外文翻譯=凍結(jié)解凍混凝土耐久性與回收拆遷總comparedto原始骨料混凝土=4000字符

中國地質(zhì)大學(xué)長城學(xué)院 本科 畢業(yè)論文外文資料翻譯 系 別 ： 工程技術(shù)系 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 姓 名： 朱雅靜 學(xué) 號(hào)： 05211405 2015 年 3 月 27 日 外文資料翻譯譯文 凍結(jié) /解凍混凝土耐久性與回收拆遷總comparedto 原始骨料混凝土 艾倫 理查森 *凱瑟琳考文垂 ,詹妮弗培根 諾森布里 亞大學(xué)的學(xué)校的建筑環(huán)境 ,英國紐卡斯?fàn)?1 介紹 在英國所有使用的需求總量約為 270噸 / y,這種需求 70噸來自中等和再生骨料 (BRMCA,2008)。這個(gè)測(cè)試 programmeinvestigated 凍結(jié) /解凍耐久性混凝土的處理 和再生骨料生產(chǎn)。具體測(cè)試的范圍 ;平原 ,加氣和 1 型聚丙烯纖維。當(dāng)時(shí)相對(duì)性能檢查強(qiáng)調(diào)再生骨料性能耐久性。 在具體使用時(shí)知道聚丙烯纖維和空氣夾 凍結(jié) /解凍保護(hù)品質(zhì) (理查森 ,2003;理查森和威爾金森 ,2003)?；炷辽a(chǎn)使用純處理 聚合通常有更高的抗壓強(qiáng)度相比 ,由循環(huán)拆遷垃 圾骨料混凝土 (理查森 et al .,2009)。指定使用抗壓強(qiáng)度作為混凝土通常是非常適宜性的指標(biāo) ,但這可能不是比例方面的耐久性。 1.1 耐用性 耐久性內(nèi)定義簡潔 Eurocode 2(2006),說 ,“一個(gè)持久的結(jié)構(gòu)應(yīng)當(dāng)滿足適用性的要求 ,強(qiáng)度和穩(wěn)定性在其預(yù)期的工作生活 ,沒有重大損失效用或過度維護(hù)的 (Narayan Goodchild,2006)。杰姆的耐久性特點(diǎn) 1(硅酸鹽水泥 )混凝土有或沒有添加聚丙烯纖維顯著 sustainedWorld 作為主要結(jié)構(gòu)材料。一致的控制在耐久混凝土破壞的生產(chǎn)材料供應(yīng)限制的數(shù)量和質(zhì) 量 ,這種情況尤其相關(guān)的處理回收材料。缺乏設(shè)計(jì)和規(guī)范指南出版回收材料及其相關(guān)建設(shè)實(shí)踐 ,讓人不愿完全意識(shí)到潛在的這些材料在不同的曝光條件。因此本文旨在解決混凝土的行為嚴(yán)重暴露條件下利用再生骨料 ,為這個(gè)調(diào)查的目的定義為重復(fù)凍結(jié) /解凍周期。 1.2 材料 在這項(xiàng)研究中使用的材料包括原始骨料和角粉碎回收拆遷廢料 ,和它的目的是使用兩種類型的制造混凝土來比較它們的相對(duì)性能。 普通混凝土、骨料由砂、礫石和碎石 ,是混凝土的重要組成部分。為了提供一個(gè)堅(jiān)實(shí)的 ,強(qiáng)大和未被污染的混合 ,骨料必須擺脫粘土涂料和任何其他元素 ,可能導(dǎo)致混凝 土削弱 (可持續(xù)的混凝土 ,2009)。再生骨料內(nèi)可能會(huì)有很多有害的材料構(gòu)成 ,這些會(huì)影響混凝土的質(zhì)量。 1.2.1 節(jié)認(rèn)為這些聚合之前使用的處理限制這種潛在影響混凝土的質(zhì)量為這次調(diào)查而設(shè)計(jì)的。研究結(jié)果對(duì)混合設(shè)計(jì)采用比較原始骨料 1.2.2 節(jié)中指定的。 混合是通過添加水和水化學(xué) 1.2.3 節(jié)而突出顯示部分 1.2.4 指定纖維采用認(rèn)為負(fù)擔(dān) freezeethaw 保護(hù) (里查德森 ,2003)和化學(xué)當(dāng)量比較混合使用。 1.2.5 最終部分說明了提出的混合設(shè)計(jì)被采納。 1.2.1 再生骨料 先前的研究 (理查森 et al .,2009)表明 ,再生骨料的使用導(dǎo)致的減少與原始骨料抗壓強(qiáng)度相比。邁耶 (2009)發(fā)現(xiàn) ,最減少強(qiáng)度混凝土與再生粗骨料在 5 e24%的范圍 ,而具體由原始骨料。當(dāng)粗和細(xì)骨料都獲得再生混凝土 ,強(qiáng)度降低范圍從 15%到 40%,相比之下 ,只有天然材料制作的混凝土”。 Zaharieva et al。 (2004)發(fā)現(xiàn) ,再生骨料的高吸收率 (RA)的主要障礙使用混凝土制造、新拌、再生骨料混凝土 (RAC)很快就失去了最初的可加工性 ,即使使用超級(jí)增塑劑。防止吸入 RA,拌和水的 必要 pre-soak 他們?；炷恋目紫抖群臀招再|(zhì)用再生骨料也難以準(zhǔn)確量化作為再生骨料的高孔隙度主要是由于殘留的砂漿堅(jiān)持原來的聚合(BS EN 1097 - 6:2000,1097)。孔隙度可能會(huì)提供一個(gè)更大的空隙系統(tǒng) ,將產(chǎn)生較低的抗壓強(qiáng)度和援助的保護(hù)混凝土從凍結(jié) /解凍損傷。角粉碎回收總已篩 ,洗前使用和分級(jí)配置文件類似于圣母碎石與更多中間總活在當(dāng)下。百分之七十 aggregatewas 8 e20 毫米紅 /藍(lán)破磚工程質(zhì)量和剩余的碎混凝土的一個(gè)未知的力量。 使用的再生骨料 ,清洗和浸泡前配料和他們直接替換 1107公斤礫石成分的混合設(shè)計(jì)。數(shù)據(jù)集被標(biāo)記為便于識(shí)別。 1.2.2 維珍總 量 總之 ,這個(gè)測(cè)試是圓形的海洋疏浚和洗礫石 ,間斷級(jí)配的最大總大小 20毫米。砂洗前使用 ,因此分級(jí)配置文件表 1 所示的唯一總替換是粗骨料。這個(gè)總替換 Zaharieva et al。 (2004)定義為 RAC1 產(chǎn)生凍結(jié) /解凍耐久性方面令人滿意的結(jié)果。 它的總吸收自然礫石中使用這個(gè)測(cè)試是 1.4%確定用電石裝置。獲得的價(jià)值是價(jià)值 ,提供了一個(gè)總準(zhǔn)備使用飽和但表面干燥條件中定義的 BS EN 1097 - 6:2000(2000)。 