【摘要】：α-半水石膏是重要的膠凝材料,因其優(yōu)良的性能廣泛應(yīng)用于建材、醫(yī)學(xué)、模具等領(lǐng)域。常壓鹽溶液法制備α-半水石膏,反應(yīng)條件溫和、產(chǎn)品穩(wěn)定,是最具前景的制備技術(shù)。其中,反應(yīng)介質(zhì)是常壓鹽溶液法最為重要的影響因素之一。本文研究了常壓溫和條件下Ca(NO3)2水溶液中脫硫石膏制備α-半水石膏的工藝,重點研究了K2SO4對脫硫石膏脫水過程、α-半水石膏形貌的影響以及不同條件下得到的產(chǎn)物的水化強度。為實現(xiàn)脫硫石膏制備α-半水石膏,常用的結(jié)晶介質(zhì)體系為CaCl2水溶液,但是氯根會導(dǎo)致材料腐蝕等問題。本實驗以Ca(NO3)2取代CaCl2,在95℃及常壓條件下,實現(xiàn)脫硫石膏順利轉(zhuǎn)化為α-半水石膏,形成了新的脫硫石膏制備a-半水石膏的工藝。通過不同K2SO4濃度對脫硫石膏脫水過程、α-半水石膏形貌的研究,結(jié)果表明,K2SO4濃度由0 mM增加至87.50 mM,脫硫石膏的完全轉(zhuǎn)化時間逐漸縮短,由11h縮短至3h。其中對α-半水石膏的誘導(dǎo)成核時間影響比對晶體生長時間影響更為顯著。K2SO4對脫硫石膏轉(zhuǎn)化速率的影響是K+和SO42-的共同作用,其中SO42-對轉(zhuǎn)化速率的促進作用大于K+。K2SO4還對α-半水石膏晶體粒徑有十分顯著的影響,隨著K2SO4濃度由0 mM增加到87.50 mM,晶體長度由354.28μm減小為55.11μm,直徑由48.88μm減小至10.81μm,長徑比由7.25降低至5.10。a-半水石膏最重要的性能是其膠凝體的強度。α-半水石膏的水化過程遵循“溶解-析晶”原理,在水化過程中形成交織連生的二水石膏膠凝體。當(dāng)K2S04濃度從0mM增加到87.50 mM,α-半水石膏的膠凝體2h抗折強度、抗壓強度分別由5.62 MPa降低至2.47 MPa,11.20 MPa降低至4.10 MPa；絕干抗折強度、抗壓強度分別由9.63 MPa降低至5.72 MPa,22.90 MPa降低至16.83 MPa。α-半水石膏水化后的二水石膏晶體粒徑增大,晶體形貌由板狀、薄片狀向針柱狀轉(zhuǎn)變,晶體間的相互搭接較為疏松,增加了膠凝體的孔徑,使得膠凝體的結(jié)構(gòu)趨于疏松,導(dǎo)致其強度降低。研究表明,95℃及常壓條件下,脫硫石膏在Ca(NO3)2溶液中快速轉(zhuǎn)化為α-半水石膏,并且a-半水石膏水化后能夠得到強度較高的膠凝體,形成了新的制備工藝。通過添加K2S04調(diào)節(jié)脫硫石膏脫水轉(zhuǎn)化為α-半水石膏的速率、控制α-半水石膏晶體形貌,從而影響膠凝體性能。
[Abstract]:偽-hemihydrate gypsum is an important cementitious material, because of its excellent properties, it is widely used in the fields of building materials, medicine, mould and so on. The preparation of 偽-hemihydrate gypsum by salt solution under normal pressure is the most promising preparation technology with mild reaction conditions and stable products. Among them, the reaction medium is one of the most important influencing factors in the method of salt solution under atmospheric pressure. The preparation of 偽 -hemihydrate gypsum from desulfurized gypsum in Ca (no _ 3) _ 2 aqueous solution under normal pressure and temperature was studied in this paper. The effect of K _ 2SO _ 4 on the dehydration process, the morphology of 偽 -hemihydrate gypsum and the hydration strength of the product obtained under different conditions were studied. In order to prepare 偽 -hemihydrate gypsum from desulphurized gypsum, CaCl _ 2 aqueous solution is commonly used as crystallization medium, but chloride can lead to material corrosion and so on. In this experiment, Ca (no _ 3) _ 2 was used to replace CaCl _ 2. Under the condition of 95 鈩，

本文編號：2129557