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        基于正交試驗的免蒸壓加氣混凝土的制備與性能優(yōu)化

        2024-11-27 00:00:00劉小薈彭曉彤汪洪偉李維海王鵬
        中國粉體技術(shù) 2024年6期

        摘要:【目的】制備輕質(zhì)高強、節(jié)能保溫的免蒸壓加氣混凝土,尋找最優(yōu)制備配合比,提高固體廢棄物的利用率?!痉椒ā炕谡辉囼灢捎脴O差分析和矩陣關(guān)聯(lián)分析的方法確定免蒸壓加氣混凝土的基礎(chǔ)最優(yōu)配比,優(yōu)化玻璃粉的摻入量來實現(xiàn)加氣混凝土性能的提升?!窘Y(jié)果】各因素對免蒸壓加氣混凝土的表觀干密度和抗壓強度的影響程度由大到小為鋁粉摻量(質(zhì)量分數(shù),下同)、水泥摻量、水料比、聚丙烯纖維(PP纖維)摻量,加氣混凝土的基礎(chǔ)最優(yōu)配比為水泥摻量為24%,水料比為0. 44,鋁粉摻量為0. 13%,PP纖維摻量為0. 4%;當玻璃粉質(zhì)量替代率達到25%時,混凝土的綜合性能達到最優(yōu)?!窘Y(jié)論】玻璃粉作為粉煤灰的替代材料,在改善免蒸壓加氣混凝土干密度、抗壓強度、導(dǎo)熱系數(shù)方面效果顯著。

        關(guān)鍵詞:免蒸壓加氣混凝土;玻璃粉;干密度;抗壓強度;導(dǎo)熱系數(shù);正交試驗

        中圖分類號:TU528;TB4文獻標志碼:A

        引用格式:

        劉小薈,彭曉彤,汪洪偉,等. 基于正交試驗的免蒸壓加氣混凝土的制備與性能優(yōu)化[J]. 中國粉體技術(shù),2024,30(6):74-84.

        LIU Xiaohui,PENG Xiaotong,WANG Hongwei,et al. Preparation and performance optimization of non-autoclaved aerated con?crete based on orthogonal tests[J]. China Powder Science and Technology,2024,30(6):74?84.

        隨著我國城市化進程的不斷加快,建筑業(yè)能耗問題日益突出。目前廣泛用于建筑墻體材料的蒸壓加氣混凝土在生產(chǎn)過程中能耗大,設(shè)備昂貴,與國家提倡的低碳節(jié)能目標相悖,其熱工性能與高效保溫材料相比仍有差距,為滿足現(xiàn)階段居住建筑節(jié)能率達到82.5%的要求,只能通過增加墻板厚度來實現(xiàn),因此開發(fā)能耗低、保溫效果好的免蒸壓加氣混凝土成為目前綠色建材一個重要研發(fā)方向[1-2]。

        許多固體廢棄物(如赤泥、稻殼灰、尾礦等)常被用來制備加氣混凝土[3-5]。廢玻璃作為一種難以降解的固體廢棄物常被當作垃圾丟棄,不僅占據(jù)大量土地,更會帶來嚴重的環(huán)境污染[6-7]。李卓才等[8]、Lu等[9]、Sun等[10]學者的研究表明,玻璃粉的化學組分與粉煤灰相似,在一定粒徑時具有優(yōu)良的火山灰活性。此外,廢玻璃導(dǎo)熱系數(shù)小,SiO2含量高[11],國內(nèi)外已有許多學者將玻璃粉應(yīng)用到水泥基材料中進行了研究[12-15],發(fā)現(xiàn)玻璃粉有提高混凝土力學性能和耐久性的潛力。Nasry等[16]、Boukhelf等[17]的研究則進一步表明,適當摻入玻璃粉有利于減小混凝土的導(dǎo)熱系數(shù)。以上研究表明,適量摻入玻璃粉不僅可以改善混凝土的物理和力學性能,還有利于提高混凝土的保溫性能,但目前對于玻璃粉在加氣混凝土

