【作者】 王冠；

【导师】 王文龙；

【作者基本信息】 山东大学 ， 动力工程（专业学位）， 2021， 硕士

【摘要】 随着我国工业化建设进程加快,人民的生活质量得到提高的同时,伴随着大宗工业废弃物的产生,工业废弃物资源化利用效率低以及安全处置不当已经给环境造成了严重的污染,尤其是含有重金属及高碱性的赤泥等工业固体废弃物。目前,我国赤泥主要采用露天堆存的处置方式,这种处置方式对水体、空气、土壤等生态环境造成严重的污染,甚至威胁到人民的身体健康。利用赤泥制备建筑材料是赤泥资源化利用的有效途径,其中利用赤泥制备陶粒具有广阔的市场和应用潜力。因此,本文提出利用赤泥和固废基硫铝酸盐水泥为原料,采用免烧结工艺,制备赤泥基绿色免烧结陶粒的创新思路,降低能耗的同时,实现了赤泥大规模资源化利用。首先在课题组研究基础上,利用赤泥、脱硫石膏、铝灰、电石渣四种工业固废制得了具有快硬、早强、高强的固废基硫铝酸盐水泥;然后,以固废基硫铝酸盐水泥为胶结剂,再度结合赤泥,利用圆盘式造粒机实现赤泥基免烧结陶粒的制备,研究了其物理性能、水化矿物、微观结构以及重金属浸出特性。最后,利用赤泥基免烧结陶粒作粗骨料,完成干压路面砖的制备,并分析了其强度、吸水率、干密度、抗冻性能以及制备成本,不仅为赤泥基免烧结陶粒的工业化应用提供了新的思路,而且形成了从固废到赤泥基免烧结陶粒再到干压砖的全固废一体化技术路线。研究结果表明:(1)利用赤泥、铝灰、脱硫石膏和电石渣四种工业固废制备的固废基硫铝酸盐水泥熟料的主要矿物相为硫铝酸四钙、硅酸二钙以及少量的钙铝黄长石,与普通硫铝酸盐水泥矿物组成相似,具备早强、高强、快硬的优异性能。(2)赤泥基绿色免烧结陶粒最佳制备工艺参数:固废基硫铝酸盐水泥掺量为30%,成球角度为45°,成球盘临界转速为33 rpm。最佳工艺条件下制备的赤泥基免烧结陶粒的成球率约90%左右;粒径大小主要分布在5-20 mm之间;堆积密度为900-1000 kg/m3,满足GB 174311-2010 1000密度等级的标准要求;表观密度在1890-2014kg/m3之间,低于普通石子2300-2600kg/m3的表观密度;1 h吸水率约为11.46%,略高于GB 174311-2010中人造轻集料1 h吸水率小于10%的标准;赤泥基绿色免烧结陶粒28 d筒压强度为7.98 MPa,超过人造高强轻粗集料筒压强度须达到6.5 MPa的标准。(3)赤泥基免烧结陶粒的主要水化产物是钙矾石、硅酸二钙和铝胶,钙矾石的形成是赤泥基绿色免烧结陶粒获得高强性能的本质原因;从微观形貌可以看到结晶度较高的钙矾石呈棒状或柱状(AFt)、铝胶(Al2O3·H2O,AH3)呈绒球状分布,钙矾石相互搭接形成骨架结构,铝胶等凝胶体和未参与水化反应的赤泥颗粒胶结并充填在骨架结构中,共同形成了赤泥基绿色免烧结陶粒硬化体的微观结构,这种结构是赤泥基绿色免烧结陶粒获得高强性能的本质原因;赤泥基绿色免烧结陶粒中重金属浸出浓度均远低于GB/T 5085.3-2007中相应重金属的浸出浓度限值,且固废基硫铝酸盐水泥水化产生的钙矾石对Cr具有良好的固化稳定化作用。(4)利用全固废实现了干压路面砖制备。当赤泥基绿色免烧结陶粒掺量为30%,石膏掺量为5%,用水量为12%,压砖机载荷为14MPa,制备的干压路面砖28 d抗压强度为47.63 MPa,能够满足GB 28635-2012中Cc40的强度标准,24h吸水率为5.87%,经过25次冻融循环后,干压砖抗压强度损失率为19.08%,质量损失率为4.78%,满足GB 28635-2012中抗冻性能指标要求;干压砖的制备总成本约为16.1-20.3元/m2,低于普通干压路面砖工业化生产约24元/m2的成本,同时制备1 m3干压路面砖可利用约788kg垃圾灰渣和525kg赤泥基绿色免烧结陶粒。所以,利用赤泥基绿色免烧结陶粒和垃圾灰渣制备的干压路面砖具有低成本、高性能、环境效益好、应用潜力大等优势。更多还原

