KR-102960931-B1 - Concrete Composition for Drainage Pipes Using Recycled Aggregate

Abstract

The present invention relates to a concrete composition for water pipes utilizing recycled coarse aggregate and steel slag coarse aggregate. To solve the problems of natural aggregate shortage and environmental destruction, concrete with excellent performance and an eco-friendly nature was developed using recycled aggregate. The concrete composition of the present invention comprises 460 kg of blast furnace slag fine powder Type 2 cement, 140 kg of water, 705 kg of recycled coarse aggregate, steelmaking slag coarse aggregate, and fine aggregate, and 9.2 kg of a high-performance water reducer. A key feature is that the steelmaking slag coarse aggregate is substituted at a weight ratio of 20% to 50% relative to the total coarse aggregate. The water-to-binder ratio is 30.4%, and the fine aggregate ratio is 42%. Steel slag coarse aggregate has physical properties of a density of 3.37 g/cm³, a fineness modulus of 6.97%, and an absorption rate of 0.87%, and contributes to the improvement of concrete strength due to its higher density compared to general aggregates. Recycled coarse aggregate exhibits excellent quality with a density of 2.55 g/cm³, a fineness modulus of 6.48%, and an absorption rate of 0.58%. Experimental results showed that compressive strengths of 37.2 MPa were achieved with 20% replacement, 38.4 MPa with 30% replacement, 41.4 MPa with 40% replacement, and 40.5 MPa with 50% replacement, all satisfying the GR F 4035 quality standard of 35.0 MPa. After steam curing at 85 degrees for 6 hours, a strength of 40.4 MPa to 44.8 MPa was observed, making it suitable for precast products. In terms of durability, it maintains 35.0 MPa or higher after 100 freeze-thaw cycles, and the flexural strength ranges from 5.6 MPa to 6.3 MPa. In particular, the optimal balance of compressive strength, flexural strength, and durability was achieved in a 40% substitution blend. The present invention reduces the use of natural aggregates through the recycling of waste resources, achieves a carbon dioxide reduction effect of approximately 34.5 kg per 1 m³, and enables an 11% reduction in material costs. Therefore, it is a practical technology that simultaneously secures eco-friendliness and economic efficiency.

Inventors

• 길현만

Assignees

• (주) 주안기업

Dates

Publication Date

20260507

Application Date

20251023

Claims (1)

1. In a concrete composition for water pipes utilizing recycled aggregate, Per 1 m³, it comprises 460 kg of Type 2 blast furnace slag cement, 140 kg of water, 630 kg to 650 kg of recycled coarse aggregate, 440 kg to 500 kg of steelmaking slag coarse aggregate, 705 kg of fine aggregate, and 9.2 kg of high-performance water reducer, and The above steel slag coarse aggregate is 40% to 44% by weight relative to the total weight of the coarse aggregate, and The water-to-binder ratio is 30.4% and the fine aggregate ratio is 38% to 39.7%, and A concrete composition for a waterway pipe utilizing recycled aggregate, characterized in that the content of the steel slag coarse aggregate, the fine aggregate ratio, and the water-binder ratio are set to be interconnected in order to prevent molding defects or cracks from occurring during demolding despite the weight increase caused by the steel slag coarse aggregate when manufacturing a waterway pipe molded by a precast method.

Description

Concrete Composition for Drainage Pipes Using Recycled Aggregate The present invention relates to a concrete composition for the construction field, and more specifically, to an eco-friendly concrete composition suitable for manufacturing water pipes by utilizing recycled aggregates, specifically recycled coarse aggregate and steel slag coarse aggregate. In particular, it is a technology applied to the manufacture of reinforced concrete water pipes, which are precast concrete products. Recently, efforts to establish resource recycling systems for industrial waste are underway worldwide to improve resource and energy waste and build a circular economy for the preservation of the global environment. Currently, due to a shortage of natural river sand, the use of sea sand at domestic construction sites has increased, leading to environmental destruction. To address this problem, it is believed that steel slag can serve as a substitute for aggregates. The Korean steel industry is a representative industry that consumes large amounts of raw materials and energy. Through a complex series of production processes such as ironmaking, steelmaking, and rolling, it generates a large amount of steel slag as a byproduct along with steel production. As of 2004, the amount of steel slag generated was approximately 14.07 million tons, of which blast furnace slag was about 8 million tons and steelmaking slag was about 6.07 million tons. Figure 1 shows the change in compressive strength according to the replacement rate of steel slag coarse aggregate, and indicates that when replaced by 20% or more, it satisfies 35.0 MPa based on GR F 4035. Figure 2 shows the excellent durability at all replacement rates by comparing the compressive strength around 100 freeze-thaw cycles. Figure 3 shows that the flexural strength improves with increasing replacement rate, achieving a maximum value of 6.3 MPa at 40% replacement. Figure 4 shows the 85-degree 6-hour steam curing temperature profile for the manufacture of precast concrete and the conditions for each stage. Figure 5 shows the results of a comparative analysis of physical properties such as density, fineness modulus, and water absorption rate of steel slag coarse aggregate and recycled coarse aggregate. Figure 6 comprehensively presents the composition of concrete mix ratios based on 1 m³ and the change in the ratio of coarse aggregate according to the replacement rate. Figure 7 shows the changes in workability characteristics of slump, air content, and unit weight as the substitution rate increases, as shown in a dual-axis graph. Figure 8 shows the microstructural differences and performance improvement effects of standard cured and steam-cured concrete through SEM analysis. Figure 9 is a radar chart for six durability indicators, visualizing that optimal overall performance is achieved at 40% substitution. Figure 10 shows the results of an economic and environmental integrated analysis of material cost reduction and carbon dioxide reduction according to the substitution rate. Figure 11 comprehensively presents a detailed analysis of the economic and environmental aspects and quantitative effects of the 40% replacement condition. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In describing the present invention, detailed descriptions of related known technologies are omitted if it is determined that such detailed descriptions may unnecessarily obscure the essence of the present invention. Furthermore, while preferred embodiments of the present invention will be described below, it is understood that the technical concept of the present invention is not limited or restricted thereto and can be modified and implemented in various ways by those skilled in the art. The terms used in this specification have been selected to be as widely used as possible, considering their functions in the present invention; however, these may vary depending on the intent or convention of those skilled in the art, the emergence of new technologies, etc. Additionally, in specific cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, terms used in the present invention should be defined not merely by their names, but based on the meanings they possess and the overall content of the present invention. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Embodiments of the present invention may be represented by functional block configurations and various processing steps. These