DESIGN, CONSTRUCTION AND RECENT APPLICATIONS OF POROUS CONCRETE IN JAPAN M. Tarnai, Kinki University, Japan H. Mizuguchi, The University of Tokushima, Japan S. Hatanaka, Mie University, Japan H. Katahira, Public Works Research Institute, Japan T. Nakazawa, Miyazaki University, Japan K. Yanagibashi, Takenaka Corporation, Japan M. Kunieda*, Gifu University, Japan

28th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 28 - 29 August 2003, Singapore

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28th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 28 - 29 August 2003, Singapore

DESIGN, CONSTRUCTION AND RECENT APPLICATIONS OF POROUS CONCRETE IN JAPAN M. Tarnai, Kinki University, Japan H. Mizuguchi, The University of Tokushima, Japan S. Hatanaka, Mie University, Japan H. Katahira, Public Works Research Institute, Japan T. Nakazawa, Miyazaki University, Japan K. Yanagibashi, Takenaka Corporation, Japan M. Kunieda*, Gifu University, Japan

Abstract Porous concrete (no-fines concrete) had been developed as an environmentally friendly material. In Japan, it has been widely used in various applications. Japan Concrete Institute established "Technical Committee on Establishment of Design and Practical Method of Porous Concrete". The committee summarized the material design concepts, process technology, construction methods of the porous concrete, and investigated applications for reduction of environmental impacts and using bio-adoptability of the porous concrete. Durability and test methods of the porous concrete were also studied. This paper presents some applications of the porous concrete in Japan, and introduces the proposed recommendations for material design and test methods of the porous concrete discussed by the committee. Keywords:

Porous concrete, process technology, construction environmental impact, durability, test methods

methods, bio-adoptability,

Introduction Porous concrete having the continuous voids of about 20% has been defined as one of the environmentally friendly material [1]. There are some studies and reports on basic properties and its applications of the porous concrete [2-6]. As shown in Table 1, Japan Concrete Institute established "Technical Committee on Establishment of Design and Practical Method of Porous Concrete (chairman: Motoharu Tarnai, 2001-2002)". The committee summarized the report including a concept of material 1.

Table 1 Members of the JCI technical committee Chairman: M. Tamai (Kinki Univ.) Co-chairmen: H. Mizuguchi (Univ. of Tokushima), S. Hatanaka (Mie Univ.) Managers: H. Katahira (PWRI), M. Kunieda (Gifu Univ.), T. Nakazawa (Miyazaki Univ.), K. Yanagibashi (Takenaka) Members: K. Asano (Sato Road), Y. Ishikawa (Electric Power Development), Y. Ito (ZEN NAMA), Y. Udagawa (Fujita), M. Kagata (Kajima Road), S. Kajio (Taiheiyo Cement), F. Kaneko (Taisei), H. Suzuki (Toa), H. Tanaka (Shimizu), K. Demura (Nihon Univ.), S. Nagaoka (Sumitomo Osaka Cement), T. Hasegawa (BRI), S. Funahashi (Maeda), T. Horiguchi (Neo Jagras), K. Murata (Ube Mitsubishi Cement), Y. Murata (Cement Assoc.), T. Yamaji (PARI), Y. Yuasa (Mie Pref.) Corresponding members: K Amo (Anan NCT), T. Otani (Oita Univ.), M. Sugiyama (Hokkai-Gakuen Univ.), R. Zhang (Wako Concrete), H. Tokushige (Akita Univ.), H. Murakami (Kumamoto Univ.), A. Zouaghi (Kyowa Concrete), S. Park (Chungnam National Univ.), D. Gemert (Katholieke Univ., Leuven) Secretary: T. Matsuda (Japan Concrete Institute)

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Fig.2

Fig. 1 Placing by backhoes

Placing machine for river revetment

(1) Recommendations for Process Technology and Construction Methods (WG1) (2) Applications for Reducing Environmental Impact (WG2) (3) Applications Using Bio-adoptability (WG3) (4) Durability (WG4) (5) Test Methods (WG5) The committee published the committee report including "recommendations for process technology and construction methods of porous concrete" and "various testing methods of porous concrete". This paper introduces the contents of the report subject to material design, process technology and construction methods of the porous concrete, as Fig. 3 Placing by asphalt finishers for road well as examples of applications for reducing pavement environmental impact and using bio-adoptability of the porous concrete. It also refers to the current status and future subjects of study on the durability of the porous concrete. Finally, the testing methods to evaluate performance of the porous concrete, such as void ratio, water permeability coefficient, modulus of elasticity and so forth are also introduced.

