關(guān)鍵參數(shù)對水泥漿體干燥收縮的影響外文文獻(xiàn)翻譯、中英文翻譯

XXXXX設(shè)計(XX)外文資料翻譯院 系專業(yè)學(xué)生姓名班級學(xué)號外文出處Cement and Concrete Research附件：1.外文資料翻譯譯文（約3000漢字）； 2.外文資料原文(與課題相關(guān)的1萬印刷符號左右)。指導(dǎo)教師評語：指導(dǎo)教師簽名：年月日關(guān)鍵參數(shù)對水泥漿體干燥收縮的影響摘要干燥收縮是一個混凝土結(jié)構(gòu)破壞的主要原因。材料的收縮通常阻礙由內(nèi)部或外部克制以及張應(yīng)力作用。這些應(yīng)力可能超出拉伸強(qiáng)度，引起混凝土的裂紋。對應(yīng)力分布在材料而引起的“真正”自由收縮形變。這篇論文將陳述有關(guān)的結(jié)果來評價形變的情況，并獲得更好地了解混凝土的干燥收縮行為的研究。收縮測試在水泥漿體中進(jìn)行。不同的關(guān)鍵影響參數(shù)為：相對濕度，試樣尺寸，水灰比，水泥含量。結(jié)果表明，在48%到100%相對濕度，水泥漿體的收縮成反比相對濕度。水泥砂漿的最終收縮量測量在5050400-mm試件并不是有很多不同于“真正”收縮測量的4832-mm試件。因此，在試件的實(shí)驗(yàn)中，存在的一個濕度比的下降從而在很大程度上影響最終收縮應(yīng)變。水灰比在(0.35-0.50)內(nèi)范圍發(fā)現(xiàn)對干燥收縮影響最小。然而，水泥的含量卻被認(rèn)為是最重要的影響因素。關(guān)鍵詞:水泥漿體;混凝土;干燥;濕度;收縮1.簡介干燥收縮和低抗拉強(qiáng)度，是大多數(shù)硅酸鹽水泥混凝土的不利特性1。收縮通常導(dǎo)致裂紋，即使它可能不影響結(jié)構(gòu)完整性，但會影響混凝土的耐久性2。這是對混凝土尤其是在重疊出和砂不同等級的情況下，干燥的地方會出現(xiàn)從一面起到阻礙和收縮并由外部和內(nèi)部一起約束3,4。外部限制是由于連接之間修復(fù)層和重疊情況的舊水泥混凝土，同時，對等級一樣的砂，限制來自與摩擦路基與板自重。內(nèi)部約束是由于濕度梯度在混凝土中的存在，直到在與周圍環(huán)境測濕達(dá)到平衡。局部收縮直接關(guān)系到濕度的大小，因此，收縮變形梯度存在于整個干燥過程。因此，在拉伸應(yīng)力最終可能克服混凝土的拉伸強(qiáng)度而造成的物質(zhì)和開裂和剝落5。為了提高混凝土的設(shè)計上強(qiáng)度和等級，材料的要求被定性更為準(zhǔn)確。目前，實(shí)踐（如，國際機(jī)場理事會，行政首長協(xié)調(diào)會）給予相當(dāng)不錯的模型來預(yù)測一個收縮變形6，但這些模型不適合在某些情況下，例如，計算的壓力所導(dǎo)致收縮漸變。而“真正的“收縮率的測定對混凝土應(yīng)變（即元素的大小無關(guān)）作為局部濕度的功能是用于此目的至關(guān)重要。這項研究是一個關(guān)于部分在薄壁混凝土耐久性的修復(fù)，進(jìn)行評估自由的膠凝材料收縮變形，并闡述了某些基本參數(shù)的影響對干燥收縮影響。收縮試驗(yàn)，進(jìn)行了水泥漿體，混凝土。研究參數(shù)分別為：相對濕度，試樣尺寸，水灰比，水泥量。2.測試方法為了獲得更好的收縮現(xiàn)象的認(rèn)識并評價“真正的”自由收縮變形，更重要的是要考慮的關(guān)鍵參數(shù)影響，如標(biāo)本的大小和相對濕度。對干燥收縮測量，進(jìn)行了兩不同大小的標(biāo)本：4832毫米和5050400毫米棱鏡。較小的試件進(jìn)行了足夠的研究以獲得約束梯度自由收縮。這是在以往的研究表明7,8中關(guān)于厚度在13毫米水泥漿體試件不同影響平衡的收縮。 在較小的試件進(jìn)行了收縮試驗(yàn)，相對濕度在三個級別（48%，75%和92）。這些值的范圍從一般的最低發(fā)生的溫和氣候條件下（50），以此來接近完全飽和的條件（100）。對較大的試件，在所有測試48的相對濕度。在兩個W/ C比值被選定（0.35和0.50）下，一般認(rèn)為是比較大的變化范圍，從而得到高到正常質(zhì)量的膠凝材料。 為了表示漿體量之間的關(guān)系（或者來說，集料量），并最終導(dǎo)致收縮，對水泥漿體、混凝土進(jìn)行了研究。在有混凝土的情況下，膠砂比分別為1和2，水灰比在混凝土分別為0.30和0.35。粗骨料砂率（在混凝土）維持在1.5不變，以減少參數(shù)的數(shù)目。3 混合物的組成及實(shí)驗(yàn)程序3.1混合物所有混合物都是用相同的普通硅酸鹽水泥?；瘜W(xué)成分和水泥物理性能見表1。使用的花崗巖砂的細(xì)度模量為2.46，其分級如表2所示。最大標(biāo)稱尺寸為10毫米的石灰?guī)r碎石用作粗骨料。對于與W/ C的0.35，這一比例的混凝土外加劑（含有33的固體和單位重量為1.1）一般用在3.8毫升/公斤，以使其水泥用量可提供穩(wěn)定可操作性。該混合物的比例和新的混合物如表3（水泥漿體和砂漿）和表4（混凝土）?；旌衔镏諝夂繙y定按美國ASTM C138重量測試方法。水泥和砂在10L的垂直軸砂漿攪拌機(jī)?；炷粱旌衔镌谝慌?00L的鍋攪拌機(jī)。所有的混合物是指在相同順序下放入攪拌機(jī)。水泥首先加入，水漸漸地增加，直到獲得均勻的糊狀。此時的沙和水泥至少2分鐘后才能混合。對于混凝土混合物，所有的（水泥，沙子）粗骨料，加入攪拌機(jī)后，水（含高效減水劑）其后逐步添加并至少持續(xù)15分鐘。3.2實(shí)驗(yàn)步驟 對于每一個混合物，五個樣本（2個100 200毫米氣瓶和三個50 50 400毫米模具）分成兩層模具進(jìn)行振動。對于水泥漿體和砂漿，另外的250322575毫米模具，是進(jìn)行小試樣（43832毫米）在（在固化期）為自收縮測量。 24小時后，所有的試件拆模并放在室溫下養(yǎng)護(hù)28天。養(yǎng)護(hù)是為確保有關(guān)條件不能使其干燥。 28天抗壓強(qiáng)度的試驗(yàn)根據(jù)試件的強(qiáng)度值做成圓柱形圖，一般要求為ASTM的C39。