Determination of Transport Properties of Lightweight Aggregate Concrete for Service Life Modeling Tourney Consulting Group

Tourney Consulting Group has completed a study to determine the effects of Expanded Shale, Clay and Slate (ESCS) lightweight coarse and fine aggregates on the transport properties of concrete. The transport properties were then used in several service life prediction programs including STADIUM®, Life 365™ and in analysis performed in accordance with fib Bulletin 34.

Specified required design service lives of 75 years or more are becoming very common, especially with regard to major infrastructure projects. The Expanded Shale Clay and Slate Institute (ESCSI) commissioned the study to determine whether the use of ESCS lightweight aggregates can improve the transport properties of concrete and offer benefits in terms of increased service life.

This study involved modeling the performance of a bridge deck in the Detroit area, with the transport properties determined for use in Life 365™ or STADIUM®. The STADIUM® results showed that the time required for the onset of corrosion in the steel reinforcement will be increased by approximately 25% for concrete bridge decks containing lightweight coarse aggregates, compared to the control mixture containing only normal weight aggregates. The replacement of normal weight sand with lightweight sand resulted in approximately a 1.5 to 2 times increase in time to corrosion.

The Life 365™ analysis showed similar performance improvements to the STADIUM® results, with up to a 3 times improvement when LW sand replaces NW sand.

An internal curing mix in which a small percentage of NW sand was replaced with LW sand resulted in an increased time to restrained shrinkage cracking, higher strength, and a longer service life than the control concrete.

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Key Findings

  • The STADIUM® results showed that using ESCS lightweight aggregate will increase the service life compared to the normal weight control mixture as follows:

    o For lightweight coarse aggregate mixtures, by approximately 25%.

    o For replacement of normal weight sand with lightweight sand, approximately 1.5 to two times.

  • Life 365™ analysis showed similar results for LW coarse aggregate mixtures, but approximately a two to three times increase in service life for lightweight sand replacing the normal weight sand.
  • The replacement of a small quantity of NW sand with LW fines for internal curing was shown to reduce restrained shrinkage cracking and to increase compressive strength and service life. These results coupled to the results with the replacement of all the fine aggregate with LW fines indicate that increasing the percentage of LW fines replacement of NW fines beyond that needed for internal curing could increase the service life of the concrete by a factor of up to 1.5 to 3 for total replacement.

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