ASTM C() in English | Standard Specification for Joints for Concrete Pipe and Manholes, Using Rubber Gaskets. PDF | The hydrostatic performance of reinforced concrete pipe (RCP) depends on the Download full-text PDF . such as CSA A, ASTM C, ASTM C and BS EN require horizontal pipe sections to be. be designed to prevent all infiltration/exfiltration of the manhole. Consult ASTM C for watertight joints. Storm manholes on the other hand should be designed .
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ASTM C—12 Standard Specification for Joints for Concrete Pipe and This convenient option is a searchable PDF download that requires a PDF Reader. ASTM C With Butyl - Download as PDF File .pdf), Text File .txt) or read online. Juntas. ASTM's early history was in large . Pressure Pipe. C Joints for Circular Concrete Sewer . ASTM C Standard Specification for Joints for Circular.
Box Culverts are designed for horizontal installations and loading conditions. Custom box structures are easily fabricated using universal forming equipment. A general rule of thumb is to provide a minimum of 6 inches as measured from the interior of the structure. Most roadways and some stormwater site drainage systems employ these types of structures. Various sizes of pipes entering at different angles can more easily be accommodated by a round structure, ensuring watertight connections are maintained. However, this practice may be necessary for certain installations and should be left to the discretion of an experienced precast concrete manufacturer. Minimum compressive strength shall be 4, psi.
A system of restraining bars and clamps holds the units together while pressure is applied.
Without the restraints, the pressure lifts the assembly apart. The restraints simulate the weight of concrete and soil that would naturally bear down on the structure if it were buried the thirty feet under water, necessary to achieve the test pressures. The ends of the butyl are kneaded together by hand to ensure a continuous gasket. Dry fit procedures, done before testing, reveal a close and even fit.
Bite-wing testing reveals the same close fit within the joint. Once assembled, the lower bladder is inflated to 55 psi. This seals the area below joint so that water is held in the center portion.
By a garden hose, water is filled into the center section to about 4 inches above the joint. The upper blad- der is inflated to 55psi. This seals the upper area so that water under pressure is held at the joint. Dry-fit with no gasket material Prepared for bite-wing test Air is pumped into the center portion to a regulated pressure of Visual inspection of the outside showed zero leakage at the end of the ten minutes.
Further, to disassemble the test rig, all restraints were removed and pressure introduced into the center portion. The sewage is now more concentrated and more corrosive. Within the last decade, the ability to see inside an installed sewer pipe via remotely controlled closed circuit television has allowed engineers to actually view the results of ongoing MIC.
The current state of the infrastructure has encouraged municipalities to design their structures for maximum longevity. The Greater Houston Wastewater program represents one of the United States largest wastewater utilities .
This story is repeated over and over in large and small municipalities around the world . Engineers must design to combat MIC in order to increase the longevity of the sewer system and to make the system more economical and cost effective. Parker in was one of the first to report the source of microbial induced corrosion MIC as the bacteria known as Thiobacillus .
This corrosion process is sometimes incorrectly referred to as hydrogen sulfide H2S corrosion. H2S alone is not corrosive to concrete whatsoever. It is the sulfuric acid H2SO4 that is produced when the Thiobacillus bacteria metabolize the H2S that actually corrodes the concrete. It is beyond the scope of this paper to detail the complete MIC cycle.
When the wastewater steam is anaerobic no oxygen is present , sulfatereducing bacteria, existing in the slime layer in the invert of the pipe, convert the naturally occurring sulfates in the wastewater into H2S. Numerous factors lead to greater H2S production. It is a well-known fact that warmer temperatures result in more bacterial activity and greater H2S production.
Also, geographic regions with greater nutrients B. The flow rate of the pipeline is a very significant factor as well. Lines with low or stagnant flows have a greater tendency to become septic and provide more anaerobic conditions for the production of HzS. Greater flow rates help to introduce oxygen into the wastewater to prevent the system from becoming anaerobic. Higher flow rates also tend to clean away the slime layer to reduce the quantity of bacteria that can produce H2S.
Released H2S gas reacts with the moisture in the crown area to form dilute acids. The dilute acids reduce the pH on the surface of the concrete from its normal level of 11 or 12 to approximately pH 7 [fresh concrete pH measures approximately Successive generations of the bacteria continue to produce the acid and lower the pH to approximately 0.
Once the pH drops below approximately 1. It should be noted that MIC occurs in the crown area of the pipe above the water line.
If the area below the water line is corroded, it is most likely erosion caused by excessive velocities or abrasive materials in the pipe. Corrosion below the water line could be caused by other acids and chemicals in the waste stream as well.
One of the most significant design changes to occur in the last 18 years is the development of computer programs for sulfide and corrosion prediction. The most recent versions of these programs allow the user to analyze an entire system for sulfide generation and corrosion potential.
When verified and calibrated, the model is a powerful tool which can be used to analyze the varying conditions anticipated throughout the life of the wastewater collection system. Using the manual method, this same analysis would require extensive time and severely limit the size of the project, which could be analyzed, and the detail of analysis, which could be performed. The impact of diversions, future flows, and changes in wastewater characteristics can all be analyzed before potentially costly decisions are made.
