), thereby lowering the strength.

In addition, the gypsum incorporation rate was limited to 15% or less, and a total of eight formulations were planned by setting the incorporation rate to 0%, 5%, 10%, and 15%. The experimental factors and the experimental compound table are shown in Table 9 and Table 10, respectively.

Item factor level Combination
Element Compounding ratio (B: S) 2  1: 1.5, 1: 2 Gypsum mixing rate (%) 4 0, 5, 10, 15 Experiment
matters Unconsolidated Mortar Experiment 3 Slump flo
Unit volume mass
Viscosity Hard Mortar Experiment 4 Adhesion strength
Thermal conductivity
Compressive strength
Board bending strength

Compounding cost
(B: S) Gypsum mixing rate
(%) Weight compounding (kg / m ² ) F / A water cement Fine aggregate gypsum One 1: 1.5 0 86.0 293.0 767.69 343.60 0.00 5 86.0 293.0 731.00 343.60 43.00 10 86.0 293.0 688.00 343.60 86.00 15 86.0 293.0 645.00 343.60 129.0 2 1: 2 0 75.0 277.5 675.00 390.15 0.00 5 75.0 277.5 637.50 390.15 37.50 10 75.0 277.5 600.00 390.15 75.00 15 75.0 277.5 562.50 390.15 112.5

Experimental Example

1) Mortar Test

 (1) slump flow experiment

The slump flow experiment was conducted according to KS L 5111 "Cement Test Flow Table".

 (2) Unit volume mass test of mortar

The unit volume mass test of the mortar that is not hardened is carried out by filling the sample in three portions of one-third of the sample in a container according to the method specified in KS F 2409 "Method for testing unit volume mass and air volume of unconsolidated concrete". Each time the sample was filled with a stick 25 times evenly and the last time to fill overflowing and evenly chopped, using a compaction rod to flatten the surface and weigh the sample.

 (3) mortar viscosity test

In order to directly measure the viscosity of mortar, the viscosity of the mortar was measured using a rotary viscometer having a viscosity measuring range of 0.3 to 4000 dPa · s and a rotation speed of 62.5 rpm. In the measuring method, the rotary rotor is rotated by inserting the rotary rotor in the center of the sample to be measured. At this time, when the scale of a viscometer indicated the constant scale, the scale was read and the viscosity was measured. The average value was obtained by measuring three times per sample.

2) Hard Mortar Experiment

(1) Bonding strength and thermal conductivity test

The bond strength and thermal conductivity test of mortar was conducted in accordance with KS F 3513 "Adhesive strength test for light aggregate finish coating material and thermal conductivity test standard". The performance standards of the coating material specified in this standard are shown in Table 11. Bond strength test was carried out by applying 40x40x5mm of lightweight refractory mortar on a flat mortar surface of 70x70x20mm and curing the jig with epoxy on the mortar surface. Thermal conductivity experiment was carried out by molding a specimen of 200x200x25mm and curing in a constant temperature and humidity chamber at a temperature of 20 ± 3 ℃ and a humidity of 80% or more for 24 hours, then curing in water at a temperature of 20 ± 2 ℃ for 5 days, and then again at a temperature of 20 ± 2 The experiment was carried out after curing for 21 days in a thermo-hygrostat at 50 ° C or higher humidity.

Experiment item Adhesion Strength (MPa) Thermal Conductivity (W / mk) Reference value 0.12 or more 0.093 or less

(2) compressive strength test

The compressive strength test method of KS L 5105 hydraulic cement mortar was carried out. For the mortar compressive strength test, a 50x50x50mm square iron mold was put into a cube with a thickness of about 25mm and 32 times with four wheels for about 10 seconds. After the mortar is uniformly chopped into the mold, pour 25 mm thick again and push the mortar on the upper surface of the mold with a trowel. Then, with the trowel, cut the flat surface at right angles to the length of the mold. The experiment was carried out by fabrication.

(3) board bending strength test

The test was carried out according to the bending test method of KS F 2263 building boards, and the test was performed by making test specimens of 200x150x30mm for each compound.

