2 LA TECNOLOGÍA
2.5 Análisis de las principales BPMS
2.5.1 jBPM
Sowjanya1 and J. Jaya Vardhan2
1Assistant Professor, Civil Engg. Dept., G.Pulla Reddy Engineering College, Kurnool
2B.Tech Student, Pulla Reddy Engineering College, Kurnool
ABSTRACT
As asphalt becomes more expensive and in short supply, and as the need to manage storm water runoff increases, designers must revisit old assumptions and take a fresh look at how pavements need to work in a sustainable environment, and how to design and specify for them. Pervious pavements are a recent addition to the list of viable paving options, but as yet, there have been few ways to design them and to effectively predict their performance. This article offers some help to accomplish those tasks. In many situations, pervious concrete simply replaces an impervious surface. In other cases, the pervious concrete pavement system must be designed to handle much more rainfall than will fall on the pavement itself. Various test were conducted on aggregate and cement are obtained with in the specified limits. It is observed that the strength of concrete is 28.69 kg/cm2 for 28 days and may be concluded that the pervious concrete may be used at various places like parking lots, footpaths, side drainages, curbs and for gutters.
Keywords— Pervious Concrete, Storm Water, Ground Water Table INTRODUCTION
Pervious concrete pavement is a unique and effective means to meet growing environmental demands. By capturing rainwater and allowing it to seep into the ground, pervious concrete is instrumental in recharging groundwater, reducing storm water runoff.
In pervious concrete, carefully controlled amount of water and cementitious materials are used to create a paste that forms a thick coating around aggregate particles. A pervious concrete mixture contains little or no sand, creating a substantial void content. Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly.
While pervious concrete can be used for a surprising number of applications, its primary use is in pavement.
This report will focus on the pavement applications of the material, which also has been referred to as porous concrete, permeable concrete, no-fines concrete, gap-graded concrete, and enhanced-porosity concrete.
Objectives
The main objectives of pervious concrete are as follows:
To drain the surface water in to the ground and ultimately to recharge the ground water table in a shorter span of time when compared to the actual or normal recharging of ground water.
To drain off the surface water into the nearby streams without pollution of the water.
To manage the storm water in a systematic manner.
MIX PROPORTIONS
Pervious concrete uses the same materials as conventional concrete, with the exceptions that the fine aggregate typically is eliminated entirely, and the size distribution (grading) of the coarse aggregate is kept narrow, allowing for relatively little particle packing.
Cementitious Materials
Portland cement is used for pervious concrete in our study.
Aggregate
Fine aggregate content is limited in pervious concrete and coarse aggregate is kept to a narrow gradation. Single-sized aggregate up to 25 mm has been used.Larger aggregates provide a rougher surface.A/C ratios of 4.5 by mass with rounded aggregate and angular aggregate have been used to produce pervious concrete is considered in laboratory studies.
Water
Water content should be tightly controlled. Water to cementitious materials ratios of 0.36 is been used successfully. A handful of pervious concrete formed into a ball will not crumble or lose its void structure as the paste flows into the spaces between the aggregates is an indication that it has enough water content for binding purpose. If there is less amount of water content the aggregates will not form into a proper group and gets separated.
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development
Pervious Concrete for Stormwater Management Runoff Control
There are a variety of controls to manage storm water runoff from a site. These control measures may address different aspects of runoff: storage runoff water, infiltration of storm water to groundwater, and treatment of the pollutants in storm water. Proper peak runoff rate control helps prevent adverse impacts such as stream channel scouring and bank alteration and minimizes downstream flooding and stream bank erosion. In general, protection from stream bank erosion requires the control of frequent flooding events (i.e., the 2-year and smaller storm events). These storms have the most influence on stream channel formation. Protection from less common, offsite flooding requires the control of storm events which exceed stream channel bankfull capacity (i.e., the 10-year and higher events).
Engineers may design drainage systems or other physical structures, suc as detention and infiltration basins, pretreatment devices, and sw manage stormwater.