        中的應(yīng)用研究較少[18-19]。

        本文中采用免蒸壓工藝制備加氣混凝土,設(shè)計四因素四水平正交試驗研究主要影響因素對免蒸壓加氣混凝土性能的影響,并摻入玻璃粉優(yōu)化加氣混凝土的力學、保溫性能,研究了玻璃粉摻量對免蒸壓加氣混凝土的表觀干密度、抗壓強度、導(dǎo)熱系數(shù)的影響。本研究中既避免了傳統(tǒng)加氣混凝土制備過程中高溫高壓的能量消耗和設(shè)備投資,又解決了廢玻璃降解困難、污染環(huán)境等問題,是免蒸壓加氣混凝土在節(jié)能墻板中應(yīng)用的有益嘗試。

        1試驗

        1.1材料與設(shè)備

        原材料:水泥(P·O42.5硅酸鹽水泥,濟南市圣偉建材公司);石灰(粒徑小于74 μm,建德市新安江永合塑膠廠);石膏(濟南市區(qū)瑞豐裝飾公司);二級粉煤灰(龍澤環(huán)??萍脊荆话l(fā)泡劑(GLS-65鋁粉膏,粒徑小于74 μm,水劑型,有效成分含量(質(zhì)量分數(shù),下同)為98%,活性含量高達99%,淮安市佳億建材有限公司);聚丙烯纖維(PP纖維,型號為PP-6,上海臣啟化工科技有限公司);外加劑;玻璃粉(粒徑小于74 μm,河北卓飛礦產(chǎn)品有限公司)。外加劑包括羥丙基甲基纖維素(穩(wěn)泡劑,晉州市寶藝建材科技有限公司)、無水硫酸鈉(無機早強劑,天津市致遠化學試劑有限公司)、三乙醇胺(有機早強劑,河南化工原料總行)。水泥、粉煤灰、玻璃粉和硅灰的主要化學組分如表1所示。

        儀器設(shè)備:SHT4605型水泥膠砂攪拌機、微機控制電液伺服萬能試驗機(美國美特斯工業(yè)系統(tǒng)有限公司);NJW-HW型混凝土標準養(yǎng)護系統(tǒng)(北京耐恒檢測設(shè)備科技發(fā)展公司);DRPL-Ⅱ型導(dǎo)熱系數(shù)測試儀(湘潭湘儀儀器有限公司);101-3型數(shù)顯恒溫鼓風干燥箱(河北雙鑫試驗儀器制造有限公司)。

        1.2試件制備與測試

        依據(jù)GB/T 11969—2020《蒸壓加氣混凝土性能試驗方法》,制作邊長為10 cm的正方體試件用于干密度和立方體抗壓強度測試。參照GB/T 10295—2008《絕熱材料穩(wěn)態(tài)熱阻及有關(guān)特性的測定熱流計法》制作長度、寬度、高度分別為30、30、3 cm的長方體試件用于導(dǎo)熱系數(shù)測試,試件制備流程如圖1所示。每層的裝料厚度大致相等,覆膜養(yǎng)護24 h后脫模,制得試件如圖2所示,然后將試件置于標準養(yǎng)護室繼續(xù)養(yǎng)護至相應(yīng)測試齡期。

        每種試件的測試均進行3組重復(fù)試驗,取平均值作為最終結(jié)果。在進行抗壓強度測試時,需確保受壓方向垂直于制品的發(fā)氣方向,施加載荷的速度應(yīng)控制在(2.0±0.5)kN/s,并持續(xù)加載直至試件破壞。導(dǎo)熱系數(shù)測試時,將試件放在測試儀的加熱板上,并用冷板壓緊,輸入樣品厚度為300 mm,設(shè)置冷熱板的溫差大于20℃但不超過50℃,測試完成后記錄數(shù)據(jù)。其中,在測試干密度和導(dǎo)熱系數(shù)之前,須要對試件進行干燥處理。首先,將試件放入電熱鼓風干燥箱,在(60±5)℃下保持24 h,然后在(80±5)℃下繼續(xù)保持24 h,最后在(105±5)℃下烘至恒質(zhì)狀態(tài),即間隔4 h前后2次質(zhì)量差應(yīng)≤2 g。