1.2.3 批處理水 混凝土拌和水的質(zhì)量為生產(chǎn)會(huì)影響設(shè)置時(shí)間 ,混凝土的強(qiáng)度發(fā)展和保護(hù)鋼筋腐蝕。 飲用水 ,稱為水是適合人類食用適合使用根據(jù) BS EN 1008:2002(2002)。 Northumbrian 水務(wù)提供的自來水 (2010),用于設(shè)計(jì)混合 ,包含以下的化學(xué)物質(zhì)。 平均為 78.750 mg / L 硫酸鹽溶解。 水中的鈉含量介于 13 和 17 毫克 /升 (15.5 mg / L),當(dāng)鈉硫酸鹽的形式也可以是有害的在混凝土 (Darby et al .,2002)。 氯在水里也存在平均為 14.75 mg / L。 在 水 中 的 化 學(xué) 物 質(zhì) 的 比 例 ,不 會(huì) 影 響 混 凝 土 的 性 能 對(duì) 凍 結(jié) / thawperformance 使用符合 BS EN 1008:2002 行蹤 ,對(duì)混凝土拌合水。 1.2.4。聚丙烯纖維和空氣夾帶 (凍結(jié) /解凍保護(hù) ) 12 毫米 35 微米 1 型聚丙烯纖維符合 BS EN 14889:2006(2006)使用劑量為 0.9 公斤 /立方米。 引氣劑添加的劑量 50 毫升每 100公斤水泥達(dá)到最小的自然和添加空隙系統(tǒng) 4 e7%按照制造商和阿特金斯 (2010)建議。三萜皂苷是提供的活性成分 ,在液態(tài)形式分散在批處理。使用引氣劑的利益結(jié)果乘火車從它的能力 ,在一個(gè)具體的矩陣 ,無數(shù)氣孔可以緩解壓力由于液壓從冰冷的水。大小的泡沫攜入的 ,明顯依賴于吸入過 程。空洞并不都是相同的大小 ,通常范圍從 0.05 至1.25 毫米 (Palliere,1994)。 1.2.5?；炷两Y(jié)構(gòu)設(shè)計(jì) 測(cè)試是一個(gè)甜的混合料配合比設(shè)計(jì)在 28 天抗壓強(qiáng)度 ,在房屋建筑常用的在英國?；旌蠚怏w的組成部分是 :240 公斤杰姆 1 水泥、粗砂 731 公斤、731 公斤 20 毫米礫石或清洗回收拆遷廢料、 0.8 e 水 /水泥比 ,0.9 千克 /立方米 e 聚丙烯纖維 (1 型 )和一個(gè)空氣夾帶添加劑。 2 方法 2.1 介紹 為本調(diào)查旨在開發(fā)的方法比較原始骨料混凝土的抗壓強(qiáng)度與混凝土再生骨料生產(chǎn)。在這兩個(gè)分組混合設(shè)計(jì) ,子群混合設(shè)計(jì)研 究聚丙烯纖維的影響和夾雜空氣劑添加的凍結(jié) /解凍保護(hù)規(guī)定的混凝土的抗壓強(qiáng)度和比較測(cè)試袒露心聲 ,普通混凝土受到 freezeethaw 周期也將被執(zhí)行。 促進(jìn)壓縮測(cè)試混凝土是形成多維數(shù)據(jù)集 (100 毫米 100 毫米 100 毫米 )。采用混凝土測(cè)試樣本的大小和形狀是由考慮后勤要求人工自然的實(shí)驗(yàn)室工作 100 毫米 150 毫米的立方體更輕比混凝土立方體。較小的多維數(shù)據(jù)集維度也產(chǎn)生一個(gè)多維數(shù)據(jù)集較大的表面積體積比 ,從而確保嚴(yán)重的測(cè)試條件。表 3 顯示了數(shù)據(jù)集的數(shù)量相對(duì)于生產(chǎn)各種混合設(shè)計(jì)。 2.2 維數(shù)據(jù)集生產(chǎn)方法 為了避免骨料破壞纖維 ,纖 維中加入濕混合時(shí)間和混合直到均勻分散。concretewas 批處理使用旋轉(zhuǎn)圓筒混合機(jī)和檢查的一致性使用坍落試驗(yàn) BS EN 12350 e2:2000 記錄衰退值 10 mmfor 圣母素混凝土 (VP)和 30 mm 的回收平原 (RP)混凝土衰退的差異值為同一水灰比可以歸因于飽和骨料的使用。混凝土坍落試驗(yàn)后 ,倒到一個(gè)托盤 ,分成三個(gè)相等的部分 ,一部分返回的初始混合罐 (聚丙烯纖維添加 )一部分放入第二個(gè)鼓 (添加了化學(xué)夾雜空氣 ),而第三部分直接放置到多維數(shù)據(jù)集模具形成了簡單的立方體。增加發(fā)生鼓被允許在哪里進(jìn)一步旋轉(zhuǎn)通過混凝土混 合促進(jìn)徹底消散。 一天后固化模具 ,模具被襲擊 ,五天的養(yǎng)護(hù)混凝土前發(fā)生在水浴接受凍結(jié) /解凍周期 ,這確保充分飽和凍結(jié) /解凍測(cè)試開始之前。有限的養(yǎng)護(hù)加速凍結(jié) /解凍測(cè)試通過確保低立方體強(qiáng)度發(fā)展加上一個(gè)開放的形成毛細(xì)管系統(tǒng)(Basheer Barbhuiya,2010)由于采用高水灰比。這種設(shè)計(jì)確保了可記錄的凍結(jié) /解凍響應(yīng)。決定使用一個(gè)低強(qiáng)度混凝土高 w / c 比值是基于工作雅各布森 et al .(1996),因?yàn)樗麄兟暦Q“零或非常小冰的形成發(fā)生在混凝土的w / c 比 0.4 和 0.35”。他們還狀態(tài) ,“一半或更少的水吸收 freezeable -20和很少的冰的形成可以啟動(dòng)過程 ,導(dǎo)致重大損失”。 2.3 試程序 三立方體的六個(gè)混凝土混合被用于確定初始強(qiáng)度混凝土之前 ,任何接觸凍結(jié) /解凍周期。 凍結(jié) /解凍測(cè)試是基于 ASTM 666 為基礎(chǔ)的 (ASTMC 666),減肥進(jìn)行檢查和凍結(jié)和融化在 -18空氣在水中進(jìn)行的核心溫度在 20 ,直到測(cè)試數(shù)據(jù)集達(dá)到 6。 BS 15177:2006 被用來通知測(cè)試的持續(xù)時(shí)間 ,這僅限于 56 周期和兩個(gè)完整凍結(jié) /解凍周期每天進(jìn)行。立方體測(cè)試都是質(zhì)量的監(jiān)控每七凍結(jié) /解凍周期和記錄顯示體重下降的趨勢(shì)。 剩下的 三個(gè)從每個(gè)混合混凝土立方體測(cè)試結(jié)束時(shí)凍結(jié) /解凍程序提供一個(gè)實(shí)力比較凍結(jié) /解凍多維數(shù)據(jù)集和多維數(shù)據(jù)集控制。 3 結(jié)果 混凝土的密度變化表 4所示 ,使用密度表示相對(duì)于普通混凝土的密度使用相關(guān)的總分類每集成批的。