Nonstructural approaches also may control or reduce stormwater runoff. For example, by reducing the building footprint while increasing the building height, more grassy areas can be preserved and new impervious surfaces can be minimized.
Nonstructural and structural Best Management Practices (BMPs) are recognized as the most effective and practical measures to reduce or prevent pollutants from reaching water bodies and to control the quantity of runoff from a site. However, storm water BMP technologies range in their ability and effectiveness to treat specific pollutant types. Depending on the receiving resources, the pollutant type of concern will vary. For drinking water supplies, inorganic compounds, volatile organic compounds, pesticides, herbicides, and pathogens (bacteria and viruses) are the main concern. For shellfish growing areas and recreation areas, bacterial contamination and nutrients are primary concerns, while temperature and pH are the major concerns for cold water fisheries.
Pervious concrete has been recognized as one of the best practices for managing storm water by EPA (Environment Protection Agency).
Benefits
1. Recharges groundwater.
2. Reduction in storm water infrastructure (Piping, Catch-Basins, Ponds, Curbing, etc.).
3. Suitable for cold-climate applications, maintains recharge capacity when frozen.
4. No standing water or black ice development during winter weather conditions.
5. Maintains traction while wet.
6. Reduced surface temperatures; minimizes the urban heat island effect.
7. Extended pavement life due to well drained base and reduced freeze-thaw.
8. Less lighting needed due to highly reflective pavement surface.
9. Requires routine (quarterly) vacuum sweeping (vacuum-assisted dry sweeper only).
10. Requires a certified pervious concrete craftsman on-site during installation.
EXPERIMENTAL WORK
Laboratory Test for Cement, Coarse Aggregate and Pervious Concrete
Brand of cement used: JSW (OPC) Fineness of Cement Test
Table 3.1: Fineness of Cement test
Trail
Result— Fineness of the cement is 6 Specific Gravity of Cement
Liquid used : kerosene
Density of Liquid at room temperature : 0.8 Weight of cement taken : 64 gm.
Table 3.2: Specific Gravity of Cement S.
Result— Specific Gravity of the Cement is 3.37.
Consistency of Cement Paste Weight of cement taken = 400 gm
Table 3.3: Consistency of Cement paste Trial
Use of Pervious Concrete in Increasing Ground Water Table
Result— Standard consistency of cement is 35.5 % Initial Setting Time & Final Setting Time Weight of cement taken = 400gm.
Percentage Weight of water taken= 0.85 P =. 85 X 35.5 = 30.175
Where P is the normal consistency.
Weight of water taken = 30.175 x 400/100 = 121 gm.
Table 3.4: Initial setting time and final setting time test No. S. Initial
Result— Initial setting time of cement: 70 min Final setting time of cement: 170 min
Specific Gravity of Coarse Aggregate
1. Weight of dry and empty pycnometer (w1) = 599 gm.
2. Weight of pycnometer + coarse aggregate (w2) = 1101 gm.
Result— Specific gravity = ______ w5 ______
( W2 – W1 )- (W3 – W4) = 500 = 2.71 (1101-599)–(1898-1500) COEFFICIENT OF PERMEABILITY BY CONSTANT HEAD METHOD FOR PERVIOUS CONCRETE
Length of the sample = L = 12.73 cm Diameter of specimen = D = 10 cm Area of specimen = A = 78.539 cm2
Table 3.6: Coefficient of permeability using constant head method test
Result— Coefficient of permeability of pervious concrete sample is K = 0.0219 cm/sec
COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE
Test observations for pervious concrete of aggregate sizes in the ranges which are taken for study are in range of (10mm –12.5 mm ) & (16 mm – 20 mm)
Table 3.7: Compressive strength of Pervious concrete test S no Size in mm Loads at crushing
Unit Weight of Pervious Concrete is = 1815 kg/ m3 Void Ratio & Porosity of Pervious Concrete:
a) Specific gravity of cement = 3.37 Mass of cement = 1 kg = 1000 gm
Volume of cement = Vc = 1000/3.37 = 296.74 cm3 b) Specific gravity of aggregate = 2.71
Mass of aggregate = 4.5 KG = 4500 gm
Volume of aggregate = Va = 4500/2.71 = 1660.52 cm3 c) Volume of cube = V = 15 x 15 x 15 = 3375 cm3 aggregate and on pervious concrete. They are summerised and are shown in the tabular form below.
