【導(dǎo)讀】需要上都留下了很多值得關(guān)注的問(wèn)題。當(dāng)2021年10月8日發(fā)生在巴基斯坦北部的一個(gè)。且造成估計(jì)79000人的死亡。在巴基斯坦這種十分低質(zhì)量的混凝土施工技術(shù)是造成這次。極廣破壞的主要原因。其表應(yīng)潮濕，但不應(yīng)有集水，應(yīng)當(dāng)。它應(yīng)該分層澆筑以使每層可被均壓實(shí)。每層澆筑間隔的時(shí)間應(yīng)該限制在能夠。度不超過(guò)3或4ft，以防止混凝土離析。這種導(dǎo)管是由輕金屬制成的管子，具有可調(diào)節(jié)。凝土用于抵抗壓應(yīng)力。間要有足夠強(qiáng)的黏結(jié)力，以確保鋼筋和其周圍混凝土間不發(fā)生相對(duì)移動(dòng)。實(shí)驗(yàn)研究予以確定。ASTM中的A706的條款是專門(mén)使用于焊接的。ACI規(guī)范允許使用強(qiáng)度FY=80KSI的鋼筋。在這種情況下，ACI規(guī)范要求在規(guī)定的最小屈服強(qiáng)度時(shí)的總應(yīng)變不應(yīng)超過(guò)。們可以在根據(jù)上述的要求的情況下使用。在特殊情況下，例如高層建筑的下部樓層的柱

　　

【正文】 It is important to select repair materials that provide adequate durability. Materials used for the repair job should be at least as durable as the substrate concrete to which it is applied. of steel The mechanism of protection provided to the reinforcing depends on the type of repair materials used. For example, cementations materials can protect the steel from further corrosion by their inhibitive effect of increasing the alkalinity of the concrete, whereas epoxy resin mortars can give protection against the ingress of oxygen, moisture and other harmful agents. 中國(guó)地質(zhì)大學(xué)長(zhǎng)城學(xué)院 2021 屆畢業(yè)論文 12 with substrate The bond with the substrate must produce an integral repair to prevent entry of moisture and atmospheric gases at the interface. With most repair materials, the bond is greatly enhanced with the use of a suitable bonding aid such as an unfilled epoxy resin systems and slurry of Portland cement, plus any latex additives for a Portland cementbased repair system. Precautions should also be taken to remove all loose and friable materials from the surfaces to be bonded. Stability Shrinkage of materials during curing should be kept to a minimum. Subsequent dimensional change should be very close in the substrate inorder to prevent failure. Resistance to Environmentally Induced Damage Some initial exposure conditions may lead to premature damage lo repairs. For example, partially cured Portland cement repairs can deteriorate from hot weather preventing full hydration of the cement. To prevent this from happening extra protection during curing time may be necessary. of Application Materials should be easily mixed and applied so that they can be worked readily into small crevices and voids. Ideally, the material should not stick to tools, and should not shear while being trowel led nor slump after placement. The degree to which the repair material should match the existing concrete will depend on the use of the structure and the client39。 s requirements. A surface coating may be required when appearance is important or when cover to reinforcement is small. of Repair Methods A suitable repair counteracts all the deficiencies which are relevant to the use of the structure. The selection of tile correct method and material for a particular, application requires careful consideration, whether to meet special requirements for placing strength, durability or other shortor longterm properties. These considerations include: 1. Nature of the Distress 中國(guó)地質(zhì)大學(xué)長(zhǎng)城學(xué)院 2021 屆畢業(yè)論文 13 If alive crack is filled with a rigid material, then either the repair material will eventually fail or some new cracking will occur adjacent to the original crack. Repairs to live cracks must either use flexible materials to acmodate movements or else steps must be taken prior to the repair to eliminate the movement. 2. Position of the Crack Techniques which rely on gravity to introduce the material into the crack are more successfully carried out on horizontal surfaces but are rarely effective on vertical ones. 3. Environment If moisture, water or contaminants are found in the crack, then it is necessary to rectify the leaks Repair to slop leaks may be further plicated by the need to make the repairs while the structure is in service and the environment is damp. 4. Workmanship The skill the operatives available to carry put the repairs is another relevant factors. Sometimes this can mean the difference between a permanent repair and premature failure of the repair material. 5. Cost The cost of repair materials is usually small pared with the costs of providing access, preparation and actual labor. 6. Appearance The repair surface may be unsightly, particularly when it appears on a prominent part of the building. In this case, the repair system will include some form of treatment over the entire surface.