【正文】 For normalweight concrete, a value of 300106 may be used. 對(duì)常重混凝土，收縮應(yīng)變終值可取為 300106 The British Code CP100 gives a value of 500106, which represents an unrestrained shrinkage of mm in 3 m length in thin, plain concrete sections. 英國(guó) CP100 規(guī)范不出的收縮應(yīng)。鋼筋的合理分布、會(huì)使混凝土中的拉應(yīng)力分布更有利，可減小內(nèi)部應(yīng)力差。 and shape of specimen. As shrinkage takes place in a reinforced concrete member, tension stresses develop in the concrete, and equal pressive develop in the steel. These stresses are added to those developed by the loading action. Therefore, cracks may develop in concrete when a high percentage of steel is used. Proper distribution of reinforcement, by producing better distribution of tensile stresses in concrete, can 26 reduce differential internal stresses. 試件的尺寸和形狀：當(dāng)收縮在鋼筋混 凝土構(gòu)件中發(fā)生時(shí)，混凝土中產(chǎn)生拉應(yīng)力，同樣大小的壓力產(chǎn)生于鋼筋中，這些力與荷載引起的力相迭加。高溫加速了水分的蒸發(fā)，因此也加快了收縮。 , amount, and gradation of aggregate. The smaller the size of aggregate particles, the greater is the shrinkage. The greater the aggregate content, the smaller is the shrinkage. 骨料的類(lèi)型、含量及其級(jí)配：骨料的粒徑越小，收縮越大；骨料含量越大，收縮則越小。 Many factors influence the shrinkage of concrete caused by the variations in moisture conditions. 許多因素都會(huì)影響因水分環(huán)境發(fā)生變化而產(chǎn)生的混凝土收縮。 As concrete continues to dry, water evaporates and the volume of the restrained cement paste changes, causing concrete to shrink, probably due to the capillary tension that develops in the water remaining in concrete. 隨著混凝土的不斷變干，水分蒸發(fā)，受約束水泥漿的體積也變化，導(dǎo)致了混凝土的收縮，這多半是由于殘留在混凝土中的水的毛細(xì)張力所致。 Shrinkage The change in the volume of drying 23 concrete is not equal to the volume of water removed. The evaporation of free water causes little or no shrinkage. 混凝土干燥時(shí)的體積變化量不等于它所失去的水的體積。 If it loses moisture by evaporation, it shrinks, but if the concrete hardens in water, it expands. 如果蒸發(fā)失去水分，混凝土?xí)湛s；但如果在水中硬結(jié)，它便膨脹。 water content 2. cement paste 水泥漿 mortar 3. capillary tension 毛細(xì)管張力，微張力 4. gradation of aggregate 骨 料 級(jí)配 coarse fine (crushed stone, gravel) 5. The British Code PC100 英國(guó)混凝土規(guī)范 PC100。 sustainable development 18. fatigue [f??ti:?]n. 疲乏 , 疲勞 , , vi.疲勞 strength 21 試驗(yàn)物 。 humid relative humidity 16. aug`ment [?: ??ment] v. 增加 , 增大 n. 增加 。 decrease 13. creep [kri:p] n. 徐變 。 ascribe ， impute ， credit， assign， refer 4. shrinkage shrink 10. distribution [?distri?bju:??n]n. 分配 , 分發(fā) distribute distributor 11. upwind [??p?wind]adj. 逆風(fēng)的 adv. 逆 風(fēng) 地 windward。 只有 30%土樣通過(guò)的最大粒徑； D60= maximum size of the smallest 60 percent of the sample；只有 60%土樣通過(guò)的最大粒徑； From these characteristic sizes, the following grading characteristics are defined: 根據(jù)這些特征粒徑，定義出如下級(jí)配特征： Effective size 有效粒徑 Uniformity coefficient 均勻系數(shù) 19 Coefficient of gradation 級(jí)配系數(shù) Lesson 4 New Words 1. undergo [??nd????u] vt. 經(jīng)歷 , 遭受 , 忍受 。 First of all, three points are located on the grading curve to give the following characteristic sizes: 首先，定出級(jí)配曲線(xiàn)上的三個(gè)點(diǎn)以給出以下特征粒徑： D10=maximum size of the smallest 10 percent of the sample。 