Immediately after finishing, shotcrete in tunnel areas shall be kept continuously moist for at least 3 days. In non tunnel application shotcrete shall be cured using any method as described below. One of the following materials or methods shall be used:
Ponding or continuous sprinkling.
Absorptive mat or fabric, sand, or other covering kept continuously wet.
Curing compound. A coverage application requirement of 2.5 square meters per liter (100 square feet per gallon) or twice the manufacturer’s requirement, whichever is less. Curing compound shall not be used on any surface against which additional shotcrete or other cementitious finishing materials are to be bonded unless positive measure, such as sand blasting, are taken to completely remove curing compound prior to the application of such additional materials.
Final curing
Additional curing shall be provided immediately following the initial curing and before the shotcrete has dried. One of the following materials or methods shall be used:
Continue the method used in initial curing
Application of impervious sheet material that conforms to ASTM C171
Formed Surface
If form are to be removed during curing period, one of the curing materials or metheds listed in paragraph initial curing shall be used immediately. Such curing shall be continued for the remainder of the curing period.
Duration of curing
Curing shall be continued for the first 7 days after shotcreting or untill the specified compressive strength of the in-place shotcrete as determined by specimens obtained and tested in accordance with ASTM C42 is achieved.
Waver and/or modification of curing requirements
Within the interior of a tunnel, curing procedures and requirements may be waved or modified if the tunnel interior environment induces a moist curing condition. The contractor shall be responsible for evaluating conditions and proposing any modifications or waver for the consideration of the engineer. Approval of curing modifications and/or waver of curing requirements be the engineer, shall not relieve the contractor or his responsibility for the proper curing of shotcrete.
No comments:
Post a Comment