聚合物改性水泥基材料研究进展

讨论了聚合物改性水泥基材料的历史、性能及改性机理。从力学性能及韧性、耐久性两方面说明了聚合物改性水泥基材料性能,从微观形貌、孔结构和聚合物与水泥基体的作用三方面详细讨论改性机理。最后,对聚合物改性水泥基材料的发展趋势进行了讨论。     

水泥基聚合物防水材料的研究进展

从杂链聚合物、元素有机聚合物和无机高分子3方面介绍了水泥基聚合物防水材料的作用机理及应用情况,同时从机理、性能、合成和改性这4方面概括了国内外的研究进展,并对水泥基聚合物防水材料的发展进行了展望。     

有机/无机复合水泥基材料研究进展

论述了有机／无机复合材料的发展历史、现状及发展方向和应用，特别是详尽地论述了有机物对水泥的改性机理，指出聚合物改性水泥基材料应向多元化、轻质多孔、早强快硬、自流平、凝结时间可调节及环保型复合材料的方向发展。由于聚合物改性水泥基材料的优良性能，随着石油化工的发展，应在我国大力推广这种有机／无机复合水泥基材料。     

胶乳改性水泥基材料的机理研究进展

综述了胶乳改性水泥基材料的机理在国内外研究进展。对胶乳改性水泥基材料的机理从理论角度进行了归纳与总结,主要从4个方面讨论了改性机理:在水泥水化过程胶乳具有物理作用和化学作用;在微观结构方面,胶乳中的乳胶粒子具有分散作用且能够形成乳胶膜;从孔洞结构看,胶乳能够改变水泥基材料的孔径分布、特征孔径、平均孔径、最可几孔径、孔隙率等,提高了材料的内聚强度;从胶乳自身结构来看,其链结构和聚集态结构对水泥基材料的性能具有重要作用。     

碳基材料对水泥基材料性能的影响

水泥基复合材料凭借其原料丰富、价格低廉、生产工艺简单、强度高等优点,广泛应用于现代化工程建设.但是这种材料长久以来都有高脆性以及裂缝等一系列的问题.针对这些问题世界各国的研究人员都主要致力于改善水泥基材料的力学性能.但是在目前的情况下,现代建筑对水泥基材料提出了许多新的要求,不仅要有好的力学行为,还要具有尽可能多的附加功能.合适的功能填料的掺入不仅能够使得水泥基复合材料的力学性能和耐久性能得到提升,还能有效地调控水泥基材料的导电率、热导率等一系列其他功能.钢纤维、聚合物纤维和矿物纤维等是之前比较常见的功能掺料,这些材料依靠它们的强度和韧性可以用来改善材料的力学性能.但这些增强材料并不能在结构上改变水泥的水化产物,因此水泥基材料的高脆性及裂缝等问题依存在.而部分碳基材料在掺入到水泥基复合材料中以后可以对水泥基材料实现改性,不仅能从微观方面改变其结构,从而改善力学性能,还可以改善如导电性、导热性等性能.使水泥基复合材料能够尽可能地满足时代的要求.本文在近年来对多种不同的碳基材料掺杂水泥基复合材料研究的基础上,分别总结了不同碳基材料(碳纤维CF、碳黑CB、碳纳米管CNTs、石墨烯GR以及氧化石墨烯GO)对水泥基复合材料性能影响的基本原理,综述了近年来五种材料掺加在水泥基复合材料中的相关研究.此外,本文同时也对这些材料的复合掺入以及互相之间的改性掺入后的效果进行了简单总结,并且同时对水泥基复合材料的研究前景提出了一点看法.     

聚合物基石墨烯纳米复合材料的研究进展

综述了聚合物基石墨烯及改性石墨烯纳米复合材料的研究进展.添加少量的石墨烯就可以显著提聚合物材料的各方面性能,因此,近年来石墨烯得到了学术界和工业界的高度关注,石墨烯、氧化石墨烯的改性,以及聚合物基石墨烯纳米复合材料被广泛研究.通过广泛的文献阅读对聚合物基石墨烯纳米复合材料的结构、制备方法以及性能进行了深入探讨.     

先进水泥及先进水泥基材料的研究进展

介绍了有关先进水泥和先进水泥基材料的探索和研究进展。消纳工业废渣的低环境负荷水泥技术、高胶凝性高钙水泥熟料体系的研究、高贝利特水泥的研究和应用、地聚合物的深入开发等成果反映了我国在水泥科学领域的突破。水泥基材料的研究进展主要体现在多因素协同作用下水泥基材料性能劣化和寿命预测的研究、大流动度自流平混凝土的研究、改善水泥基材料体积稳定性的研究、高延性纤维增强水泥基复合材料的研究方面。水泥和水泥基材料近期研究重点将主要集中在与节能减排、环保利废有关的新设备、新材料和新技术方面;水泥基材料的抗裂性和耐久性,功能性复合材料的开发也将是研究的重点。     

生土材料国内外研究进展

详细综述了生土材料在物理力学性能、改性理论与措施、耐久性和功能化方面的国内外研究进展,探讨了石灰、水泥、纤维以及复合改性方法等对生土材料性能的影响及各自的改性机理,分析了目前生土材料研究和应用中存在的问题,结合笔者的研究提出了可适时崩解回归自然的改性生土材料的设计思路.     