【Abstract】 With the acceleration of our country industrialization process and the improvement of people’s quality of life,along with the generation of large amounts of industrial waste,the low efficiency resource utilization and improper safe disposal of industrial waste have caused serious environment pollution,especially those containing heavy metals and highly alkaline,such as red mud.At present,red mud mainly adopts the open-air storage method in China,which causes serious pollution to the ecological environment such as water,air,and soil etc.,even threatens the health of the people.Using red mud to prepare building materials is an effective way to realize the resource utilization of red mud.Among them,ceramsites prepared by using red mud has a broad market and application potential.Therefore,this article proposed a new preparation concept of green red mud-based ceramsites,which using red mud and sulphoaluminate cement as raw materials through sintering-free process.This process can not only reduce energy consumption,but also realize large-scale resource utilization of red mud.First,based on the study of our research team,four industrial solid wastes,including red mud,desulfurized gypsum,aluminum ash,and calcium carbide slag,were used to prepare solid waste-based sulfoaluminate cement with the performance of fast hardening,early strength and high strength.Then,using solid waste-based sulfoaluminate cement as the cementing agent,recombining red mud,and using a disc granulator to realize the preparation of red mud-based sintering-free ceramsites.Its physical properties,hydrated minerals,microstructure and heavy metal leaching characteristics have been studied.Finally,red mud-based sintering-free ceramsites is used as coarse aggregate to prepare dry-pressed pavement bricks,and its strength,water absorption,dry density,frost resistance and preparation cost were analyzed.This study provides a new idea for the engineering application of red mud-based sintering-free ceramsites,and form a total solid waste integration technology from solid waste to red mud-based sintering-free ceramsites to dry-pressed bricks route.Research indicates:(1)The main mineral phases of solid waste-based sulfoaluminate cement clinker prepared from four industrial solid wastes of red mud,aluminum ash,desulfurized gypsum and calcium carbide slag are C4A3S,AH3 and C2S,which is similar to the mineral composition of ordinary sulfoaluminate cement.It has the excellent properties of early strength,high strength and fast hardening.(2)The best preparation process parameters of the red mud-based green sintering-free ceramsites:the content of solid waste-based sulfoaluminate cement is 30%,the inclination angle of pelletizing disc is 45°,and the critical speed of pelletizing disc is 33 rpm.The pelletizing rate of the red mud-based sintering-free ceramsites prepared under the optimal process conditions is approximately 90%;the particle size is mainly distributed between 5-20 mm;the bulk density is 900-1000 kg/m3,which can meet the requirement of 1000 density grade in GB 174311-2010;apparent density between 1890-2014 kg/m3,lower than the apparent density of ordinary stone 2300-2600 kg/m3;the water absorption for 1 h is approximately 11.46%,slightly higher than GB 174311-2010,which the 1 h water absorption rate of artificial lightweight aggregates was less than 10%;the 28 d cylinder compressive strength of red mud-based green sintering-free ceramsites is 7.98 MPa,which exceed the standard that the cylinder compressive strength of the artificial high-strength lightweight coarse aggregate need to reach 6.5 MPa.(3)The main hydration products of the red mud-based sintering-free ceramsite are ettringite(AFt),dicalcium silicate(C2S)and alumina gel(AH3).The formation of ettringite is the fundamental reason for the high strength performance of the red mud-based green sintering-free ceramsites.From the microscopic morphology,AFt with higher crystallinity is in the shape of rods or columns,and the AH3 is distributed in the shape of pompoms.The ettringite overlaps each other to form a framework structure,red mud particles that are not involved in the hydration reaction and aluminum gel are cementitious and filled in the framework structure to form a microstructure of the red mud-based green sintering-free ceramsites hardened body.This is structural reasons for the red mud-based green sintering-free ceramsites to obtain high-strength performance.The leaching concentration of heavy metals from red mud-based green sintering-free ceramsites were far lower than the corresponding concentration limit of heavy metal leaching in GB/T 5085.3-2007,and the ettringite produced by the hydration of solid waste-based sulfoaluminate cement has a good solidification and stabilization effect on Cr.(4)The preparation of dry-pressed pavement bricks were performed by using all industrial solid waste.When the content of red mud-based green sintering-free ceramsites is 30%,the desulfurization gypsum is 5%,the water consumption is 12%,the brick press equipment load is 14 MPa,and the 28 d compressive strength of the prepared dry pressed pavement brick is 47.63 MPa,it can meet the strength standard of Cc40 in GB 28635-2012.The water absorption rate for 24 h is 5.87%.After 25 freeze-thaw cycles,the compressive strength loss rate of dry pressed brick is 19.08%,and the mass loss rate is 4.78%,which meets the requirements of GB 28635-2012 frost resistance performance index requirements.The total cost of preparing dry-pressed pavement bricks is about 16.1-20.3 yuan/m2,which is lower than the cost of about 24 yuan/m2 for the industrial production of ordinary dry-pressed pavement bricks.At the same time,about 788 kg refuse incineration residue and 525 kg red mud-based green sintering-free ceramsites can be used to prepare 1 m3 of dry-pressed pavement bricks.Therefore,using red mud-based green sintering-free ceramsites and refuse incineration residue to prepare dry-pressed pavement bricks has the advantages of low cost,high performance,good environmental benefits,and great application potential.更多还原