中高等强度混凝土预应力转换梁开裂分析

从混凝土裂缝产生机理入手,结合分析某大型商住两用框架结构的转换梁开裂分析的工程实例,介绍了混凝土裂缝类型、特征、以及引起开裂的主要原因。探讨在中高等强度的混凝土结构工程的施工中,如何根据裂缝的性状,正确分析与判别裂缝类型,并采取合理的技术措施,防止裂缝对工程结构的安全性和耐久性造成不利影响。

建筑垃圾人工砂配制混凝土试验研究

研究了邯郸地区用砖混结构建筑垃圾生成的建筑垃圾人工砂的粒径、堆积密度、吸水率、压碎值指标等基本物理性能,分别以0、50%、100%的建筑垃圾人工砂等量取代天然细骨料配制不同强度等级混凝土,检验混凝土拌合物的性能、力学性能及耐久性能,探讨了建筑垃圾人工砂不同取代率对混凝土性能的影响。试验结果表明,建筑垃圾人工砂完全代替天然砂用于C60及以下强度等级的混凝土中是可行的,随着取代率的提高,混凝土强度有所降低;混凝土强度越高,降低幅度越大。

Flexural response of reinforced concrete beams strengthened with post-poured ultra high toughness cementitious composites layer

Four-point bending tests were conducted up to failure on eleven reinforced concrete (RC) beams and strengthening beams to study the effectiveness of externally pouring ultra high toughness cementitious composites (UHTCC) on improving the flexural behavior of existing RC beams.The strengthening materials included UHTCC and high strength grade concrete.The parameters,such as thickness and length of strengthening layer and reinforcement in post-poured layer,were analyzed.The flexural behavior,failure mode and crack propagation of composite beams were investigated.The test results show that the strengthening layer improves the cracking and ultimate load by increasing the cross section area.Introducing UHTCC material into strengthening not only improves the bearing capacity of the original specimens,but also disperses larger cracks in upper concrete into multiple tightly-spaced fine cracks,thus prolonging the appearance of harm surface cracks and increasing the durability of existing structures.Compared with post-poured concrete,UHTCC is more suitable for working together with reinforcement.The load?deflection plots obtained from three-dimensional finite-element model (FEM) analyses are compared with those obtained from the experimental results,and show close correlation.

机制砂和聚羧酸减水剂在普通混凝土中的应用

结合生产实际,本文介绍了用机制砂代替河砂,聚羧酸减水剂代替脂肪类减水剂配制普通混凝土具体做法及实用效果。以及采用机制砂、聚羧酸减水剂所产生的经济和社会效益。