純數(shù)據(jù)集之間的百分比變化很小 (0.5%)和-1.2 - -2.8%的密度減少反映了空氣的量存在于每一個(gè)批次。產(chǎn)生的再生骨料混凝土密度最高的時(shí)候相比普通混凝土生產(chǎn)與海洋疏浚礫石。角再生骨料結(jié)合藍(lán)磚出現(xiàn)在再生骨料的比例混合被認(rèn)為產(chǎn)生更高的粒子包裝內(nèi)觀察到相對(duì)的抗壓強(qiáng)度和密度值。 混凝土的強(qiáng)度開始的時(shí)候凍結(jié) /解凍測(cè) 試將決定其抵抗能力創(chuàng)建的靜水壓力由于凍結(jié) /解凍操作。純數(shù)據(jù)集之間的變化百分比是 17%,這不是預(yù)測(cè) ,通常作為再生骨料混凝土生產(chǎn)與原始骨料混凝土抗壓強(qiáng)度低于批處理 ,然而 ,骨料的不同類型 ,再生骨料的質(zhì)量和治療前配料占了這種差異。洗總批處理降低了罰款內(nèi)容之前 ,留下良好的聲音總有更高的抗壓強(qiáng)度。浸泡可以作為一個(gè)內(nèi)部蓄水池將協(xié)助固化過程和根據(jù) Shigematsu(Shigematsu et al .,2010)可能占這強(qiáng)度增加。之前的測(cè)試?yán)聿樯?et al。 (2009、 2010)幫助完善制造混凝土的過程中 ,一個(gè)令人滿意的 標(biāo)準(zhǔn) ,這是觀察在這個(gè)測(cè)試。 表 5 顯示了抗壓強(qiáng)度變化 ,基于對(duì)普通混凝土的抗壓強(qiáng)度批每集。減少-3.2 到 -24%強(qiáng)度反映了足量的空氣出現(xiàn)在每一個(gè)批次。 24%的價(jià)值也反映了再生骨料的可變性 ,用于制造的混凝土。 比較所有混凝土的抗壓強(qiáng)度值在表 6 給出測(cè)試 ,在 56 凍結(jié) /解凍周期。標(biāo)準(zhǔn)偏差低控制和凍結(jié) /解凍標(biāo)本。減少最大的優(yōu)點(diǎn)是觀察在維珍的素混凝土 (70%)。更少的力量減少觀察與再生骨料混凝土 (24%)。它也許這較高的初始強(qiáng)度提供了一些額外的凍結(jié) /解凍的保護(hù)。平原的空氣夾帶和聚丙烯纖維混凝土和再生骨料凍結(jié) /解凍條件下養(yǎng)護(hù) 的跡象在 56 個(gè)周期。顯示的纖維再生骨料混凝土強(qiáng)度降低 7%,然而 ,沒有可見明顯的剝落的混凝土 ,強(qiáng)度差異被認(rèn)為是由于配料公差。 4 結(jié)論 夾雜空氣的使用和聚丙烯纖維在混凝土與再生骨料顯示同樣有效提供凍結(jié) /解凍耐久性與混凝土相比由原始骨料夾雜空氣和聚丙烯纖維。 結(jié)果表明 ,混凝土立方體用再生骨料略更耐用比用原始骨料。數(shù)據(jù)集用再生骨料的聚丙烯纖維被發(fā)現(xiàn)有一個(gè)意思抗壓強(qiáng)度 13.8 N /平方毫米而立方體由維珍總與聚丙烯纖維平均抗壓強(qiáng)度 12.9 N /平方毫米的差異 7%,在正常配料公差。 用再生骨料混凝土立方體更耐用比普通 立方體由原始骨料 68%。這些數(shù)據(jù)可能被解釋為優(yōu)質(zhì)再生骨料的可變性和固化過程使用浸泡聚合。 總的來說 ,結(jié)果表明 ,再生骨料與添加劑的加入可以用于應(yīng)用程序的凍融混凝土發(fā)生同時(shí)仍然提供原始骨料的耐久性提供。這項(xiàng)工作應(yīng)該通知進(jìn)一步研究使用一個(gè)更大的數(shù)據(jù)集。 這項(xiàng)研究報(bào)告的結(jié)果 ,鼓勵(lì)利用清潔建筑廢物管理實(shí)現(xiàn)顯著的環(huán)境效益。建筑垃圾作為骨料替代避免天然骨料的開采產(chǎn)生的不利影響視覺的自然和生態(tài)方面環(huán)境。未能回收導(dǎo)致環(huán)境破壞的這種廢物通過不必要的土地填補(bǔ)處理。處理建筑廢料管理符合出來的精神及資源行動(dòng)計(jì)劃” (包裝 )在英國這是一 個(gè)政府機(jī)構(gòu)致力于重用和減少浪費(fèi)。使用我們的生命周期基礎(chǔ)設(shè)施作為物質(zhì)資源來產(chǎn)生新的發(fā)展是一個(gè)關(guān)鍵的元素提供一個(gè)可持續(xù)發(fā)展的社會(huì)。 外文原文 Freeze/thaw durability of concrete with recycled demolition aggregate comparedto virgin aggregate concrete Alan Richardson*, Kathryn Coventry, Jennifer Bacon School of the Built Environment at University of Northumbria, Newcastle upon Tyne, UK 1. Introduction In the UK the demand for aggregates for all uses is approximately 270 Mt/y, with 70 Mt of this demand coming from secondary and recycled aggregates (BRMCA, 2008). This test programmeinvestigated the freeze/thaw durability of concrete manufactured with both virgin and recycled aggregate. The range of concrete tested was; plain, air entrained and with Type 1 polypropylene fibres. The relative performance was then examined to highlight recycled aggregate performance with regard to durability. Polypropylene fibres and air entrainment have known freeze/thaw protection qualities when used in concrete (Richardson, 2003; Richardson and Wilkinson, 2009). Concrete manufactured using plain virgin aggregate normally has a higher compressive strength when compared to concrete made with recycled demolition waste aggregate (Richardson et al., 2009). Concrete is normally specified using compressive strength as amain indicator of suitability, however this may not be proportional with regard to aspects of durability. 