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Case Studies in Construction Materi
Case Studies in Construction Materials 1 (2014) 1–9
Contents lists available at ScienceDirect
Case Studies in Construction Materials
jour nal h omep age: www.elsevie r .com/locat e/cscm
Short Communication
Monitoring in situ performance of pervious concrete in British
Columbia—A pilot study§
Rishi Gupta *
Civil & Environmental Engineering Program, Department of Mechanical Engineering, University of Victoria, Canada
A R T I C L E I N F O
Article history:
Received 25 September 2013
Accepted 3 October 2013
Keywords:
Pervious concrete system No-fines concrete Raveling
Stormwater management
Sustainability
Asphalt replacement
A B S T R A C T
Modern day infrastructure calls for use of impervious surfaces and curb and gutter systems on pavements to rapidly collect and transport rain runoff. Due to this stormwater reaches the receiving water bodies rapidly, in greater volume and carries more pollutants than natural conditions. Porous pavement on parking lots, sidewalks, and driveways provides a solution to this problem. One such material that can be used to produce porous surfaces is pervious concrete. Even though no-fines concrete mix has been used for many years, there are still many outstanding issues related to its structural performance and issues with reduced percolation capacity over time especially when exposed to real conditions. This paper presents a case study describing a project in British Columbia, Canada where
1000 ft2 of asphalt was replaced with a pervious concrete system. The details of the unique
construction technique including details of the material used are described in this paper. On-going tests to monitor the performance of this test slab are also described.
2013 The Author. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Stormwater management has become a concern for cities and municipalities due to increased urbanization of residential and commercial neighborhoods. In a built environment with significant amount of impervious surfaces and integration of curb and gutter systems in our pavements, stormwater reaches the receiving water bodies much faster, in greater volume and carries more pollutants. Cities and municipalities along with engineers, researchers and developers are exploring different ways to reduce the impervious surfaces and to deal with stormwater management in a sustainable and environment friendly manner. Porous pavement is found to be an effective measure to mitigate the impact of urbanization on the environment. Without occupying any additional space, porous pavement on parking lots, sidewalks, and driveways provides multiple benefits, i.e. promotes infiltration, reduces peak flows and runoff volume, improves water quality, and reduces thermal pollution, thus helping to maintain our delicate ecological balance and the environment we live in. Using materials that allow water to permeate into the ground helps contribute to the ground water table. One such material that can be used to construct porous pavements and porous urban surfaces is ‘‘pervious concrete.’’ This type of concrete has high permeability and allows rain water to permeate.
According to Sustainable Concrete Canada (2012), the pervious concrete system can have the following impact on the environment: eliminating time consuming and costly storm water detention facilities and underground piping systems, allowing water, air and nutrients to tree roots promoting healthy tree growth without damaging your pavement surface, increasing the quantity of water which can be retained on your site and infiltrate into aquifers thus promoting healthy water
§ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
* Tel.: +1 250 721 7033.
E-mail address: guptar@uvic.ca
2214-5095/$ – see front matter 2013 The Author. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cscm.2013.10.001
levels which sustain our streams and drinking water, eliminating the expense of curbs and gutters, reclaiming valuable property otherwise consumed by stormwater tanks and ponds, preventing harmful hydrocarbons, and other pollutants from reaching our waterways which commonly occur with conventional storm water systems. Pervious concrete is being used for many applications including use as a paving material for parking lots, lightweight structural walls, tennis courts, and greenhouse floors (ACI Committee 522, 2006). Pervious concrete is also known as ‘‘no-fines’’ concrete. Pervious concrete reduces storm water pollution at the source, control storm water runoff, and eliminate or reduce the size of storm sewers (Schokker, 2010). However, there are many issues related to pervious concrete that still need to be further investigated to improve its life and performance during service. Some of the current issues for pervious concrete are as follows.
1.1. Clogging
When small material such as dirt and fine sand are carried by storm water through the pores of pervious concrete, the debris can eventually reduce the effectiveness of the drainage and permeability of the concrete. Such clogging could then lead to flooding and the concrete being susceptible to extensive freeze–thaw cycles (Deo et al., 2010). One issue associated with this is the requirement to maintain the slabs by frequent power washing to unclog the pores.
1.2. Abrasion resistance
As the bonding in pervious concrete is aggregate-to-aggregate rather than the aggregate embedded in a cementitious paste like in regular concrete, pervious concrete has poorer mechanical properties. Pervious concrete is susceptible to abrasion failure caused by the surface course being worn off or crushed under traffic loads (Wu et al., 2011). This phenomenon is sometimes referred to as ‘‘raveling.’’
1.3. Freeze and thaw
When pervious concrete is exposed to cold climates, there is a possibility the concrete would undergo extensive freeze– thaw cycles if the placement was fully saturated. This leads to pressure on the thin cement paste surrounding the aggregates and a loss of durability of the concrete (Kevern et al., 2010).
To study these issues, a project was recently initiated by the author at British Columbia Institute of Technology (BCIT) in Canada. This project involved replacing a section of the asphalt paved surface in a parking lot with pervious concrete. The aim of this project is to determine the feasibility of using pervious concrete on a larger scale, especially as an alternative to using asphalt for paving. The pilot slab is being exposed to real environmental conditions and traffic. The observations and test results from this study will help address above-mentioned issues and determine the feasibility of using larger placements in the future especially when using in regions that are prone to freeze–thaw cycles. In this paper, the procedure used to construct this non-traditional system of pervious concrete as a pavement is discussed and the on-going tests to monitor the performance of the pavements are described. Some of the initial test results are also presented.
