本文選題：輕骨料 + 預濕　； 參考：《長沙理工大學》2014年碩士論文

【摘要】：輕骨料經過預濕處理,會對新拌混凝土的工作性、硬化混凝土內部結構、力學及收縮性能等產生重要影響。本文選用三種不同種類、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。設計不同輕骨料取代率、水膠比水平以及多種養(yǎng)護條件,在大量試驗的基礎上,研究經過不同時間(干燥、預濕1h、預濕24h)浸水預濕處理的輕骨料對混合骨料混凝土工作性、力學性能、內部相對濕度和收縮的影響,并探討其作用機理。主要工作及結論如下：1、分析不同輕骨料種類及取代率條件下,干燥與預濕輕骨料分別對低塑性和高流態(tài)混合骨料混凝土工作性的影響。試驗結果表明：干燥、預濕輕骨料對低塑性混凝土工作性影響較��；而高流態(tài)混凝土中,干燥輕骨料試樣經時坍落度損失最大,預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濕輕骨料,預濕24h時高含水率的輕骨料比低含水率的輕骨料返水時間更早,對降低坍落度損失更明顯。2、分別采用高效減水劑和緩凝劑,輕骨料預濕過程中預先吸附外加劑與混凝土攪拌過程中直接摻入外加劑的對比,通過坍落度損失試驗和凝結時間測定,分析多孔輕骨料對外加劑的“載體”和“緩釋”作用,并得出初步結論：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,其液相中減水劑維持一定濃度,坍落度損失減小；輕骨料吸附緩凝劑使初、終凝時間間隔變長,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、預濕1h、預濕24h輕骨料對混合骨料混凝土強度發(fā)展的影響,并分析輕骨料吸水返水作用機理。隨著輕骨料預濕時間的延長,混凝土后期強度增長率逐漸加大。對吸水率小的碎石型頁巖陶粒,干燥與預濕1h輕骨料對混凝土后期強度影響不大；對中等、高吸水率的輕骨料,預濕時間越久,混凝土后期強度增長率相對越大,28d基本能趕上或超出干燥輕骨料試樣的強度。在凈水膠比、總水膠比和有效水膠比三個參數(shù)中,混合骨料混凝土的早期強度與凈水膠比相關性最大,后期強度與總水膠比相關性大,但無論早期、中期還是后期,混凝土強度總是取決于其有效水膠比。4、通過對比試驗,分析浸水養(yǎng)護、自然養(yǎng)護以及密封養(yǎng)護等不同外界養(yǎng)護條件下,預濕輕骨料在混凝土內部返水作用與“內養(yǎng)護”功能的發(fā)揮,總結不同外部溫濕度環(huán)境下“內養(yǎng)護”混合骨料混凝土的抗壓強度發(fā)展規(guī)律。浸水養(yǎng)護時,預濕輕骨料無“內養(yǎng)護”效果；密封養(yǎng)護條件下預濕輕骨料改善水泥水化環(huán)境,“內養(yǎng)護”與外養(yǎng)護結合,混凝土具有較高的強度；自然養(yǎng)護效果居中,且預濕輕骨料與干燥輕骨料試樣強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部相對濕度變化,分析輕骨料吸水返水特性、預濕輕骨料取代率等對混凝土內部相對濕度的影響,以及混合骨料混凝土早期收縮發(fā)展規(guī)律。試驗研究表明,輕骨料預濕后可以在混凝土內部形成微型蓄水源,在濕度擴散作用下釋放水分,改善混凝土內部濕度環(huán)境。預濕輕骨料取代率越高,預濕時間越久,可供遷移的水分越多,混凝土內部相對濕度降低越緩慢。預濕輕骨料對混凝土收縮的影響十分明顯,通過提高輕骨料預濕時間可降低混凝土的收縮率。6、從輕骨料的合理選用、預濕工藝、輕骨料對外加劑的作用、養(yǎng)護手段等方面對工程應用中應注意的關鍵問題進行初步討論和總結,為其在實際工程中的生產和應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 .
【學位授予單位】：長沙理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU528
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本文編號：1934040