這些測試的結(jié)果列于表3和4。 在28天后，5050400毫米模具被放置 在溫度（23）和相對相對濕度（48）恒定的養(yǎng)護(hù)室中。在不同的養(yǎng)護(hù)齡期，對長度變化和質(zhì)量的變化進(jìn)行測定。28天齡期后，將4832毫米的試件，用來測量自由收縮變形的試件放置在干燥飽和三鹽溶液器中。據(jù)對化學(xué)平衡的定律9，飽和食鹽在一個固定的溫度能提供了一個恒濕的封閉的環(huán)境。在這個實(shí)驗(yàn)中，三鹽（碳酸鈉，氯化鈉和碳酸鉀）是用來提供三種不同的濕度在干燥器的（92%，75%和48）。將一個真空器引入這些干燥器，以避免在測試期間碳化。 由于試件的體積非常小，并不可避免的干燥器的相對濕度變化，通常的測量設(shè)備無法使用。對于一個光應(yīng)變系統(tǒng)，在允許長度測量從干燥器外部變化就可以利用。這個裝置，有引伸和自準(zhǔn)直儀組成，根據(jù)光反射原理工作。把引伸安裝在試件上使其放置了兩個鏡子，其中一個是固定的，另外可以旋轉(zhuǎn)（菱形）。該長度變化的測量條件為自準(zhǔn)直儀，它是閱讀分光儀，其靈敏度為獨(dú)立的量具的距離所決定。這個反射儀由兩個反射鏡的光形成圖像出現(xiàn)在自準(zhǔn)直儀視野中。在位于圖像中心是一個菱形旋轉(zhuǎn)功能所造成的試樣變形。圖一簡圖展示了如何從自準(zhǔn)直光來反映在固定鏡子菱形回自準(zhǔn)直儀，來形成圖像。4.試驗(yàn)結(jié)果4.1收縮4832毫米標(biāo)本4832毫米水泥漿體和砂漿試件干燥收縮如下圖.2。在每個圖中，作為時間函數(shù)的收縮體現(xiàn)出這三個實(shí)驗(yàn)顯示出的濕度水平。每條曲線表示的平均價獲得到了兩個試件。如圖2的結(jié)果，表明干燥速度極為快，經(jīng)過1天的干燥收縮一般占60的最終收縮或更多。在所有情況下，一個給定的砂漿的W/ C比減少從0.50至0.35導(dǎo)致略低收縮。正如設(shè)想，干燥收縮率降低非常顯與水泥量。從相對濕度為48，減少到平均約3200毫米/米至950毫米/米的砂漿總的膠灰比為2.0。從中可以進(jìn)一步看出，在圖2中收縮還是相當(dāng)顯著，在相對濕度為92而“最終“線性收縮率相對增加與相對濕度在92%和48的下降。4.2收縮5050400毫米標(biāo)本如圖3給出的干燥收縮試驗(yàn)結(jié)果5050400毫米的試件，砂漿和48相對濕度混凝土。每條曲線在四個圖上代表了三個平均結(jié)果的試件。 “最終”收縮測量范圍在平均約600毫米/米四個混凝土和3000毫米/米的水泥漿體。從圖3可以得到，對干燥速率慢得多為5050400毫米以上較小的試件。即使經(jīng)過500天，測濕平衡還沒有完全達(dá)到。此外，試件的W/ C比對一般的影響對這些較大的試件更明顯，相比與它與較小的試件。水泥量的效果是相似的，隨著薄試件觀而變化。5討論5.1 W / C比 總體而言，影響干燥的W / C比對漿體和水泥砂漿試樣的情況不同，并可以在收縮值范圍測定（瓦特/ 5 0.35和0.50），在（圖2）中可以觀察到相對小。從早先進(jìn)行的收縮數(shù)據(jù)8,10-12，可以得出W/ C對漿料和水泥砂漿產(chǎn)生重大影響。嚴(yán)格的比較是不同，由于實(shí)驗(yàn)的差異和材料不同。例如，實(shí)驗(yàn)由皮克特10在0.35和0.50 W / C比漿料和水泥砂漿進(jìn)行了超過40年的大試件（19.0325.4毫米截面）實(shí)驗(yàn)，從而作出的推測粗水泥和不使用任何塑化外加劑。在其他研究8,11,12，在W/ C比實(shí)驗(yàn)范圍高（0.54和0.60），甚至更高的W / C比，研究發(fā)現(xiàn)其效果在較大的漿體和水泥砂漿試件（圖3）中水的擴(kuò)散率降低水泥水化與W/ C比。因此，影響干燥收縮的大小和速度可能有共同的放大值，期間的差異將獲兩個瓦/ C比值。這種影響仍然相當(dāng)小，但并在具體實(shí)驗(yàn)（圖3B和三維），它不會明顯出現(xiàn)。這種W/ C比的影響也會減少，對于不同的研究人員在砂漿的試件13和混凝土14-16的實(shí)驗(yàn)中。 雖然目前的研究還沒有定論，使得W/ C比的影響力對干燥水泥基材料收縮還不確定，使得這樣的研究在符合條件的限制下可能不那么重要。這是可能再次為限定w/ C的范圍和條件，即一些是在W/取決于幾個因素收縮率及影響（孔徑分布，總孔隙率，彈性模量，蠕變，水?dāng)U散等）可能有這樣一種方式，相反個別效果整體效果是相當(dāng)小。這是重要的，因?yàn)樽畛Ｒ姷幕炷粱旌衔飳儆趯?shí)際范圍控制的W / C比內(nèi)。 值得一提的是砂漿收縮模型與混凝土的收縮一般會隨預(yù)期這種W/ C比減少。在實(shí)際的情況下W/ C比只考慮效果明確模型是關(guān)系到體積計算的制約所提供的未水化水泥顆粒，預(yù)測主要依賴于實(shí)際的收縮實(shí)驗(yàn)測定水泥凈漿試件。事實(shí)上，這種關(guān)系對實(shí)驗(yàn)數(shù)據(jù)是最真實(shí)可用模型。令人驚訝的是有關(guān)W/ C比影響水泥漿體收縮后的數(shù)據(jù)是相當(dāng)稀缺。5.2 尺寸效應(yīng) 最終的兩個水泥收縮試件原料和四個獲得這兩個試件砂漿大小在實(shí)驗(yàn)如表5所示。試樣的大小使干燥速率的影響強(qiáng)烈，可以從表中的最終變形看出。因此，對于較大規(guī)模在這項研究中使用，可以看來，濕度梯度沒有大的影響在對最終的收縮。在濕度梯度場的沒一個漿料明顯的：在第一天干燥，裂紋圖案覆蓋整個表面在所有清晰可見5050400毫米的標(biāo)試件。因此，可以看來，表面裂縫是發(fā)生在早期階段干燥收縮，往往會降低整體現(xiàn)象或“明顯“收縮3，可能會逐漸接近干燥。在干燥過程結(jié)束時，試件變形然后很接近自由收縮變形。這個過程實(shí)際上是通過光學(xué)顯微鏡上觀察從1至3毫米7薄試件得出的。5.3 相對濕度 收縮率和相對濕度為同時的關(guān)系時，可以提出了漿體和砂漿圖4。