Distribution of Na+and Mechanical Properties of Hardened Body of Alkali-activated Cementitious Materials

To explore the distribution of and the mechanical properties(compressive strength)of the hardened body of alkali slag-fly ash cementitious materials,this study was conducted by using the XRD,FTIR,SEM/EDS,and other test methods in three conditions:airtight drying(AD),airtight immersion(AI),and airtight soaking(AS).The 1D distribution law of free of hardened body under standard curing conditions was explored.The experimental results show that under standard curing conditions,the 1D distribution of within 0d-3 d shows a∨-shaped distribution,within 3-7 d show a∧-shaped distribution,and within 7-28 d tends to be balanced.The test results of leaching rate show that the free was the most stable under AD conditions and the hardened body bound the most by XRD,FTIR and SEM/EDS.And the compressive strength of the hardened body was the highest.The compressive strength of 28th reached 95.9 MPa.The definite distribution of provides an important reference for the strength development and durability evaluation of the hardened body of alkaliexcited cementitious materials.

Effect of the Retarder on Initial Hydration and Mechanical Properties of the"one-step"Alkaliactivated Composite Cementitious Materials

This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly ash(FA),and analyzed its mechanical properties,hydration mechanism,and retardation mechanism.The effects of retarders on the hydration products,mechanical properties,and hydration kinetics of ACCM were investigated using XRD,SEM,FTIR,EDS,and thermoactive microcalorimetry.The results showed that Na_(2)B_(4)O_(7)·10H_(2)O(B)delayed the exotherm during the alkali activation process and could effectively delay the setting time of ACCM,but the mechanical properties were slightly decreased.The setting time of ACCM increased with the increase in SG content,but the mechanical properties of ACCM decreased with the increase in SG content.C1_(2)H_(22)O_(11)(CHO)could effectively delay the hydration reaction of ACCM and weakly enhanced the compressive strength.H_(3)PO_(4)(HP)at a concentration of 0.05 mol/L had a certain effect on ACCM retardation,but HP at a concentration of 0.07 and 0.09 mol/L had an effect of promoting the setting and hardening time of ACCM.

The Durability of Alkali-Activated Materials in Comparison with Ordinary Portland Cements and Concretes:A Review

China is the largest producer and user of ordinary Portland cement(OPC),and the rapid growth of infrastructure development demands more sustainable building materials for concrete structures.Alkali-activated materials(AAMs)are a new type of energy-saving and environmentally friendly building material with a wide range of potential applications.This paper compares the durability of AAMs and 0 PC-based materials un der sulfate attack,acid corrosion,carb on ation,and chloride penetratio n.Different AAMs have shown distinct durability properties due to different compositions being formed when different raw materials are used.According to the calcium(Ca)concentration of the raw materials,this paper interprets the deterioration mechanisms of three categories of AAMs:calcium-free,low-calcium,and calcium-rich.Conflicts found in the most recent research are highlighted,as they raise concerns regarding the consistenee and long-term properties of AAMs.Nevertheless,AAMs show better durability performances than OPC-based materials in general.

Adhesion performance of alkali-activated material for 3-dimensional printing of tunnel linings at different temperatures

Robotic-based technologies such as automated spraying or extrusion-based 3-dimensional(3D)concrete printing can be used to build tunnel linings,aiming at reducing labor and mitigating the associated safety issues,especially in the high-geothermal environment.Extrusion-based 3D concrete printing(3DCP)has additional advantages over automated sprayings,such as improved surface quality and no rebound.However,the effect of different temperatures on the adhesion performance of 3D-printed materials for tunnel linings has not been investigated.This study developed several alkali-activated slag mixtures with different activator modulus ratios to avoid the excessive use of Portland cement and enhance sustainability of 3D printable materials.The thermal responses of the mixtures at different temperatures of 20 and 40℃ were studied.The adhesion strength of the alkali-activated material was evaluated for both early and later ages.Furthermore,the structural evolution of the material exposed to different temperatures was measured.This was followed by microstructure characterization.Results indicate that elevated temperatures accelerate material reactions,resulting in improved early-age adhesion performance.Moreover,higher temperatures contribute to the development of a denser microstructure and enhanced mechanical strength in the hardened stage,particularly in mixtures with higher silicate content.