The experimental results of the light weight refractory mortar for gypsum-formed formwork are shown in Table 12.

Compounding cost Gypsum mixing rate (%) Slump flo
(mm) Viscosity
(dPa? s) unit
mass
(kg / m ³ ) Compressive strength
(MPa) Board flexural strength
(MPa) Paint ash experiment 3 days 7 days 14 days 28 days 3 days 7 days 14 days 28 days Thermal conductivity
(W / mK) Adhesion strength
(MPa) 1: 1.5 0 316 80 1512.9 20 23 25 27 4.94 7.81 8.1 9 0.106 2.11 5 317 80 1507.7 19.3 21.3 23 25 4.35 7.42 7.68 8.2 0.092 1.2 10 321 70 1504.0 13 15.4 18 19 4.33 6.09 6.63 7.2 0.088 0.75 15 320 50 1503.0 12 13 15 16.5 4.01 5.76 6.36 6.87 0.082 0.64 1: 2 0 317 80 1485.3 17 23.6 24.5 26 3.82 6.37 6.50 6.9 0.098 1.74 5 318 65 1460.6 14.3 16.7 18 19 3.46 6.2 6.21 6.7 0.089 1.3 10 319 65 1432.8 10.6 12.5 13 14.5 3.06 6.07 6.37 6.68 0.083 1.2 15 318 60 1430.1 11.6 12.7 14 15.5 2.95 5.56 5.27 5.57 0.078 1.07

Unconsolidated Mortar Experiment

1) Slump Flow Experiment

The slump flow of lightweight fire resistant mortar, which can confirm the constructability of light weight fire resistant mortar for slope formwork, was generally increased as the gypsum incorporation rate increased. In the mixing ratio 1: 1.5, 0.32% increased at 5% and 1.26% at 10%, but decreased slightly to 0.31% at 15% of gypsum mixture. Appeared to decrease. In the mixing ratio 1: 2, the mixing ratio increased by 0.32% ㎥ at 5% and 0.31% at 10%, but decreased by 0.31% at the gypsum mixing rate of 15%. It is believed that as the level increases, the slump flow decreases.

2) Unit volume mass test of mortar

The unit volume mass of the lightweight refractory mortar was in the range of 1,430.1 ~ 1512.9kg / ㎥, the compounding ratio 1: 1.5 averaged 1506.9kg / ㎥, and the compounding ratio 1: 2 averaged 1452.2kg / ㎥. The bulk mass also decreased, with a decrease of 3.62% between 1: 1.5 and 1: 2. In addition, the unit volume mass decreased as the gypsum mixing ratio increased, but the average 1499.1kg / ㎥ at 0% mixing ratio and 1466.5kg / ㎥ at 15% mixing ratio increased to 2.17%. Appeared to be small.

3) Mortar viscosity test

As a result of the viscosity test of the light refractory mortar, the viscosity was generally inversely proportional to the slump flow. As the gypsum incorporation rate increased, the viscosity decreased by 20.5% on average at the ratio of 1: 1.5 and 13.2% on average at 1: 2.

Hard Mortar Experiment

1) Bonding strength test

The adhesive strength of the light weight mortar for slope form was in the range of 0.64 to 2.11 MPa, and all were destroyed between the ground surface and the mortar. In addition, all 8 formulations satisfied the adhesion strength criterion of 0.12 MPa or more, and tended to be proportional to the compressive strength of lightweight refractory mortar.

Adhesion strength generally decreased as the blending ratio increased. At 1: 1.5, the average was decreased by 31.8% with increasing gypsum incorporation ratio, and at 1: 2, the average was decreased by 14.6%. In particular, the ratio of strength of plain and gypsum mixed with 5% was 43.1%, and the difference of strength between plain and gypsum mixed with 5% was 25.3%. The reason is that the initial strength decreases when gypsum is mixed.

