负弯矩钢筋混凝土保护层厚度施工控制技术的探析.docx

负弯矩钢筋混凝土保护层厚度施工控制技术的探析
摘　要：在钢筋混凝土施工中，钢筋保护层厚度控制常常被忽略。本文重点叙述了钢筋保护层在钢筋混凝土结构中的作用和不同构件的具体施工控制措施，并根据施工经验提出了一些建议，供同行参考。
Pick to: during the construction of reinforced concrete, the reinforcement protection layer thickness control is often ignored. This paper describes the role of reinforced protective layer in reinforced concrete structures and construction control measures of different components, and puts forward some Suggestions according to the construction experience, for peer reference.
关键词：钢筋保护层；控制；垫块
Key words: reinforced protection layer; Control; block
一 钢筋保护层的作用　　
A reinforced protection layer
一般来说，保护层厚度的规定是为了满足结构构件的耐久性要求和对受力钢筋有效锚固的要求。保护层厚度与钢筋直径、构件种类、环境条件和砼强度等级等因素有关。从微观构造进行分析，砼存在有大量的微观裂缝孔隙及毛细孔，这些微观裂缝的存在，会造成水和侵蚀性介质的渗入，从而造成对钢筋的损害。　　
In general, protective layer thickness of the regulation is in order to meet the requirements of the durability of structures and effective reinforced anchorage requirements. Protective layer thickness and the steel bar diameter, component types, environmental conditions and concrete strength grade and other factors. From microscopic structure analysis, concrete microscopic fracture pore and wool stoma, there are a lot of these micro cracks exist, can create the infiltration of water and corrosive medium, resulting in damage to the steel.
在砼强度等级、密度一致的情况下，保护层越厚，钢筋受腐蚀的程度和可能性就越低。因此，规范对处于恶劣条件环境(室外、高湿度、或考虑冻融和腐蚀环境)下的构件，在砼强度等级相同的情况下，其保护层厚度相应加厚。具有一定的保护层厚度，也是保证砼对受力钢筋正常的握裹力和有效锚固，使得钢筋与砼能有效传力和共同作用。但是，保护层过厚，会减少构件截面有效高度，导致其承载力下降，构件变形过大和开裂，造成一定的结构安全隐患。保护层过小，将会加速钢筋的锈蚀，影响结构的耐久性和正常工作。因此，保护层厚度应在规范规定的偏差范围之内。
Under the condition of the concrete strength grade and density is consistent, the protective layer is thicker, the degree of reinforcement corrosion and the less likely. Therefore, the specification is in bad condition of environment (outdoor, high humidity, or consider freezing and thawing and corrosion environment) under the artifacts, in under the same strength grade of concrete, the thickness of protective layer thickening accordingly. Has certain protective layer thickness, but also to ensure concrete reinforced grip of normal and effective anchorage, steel rebar and concrete makes the effective force transmission and work together. Protective layer too thick, however, will reduce the components section effective height, resulting in a decline in its bearing capacity and deformation of components is too large and cracking, and structure as a potential safety hazard. Protective layer is too small, will accelerate reinforcement corrosion, effect on the durability of the structure and work properly. Therefore, the protective layer thickness should be within the deviation range stipulated by the specification.
二 施工控制措施　　
Two construction control measures
目前在施工现场大量使用的控制保护层的是砂浆垫块。砂浆垫块应根据不同使用部位、按不同厚度使用高标号水泥分别预制，垫块上面预锚铅丝，以方便固定，其强度不得小于结构构件混凝土的设计要求。强度过低则易被钢筋压碎，且削弱构件强度。下面结合施工经验分别对板、基础、梁、柱构件的保护层控制分别进行阐述。
In the construction site at present extensive use of control layer is mortar pad. Mortar pad should be used according to different parts and use high quality cement prefabricated respectively according to the different thickness, block the prestressing anchor galvanized iron wire, fixed with convenient, its strength should not be less than the design requirements of concrete structures. Is easy to broken in reinforcement strength is too low, and weaken the strength of components. Combined with construction experience of plate respectively, foundation, under the beam, column layer control respectively.
板构件保护层厚度控制　　
Board member protective layer thickness control
板构件中，施工中经常出现的问题是负弯矩筋大量被踩踏，造成负筋下沉，保护层加大减少了截面有效高度。控制应从以下方面进行：
Board member, often encountered in the construction of the problem is a massive amount of negative moment reinforcement stampede, resulting in negative reinforcement, protective layer increase effectively reduces the section level. Control from the following aspects:
(1)采取措施避免对钢筋的踩踏。可在浇筋砼时搭设通道，施工人员返往及材料运输通过通道进行。同时，尽量采用先进的施工技术和设备，如采用泵送砼或塔吊进行砼运输，以减少在砼浇筑时，过于频繁的材料运输和人员往返时对钢筋的踩踏
(1) take measures to prevent the steel bar in the stampede. Available in pouring reinforced concrete channel shall be built, workers to return to and materials transportation through the channel. At the same time, as far as possible the adoption of advanced construction technology and equipment, such as using to transport concrete pumping concrete or tower crane, in order to reduce the concrete casting, too often the material transport and a basis for reinforcement of trampling
(2)加强负弯矩筋的抗踩踏力。对负弯矩筋加设钢筋凳，钢筋凳宜用直径大于14mm的钢筋制作，且间距不应过大，一般应为600mm 左右，呈梅花形布局。
(2) strengthen the trampling resistance of negative moment reinforcement. Of negative moment reinforcement adding reinforced bar stool, appropriate is used is greater than 14 mm diameter steel production, and the distance should not be too big, should be 600 mm or so commonly, the plum flower form layout.