2.

Recommendations for process technology and construction methods(WG1) This working group investigated the component materials and basic properties of fresh and hardened porous concrete. For placing techniques, ordinary construction machines such as backhoe and asphalt finisher were applied, and new type machines were developed, as shown in Figs. 1-3. This working group also proposed "Recommendations for Process Technology and Construction Methods of Porous Concrete (draft)" covering river revetment, road pavement, and precast products, based on the investigations. The contents of the recommendations are summarized in Table 2. 3.

Applications for reducing environmental impact(WG2) This chapter describes the performance of porous concrete including capabilities to permeate, drain, and retain water, purify water, absorb noise, adjust/adsorb moisture, and thermal capabilities, as well as the application of the porous concrete for reducing environmental impact by actively utilizing these capabilities. 3.1 Water-permeating/draining/retaining performance The water-permeating, -draining, and -retaining performances of the porous concrete have been utilized as road pavements, sidewalks, parks, and building exteriors, as well as for plant bedding and permeable rainwater retention facilities, such as permeable trenches, permeable gullies and permeable gutters. Particularly for road pavement, the porous concrete has been used for more than 5,OOO,OOOm 2 of exterior pavement, sidewalks, and exhibition squares since 1985, most of which are of permeable full-depth types. Water-draining composite types have been used for middle and heavy traffic roads.

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Table 2

Summary of Recommendations for Process Technology and Construction Methods of Porous Concrete (draft)

1. Process of making porous concrete 1.1 Materials (1) Cement: Ordinary portland cement, high-early-strength portland cement, blast-furnace slag cement and the like should be used. (2) Water: Water conforming to the same level of requirements for ordinary ready-mixed concrete should be used. (3) Aggregate: Coarse aggregate consisting of a single particle size is preferable to ensure the specified void (e.g., Greening: 13-20 mm, Road pavement: 5-13 mm). No fine aggregate should be used. A small amount of normal sand or fine-grained sand can be used. (It depends on applications.) (4) Chemical admixtures: AE water reducing agent and superplasticizer should be used for the mix proportions with a low water-cement ratio. (5) Admixtures: Admixtures should be used by sufficient information about their effects on the porous concrete. Mix proportions Conditions 1) Void content and void size: Since the void content and void size, which affect the performance of the porous concrete, are important, the aggregate size and other conditions should be selected appropriately. 2) Specified Design strength: Since the strength of the porous concrete is closely related to the void content, the specified design strength should be adequately established according to the use. 3) Strength for Mix Proportioning: The Strength for mix proportioning should be established by adding a margin for the variations of quality to the specified design strength. 4) Durability: The porous concrete should be designed with a low water-cement ratio to compensate for the slightly lower durability compared with ordinary concrete. 5) Consistency: Consistency should be established in consideration of the use and construction conditions. (2) Procedure of proportioning calculation The following procedure should be regarded as a standard: 1) select the coarse aggregate content in consideration of the use, 2) establish a mortar content suitable for the void content, 3) determine the fine aggregate content, 4) determine the unit water content and cement content, and 5) determine the admixture dosage.

1.2

(~)

1.3 Mixing (1) Storage of materials: The materials should be stored so that the stability of surface moisture content of aggregate is maintained, because the porous concrete has low water content and high aggregate content. (2) Batching of materials: The batch size may be limited by the dispenser capacity or mixer load capacity. (3) Mixing: A mixer with a high mixing efficiency should be used. The mixing sequence should be checked beforehand. (4) Transportation: The porous concrete should be transported by dump trucks or agitating trucks. 2. Placing in situ 2.1 River revetment (1) Conveyance within site: Backhoes, cranes, belt conveyers, and manpower should be used. (2) Placement and compaction: There has been field experience in the use of backhoes and vibration compactors. Care should be exercised to protect the porous concrete from drying during placing. (3) Curing: Sufficient moist curing should be carried out. 2.2 Road pavement (1) Conveyance within site, placement and compaction: Asphalt finishers should primarily be used. Vibration rollers and rubber tire rollers should be used for roller compaction as required. For a small area, vibration compactors, rammers, etc. should be used. Work should be carried out quickly while exercising care for protecting the porous concrete from drying. (2) Curing: Sufficient moist curing should be carried out. 3. Precast products (1) Molding: The procedure up to mixing should be carried out in accordance with 1.1 to 1.3. The porous concrete should be consolidated with adequate setting of the vibration time to prevent mortar segregation. Care should be exercised for surface finishing, as troweling is difficult. (2) Curing: Sufficient curing should be carried out. In the case of steam curing, care should be exercised to avoid abrupt temperature changes. (3) Form stripping, transportation and construction on site: Care should be exercised to prevent corner defects.