2. Construction details
The site is located at the northern area of Parking Lot F at the Burnaby campus of BCIT, Canada (Fig. 1a). The placement size is 24 ft 40 ft, and covers three parking stalls (794, 795, and 796) and the roadway adjacent to it. The site location was specifically chosen to study the effect of standing traffic, moving traffic, and turning vehicles.
The construction of the concrete slab was completed in three major stages: excavation and asphalt removal, subbase fill, and the concrete placement and curing. The details of each are described below.
2.1. Excavation
The existing asphalt was saw cut to form straight edges and 12 in. deep excavation was done. The soil below the asphalt pavement consisted of sandy soil for the top 6 in., and sandy clay in the lower 6 in. Sets of perforated pipes were placed below lanes 795 and 796 located at west end of the test slab (Fig. 1b). One set was placed at the bottom of the clear crush and one at the bottom of the 6 in. thick pervious concrete slab (Photos 1 and 2). Separate pipes were used at each level under lot 795 and
796 to study the reduction in percolation capacity (if any) by not maintaining (power washing) one section of the pavement. In this study, lot 795 will be maintained and lot 796 will be left unmaintained. A small portion of the ditch north of the placement (outside the test slab) was also excavated to accommodate a water collection system for testing purposes (Photo
3). The perforated pipes were 3 in. in diameter, 7 ft in length, and made from PVC.
2.2. Subbase fill
Once the excavation was complete, 6 in. of fractured clear crush with a maximum aggregate size of 3/ 4 in. was deposited above the subgrade. The fill was then compacted using a vibratory roller and measured to gain a uniform depth of 6 in.
Fig. 1. (a) Site location at BCIT’s Burnaby campus (inset – zoomed in view of the test slab). (b) Dimensions of the test slab.
Photo 1. Perforated pipes above the subgrade.
Photo 2. Perforated pipes on top of crush connecting to ABS pipes.
throughout the placement. Photo 4 shows the clear crush being compacted by the vibratory compactor. The background of Photo 4 also shows the simultaneous excavation of soil and the transportation of clear crush from a nearby deposited pile. The clear crush is necessary for pervious concrete as it acts as a storage medium and a filtration system for water passing through the pervious concrete. The crush also acts as a subbase for receiving th
Contents lists available at ScienceDirect
Case Studies in Construction Materials
jour nal h omep age: www.elsevie r .com/locat e/cscm
Short Communication
Monitoring in situ performance of pervious concrete in British
Columbia—A pilot study§
Rishi Gupta *
Civil & Environmental Engineering Program, Department of Mechanical Engineering, University of Victoria, Canada
A R T I C L E I N F O
Article history:
Received 25 September 2013
Accepted 3 October 2013
Keywords:
Pervious concrete system No-fines concrete Raveling
Stormwater management
Sustainability
Asphalt replacement
A B S T R A C T
Modern day infrastructure calls for use of impervious surfaces and curb and gutter systems on pavements to rapidly collect and transport rain runoff. Due to this stormwater reaches the receiving water bodies rapidly, in greater volume and carries more pollutants than natural conditions. Porous pavement on parking lots, sidewalks, and driveways provides a solution to this problem. One such material that can be used to produce porous surfaces is pervious concrete. Even though no-fines concrete mix has been used for many years, there are still many outstanding issues related to its structural performance and issues with reduced percolation capacity over time especially when exposed to real conditions. This paper presents a case study describing a project in British Columbia, Canada where
1000 ft2 of asphalt was replaced with a pervious concrete system. The details of the unique
construction technique including details of the material used are described in this paper. On-going tests to monitor the performance of this test slab are also described.
2013 The Author. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Stormwater management has become a concern for cities and municipalities due to increased urbanization of residential and commercial neighborhoods. In a built environment with significant amount of impervious surfaces and integration of curb and gutter systems in our pavements, stormwater reaches the receiving water bodies much faster, in greater volume and carries more pollutants. Cities and municipalities along with engineers, researchers and developers are exploring different ways to reduce the impervious surfaces and to deal with stormwater management in a sustainable and environment friendly manner. Porous pavement is found to be an effective measure to mitigate the impact of urbanization on the environment. Without occupying any additional space, porous pavement on parking lots, sidewalks, and driveways provides multiple benefits, i.e. promotes infiltration, reduces peak flows and runoff volume, improves water quality, and reduces thermal pollution, thus helping to maintain our delicate ecological balance and the environment we live in. Using materials that allow water to permeate into the ground helps contribute to the ground water table. One such material that can be used to construct porous pavements and porous urban surfaces is ‘‘pervious concrete.’’ This type of concrete has high permeability and allows rain water to permeate.
According to Sustainable Concrete Canada (2012), the pervious concrete system can have the following impact on the environment: eliminating time consuming and costly storm water detention facilities and underground piping systems, allowing water, air and nutrients to tree roots promoting healthy tree growth without damaging your pavement surface, increasing the quantity of water which can be retained on your site and infiltrate into aquifers thus promoting healthy water
§ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
* Tel.: +1 250 721 7033.
