Page 150 - Water Standards
P. 150

narrow topography.
                             4) Crane swinging concrete tanks should be employed for
                                gravity dams, and capacious sluices and dams in river
                                channels.
                       3   3   6  Concrete temperature controlling measures shall meet the fol⁃
                       lowing requirements:
                           1  In the cold season, the requirements of Article 2   7   23 in
                       this specification shall be complied with. In hot seasons, the require⁃
                       ments of Article 2   7   24 in this specification shall be complied with,
                       as well as that in this section.
                           2  In order to avoid cracking, comprehensive measures shall be
                       employed regarding structure design, temperature control, rough ma⁃
                       terials selection, construction plan and construction quality, etc.
                       Strict temperature control during construction shall be regarded as the
                       major measure to avoid concrete cracking. Both pouring temperature
                       and maximum temperature rise of concrete shall meet design require⁃
                       ments. Otherwise the concrete should not be poured.
                           3  The construction technology of concrete shall be modified to
                       improve concrete quality. The concrete shall meet the requirements for
                       strength guarantee rate, avoid overly surpassing design strength, and
                       meet the requirements for the construction quality homogeneity
                       indices. The homogeneity index is expressed as S , the value of the
                                                                fcu
                       standard deviation of the site specimen compressive strength after
                       curing 28 days. The value should be less than 0   18, and the calcula⁃
                       tion method is listed in Annex J. When the mix proportion of the con⁃
                       crete is selected, bleeding problems shall be solved properly, and
                       during construction, bleeding on bin surfaces shall be strictly con⁃
                       trolled. During construction crack treatment, all emulsion skin, oil
                       stains, poorly combined aggregates, and weak layers caused by
                       bleeding on bin surfaces shall be cleared away.
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