For example, the steep curve may be taken to 18 represent a poorlygraded medium sand, indicating a narrow range of sizes. 例如，陡峭的曲線(xiàn)可用來(lái)表示級(jí)配差的中砂，并表示其粒徑范圍比較小。 It should also be remembered that the primary object is to provide a descriptive term for the type of soil. 還應(yīng)牢記的是我們的主要目的是提供對(duì)土的類(lèi)型的描述性術(shù)語(yǔ)。 Grading Characteristics The grading curve is a graphical representation of the particlesize distribution and is therefore useful in itself as a means of describing the soil. 級(jí)配曲線(xiàn)是粒徑分布的一種圖形表達(dá)，因而可用來(lái)作為描述土的手段。 The procedure using a hydrometer consists of measuring the suspension density at a depth of 100mm at a series of elapsedtime intervals. 用液體比重計(jì)的方法包括以一系列時(shí)間 間隔在深度 100mm 處測(cè)定懸浮液的比重。 因此在，在深度 100mm 處， t 時(shí)間后所取的懸浮液中將不會(huì)有粒徑大于式 所給出的土粒 。 The soil/water suspension is then made up to 500 ml, agitated vigorously for a short while and then allowed to settle. 再?gòu)闹腥〕?500ml 的土 /水懸浮液，充分?jǐn)嚢枰粫?huì)后讓其沉降。 A process of sedimentation is normally carried out for this purpose. 通常必須用沉降法實(shí)現(xiàn)此目的。最粗的部分（即粒徑 20mm 的部分）也可被過(guò)篩，并用其結(jié)果完成級(jí)配曲線(xiàn)的繪制。 After weighing the fractions retained on each sieve and calculating the cumulative percentage passing each sieve, the grading curve is drawn. 稱(chēng)量落在每個(gè)篩中土重，并計(jì)算出通過(guò)每個(gè)的累計(jì)百分?jǐn)?shù)后，就可描出級(jí)配曲線(xiàn)。 A suitablesized subsample is first ovendried and then 14 sieved to separate the coarsest particles (20mm). 將一適量的分土樣烘干，并過(guò)篩分開(kāi)最粗的顆粒（ 20mm的顆粒） The subsample is then immersed in water containing a dispersing agent and allowed to stand before being washed through a 63?m(micron) mesh sieve. 然后將土樣浸入含有分散劑的水中，并在將其用 63 微米篩過(guò)篩 前擱置起來(lái)（并將其擱置一會(huì)，再用 63micron 的篩子過(guò)篩）。 From these figures the particlesize distribution for the soil is plotted as a semilogarithmic curve () known as grading curve. 根據(jù)這些數(shù)據(jù)，以半對(duì)數(shù)曲線(xiàn)的形 式描出該土的粒徑分布圖，即所謂的級(jí)配曲線(xiàn)。 This sample is then passed through a nest of standard test sieves arranged in descending order of mesh size. 再使烘干的土樣通過(guò)一組篩孔尺寸由大至小放置的標(biāo)準(zhǔn)試驗(yàn)篩。 In the case of a coarse soil, from which finegrained particles have been removed or were absent, the usual process is a sieve analysis. 對(duì)于粗粒土，它里面的細(xì)粒土被除去或本身就無(wú)細(xì)顆粒，常用的方法就是篩分法。 shows the British Standard range of percentage of particle sizes. 圖 為粒徑百 12 分?jǐn)?shù)的英國(guó)標(biāo)準(zhǔn)范圍。When the width of this size band is very narrow the soil will be termed poorlygraded, if it is wide the soil is said to be wellgraded. 當(dāng)這一粒徑范圍非常小時(shí)，稱(chēng)這種土級(jí)配較差，而當(dāng)其較大時(shí)，稱(chēng)這種土級(jí)配良好。 permeate, permeable seep seepage Phrases and expressions 1. frost susceptibility 霜凍敏感性 2. sieving method 篩分法 3. semilogarithmic curve 半對(duì)數(shù)曲線(xiàn) 4. grading curve 級(jí)配曲線(xiàn) 5. wet sieving 濕法篩分 6. dispersing agent 分散劑 7. Stoke?s law 斯托克定律 8. unit weight 重度 9. coefficient of grading 級(jí)配系數(shù) 10. sedimentation method 沉降法 11. particlesize distribution 粒徑分布 Text Particle Size Analysis 粒徑分析