數(shù)據(jù)在此圖顯示了測試結(jié)果，獲得4832毫米的試件和數(shù)據(jù)代表收縮分?jǐn)?shù)在48相對濕度測量的收縮。對于漿體，可以看出，幾乎增加收縮線性關(guān)系，在相對濕度下降為100%和48。在砂漿為48%至75的相對濕度低情況時，那么它在75%至100的增長相對濕度范圍將對W/ C比的影響力似乎非常小。5.4漿體量 由于水泥漿體的收縮是水泥漿體是主要特征，這一點(diǎn)在圖5可以顯示出來，相對收縮，關(guān)于漿體量對于兩個W/ C比值的影響。收縮數(shù)據(jù)從上執(zhí)行相應(yīng)的測試所得的較大的試件得到，并在來表示的分?jǐn)?shù)應(yīng)變測量水泥凈漿試件。 如圖所示的曲線五清楚地表明了抑制聚集效應(yīng)，結(jié)果與彈性理論曲線吻合較好，是凸或凹取決于彈性模量（和相對值泊松系數(shù)水泥凈漿和聚合）11。有趣的是注意到，“最終”混凝土的收縮總體積含量通常位于65至75，約等于15%至25整潔的水泥漿體的收縮。圖5還清楚地表明了這對關(guān)系的影響的W / C比體積收縮和漿體是非常小。 漿體量之間的關(guān)系的內(nèi)容及“最終”減少（單位體積）如圖所示6所示。這些數(shù)據(jù)再次對應(yīng)了從測試所得的進(jìn)行了較大的試件。他們清楚地表明該材料的數(shù)量，每單位重量的損失是直接成比例的兩個瓦/ C比值漿體量：在比重較高導(dǎo)致更高的減少，只是由于自由水含量越高。5.5干縮對比減少 在圖7中干燥收縮是針對減少所有的混合物策的實(shí)驗(yàn)。這些數(shù)據(jù)也對應(yīng)從測試所得的進(jìn)行了較大試件。對于與W/ C的0.35比所有的混合物，收縮率約成正比的水分流失。在W/ C的0.50混合物的情況下，水失去了早期干燥收縮小階段的原因，因?yàn)檫@些水主要來自大型毛細(xì)管孔隙17。隨后，該曲線的斜率變?yōu)榧s等于到W/ C的0.35混合物。 應(yīng)當(dāng)指出，動態(tài)收縮暴露于不同的試件減少薄曲線相對濕度將提供進(jìn)一步的評價在短暫的水分梯度的潛在影響。在另一項實(shí)驗(yàn)中提出這樣的測量8結(jié)果表明，在收縮2.3毫米厚的測量試件，沒有發(fā)生顯著影響的梯度，因此，測量反映了真正的材料收縮。不過，與實(shí)驗(yàn)在這項研究中用于安裝長度的測定上薄試樣的變化，這是無法估量他們在測試的重量的變化。朗讀6 結(jié)論 結(jié)果表明，對于試樣尺寸在本實(shí)驗(yàn)研究范圍（4832和5050400毫米），這個參數(shù)對收縮率有明顯的影響，但對“最終”的收縮量影響不大。他實(shí)驗(yàn)還表明，在濕度48%至100之間，干燥收縮率約反比與相對濕度。對于那些水灰比在0.35到0.5時，在這個比值其相對較少收縮影響減少。此外，測試結(jié)果證實(shí)在膠凝材料的收縮幅度與漿體量成正比。Influence of key parameters on drying shrinkage of cementitious materialsAbstract Drying shrinkage can be a major cause of the deterioration of concrete structures. The contraction of the material is normally hindered by either internal or external restraints and tensile stresses are induced. These stresses may exceed the tensile strength and cause concrete to crack. The evaluation of the stress distribution in the material requires the knowledge of the “real” free shrinkage deformation. This paper presents the results of a study performed to evaluate this deformation and obtain a better understanding of the behavior of concrete under drying conditions. Shrinkage tests were carried out on cement pastes, mortars, and concretes. The influences of different key parameters were evaluated: relative humidity, specimen size, water/cement ratio, and paste volume. The results indicate that between 48 and 100% relative humidity, the shrinkage of cement paste is approximately inversely proportional to relative humidity. Results also show that the ultimate shrinkage of pastes and mortars measured on 50350 400-mm specimens does not differ much from the “real” shrinkage measured on 4832-mm specimens. Thus, for the specimen dimensions investigated in this study, the existence of a humidity gradient did not affect to a large extent the ultimate shrinkage strain. The influence of the water/cement ratio, within the range investigated (0.350.50), was found to be relatively small. Conversely, paste volume was observed to have a very strong influence. 