2) Thermal Conductivity Experiment

The thermal conductivity of the light weight mortar for slope form was in the range of 0.078 ~ 0.106W / m? K, and 6 of the 8 formulations, 75% of which satisfied the thermal conductivity criteria of 0.093W / m? K or less. Thermal conductivity decreased with increasing gypsum incorporation and mixing ratio. The thermal conductivity decreased by 8.12% on average at the mixing ratio of 1: 1.5 and 7.31% at the mixing ratio of 1: 2.

Based on the above test results, it is considered that some of the fire resistance can be secured through the mixing of gypsum, and it is expected to show excellent fire resistance performance when using lightweight aggregates with a large amount of voids.

2) compressive strength

The 28-day compressive strength of the lightweight form fire-resistant mortar for slope form was in the range of 15.5 ~ 27MPa, and the average ratio was decreased by 14.2% at 1: 1.5. In the mixing ratio 1: 2, the gypsum incorporation ratio was 26.9% at 5% and 23.7% at 10%. Overall, the compressive strength of lightweight refractory mortar decreased due to the increase of the mixing ratio. In addition, the compressive strength tended to decrease as the gypsum mixing ratio increased.

The expression rate of the compressive strength showed a tendency of rapid intensity expression at the early age of the gypsum-free blended formulation, but the expression rate decreased as the age of aging increased. As a result, the intensity expression rate gradually increased with age. This is because the initial expression rate is low due to the effect of gypsum coagulation control during the initial coagulation due to the influence of gypsum, but the strength expression rate is continuously increased.

3) Board flexural strength test

On the 28th, the board whip strength of the lightweight refractory mortar, which can determine whether the slope formwork can withstand the lateral pressure of the cast concrete, was in the range of 5.57 ~ 9MPa.

At the ratio of 1: 1.5, the average was 8.6%, and at 1: 2, the average was 6.5%. As with the compressive strength, the board flexural strength decreased as the mixing ratio increased and as the gypsum mixing ratio increased. In terms of the expression rate of the intensity, the ratio of 1: 1.5 and 1: 2 showed a rapid intensity expression rate at the early age of the age, but the expression rate tended to decrease with age.

Slope  Fire resistance test of lightweight fireproof mortar for formwork

This experiment is to investigate the fire resistance performance of lightweight fireproof slope formwork mortar.A total of eight specimens were applied by applying 70MPa-class high-strength concrete to a 30mm-thick test specimen prepared in advance using eight combinations of lightweight fireproof slope form mortar. After fabricating the temperature history inside the test body was grasped.

1) Fireproof thermocouple installation

In order to fabricate high-strength concrete specimens for fire resistance tests, thermocouples were installed inside the specimens. As shown in FIGS. 15 and 16, two 75-size spacers made of mortar are installed on the floor, and 0 mm (surface temperature), 10 mm, 20 mm, 30 mm, 40 mm, and 50 mm height from the bottom of the spacer. After each of the grooves having a depth of about 10mm, 6 thermocouples were inserted to insert a total of 12 thermocouples per specimen.

2) 70MPa class high strength concrete specimen

In order to prepare 500 high-strength concrete specimens for fire resistance experiments, the following materials were used and the formulation was planned.

(1) cement

The cement used in this experiment is Class 1 ordinary portland cement from S Company that satisfies KS L 5201.

(2) fine aggregate

The fine aggregate used in this experiment was Incheon Washing sand, and its properties were tested according to the specific gravity and water absorption test method of KS F 2504 fine aggregate and the unit mass test method of KS F 2505 aggregate, and the results are shown in Table 13.

division density
(g / cm ³⁾ Absorption rate (%) Assembly rate Unit volume mass
(kg / m ³ ) Incheon Sansa 2.6 1.03 2.57 1,613

 (3) coarse aggregate

The coarse aggregate used in this experiment was crushed stone of 25mm or less, and its physical properties were tested according to the density and water absorption test method of KS F 2503 coarse aggregate and the unit mass test method of KS F 2505 aggregate, and the results are shown in Table 14.

division density
(g / cm ³⁾ Absorption rate (%) Assembly rate Unit volume mass
(kg / m ³ ) broken stone 2.65 0.84 7.12 1,594

 (4) water

Using water containing harmful oils, acids, alkalis, corrosive substances, etc. as a blended water will reduce the coagulation and hardening of cement, adversely affect the coagulation hardening, workability and the development of strength, and the durability of concrete or mortar. There is a risk of deterioration. Therefore, the water used in this experiment was used tap water according to the standard of building construction standard and concrete standard.

