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预应力砼大型屋面板(代号 YDB)自问世以来发展很快,已广泛应用于工业建筑。砼制品厂一般采用长线台座法或短线钢模法,并采取自然养护及蒸汽养护的方式生产预应力砼大型屋面板。但生产中由于施工不当,常产生板面印筋微裂缝、板端围绕预应力主筋的“星状”裂缝和板主肋二侧的“八字”裂缝(图1)等。这里根据对构件厂的质量检查情况,对裂缝的产生原因和处理方法作以下介绍,以供借鉴。1.板面印筋干缩裂缝砂石含泥量偏高,或称量控制不严导致砂石级配波动较大,水灰比过大,水泥用量超定额,以及养护不及时,造成砼干缩值增大,使得沿板面分布筋部位应力集中,则板
The prestressed concrete large roof (codenamed YDB) has developed rapidly since its inception and has been widely used in industrial buildings. Tantalum Products Factory generally adopts long-term pedestal method or short-term steel mold method, and adopts natural maintenance and steam curing methods to produce prestressed concrete large-scale roof panels. However, due to improper construction in the production, there are often micro cracks on the surface of the board, “star” cracks around the prestressed main tendon at the plate end, and “character” cracks on both sides of the main rib (Figure 1). Based on the quality inspection of the component factory, the following describes the causes and treatment methods of cracks for reference. 1. The board surface crevices shrink shrinkage cracks gravel with high mud content, or lax control leads to sand and stone gradation fluctuations, water-cement ratio is too large, cement dosage is over-quota, and maintenance is not timely, resulting in The shrinkage value increases, so that the stress concentration is distributed along the surface of the plate.