        2基礎(chǔ)配合比

        經(jīng)大量試驗比較,選取水泥摻量(質(zhì)量分數(shù),下同)、鋁粉摻量、PP纖維摻量、水料比4項因素,以表觀干密度和14 d齡期抗壓強度作為基礎(chǔ)指標設(shè)計L16(44)正交試驗方案,正交試驗因素水平如表2所示,研究4項因素對免蒸壓加氣混凝土性能的影響。試驗中水泥、石灰、石膏和粉煤灰為干粉料,前期試驗確定水泥和石灰的總質(zhì)量固定為干粉料總質(zhì)量的39%。粉煤灰、穩(wěn)泡劑、無機早強劑、有機早強劑的摻量分別固定為干粉料總質(zhì)量的58%、0. 1%、0.5%、0.03%。

        2.1試驗結(jié)果分析

        以表觀干密度和14 d齡期抗壓強度為衡量指標,得到正交試驗結(jié)果及極差分析分別見表3、4。

        根據(jù)表3的試驗結(jié)果,可得到各因素對免蒸壓加氣混凝土基礎(chǔ)指標的影響如圖3所示。由圖3可得,在研究加氣混凝土的干密度時,各因素對其影響程度由大到小依次為鋁粉摻量、水泥摻量、水料比、PP纖維摻量。隨著水泥摻量的增加,干密度先增加后減?。浑S水料比和PP纖維摻量的增加,干密度小幅波動,但整體呈上升趨勢;而鋁粉摻量的增加則會導(dǎo)致干密度減小。加氣混凝土以輕質(zhì)為優(yōu),故取各因素下干密度最小的水平組得到加氣混凝土干密度的最優(yōu)組合為A1B3C4D1(表3),即水泥摻量24%,水料比0.48,鋁粉摻量0.22%,PP纖維摻量0.2%。

        由圖3可得,各因素對加氣混凝土14 d抗壓強度的影響程度由大到小依次為鋁粉摻量、水泥摻量、水料比、PP纖維摻量。隨著水泥摻量的增加,抗壓強度先增加后減小;隨水料比的增加,抗壓強度則先減小后增大;PP纖維摻量的增加有利于抗壓強度的提高;而鋁粉摻量的增加則對抗壓強度有不利影響。為了提高加氣混凝土的強度,取各因素下抗壓強度最大的水平組得到加氣混凝土抗壓強度的最優(yōu)組合為A2B1C1D4(表3),即水泥摻量26%,水料比0.44,鋁粉摻量0. 13%,PP纖維摻量0.5%。

        2.2矩陣關(guān)聯(lián)分析

        單一指標不能反映免蒸壓加氣混凝土的綜合性能,為了保證分析結(jié)果的準確性,可以采用矩陣關(guān)聯(lián)分析來確定綜合評價指標,從而確定本試驗所需的基礎(chǔ)最優(yōu)配比。根據(jù)四因素四水平正交試驗及極差分析(表5)分別建立指標層矩陣M、因素層矩陣T和水平層矩陣S,如式(1)—(3)所示。

        式中:強度指數(shù)為正向指標,取Kij=kij;干密度指數(shù)為負向指標,取Kij=1/kij。

        確定各個評價指標的權(quán)重矩陣為:

        W=M?T?S。(4)

        由各指標權(quán)重矩陣取平均值得到綜合權(quán)重矩陣:

        (5)

        式中:W1、W2分別為干密度和抗壓強度的權(quán)重矩陣。通過計算,得到正交試驗的矩陣分析計算結(jié)果如表5所示。

        2.2.1影響因素分析

        影響權(quán)重是反映該因素對性能影響程度的大小。對于同一因素的不同水平來說,影響權(quán)重越大,意味著該水平對應(yīng)的干密度越小,抗壓強度越大。如圖4、5所示,各因素對加氣混凝土基礎(chǔ)指標的影響程度次序與極差分析的結(jié)果一致。在諸多因素中,鋁粉摻量對免蒸壓加氣混凝土的基礎(chǔ)指標影響最為顯著,隨著鋁粉摻量的增加,混凝土的干密度和抗壓強度逐漸減小。這是由于鋁粉在發(fā)氣過程中產(chǎn)生氫氣,導(dǎo)致混凝土內(nèi)部氣泡增多[20],從而降低干密度,同時氣泡的增加會使集料間的黏結(jié)強度減小,導(dǎo)致抗壓強度下降。