1.1. Durability Durability is defined within the Concise Eurocode 2 (2006),stating,A durable structure shall meet the requirements of serviceability, strength and stability throughout its intended working life, without significant loss of utility or excessive maintenance (Narayan and Goodchild, 2006). The durability characteristics of CEM 1 (Portland cement) concrete with or without polypropylene fibre additions are significant to its sustainedWorld use as a dominant constructionmaterial. Consistent control in the manufacture of durable concrete is compromised by material supply limitations in terms of quantity and quality and this situation is particularly pertinent when working with recycled materials. A lack of published design and specification guides for recycled materials and their associated construction practices, perpetuates the reluctance to fully realise the potential of these materials in a variety of exposure conditions. Thus this paper aims to address the behaviour of concretes utilising recycled aggregates under severe exposure conditions which are defined for the purpose of this investigation as repetitive freeze/thaw cycles. 1.2. Materials The materials used in this study comprise virgin aggregates and angular crushed recycled demolition waste, and it is intended to use both types in the manufacture of concrete to compare their relative performance. For normal concrete, aggregates consist of sand, gravel and crushed stone and are vital elements in concrete. In order to provide a solid, strong and uncontaminated mix, aggregates must be free from clay coatings and any other elements that could cause the concrete to weaken (Sustainable Concrete, 2009). Recycled aggregates may have many deleterious materials within their make up and these can adversely affect the quality of the concrete.Section 1.2.1 considers the processing of these aggregates prior to use to limit this potential impact on the quality of concretes designed for this investigation. The findings are compared against mix designs adopting virgin aggregates which are specified in Section 1.2.2. Mixing is facilitated by the addition of water and the water chemistry is highlighted in Section 1.2.3 while Section 1.2.4 specifies the fibre adoption believed to afford freezeethaw protection (Richardson, 2003) and the chemical equivalent which is to be used within a comparative mix. Ultimately Section 1.2.5 illustrates the proposed mix designs to be adopted. 