 (5) fly ash (F / A)

Fly ash used Yeongheung thermal power mountain.

 (6) silica fume

Silica fume was used in Canada, and the physical and chemical properties are shown in Table 15.

density
(g / cm ³⁾ Powder
(cm ² / g) SiO ₂
(%) Al ₂ O ₃
(%) Fe ₂ O ₃
(%) MgO
(%) CaO
(%) SO ₃
(%) 2.2 200,000 90 1.5 3.0 2.0 0.7 0.2

 (7) high performance water reducing agent

As the admixture used in this experiment, a polycarboxylic acid-based high performance sensitizer is shown in Table 16.

division chief ingredient Appearance color Remarks High Performance Supervisor Polycarboxylic acid system Liquid bitumen -

 (8) Blending high strength concrete specimens and designing experiments

For the production of 60MPa-class concrete specimens, high-strength concrete specimens were prepared by the following formulation. In addition, in order to grasp the characteristics of the high-strength concrete specimens, test specimens were prepared and subjected to the physical properties shown in Table 18.

G _max
(mm) W / B
(%) S / a
(%) Mass mix (kg / m ³ ) water cement Fly ash Silica fume Fine aggregate Coarse aggregate 25 29.5 37 187.8 490 97.8 48.9 533.9 926.5

Experiment item Experimental Method Unconcrete concrete slump -KS F 2401 Sampling Method of Unconsolidated Concrete
-Slump test method of KS F 2402 concrete Air volume -Air volume test method of concrete not hardened by KS F 2421 pressure method Hard concrete Compressive strength -Method of manufacturing specimens for strength test of KS F 2403 concrete
-Compressive strength test method of KS F 2405 concrete

2) fireproof test

In order to measure the fire performance, the fire resistance test was carried out by pouring high-strength concrete on a lightweight fire-resistant slope form mortar specimen. The refractory test method is difficult to analyze the pure reaction furnace according to the depth of the specimen under the existing four-side heating conditions. Therefore, one-sided heating is advantageous for heating high-strength concrete to high temperature and at the same time accurately understanding the pattern of explosion and temperature history by depth. This possible furnace was used.

(1) heating conditions

The heating conditions of the refractory test furnace were heated for 180 minutes according to the standard time-heating temperature curve of the fire resistance test method of KS F 2257 building member. The standard time-heating temperature curve is shown in FIG. 17.

(2) How to measure

0mm (surface temperature), 10mm, 20mm, 30mm inserted in the spacer of the left and right sides of the specimen to measure the internal temperature history of the high-strength concrete to know the fire resistance performance of the lightweight refractory slope form mortar test specimen in which high-strength concrete was poured. The temperature values of the thermocouples for each 40 mm and 50 mm thickness were collected using a data logger, and the average values of the left and right thermocouples were recorded as the internal temperature of the specimens. In addition, every 10 minutes after the heating of the specimen was observed for cracking and cracking, after the end of the experiment was observed whether the occurrence of explosion.

Experiment Results and Analysis

High strength concrete Experiment

Properties of 70MPa class high strength concrete for fire resistance test are shown in Table 19. The 28-day compressive strength of the concrete specimens was 78 MPa, indicating a target strength of 70 MPa or more.

Slump (mm) Air volume (%) Compressive strength (MPa) 7 days 14 days 28 days 180 1.4 42 53.4 78

Compounding ratio 1: 1.5 Gypsum mixing rate  0% test body

The results of the fire resistance test are shown in Table 20 below.