E-mail address: guptar@uvic.ca
2214-5095/$ – see front matter 2013 The Author. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cscm.2013.10.001
levels which sustain our streams and drinking water, eliminating the expense of curbs and gutters, reclaiming valuable property otherwise consumed by stormwater tanks and ponds, preventing harmful hydrocarbons, and other pollutants from reaching our waterways which commonly occur with conventional storm water systems. Pervious concrete is being used for many applications including use as a paving material for parking lots, lightweight structural walls, tennis courts, and greenhouse floors (ACI Committee 522, 2006). Pervious concrete is also known as ‘‘no-fines’’ concrete. Pervious concrete reduces storm water pollution at the source, control storm water runoff, and eliminate or reduce the size of storm sewers (Schokker, 2010). However, there are many issues related to pervious concrete that still need to be further investigated to improve its life and performance during service. Some of the current issues for pervious concrete are as follows.
1.1. Clogging
When small material such as dirt and fine sand are carried by storm water through the pores of pervious concrete, the debris can eventually reduce the effectiveness of the drainage and permeability of the concrete. Such clogging could then lead to flooding and the concrete being susceptible to extensive freeze–thaw cycles (Deo et al., 2010). One issue associated with this is the requirement to maintain the slabs by frequent power washing to unclog the pores.
1.2. Abrasion resistance
As the bonding in pervious concrete is aggregate-to-aggregate rather than the aggregate embedded in a cementitious paste like in regular concrete, pervious concrete has poorer mechanical properties. Pervious concrete is susceptible to abrasion failure caused by the surface course being worn off or crushed under traffic loads (Wu et al., 2011). This phenomenon is sometimes referred to as ‘‘raveling.’’
1.3. Freeze and thaw
When pervious concrete is exposed to cold climates, there is a possibility the concrete would undergo extensive freeze– thaw cycles if the placement was fully saturated. This leads to pressure on the thin cement paste surrounding the aggregates and a loss of durability of the concrete (Kevern et al., 2010).
To study these issues, a project was recently initiated by the author at British Columbia Institute of Technology (BCIT) in Canada. This project involved replacing a section of the asphalt paved surface in a parking lot with pervious concrete. The aim of this project is to determine the feasibility of using pervious concrete on a larger scale, especially as an alternative to using asphalt for paving. The pilot slab is being exposed to real environmental conditions and traffic. The observations and test results from this study will help address above-mentioned issues and determine the feasibility of using larger placements in the future especially when using in regions that are prone to freeze–thaw cycles. In this paper, the procedure used to construct this non-traditional system of pervious concrete as a pavement is discussed and the on-going tests to monitor the performance of the pavements are described. Some of the initial test results are also presented.
2. Construction details
The site is located at the northern area of Parking Lot F at the Burnaby campus of BCIT, Canada (Fig. 1a). The placement size is 24 ft 40 ft, and covers three parking stalls (794, 795, and 796) and the roadway adjacent to it. The site location was specifically chosen to study the effect of standing traffic, moving traffic, and turning vehicles.
The construction of the concrete slab was completed in three major stages: excavation and asphalt removal, subbase fill, and the concrete placement and curing. The details of each are described below.
2.1. Excavation
The existing asphalt was saw cut to form straight edges and 12 in. deep excavation was done. The soil below the asphalt pavement consisted of sandy soil for the top 6 in., and sandy clay in the lower 6 in. Sets of perforated pipes were placed below lanes 795 and 796 located at west end of the test slab (Fig. 1b). One set was placed at the bottom of the clear crush and one at the bottom of the 6 in. thick pervious concrete slab (Photos 1 and 2). Separate pipes were used at each level under lot 795 and
796 to study the reduction in percolation capacity (if any) by not maintaining (power washing) one section of the pavement. In this study, lot 795 will be maintained and lot 796 will be left unmaintained. A small portion of the ditch north of the placement (outside the test slab) was also excavated to accommodate a water collection system for testing purposes (Photo
3). The perforated pipes were 3 in. in diameter, 7 ft in length, and made from PVC.
2.2. Subbase fill
Once the excavation was complete, 6 in. of fractured clear crush with a maximum aggregate size of 3/ 4 in. was deposited above the subgrade. The fill was then compacted using a vibratory roller and measured to gain a uniform depth of 6 in.
Fig. 1. (a) Site location at BCIT’s Burnaby campus (inset – zoomed in view of the test slab). (b) Dimensions of the test slab.
Photo 1. Perforated pipes above the subgrade.
Photo 2. Perforated pipes on top of crush connecting to ABS pipes.