1.2.1. Recycled aggregates Previous research (Richardson et al., 2009) suggests that the use of recycled aggregates results in a reduction in compressive strength when compared with virgin aggregates. Meyer (2009) found that most reductions in strength for concrete made with recycled coarse aggregate were in the range of 5e24%, compared with concrete made with virgin aggregate. When both coarse and fine aggregate were obtained from recycled concrete, the strength reductions ranged from 15% to 40%, compared with concrete made with only naturally occurring materials. Zaharieva et al. (2004) found that the high absorption rate of recycled aggregate (RA) is the main barrier to their use in concrete manufacturing, as freshly mixed, recycled aggregate concrete (RAC) quickly loses its initial workability, even when super plasticizers are used. To prevent the suction of the mixing water by RA, it is necessary to pre-soak them. The porosity and absorption properties of concrete made using recycled aggregate are also difficult to accurately quantify as the high porosity of the recycled aggregates can mainly be attributed to the residue of mortar adhering to the original aggregate (BS EN 1097-6:2000, 2000). Porosity may provide a greater air void system that will produce a lower compressive strength and will aid the protection of the concrete from freeze/thaw damage. The angular crushed recycled aggregate was sieved and washed prior to use and the grading profile was similar to that of the virgin gravel with more intermediate aggregate being present. Seventy percent of the aggregatewas 8e20 mm red/blue broken brick of engineering quality and the remainder was crushed concrete of an unknown strength. The recycled aggregates used, were washed and soaked prior to batching and they were a direct replacement for the 1107 kg gravel component of the mix design. The cubes were labelled for ease of identification as shown in Table 3. 1.2.2. Virgin aggregates The aggregate as used in this test was rounded marine dredged and washed gravel, gap graded with a maximum aggregate size of 20 mm. The sand was washed prior to use and the grading profile is shown in Table 1 therefore the only aggregate replacement was the coarse aggregate. This aggregate replacement was defined by Zaharieva et al. (2004) as RAC1 which produced satisfactory results with regard to freeze/thaw durability. Table 2 shows the grading profile of the gravel, which is gap graded. The aggregate absorption for the natural gravel as used in this test was 1.4% determined with the use of a calcium carbide apparatus.This obtained value was the value that provided an aggregate ready for use in a saturated but surface dry condition as defined in BS EN 1097-6:2000 (2000). 