Lightweight refractory mortar Mixing ratio 1: 1.5 Gypsum mixing rate 0% Test specimen-temperature after 180 minutes heating thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃)   917.5 768.6 231.6 222.6 149.7 109.8 100.4 Occur 40 minutes 120 minutes
Temperature
(℃) 104.5 1025 905.2 877.4 777.7 674.9 467.5 180 minutes
Temperature
(℃) 1097 1086 1027 987.4 925.9 855.2 692.6

The refractory test temperature history of this test body is shown in FIG. Particular surface explosion occurred from 40 min of experiment time, furnace temperature of 889 ℃ and surface temperature of 150 ℃, "moisture clog" occurred, and excessive depth explosion with severe noise occurred with increasing heating time. This experiment showed that the specimen failed to exhibit fire resistance for more than 3 hours.

Compounding ratio 1: 1.5 Gypsum mixing rate  5% test body

Refractory test results are shown in Table 21 below.

Lightweight refractory mortar compounding ratio 1: 1.5 Gypsum mixing rate 5% Test specimen-temperature after 180 minutes heating thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 78.4 92.1 54.3 43.6 32.7 28.1 Occur 100 minutes 120 minutes
Temperature
(℃) 1046 540.8 247.9 313.3 233.6 119.1 141.9 180 minutes
Temperature
(℃) 1097.6 1098.2 744.3 729.2 714.3 547 602

The refractory test temperature history of this test body is shown in FIG. Experimental time 100 minutes The surface moisture was generated from the furnace temperature of 1000 ℃ and the surface temperature of 146 ℃, and the "moisture clog" was discharged. Over time, deep explosion occurred, and the test specimens were not able to exhibit fire resistance over 3 hours.

Compounding ratio 1: 1.5 Gypsum mixing rate  10% test body

The refractory test results are shown in Table 22 below.

Lightweight refractory mortar Mixing ratio 1: 1.5 Gypsum mixing rate 10% thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 111.7 100.1 83.1 73.9 61.8 53.9 Occur
Never - 120 minutes
Temperature
(℃) 1046 242.9 209.5 149.8 134.5 112.3 100.9 180 minutes
Temperature
(℃) 1097.6 358.2 301.1 246.2 220.3 184.5 160.1

The refractory test temperature history of this test body is shown in FIG. The specimen had an internal temperature history of less than 358.2 ° C. at full thickness for 180 minutes of the experiment, and no explosion occurred. This proved that the performance of the main reinforcing bar of the structure meets the criteria of 538 ℃ on average and less than 649 ℃ at maximum among the "Fire Resistance Performance Management Standards of High Strength Concrete Columns / Beams" announced by the Ministry of Land, Transport and Maritime Affairs.

Compounding ratio 1: 1.5 Gypsum mixing rate  15% test body

The results of the refractory test are shown in Table 23 below.

Light weight refractory mortar Mixing ratio 1: 1.5 Gypsum mixing rate 15% Test temperature-180 minutes after heating thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 143 137.8 107.8 94.1 95.3 62.9 Occur
Never - 120 minutes
Temperature
(℃) 1046 297.7 265.1 217.7 144.1 122.7 100.3 180 minutes
Temperature
(℃) 1097.6 417.4 386.3 329.2 262.8 231.7 195.3

The fire resistance test temperature history of this test body is shown in FIG. The specimen had an internal temperature history of 343.8 ° C. or less at full thickness for 180 minutes of the experiment, and no explosion occurred. This proved that the performance of the main reinforcing bars in the structure satisfies the average of 538 ℃ and below the maximum of 649 ℃ among the "High Fire Resistant Performance Standards".

Formulation ratio 1: 2 Gypsum mixing rate  0% test body

Refractory test results are shown in Table 24 below.