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Fig.4

Water purifying blocks(example 1)

Fig.5 Water purifying blocks(example 2)

Fig.6

Noise barrier in railway

Fig. 7

Noise barrier in expressway

For tollgates on heavy traffic expressways, the porous concrete having high rutting resistance, abrasion resistance and oil resistance as well as drainage function is bonded and unified with continuous reinforced concrete slabs into composite pavement to withstand the repeated stopping and starting motions of cars. For the purpose of tentative ponding of rainwater and recharging into the ground, the porous concrete is used for permeable trenches, gullies, and side gutters. 3.2 Water purifying performance Pollution of urban rivers, lakes, and wetlands and enclosed coastal waters near large cities has been serious in recent years due to runoffs containing wastewater from homes and plants, posing problems of environmental disruption. Water purification by the porous concrete is a sort of inter-gravel contact oxidation, in which the biota formed on the internal surfaces of continuous voids provide an additional bio-purification function. It is therefore anticipated that the porous concrete applied to revetment and coastal areas would contribute to water purification by the biota consisting of various organisms including microbes. As shown in Figs. 4 and 5, examples of the application of the porous concrete to this field include waterway purification using the porous concrete blocks with embedded aerators, which are expected to adsorb nitrogen and phosphorus as well. Other examples include facilities for biopurification by inter-gravel contact oxidation and those constructed as biotopes with a function of water purification where a wide variety of living organisms gather. 3.3 Noise-absorbing performance Porous materials can be used as noise-absorbing products. Active attempts have been made in recent years to develop precast concrete acoustic panels using the porous concrete, to impart not only a noise-insulating effect but also noise-absorbing one to concrete products. Practical application of the porous concrete to noise barriers, the backside of elevated roads and inside walls of tunnels is under way, as shown in Figs. 6 and 7. 3.4 Thermal performance Thermal performance of the porous concrete refers to its performance to mitigate or improve the environment in terms of thermal conditions. Investigation into thermal performance of the porous concrete has just commenced. Field experience is still limited, with a small number of examples

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Fig.8

Fig. 9

Revetment by porous concrete blocks

Plant growing on porous concrete

Soli on surface Porous concrete(300mm)

Water retention material, fertilizer in voids

Fig.10 Greening of slope

Fig. 11

Image for revetment by porous concrete

including road pavements and rooftop gardens. 3.5 Moisture-conditioning/adsorbing performance The moisture-conditioning performance of the porous concrete is said to depend on the mOisture-absorbing properties of aggregate, void content, the conditions of internal void surfaces, and the properties of the binder. Excellent moisture-conditioning performance can therefore be achieved for buildings requiring such properties by properly selecting the aggregate, binder and mixture proportions to be used. Due to its large surface area, the porous concrete can be made to possess a gas-adsorbing performance by selecting materials to adsorb SOx and NOx for the aggregate and binder (e.g., zeolite), with which hazardous gases in the atmosphere can be adsorbed and made harmless. Also, hazardous gases can be fixed and made innocuous further by applying a photocatlyst, such as titanium oxide, to the porous concrete surfaces. 4

Applications using bio-adoptability(WG3} This chapter describes the applications of porous concrete in biohabitats focusing on its friendliness to plants, insects and other animals, as well as to marine organisms and microbes. 4.1 Plant-growing performance Examples of applications of the porous concrete in this field are shown in Figs. 8-11. When growing plants on the porous concrete, it is necessary to provide space for growing roots, ensure effective water retention, reduce the amount of alkali leaching and retain fertilizer components. Regarding space for roots, the recommended continuous void contents are as follows: not less than 25% for immediate plant growth, not less than 21 % for later growth and not less than 18% for viable growth. Applicable aggregate sizes, which determine the void size, are crushed stone in the range of 5-13mm, 13-20mm, 20-30mm, 5-20mm, 15-20mm and 15-25mm. For ensuring an effective amount of water retention, it is desirable to fill a water-retaining material in the voids to compensate for the low effective amount of water retention of the porous concrete or to cover the top surfaces with soil.