1999 Elsevier Science Ltd. All rights reserved. Keywords: Cement paste; Concrete; Drying; Humidity; Shrinkage1. Introduction Drying shrinkage, together with its low tensile strength, is probably the most disadvantageous property of Portland cement concrete 1. Shrinkage generally leads to cracking and, even though it may not affect the structural integrity, durability problems are generally increased 2. This is particularly true in the case of concrete overlays and slabs on grade where drying occurs from one face only and shrinkage is hindered by external and internal restraints 3,4. The external restraint is due to the bond between the repair layer and the old concrete in the case of overlays, while, for slabs on grade, it comes from the friction with the subgrade and the slab self-weight. The internal restraint is caused by the humidity gradient that exists in concrete until the hygrometric equilibrium with the surroundings is reached. Local shrinkage is directly related to pore humidity; there-fore, a gradient of shrinkage deformation exists throughout the drying process. Tensile stresses are thus induced in the concrete and may eventually overcome the tensile strength of the material and cause cracking and debonding of over-lays 5.To improve the design of concrete overlays and slabs on grade, the material behavior under drying has to be characterized more precisely. Presently, codes of practice (e.g., ACI, CEB) give fairly good models to predict shrinkage as a global deformation 6, but these models are unsuitable in some cases, for instance, to compute the stresses induced by a shrinkage gradient. The determination of the “real” shrink-age strain of concrete (i.e. independent of the element size) as a function of local humidity is essential for this purpose. This study, which is part of a research program on the durability of thin concrete repairs, was performed to evaluate the free shrinkage deformation of cementitious materials and to characterize the influence of certain basic parameterson this deformation. Shrinkage tests were carried out on cement pastes, mortars, and concretes. The parameters studied were: relative humidity, specimen size, water/cement (W/C) ratio, and paste volume. 