Lightweight refractory mortar Mixing ratio 1: 2 Gypsum mixing rate 0% Test specimen-Temperature after 180 minutes heating thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 71.9 59.9 51.6 41.9 34.9 26.8 Occur 82 minutes 120 minutes
Temperature
(℃) 1046 1010.4 989.8 1000.2 1007.4 798.5 617.3 180 minutes
Temperature
(℃) 1097.6 1079.5 1072.5 1081.3 1082.9 984.9 897.2

The refractory test temperature history of this test body is shown in FIG. From 82 min of experiment time, furnace temperature of 983 ℃ and surface temperature of 147 ℃, "moisture clog" occurred along with partial surface phenomena. Excessive depth blasting with severe noise occurred with increasing heating time. This experiment showed that the specimen failed to exhibit fire resistance for more than 3 hours.

Formulation ratio 1: 2 Gypsum mixing rate  5% test body

Refractory test results are shown in Table 25 below.

Lightweight refractory mortar Mixing ratio 1: 2 Gypsum mixing rate 5% Test specimen-temperature after 180 minutes heating thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 97.7 84.9 72.2 59 46.6 38 Occur 131 minutes 120 minutes
Temperature
(℃) 1046 197.9 164.1 144.5 124.7 104.6 93.3 180 minutes
Temperature
(℃) 1097.6 899.7 839.1 751.4 704.4 609.9 406.4

The fire resistance test temperature history of this test body is shown in FIG. Partial popout occurred at 131 min, furnace temperature 1058 ℃ and surface temperature 227 ℃, after which the popout area continuously increased and excessive depth bursting with noise occurred. It is estimated that "moisture clog" has accumulated and burst at once. This experiment showed that the specimen failed to exhibit fire resistance for more than 3 hours.

Formulation ratio 1: 2 Gypsum mixing rate  10% test body

Refractory test results are shown in Table 26 below.

Light weight refractory mortar Mixing ratio 1: 2 Gypsum mixing rate 10% thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 118.5 92.1 77.8 67.5 58.7 49.7 Occur
Never - 120 minutes
Temperature
(℃) 1046 252.8 179.9 115.2 101.6 101 101.4 180 minutes
Temperature
(℃) 1097.6 343.5 271.1 218.8 187.9 163.9 148.6

The fire resistance test temperature history of this test body is shown in FIG. The specimens exhibited an internal temperature history of less than 343.5 ° C at full thickness for 180 minutes, with no explosion. This proved that the performance of the main reinforcing bars in the structure satisfies the average of 538 ℃ and below the maximum of 649 ℃ among the "High Fire Resistant Performance Standards".

Formulation ratio 1: 2 Gypsum mixing rate  15% test body

Refractory test results are shown in Table 27 below.

Light weight refractory mortar compounding ratio 1: 2 Gypsum mixing rate 15% thickness
(mm) Furnace 0 10 20 30 40 50 Explosion
The presence or absence Explosive 60 minutes
Temperature
(℃) 917.5 108.2 97.9 83.5 71.3 63.1 52.9 Occur
Never - 120 minutes
Temperature
(℃) 1046 231.3 188.1 148.4 127.8 104.4 100.7 180 minutes
Temperature
(℃) 1097.6 315 281.6 236.5 198.7 176.7 154.6

The refractory test temperature history of this test body is shown in FIG. The specimens exhibited an internal temperature history of less than 315 ° C at full thickness for 180 minutes, and no explosion occurred. This proved the fire resistance performance as the main reinforcing bar temperature of the structure meets the criteria of 538 ℃ and up to 649 ℃ below the "Fire resistance management criteria for high strength concrete columns / beams" announced by the Ministry of Land, Transport and Maritime Affairs.

Claims (4)

A light weight fireproof slope formwork composition comprising 10 to 15% by weight of gypsum in the light weight fireproof formwork composition. The light weight fireproof slope formwork composition of claim 1, wherein the light weight refractory formwork composition has a binder: coarse aggregate volume ratio of 1: 1.5 to 1: 2. A light weight fireproof slope formwork manufacturing method, characterized in that 10-15% by weight of gypsum is added. The method of claim 3, wherein the lightweight refractory slope formwork composition is a compounding ratio of a binder: fine aggregate of 1: 1.5 to 1: 2, characterized in that the light weight refractory slope formwork.

Images