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Fig. 12

Porous concrete as habitat

Fig. 13 Seaweed on porous concrete

Fig. 14 Seaweed on porous concrete blocks

Fig. 15

Precast porous concrete blocks

The amount of alkali leaching shortly after placing of the porous concrete can adversely affect the plant growth. For this reason, in such a case as sodding a lawn on the porous concrete shortly after in-situ placing, it is necessary to reduce the amount of alkali content by the following methods: use combined cement, such as blast-furnace slag cement and fly ash cement, in which alkalis can be consumed by their latent hydrating properties or pozzolanic reactivity; use ordinary portland cement and provide a certain acclimatizing period; use normal portland cement and steam-cure; or carry out neutralization treatment after hardening of the porous concrete. Since the porous concrete scarcely contains nutrients necessary for plants, such as phosphorus and potassium, solid or liquid fertilizers should be supplied to the bedding. 4.2 Insect/animal accommodating performance Voids in the porous concrete may serve as habitats for larvae of waterside land insects, water bugs and benthic organisms in plain water, as shown in Fig. 12. In order to achieve vegetation on river revetments made of the porous concrete, the void content should be not less than 18%, and the void diameter should be 1-2mm (crushed stone NO.6: 5-13mm) or 3-4mm (crushed stone NO.5: 13-20mm). Organisms of a size that fit such voids can inhabit the spaces. The void diameter is a critical factor. Larvae of mole crickets (approximately 1cm long and 3mm thick) were reportedly found to grow in the porous concrete revetment with a void content of 22% and void diameter of 3-4mm (crushed stone No. 5: 13-20mm). 4.3 Marine organisms The high coarseness of the porous concrete makes it easy for seaweed and shellfish to cling to its surfaces, as shown in Figs. 13-15. Though no particular recommendations are available for the void content and its size for these surface inhabitants, it is generally considered adequate to select a void content of not less than 18% using crushed stone No. 6(5-13mm}, preferably No. 5(13-20mm} or greater, for the aggregate. 4.4 Microbes In enclosed waters such as gulfs, lakes and wetlands, water quality deterioration by algal blooms of phytoplanktons, such as "red tide", has been posing a serious problem in recent years. This

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phenomenon is primarily attributed to increases in the levels of biological nutrients entering such waters. The porous concrete made using crushed stone provides a range of surface coarseness depending on the aggregate diameter. When such surfaces are kept in contact with turbid water, not only aerobic but also anaerobic bacteria are reported to inhabit in the biofilms on the external surfaces of the porous concrete. It follows that microscopic anaerobic conditions can exist in such biofilms adhering to the minute irregularities of the surfaces. It is therefore desirable to select aggregate for the porous concrete to provide a habitat for both aerobic and anaerobic bacteria by making the surface and internal environments more anaerobic, in order to accelerate the denitrifying effect. 5