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.

Life cycle assessment of alkali-activated materials:a systematic literature review

The physical-mechanical,chemical,and durability characteristics of alkali-activated materials(AAMs)have been widely investigated.However,a critical gap in the literature is the lack of a comprehensive overview of recently published literature regarding the life cycle assessment(LCA)of these binders.This study aims to fill that gap by conducting a systematic literature review of globally published literature on the topic.This paper consolidates knowledge by searching different databases,focusing on LCA studies that used AAMs as pastes,mortars,concretes,bricks,and rammed earth/soil blocks.The selected articles were reviewed and categorized based on precursors,alkaline activators,functional units,system boundaries,life cycle inventory databases,allocation,impact methodologies,and software used.Additionally,this paper also critically analyzes the key challenges of LCA for AAMs.The major challenges were identified as selecting a functional unit,subjectivity in boundary systems,and data interpretation.This work concludes that AAMs show substantial advantages in global warming potential compared to ordinary Portland cement-based materials;however,the average of other categories such as marine ecotoxicity and ozone layer depletion has been reported to be higher than for the reference samples.

海藻酸钠改性垃圾焚烧底灰-矿渣基胶凝堵漏材料研究

针对传统矿用水泥基堵漏材料存在的收缩开裂、高能耗及高碳排放的问题,探索采用海藻酸钠(SA)交联金属离子,制备SA改性垃圾焚烧底灰(MSWI-BA)-粒化高炉矿渣(GBFS)基胶凝堵漏材料(SWM)。通过抗压强度和凝结时间的测试,确定了最佳水固比为0.4。通过胶凝材料在不同温度下的抗压强度、收缩率及裂缝形貌的分析,探究了SA改性对胶凝材料的耐高温性能的影响,结果表明SA改性后,胶凝材料的耐高温性得到了改善,受热后改性胶凝材料表面裂缝明显减少,收缩率较改性前最大降低了26.5%,在400℃受热后,剩余抗压强度仍高达17.25 MPa。结合微观形貌、孔结构性能和热分析实验,探究了SA改性胶凝材料的形成机理,结果表明,SA改性MSWI-BA-GBFS基胶凝堵漏材料通过SA与底物中的Ca^(2+)/Al^(3+)的配位交联与碱激发底物形成的硅铝酸盐共价网络协同作用,细化孔径,减小孔容,在受热后保持基体结构的完整性,从而改善胶凝材料的抗收缩开裂性。堵漏风模拟实验结果表明,水固比0.4的SA改性MSWI-BA-GBFS基胶凝堵漏材料的堵漏性能优于矿用水泥基材料,表现出较好的堵漏性能。SA改性MSWI-BA-GBFS基胶凝堵漏材料的研制不仅为城市垃圾焚烧底灰的资源化利用提供了有效途径,还提供了一种抗压强度高、抗收缩开裂且耐高温的可以完全替代传统矿用水泥基堵漏材料的环保防灭火材料。