The test procedure done in the laboratory is as follows.
The mix proportions are taken as mentioned above i.e., A/C ratios of 4.5 by mass and W/C of 0.36. First the course aggregate and cement are mixed well without
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development adding water to it so that the aggregate can be coated with
cement as shown in the figure 1.
Table 1: Results of Tests conducted on materials S.
No Test Result
1. Fineness of Cement 6%
2. Specific Gravity of Cement 3.37 3. Consistency of Cement 35.5%
4. Initial setting Time Of Cement 70 min.
5. Final Setting Time of Cement 170 min.
6. Specific Gravity of Coarse
Aggregate 2.71
7. Co- efficient of Permeability by Constant Head Method
0.0219 cm/sec 8. Compressive strength of Pervious
Concrete 2.815
N/mm2 9. Unit Weight of Pervious Concrete 1815 kg/m3 10
. Void ratio of Pervious Concrete 0.724 11
. Porosity of Pervious Concrete 0.42
Fig. 1: Aggregate & Cement dry Mix
Fig. 2: Water to Cement ratio at 0.36
Later water is added and mixed properly as shown in the figure 2. The cement concrete mix is placed in the mould
by placing a minimum 6 ml poly sheeting at the bottom as shown in the figure 3. It prevents the shrinking of concrete due to evaporation of water content present in the cement concrete mix.
Fig. 3: Setup Box Made up of Wooden
Fig. 4: Preparation of Pervious Concrete
Fig. 5: Curing for prepared sample
Fig. 6: Pervious Concrete sample
Use of Pervious Concrete in Increasing Ground Water Table The concrete is then cured for a period of 7 days by
spraying the surface with soya bean oil. as shown in the figure 5.
Prepared Pervious Concrete sample is tested as shown in Figure7.
Fig. 7: Testing of prepared sample CONCLUSIONS
Pervious concrete is considered as best practice for storm water management and has wide applications in areas with huge runoff.
The idea is to demonstrate the permeability and engineering properties and use pervious concrete effectively in areas where its use is little known.
LIMITATIONS
1. Test results were obtained without using of admixtures.
2. Permeability test is confined to constant head and single drainage conditions only but not with respect to
actual site conditions like usage of double ring infiltrometer apparatus.
3. Test has been limited to pervious concrete only but not when the pervious concrete is on the subgrade.
SCOPE FOR RESEARCH
The main drawback of pervious concrete is less compressive strength. Efforts can be made to increase the compressive strength of pervious concrete using suitable admixtures, keeping in mind the financial constraint. The other problems are making pervious concrete more resistant in freeze and thaw conditions.
Pervious concrete and its engineering properties can also be utilised to store water in residential communities. In areas where compressive strength is not the primary criteria, and there is huge runoff, pervious concrete can be of wide use.
REFERENCES
[1] A.M Neville “Properties of Concrete”.
[2] “Concrete in practice, what why and how” NRMCA CIP-38 “Pervious Concrete”.
[3] Pervious concrete pavements by “Paul D. Tennis, Michael L. Leming, and David J. Akers”.
[4] Pervious concrete pavement assessment by “Marty Wanielista, Manoj Chopra”, Storm water management academy, University of Central Florida, Orlando.
[5] AASHTO, Guide for Design of Pavement Structures, American Association of State Highway and Transportation.
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development (ACEID-2014), Vasavi College of Engineering, Hyderabad, A.P. 6 - 7 February, 2014. pp.118-123.