DurabiJity(WG4) In light of increasing field experience with porous concrete, the following sections summarize deterioration of the porous concrete due to cyclic wetting and drying, hydrate washout, and repeated freezing and thawing. Round-robin tests were conducted by the committee in regard to cyclic wetting and drying, as well as washout tests [8,9]. 5.1 Effects of plain water and seawater Assuming the case where the porous concrete is used as a base for water purification or seaweed field formation, tests were conducted in which the porous concrete was immersed in a flow of tap water or artificial seawater. These tests revealed that the losses in the relative dynamic modulus were marginal, that the mass of concrete decreased in fresh water but increased in artificial seawater, and that the Ca(OHh concentration decreased by leaching. When the porous concrete was immersed in natural seawater, the compressive strength increased by around 20% at early ages and decreased from the peak by 10 to 15% at 182 days. It was also found that the addition of silica fume reduced the strength losses and that the strength increased as the aggregate diameter decreased. This is presumably because seaweed and biofilms of microbes in natural seawater adhere to the internal and external surfaces of the porous concrete, tending to inhibit strength losses. Test data on a longer term basis are essential for elucidating deterioration of the porous concrete by fresh and seawater. Future investigation is anticipated. 5.2 Cyclic wetting and drying Under alternating dry and wet conditions due to rainwater and moisture, paste or mortar undergoes expansion and contraction, which produces differences between the coefficients of drying shrinkage and thermal expansion of the matrix and the aggregate, causing concern about microscopic cracking. Various test methods have conventionally been attempted to measure the resistance to this action, but the results are known to widely vary depending on the test method. It is generally reported that the use of fine aggregate and the use of small-diameter coarse aggregate improve the resistance to cyclic wetting and drying, that not only void content but also void size strongly affects the resistance, and that inclusion of short fibers may improve the resistance. 5.3 Freezing and thawing Being a structure having continuous voids, the porous concrete readily allows permeation of water including rainwater, resulting in freezing and thawing action internally and externally. This causes concern that the porous concrete might be more vulnerable to deterioration than normal concrete. Possible effects on this kind of deterioration include thermal conductivity, latent heat of concrete during freezing and thawing of water in concrete, and thermal properties of concrete. A deterioration mechanism resulting from the difference between the coefficients of linear expansions of ice and paste is assumed for this phenomenon. Though a number of test methods and parameters have been proposed for evaluating the resistance to freezing and thawing, the results widely vary depending on the test method. It is therefore important to select a test method suitable for the speCific use. In general, smaller diameters of coarse aggregate tend to lead to lower resistance to freezing and thawing. Methods of improving resistance to freezing and thawing of the porous concrete include the use of air-entraining admixture, densification of microstructures by the addition of silica fume and other additions, improvement of bond at aggregate-paste interfaces, and improvement of ductility by the addition of fibers. 5.4 Carbonation Major causes of carbonation of the porous concrete include CO 2 permeation and reductions in the pH value due to leaching out calcium from concrete surfaces. Since the porous concrete has mostly been used for unreinforced concrete having no steel reinforcement such as steel bars, few examples of study or deterioration are currently available regarding carbonation. 5.5 Abrasion As the thin binder layer covering coarse aggregate is directly subjected to physical actions, significant abrasion is of concern. Abrasion by tires and tire chains of vehicles is expected for road pavement, whereas abrasion by water flow including gravel and sand is expected for revetments. The

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abrasion loss of the porous concrete by erosion is lower than that of normal concrete, and the greater the coarse aggregate, the lower the abrasion loss. When comparing the porous concretes made using the same coarse aggregate, the higher the compressive strength gives the higher abrasion resistance. In regard to the resistance to aggregate loss (by the Cantabro method, mass loss ratio), the losses increase as the void content increases, and decreases as the maximum aggregate size decreases. 5.6 Repeated loading (fatigue) There are some reports focusing on the resistance of the porous concrete to repeated loading in road pavement. Whereas test results of the compressive fatigue properties of the porous concrete scatter more widely than normal concrete, underwater resistance to fatigue of the porous concrete is known to be higher than that of normal concrete in the range of low upper limit stresses. Though the flexural fatigue properties of the porous concrete is lower in water than in air, it is pointed out that its fatigue life is comparable to that of normal concrete. 5.7 Effects of plants Possible effects of plants on the porous concrete include failure due to the growth pressure of roots and erosion by organic acids secreted from roots, but no such failure or erosion has so far been reported. The absence of defect incidents due to root growth is presumably attributed to the fact that there have been only a limited number of examples of planting arbors on the porous concrete, with the age being 5 years at the longest, and that the compressive strength of the porous concrete is significantly higher than soil hardness, while its tensile strength exceeds the pressure of growing roots. The absence of defects due to organic acids secreted from tree roots is considered to be due to the fact that organic acids are mostly weak acid with weak erosive action on concrete compared with inorganic acids and that the chemical resistance of the porous concrete is high owing to the low water-cement ratio between 20 and 30%. 5.8 Alkali-aggregate reaction No reports have been available on defects induced by alkali-aggregate-reaction or investigation into the reaction in regard to the porous concrete. In light of the mechanism of concrete expansion due to alkali-aggregate reaction, it is considered probable that the expansion resulting from alkali-aggregate reaction in the porous concrete is absorbed by air voids, which account for more than 10% of the concrete volume, ending up with no expansive pressure or damage. On the other hand, it is also possible that cracking or bond failure can occur in the microscopic range, i.e., at the boundaries between coarse aggregate and paste or mortar, leading to damage including strength losses. This is another subject for the future.