throughout the placement. Photo 4 shows the clear crush being compacted by the vibratory compactor. The background of Photo 4 also shows the simultaneous excavation of soil and the transportation of clear crush from a nearby deposited pile. The clear crush is necessary for pervious concrete as it acts as a storage medium and a filtration system for water passing through the pervious concrete. The crush also acts as a subbase for receiving th
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Trường hợp nghiên cứu trong vật liệu xây dựng 1 (2014) 1-9Nội dung danh sách có sẵn tại ScienceDirectTrường hợp nghiên cứu trong vật liệu xây dựngJour nal h omep tuổi: www.elsevie r .com/locat e/cscm Ngắn truyền thôngGiám sát hiệu suất tại chỗ thấm bê tông ở AnhColumbia — một phi công study§Rishi Gupta *Kỹ thuật xây dựng và môi trường chương trình, vùng kỹ thuật cơ khí, đại học Victoria, Canada R T TÔI C L E TÔI N F O Bài viết lịch sử:Nhận được 25 tháng 9 năm 2013Được chấp nhận ngày 3 tháng 10 năm 2013Từ khoá:Hệ thống thấm No-fines bê tông RavelingQuản lý nước mưaPhát triển bền vữngThay thế nhựa đường MỘT B S T R MỘT T C Cơ sở hạ tầng hiện đại ngày gọi cho việc sử dụng của bề mặt không thấm nước và hệ thống lề đường và gutter trên vỉa hè để nhanh chóng thu thập và vận chuyển mưa dòng chảy. Do nước mưa này đến các cơ quan nước nhận được nhanh chóng, trong khối lượng lớn và mang chất ô nhiễm nhiều hơn điều kiện tự nhiên. Các vỉa hè xốp trên bãi đậu xe, vỉa hè và driveways cung cấp một giải pháp cho vấn đề này. Một tài liệu có thể được sử dụng để tạo ra bề mặt xốp là thấm bê tông. Mặc dù hỗn hợp bê tông no-fines đã được sử dụng trong nhiều năm, có được vẫn còn nhiều vấn đề nổi bật liên quan đến hiệu quả cấu trúc của nó và các vấn đề với giảm percolation công suất theo thời gian đặc biệt là khi tiếp xúc với điều kiện thực tế. Bài báo này trình bày một trường hợp nghiên cứu mô tả một dự án ở British Columbia, Canada nơi1000 ft2 của nhựa đường được thay thế bằng một hệ thống cụ thể thấm. Các chi tiết của độc đáoxây dựng kỹ thuật bao gồm các chi tiết của các vật liệu được sử dụng được mô tả trong bài báo này. Ngày đi xét nghiệm để giám sát hiệu suất của các tấm sàn thử nghiệm này cũng được mô tả. 2013 tác giả. Được đăng bởi Elsevier Ltd. Tất cả các quyền. 1. giới thiệuQuản lý nước mưa đã trở thành một mối quan tâm cho các thành phố và đô thị do tăng đô thị hóa khu phố dân cư và thương mại. Trong một môi trường được xây dựng với significant số không thấm nước bề mặt và tích hợp hệ thống lề đường và gutter ở vỉa hè của chúng tôi, nước mưa đạt đến các cơ quan nước nhận được nhanh hơn nhiều, lớn hơn khối lượng và mang thêm chất ô nhiễm. Các thành phố và đô thị cùng với kỹ sư, các nhà nghiên cứu và phát triển khám phá những cách khác nhau để giảm các bề mặt không thấm nước và đối phó với quản lý nước mưa một cách bền vững và môi trường thân thiện. Xốp vỉa hè được tìm thấy là một biện pháp hiệu quả để giảm thiểu tác động của đô thị hóa môi trường. Mà không chiếm bất kỳ không gian bổ sung, xốp vỉa hè trên bãi đậu xe, vỉa hè và driveways cung cấp nhiều lợi, tức là khuyến khích infiltration, làm giảm đỉnh flows và dòng chảy khối lượng, cải thiện chất lượng nước, và làm giảm ô nhiễm nhiệt, do đó giúp đỡ để duy trì cân bằng sinh thái tinh tế của chúng tôi và môi trường chúng ta sống trong. Sử dụng vật liệu cho phép nước tràn ngập vào lòng đất giúp đóng góp vào bảng nước ngầm. Một tài liệu có thể được sử dụng để xây dựng vỉa hè xốp và bề mặt xốp đô thị là '' bê tông thấm ''. Loại bê tông có tính thấm cao và cho phép nước mưa để tràn ngập.Theo bền vững bê tông Canada (2012), Hệ thống cụ thể thấm có thể có tác động đến môi trường sau: loại bỏ thời gian và tốn kém bão nước tạm giam và hệ thống đường ống ngầm, cho phép nước, không khí và chất dinh dưỡng cây gốc thúc đẩy sức khỏe cây tăng trưởng mà không làm hư hỏng bề mặt vỉa hè của bạn, tăng số lượng nước mà có thể được giữ lại trên trang web của bạn và infiltrate vào các tầng ngậm nước do đó thúc đẩy nước lành mạnh• Đây là một bài viết mở truy cập phân phối theo các điều khoản của Creative Commons Attribution-NonCommercial-No Derivative tác phẩm License, cho phép sử dụng phi thương mại, phân phối và sinh sản trong môi trường bất kỳ, cung cấp các tác giả và nguồn gốc được ghi.* Điện thoại: + 1 250 721 7033 người.Địa chỉ e-mail: guptar@uvic.ca2214-5095 / $ – xem trước vấn đề 2013 tác giả. Được đăng bởi Elsevier Ltd. Tất cả các quyền. http://DX.Doi.org/10.1016/j.cscm.2013.10.001 mức độ mà duy trì chúng tôi suối và nước uống, loại bỏ chi phí của kiềm chế và máng xối, khai hoang có giá trị bất động sản nếu không tiêu thụ bởi nước mưa thùng và ao, ngăn chặn có hại hydrocarbon và các chất ô nhiễm khác tiếp cận của chúng tôi dòng nước đó thường xảy ra với hệ thống nước thông thường cơn bão. Thấm bê tông đang được sử dụng cho nhiều ứng dụng bao gồm sử dụng như một lát vật liệu đậu, nhẹ cấu trúc tường, Sân tennis và nhà kính floors (ACI Ủy ban 522, 2006). Thấm bê tông còn được gọi là '' no-fines'' bê tông. Bê tông thấm giảm ô nhiễm nước bão tại nguồn, kiểm soát cơn bão nước dòng chảy, và loại bỏ hoặc giảm kích thước của cơn bão cống (Schokker, 2010). Tuy nhiên, có rất nhiều vấn đề liên quan đến bê tông thấm vẫn cần phải được tiếp tục điều tra để cải thiện cuộc sống và hiệu suất trong dịch vụ của nó. Một số trong những vấn đề