Evaluation of various cellulose ethers performance in ceramic tile adhesive mortars

Eleven cellulose ethers (CE) were selected and tested in a cement based ceramic tile adhesive (CTA) formulation designed to highlight the effect of the CE on the end-use values of the mortars. Results showed that the end-use values, either in the fresh or hardened state, are strongly influenced by the latex powder/CE choice. This is due to the competitive adsorption between these two components; in the fresh state, it affects the CE concentration in the pore solution and hence the viscosity of the mortar, setting time, and skinning. In the hardened state, when CE films do not prevent evaporation at the tile–mortar interface, adhesion in hot curing conditions is lowered compared to dry tensile adhesion values. Test results showed that CTA formulations should be thought of in terms of the CE/latex powder couple, since interactions between this couple and the cement, strongly influence end-use values of the mortar.     

Solid state NMR and LVSEM studies on the hardening of latex modified tile mortar systems

Construction mortars contain a broad variety of both inorganic and organic additives beside the cement powder. Here we present a study of tile mortar systems based on portland cement, quartz, methyl cellulose and different latex additives. As known, the methyl cellulose stabilizes the freshly prepared cement paste, the latex additive enhances final hydrophobicity, flexibility and adhesion. Measurements were performed by solid state nuclear magnetic resonance (NMR) and low voltage scanning electron microscopy (LVSEM) to probe the influence of the latex additives on the hydration, hardening and the final tile mortar properties. While solid state NMR enables monitoring of the bulk composition, scanning electron microscopy affords visualization of particles and textures with respect to their shape and the distribution of the different phases.

Within the alkaline cement paste, the poly(vinyl acetate) (VAc)-based latex dispersions stabilized by poly(vinyl alcohol) (PVA) were found to be relatively stable against hydrolysis. The influence of the combined organic additives methyl cellulose, poly(vinyl alcohol) and latexes stabilized by poly(vinyl alcohol) on the final silicate structure of the cement hydration products is small. But even small amounts of additives result in an increased ratio of ettringite to monosulfate within the final hydrated tile mortar as monitored by ²⁷Al NMR. The latex was found to be adsorbed to the inorganic surfaces, acting as glue to the inorganic components. For similar latex water interfaces built up by poly(vinyl alcohol), a variation in the latex polymer composition results in modified organic textures. In addition to the networks of the inorganic cement and of the latex, there is a weak network build up by thin polymer fibers, most probably originating from poly(vinyl alcohol). Besides the weak network, polymer fibers form well-ordered textures covering inorganic crystals such as portlandite.     

Changes in microstructures and physical properties of polymer-modified mortars during wet storage

The decrease in strength of tile adhesive mortars during wet storage was investigated. In a first approach, the water resistance of the polymer phases was tested on structures isolated from the mortar and in situ. It was observed that cellulose ether and polyvinyl alcohol structures are water-soluble. Subsequent investigations on polymer mobility within the mortar showed that the migrating pore water transports cellulose ether and polyvinyl alcohol during periods of water intrusion and drying. This leads to enrichments at the mortar-substrate interface. In contrast, latices interacting with the cement are water-resistant, and therefore, immobile in the mortar. Further experiments revealed that the mortar underwent considerable volume changes depending on the storage condition. Cracking occurred mainly close to the mortar-tile interface, cement hydrates grew within these shrinkage or expansion cracks. Test results revealed that the strength decrease of wet stored tile adhesives is caused by different mechanisms related to cement hydration, volume changes of the mortar, and reversible swelling of latex films.     

Preparation of a new polymer-modified adhesive mortar using fine iron tailings as aggregate

In this paper, a new polymer-modified adhesive mortar is prepared using the fine iron tailings, eco-cement, redispersible latex powder, additives, and water. In our study, the fine iron tailings are used to replace the natural river sand as the mortar aggregate and the optimal process conditions are determined by the orthogonal experiment. The obtained results are shown as follows: The ratios of cement–sand and polymer–cement are 1:2.5 and 4%, respectively, with the aggregate modulus 0.81 and water reducing agent 0.5% (cement-based). The properties of the polymer-modified adhesive mortar obtained under the optimal process conditions conform to JC/T 547-2005 (China Professional Standard: Ceramic Tile Adhesive). Moreover, the microstructure of the polymer-modified adhesive mortar is studied and discussed. The results show that the network formed by the intertwined polymer film can prevent the merger of micro-cracks and improve the adhesive mortars’ overall cohesion. Therefore, adding polymer to the adhesive mortar can improve its failure stress and enhance its bonding strength.     

