KR20030088608A - Recycled aggregate for base course material of pavement - Google Patents

Abstract

PURPOSE: An aggregate for a roadbed material using reclaimed constructional waste is provided to obtain the physical properties needed for a roadbed and to prevent the environmental pollution. CONSTITUTION: The reclaimed aggregate for a roadbed material is characterized in that the particle diameters of the aggregate are distributed such that the percent ratio of the particles passing through a sieve of 50.8 mm size is 100%, that of the particles passing through a sieve of 38.1 mm size is 75-100%, that of the particles passing through a sieve of 19.1 mm size is 55-70%, that of the particles passing through a sieve of 9.53 mm size is 40-60%, that of the particles passing through a sieve of 4.75 mm size is 25-45%, that of the particles passing through a sieve of 2.00 mm size is 15-30%, that of the particles passing through a sieve of 0.425 mm size is 5-20% and that of the particles passing through a sieve of 0.075 mm size is up to 10%, and in that the aggregate has the bearing value of the subgrade soil of 20-40% and the resilient modulus of 1.5-5 Mpa.

Description

Recycled aggregate for base course material of pavement}

The present invention relates to recycled aggregates for roadbed materials, and more particularly, to produce recycled aggregates from waste concrete generated at a construction site, and to appropriately select a blending ratio for each particle size distribution, thereby satisfying required physical properties as roadbed materials. It relates to a recycled aggregate for the material.

In modern society, the amount of waste concrete, which is a kind of construction waste due to urban redevelopment, improvement of living environment and aging of buildings is increasing rapidly due to economic growth and improvement of people's life. However, until now, most of the waste concrete has not been recycled and has been reliant on landfilling, and even in the case of landfill, most of the construction wastes generated at the construction site due to landfill shortages, huge transportation and disposal costs are illegally landfilled, dumped and incinerated. It has been dealt with improperly, resulting in increased environmental destruction and pollution of living environment and causes various complaints.

In addition, the government's environmental regulations are being strengthened through the wave of the Green Round (GR), which focuses on the establishment of environmental standards of global standards and the regulation of various products and industries that do not meet those standards. Therefore, the generation of waste concrete, which is gradually accelerated along with the reconstruction and redevelopment projects, is required to establish measures in terms of resource recycling as well as to prevent environmental pollution, and it is urgent to improve the recycling efficiency of construction wastes. In particular, since about 70% of the current construction waste generated is waste concrete, it can greatly solve the construction waste disposal problem if it can be recycled.

Unlike Korea, which relies on simple landfill to process such construction by-products, advanced foreign countries recognized the importance of recycling from early on and accumulated a lot of research and recycling experience in this field. Korea has only recently begun to pay attention to this, but the results are minimal. Construction by-products are inherently harmless and have a high rate of recycling, but their technical value is not so high. In particular, the recycling of waste concrete is particularly important because of its high added value and high demand.

The reason for maximizing the recycling of waste concrete is first, the supply shortage of aggregates due to the depletion of domestic natural aggregate resources due to the massive construction work since the 1990s. If the current demand for natural aggregates is on the rise, the value of about 4 billion tons of stored value is only about 10 years. In particular, if the national natural environment protection law is announced and the government policy that natural aggregate is preserved as a resource is enforced, the aggregate supply conditions will be worse. Second, construction waste is hampering redevelopment projects. Even if the redevelopment permit has already been received, the problem is serious in that the redevelopment project may be delayed or abandoned without the precondition of disposal of construction waste. As such, the development of waste concrete recycling technology is desperately needed in Korea in terms of improving the added value of recycled aggregates, preventing environmental pollution, and saving aggregate resources.

Construction wastes are wastes from construction, civil engineering and dismantling of construction structures, including earth and sand, waste concrete, waste asphalt concrete, sludge (sludge), wood chips, paper, metals, waste plastics, waste glass, waste ceramics. And the like. Under the current Korean law, the types of construction waste are not classified in detail, but according to the Waste Management Act, most of construction waste belongs to general waste, and some of waste such as paint, waste oil and asbestos are classified as specific waste. Construction wastes subject to recycling under the Promotion Act are three types of designated by-products: earth and sand, waste concrete, and waste asphalt concrete. Looking at the specific contents of the construction waste generated at the construction site as shown in Table 1.