早强型钢渣基胶凝材料的制备及其水化机理研究

钢渣是炼钢过程中产生的主要废弃物,具有用途单一、产生量大、污染环境等特点。本文使用钢渣微粉、42.5普通硅酸盐水泥分别与增强剂Ⅰ、增强剂Ⅱ混合制备早强型钢渣基胶凝材料,通过测定原料化学成分、矿物组成,测试胶凝材料的力学性能,分析其热稳定性、微观形貌来揭示胶凝材料的水化机理。研究结果表明:胶凝材料的早期抗压强度大幅提高,后期抗压强度良好;这是因为增强剂能促进Ca(OH)2消耗并提高水化反应速率,Ca(OH)2水解出的OH-能促进钢渣微粉中玻璃体溶出硅酸盐,与Ca^(2+)生成C-S-H凝胶;增强剂含有的硫酸盐能与胶凝材料生成钙矾石AFt,并填充于凝胶孔隙中,增强了材料的密实度。早强型钢渣基胶凝材料的最优配比为钢渣微粉125 g、增强剂Ⅱ用量10 g。研究成果为早强型钢渣基胶凝材料的制备提供了新思路,也可为钢渣综合利用研究提供借鉴。

碱激发胶凝材料在充填领域的应用及发展

碱激发胶凝材料是一种由硅铝酸盐矿物在碱激发剂的激发活化作用下形成的无机胶凝材料,具有强度高、耐久性优异、绿色环保等优点。为明确碱激发胶凝材料在溶洞等充填领域的应用现状,简要介绍了碱激发胶凝材料胶结骨料的反应机理,分别阐述了碱激发矿渣、粉煤灰、尾矿和有色金属冶炼渣等胶凝材料在充填领域的研究进展,概括提出了碱激发胶凝材料在充填领域的下一步研究发展趋势。结论表明,碱激发胶凝材料胶结骨料的反应机理主要包括溶解、解聚、缩聚和固化等阶段,相较于水泥基胶结充填体,碱激发矿渣、粉煤灰、尾矿和有色金属冶炼渣胶结充填体表现出了更为显著的力学特性、工作性能、成本低廉和环境相容性。

玻化微珠-水泥/水玻璃隔热注浆材料正交试验

目的为解决深部矿井开采出现的高温热害问题,提出以玻化微珠为掺合料的水泥/水玻璃注浆材料进行隔热支护的新思路。方法采用正交试验的方法,研究水灰比(因素A)、玻化微珠掺量(因素B)、水玻璃与水泥浆体积比(因素C)3种因素对注浆材料性能的影响。结果获得最优配比为A_(1)B_(3)C_(3),90d抗压强度为20.2MPa,即水灰比为0.6,玻化微珠掺量为45kg/m^(3),水玻璃与水泥浆体积比为0.6。3种因素对抗压强度的影响顺序为水灰比影响最大,其次是水玻璃与水泥浆体积比,最后是玻化微珠掺量;对于胶凝时间,水玻璃与水泥浆体积比有较为显著影响,玻化微珠掺量、水灰比影响较小;对于结石率,玻化微珠掺量和水灰比影响显著,其中后者影响更为显著,最后是水玻璃与水泥浆体积比,结石率最大可接近。结论该种新型隔热注浆材料强度大、结石率大,能够满足井下注浆施工的要求,对于井巷主动隔热环境控制有一定参考。

关于核电厂厂房混凝土氯离子危害与防治探究

目前国内核电厂均处于滨海范围,大气环境会对核电厂厂房混凝土结构在全寿期带来不利影响。混凝土结构是核电厂重要物项和安全屏障,对核电厂厂房安全有着非常重要的作用,核电厂厂房在设计上有着比普通建构筑物更高的质量标准,混凝土的氯离子含量上更是严格控制。通过分析氯离子对混凝土结构的危害,结合核电厂老化数据的分析,对沿海核电厂在混凝土氯离子含量在施工阶段、运营阶段的预防和整治提出措施与建议。

某铁矿充填尾砂力学性能研究

为了优化某铁矿的尾砂充填工艺技术与经济指标,开展了料浆浓度、灰砂比和新型胶凝材料试验。结果表明:(1)水泥是影响充填试块强度的主要因素,料浆浓度提高有利于试块强度的提高;7~28 d龄期试块的强度增长较快,强度增长约1倍;28~90 d龄期,试块的强度普遍增长,水泥含量较多时更明显。(2)在排除沉降、结块等因素后,料浆屈服应力与料浆浓度成正相关关系,非胶结充填的料浆质量浓度宜为74%~72%,胶结充填的料浆质量浓度宜为73%~71%。(3)添加胶固粉有利于提高充填体试块的强度。因此,矿山应开展以新型胶凝材料替代或部分替代矿用水泥的研究与论证工作。

