Code Update: ASTM Introduces Two New Standards for Precast Concrete

ASTM committees have been hard at work providing new standards and improving existing standards for precast concrete products that are in high demand in the industry. Committee C13 on Concrete Pipe recently released a new standard for precast reinforced concrete end sections, and Committee C27 on Precast Concrete Products recently made significant improvements to its standard for precast concrete septic tanks. Each of these standards serve to improve product quality and consumer confidence as well as strengthen the transportation infrastructure and onsite wastewater markets.

ASTM C1932: Standard Specification for Manufacture of Reinforced Precast Concrete End Sections for Pipe

ASTM recently published a new standard specification for the manufacturing of reinforced precast concrete end sections for pipe culverts. These would include sloped end sections, safety end treatments, flared end sections, parallel wall sections, precast end walls and precast headwalls for various culvert pipe shapes.

Although precast concrete end sections have been in the marketplace for years, the responsibility to provide specifications for these products has been with project owners, who have either written their own specifications or have had to find a place for these precast concrete structures in their project specifications. This new ASTM standard specification allows project owners to now specify conformance ASTM C1932 in lieu of providing their own specifications for precast end sections. This new standard includes minimum requirements for their performance, design methods, concrete materials used in manufacture, joints and connections, concrete reinforcement, and physical requirements for strength and durability as well as minimum acceptance criteria.

This new standard will benefit project owners and manufacturers of these products. Project owners who want assurance that the products they need for their projects have been designed and manufactured in accordance with the best industry standards will no longer be forced to write their own specifications but may now specify conformance to this new ASTM standard. Product manufacturers will have a uniform standard set of criteria to reference when producing these products, removing any guesswork. One additional benefit is that having a national standard for these products sets the bar for similar products being specified throughout the industry.

ASTM C1227: Standard Specification for Precast Concrete Septic Tanks

The ASTM committee Precast Concrete Products recently made several substantive changes to the materials, design and testing sections of ASTM standard C1227 on precast concrete septic tanks.

To keep up with recent and ongoing changes in the cement industry, provisions for expanding the use of different types of ASTM C595 cements as well as a new provision allowing the use of ASTM C1157 blended cements have been added to the materials section. The inclusion of these new types of cements will help keep ASTM C1227 products on the forefront of concrete and cement technology as they continue to evolve, allowing manufacturers to provide septic tanks that are even more environmentally friendly than before.

Moving on to design requirements, previous provisions for the use of allowable stress design or working stress theory for design have been removed since most—if not all—of the current concrete building codes have eliminated any reference to those design methods in favor of using ultimate strength theory, often referred to as Load Factor Design (LFD) or Load and Resistance Factor Design (LRFD). A provision for design based on actual demonstrated performance is still included in case designers or users would prefer to use other types of design methods. A helpful diagram also has been added to the design section to provide a visual representation of various design requirements, such as minimum and maximum liquid depth relative to total tank depth, and how these and other physical requirements are intended to work together.

Perhaps the most significant changes were made to the performance testing requirements for both the vacuum test and hydrostatic test. Requirements for the vacuum test are the same as before, but much clarifying information has been added for users. As before, a successful vacuum test is one in which a negative pressure of 4 inches of mercury is held for five minutes without any measurable loss in the reading.

For the hydrostatic test, the minimum standing time for the water level has been significantly reduced, instead allowing a visual check that the tank is holding the static water level steady before timing the test at least one hour, the same time period as before. By removing the minimum soak time, the overall test time may be greatly reduced. If the water level is observed to be steadily decreasing, bringing the water level back to its intended test level before starting the timer is allowed to account for any absorption in the concrete. The one-hour minimum test time must be met in any case. Clarifying information has been added to this section as well, instructing users not to overfill the tank before testing, as this could lead to false negatives and produce excessive load stresses in the concrete.

 

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