(3)浇筑砼时，必须配备钢筋工，对被踩踏下沉的钢筋及时调整复位。
(3) pouring concrete, it must be equipped with steel workers, on the sink of the trampled steel adjust reset.
2. 基础的钢筋保护层的控制　　
2. The foundation of reinforced protective layer control
基础因为大多埋深在地下，地下环境较复杂，或有地下水，环境潮湿，有机物较多，化学腐蚀的可能性大大增加。因此基础的钢筋保护层的厚度设置在设计规范上规定是最大的，为35mm-50mm。在条基或满堂基础、独立基础施工时，底面钢筋保护层必须设置在受力主筋的下面，用扎丝绑扎固定好，侧边及上边受负弯矩钢筋则用钢筋垫铁支起，防止被人或混凝土压下。在桩基础施工时，因桩基埋深较大，多处于地下水或泥浆中，因此保护层垫块做成圆形，中间留一圆孔，将钢筋从圆孔穿过。这样一来，不仅在将钢筋笼放入桩孔时减少摩擦，有利于放置钢筋笼，更有利于保证钢筋笼位于桩孔中央，从而使保护层的厚度准确，不会出现偏差。
Basis because mostly buried deep in the ground, underground environment is complex, and groundwater environment moisture, organic matter more, is the possibility of chemical corrosion increase greatly. Therefore foundation reinforced protection layer thickness of the Settings on the design code provisions is one of the biggest, 35 mm to 50 mm. Article in the base or fertility in construction of foundation, independent foundation, base reinforced protection layer must be set in the design on the bar below, with Mr. Silk tie fixed well, the side and top under negative moment reinforcement with steel shim pitched, prevent or concrete under pressure. In pile foundation construction, due to the embedded depth of the pile is bigger, more is in ground water or mud, so protective layer block into a circle, leaving a round hole, will be reinforced through the round hole. As a result, not only reduce friction when the reinforcing cage in the pile hole, is advantageous to the placement of reinforcing cage, is more advantageous to guarantee the reinforcing cage is located in the central pile hole, so that the protective layer thickness accurate, won't appear deviation.
3. 梁、柱钢筋保护层的控制措施　　对梁、柱钢筋保护层厚度控制，一般采用的是绑扎砂浆垫块的方法。这种方法有以下缺点：
3. The control measures of beams and columns reinforced protective layer of beams and columns reinforced protection layer thickness control, generally adopt the method of binding mortar pad is. This method has the following disadvantages:
垫块为纯砂浆块，强度低，易破碎；
Block for pure cement mortar, low intensity, easy and broken;
垫块为绑扎固定，固定不易牢固，易脱落。以上两方面造成钢筋位置不准确，保护层偏差较大。可采用定制的高强塑料垫块进行钢筋保护层厚度的控制，该垫块可按保护层厚度和钢筋直径分为不同规格，适用于各种构件的不同配筋情况。这种垫块的安装方法是将垫块利用塑料本身的弹性直接卡在钢筋上，既施工简便， 安装又牢固，能准确地控制保护层厚度，效果较好 高强塑料垫块示意图三 建议 1．一般混凝土构件混凝土保护层的建议　　
Block is bound and fixed, fixed firmly not easily, easy to fall off. Above two aspects cause reinforced position is not accurate, the protective layer. The deflection Can use custom high strength plastic reinforced protection layer thickness control block, the block can be in accordance with the protective layer thickness and the steel bar diameter is divided into different specifications, applicable to a variety of different component parts of the reinforcement. Installation method of this block is to block using plastic and elastic card on the reinforcing steel bar directly, both the construction is simple, installation and strong, can accurately control the thickness of protective layer, the effect is good, high strength plastic block diagram 3 suggestion 1. General concrete member concrete cover
根据混凝土保护层的特性，混凝土构件(特别是二、三类环境中的构件) 应尽量避免使用清水混凝土，而应在表面采取诸如水泥砂浆抹面之类的保护措施。因为，相对于混凝土来说，水泥砂浆抹面的密实度更好，能更好的防止大气中的CO2及其他腐蚀性气体的渗入，从而能更好的确保结构的耐久性。 2．露天悬臂板保护层的建议　　由于露天悬臂板所处的特殊环境，其上表面开裂后更容易造成钢筋的锈蚀，因此，《混凝土结构设计规范》规定，对于处于二、三类环境中的悬臂板，其上表面应采取有效的保护措施，以保证构件的耐久性。而在平时的工程实践中，这个问题并未得到足够的重视，使悬臂板钢筋过早锈蚀，从而影响结构安全。
According to the properties of the concrete cover, concrete member (especially the artifacts in the two, three types of environment) should be as far as possible avoid the use of concrete, and should be on the surface to take protective measures, such as cement mortar plaster. Because, relative to the concrete, cement mortar coating compactness is better, can better prevent the atmospheric CO2 and other corrosive gas infiltration, thus better able to ensure that the durability of the structure. 2. Outdoor cantilever plate cover suggestion due to outdoor cantilever plate special environment, and on its surface after cracking are more likely to cause steel corrosion, therefore, the "concrete structure design code" regulation, for a cantilever plate in two, three types of environments, and its effective protection measures should be taken on the surface, to ensure the durability of the components. And in the usual engineering practice, this problem has not been enough attention, make premature cantilever plate reinforcing steel corrosion, so as to affect the structure safety.