hiện tại cho thấm bê tông là như sau.1.1. nghẽnKhi các tài liệu nhỏ chẳng hạn như cát bụi bẩn và fine được thực hiện bởi cơn bão nước thông qua các lỗ chân lông của thấm bê tông, các mảnh vỡ có thể cuối cùng làm giảm hiệu quả của hệ thống thoát nước và tính thấm của bê tông. Tắc nghẽn như vậy sau đó có thể dẫn đến flooding và bê tông được dễ bị chu kỳ đóng băng-tan băng rộng rãi (Deo et al., 2010). Một trong những vấn đề liên quan đến điều này là yêu cầu để duy trì các tấm bằng quyền lực thường xuyên rửa để unclog các lỗ chân lông.1.2. chịu mài mònNhư các liên kết trong thấm bê tông là tổng hợp tổng hợp chứ không phải là sự tổng hợp nhúng trong một dán hợp như thường xuyên bê tông, bê tông thấm có nghèo hơn các tính chất cơ học. Thấm bê tông là dễ bị thất bại mài mòn do trình bề mặt được đeo hoặc nghiền nát dưới traffic tải (Wu và ctv., năm 2011). Hiện tượng này đôi khi được gọi là '' raveling.''1.3. đóng băng và tan băngKhi thấm bê tông được tiếp xúc với khí hậu lạnh, có là một khả năng bê tông sẽ trải qua một rộng rãi đóng băng-tan băng chu kỳ nếu vị trí đầy đủ được bão hòa. Điều này dẫn đến áp lực trên dán mỏng xi măng xung quanh các uẩn và sự mất độ bền của bê tông (Kevern và ctv., 2010).To study these issues, a project was recently initiated by the author at British Columbia Institute of Technology (BCIT) in Canada. This project involved replacing a section of the asphalt paved surface in a parking lot with pervious concrete. The aim of this project is to determine the feasibility of using pervious concrete on a larger scale, especially as an alternative to using asphalt for paving. The pilot slab is being exposed to real environmental conditions and traffic. The observations and test results from this study will help address above-mentioned issues and determine the feasibility of using larger placements in the future especially when using in regions that are prone to freeze–thaw cycles. In this paper, the procedure used to construct this non-traditional system of pervious concrete as a pavement is discussed and the on-going tests to monitor the performance of the pavements are described. Some of the initial test results are also presented.2. Construction detailsThe site is located at the northern area of Parking Lot F at the Burnaby campus of BCIT, Canada (Fig. 1a). The placement size is 24 ft 40 ft, and covers three parking stalls (794, 795, and 796) and the roadway adjacent to it. The site location was specifically chosen to study the effect of standing traffic, moving traffic, and turning vehicles.The construction of the concrete slab was completed in three major stages: excavation and asphalt removal, subbase fill, and the concrete placement and curing. The details of each are described below.2.1. khai quậtNhựa đường hiện tại là thấy cắt cạnh thẳng mẫu và khai quật sâu 12 in đã được thực hiện. Đất bên dưới vỉa hè nhựa đường bao gồm đất cát cho top 6 in, và đất sét cát trong 6 thấp trong. Bộ đục lỗ ống được đặt bên dưới làn xe 795 và 796 tọa lạc phía tây cuối của bài kiểm tra tấm (hình 1b). Một bộ được đặt ở dưới cùng của lòng rõ ràng và một ở cuối 6 in dày thấm tấm sàn bê tông (hình ảnh 1 và 2). Riêng biệt ống được sử dụng ở mỗi cấp theo nhiều 795 và796 để nghiên cứu việc giảm công suất percolation (nếu có) bằng cách không duy trì (điện rửa) một phần của vỉa hè. Trong nghiên cứu này, nhiều 795 sẽ được duy trì và nhiều 796 sẽ còn lại unmaintained. Một phần nhỏ của mương về phía bắc của vị trí (ngoài các tấm sàn thử nghiệm) cũng đã được khai quật để chứa một hệ thống thu gom nước cho mục đích (ảnh thử nghiệm3). ống đục lỗ là in 3 đường kính, 7 ft dài, và được làm từ nhựa PVC.2.2. subbase fillSau khi khai quật là hoàn thành, 6 in bị vỡ lòng rõ ràng với một kích thước tối đa tổng hợp của 3 / 4 in được gửi trên subgrade. fill là sau đó đầm bằng cách sử dụng một con lăn rung và đo để đạt được độ sâu 6 trong đồng phục. Hình 1. (a) trang web các vị trí tại cơ sở của BCIT Burnaby (ghép-thu nhỏ trong xem các tấm sàn thử nghiệm). (b) kích thước của các tấm sàn thử nghiệm. Ảnh 1. Đục lỗ ống ở trên subgrade. Photo 2. Perforated pipes on top of crush connecting to ABS pipes.throughout the placement. Photo 4 shows the clear crush being compacted by the vibratory compactor. The background of Photo 4 also shows the simultaneous excavation of soil and the transportation of clear crush from a nearby deposited pile. The clear crush is necessary for pervious concrete as it acts as a storage medium and a filtration system for water passing through the pervious concrete. The crush also acts as a subbase for receiving th
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Case Studies in Construction Materials 1 (2014) 1–9
Contents lists available at ScienceDirect
Case Studies in Construction Materials
jour nal h omep age: www.elsevie r .com/locat e/cscm
Short Communication
Monitoring in situ performance of pervious concrete in British
Columbia—A pilot study§
Rishi Gupta *
Civil & Environmental Engineering Program, Department of Mechanical Engineering, University of Victoria, Canada
A R T I C L E I N F O
Article history:
Received 25 September 2013
Accepted 3 October 2013
Keywords:
Pervious concrete system No-fines concrete Raveling
Stormwater management
Sustainability
Asphalt replacement
A B S T R A C T