Figure 1 illustrates the relationship between the waste terms generated at the construction site. As shown in FIG. 1, some of the waste generated at the construction site may be classified as designated designated by-products for recycling, and some may be classified as designated wastes or household wastes that do not recycle, and appropriate separation thereof is required.

On the other hand, according to the US EPA (1998) data, by-products of construction and dismantling are defined as waste materials produced during the construction, repair, or dismantling of structures. Structures here include roads and bridges and buildings of all types (residential or non-residential).

In general, in Korea, construction wastes are often discharged in a mixed state of scum, waste concrete, waste asphalt concrete, construction sludge, wood chips, paper, metals, waste plastics, waste glass, and waste ceramics. Construction wastes, unlike domestic wastes and industrial wastes from manufacturing, are not constant in waste generation, have a large amount of emissions, and have a wide variety of wastes. In addition, due to the various subcontracting structure, there are various waste handlers, and many kinds of wastes are often discharged in a mixed state. Therefore, in Korea, even accurate statistics on the construction status of construction wastes are not secured. Based on the waste statistics reported by the cities and provinces based on the Waste Management Act, the Ministry of Environment publishes the national waste generation and disposal status as data every year. have.

Table 2 below shows <97 national waste generation and treatment status>.

The total waste generated in Korea in 1997 was 189,200 tons / day (6,960,000 tons per year), 93,528 tons / day (49.4%) for workplace waste, 47,895 tons / day (25.3%) for construction waste and 47,777 tons / day for construction waste. (25.3%). Total waste generation increased by 7.9% compared to the 1996 level, and construction waste increased 68.1% year-on-year, which was the main reason for the increase in waste. However, the rate of recycling of construction wastes has soared every year. In 1994, the recycling rate soared from 8.0% to 76.6% in 1997, while the landfill rate fell from 90.7% in 1994 to 20.4% in 1997.

This high recycling rate is due to the fact that construction wastes can be recycled in bulk, covering materials, etc. However, construction waste is mostly used as a simple road fill after crushing, and technology development that can be used as concrete aggregates to increase added value is inadequate. Therefore, research and development are needed to utilize recycled aggregates as concrete aggregates.

The present invention is to solve the problems of the prior art as described above, the object of the present invention, by producing recycled aggregate from the waste concrete generated at the construction site, by setting the mixing ratio of the recycled aggregate by particle size distribution strictly, It is to provide a recycled aggregate for the roadbed material satisfying the required physical properties as the roadbed material.

Figure 1 illustrates the relationship between the waste terms generated at the construction site.

Figure 2 schematically shows a process for producing recycled aggregate used in the present invention.

3A to 3C show the compounding ratios of the average particle size distributions of the samples prepared according to Examples 1 to 3 of the present invention, respectively, and FIG. 3D shows the compounding ratios of the average particle size distributions of the above embodiments.

Figure 4 is a flow chart showing a physical property test procedure for the recycled aggregate prepared in accordance with an embodiment of the present invention.

5 is a block diagram of a repeatable load M _R tester system used in the present invention.

Figure 6 shows the triaxial cell and load and displacement measurement position of the repeated loading M _R tester system used in the present invention.

Figure 7 shows the load and strain relationship in the cyclic M _R test.

8a to 8c show the M _R test results for the recycled aggregate prepared according to Examples 1 to 3 of the present invention, respectively.

In order to achieve the above object, the recycled aggregate for the roadbed material according to the present invention is a recycled aggregate for use as a roadbed material, the particle size of the recycled aggregate is 50.8mm size body weight percentage of 100%, 75-100% of the size of the passage through the size of 38.1 mm, 65-80% of the weight of the passage through the size of 25.4 mm, 55-70% of the weight of the passage of the size of the body with 19.1 mm, 55% to 70% of the passage of the body of 9.53 mm This 40-60%, the size-through weight percentage of 4.75 mm is 25-45%, the size-through weight percentage of 2.00 mm is 15-30%, the size-through weight percentage of 0.425 mm is 5-20%, 0.075mm It has a blending ratio of the particle size distribution having a transit weight of 10% or less, the subgrade soil bearing capacity ratio of the recycled aggregate is 20% to 40%, and the recovery modulus of elasticity is 1.5 to 5MPa.