无醛无毒防火秸秆人造板的制备与性能试验

针对目前市场秸秆人造板物理机械性能差,不能完全解决甲醛含量等问题,该研究采用Mg SO4、Mg CO3、活性硅和ALSi O4等做成无机胶凝材料,采用豆胶与改性异氰酸酯(diphenylmethane diisocyanate,MDI)制成有机胶凝材料,无机胶凝材料与有机胶凝材料混合制成胶黏剂。秸秆物料热重分析和秸秆板显微结构观察表明,胶黏剂对提高秸秆板的性能指标具有显著影响。通过五因素四水平L16(45)正交试验优化秸秆人造板的热压工艺,获得最佳工艺条件为:无机胶凝材料与有机胶凝材料质量比为4:1,胶黏剂添加量与秸秆物料质量比为0.65:0.35(固体有效成分在秸秆人造板中质量分数为35%),热压时间3 min,热压温度为100~120℃,热压压力80 MPa。试验研究表明:热压压力、胶黏剂中无机胶凝材料的比例和胶黏剂添加量是影响秸秆板性能的重要因素,最佳工艺组合下生产的秸秆板各项指标均达到中密度纤维板的国家标准,该研究对中国秸秆资源的开发利用和人造板的生产具有重要的参考意义。

基于硝基甲烷的两类凝胶推进剂流变性能研究

分别制备了以气相二氧化硅(SiO2)和羧甲基纤维素硝酸酯(CMCN)为胶凝剂的硝基甲烷(NM)凝胶推进剂,研究了两类凝胶的形成机理及胶凝剂类型对凝胶体系流变性的影响规律。采用线性的流变学方法研究了凝胶体系的屈服性、触变性、蠕变性与温敏性等动态粘弹性,分别利用Power-Law模型、Herschel-Bulkley模型、Burger模型对凝胶的流动曲线、蠕变曲线进行了数据拟合。研究发现,NM/SiO2凝胶是SiO2粒子间通过氢键形成的小分子聚集体团聚而成堆积型网路结构凝胶,而NM/CMCN凝胶是由CMCN大分子链上两亲性基团与有机小分子基团间通过分子链间疏水键、氢键等非共价键相互作用形成的一种交联网络型凝胶。两类凝胶的非牛顿系数n≤0.60.与NM/CMCN凝胶相比,NM/SiO2凝胶具有较高的屈服应力、剪切稀化性和弹性柔量与弹性响应性,具有较差的触变恢复性和较小的内耗,且其凝胶强度在高温与低温下反而有一定的增强。

喷射补偿收缩混凝土中胶凝材料微观结构分析

为了研究喷射补偿收缩混凝土中胶凝材料的相容性,采用X射线、电镜扫描等测试手段,对HCSA、UEA、HEA和CSA四种膨胀剂与D型速凝剂和硅酸盐水泥配制的水泥浆进行微观结构试验,对其水化产物微观晶体的形貌、矿物成分及显微结构进行分析。试验结果表明:硅酸盐水泥、膨胀剂和速凝剂三者之间有较好的适应性。水中养护3 d时水化产物中产生大量的钙矾石,28d时基本形成密实的水泥石结构。通过试验对比分析,得出掺CSA膨胀剂配制的水泥浆水化3 d时生成多而大的柱状钙矾石(AFt),水化28 d的钙矾石相比其他膨胀剂明显增多和长大,XRD图谱中钙矾石衍射峰明显增强,从表观特性上分析得出CSA膨胀剂与水泥和速凝剂相容性最好,适宜配制喷射补偿收缩混凝土。

