本文選題：輕骨料 + 預(yù)濕��； 參考：《長(zhǎng)沙理工大學(xué)》2014年碩士論文

【摘要】：輕骨料經(jīng)過(guò)預(yù)濕處理,會(huì)對(duì)新拌混凝土的工作性、硬化混凝土內(nèi)部結(jié)構(gòu)、力學(xué)及收縮性能等產(chǎn)生重要影響。本文選用三種不同種類(lèi)、不同吸水率的輕骨料,制備低塑性和高流態(tài)混合骨料混凝土。設(shè)計(jì)不同輕骨料取代率、水膠比水平以及多種養(yǎng)護(hù)條件,在大量試驗(yàn)的基礎(chǔ)上,研究經(jīng)過(guò)不同時(shí)間(干燥、預(yù)濕1h、預(yù)濕24h)浸水預(yù)濕處理的輕骨料對(duì)混合骨料混凝土工作性、力學(xué)性能、內(nèi)部相對(duì)濕度和收縮的影響,并探討其作用機(jī)理。主要工作及結(jié)論如下：1、分析不同輕骨料種類(lèi)及取代率條件下,干燥與預(yù)濕輕骨料分別對(duì)低塑性和高流態(tài)混合骨料混凝土工作性的影響。試驗(yàn)結(jié)果表明：干燥、預(yù)濕輕骨料對(duì)低塑性混凝土工作性影響較��；而高流態(tài)混凝土中,干燥輕骨料試樣經(jīng)時(shí)坍落度損失最大,預(yù)濕輕骨料有效抑制了混凝土的坍落度損失。三種不同吸水率的預(yù)濕輕骨料,預(yù)濕24h時(shí)高含水率的輕骨料比低含水率的輕骨料返水時(shí)間更早,對(duì)降低坍落度損失更明顯。2、分別采用高效減水劑和緩凝劑,輕骨料預(yù)濕過(guò)程中預(yù)先吸附外加劑與混凝土攪拌過(guò)程中直接摻入外加劑的對(duì)比,通過(guò)坍落度損失試驗(yàn)和凝結(jié)時(shí)間測(cè)定,分析多孔輕骨料對(duì)外加劑的“載體”和“緩釋”作用,并得出初步結(jié)論：直接摻入減水劑攪拌混凝土,液相中減水劑濃度下降快,流動(dòng)性保持能力差；輕骨料吸附的減水劑能緩慢地從其“載體”中釋放出來(lái),其液相中減水劑維持一定濃度,坍落度損失減��；輕骨料吸附緩凝劑使初、終凝時(shí)間間隔變長(zhǎng),輕骨料吸附緩凝劑同樣也能改善混凝土坍落度損失。3、系統(tǒng)研究干燥、預(yù)濕1h、預(yù)濕24h輕骨料對(duì)混合骨料混凝土強(qiáng)度發(fā)展的影響,并分析輕骨料吸水返水作用機(jī)理。隨著輕骨料預(yù)濕時(shí)間的延長(zhǎng),混凝土后期強(qiáng)度增長(zhǎng)率逐漸加大。對(duì)吸水率小的碎石型頁(yè)巖陶粒,干燥與預(yù)濕1h輕骨料對(duì)混凝土后期強(qiáng)度影響不大；對(duì)中等、高吸水率的輕骨料,預(yù)濕時(shí)間越久,混凝土后期強(qiáng)度增長(zhǎng)率相對(duì)越大,28d基本能趕上或超出干燥輕骨料試樣的強(qiáng)度。在凈水膠比、總水膠比和有效水膠比三個(gè)參數(shù)中,混合骨料混凝土的早期強(qiáng)度與凈水膠比相關(guān)性最大,后期強(qiáng)度與總水膠比相關(guān)性大,但無(wú)論早期、中期還是后期,混凝土強(qiáng)度總是取決于其有效水膠比。4、通過(guò)對(duì)比試驗(yàn),分析浸水養(yǎng)護(hù)、自然養(yǎng)護(hù)以及密封養(yǎng)護(hù)等不同外界養(yǎng)護(hù)條件下,預(yù)濕輕骨料在混凝土內(nèi)部返水作用與“內(nèi)養(yǎng)護(hù)”功能的發(fā)揮,總結(jié)不同外部溫濕度環(huán)境下“內(nèi)養(yǎng)護(hù)”混合骨料混凝土的抗壓強(qiáng)度發(fā)展規(guī)律。浸水養(yǎng)護(hù)時(shí),預(yù)濕輕骨料無(wú)“內(nèi)養(yǎng)護(hù)”效果；密封養(yǎng)護(hù)條件下預(yù)濕輕骨料改善水泥水化環(huán)境,“內(nèi)養(yǎng)護(hù)”與外養(yǎng)護(hù)結(jié)合,混凝土具有較高的強(qiáng)度；自然養(yǎng)護(hù)效果居中,且預(yù)濕輕骨料與干燥輕骨料試樣強(qiáng)度的差異隨輕骨料取代率的增加而減小。5、監(jiān)控混合骨料混凝土內(nèi)部相對(duì)濕度變化,分析輕骨料吸水返水特性、預(yù)濕輕骨料取代率等對(duì)混凝土內(nèi)部相對(duì)濕度的影響,以及混合骨料混凝土早期收縮發(fā)展規(guī)律。試驗(yàn)研究表明,輕骨料預(yù)濕后可以在混凝土內(nèi)部形成微型蓄水源,在濕度擴(kuò)散作用下釋放水分,改善混凝土內(nèi)部濕度環(huán)境。預(yù)濕輕骨料取代率越高,預(yù)濕時(shí)間越久,可供遷移的水分越多,混凝土內(nèi)部相對(duì)濕度降低越緩慢。預(yù)濕輕骨料對(duì)混凝土收縮的影響十分明顯,通過(guò)提高輕骨料預(yù)濕時(shí)間可降低混凝土的收縮率。6、從輕骨料的合理選用、預(yù)濕工藝、輕骨料對(duì)外加劑的作用、養(yǎng)護(hù)手段等方面對(duì)工程應(yīng)用中應(yīng)注意的關(guān)鍵問(wèn)題進(jìn)行初步討論和總結(jié),為其在實(shí)際工程中的生產(chǎn)和應(yīng)用提供了重要的參考。