In addition, the recycled aggregate for the roadbed material according to the present invention is a recycled aggregate for use as a roadbed material, the particle size of the recycled aggregate, 100% of the weight passing through the body size of 38.1mm, percentage of the weight passing through the body size of 25.4mm The 80-100%, the percentage of passage through the size body of 19.1mm is 65-90%, the percent of passage through the size of body is 50-75%, and the percent of passage of the body size of 35-65%, 2.00mm is 4.75mm It has a mixing ratio of particle size distribution of 25 to 50% of the size of the sieve through weight, 5 to 30% of the size of the passing sieve of 0.425 mm, 15% or less of the size of passing through the sieve of 0.075 mm, The bearing capacity ratio is 20% to 40%, and the recovery modulus of elasticity is 1.5 to 5 MPa.

The recycled aggregate for the roadbed material according to the present invention is a recycled aggregate for use as a roadbed material, wherein the particle size of the recycled aggregate has a size of 25.4 mm in size passing weight of 100% and 19.1 mm of size in passing weight of 80%. ~ 100%, 9.53mm size sieve weight percent 60-85%, 4.75mm size sieve weight percent 45-75%, 2.00mm size sieve weight percent 30-60%, 0.425mm size 15% to 35% sieve weight percentage, 0.075 mm size sieve weight ratio of 15% or less, having a mixing ratio by particle size distribution, subgrade soil bearing capacity ratio of the recycled aggregate is 20% to 40%, recovery elastic modulus of 1.5 ~ 5MPa It is characterized by that.

Since the 1980s, efforts have been made to utilize recycled concrete aggregates as road bases, auxiliary bases and concrete aggregates in various countries in the US and Europe. Although some road pavement works in Korea have been used as base and auxiliary bases using recycled concrete, the construction performance is very low compared to the superiority of recycled concrete aggregate. This is due to the lack of research on the performance ratio test data and field measurement data of recycled aggregates, as well as the mixing ratios of particle size distribution of recycled aggregates that can satisfy the physical properties required for use as roadbed materials.

In the present invention, the following research process was performed to set the mixing ratio of the particle size distribution of the optimum aggregate for roadbed materials.

1) Grasp the material characteristics (specific gravity, water absorption, etc.) of the recycled aggregate

2) Analysis of particle size analysis results of existing road auxiliary layer soil material

3) Analysis of Subgrade Soil Bearing Capacity (CBR) of Existing Road Auxiliaries

4) Mixing design of recycled aggregate of concrete (more than 3 times)

5) Confirmation of compaction, physical properties and particle size of each ingredient

6) Indoor CBR value analysis of each compound

7) Resilient Modulus Test of Optimum Compound (Resiliant Modulus, hereinafter referred to as 'M _R ')

The recycled coarse aggregate used in the present invention for the characterization of recycled aggregates during the process was taken from the hazelnut environment of a joint research company in Jeonju city.

Figure 2 schematically shows a process for producing the recycled aggregate.

In the characterization experiments of the recycled aggregates of coarse aggregates produced through the crushing, washing and sorting processes as shown in FIG. 2, the aggregates were passed through a sieve having a size of 30 mm and remained in No. 4 (# 4). Used natural sand. At this time, impurities harmful to the coarse aggregate such as brick, asphalt, glass, artificial stone, tile, paper, and wood were removed as much as possible with the naked eye.

In general, the specific gravity of fine aggregate is usually about 2.5 to 2.65, the specific gravity of coarse aggregate is usually about 2.55 to 2.70. The assembly rate of fine aggregate and coarse aggregate is about 2.3 to 3.1 and 6 to 8, respectively. As shown in Table 3, the specific gravity and water absorption of the recycled coarse aggregate used in the present invention is relatively higher than the coarse aggregate, and the assembly rate is good. In addition, the limit of wear reduction rate of coarse aggregate by Los Angels tester should be less than 40%, but according to standard specification of pavement concrete 4.5.5, even coarse aggregate with more than 35% wear reduction ratio satisfies the strength of concrete with the selected mix ratio. If you got it, you may use it. In addition, according to ASTM C-33 of the American Society for Testing and Materials, aggregates can be used in concrete products if the wear loss percentage does not exceed 50%, and the British Standard (BS) (88,1201 Part 2, 1973). ) Aggregates can be used if the surface wear does not exceed 45%.