        水泥摻量對干密度和抗壓強度的影響次之。隨著水泥摻量的增加,免蒸壓加氣混凝土的干密度和抗壓強度先增大后減小。這是因為在一定范圍內(nèi)增加水泥用量有助于填充混凝土內(nèi)部孔隙,增加密實度,同時增強混凝土內(nèi)部的膠凝作用,這有利于混凝土強度的提升,但過多的水泥摻量會導(dǎo)致混凝土過度硬化和收縮,進而對抗壓強度產(chǎn)生不利影響。

        水料比和PP纖維摻量的增加對加氣混凝土干密度的影響不顯著,但對抗壓強度影響較為明顯。加氣混凝土的抗壓強度隨著水料比的增加先降低后提高。這是因為適當增加水料比可以使膠凝材料充分水化,增強集料間的黏結(jié)力,進而提高抗壓強度。然而,當水料比過大時,基體內(nèi)部的自由水增加,使?jié){體變得稀薄,導(dǎo)致集料間的黏結(jié)力減弱,從而使抗壓強度下降。PP纖維的摻入則有助于提高混凝土的延性和韌性,并能夠抑制裂縫的發(fā)展。隨著PP纖維摻量的增加,基體內(nèi)部形成良好的三維網(wǎng)絡(luò)結(jié)構(gòu),有效地抵抗裂縫擴展[21],從而提高整體的抗壓性能。

        2.2.2最優(yōu)配合比

        由各指標權(quán)重矩陣取平均值得到各影響因素的不同水平對加氣混凝土多指標的綜合影響權(quán)重如圖6所示。由圖可知,加氣混凝土多指標的綜合權(quán)重由大到小依次為鋁粉摻量、水泥摻量、水料比、PP纖維摻量,取各影響因素下綜合權(quán)重最大的水平組,得到加氣混凝土的基礎(chǔ)最優(yōu)配合比為A1B1C1D3(見表4),即水泥摻量24%,水料比0.44,鋁粉摻量0. 13%,PP纖維摻量0.4%。

        3玻璃粉摻量的影響

        為了進一步提升免蒸壓加氣混凝土的性能,同時提高固體廢棄物的利用率,基于加氣混凝土的基礎(chǔ)最優(yōu)配合比,分別設(shè)計了玻璃粉替代粉煤灰0、15%、20%、25%、30%共5組試驗,以干密度、28 d齡期抗壓強度和導(dǎo)熱系數(shù)為衡量指標研究玻璃粉替代率對加氣混凝土的影響,試驗結(jié)果見圖7所示。

        3.1干密度和抗壓強度

        圖7的試驗結(jié)果顯示,當玻璃粉替代率從0增至30%時,加氣混凝土的干密度和抗壓強度逐漸增大。在水料比不變的情況下,當玻璃粉替代率增加時,玻璃粉的特殊形狀增加了顆粒間的摩擦力,增加漿體的剪切力,并降低其流動性,使得鋁粉的發(fā)氣受到一定阻礙,導(dǎo)致孔隙率減小,從而提高了加氣混凝土的干密度和抗壓強度。此外,玻璃粉與水泥水化產(chǎn)生的氫氧化鈣發(fā)生火山灰效應(yīng),形成的水化硅酸鈣(C-S-H)凝膠填充了加氣混凝土的孔隙,導(dǎo)致加氣混凝土的干密度和抗壓強度增加[19],當替代率達到25%之后,材料的填充效果逐漸飽和,混凝土的抗壓強度不再增加。

        3.2導(dǎo)熱系數(shù)