Modern day infrastructure calls for use of impervious surfaces and curb and gutter systems on pavements to rapidly collect and transport rain runoff. Due to this stormwater reaches the receiving water bodies rapidly, in greater volume and carries more pollutants than natural conditions. Porous pavement on parking lots, sidewalks, and driveways provides a solution to this problem. One such material that can be used to produce porous surfaces is pervious concrete. Even though no-fines concrete mix has been used for many years, there are still many outstanding issues related to its structural performance and issues with reduced percolation capacity over time especially when exposed to real conditions. This paper presents a case study describing a project in British Columbia, Canada where
1000 ft2 of asphalt was replaced with a pervious concrete system. The details of the unique
construction technique including details of the material used are described in this paper. On-going tests to monitor the performance of this test slab are also described.
2013 The Author. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Stormwater management has become a concern for cities and municipalities due to increased urbanization of residential and commercial neighborhoods. In a built environment with significant amount of impervious surfaces and integration of curb and gutter systems in our pavements, stormwater reaches the receiving water bodies much faster, in greater volume and carries more pollutants. Cities and municipalities along with engineers, researchers and developers are exploring different ways to reduce the impervious surfaces and to deal with stormwater management in a sustainable and environment friendly manner. Porous pavement is found to be an effective measure to mitigate the impact of urbanization on the environment. Without occupying any additional space, porous pavement on parking lots, sidewalks, and driveways provides multiple benefits, i.e. promotes infiltration, reduces peak flows and runoff volume, improves water quality, and reduces thermal pollution, thus helping to maintain our delicate ecological balance and the environment we live in. Using materials that allow water to permeate into the ground helps contribute to the ground water table. One such material that can be used to construct porous pavements and porous urban surfaces is ‘‘pervious concrete.’’ This type of concrete has high permeability and allows rain water to permeate.
According to Sustainable Concrete Canada (2012), the pervious concrete system can have the following impact on the environment: eliminating time consuming and costly storm water detention facilities and underground piping systems, allowing water, air and nutrients to tree roots promoting healthy tree growth without damaging your pavement surface, increasing the quantity of water which can be retained on your site and infiltrate into aquifers thus promoting healthy water
§ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
* Tel.: +1 250 721 7033.
E-mail address: guptar@uvic.ca
2214-5095/$ – see front matter 2013 The Author. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cscm.2013.10.001
levels which sustain our streams and drinking water, eliminating the expense of curbs and gutters, reclaiming valuable property otherwise consumed by stormwater tanks and ponds, preventing harmful hydrocarbons, and other pollutants from reaching our waterways which commonly occur with conventional storm water systems. Pervious concrete is being used for many applications including use as a paving material for parking lots, lightweight structural walls, tennis courts, and greenhouse floors (ACI Committee 522, 2006). Pervious concrete is also known as ‘‘no-fines’’ concrete. Pervious concrete reduces storm water pollution at the source, control storm water runoff, and eliminate or reduce the size of storm sewers (Schokker, 2010). However, there are many issues related to pervious concrete that still need to be further investigated to improve its life and performance during service. Some of the current issues for pervious concrete are as follows.
1.1. Clogging
When small material such as dirt and fine sand are carried by storm water through the pores of pervious concrete, the debris can eventually reduce the effectiveness of the drainage and permeability of the concrete. Such clogging could then lead to flooding and the concrete being susceptible to extensive freeze–thaw cycles (Deo et al., 2010). One issue associated with this is the requirement to maintain the slabs by frequent power washing to unclog the pores.
1.2. Abrasion resistance
As the bonding in pervious concrete is aggregate-to-aggregate rather than the aggregate embedded in a cementitious paste like in regular concrete, pervious concrete has poorer mechanical properties. Pervious concrete is susceptible to abrasion failure caused by the surface course being worn off or crushed under traffic loads (Wu et al., 2011). This phenomenon is sometimes referred to as ‘‘raveling.’’
1.3. Freeze and thaw
When pervious concrete is exposed to cold climates, there is a possibility the concrete would undergo extensive freeze– thaw cycles if the placement was fully saturated. This leads to pressure on the thin cement paste surrounding the aggregates and a loss of durability of the concrete (Kevern et al., 2010).