Hereinafter, the structure and the effect of the present invention will be described in more detail with reference to Examples and Experimental Examples. The following Examples and Experimental Examples illustrate the content of the present invention, but the content of the present invention is not limited thereto.

Example 1: Particle Size Mixing Test of Recycled Aggregate

Using the recycled aggregate produced in the hazelnut environment, the maximum aggregate size was 50.8 mm, and a recycled aggregate having a blending ratio according to particle size distribution was prepared as shown in Table 4 below.

Example 2: Particle Size Mixing Test of Recycled Aggregate

A maximum aggregate size was 38.1 mm, and a recycled aggregate having a blending ratio according to particle size distribution was prepared as shown in Table 5 below.

Example 3: Particle Size Mixing Test of Recycled Aggregate

A maximum aggregate size was 25.4 mm, and a recycled aggregate having a blending ratio according to particle size distribution as shown in Table 6 was prepared.

Figures 3a to 3c shows the mixing ratio of the particle size distribution of the samples prepared according to Examples 1 to 3 of the present invention, respectively. In addition, Figure 3d shows the mixing ratio of the average particle size distribution of the above embodiments. In the figure, the solid line shown on the outside of the graph showing the compounding ratio for each particle size distribution of the embodiments is a line indicating the particle size limit of the material (dirt) used as the roadbed.

As described above, with respect to the recycled aggregates of Examples 1 to 3 blended to satisfy the standards required as the road auxiliary base layer and subgrade soil material of the concrete recycled aggregates, the physical property test such as particle size test and specific gravity test, as well as the optimum water content ratio Compaction test to obtain the CBR test, and repeated loading M _R test was performed according to the respective mixing ratio, the procedure is shown in the flow chart shown in FIG.

Experimental Example 1 CBR Test

Quality characteristics of the roadbed of the Korea Expressway Corporation are shown in Table 7.

It can be seen that the CBR test measurement value of the recycled aggregate prepared in the mixing ratio according to the particle size distribution according to Examples 1 to 3 can be utilized as a furnace body or a road material as 30% -40%. However, it may be desirable to perform further reviews, such as quality stability and on-site CBR testing, for use as auxiliary base material.

Experimental Example 2: M _R Test

The package receives the wheel load repeatedly as the vehicle travels. Therefore, rather than applying general mechanical properties (elastic modulus) to pavement design, pavement design analysis method using pavement properties determined under repeated loading condition is more reasonable and economical. There is a recovery modulus of elasticity (M _R ) as a material property of the material which shows the stress-strain relationship with respect to the repeated lubrication loads received by each pavement layer.

In 1986, the AASHTO revised design method introduced M _R according to the AASHTO T 274 test in the pavement design method for determining the design thickness of the entire pavement layer and the relative thickness of each pavement layer, and M _R is defined by Equation 1 below.

M _R = σd / εR

Where σd is the repetitive axial stress (kg / cm 2) and εR is the axial recovery strain.

Factors affecting the M _R characteristics include water content, density and compaction characteristics, freezing, melting, and particle size distribution. For example, it is influenced by the change of the water content according to the season after construction. In general, as the water content increases, the M _R value decreases. In addition, the water content has a great influence on the M _R characteristics of the granular granules for viscous, subgrade soils of fine grained soils and high base and subbases of fine grained soils. And at the same saturation degree, M _R value becomes large, so that compaction degree is large. This is related to the compaction characteristics of each pavement and subgrade soil at the construction stage. On the other hand, seasonally repeated freezing and thawing have a great influence on the M _R characteristics of fine clay. Even if a constant water content is maintained, the M _R value of the viscous fine grains is remarkably decreased by repeated freezing and thawing.

In general, it is known that there is no clear correlation between soil type and M _R characteristics distinguished by the unification classification method. However, if the same size having a distribution of particulate soil composed of angular particles (angularity) M _R value is larger and smaller than the value _R M when having a particle size of a dense material having a loose distribution of the particle size distribution.

The repeated loading M _R tester used in this Experimental Example 2 is a VJ-Tech (UK) and Instron (USA) product and consists of a load frame including triaxial cells, restraint stress load device, signal processing and system control device. Both stress control and strain control are possible. The configuration of the tester system is shown in FIG. 5, and the triaxial cell and the load and displacement measurement positions are shown in FIG. 6. The test material is 100 mm in diameter cylindrical.