1.2.3. Batching water The quality of the mixing water for production of concrete can influence the setting time, the strength development of concrete and the protection of reinforcement against corrosion. Potable water, described as water which is fit for human consumption is suitable to use according to BS EN 1008: 2002 (2002). Tap water supplied by Northumbrian Water (2010), was used in the design mix, which contained the following chemicals. Average of 78.750 mg/L dissolved sulphates. Sodium content in the water ranged between 13 and 17 mg/L(average of 15.5 mg/L) which when in the form of sodium sulphate can also be harmful in concrete (Darby et al., 2002). Chloride was also present in the water with an average of 14.75 mg/L. The percentage of chemicals present in the water, will not adversely affect the performance of the concrete with regard to freeze/thawperformance as thewater as used complied with BS EN 1008:2002, mixing water for concrete. 1.2.4. Polypropylene fibres and air entrainment (freeze/thaw protection) The 12 mm 35 micron Type 1 polypropylene fibres conforming to BS EN 14889:2006 (2006) were used at 0.9 kg/m3 dosage. The air-entraining agent was added at a dose of 50 mL per 100 kg of cement to achieve a minimum combined natural and added air void system of 4e7% in accordance with the manufacturers and Atkins (2010) recommendations. Triterpenoid saponin is the active ingredient and is supplied in liquid form for dispersal during batching. The benefit of using an air-entraining agent results from its ability to entrain, within the matrix of a concrete, numerous air voids which can relieve the stress due to the hydraulic pressure from the freezing water. The size of bubbles entrained, is significantly dependent on the entraining process used. The voids are not all the same size, and range usually from 0.05 to 1.25 mm (Palliere, 1994). 1.2.5. The concrete mix designs The mix design for the test was a C20 characteristic strength at 28 days, which is commonly used in house building in the UK. The component parts of the mix were: 240 kg CEM 1 cement, 731 kg coarse sand, 1107 kg 20 mm gravel or washed recycled demolition waste, 0.8 e water/cement ratio, 0.9 kg/m3 e polypropylene fibres (Type 1) and an air entrainment additive. 2. Methodology 2.1. Introduction The methodology developed for this investigation aims to compare the compressive strength of virgin aggregate concretes with concretes manufactured from recycled aggregates. Within these two grouped mix designs, sub-group mix designs would investigate the effects of polypropylene fibre and air-entrainment agent additions as a means of freeze/thaw protection provision on the compressive strength of the concrete and comparative testing of un-protected, plain concretes subjected to freezeethaw cycles would also be executed. To facilitate compression testing the concretes were formed into cubes (100 mm 100 mm 100 mm). The adoption of the size and shape of the concrete test samples was determined by consideration of the logistical demands of the manual nature of the laboratory work 100 mm cubes are lighter than concrete cubes of 150 mm. The smaller cube dimensions also produce a cube of larger surface area to volume ratio, thus ensuring severe test conditions. Table 3 illustrates the number of cubes produced relative to the various mix designs. 