The chapter delves into the history and current applications of resin concrete in Japan, highlighting its superior material characteristics such as high strength and durability. It discusses the development of small resin concrete manholes tailored to Japan's unique environmental challenges, including seismic activity and corrosive conditions. The chapter also explores the use of homogenization analysis to optimize resin concrete formulations, demonstrating the potential for efficient material development. Additionally, it touches on environmental adaptability and future prospects, such as the use of biomass resins and recycled aggregates to reduce carbon footprint.
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Abstract
Resin concrete, which has high strength, high early strength development and excellent chemical resistance, has been widely applied for repair and reinforcement of concrete structures, and precast products since the 1950’s. The research and development of resin concrete in Japan have evolved in tandem with various regions and international activities. It is a common and indispensable material for infrastructures in the world at present. On the other hand, there are so many different Acts of God, such as earthquakes, typhoons, and torrential rains, that occur in Japan, and disaster measures are an important issue. In this paper, the current status and practical application of resin concrete mainly applied for sewage products in Japan were investigated and discussed. Based on the regional characteristics of Japan, a resin concrete manhole of high quality to compensate for the defects of cement concrete was developed. Furthermore, the future trends in the research and development of resin concrete including environmental issues such as carbon dioxide emissions reduction, application of recycled materials and bioplastics to replace natural aggregates and petroleum-derived resin for concrete are proposed and discussed. A homogenization analysis method is introduced particularly to bring out the ability of resin concrete as composite materials and to carry out material development efficiently.
1 Introduction
Research and development of resin concrete started in the USSR, USA, West Germany, UK and Japan in the 1950's [1]. In Japan, it was successfully commercialized in1971, and is widely used for precast products such as block manholes and pipes, as well as cast-in-place mortar and concrete. Along with growing use and expanding applications of resin concrete, test methods and quality of resin concrete applied for structural members were established as a Japanese Industrial Standard in 1978 [2‐7]. As a high-strength and lightweight precast concrete, resin concrete is widely used for boxes for protecting valves of water pipes, manholes for sewage facilities, and sewage pipes. Unsaturated polyester resin is mainly used as a binder for resin concrete.
Japan is located in the Circum-Pacific Mobile Belt where seismic and volcanic activities occur constantly. Although the land area of Japan covers only 0.25% of that on the planet, the number of earthquakes and active volcanoes is quite high. Three-fourths of Japan’s land area is mountainous and hilly, and flat land for people to live in is limited. As a result, the population is concentrated on the plains, and there are areas where the roads are too narrow that large vehicles cannot pass. Thus, infrastructures in Japan should have high seismic resistance and corrosion resistance in hot spring areas associated with volcanic activities, and it is necessary to reduce the size of facilities to accommodate narrow land.
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In addition, because of geographical and meteorological conditions, the country is subject to frequent natural disasters such as typhoons, torrential rains and heavy snowfalls, as well as earthquakes and tsunamis. As Japan is an island country surrounded by the sea on all sides, there are concerns about salt damage to coastal structures. The environment surrounding Japan, issues and measures for sewage pipeline facilities as one of the infrastructures are summarized in Table 1.
Table 1.
Environment surrounding Japan, issues and measures for sewage pipeline facilities.
Environment
Influence on sewerage
Measures for pipeline facilities
Many disasters
Earthquake
Destruction of facilities
Higher strength and improved impact resistance
Torrential rains
Flood damage
Efficient pipeline augmentation
Many corrosive environments
Volcanic gas/hot spring area
Early deterioration due to corrosion
Measures against hydrogen sulfide
Salt damage
Measures against salt damage
Topographic features
Narrow road
Work in places where heavy machinery cannot enter
Miniaturization
Little flat area
Corrosion deterioration due to hydrogen sulfide at manhole pump discharge destinations and densely populated areas
Measures against hydrogen sulfide
Aging population/declining working population
Decrease in sewage fee income and workers
Efficient maintenance and long life
Aging facilities
Frequent occurrence of road subsidence accidents
In this paper, the application of resin concrete manholes based on the superior material characteristic and development of the small manhole suited for severe conditions in Japan were investigated. Furthermore, a homogenization analysis method to plan the material optimization of resin concrete was studied and the obtained results were confirmed by the experiments.