There has been much discussion about where to measure the axial strain in a repeatable M _R tester (Pezo, 1991). AASHTO T294-82, the initial specification for the repeated loading M _R test method, proposed both an internal strain measurement method using a clamp and an external strain measurement method using two LVDTs mounted outside the triaxial cell.

In the repeated loading M _R test, the stress state induced on the package due to the lubrication load is simulated, and a load of a harversine shape is loaded for 0.1 second as shown in FIG. By repeatedly loading the sequential stress of a certain period, the strain response as shown in FIG. 7 (b) is obtained. If this is represented by the stress-strain relationship, the result as shown in FIG. 7 (c) can be obtained, and the recovery elastic modulus (M _R ) is determined therefrom.

Disregarding the difference in the load waveform, the semi-sinusoidal load for 0.1 s in the cyclic M _R test can be considered equivalent to the upper part of the 5 ㎐ sine load used in the torsional shear test. Therefore, the load frequency at which the repeated loading M _R test is performed can be assumed to be 5 kHz.

As a result of the M _R test, the examples showed excellent physical properties of 2.0 to 3.5 MPa, and these measurements are shown in FIGS. 8A to 8C (Examples 1 to 3, respectively). At this time, the restraint stress was 69 kPa, which gave a general restraint pressure.

In addition, other test results showed no change in particle size due to impact, such as compaction.

As described above, in the present invention, the mixing ratio of the optimum particle size distribution of the recycled aggregate for the roadbed material satisfying the physical properties including the CBR and M _R test results required as the roadbed material was presented.

Therefore, the recycled aggregate for roadbed materials according to the present invention can be utilized as a roadbed material such as a furnace body, a roadbed material, and an auxiliary base material.

Claims (3)

As recycled aggregate to be used as roadbed material, The particle size of the recycled aggregate, 100% of the size of the passage through the size of 50.8mm, 75% to 100% of the weight of the passage through the size of 38.1mm, 65-80% of the size of the passage through the size of 25.4mm, 65 to 80%, 55-70% of the size of the penetrating weight of the size, 40-60% of the size of the penetrating weight of the 9.53 mm, 25-45% of the size of the penetrating weight of the 4.75 mm, 15- of the size of the weight of the penetrating body of 15.00 mm It has a blending ratio of particle size distribution of 30%, 0.425mm sized body weight percentage of 5-20%, 0.075mm sized body weight of 10% or less, The subgrade soil bearing capacity ratio of the recycled aggregate is 20% to 40%, and the recycled aggregate for roadbed materials, characterized in that the recovery modulus of 1.5 ~ 5MPa. As recycled aggregate to be used as roadbed material, The particle size of the recycled aggregate, 100% of the weight of the passage through the size of 38.1mm, 80% to 100% of the weight of the passing through the size of 25.4mm, 65-90% of the weight of the passing through the size of 19.1mm, of 65 to 90% 50-75% of the size of the penetrating weight of the size, 35-65% of the weight of the penetrating weight of the 4.75mm, 25-50% of the size of the weight of the penetrating body of the 2.00mm, 5-5 of the size of the weight of the penetrating body of 0.425mm It has a compounding ratio by particle size distribution with a weight of 30% and a body size of 0.075 mm of 15% or less The subgrade soil bearing capacity ratio of the recycled aggregate is 20% to 40%, and the recycled aggregate for roadbed materials, characterized in that the recovery modulus of 1.5 ~ 5MPa. As recycled aggregate to be used as roadbed material, The particle size of the recycled aggregate, 100% of the weight of the passage through the size of 25.4 mm, 80-100% of the weight of the passage of the size of 19.1 mm, 60-85% of the size of the passage of the size of 9.53 mm, of 4.75 mm 45-75% of the size of the passage of the size of the body, 30-60% of the weight of the passage of the body of 2.00 mm, 15-35% of the size of the passage of the body of the body size of 0.425 mm, and 15% of the size of the passage of the body of 15 size of 0.075 mm Having a compounding ratio by particle size distribution, The subgrade soil bearing capacity ratio of the recycled aggregate is 20% to 40%, and the recycled aggregate for roadbed materials, characterized in that the recovery modulus of 1.5 ~ 5MPa.