The Competitive Adsorption Characteristics of Welan Gum and Superplasticizer in Cement Mortar

Welan gum has been widely used in oil cement and grouting materials for its excellent rheological properties and anti-bleeding,and most of all,being friendly to the environment.However,when welan gum was added,the fluidity of mortar decreased sharply,so it should be used together with a superplasticizer to enable good workability.With its powerful charge density in the molecular structure,the competitive adsorption between welan gum and other admixtures happened remarkably during the addition process.Consequently,we experimentally studied on the bleeding rate and rheological properties of cement slurry,fluidity and mechanical properties of mortar with welan gum mixed with superplasticizer,aiming at understanding the competitive adsorption phenomenon by application of welan gum mixed with superplasticizer.By measuring the hydration heat and zeta potential,the mechanism of interaction of welan gum with superplasticizer was deduced and explained.The results showed that it could ensure a good dispersion effect when welan gum is mixed with the two kinds of superplasticizer.Welan gum had little impact on the naphthalene superplasticizer,but did have a substantial influence on polycarboxylate.In practice,adding welan gum after PCE acted with cement for 2 min could effectively avoid the competitive adsorption and then achieve better performance.On this viewpoint for mortar with PCE,new delay release welan gum needs further research and development.     

水泥基灌浆料工作性的实验

目的通过研究不同外加剂对水泥基灌浆料工作性的影响,解决工程中高性能灌浆料的高工作性问题．方法采用高度（60±0．5）rnl／l、上口内径（70±0．5）mm、下口内径（100±0．5）nqm、下口外径120mm的截锥圆模、玻璃板、直尺等工具,依据《GB／T2419水泥胶砂流动度测试方法》对水泥基灌浆料进行流动性测试．结果硫铝水泥基灌浆料与普硅水泥基灌浆料相比,其初始流动度与30min流动度较好,且最小水胶比为0．21．采用萘系、聚羧酸,SM（均为固体）减水剂的硫铝水泥基灌浆料,在初始流动度大于300mill的前提下,最小水胶比分别为0．26、0．21、0．27．硫铝水泥基灌浆料随着聚羧酸减水剂掺量的增加,初始流动度和30min后的流动度均明显增加,最佳掺量在3％o～5％o．缓凝剂掺量的增加对硫铝水泥基灌浆料的初始流动度影响不明显,对其30min后的流动度影响较为突出,最佳掺量不超过6％o．结论测定硫铝水泥与普硅水泥基灌浆料的工作性,结果相差较大,说明水泥物理化学性质对减水剂的适应性产生较大影响;外加剂对水泥基灌浆料的流动度影响显著,宜控制在合理范围之内．     

Use of Recycled Glass in Architectural Mortars

In recent years,recycled glass has been widely used as aggregate replacements in concrete. Owing to the aesthetic potential of the coloured recycled glass,this research aims to fully utilize this advantage for their higher end uses,such as architectural mortar. In this study,architectural white cement mortar was produced with a self consolidating method using recycled glass as the aggregate. An adequate amount of Metakaolin was incorporated into the mortar to mitigate the adverse effect of alkali-silica reaction. The results show that the self-compacting method is suitable to produce architectural mortar containing up to 100% recycled glass. Overall,the performance of all the architectural mortar mixtures in terms of both fresh and hardened properties was good.     

免振捣高强高性能混凝土的试配研究

研究针对高强度高性能混凝土实现免振捣的关键——降低混凝土的屈服应力和粘度入手,优选高性能减水剂,试配了不同浆体体积、水灰比、砂率的免振捣高强高性能混凝土,并研究其工作性能及强度的主要影响因素,进而采用不同种掺和料配置出C80~C100级免振捣高强高性能混凝土,经耐久性实验,表明该种混凝土完全可以在实际工程中应用.     

The Impermeability Mechanism of Self-compacting Water Proof Concrete

The impermeability mechanism of water-proof self-compacting concrete ( WPSCC ) was studied.The mechanism ancl influential factors, such as water-cement ratio(w/c), dosage of powder, superplastieizer,sand content, aggregate content, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC suceessfully applied in tunnel liner with its validities, conveniences and economies by mockup test was developed and optimized. Experimental results show their the WPSCC has good workability,mechanical properties and impermeability when reasonable requirements are fulfilled.     