国内文物保护胶凝材料研究状况及发展趋势——基于中国知网近15年来期刊论文的定量分析

利用CNKI中国知网期刊数据库,对2000~2014年间国内发表的文物保护胶凝材料研究与应用的相关论文进行了查询和统计。在收集整理相关论文的基础上,使用文献计量学方法对年份、作者、机构、基金等要素进行统计分析,主要关注文物黏接、加固、防护（封护）等用途中所用传统胶凝材料和现代高分子胶凝材料的研究与应用状况,并对主要品种的研究现状进行定量分析,希望由此判断典型文物保护材料,尤其是粘结修复胶凝材料研究领域的重点和热点,同时探讨该研究领域的发展趋势。

水玻璃-工业废渣双液注浆材料的研究与应用

采用碱激发工业废渣的原理研制出了一种新型的双液注浆材料,其试验结果表明:此注浆材料凝胶性能好,凝胶时间在几秒到几十分钟范围内可调,并随水灰比及粉煤灰、水玻璃掺量的增加而延长,随水玻璃模数由1增加到3.19而缩短;强度高,28天强度可达30 MPa,随龄期的延长持续增大,随水灰比及粉煤灰掺量、水玻璃掺量的增大而降低,随水玻璃模数由1增加到3.19而增大。文章介绍了该注浆材料的试验研究、成果分析及在武汉长江隧道工程中的应用。

国外固体推进剂技术现状和发展趋势

总结了固体推进剂技术发展情况 ,综述了国外固体推进剂技术现状 ,重点介绍了国外高能量密度材料、含能粘合剂及增塑剂、氧化剂、添加剂以及新型固体推进剂的研究进展情况 ,并提出了固体推进剂技术今后的发展趋势。

自然养护条件下水泥-粉煤灰复合胶凝材料体系早期水化的研究

在自然变温条件下,采用水化热,XRD,TG-DSC手段研究了水泥-粉煤灰复合胶凝材料体系在水灰比一定的条件,粉煤灰掺量和亚硝酸钠掺量对早期水化的影响规律。研究结果表明:在水化热测试中,温度对胶凝材料的早期放热速率影响较大,粉煤灰掺量和亚硝酸钠掺量对其放热速率影响较小,但三者都会影响胶凝材料早期水化放热量;在XRD分析中,随着粉煤灰的掺量增加,水化产物CH在晶体产物中的比例是逐渐下降的,随着亚硝酸钠的增加,水化产物CH在晶体产物中的比例逐渐增加的;在TG-DSC产物分析中,水化产物CH随着粉煤灰掺量和亚硝酸钠掺量的逐渐增大,水化产物CH的含量是逐渐减少的。这表明:亚硝酸钠一方面促进的胶凝材料的水化,生成较多的CH,另一方面激发了粉煤灰的火山灰效应,消耗了部分的CH,生成了不易形成晶体的水化硅酸钙。

胶凝剂对煤矸石多孔材料性能的影响

以周源山煤矿煤矸石作原料,硅溶胶作胶凝剂、十二烷基硫酸钠作发泡剂制备密度0.6 g/cm^3的煤矸石多孔材料。研究了水固比对煤矸石料浆粘度和煤矸石多孔坯体干燥行为的影响,促凝剂对胶凝剂胶凝时间的影响,胶凝剂加入量对煤矸石多孔坯体与烧结体强度的影响,考察了样品断面的气孔形貌。结果表明,水固比为0.3时煤矸石料浆粘度为558.2 mPa·s、促凝剂占胶凝剂0.75wt%-1.0wt%,硅溶胶与煤矸石质量比为0.5时,泡沫浆料的胶凝时间满足操作要求,坯体干燥时不开裂;烧结体抗压强度为1.82 MPa,总气孔率72.6%,气孔分布均匀、孔径大小较为均一、约为100μm。