Preparation of Super Composite Cement with a Lower Clinker Content and a Larger Amount of Industrial Wastes

The effects of the grinding mode,fineness,gypsum kinds and dosage,mix proportions on properties of the composite cements consisting of slag,fly ash,limestone and a lower content clinker were investigated,respectively.The results show that when the proportions among slag,fly ash and limestone are appropriate,the grinding technology and system are reasonable,the optimized gypsums and additives are effective,the 52.5R grade cement (52.5R grade cement means a higher strength than 52.5 at early age) can be prepared by clinker dosage of 50% in weight,the 42.5R or 42.5,32.5 grade composite cement containing 40% and 30% clinker also may be made, respectively.Moreover,the high performance concrete prepared from the above composite cements was studied experimentally.

Plant Test of Industrial Waste Disposal in a Cement Kiln

Destruction of industrial waste in cement rotary kilins(CRKs) is an alternative technology for the treatment of certain types of industrial waste(IW).In this paper,three typical types of industrial wastes were co-incinerated in the CRK at Beijing Cement Plant to determine the effects of waste disposal(especially solid waste disposal )on the quality of clinker and the concentration of pollutants in air emission.Experimental results show that(1) waste disposal does not affect the quality of clinker and fly ash,and fly ash after the IW disposal can still be used in the cement production,(2) heavy metals from IW are immobilized and stabilized in the clinker and cement,and (3) concentration of pollutants in air emission is far below than the permitted values in the China National Standard-Air Pollutants Emission Standard(GB 16297-1996).

三元工业废渣协同水泥固化土的基本特性和机理分析

为了资源化利用工业固废的胶凝活性以求减少水泥使用量,设置10%和20%两种固化剂总掺量,并以纯水泥固化土作为对照组,将赤泥、电石渣和磷石膏3种工业废渣部分代替35%、45%、55%的水泥。研究每种配比方案下固化土的强度、电阻率、抗渗性和浸出液pH值变化规律,并结合SEM、FTIR和XRD谱图揭示三元工业废渣协同水泥固化土的微观机理。结果表明:工业废渣代替水泥存在最优替代率问题,当固化剂总掺量为10%和20%,且三元废渣占比<45%时,力学性能优于零废渣纯水泥固化土,废渣占比达到55%时力学强度低于纯水泥固化土,且固化剂总掺量和养护龄期越大强度越高;无损化的电阻率测试技术对于强度的预测具有较高精度,浸出液的pH值随龄期的增大而降低,含废渣固化土的pH值低于零废渣固化土,不同掺量和龄期固化土的pH值均小于腐蚀性鉴别限值;三元废渣协同水泥固化土的抗渗性优于零废渣水泥固化土。微观试验结果表明固化土中生成了钙矾石、水化硅酸钙和碳酸钙等水化产物,三元工业废渣掺入能产生更多的胶结物,使固化土结构更加致密。

水泥窑纯低温余热锅炉常见问题及应对措施

随着水泥工业的飞速发展,水泥窑纯低温余热发电技术被广泛应用于水泥工业中。该技术利用窑头(AQC)和窑尾(SP)排出的废热烟气热量加热余热锅炉水,经过一系列转换后将锅炉水转变为过热蒸汽,进而推动汽轮机组发电。该技术的应用显著提高水泥制造企业的能源利用率,降低大气污染,是企业降本增效、节能减排的重要举措。该文主要介绍水泥窑纯低温余热锅炉的工作原理及其在运行过程中的常见问题,分析问题的形成原因,并提出相应的解决措施,以期为水泥窑纯低温余热锅炉的安全经济运行,维护保养、检修及定期检验提供科学指导。

经济角度论证水泥窑燃料替代技术发展路径选择

随着双碳政策的不断推进,作为我国高能耗的行业之一,水泥行业的节能减排面临越来越大的压力。国内目前已有多条水泥窑完成替代燃料入窑项目的建设,并分别进行了工业废纺、农林垃圾、炭黑、轮胎等物料的燃煤替代尝试。本文将对替代燃料来源、原料预处理、入窑方式、煤价波动等影响因素进行经济可行性综合分析,探索适合我国水泥行业燃煤替代全流程建设路径。

当前国内水泥市场面临的挑战与机遇

文章概述了当前国内水泥行业的发展现状,为了提振行业景气度,提高企业效益,提出水泥企业有必要跟随国家政策的引导,抓住建材工业绿色高质量发展、环境保护超低排放、管理制造数智化转型、推进国际化发展等多方面的机遇来提升企业的市场竞争力。