水泥基材料裂缝自愈合的研究进展

总结了近些年来在水泥基材料裂缝自愈合领域的研究进展，重点论述了两种普通类型的水泥基材料裂缝自愈合的机理、愈合过程、影响因素及评价。普通水泥基材料裂缝愈合机理包括结晶沉淀、结晶渗透，对聚合物水泥基材料，主要包括空气固化愈合、热聚合愈合和温致愈合机理。并提出了进一步的研究方向。     

碳纳米管分散技术及碳纳米管-水泥基复合材料研究进展

应用碳纳米管(Carbon nanotubes,CNTs)对水泥基材料进行改性,能大幅度提高水泥基材料的抗折强度。综述了碳纳米管复合材料的国内外研究进展,主要探讨碳纳米管的分散技术,分析碳纳米管对水泥基材料性能的提高以及最佳掺入量,简要介绍了碳纳米管定向排列的研究进展。还指出了当前研究中存在的问题,并就今后的研究前景提出了一些建议。     

聚合物改性水泥基修补材料的研究现状及发展措施

综述了工程修补材料的基本情况,分别介绍了无机类、有机类、有机改性类修补材料的研究现状,并探讨了聚合物乳液在修补材料中的应用潜力。重点论述了常用于聚合物改性水泥基修补材料中的环氧乳液、丁苯乳液、丙烯酸系乳液和醋酸乙烯酯共聚物等聚合物乳液的特性及其应用现状,并就聚合物改性水泥基修补材料的发展中所面临的主要问题提出了若干建议。     

Review and discussion of polymer action on alkali–silica reaction

This paper compares the factors known to influence the deleterious alkali–silica reaction in concrete with the properties that polymers tend to modify in cementitious materials. A discussion on the potential ASR-influencing mechanisms of polymer additions is provided, along with a critical review of the existing literature on the subject. The influence of the potentially significant differences in mechanical properties and sorptivity between polymer-modified and unmodified cementitious materials on the expansion results of alkali reactivity tests is also discussed. According to the available results, the influence of polymers on ASR-related expansion seems to depend on both polymer type and dosage, suggesting the existence of concurrent, not yet well understood mechanisms by which polymers may influence ASR-related expansion. As polymer modification of cementitious materials can lead to significantly lower modulus of elasticity, higher tensile strength and resistance to microcracking, it is suggested that further research on the subject includes not only expansion tests but also an assessment of the resistance of polymer-modified cementitious materials to ASR-related damage, the main concern due to this deleterious phenomena.     

Micromechanics-based investigation of the elastic properties of polymer-modified cementitious materials using nanoindentation and semi-analytical modeling

Cementitious materials are modified by the addition of polymers in order to improve the durability and the adhesive strength. However, polymer-modified mortars and concretes exhibit lower elastic moduli in comparison to unmodified systems. The macroscopic properties are governed by microstructural changes in the binder matrix, which consists of both cementitious and polymer components. Herein, different polymer-modified cement pastes were characterized using nanoindentation to better understand the microscopic origin of the macroscopic elastic modulus. By means of the statistical nanoindentation technique, the existence of three micromechanical phases in plain and polymer-modified cement pastes with a water-to-cement mass ratio of 0.40 is evidenced, illustrating that the polymer modification does not induce the formation of additional reaction products. Instead, the polymers adsorb on the hydration products as well as on unhydrated clinker grains and decrease the indentation moduli of the micromechanical phases. The link between the microscopic and macroscopic mechanical properties is established by means of a continuum micromechanics approach. A multiscale model aimed at the prediction of the elastic moduli of polymer-modified cementitious materials is developed with input parameters that are partially obtained from the nanoindentation tests. The comparison of the modeling results with the experimentally determined elastic (macroscopic) moduli at the scales of cement paste, mortar, and concrete is satisfactorily good, underlining the predictive capability of the modeling approach. The improvement of prediction models is essential for the application of polymer-modified cementitious materials in construction and will encourage their integration into design guidelines.     

