Last edited 21 Feb 2021

Mass concrete

Hoover dam.jpg

[edit] Introduction

The generally accepted and widely-used definition of ‘mass concrete’ is that provided by the American Concrete Institute (ACI). It defines mass concrete as:

“…any volume of structural concrete in which a combination of dimensions of the member being cast, the boundary conditions, the characteristics of the concrete mixture, and the ambient conditions [which] can lead to undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in the long-term strength as a result of elevated concrete temperature due to heat of hydration.”

The emphasis on thermal behaviour – which can cause a loss of structural integrity and monolithic action – is the only characteristic that distinguishes mass concrete from other concrete work.

Mass concrete is usually associated with large, poured in-situ concrete structures such as dams, bridge piers, foundations to very tall buildings and other large volume placements which are at least 1m-deep. In many cases, mass concrete is unreinforced and therefore strong in compression but weak in tension.

[edit] Hoover Dam

Construction of the Hoover Dam (pictured) on the Colorado River, USA, began in 1931, required enormous quantities of mass concrete (3.3 million cubic metres) to construct its arch-gravity structure. It is 13.7m wide at the top and 201m-wide at the bottom. To dissipate the heat generated by the cooling (setting) of the mass concrete required a vast network of water circulating through steel pipes. Without this, the concrete would still be setting today.

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