利用工业固体废弃物制备全固废无熟料水泥的试验研究

采用钢渣、矿渣、三级粉煤灰、脱硫石膏和碱渣为原料制备全固废无熟料水泥,通过调整各个物料之间的比例,研究其凝结时间和抗压强度。研究发现:当钢渣掺入质量为30%时,28 d胶砂强度可达39.2 MPa;用10%的粉煤灰替代矿渣,28 d胶砂强度有少量降低,其值为36.1 MPa。加入Na_(2)SiO_(3)对全固废无熟料水泥凝结时间具有较好的调节效果,当Na_(2)SiO_(3)掺入质量为0.6%时,全固废无熟料水泥的初凝时间为145 min,终凝时间为239 min,与普通硅酸盐水泥相近。同时,Na_(2)SiO_(3)对全固废无熟料水泥的强度具有较好的激发效果,当Na_(2)SiO_(3)掺入质量为0.6%时,其28 d胶砂强度增大到49.5 MPa。

水泥行业工业固体废物资源综合利用评价要点分析

围绕工业固废综合利用评价工作,通过规范第三方机构工作流程,实现水泥行业工业固体废物资源综合利用评价标准化,将水泥企业工业固废综合利用评价流程划分为申请受理、签订评价合同、确定评价方案、资料审查、核查现场、报告编制、技术评审、评价报告提交、评价记录存档等九个控制过程,并对各过程中评价要点进行细化、分析和研究。

High Water Content Material Based on Ba-Bearing Sulphoaluminate Cement

A new type of high water content material which is made up of two pastes is prepared, one is refute from lime and gypsum, and another is based on Ba-bearing sulphoaluminate cement. It has excellent properties such as slow single paste solidifing ,fust double pustes solidifing ,fast coagulating and hardening, high early strength, good suspeasion property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD, DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.

Modification of Fluorgypsum as Cement Retarder

The chemical composition and mineral structure of fluorgypsum as well as its harm to application in cement were elaborately analyzed. The primary fluorgypsum was modified and its applications in cement＇s production were studied. The technological flow chart of preparing modified fluorgypsum was given. Experimental results indicate that hydration ratio the modified fluorgypsum through adding compound additive for 14d is about 70%. The modified fluorgypsum as cement retarder has certain stimulation to fly ash and increases the strength of compound cement. In addition, its adding amount is lower than that of natural gypsum. The modified fluorgypsum is a good substitute for natural gypsum.

Influence of CG With High Content of Metallic Particles as a Cement Admixture on Cement Strength

Copper gangue (CG), containing a large amount of water with grain sizes of 0.037 to 0.10mm,is an inactive industrial waste generated from copper refineries. When it is dried and used as a cement admixture, the influence of the presence of finely dispersed metallic particles in CG on the microstructure and compressive strength of cement paste has been studied.The results show that the higher the replacement of CG is,the lower the compressive strength of cement mortar is.However,the long-term strength of the specimens with 10% CG,especially after being cured for 3 months,approached to that of the plain mortar.Its mechanism was studied by an electron probe X-ray microanalyzer (EPXMA).The results indicate that a small quantity of Fe(OH) 3·nH 2O slowly formed from Fe 2O 3 in the presence of Ca(OH) 2, free CaO and MgO of the clinker also slowly hydrated and formed Ca(OH) 2 and Mg(OH) 2 respectively,so the hardened cement paste became more compact.

Sustainable Construction—Use of Stone Dust as Plasticiser in High Strength SCC with Blended Cement

Extensive growth in the developing countries due to infrastructure development is resulting into massive consumption of concrete thereby increasing the demand on concrete materials. Quite large amounts of fine aggregates are required for concrete in developing countries thus shortages of quality river sand is putting pressure on availability of fine aggregates. To fulfill the high demand of fine aggregates, a search for alternative materials is in process. Stone crushing and processing industry is a large industry which generates large amounts of stone dust and slurry which is a waste produced from this process. Tons of such waste generated has no useful purpose except as landfill material. Some preliminary studies have been conducted into use of marble/ limestone waste for use in concrete [1] [2].?This study aims at using stone dust as partial replacement of sand in concrete to observe its effects on workability and other mechanical properties. This would result in useful consumption of this waste product thereby eliminating environmental issues related to its disposal. Partial replacement of 10% and 20% sand replacement with stone dust is carried out with the use of self-compacting concrete with blended cement. Blended cement used contains 50% rice husk ash and 50% Portland cement. Such high strength SCC with blended cement containing 50% rice husk ash and 50% Portland cement has already been tested to provide better quality concrete [3]. Wide ranging investigations covering most aspects of mechanical behavior and permeability were carried out for various mixes for compressive strengths of 60?MPa & 80?MPa. Compressive strengths of high strength SCC with blended cements and 10% and 20% replacement of sand with stone dust for 60?MPa and 80?MPa were observed to be higher by about 10% to 13% than the control specimen. Higher elastic moduli and reduced permeability were observed along with better sulphate and acid resistance. Better strengths and improved durability of such high strength SCC make it a more acceptable material for major construction projects thereby reducing the burden on environment and use of such waste product for a useful purpose promoting sustainable construction.