2. Test program To obtain a better understanding of the shrinkage phenomenon and to evaluate the “real” free shrinkage deformation, it is important to take into account the influence of key parameters such as the size of specimens and the relative humidity.Drying shrinkage measurements were carried out on twodifferent sizes of specimens: 4832-mm and 5050400-mm prisms. The smaller specimens were considered thin enough to obtain approximately gradient-free shrink-age. It was shown in previous studies 7,8 that the thickness of cement paste specimens in the range of 1 to 3 mm does not affect equilibrium shrinkage.The shrinkage tests on the smaller specimens were per-formed at three relative humidity levels (48, 75, and 92%). These values range from the minimum occurring generally in moderate climates to close to full saturation conditions (100%). The larger specimens were all tested at 48% relative humidity.The two W/C ratios that were selected (0.35 and 0.50) were considered to cover fairly well the range from high- to normal-quality cementitious materials.In order to characterize the relation between paste volume (or, conversely, aggregate content) and ultimate shrinkage, cement pastes, mortars, and concretes were investigated. In the case of mortars, the sand/cement weight ratios chosen were 1 and 2, respectively. The paste volume fractions of the concretes were 0.30 and 0.35. The coarse aggregate to sand ratio (in concretes) was kept constant at 1.5 to reduce the number of parameters. 3. Mixture composition and experimental procedures3.1. Mixtures All mixtures were made with the same Canadian (Type 10) normal Portland cement. The chemical composition and physical properties of this cement are given in Table 1. A granitic sand having a modulus of fineness of 2.46 was used; its grading is shown in Table 2. A 10-mm maximum nominal size crushed limestone was used as coarse aggregate. For the concrete mixtures with a W/C ratio of 0.35, a melamine-based super plasticizing admixture (containing 33% solids and having a unit weight of 1.1) was used at a dosage of 3.8mL/kg of cement to provide a satisfactory workability. The mixture proportions and the properties of the fresh mixtures are given in Table 3 (cement pastes and mortars) and Table 4 (concretes). The air content of the mixtures was determined according to the ASTM C138 gravimetric test method.Cement pastes and mortars were batched in a 10-L vertical axis mortar mixer. Concrete mixtures were batched in a 100-L pan mixer. All mixtures were batched at atmospheric pressure and the constituents were always introduced into the mixer following the same sequence. The cement wasfirst introduced and the water was progressively added until a homogeneous paste was obtained. The sand was then added and the mortars were mixed for at least 2 min. For the concrete mixtures, all the dry constituents (cement, sand, and coarse aggregates) were first introduced in the mixer.The water (containing the super