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Of all the ASTM-related technical questions received here at the National Precast Concrete Association, C478, “Standard Specification for Precast Concrete Manhole Sections,” stands out as one of the most popular. Many NPCA members produce precast concrete manholes, as these products are used for so many underground applications such as storm and sanitary sewer access, lift stations and utilities.
The ASTM C478 standard contains the requirements for the manufacture and purchase requirements of products used for the assembly and construction of circular, vertical precast concrete manholes and structures. The scope of C478 includes structures used in precast sewer, drainage and water works. ASTM C478 is an important standard under the jurisdiction of ASTM C13, the technical committee on concrete pipe, established in 1931.
A bit of history
Committee C13 has been around a long time. The concrete pipe industry actually dates back to the late 1800s, as cited in the “Concrete Pipe Handbook” published by the American Concrete Pipe Association: “The history of concrete pipe standards began virtually with the founding of ASTM in 1898. By 1904, eight technical committees had been organized, and in 1904 six more were formed. One of these, Committee C-4 on Clay and Cement-Concrete Sewer Pipe, was the forerunner of Committee C13.”
The committee meets once a year, with approximately 100 members attending over three days of technical meetings. With a membership of approximately 200, C13 currently has jurisdiction over 55 standards published in the Annual Book of ASTM Standards. C13 has nine technical subcommittees that maintain jurisdiction over these standards.
C13’s subcommittee structure and its portfolio of approved standards and work items under construction are listed in the sidebar “Resources & References” on page 10. These standards play a pre-eminent role in all aspects important to the effective standardization of concrete pipe, including material specifications, test methods and installation practices.
The specific scope of C13 is the formulation and review of specifications, methods of test and definitions for concrete pipe, concrete box sections and concrete manhole sections used for constructing sewers, culverts, and for factory-made compression and self-energizing joints. Development and review of practices and guides cover design, installation, testing, economic evaluation and performance of concrete pipe systems.
ASTM C478 and joint materials
C478 opened up new manufacturing standards for joint materials as gasket material technology evolved. In addition to the O-ring gasket cross section, the profile-wall gasket cross section was developed (see ASTM C443 listed below). The following specifications apply to manhole connectors and joints:
• C923, “Standard Specification for Resilient Connectors Between Reinforced Concrete Manhole Structures, Pipes, and Laterals”
• C443, “Standard Specification for Joints for Concrete Pipe and Manholes, Using Rubber Gaskets”
• C990, “Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants” (Butyl rubber gaskets are commonly used in the industry)
To improve the testing of manhole section gaskets, the discussions in C478 led to the profile wall gasket, a connection with no notch that can be reset in the manhole. It is more forgiving than other gaskets and is becoming more the norm.
While the precast manhole is usually able to withstand additional pressure than that prescribed by ASTM 1244, the gaskets are manufactured to withstand a minimum of only 13 psi according to ASTM C443. Under the jurisdiction of Subcommittee C13.06, C923 specifies the assembly to be subjected to hydrostatic pressure of 13 psi for 10 minutes.
Understanding and supporting ASTM standards
The emergence of the 1972 Clean Water Act established the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. Ensuring the separation of human waste from clean drinking water relies on the durability and reliability of underground piping systems. Compliance with ASTM standards protects the integrity of precast concrete pipe systems and the consumer.
Beyond the critical importance of protecting human health and preventing contagious disease, properly designed and produced manholes ensure the safety of workers who handle precast products, and in the long run guarantee quality precast products that comply with accepted industry practices and prevent unnecessary increases in cost to the consumer.
Precast specifying engineers and precast producers need to be up to date on ASTM standards, because construction material technology, manufacturing and installation practices, testing techniques, and state and federal regulations are continuously evolving. ASTM is at the cutting edge of all of these changes; the balance of the members of its technical committees represents the best practitioners in their respective fields.
As a specific example, consider the skyrocketing cost of steel as it relates to precast concrete reinforcement. The changes made to hoop steel specifications means less steel. Overdesigning reinforcement translates into an unnecessary increase in manhole manufacturing costs, which in turn results in increased costs to consumers. ASTM C478 specifications are minimum requirements for manholes, and engineers can specify additional reinforcement to resist point loading.
“Engineers and producers are well-advised to be familiar with the latest precast manhole specifications for three reasons,” said Frederick Cash Sr., a consulting engineer and chairman of ASTM C478. “ASTM standards address the latest technologies in the marketplace; ASTM committees are made up of a balanced membership that includes input from producers, regulators, engineers and consumers – this balanced input produces a good standard; and finally, compliance with current ASTM standards produces the best product for its purpose and best serves the manufacturer and the public.”
Without a good understanding of the current ASTM standards and the best information available from the contributions of the diverse committee member (producers, suppliers, engineers, federal regulators and consumers), the use of old documents (C478-72) instead of the current C478-09 specification does not serve the product’s purpose and is neither in the best interests of the manufacturer nor the consumer.