2 Development of Small Resin Concrete Manhole
A small resin concrete manhole [8] suited to the Japanese environment was developed as shown in Fig. 1. The development concept of this product is summarized in Table 2. The standard manhole is a combination of cover and body. The inner diameters of the cover and body are 600 mm and 900 mm, respectively. On the other hand, for small manholes, the diameters are both 300 mm. Since people cannot enter inside small manholes, inspection and cleaning inside manholes is done by machines instead of humans. In order to enhance production efficiency and workability, and to reduce material cost and construction cost, small manholes are used in Japan. Reinforced Concrete Small Assembled Manhole and Small Manhole Made of Hard Vinyl Chloride for Sewerage had been established as Japan Sewage Works Association Standard [9, 10]. The standardization played an important role in the popularization of small resin concrete manholes. The developed resin concrete manholes are superior to the former in workability and durability, and to the latter in strength, workability and cost balance, respectively. Furthermore, the inside of the resin concrete manhole was coated by FRP to increase the flexural strength and impact resistance. The improvement in strength made it possible to reduce the thickness and weight of the product. As a result, it is possible to improve the efficiency of transportation and save labor in on-site construction. In addition to the above, the flow function of this resin concrete manhole can be maintained even in the event of a large-scale earthquake such Level 2 earthquake ground motion. The function was confirmed by pull-out/push-in test, bending test and shearing test as shown in Fig. 2. There was no occurrence of lateral slip and cracks in the pull-out/push-in test, bending test and shearing test.
Table 2.
Development concept of a small resin concrete manhole.
Element
Concept
Workability
• Weight reduction by using high-strength esin concrete
• Manpower construction in narrow spaces is possible without using heavy machinery
• Short construction time by assembly
Durability
• Improved lateral flexural strength and impact resistance by combining with FRP
• Applicable to hot spring areas where acid resistance is required and cold areas with severe freezing and thawing
• Flow capacity against level 2 earthquake motion
Cost
• Since heavy machinery is not required, transportation and construction costs are low
• Excellent durability in harsh environments and low life cycle costs
Fig. 1.
Appearance of a small resin concrete manhole.
Fig. 2.
Durability test against level 2 earthquake ground motions.
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2.1 Durability
Resin concrete has almost no water absorption and no penetration of salt, and thus the products have excellent durability such as resistance to freezing and thawing in cold regions and resistance to permeability of salt in coastal areas. Furthermore, it is characterized by excellent corrosion resistance in hot spring areas and places with high hydrogen sulfide gas concentrations.
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Excellent corrosion resistance of resin concrete against chemicals and hydrogen sulfide gas was clarified by the immersion test at the hot spring site and laboratory as described below. Specimens were prepared with FRP attached to the top and bottom of the resin concrete. The sandwiched specimen was thickness 16.5 mm, width 30 mm and length 300 mm and the thickness of resin concrete was 8.0 mm, and that of FRP plates pasted was 3 mm at the top and 5.5 mm at the bottom, respectively. The specimen was immersed in 10% sulfuric acid at 23 ℃ for up to one year. The flexural strength decreased by 10% in the first month, but remained constant thereafter as shown in Fig. 3.
Disk-shaped resin concrete specimens of diameter 50 mm and thickness 10 mm were immersed in an acidic hydrogen sulfide spring of pH 1.8 and 55–70 ℃ for 3 months. Figure 4 shows the appearance of the specimens after 3 months of immersion. The surface was slightly whitened, but there was no change in mass. Cement mortar specimens for comparison became brittle throughout, and its mass was decreased by about 50%. The results of these experiments show that resin concrete can be used under severe corrosive environments such as hot springs and sewage treatment facilities.
Fig. 3.
Changes in flexural strength due to 10% sulfuric acid immersion test.
Fig. 4.
Result of hot spring immersion test (pH 1.8, 55 ~ 70 C).
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2.2 Workability
Reducing the size of manholes provides great benefits. A comparison of construction cost and product weight of portland cement concrete and resin concrete is shown in Fig. 5. Replacing a standard cement concrete manhole at a depth of 2 m with a small resin concrete one, the product weight can be reduced by about 80% and construction cost can be decreased by 30% or more. Due to the miniaturization, construction can be done manually in narrow spaces and construction work is easy even on narrow roads.
Fig. 5.
Comparison of construction cost and product weight of portland cement concrete and resin concrete (2 m deep).
