本文選題：石膏 + 磷酸�。� 參考：《長安大學》2017年碩士論文

【摘要】：作為一種古老的建筑材料,石膏具有環(huán)保、節(jié)能、質(zhì)輕、保溫、耐火、吸聲、尺寸穩(wěn)定等優(yōu)良性能。但是,石膏材料耐水性較差,這大大限制了它在各個領域的發(fā)展。為了解決石膏的耐水性問題,本文分析了導致石膏耐水性差的原因,總結了國內(nèi)外石膏的改性研究現(xiàn)狀。通過內(nèi)摻和外涂磷酸,從石膏的密度、吸水率、體積穩(wěn)定性、抗折強度、抗壓強度和軟化系數(shù)的角度,對其進行改性性能評價。實驗結果表明,單摻磷酸后石膏產(chǎn)生發(fā)泡和緩凝,這導致連通孔和塌�，F(xiàn)象。磷酸摻入后,由于發(fā)泡導致吸水率升高。摻量超過2%后,隨摻量的增加,吸水率降低。XRD和SEM分析發(fā)現(xiàn)加入磷酸后生成不溶于水的磷酸一氫鈣,這些物質(zhì)覆蓋在石膏晶體表面,導致石膏耐水性的提高。摻加PVA和二水石膏的實驗結果表明,加入PVA后穩(wěn)泡效果較好。加入二水石膏后初凝和終凝時間大大縮短。在磷酸摻量2%時,摻加PVA和二水石膏的效果最佳。與對比樣石膏相比,密度降低了14.3%,吸水率降低了12.8%,體積穩(wěn)定性提高了50%。但是強度較低,絕干抗折強度降低了75.3%,絕干抗壓強度降低了85.6%。復摻膨脹珍珠巖的實驗結果表明,膨脹珍珠巖可有效改善石膏的力學性能和軟化系數(shù)。膨脹珍珠巖最佳摻量為1.5%。與未摻膨脹珍珠巖的石膏相比,絕干抗折強度提高了46.9%,絕干抗壓強度提高了27.0%,抗折軟化系數(shù)提高了12.9%,抗壓軟化系數(shù)提高了3.0%。復摻麥秸稈纖維的實驗結果表明,最佳纖維摻量2.5%。絕干抗折強度較未摻麥秸稈纖維試樣提高了116.8%。絕干抗壓強度較未摻麥秸稈纖維試樣提高了183.9%。SEM測試發(fā)現(xiàn)麥秸稈纖維和石膏結合良好且PVA的加入可阻止麥秸稈纖維被酸腐蝕。外涂磷酸水溶液的實驗結果表明,磷酸與水的最佳稀釋倍數(shù)為1:4。耐水性改善效果較好,吸水率降低了8.5%,抗折軟化系數(shù)0.57,較空白石膏提高了54.1%,抗壓軟化系數(shù)0.52,較空白石膏提高了44.4%,抗折抗壓強度略有降低。最佳涂層厚度為四層。較空白石膏吸水率降低了9.3%,絕干抗折強度提高了4.9%,絕干抗壓強度提高了1.8%,抗折軟化系數(shù)提高了18.9%,抗壓軟化系數(shù)提高了25%。外涂磷酸后,SEM測試發(fā)現(xiàn),石膏表面覆蓋了一層物質(zhì)。與空白石膏相比,晶體與晶體間孔隙有所減少,結晶接觸點增多,晶體變得更加密實。
[Abstract]:As an ancient building material, gypsum has environmental protection, energy saving, light weight, heat preservation, fire resistance, sound absorption, size stability and other excellent properties. However, the water resistance of gypsum materials is poor, which greatly limits its development in various fields. In order to solve the problem of water resistance of gypsum, this paper analyzes the causes of poor water resistance of gypsum, and summarizes the research status of gypsum modification at home and abroad. The modification properties of gypsum were evaluated from the aspects of density, water absorption, volume stability, flexural strength, compressive strength and softening coefficient of gypsum. The experimental results show that the gypsum is foamed and retarded after the addition of phosphoric acid, which leads to the phenomenon of connected pores and collapsing modes. After incorporation of phosphoric acid, the water absorption rate increases due to foaming. The results of XRD and SEM analysis show that calcium monohydrogen phosphate, which is insoluble in water, is formed by adding phosphoric acid, which covers the surface of gypsum crystal and improves the water resistance of gypsum. The experimental results of adding PVA and gypsum dihydrate show that the foam stabilization effect is better after adding PVA. After adding gypsum dihydrate, the initial setting time and final setting time are greatly shortened. When the amount of phosphoric acid is 2, the effect of adding PVA and gypsum dihydrate is the best. Compared with the contrast gypsum, the density decreased by 14.3, the water absorption decreased by 12.8and the volume stability increased by 50. But the strength was lower, the dry strength and compressive strength decreased 75.3% and 85.6% respectively. The experimental results of mixed expanded perlite show that expanded perlite can effectively improve the mechanical properties and softening coefficient of gypsum. The optimum content of expanded perlite is 1.5. Compared with the gypsum without expanded perlite, the dry flexural strength, dry compressive strength, flexural softening coefficient and compressive softening coefficient are increased by 46.9, 27.0, 12.9and 3.0, respectively. The experimental results of mixed wheat straw fiber showed that the optimum fiber content was 2.5%. The dry flexural strength was 116.8% higher than that of the unadulterated wheat straw fiber. The compressive strength of wheat straw fiber was 183.9% higher than that of unadulterated wheat straw fiber. SEM test showed that wheat straw fiber combined well with gypsum and the addition of PVA could prevent wheat straw fiber from being corroded by acid. The experimental results show that the optimum dilution ratio of phosphoric acid and water is 1: 4. The water resistance is improved better, the water absorption is reduced by 8.5, the flexural softening coefficient is 0.57, compared with the blank gypsum, the bending softening coefficient is increased by 54.1, the compressive softening coefficient is 0.52, compared with the blank gypsum, the water absorption is increased by 44.4and the flexural strength is slightly reduced. The best coating thickness is four layers. Compared with the blank gypsum, the absorptivity of water was decreased by 9.3%, the dry bending strength was increased by 4.9%, the absolute dry compressive strength was increased by 1.8%, the flexural softening coefficient was increased by 18.9%, and the compressive softening coefficient was increased by 25%. SEM test showed that the gypsum surface was covered with a layer of substance. Compared with the blank gypsum, the porosity between crystal and crystal decreases, the crystal contact point increases, and the crystal becomes more dense.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ177.31

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本文編號：2007196