Tensile and flexural properties of ultra high toughness cemontious composite

The tensile and flexural properties of polyvinyl alcohol (PVA) fiber reinforced ultra high toughness cementitious composite (UHTCC) were investigated. The composite, tested at the age of 14 d, 28 d and 56 d, shows extremely remarkable pseudo strain hardening behavior, saturated multiple cracking and ultra high ultimate strain capacity above 4% under uniaxial loading. Also, the corresponding crack widths are controlled under 50 μm even at 56 days age. In the third point bending tests on thin plate specimens, the composite shows ultra high flexural ductility and multiple cracking on the tension surface. The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC. SEM observation on fracture surfaces provides indirect evidence of optimal design for the composite. Funded by the Hong Kong Research Grant Council(CERG UST6138/04E), the Key Program of National Natural Science Foundation of China(No.50438010) and the Research & Application of Key Technology for the South-North Water Transfer Project Construction in China(JGZXJJ2006-13)     

Influence of Superplasticizers on Strength and Shrinkage Cracking of Cement Mortar under Drying Conditions

The effects of polynaphthalene series superplasticizers（PNS） with a low content of sodium sulfate （H-UNF）,with a high content of sodium sulfate（C-UNF） and polycarboxylate type superplasticizer （PC） on strength and shrinkage cracking of cement mortar under drying conditions were investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase the initial cracking time of mortars, and decrease the cracking sensitivity of mortars. As for decreasing the cracking sensitivity of mortars, PC〉H-UNF〉C-UNF. To incorporate superplasticizers is apparently to increase the free shrinkage of mortars when keeping the constant w/b ratio and the content of cement pastes. As for the effect of controlling the volume stability of mortars, PC〉C-UNF〉H-UNF. Maximum crack width of mortars containing PC is lower, but the development rate of maximum crack width of mortars containing H-UNF is faster in comparison with control mortars. The flexural and compressive strengths of mortars at 28-day increase with increasing superplasticizer dosages under drying conditions. PC was superior to PNS in the aspect of increasing strength.     

聚合物-水泥基注浆材料早期流变及水化特性

为制备满足复杂地层加固工程需求的高性能水泥基注浆材料,探究以偏铝酸钠(SA)、聚羧酸(Sp)及高吸水性树脂(SAP)为组分的聚合物体系及其掺量对新拌水泥浆体流变特性与泌水率的影响,并采用水化放热监测与倒置荧光显微技术,对不同体系下水泥浆体早期水化进程及微米级颗粒的悬浮分散形态进行分析.结果表明:新拌水泥浆液流动性和泌水率与SA、SAP掺量呈负相关,随Sp掺量增加而提高. Sp及SAP延缓了水泥早期水化进程,改性样延迟近1 h进入水化诱导期,诱导期内水化放热速率显著降低.在不同掺量SA的促凝效应、Sp的分散效应以及SAP的"水库"作用下,新拌水泥浆液表现为初始及经时流动度大于200 mm的高流态期可分别被控制在10、20、30 min内且析水率小于5%(稳定性浆液),接近临界期时流动度陡降、流变参数突增并迅速凝结的流变特性.结合微观结构观测结果,建立了新拌水泥浆体流变演化模型,揭示多聚合物协调效应下水泥浆体呈现分散-储水-流变-水化的早期流变机制.     

氨基磺酸盐系高效减水剂的改性研究

氨基磺酸盐系减水剂具有高减水率、抑制混凝土塌落度经时损失等优点,但泌水严重,限制了其在混凝土中的应用。本文根据“分子设计”原则,通过单体A和单体U引入适当的官能团,对传统氨基磺酸盐系高效减水剂进行改性,测试了产品对水泥净浆流动度、流动度经时损失和泌水率的影响。试验表明,单体A的改性效果优于单体U,以9%的单体A改性后,减水剂的分散性和分散保持性能好,泌水率显著降低。     

