01365899

Component

Due to some remotely located projects and successes with admixtures, industry requested the State Department of Transportation (Mn/DOT) to allow longer delivery times. In response to this request, 90 and 120 minute allowable delivery times were proposed as alternatives to the current 60 minutes specification for air entrained concrete to allow for more feasible construction. To investigate the impact this change would have on concrete performance, a laboratory study, controlled plant study, and a field study were conducted. These studies all evaluated critical properties of concrete (slump, plastic and hardened air, freeze thaw durability, and compressive strength) for a variety of mix designs at different times after mixing. Many different combinations of air entrainers, water reducers, retarders and cementitious materials were used in the mix designs. Analysis of the data from the laboratory study, controlled plant study, and field study led to mixed theories on how these properties of concrete are influenced by extended delivery times of 90 and 120 minutes. Because in many cases the analysis showed that slump and plastic air content can be significantly affected by a change in delivery time, it would be beneficial to conduct further research on this topic before any changes were made to current specifications for allowable delivery time of concrete.

This paper was sponsored by TRB committee AFN20 Properties of Concrete

01362476

12-1789

English

18p

2012

Transportation Research Board 91st Annual Meeting

Digital/other

Figures; References; Tables

Admixtures; Air entrained concrete; Concrete hardening; Concrete industry; Construction projects; Delivery service; Properties of materials; Setting (Concrete); Specifications; Time

Minnesota Department of Transportation

Construction; Highways; Materials; Pavements; I32: Concrete; I50: Construction and Supervision of Construction

Transportation Research Board Annual Meeting 2012 Paper #12-1789

PRP, TRIS, TRB

Feb 8 2012 5:05PM