plasticizer) was then progressively added and mixing continued for at least 15 min.3.2. Experimental proceduresFor each mixture, five specimens (two 100200-mm cylinders and three 5050400-mm prisms) were cast into molds in two layers consolidated by vibration. For the cement pastes and mortars, an additional 25022575-mm prism was cast from which small specimens (4832 mm) were sawed (during the curing period) for the free shrinkage measurements. After 24 h, all the specimens were demolded and cured in lime-saturated water at ambient temperature (23) for 28 days prior to testing. Care was taken to ensure that the specimens were never allowed to dry. The 28-day compressive strength tests were carried out on the cylindrical specimens according to the requirements of ASTM C39. The results of these tests are given in Tables 3 and 4. At 28 days, the 5050400-mm prisms were placed in a room at a constant temperature (23) and a constant relative humidity level (48%). At different time intervals, the length change and the mass of the specimens were measured. After the curing period, the 4832 mm prisms used to evaluate the free shrinkage deformations were placed in three desiccators over three saturated salt solutions. According to the laws of chemical equilibrium 9, a saturated salt solution at a fixed temperature gives a constant humidity level in a closed space. In this study, three salts。 were used to provide three different humidity levels (92, 75, and 48%) in the desiccators. A vacuum was introduced into these desiccators to avoid carbonation during the testing period.Because of the very small size of the specimens and to avoid undesirable relative humidity variations in the desiccators, usual measuring devices could not be used. An optical strain gage system allowing the measurement of length change from outside of the desiccators was thus used. This device, composed of an extensometer and an autocollimator, works upon the principle of light reflection. The extensometer mounted on the specimen incorporates two mirrors, one of which is fixed and the other can rotate (lozenge). The length change is measured with the autocollimator, which is a reading auto collimating telescope whose sensitivity is in-dependent of the distance from the gage. The reflection of light by the two mirrors causes an image to appear in the autocollimator field of view. The position of the image on the reticule scale is a function of the lozenge rotation caused by the specimen deformation. Fig. 1 displays a simplified diagram showing how light coming from the autocollimator is reflected by the lozenge to the fixed mirror and back to the autocollimator to form an image. The resolution of