2.2. The cube production method To avoid the aggregates damaging the fibres, the fibres were added during the wet mixing period and mixed until evenly dispersed. The concretewas batched using a rotary drum mixer and checked for consistency using a slump test to BS EN 12350e2:2000 which recorded slump values of 10 mmfor the virgin plain concrete(VP) and 30 mm for the recycled plain (RP) concrete The difference in slump values for the same water cement ratio can be attributed to the use of saturated aggregate. After the slump test, the concrete was poured onto one tray and divided into 3 equal parts with one part returning to the initial mixing drum (to which the polypropylene fibres were added) one part was placed into a second drum (to which the chemical air-entrainment was added) whilst the third part was placed straight into the cube moulds to form the plain cubes. Where additions occurred, the drums were allowed further rotations to facilitate thorough dispersal through the concrete mixes. After one day curing in the moulds, the moulds were struck,and five days of curing occurred within a water bath prior to the concrete being subjected to freeze/thaw cycles and this ensured full saturation prior to starting the freeze/thaw test. Limited curing accelerated the freeze/thaw testing by ensuring low cube strength development coupled with the formation of an open capillary system (Basheer and Barbhuiya, 2010) due to the high water cement ratio adopted. This design ensured a recordable freeze/thaw response. The decision to use a lower strength concrete with a high w/c ratio was based on work by Jacobsen et al. (1996) as they claim that “zero or very little ice formation occurs in concretes with a w/c ratio of 0.4 and 0.35”. They also state, “one half or less of the absorbed water was freezeable to -20 and very little ice formation can initiate the process and result in major damage” . 2.3. The test program Three cubes of each of the six concrete mixes were used to determine the initial strength of concretes prior to any exposure to the freeze/thaw cycles. The freeze/thaw testing is based is based upon ASTM 666 (ASTMC 666), where weight loss is examined and the freezing is carried out at -18 in air and thawing is undertaken in water at 20 until the core temperature of the test cubes reached 6 . BS 15177:2006 was used to inform the duration of the test, which was limited to 56 cycles and two full freeze/thaw cycles were carried out