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3 Future Prospects of Resin Concrete
3.1 Environmental Adaptability
A comparison of CO2 emissions related to construction, transportation and manufacture of portland cement concrete and resin concrete manhole is shown in Fig. 6 when the effective inner diameter is fixed [11]. The amount of CO2 emitted per manhole of resin concrete is about 30% less than that of cement concrete. Due to the high performance of resin concrete’s high strength and excellent durability, the weight of products is decreased and CO2 emissions are significantly reduced. Additionally, resin concrete is no elution of harmful substances and environmentally friendly material and then the products can be expected to decrease the amount of materials and long-term service.
Fig. 6.
Comparison of CO2 emissions of reinforce concrete and resin concrete manholes (3 m depth).
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In order to reduce further carbon footprint, three major research and development were tried as follows;
1)
Application of an unsaturated polyester resin from biomass resources. Instead of conventional petroleum-based materials, biomass resin was applied for the resin concrete products.
2)
The recycle of resin concrete products. The recycled aggregates from waste resin concrete products were examined. The material was able to be applied to coarse aggregate by crushing it to a size of about 5 mm, and considering the reduction of flowability and strength, material placement of coarse aggregate was possible up to 10 %. These crushed aggregates can be also used as recycled base course material.
3)
Utilization of blast furnace slag and coal gasification grinded slag. Application of blast furnace slag produced as a by-product in the steel manufacturing process, and coal gasification slag generated at Integrated coal Gasification Combined Cycle abbreviated to IGCC, as recycled aggregate was investigated. Fig. 7 shows the appearance of the recycled aggregates. Since the slag reduced the fluidity at the time of material filling, the particle size was adjusted in advance.
The strengths of the new resin concrete containing biomass resin and recycled aggregate were almost the same as those of conventional ones as shown in Fig. 8. Indeed, the strength of the resin concretes using slag is slightly low, but that can satisfactorily meet the required values. Although it is necessary to investigate CO2 emissions during transportation and procurement costs, it may be used as an alternative material in the future.
Fig. 7.
Appearance of recycled aggregates.
Fig. 8.
Influence of strength on use of biomass resin and recycled aggregate.
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3.2 Application of Homogenization Analysis to Material Development
In the mixture design of resin concrete, according to product requirement, molding conditions and manufacturing method, the material type and mixture proportion are determined. Determining the optimum combination from a myriad of options in a short time leads to efficiency in material development. Recently, homogenization analysis applied in the field of FRP has been investigated [12]. Generally, composite materials are discretized by finite elements, and macroscopic material properties are estimated by homogenization analysis for microscopic models considering periodicity.
Examples of creating 3D micro models for analysis in which coarse aggregate and fine aggregate are filled with a resin paste (filler + resin) are shown in Fig. 9. Young’s modulus and Poisson’s ratio corresponding to aggregate ratios are obtained from homogenization analysis as shown in Fig. 10. These analyzed results suggest the approximate mixture proportion of resin concrete to satisfy the specified physical quantities.
Fig. 9.
Example of 3D micro model used for homogenization analysis.
Fig. 10.
Result of homogenization analysis.
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After test specimens with 55% aggregate content were actually fabricated, strength tests were performed. The test results were compared with the homogenization analysis results. The dumbbell and cylindrical specimens were used for tests. The sizes of test pieces were 25.4-mm diameter with 25.4 mm height at the central parallel part and total 105.4-mm height including the end for tensile strength tests and 75-mm diameter with 150-mm height for compressive tests, respectively. Figure 11 shows the comparison of the results of homogenization analysis and experiment. The strain and strength gradient in the elastic region that are important for product design are in good agreement with the experimental results. Therefore, the apparent physical property values obtained from this analytical method are expected to be used to improve the efficiency of material development.
Fig. 11.
Comparison of results of analysis and experiment.
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4 Conclusions
Development and practical application of resin concrete applied for sewage products in Japan were investigated and discussed. The main conclusions obtained from the results are summarized in the following:
In Japan, resin concrete with unsaturated polyester resin has been developed mainly in the field of civil engineering. The standardization played an important role in the popularization of resin concrete.
Considering severe conditions of sewer infrastructures such as a narrow working environment, long-term resistance to corrosive environment and cost rationalization, small size resin concrete manholes were developed and haves been widely used.
Application of collected used products, plant-derived biomass resin, blast furnace slag and coal gasification slag as recycled aggregate for environmental-friendly resin concrete was tried and proposed.
The homogenization analysis method including 3D micro models is effective in estimating the material properties to permit efficient material formulation design to become possible.
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