        由圖7可得,當玻璃粉替代15%、20%、25%、30%粉煤灰時,各試樣的導(dǎo)熱系數(shù)較基準組(替代率為0)分別降低了18.58%、19.47%、23.79%、19. 19%。隨著玻璃粉替代率的增加,免蒸壓加氣混凝土的導(dǎo)熱系數(shù)先減小后增大。當玻璃粉替代率達到25%時,混凝土的導(dǎo)熱系數(shù)最小。

        玻璃粉的導(dǎo)熱系數(shù)小于粉煤灰的,但大于混凝土孔隙內(nèi)空氣的導(dǎo)熱系數(shù),適量摻入玻璃粉有助于使加氣混凝土的導(dǎo)熱系數(shù)減小,但過量的玻璃粉會使料漿的流動性變差,導(dǎo)致鋁粉發(fā)氣受阻甚至出現(xiàn)局部憋氣現(xiàn)象,破壞漿體內(nèi)部空隙結(jié)構(gòu),導(dǎo)致導(dǎo)熱系數(shù)增大。

        3.3綜合性能對比分析

        當玻璃粉替代25%粉煤灰時,免蒸壓加氣混凝土的導(dǎo)熱系數(shù)最小,抗壓強度最高,并且干密度也在標準范圍之內(nèi)。將本文中所研究的免蒸壓加氣混凝土與GB/T 11968—2020《蒸壓加氣混凝土砌塊》中要求的性能、文獻[22]制備的混凝土性能進行對比分析,結(jié)果如表6所示。由表可知,自制的免蒸壓加氣混凝土在相同干密度等級下的導(dǎo)熱系數(shù)小于文獻[22]和國標要求的,但對應(yīng)的抗壓強度僅2.6 MPa,不能滿足要求。還需要進一步研究提升其強度使其達到規(guī)范要求。

        4結(jié)論

        本文中通過正交試驗,采用極差分析和矩陣關(guān)聯(lián)分析的方法研究了不同因素摻量對免蒸壓加氣混凝土干密度和抗壓強度的影響,并進一步探討了玻璃粉替代粉煤灰對免蒸壓加氣混凝土性能的影響。

        1)各因素對免蒸壓加氣混凝土干密度和抗壓強度影響程度由大到小依次為鋁粉摻量、水泥摻量、水料比、PP纖維摻量,且與矩陣關(guān)聯(lián)分析得到的各因素影響程度一致。

        2)加氣混凝土的基礎(chǔ)最優(yōu)配合比為水泥摻量為24%,水料比為0.44,鋁粉摻量為0. 13%,PP纖維摻量為0.4%。

        3)玻璃粉在一定范圍內(nèi)可以使加氣混凝土的導(dǎo)熱系數(shù)減小并提高其強度。當玻璃粉替代率達到25%時,加氣混凝土的基本性能達到最優(yōu),干密度、抗壓強度和導(dǎo)熱系數(shù)分別592 kg/m3、2.6 MPa、0.07194 W/(m·K)。

        4)制備的免蒸壓加氣混凝土保溫性能優(yōu)異,導(dǎo)熱系數(shù)遠小于國標要求,但強度不高,還有待通過后續(xù)的研究提升其強度。

        利益沖突聲明(Conflict of Interests)

        所有作者聲明不存在利益沖突。

        All authors disclose no relevant conflict of interests.

        作者貢獻(Authors’Contributions)

        劉小薈和彭曉彤進行了方案設(shè)計,劉小薈、彭曉彤、汪洪偉、李維海、王鵬參與了論文的寫作和修改。所有作者均閱讀并同意了最終稿件的提交。

        The study was designed by LIU Xiaohui and PENG Xiaotong. The manuscript was written and revised by LIU Xiaohui,PENG Xiaotong,WANG Hongwei,LI Weihai,and WANG Peng. All authors have read the final version of the paper and consented to its submission.