Compressive strength development and microstructure of cement-asphalt mortar

The compressive strength developing process and the microstructure of cement-asphalt mortar (CA mortar) were investigated. The fluidity of CA mortar has a great influence on its strength. The optimum value of spread diameter of slump flow test is in the range of 300 to 400 mm. The compressive strength of CA mortar keeps a relatively high growth rate in 56 days and grows slowly afterwards. The residual water of hydration in CA mortar freezes under minus environmental temperature which can lead to a significant reduction of the strength of CA mortar. Increasing A/C retards asphalt emulsion splitting and thus prolongs the setting process of CA mortar. The hydration products of cement form the major structural framework of hardened CA mortar and asphalt is a weak phase in the framework but improves the viscoelastic behavior of CA mortar. Therefore, asphalt emulsion should be used as much as possible on the condition that essential performance criterions of CA mortar are satisfied.     

新型羧酸盐高效减水剂的合成试验

根据混凝土外加剂分子设计理论，试验采用了自制丙烯酸聚乙二醇单酯、丙烯酸钠盐和二乙烯三胺通过Michael加成制得一种新型羧酸盐高效减水剂．对该新型减水剂进行了水泥净浆流动度测试，结果表明该减水剂具有良好的分散能力与流动保持性，其掺量的质量分数为1．5％，水灰质量比为0．29时，水泥净浆流动度达218mm。     

一种高精准水泥浆体流动性测定装置

针对传统净浆流动度测试方法灵敏度不高、测试范围窄的问题,设计了一系列不同口径的玻璃管(H管)。通过对不同水灰比、不同掺量减水剂条件下水泥浆体的流变特点的对比分析,得到不同H管对应净浆流动度测试范围和减水剂最佳掺量测试方法。H管不仅灵敏度高、测试范围广,而且还可以反映浆体粘度,是一套比较全面准确的水泥浆体流动性测试方法。     

不同黏土对掺减水剂水泥净浆流动度影响

目的 研究4种不同黏土对掺聚羧酸减水剂及萘系减水剂水泥净浆流动度的影响规律并从黏土的吸附性能角度探究其影响机理.方法 采用水泥净浆流动度试验方法比较了4种黏土对掺聚羧酸减水剂水泥净浆流动度的影响,通过TOC总有机碳测试仪测定了4种黏土对聚羧酸减水剂的吸附量.结果 4种黏土对水泥净浆流动度的影响差异较大,其中钙基蒙脱土和钠基蒙脱土的掺量为2％时,掺聚羧酸减水剂水泥净浆已基本没有流动度,掺萘系减水剂的水泥净浆流动度也有所下降,但降幅稍小,而伊利土和高岭土对掺减水剂水泥净浆流动度无明显负面影响;钙基蒙脱土和钠基蒙脱土对聚羧酸减水剂的吸附量较大,伊利土、高岭土对聚羧酸减水剂的吸附能力和水泥相当.结论蒙脱土对掺聚羧酸减水剂水泥净浆流动度负面影响极为严重,而伊利土和高岭土对掺减水剂水泥净浆基本没有负面影响.     

不掺硅粉的活性粉末混凝土配合比试验

在遵循活性粉末混凝土(RPC)基本配制原则的基础上,不掺入硅粉,采用超细水泥、普通水泥、掺合料(粒化高炉矿渣和粉煤灰)、砂、水、减水剂、钢纤维进行配合比试验。试验结果表明:不采用硅粉制备RPC是可行的;在制备RPC时,将超细水泥与适量掺合料混掺后,可以在保证材料强度和流动性的同时提高材料的经济性;用普通水泥取代大部分超细水泥后,材料的性能仍可保证,且更加经济。另外,研究了钢纤维掺量对材料性能(抗压、抗折、流动性及弯曲韧性)的影响规律。     

聚合物纤维对聚苯乙烯颗粒保温砂浆性能的影响

主要研究纤维种类、掺量和长度对EPS保温砂浆抗裂性的影响。结果表明,掺入纤维对EPS保温砂浆有显著的增强作用,其中以聚丙烯纤维增强效果最佳。聚丙烯纤维使EPS保温砂浆收缩率降低,断裂能增大,裂缝指数显著降低,表明EPS保温砂浆抗裂性得到显著改善。聚丙烯纤维的适宜掺量为0.1%,最佳长度范围为12~15 mm。     