To study these issues, a project was recently initiated by the author at British Columbia Institute of Technology (BCIT) in Canada. This project involved replacing a section of the asphalt paved surface in a parking lot with pervious concrete. The aim of this project is to determine the feasibility of using pervious concrete on a larger scale, especially as an alternative to using asphalt for paving. The pilot slab is being exposed to real environmental conditions and traffic. The observations and test results from this study will help address above-mentioned issues and determine the feasibility of using larger placements in the future especially when using in regions that are prone to freeze–thaw cycles. In this paper, the procedure used to construct this non-traditional system of pervious concrete as a pavement is discussed and the on-going tests to monitor the performance of the pavements are described. Some of the initial test results are also presented.
2. Construction details
The site is located at the northern area of Parking Lot F at the Burnaby campus of BCIT, Canada (Fig. 1a). The placement size is 24 ft 40 ft, and covers three parking stalls (794, 795, and 796) and the roadway adjacent to it. The site location was specifically chosen to study the effect of standing traffic, moving traffic, and turning vehicles.
The construction of the concrete slab was completed in three major stages: excavation and asphalt removal, subbase fill, and the concrete placement and curing. The details of each are described below.
2.1. Excavation
The existing asphalt was saw cut to form straight edges and 12 in. deep excavation was done. The soil below the asphalt pavement consisted of sandy soil for the top 6 in., and sandy clay in the lower 6 in. Sets of perforated pipes were placed below lanes 795 and 796 located at west end of the test slab (Fig. 1b). One set was placed at the bottom of the clear crush and one at the bottom of the 6 in. thick pervious concrete slab (Photos 1 and 2). Separate pipes were used at each level under lot 795 and
796 to study the reduction in percolation capacity (if any) by not maintaining (power washing) one section of the pavement. In this study, lot 795 will be maintained and lot 796 will be left unmaintained. A small portion of the ditch north of the placement (outside the test slab) was also excavated to accommodate a water collection system for testing purposes (Photo
3). The perforated pipes were 3 in. in diameter, 7 ft in length, and made from PVC.
2.2. Subbase fill
Once the excavation was complete, 6 in. of fractured clear crush with a maximum aggregate size of 3/ 4 in. was deposited above the subgrade. The fill was then compacted using a vibratory roller and measured to gain a uniform depth of 6 in.
Fig. 1. (a) Site location at BCIT’s Burnaby campus (inset – zoomed in view of the test slab). (b) Dimensions of the test slab.
Photo 1. Perforated pipes above the subgrade.
Photo 2. Perforated pipes on top of crush connecting to ABS pipes.
throughout the placement. Photo 4 shows the clear crush being compacted by the vibratory compactor. The background of Photo 4 also shows the simultaneous excavation of soil and the transportation of clear crush from a nearby deposited pile. The clear crush is necessary for pervious concrete as it acts as a storage medium and a filtration system for water passing through the pervious concrete. The crush also acts as a subbase for receiving th
Contents lists available at ScienceDirect
Case Studies in Construction Materials
jour nal h omep age: www.elsevie r .com/locat e/cscm
Short Communication
Monitoring in situ performance of pervious concrete in British
Columbia—A pilot study§
Rishi Gupta *
Civil & Environmental Engineering Program, Department of Mechanical Engineering, University of Victoria, Canada
A R T I C L E I N F O
Article history:
Received 25 September 2013
Accepted 3 October 2013
Keywords:
Pervious concrete system No-fines concrete Raveling
Stormwater management
Sustainability
Asphalt replacement
A B S T R A C T
Modern day infrastructure calls for use of impervious surfaces and curb and gutter systems on pavements to rapidly collect and transport rain runoff. Due to this stormwater reaches the receiving water bodies rapidly, in greater volume and carries more pollutants than natural conditions. Porous pavement on parking lots, sidewalks, and driveways provides a solution to this problem. One such material that can be used to produce porous surfaces is pervious concrete. Even though no-fines concrete mix has been used for many years, there are still many outstanding issues related to its structural performance and issues with reduced percolation capacity over time especially when exposed to real conditions. This paper presents a case study describing a project in British Columbia, Canada where
1000 ft2 of asphalt was replaced with a pervious concrete system. The details of the unique
construction technique including details of the material used are described in this paper. On-going tests to monitor the performance of this test slab are also described.
2013 The Author. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Stormwater management has become a concern for cities and municipalities due to increased urbanization of residential and commercial neighborhoods. In a built environment with significant amount of impervious surfaces and integration of curb and gutter systems in our pavements, stormwater reaches the receiving water bodies much faster, in greater volume and carries more pollutants. Cities and municipalities along with engineers, researchers and developers are exploring different ways to reduce the impervious surfaces and to deal with stormwater management in a sustainable and environment friendly manner. Porous pavement is found to be an effective measure to mitigate the impact of urbanization on the environment. Without occupying any additional space, porous pavement on parking lots, sidewalks, and driveways provides multiple benefits, i.e. promotes infiltration, reduces peak flows and runoff volume, improves water quality, and reduces thermal pollution, thus helping to maintain our delicate ecological balance and the environment we live in. Using materials that allow water to permeate into the ground helps contribute to the ground water table. One such material that can be used to construct porous pavements and porous urban surfaces is ‘‘pervious concrete.’’ This type of concrete has high permeability and allows rain water to permeate.
