【導(dǎo)讀】在過去的50年里，建筑物發(fā)生火災(zāi)的數(shù)量增加了一倍。確保結(jié)構(gòu)在被火災(zāi)。損壞后安全并使之能夠有計劃地適當?shù)谋痪S修的評估就顯得前所未有的重要。巖相學(xué)能夠使人們獲得在建筑維修和增加安全保證直接。提高節(jié)約成本的受損材料的精確的探測。廣泛、真實的火災(zāi)損傷調(diào)研相結(jié)合，也被作者承擔了下來。在英國，火災(zāi)的損失目前超過了每天兩萬英鎊。后續(xù)損失中提供相當多的結(jié)余。巖相學(xué)的檢驗已被廣泛地應(yīng)用于確定鋼筋混凝土構(gòu)件的火災(zāi)影響深度。美國阿林頓的五角大樓，一架被劫持的飛機在2021年9月11日撞向了它。應(yīng)地，白宮在2021年作出了將受損部分進行拆除并重建的決定。樣品的巖相檢測可用于視維修所需要的程度來作出明智的決策。隨后在一個單獨的部分中，將會對一項考古學(xué)調(diào)查所做的。中對鉆孔的鉆石核心樣品進行的巖相檢測就可取得的一般成績。薄切片的檢驗借助于倍率一般高達×600的高倍巖相學(xué)顯微鏡。然而，由于其有限的可能性和相對較高的費用，

　　

【正文】 e is deemed to have been significantly damaged. Normally concrete exposed to temperatures above 300186。C is replaced if possible. Otherwise the dimensions are increased (for example, by reinforced columns), depending upon the design loads. Visually apparent damage induced by heating include spalling, cracking, surface crazing, deflection, colour changes and smoke damage. Visual survey of reinforced concrete structure is performed using a classification scheme from Concrete Society Technical Report No. 33 (1990). This system uses visual indications of the degree of damage to assign each structural member a class of damage from 1 to 5. Each damage classification number has a corresponding category of repair, ranging from decoration to major Concrete Society classification system is summarised in Table 1. Spalling of the surface layers is a mon effect of fires and may be grouped into two spalling is eratic and generally occurs in the first thirty minutes of the fire. A slower spalling (refered to as 39。sloughing off39。) occurs as cracks form parallel to the fireaffected surfaces leading to a gradual separation of concrete layers and detachment of a section of concrete along some plane of weakness, such as a layer of reinforcement. A prehensive study of spalling of concrete in fires is given in CIRIA Report 118 (Malhotra,1984). Forms of cracking include those caused by differential thermal exansion that often run perpendcular to the outer surface. Also, differential inpatability between aggregates and cement paste may cause surface crazing. Thermal shock caused by rapid cooling from firefighting water may also cause cracking. The colour of concrete can change as a result of heating (Bessey, 1950) and may be used to indicate the maximum temperature attained and the equivalent fire duration. In many cases, at above 300186。C a red discoloration is important as it coincides approximately with the onset of significant strength loss. Any pink/red discolored concrete should be regarded as being suspect (Concrete Society, 1990). Actual concrete colours observed depend on the types of aggregate present in the concrete. Colour changes are most pronounced for siliceous aggregates and less so for limestone, granite and Lytag (shows very little colour change). The most striking colours are produced by flint (chert) and Figure 1 illustrates the colour changes of flint aggregate concrete. The red colour change is a function of (oxidizable) iron content and it should be noted that as iron content varies, not all aggregates undergo colour changes on heating. Also, due consideration must always given to the possibility that the pink/red colour may be a natural feature of the aggregate rather than heatinduced. Some widely used aggregate materials contain naturally red or pink particles. British examples include Ordovician and Permotriassic sandstones and quartzites, which are often various shades of red and any sand/gravel deposits that include materials derived from these rocks (for example, Trent river gravels). In addition, the Thames river gravels may occassionally include naturally red coloured flints. Care must also be taken when white calcined flints are present as these are monly incorporated in decorative white concrete panels and are also a mon ingredient of calcium silicate bricks. Petrographic examination is invaluable in determining the heating history of concrete as it can determine whether features observed visually are actually caused by heat rather than some other cause. In addition to colour changes of aggregate, the heating temperature can be crosschecked with changes in the cement matrix and evidence of physical distress such as cracking and microcracking. A pilation of the changes undergone by concrete as it is heated is presented in Table 2. Careful identification of microscopically observed features allows thermal contours (isograds) to be plotted through the depth of individual concrete members. In the most favourable situations contours can be plotted for 105186。C (increased porosity of cement marix), 300186。C (red discoloration of aggregate), 500186。C (cement matrix bees wholly isotropic), 600186。C (_to _ quartz transition), 800186。C (calcination of limestone) and 1200186。C (first signs of melting). Figure 2 shows some microscopical features that may be observed in firedamaged concrete (example from Smart, 1999). Some aggregate particles have been reddened indicating that the concrete has reached at least 300186。C at that point. Particles of flint have been calcined and so have been heated to 250450186。C. The cement matrix is bisected by numerous fine cracks, some of which radiate from quartz grains in the fine aggregate fraction. This deep cracking and cracking associated with quartz suggest that the concrete has reached 550575186。C. Overall we can deduce that the concrete has been heated to the approximately 600186。C in the area represented by the sample. By determining the position of thermal contours through the crosssection of a concrete element, an estimate can also be made of the likely condition of reinforement bars. At 200400186。C prestressed steel shows considerable loss of strength, at 450186。C coldworked steel losses residual strength and at 600186。C hotrolled steel losses residual strength. Case study of a firedamaged concrete structure An investigation was misioned to determine the extent of damage caused by a large fire to the reinforced concrete frame of a tenstorey building (Figure 3). The fire started during construction and swept through three whole storeys, burning the woodern formwork that was still insitu after placement of the upper three concrete floor slabs (Figure 4). The investigation was divided into two phases. The first phase consisted of a limited trial of onsite visual inspection and petrographic examinatio