高效减水剂与水泥间适应性的研究

在高性能混凝土、商品混凝土中往往会出现高效减水剂与水泥适应性较差的现象,这种现象大多发生在低水胶比、实际用水量较少的高性能混凝土的拌合物中．通过对高效减水剂在不同厂家水泥中的应用研究,来表述对水泥的适应性．通过高效减水剂在不同生产厂家水泥的净浆流动度、不同水泥的砂浆的性能研究表明,与水泥较适应的减水剂在混凝土和砂浆中的掺量较小、强度较高、和易性较好、成本较低;与水泥适应性较差的减水剂,在混凝土和砂浆中的掺量大,成本较高．     

Properties of Chemically Synthesized Nano-geopolymer Cement based Self-Compacting Geopolymer Concrete(SCGC)

The physical and mechanical properties of self-compacting geopolymer concrete(SCGC) using chemically synthesized nano-geopolymer cement was investigated. Nano-geopolymer cement was synthesized using nano-silica, alkali activator, and sodium aluminate in the laboratory. Subsequently, nine nanogeopolymer cement sbased SCGC mixes with varying nano-geopolymer cement content, alkali activator content, coarse aggregate(CA) content, and curing temperature were produced. The workability-related fresh properties were assessed through slump flow diameter and slump flow rate measurements. Mechanical performances were evaluated through compressive strength, splitting tensile strength, and modulus of elasticity measurements. In addition, rapid chloride penetration test, water absorption, and porosity tests were also performed. It was assessed that all mix design parameters influenced the fresh and hardened properties of SCGC mixes. Based on test results, it was deduced that nano-geopolymer cement SCGC performed fairly well. All the SCGC mixes achieved the 28-day compressive strength in the range of 60-80 MPa. Additionally, all mixes attained 60% of their 28-day strength during the first three days of elevated temperature curing. FTIR and SEM analyses were performed to evaluate the degree of polymerization and the microstructure respectively for SCGC mixes.     

自密实混凝土配合比优化研究

自密实混凝土是一种具有高工作性能的高性能混凝土。本文探讨了自密实混凝土工作性能的评定方法,并对掺加磨细矿渣的自密实混凝土进行了研究。通过分析磨细矿渣含量、胶凝材料总量、砂率、减水剂掺量对自密实混凝土流动性和强度的影响,配制了高工作性能和力学性能的自密实混凝土,为掺加磨细矿渣的高强自密实混凝土配合比设计提供了依据。     

再生混凝土ITZ结构与性质的研究

采取降低水灰比 ,掺入适量粉煤灰、高效减水剂和对再生集料表面进行处理等措施 ,通过 SEM研究了再生混凝土界面过渡区 (ITZ)的结构与性质。试验结果显示 :降低水胶比 ,掺入 2 0 %的粉煤灰和 2 .5 %高效减水剂 (对水泥 ) ,可使再生混凝土 ITZ结合更加紧密 ,抗压强度得以提高。在同样条件下 ,采用 1% PVA溶液处理过的再生集料 ,有利于提高新拌再生混凝土的流动性 ,同时 ,硬化混凝土的强度也有所提高     

Uniaxial compressive properties of ultra high toughness cementitious composite

Uniaxial compression tests were conducted to characterize the main compressive performance of ultra high toughness cementitious composite (UHTCC) in terms of strength and toughness and to obtain its stress-strain relationships. The compressive strength investigated ranges from 30 MPa to 60 MPa. Complete stress-strain curves were directly obtained, and the strength indexes, including uniaxial compressive strength, compressive strain at peak stress, elastic modulus and Poisson’s ratio, were calculated. The comparisons between UHTCC and matrix were also carried out to understand the fiber effect on the compressive strength indexes. Three dimensionless toughness indexes were calculated, which either represent its relative improvement in energy absorption capacity because of fiber addition or provide an indication of its behavior relative to a rigid-plastic material. Moreover, two new toughness indexes, which were named as post-crack deformation energy and equivalent compressive strength, were proposed and calculated with the aim at linking up the compressive toughness of UHTCC with the existing design concept of concrete. The failure mode was also given. The study production provides material characteristics for the practical engineering application of UHTCC.