6

Test methods(WGS} Physical test methods for evaluation of basic properties of porous concrete were proposed by JCI Technical Committee on Eco-concrete (Chairman: Motoharu Tamai, 1994-1995) and have been used in various situations. However, practical operation by these methods has revealed some pOints requiring improvement. Improvements to these methods and new test methods in demand are proposed in the following sections as "Test method for void ratio offresh porous concrete (draft)," "Test method for static modulus of elasticity of porous concrete (draft)," and "Test method for resistance of porous concrete to cyclic wetting and drying (draft)." 6.1 Method of making porous concrete specimens (draft) (1) Specimen size It has been pOinted out in recent years that air voids near the molded surfaces strongly affect the test results. Such effects of voids on various test results should therefore be minimized. For cylindrical specimens, a diameter of 15cm or 12.5cm is required as a rule in this method when the maximum aggregate size is 40mm or less. The 10-cm diameter specimens can be used with respect to maximum aggregate sizes is given in Table 3. Though 10-cm diameter specimens are easy to handle, uncertainties remain in their applicability to coarse aggregate with a maximum diameter between 15 and 25mm, requiring care during testing.

Table 3

Applicability of 10-cm diameter specimens with respect to maximum aggregate size

Maximum aggregate size 25mm :s; G max 15mm :s; G max < 25mm Gmax:S;

15mm

10 x 20cm (diameter x heiQht) Inadequate because of strong effect of voids near molded surfaces Applicable (provided the effect of voids near molded surfaces is cleared beforehand) Applicable

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(2) Method of making specimens Placing the porous concrete in molds in Demold specimens (drill cores) layers while consolidating each layer to a smooth surface can cause excessively porous portions similarly to those near Measure the volume of specimens, VI molded surfaces. This can cause strength losses and excessive void, adversely Saturate specimens in water for 24 h affecting the test results. 6.2 Test method for void ratio of Measure the mass in water, WI porous concrete (draft) (1) Definitions "Continuous void ratio" is defined as the "percentage of the volume of continuous voids to the total volume of the specimen". Measure the mass in water, W3 "Continuous voids" are defined as voids that are continuous to the external surfaces and Calculate the total void ratio, At. and continuous void can be easily saturated with water and ratio, Ac, by the foll9win9 equations: drained. "Total void ratio" is defined as the Total void ratio: percentage of the total volume of voids to the total volume of the specimen. The total A {%)= 1- (W2 - WI )/ Pw x 100 t volume of voids is calculated as the sum of VI continuous voids and closed voids. Closed Continuous void ratio: voids are discontinuous with the external space. It takes a certain amount of time to Ac{%) = At - (WI -~3)/ Pw x100 saturate with water or drain closed voids. It I should be noted that the total void ratio is defined as the void ratio calculated by using Fig. 16 Flow of test method for void ratio the mass of a specimen in the air after draining it and leaving it to stand for 24 hours. (2) Methods of measuring mass in the air and determining void ratio Figure 16 shows the flow of calculating the total void ratio and continuous void ratio. The flow for prismatic specimens is also proposed. Further data accumulation is necessary for discussion of the interchangeability between them. 6.3 Test method for permeability of porous concrete (draft) Conventional permeability test methods covered only cylindrical specimens. In the proposed test method, a method for prismatic specimens is also available in addition to the method for cylindrical specimens. 6.4 Test method for void ratio of fresh porous concrete (draft) This test method was established referring to PWRI report "Manual for rapid judgment of the properties of fresh porous concrete [10)" to judge the void properties of the freshly mixed porous concrete. Basically, water is poured from the top surface of the porous concrete filled in a container by the specified method, and the percentage determined by dividing the amount of poured water by the volume of the container is defined as continuous void ratio. The air content of the porous concrete after pouring water is then measured in accordance with Japanese Industrial Standard (JIS) A 1128, and the sum of the determined air content and the above-mentioned continuous void ratio is defined as the total void ratio. It should be noted that this is a simple method of roughly measuring the void ratio of the fresh porous concrete. For the void ratio to be used for proportioning of the porous concrete, the value determined from hardened specimens should be adopted. Table 4 Test conditions for cyclic wetting and drying Specimen size Wet condition Dry condition Cycle