Effects of Wood Ash and Waste Glass Powder on Properties of Concrete in Terms of Workability and Compressive Strength in Jaresh City

The potential for using fly ash as a supplementary cementing material in concrete has been known almost since the beginning of the previous century. Fly ash was used as a supplementary cementing material (SCM) in the production of Portland cement concrete. A supplementary cementing material, when used in conjunction with Portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both. In this study, the fly ash and waste glass powder were used in concrete blocks to study the improvement of concrete in terms of workability and strength. Therefore, an experimental study will be conducted to measure the engineering properties of cured concrete. In this research, local raw material from Jaresh area was used.

Ashes of Biogenic Wastes—Pozzolanicity, Prospects for Use, and Effects on Some Engineering Properties of Concrete

The growing concern for the environment all over the world, as well as the high cost of Portland cement has placed limitation on its use as the sole binding material in concrete. This work has shown that ashes from some agricultural or other biogenic wastes when mixed with appropriate amounts of ordinary Portland cement (OPC) can be used as low-cost, environmentally, more friendly binders for concrete production, than using OPC alone. Experimental determination of requisite properties of the ashes of rice husk, coconut husk, palm leaf, bamboo leaf and peanut shell revealed that they satisfy the essential requirements for pozzolans. Further experimental work was carried out on OPC/rice husk ash (RHA) and OPC/coconut husk ash (CHA) concretes to determine their essential properties in fresh and hardened states. Although the initial and final setting times of OPC/RHA and OPC/CHA pastes were longer than the setting times of 100% OPC paste, they are all within the limits specified by relevant standards. The workability of fresh concrete produced by partially replacing OPC with either of RHA and CHA was found to be better than with 100% OPC. It was also shown that the porosity of OPC/RHA and OPC/CHA concretes was less than the porosity of OPC concrete. Strength tests using very finely ground RHA and CHA to partially replace Portland cement in concrete production showed that at up to 15% replacement the strength activity index of each of them is greater than 100%, which indicating that they are excellent pozzolans.

固废制备低碳少熟料水泥的试验研究

文中以矿渣、脱硫石膏、钢渣等工业固体废弃物及水泥熟料为主要原料,通过掺入硫酸钠、甲酸钙等激发剂制备低碳水泥胶凝材料,研究了各因素对低碳水泥力学性能的影响。结果表明,当矿渣、脱硫石膏、钢渣、水泥熟料掺量分别占质量的56%、15%、20%、9%,激发剂中硫酸钠0.5%、甲酸钙0.8%时,胶凝体系力学性能最佳,试验所制备的低碳水泥抗压基本可以达到P·O 42.5水泥强度要求。

工业废渣-氯氧镁水泥固化工程泥浆力学特性与微观机制

基于无侧限抗压强度、渗透和扫描电镜试验,研究工业废渣-氯氧镁水泥固化絮凝-抽滤处理泥浆抗压强度、渗透性及微观机理,探索絮凝剂类型、固化剂配比、养护龄期等因素对固化泥浆力学特性影响过程与内在机制。结果表明:随工业废渣与水泥相对配比增加、养护龄期延长,固化泥浆试样抗压强度和刚度随之提高。相同条件下,氢氧化钙絮凝-抽滤处理泥浆固化后强度高于阴离子聚丙烯酰胺絮凝-抽滤处理泥浆。固化泥浆渗透系数大幅降低,随工业废渣掺量增长,固化泥浆渗透系数随之降低。工业废渣的物理填充作用和水化硅酸钙、水化硅酸镁的黏聚作用,被认为是固化泥浆强度提升和渗透系数降低的关键机制。

改性磷石膏在普通硅酸盐水泥中的应用

通过小磨试验研究了改性磷石膏对普通硅酸盐水泥凝结时间及强度的影响,确定了冬夏两季应用改性磷石膏生产水泥的配比。生产实际表明,应用pH值为7~13的磷石膏生产的水泥产品完全满足国家标准要求,凝结时间可调控范围宽;应用改性磷石膏既消化了工业生产废渣,又降低了生产成本,带来了较好的社会效益与经济效益。

工业废渣协同水泥改良膨胀土试验研究

为推广水泥改良膨胀土在寒冷地区的应用,探索工业废渣资源化利用的新路径,本次研究提出采用工业废渣增强水泥改良膨胀土的抗冻性。得出主要结论如下:(1)工业废渣协同水泥改良膨胀土的最佳配合比为14%水泥+10%粉煤灰+2%脱硫石膏;(2)ESC试件与ESC-FG试件的三轴应力应变曲线形态相似,但ESC-FG试件的应力应变曲线下降段比ESC试件平缓;冻融循环下,ESC-FG试件比ESC试件的外观更完整、质量损失更小、强度更高,冻融循环20次后,ESC-FG试件的强度较ESC试件高89%;(3)通过SEM电镜观察发现,与ESC试件相比,ESC-FG试件的水化产物数量更多、结构更密,并形成以柱状钙矾石晶体和纤维状硅酸钙凝胶为结构骨架、硅酸钙凝胶为包裹的致密结构,从而使其强度和抗冻性获得显著提升。