From microstructure to macrostructure: an integrated model of structure formation in polymer-modified concrete

A model is proposed for the formation of the microstructure in polymer-modified cementitious materials. Cement hydration and polymer film formation were studied, with specific emphasis on the synergetic effect between cement particles and polymer particles. Alterations at the microstructure level result in macroscopic changes in the properties of the modified material. In this paper, the influence of the polymer addition on the appearance of the cement hydrates and the presence of the polymer film through the cement hydrates are presented in relation to the minimum film forming temperature. Owing to the presence of the cement particles and to cement hydration, film formation can take place at lower temperatures, so that a polymer dispersion with a slightly higher MFT (minimum film forming temperature) can be used. This is important for the physical and mechanical properties of the polymer-modified materials. The findings have been included in an integrated model based on the three-step model of Ohama, in which the polymer film formation and the cement hydration processes are integrated in relation to each other. A time-dependent evaluation of both processes was incorporated. The research presented in this paper was part of a PhD research at the Civil Engineering Department, University of Leuven, Belgium [1].     

Efficiency of RC square columns repaired with polymer-modified cementitious mortars

This paper regards the axial behavior of reinforced concrete columns repaired by polymer-modified cementitious mortars. Tests were performed on eight columns with square cross-section: six were repaired with three types of polymer-modified cementitious mortars on all faces, two were in non-damaged and non-repaired condition (control elements). Tests were repeated varying mechanical properties (elastic modulus and compressive strength) of repair materials, maintaining the same repair thickness, including the reinforcement bars. Comparisons between repaired and control elements showed that polymer-modified cementitious mortars cannot restore the original load-bearing capacity of columns. In spite of this, selection of mortar mechanical properties plays a significant role. Among the three types of repair mortar tested in this experimental study, using the material with the most similar elastic modulus and higher compressive strength than that of the concrete substrate is recommended.     

Effect of hot-dry curing environment on the intrinsic properties of repair materials

The paper examines the properties of five different types of repair materials, including conventional cementitious, polymer and polymer-modified repair mortars. Assessment was carried out on the basis of the engineering properties (compressive strength, tensile strength and modulus of elasticity), pore structure (porosity and pore size distribution), transport properties (permeability and diffusion) and shrinkage. These properties were measured up to the age of 28 days after curing in a hot-dry environment.

The epoxy resin repair mortar showed superior strength and transport characteristics with a very fine pore structure; however, its modulus of elasticity was remarkably low when compared with that of normal- and high-strength concretes. A hot-dry curing environment adversely affects the shrinkage and performance-related properties of conventional repair mortars; however, small improvements could be achieved by the use of mineral admixtures (fly ash and silica fume). The paper discusses also the different testing techniques which could be used to assess the potential performance of concrete repair mortars.     

Compatibility of repair mortars with concrete in a hot-dry environment

Strengthening, maintenance and repair of concrete structures are becoming more recognised in the field of civil engineering. There is a wide range of repair mortars with varying properties, available in the market and promoted by the suppliers, which makes the selection of the most suitable one often difficult. A research programme was conducted at Leeds University to investigate the properties of cementitious, polymer and polymer modified (PMC) repair mortars. Following an earlier publication on the intrinsic properties of the materials, this paper presents results on the compatibility of these materials with concrete. The dimensional stability is used in this study to investigate the compatibility of the repair mortars and the parent concrete. Composite cylindrical specimens (half repair mortar/half concrete) were prepared and used for the measurements of modulus of elasticity and shrinkage. The results of the different combined systems were obtained and compared to those calculated using a composite model. The variations between the measured and calculated values were less than 10%. The paper attempts to quantify the effect of indirect differential shrinkage on the permeability and diffusion characteristics of the different combined systems.     

聚合物改性沥青的研究进展

介绍了目前聚合物改性沥青的研究进展,包括改性聚合物种类、聚合物改性机理及其性能评价方法,并阐述了聚合物改性沥青技术的发展趋势.     

Mechanism of a vegetable waste composite with polymer-modified cement (VWCPMC)

In search for improved construction materials and techniques, two main factors must be taken into account: ecological impact and production costs. The incorporation of recycled materials originating from renewable sources into cementitious cores is a feasible alternative that has gained ground in civil construction. This study investigated the matrix of a vegetable waste composite with polymer-modified cement. Several mixtures composed of Slag-Modified Portland cement, treated vegetable residue, wood from the Pinus caribaea species, latex type polymer, styrene–butadiene rubber (SBR) and an adequate water ratio for the mixtures were studied. The composite was characterized based on mortar tests carried out according to ABNT norms to determine its mechanical behavior, workability and water absorption by capillarity. Some of the essential properties of mortars, such as workability, mechanical strength and durability were substantially altered by the addition of polymers when compared to mortars without this addition. The effect of reduced capillary pores resulting from the action of the polymer contributed to decrease in the permeability of the material, preventing the penetration of aggressive agents due to the phenomenon of water transport. The composite containing vegetable residues and SBR-modified core presented the best mechanical behavior, and an increase of the polymer content resulted in greater water retention in the fresh mixture and a significant reduction in porosity.