Test end

100x1 00x400mm In water(20°C) In oven(40°C) 3 days in dry condition -- 1 day in wet condition --2 days in dry condition -- 1 day in wet condition (This means 2 cycles) Total 30 cycle

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6.5 Test method for static modulus of elasticity of porous concrete (draft) This method basically follows JIS A 1149, the test method for static modulus of elasticity of concrete. In the calculated stress-strain curve of the porous concrete, since the strain at the peak stress is lower than that of normal concrete, the porous concrete exhibits linear elastic behavior up to a point approximately f/3 of the peak stress. Accordingly, in this test method as well, the static modulus is determined as the secant modulus given as the slope of the line segment connecting the stress corresponding to 1/3 of the peak load and the stress at a longitudinal strain of the specimen of 50 x 10-6 in the stress-strain curve of the specimen. 6.6 Test method for resistance of porous concrete to cyclic wetting and drying (draft) This is a method of evaluating the deterioration of the porous concrete specimens exposed to alternating wetting and drying environments in terms of relative dynamic modulus and mass reductions. The test conditions include the specimen size, temperature and duration of wet and dry conditions, and the rate of shifting to the other condition. In this test method, conditions shown in Table 4 have been selected in consideration of actual conditions and the results of the round-robin tests. (i.e. wetting at 20°C in water and drying at 40°C in an oven) . As for the total number of wetting and drying cycles to be applied, which may depend on the properties of the porous concrete, the value of 30 was selected for the present stage. Further data accumulation is necessary to find as to what degree of deterioration under normal exposure conditions is represented by the deterioration after 30 cycles in the test conditions. 7

Summary This paper introduced the recommendations for process technology and construction methods of porous concrete, and various test methods. And also, applications of porous concrete for reducing environmental impact and using bio-adoptability were reported while summarizing the current status and future subjects on the durability of porous concrete. The authors wish that the recommendations and test methods help to increase the number of application using the porous concrete, such as road pavement and river revetment and others. References: [1]Japan Concrete Institute: Technical Committee Report on Eco-concrete, 1995 (in Japanese) [2]M. Tarnai and T. Matsukawa: Properties and Application of Environmentally Friendly Porous Concrete, ACI SP179, pp.123-140, 1998 [3]K. Yanagibashi and T. Yonezawa: Properties and Performance of Greening Concrete, ACI SP179, pp.141-158,1998 [4]H. Fujiwara, R. Tomita, T. Okamoto, A. Dozono, A. Obatake: Properties of High-Strength Porous Concrete, ACI SP179, pp. 173-187, 1998 [5]A. Beeldens, D. Van Gernert, C. Caestecker, M. Van Messem and E. De Winne: Influence of Polymer Modification on Durability of Porous Concrete, ACI SP192-47, 2000 [6]N. Ghafoori and S. Dutta: Building and Nonpavement Applications of No-Fines Concrete, Journal of Materials in Civil Engineering, VoL7, No.4, pp.286-289, 1995 [7]Japan Concrete Institute: Technical Committee Report on Establishment of Design and Practical Method of Porous Concrete, 2003 (in Japanese) [8]S. Kajio, H. Mizuguchi and H. Katahira: Study on Dry-wet Cyclic Resistance of Porous Concrete, Proc. of JCI Symposium on Design, Construction and Recent Applications of Porous Concrete, pp.139-142, 2003 (in Japanese) [9]Japan Concrete Institute: Round Robin Tests on Wash-out, Technical Committee Report on Establishment of Design and Practical Method of Porous Concrete, pp.203-207, 2003 (in Japanese) [10]H. Kawano and H. Katahira: Manual for Rapid Judgment of the Properties of Fresh Porous Concrete, PWRI Report No. 3765, 2000 (in Japanese)

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