Use of wet cellulose to cure shotcrete repairs on bridge soffits. Part 2: Laboratory testing and analysis.

This paper reports results of an experimental program conducted to investigate the quality of shotcrete cured by wet, sprayed-on cellulose fibers. The program also investigated the quality of shotcrete containing accelerator. Both field and laboratory samples were prepared and cured using air-curing, curing compound, misting and curing compound, or cellulose. At the end of the curing period, cores were collected from the test panels and tested. The results showed that the effects of curing are noticeable mainly at the top 15 mm of the shotcrete surface. Within this part of the shotcrete, cellulose-cured panels showed an enhanced pore structure compared to samples cured using traditional curing methods, as reflected by mercury intrusion porosimetry and sorptivity test results. The quality of the surface of cellulose-cured shotcrete was significantly enhanced when the additives added to commercially available cellulose to improve its fire resistance were eliminated. Adhesive added to improve bonding of cellulose fibers to the shotcrete surface did not have a negative effect on the surface of the shotcrete. Laboratory-prepared samples showed evidence that cellulose curing reduces shrinkage cracking. The use of accelerator was found to adversely affect the strength and durability of the shotcrete. [ABSTRACT FROM AUTHOR]