Precast Inc. - May/June 2008 - (Page 33) THE MANUFACTURER SUPPLIED THE HIGH-PERFORMANCE PRECAST CONCRETE FOR THE I-10 BRIDGE PROJECT AND CHOSE AN ULTRAFINE FLY ASH DUE TO ITS EASE OF HANDLING AND COST SAVINGS. applications such as bridge decks, overlays, parking garages and pavements. When looking for a longer-lasting structure in a marine or aggressive environment, low permeable concrete is important. If the concrete has a crack, the effective cover over the reinforcing steel is reduced to the distance from the bottom of the crack to the reinforcing steel. A recent study by the University of South Alabama (“Influence of Ultrafine Fly Ash on the Early Age Response and the Shrinkage Cracking Potential of Concrete,” Journal of Materials in Civil Engineering 2005, Vol. 17, No. 1, pages 45-53) indicated that the propensity of autogenous and plastic shrinkage cracking is reduced when ultrafine fly ash is used. When putting together a concrete mix with ultrafine fly ash, it is not necessary to preload the ultrafine fly ash into the mixer. This material does not require any additional or special mixing procedures to ensure that the concrete is homogenous throughout the concrete mix. Ultrafine fly ash can be added AN ULTRAFINE FLY ASH HAS A TOP SIZE OF 10 MICRONS AND AN AVERAGE PARTICLE SIZE OF 2 TO 4 MICRONS. THE FINER SIZE PROVIDES THE REACTIVE SURFACE AREA THAT GENERATES HIGHER EARLY STRENGTHS AND LOWER PERMEABILITIES IN THE CONCRETE MIX. MAY/JUNE 2008 | WWW.PRECAST.ORG 33 http://www.precast.org
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