According to Sustainable Concrete Canada (2012), the pervious concrete system can have the following impact on the environment: eliminating time consuming and costly storm water detention facilities and underground piping systems, allowing water, air and nutrients to tree roots promoting healthy tree growth without damaging your pavement surface, increasing the quantity of water which can be retained on your site and infiltrate into aquifers thus promoting healthy water
§ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
* Tel.: +1 250 721 7033.
E-mail address: guptar@uvic.ca
2214-5095/$ – see front matter 2013 The Author. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cscm.2013.10.001
levels which sustain our streams and drinking water, eliminating the expense of curbs and gutters, reclaiming valuable property otherwise consumed by stormwater tanks and ponds, preventing harmful hydrocarbons, and other pollutants from reaching our waterways which commonly occur with conventional storm water systems. Pervious concrete is being used for many applications including use as a paving material for parking lots, lightweight structural walls, tennis courts, and greenhouse floors (ACI Committee 522, 2006). Pervious concrete is also known as ‘‘no-fines’’ concrete. Pervious concrete reduces storm water pollution at the source, control storm water runoff, and eliminate or reduce the size of storm sewers (Schokker, 2010). However, there are many issues related to pervious concrete that still need to be further investigated to improve its life and performance during service. Some of the current issues for pervious concrete are as follows.
1.1. Clogging
When small material such as dirt and fine sand are carried by storm water through the pores of pervious concrete, the debris can eventually reduce the effectiveness of the drainage and permeability of the concrete. Such clogging could then lead to flooding and the concrete being susceptible to extensive freeze–thaw cycles (Deo et al., 2010). One issue associated with this is the requirement to maintain the slabs by frequent power washing to unclog the pores.
1.2. Abrasion resistance
As the bonding in pervious concrete is aggregate-to-aggregate rather than the aggregate embedded in a cementitious paste like in regular concrete, pervious concrete has poorer mechanical properties. Pervious concrete is susceptible to abrasion failure caused by the surface course being worn off or crushed under traffic loads (Wu et al., 2011). This phenomenon is sometimes referred to as ‘‘raveling.’’
1.3. Freeze and thaw
When pervious concrete is exposed to cold climates, there is a possibility the concrete would undergo extensive freeze– thaw cycles if the placement was fully saturated. This leads to pressure on the thin cement paste surrounding the aggregates and a loss of durability of the concrete (Kevern et al., 2010).
To study these issues, a project was recently initiated by the author at British Columbia Institute of Technology (BCIT) in Canada. This project involved replacing a section of the asphalt paved surface in a parking lot with pervious concrete. The aim of this project is to determine the feasibility of using pervious concrete on a larger scale, especially as an alternative to using asphalt for paving. The pilot slab is being exposed to real environmental conditions and traffic. The observations and test results from this study will help address above-mentioned issues and determine the feasibility of using larger placements in the future especially when using in regions that are prone to freeze–thaw cycles. In this paper, the procedure used to construct this non-traditional system of pervious concrete as a pavement is discussed and the on-going tests to monitor the performance of the pavements are described. Some of the initial test results are also presented.
2. Construction details
The site is located at the northern area of Parking Lot F at the Burnaby campus of BCIT, Canada (Fig. 1a). The placement size is 24 ft 40 ft, and covers three parking stalls (794, 795, and 796) and the roadway adjacent to it. The site location was specifically chosen to study the effect of standing traffic, moving traffic, and turning vehicles.
The construction of the concrete slab was completed in three major stages: excavation and asphalt removal, subbase fill, and the concrete placement and curing. The details of each are described below.
2.1. Excavation
The existing asphalt was saw cut to form straight edges and 12 in. deep excavation was done. The soil below the asphalt pavement consisted of sandy soil for the top 6 in., and sandy clay in the lower 6 in. Sets of perforated pipes were placed below lanes 795 and 796 located at west end of the test slab (Fig. 1b). One set was placed at the bottom of the clear crush and one at the bottom of the 6 in. thick pervious concrete slab (Photos 1 and 2). Separate pipes were used at each level under lot 795 and
796 to study the reduction in percolation capacity (if any) by not maintaining (power washing) one section of the pavement. In this study, lot 795 will be maintained and lot 796 will be left unmaintained. A small portion of the ditch north of the placement (outside the test slab) was also excavated to accommodate a water collection system for testing purposes (Photo
3). The perforated pipes were 3 in. in diameter, 7 ft in length, and made from PVC.
2.2. Subbase fill
Once the excavation was complete, 6 in. of fractured clear crush with a maximum aggregate size of 3/ 4 in. was deposited above the subgrade. The fill was then compacted using a vibratory roller and measured to gain a uniform depth of 6 in.
Fig. 1. (a) Site location at BCIT’s Burnaby campus (inset – zoomed in view of the test slab). (b) Dimensions of the test slab.
Photo 1. Perforated pipes above the subgrade.
Photo 2. Perforated pipes on top of crush connecting to ABS pipes.
throughout the placement. Photo 4 shows the clear crush being compacted by the vibratory compactor. The background of Photo 4 also shows the simultaneous excavation of soil and the transportation of clear crush from a nearby deposited pile. The clear crush is necessary for pervious concrete as it acts as a storage medium and a filtration system for water passing through the pervious concrete. The crush also acts as a subbase for receiving th
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- 5.2.5 Relationships between strength and
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