the devices used in this study.4. Test results4.1. Shrinkage of 4832-mm specimensThe results of the drying shrinkage tests on the 4832-mm specimens of paste and mortar are presented in Fig. On each graph, the shrinkage as a function of time is shown for the three humidity levels investigated. Each curve represents the average value obtained for two specimens. The results in Fig. 2 clearly show that the rate of drying is extremely rapid. After 1 day, the recorded value generally represents 60% or more of the “ultimate” shrinkage. In all cases, for a given paste content the reduction of the W/C ratio from 0.50 to 0.35 resulted in a slightly lower shrinkage. As expected, drying shrinkage decreases very significantly with the paste volume. At 48% relative humidity, it de-creases from an average of approximately 3200 for the pastes to 950m/m for the mortars with an aggregate/ cement ratio of 2.0. It can further be seen in Fig. 2 that shrinkage is still quite significant at 92% relative humidity and that the “ultimate” shrinkage increases relatively linearly with a decrease in relative humidity between 92 and 48%.4.2. Shrinkage of 5050400-mm specimens Fig. 3 presents the results of the drying shrinkage tests performed on the 5050400-mm specimens of paste, mortar, and concrete at 48% relative humidity. Each curve on the four graphs represents the average result for three specimens. The “ultimate” shrinkage measured ranges between an average of approximately 600m/m for the four concretes to 3000m/m for the cement pastes.It is quite evident from Fig. 3 that the rate of drying is much slower for the 5050400-mm specimens than for the smaller specimens. Even after 500 days, hygrometric equilibrium has not been completely reached. In addition, the influence of the W/C ratio generally appears to be a little more pronounced for these larger specimens than it is with the smaller ones. The effect of paste volume, however, appears to be similar to that observed with the thin specimens.5. Discussion5.1. W/C ratio Overall, the influence of the W/C ratio upon drying shrinkage of the thin paste and mortar specimens, for a given paste content and within the range of values investigated (W/C0.35 and 0.50), is observed to be relatively small (Fig. 2). Shrinkage data from earlier investigations8,1012 indicate a more significant influence of the W/C ratio for pastes and mortars. Strict comparisons are hazardous however, because of miscellaneous differences in experimental procedures and materials. For example, the experiments by Pickett 10 on 0.35 and 0.50 W/C ratio pastes and mortars were conducted over 40 years ago on larger specimens (19.025.4-mm cross-section) made with pre