[Abstract]:The effects of light aggregate on workability , mechanical property , internal relative humidity and shrinkage of mixed aggregate concrete with different kinds and different water absorption are studied . The effects of light aggregate on workability , mechanical property , internal relative humidity and shrinkage of mixed aggregate concrete have been studied . The main work and conclusion are as follows : 1 . To analyze the influence of different light aggregate types and substitution rates on workability , mechanical property , internal relative humidity and shrinkage of mixed aggregate concrete . The results show that the drying and pre - wetting lightweight aggregate have less influence on the workability of low plasticity concrete .
In the high - flow concrete , the loss of slump of the dry lightweight aggregate is the largest , and the pre - wet lightweight aggregate effectively inhibits the slump loss of the concrete . Compared with the lightweight aggregate with low water content during the pre - wet 24h , the light aggregate with high water content is more obvious than the light aggregate with low water content , and the effect of the porous light aggregate on the carrier and the slow release of the admixture is analyzed by the slump loss test and the setting time .
the water reducing agent adsorbed by the light aggregate can be slowly released from the carrier , the water reducing agent in the liquid phase is maintained at a certain concentration , and the slump loss is reduced ;
3 . The effect of drying , pre - wetting 1h and pre - wetting 24h light aggregate on the strength development of mixed aggregate concrete can be improved .
In the light aggregate with medium and high water absorption , the longer the pre - wetting time , the higher the later strength growth rate of the concrete , the 28d is basically able to catch up with or exceed the strength of the dry lightweight aggregate specimen . In the water - purifying ratio , the total water - cement ratio and the effective water - cement ratio , the concrete strength always depends on its effective water - cement ratio .
the pre - wet light aggregate under the condition of sealing and curing can improve the hydration environment of the cement , the internal curing is combined with the outer curing , and the concrete has higher strength ;
The effect of pre - wetting time of lightweight aggregate on the internal relative humidity of concrete is analyzed . The effect of pre - wetting lightweight aggregate on concrete shrinkage can be reduced . The effect of pre - wetting lightweight aggregate on shrinkage of concrete is obvious .
【學(xué)位授予單位】：長(zhǎng)沙理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TU528
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本文編號(hào)：1934040