The most recent generation of programs published for sulfide generation and corrosion prediction are HS and Sulfide Works. Both were published in Sulfide Works was developed by MicroComp Systems. The HS program is limited to pipes flowing partially full. This limitation requires manual input when modeling siphons or force mains.
Sulfide Works' program handles either full-flowing pipes or partially full pipes.
When evaluating a system's sulfide potential, it may be necessary to simulate varied conditions. The programs provide various options, including constant or variable quantity or depth of flow and incremental life analysis, to account for variable flow quantities of depths during the sewer life, and will take into account the effect of input sulfide at junctions.
For primary data input, sewage characteristics required are: climatic BOD, sewage temperature, design life [which may be broken into increments], acid reaction factor "k", pH of the sewage, upstream total sulfide level, insoluble sulfides, and the climatic ratio "c". The programs prompt for the number of reaches to be analyzed; then for the pipe diameter, slope and length of reach for each reach in succession, beginning at the upstream end of the sewer.
With the information provided by the software programs, and more specifically the "snapshot" information available from the ACPA Hydrogen Sulfide Prediction software, the designer can work with different "what it" scenarios to determine the best design for the wastewater system. These are important to the specific application, both at present and in the future. Today's designer can have the modem day equivalent of a crystal ball, which allows the estimation of tomorrow's Operations, Maintenance, and Replacement OMR costs.
H2S Modeling Design Method software is used in estimating the future costs ofwastewater systems. Pipe and all the other components of the wastewater system can be initially designed, rehabilitated or studied for future design and maintenance costs. Community expansion, real time and planned, can be accommodated by the H2S Modeling Design Method program.
H2S Modeling Design Method information is not only valuable at design time but also at rehabilitation time. Annual maintenance budgets can be accurately predicted by effectively utilizing the H2S Modeling Design Method software on a periodic scheduled time frame.
Design professionals can now have accurate input into wastewater system maintenance costs. Graphic presentations can be presented to city officials to support budget requests and to illustrate the construction and rehabilitation needs of the city's wastewater system. As with any software of mathematical concept, H2S Modeling Design Method is only as good as the data input.
The accuracy of the data, and the skill and knowledge of the operator, are key factors in successful H2S modeling. Because the factors controlling sulfide generation in sewers are so complex, it would be unrealistic to expect that sulfide concentrations can be accurately predicted on an hour-by-hour basis. Even predictions of average sulfide conditions in a sewer are not considered precise, but they will be adequate for many design and operation purposes.
The Pomeroy equations that have been devised have coefficients that can be modified to meet the objectives of the engineer, giving results that will approximate average performance of all sewers represented by any given set of parameters or that will give results in varying degrees of conservatism. Thus, a sulfide prediction may show a concentration that will rarely be exceeded in any sewer, or one that will be exceeded only part of the time, or one that will be an average value where septic conditions prevail.
The level of understanding of sulfide generation mechanisms and corrosion of both cement bonded and ferrous materials allows a relatively accurate assessment of anticipated conditions in sewer systems and the cost-effective design of control measures. Structures, manholes, tanks and the treatment plants can benefit from the use of H2S Modeling Design Method evaluation.
This concept allows for the selecting of methods to minimize the corrosion of all concrete and metallic elements. By utilizing the H2S Modeling Design Method the following major factors can be addressed to minimize the formation and presence of sulfide in sewage systems. In addition numerous other methods are available to control the generation of sulfide in wastewater.
These methods affect the oxygen balance in sewage, oxidize generated sulfide, and react chemically with dissolved sulfide to form insoluble sulfide, or affect the sulfide generation capability of the sulfate or organic sulfur reducing organisms. The second step in reducing and eliminating MIC is to prevent the Thiobacillus from growing, thus cutting off the biogenetic formation of sulfuric acid. Traditionally, efforts to control corrosion of concrete sewers have focused on coating the concrete or using plastic liners, or chemical treatments to reduce the concentration of dissolved hydrogen sulfide gas carried by the wastewater.
Most of the treatments are costly and do not provide adequate, long-term protection or control. Acid can penetrate coatings though pinholes and react with the concrete; thus destroying the bond of the coating to the concrete . Thiobacillus are still present and able to produce sulfuric acid on the surface of the coating. By adding an antimicrobial agent to the coating some of this action can be abated.
Another concern about coatings is their adhesion to the concrete. Pull off testing of coatings has shown the failure zone within the concrete because the surface concrete pulls away with the coating.
By increasing the cohesion of the concrete, greater resistance to coating pull off would be achieved. It stands to reason that fibers in the concrete would improve the concrete's cohesion and thus the coatings adhesion.
For improved coating performance, the use of an antimicrobial agent in the coating and better adhesion through the use of fibers in the concrete is logical.
Another approach that has shown success in mitigating corrosion is mortar made from calcium aluminate cement and same source clinker. This material has shown a reduction affect on Thiobacillus growth and greater resistance to MIC although it is still subject to corrosion, albeit at a slower rate. These cements can be used in place of portland cement and do not produce calcium hydroxide, which is attacked by sulfuric acid.