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        Preparation and performance optimization of non-autoclaved aerated concrete based on orthogonal tests

        LIU Xiaohui1,PENG Xiaotong1,WANG Hongwei2,LI Weihai2,WANG Peng1

        1. School of Civil Engineering and Architecture,University of Jinan,Jinan 250022,China;

        2. China Railway Tenth Bureau Group Co. ,Ltd. ,Yantai 264001,China

        Abstract

        ObjectiveWith the rapid progress of urbanization,energy consumption in the construction industry has become increasingly con?cerning. Traditional autoclaved aerated concrete,though widely used,requires high energy during production,conflicting with low-carbon and energy-saving goals. Thus,developing non-autoclaved aerated concrete with low energy consumption and good thermal insulation is akey research direction. This study also seeks to enhance the use of solid waste,particularly waste glass powder. Waste glass,difficult to degrade,poses environmental risks if improperly handled. Incorporating waste glass powder in non-autoclaved aerated concrete not only mitigates environmental pollution but also improves its properties,such as lowering thermal conductivity and increasing compressive strength. This approach aligns with sustainability goals and promotes waste recycling. Theresearchultimatelyaimstopreparelightweight,high-strength,energy-efficient,andheat-insulatingnon-autoclaved aerated concrete,contributing to low-carbon,eco-friendly construction.

        MethodsIn this study,orthogonal tests were conducted with two analysis approaches:range analysis and matrix correlation analysis. First,taking dry density and compressive strength as performance indicators,a L16(44)orthogonal experiment was designed examining four factors:cement content,aluminum powder content,polypropylene(PP)fiber content,and water-material ratio. Then,range analysis method was used to determine the influence of each factor on the performance of aerated con?crete. Matrix analysis was applied to calculate the comprehensive weight of different levels of each influencing factor on multiple performance indicators to determine the optimal ratio for non-autoclaved aerated concrete. In addition,different amounts of glass powder(15%,20%,25%,and 30%)were used to replace fly ash,and their effects on performance indicators such as dry density,compressive strength,and thermal conductivity were investigated.

        Results and DiscussionAluminum powder had the most significant impact on the dry density and compressive strength of non-autoclavedaerated concrete. With the increase in aluminum powder content,more bubbles formed in the concrete during the gas generation process,weakening the bonding strength between aggregates. As aresult,it led to agradual decrease in dry density and compressive strength. Cement content was identified as the second most influential factor:with the increase in cement con?tent,the compressive strength increased initially but then decreased. This occurred because acertain increase in cement would promote aggregate reaction to generate more hydration products,thereby improving the compressive strength of aerated concrete. However,excessive cement content resulted in excessive hardening and shrinkage,negatively affecting compressive strength. The increase in water-material ratio and PP fiber content showed minimal impact on dry density,with aslight influence on com?pressive strength. The optimal mix ratio of the foundation was determined to be 24%cement content,a 0. 44 water-material ratio,0. 13%aluminum powder content,and 0. 4%PP fiber content. The introduction of glass powder as asubstitute for fly ash reduced the thermal conductivity and improved the strength of aerated concrete. At areplacement rate of 25%,the basic proper?ties of aerated concrete were optimal,with adry density of 592 kg/m3,a compressive strength of 2. 6 MPa,and athermal con?ductivity of 0. 07194 W/(m·K).

        ConclusionThis study shows that aluminum powder,cement,water-to-material ratio,and PP fiber have varying impacts on the dry density and compressive strength of non-autoclaved aerated concrete,with aluminum powder having the most notable effect. Incorporatingglasspowderasa flyashsubstitutesignificantlyenhancesboththermalconductivityandcompressive strength. The optimal material performance is achieved when the substitution rate of glass powder reaches 25%. While the ther?mal insulation of the prepared non-autoclaved aerated concrete exceeds current national standards,its compressive strength remains relatively low and requires further optimization. Overall,the study underscores the potential of non-autoclaved aerated concreteforenergyefficiency,environmentalsustainability,andmaterialperformanceimprovements. However,additional research is necessary to address the compressive strength limitations for practical engineering applications.

        Keywords:non-autoclaved aerated concrete;glass powder;dry density;compressive strength;thermal conductivity;orthogo?nal test

        (責任編輯:王雅靜)

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