苯丙乳液改性水泥修补砂浆的制备与性能研究

采用复配技术制备苯丙乳液改性水泥修补砂浆,并进行性能研究.探讨了聚合物乳液、偏高岭土、煅烧膨润土等外加剂对该砂浆物理性能的影响.结果表明:苯丙乳液的掺入虽然在一定程度上降低了砂浆的抗压强度,但显著改善了水泥砂浆的和易性和需水量.通过掺加偏高岭土或煅烧膨润土等火山灰活性掺合料可弥补砂浆力学性能的不足.     

Latex influence on the mechanical behavior and durability of cementitious materials

The results of an experimental program conducted on latex-modified mortars are presented in this article. These mortars have become of growing interest in the field of construction. They were used as superplasticizers, or water reducers, for finishing work applications and for repairs, coatings, and waterproofing. This study is about using two polymers (latex), i.e. styrene–butadiene rubber and styrene–acrylic, in order to assess their performance in replacing cement in mortars. A series of mortar mixtures, containing 0, 2.5, 5, 10, 15, and 20% of solid polymer latex (by weight), were prepared and tested in the fresh and hardened states. The test parameters include the fluidity, compressive and flexural strengths, porosity accessible to water, adhesion to clay bricks, and cementitious substrates. The experimental results showed that substituting cement into modified mortars improves their fluidity and adhesion. In the case of clay substrates, a cohesive failure occurs within the substrate layer beyond 10% of substitution, while the rupture takes place at the interface for all formulations tested on cementitious substrates. It was also noted that the flexural tensile strength improved beyond 60 days. However, the compressive strength of polymer mortars decreased with the substitution rate of cement, for all maturities considered. However, for porosity accessible to water, the results follow a linear function, with an inflection at 5% of latex substitution.     

氧化淀粉胶粘剂添加助剂的研究

研究了在氧化淀粉胶粘剂中加入一些环保型的高分子助剂,通过对氧化淀粉粘合剂耐水性、粘合强度、稳定性等测试,得出最佳配方,并与白乳胶的性能进行了对比分析。结果表明,加入了PVA的氧化淀粉胶粘剂在各方面的性能测试中均优于其他2种助剂,稳定性好,剥离强度可以与白乳胶相媲美,且粘合强度不受粘接正反面的影响。     

水性环氧树脂改性水泥砂浆力学性能及微观结构

通过对水泥砂浆中掺加水性环氧树脂,制备了水性环氧树脂改性水泥砂浆,研究了不同聚灰比下,水性环氧树脂对水泥砂浆水化和强度的影响.运用XRD、TG/DSC、SEM、FTIR微观测试手段,研究了水性环氧树脂对水泥砂浆水化产物的影响.研究结果表明:水性环氧树脂可形成聚合物膜会延迟水泥水化;水性环氧树脂的加入会降低水泥砂浆的抗压强度;当聚灰比在2％范围以内,水性环氧树脂可以提高水泥砂浆的抗折强度.     

Effect of polymer cement modifiers on mechanical and physical properties of polymer-modified mortar using recycled artificial marble waste fine aggregate

Various polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling. Styrene–butadiene rubber (SBR) latex and polyacrylic ester (PAE) emulsion were employed as polymer modifier, and compared each other. The replacement ratio of AMWFA was also changed to investigate the effect of it on physical properties. Adding polymer cement modifier into mortar reduced water–cement ratio, and PAE was the more effective polymer cement modifier to reduce water–cement ratio than SBR. PAE emulsion-modified mortar increased the air content entrained as the proportion of PAE was increased. There was little difference in water absorption between SBR latex and PAE emulsion. The compressive strength decreased in the presence of polymer cement modifiers compared to that of no polymer cement modifiers, but the compressive strength of 20% of polymer–cement ratio was higher than that of 10%. After the hot water resistance test, both compressive strength and flexural strength were decreased.     

Thermal,mechanical, and surface properties of poly(vinyl alcohol) (PVA) polymer modified cementitious composites for sustainable development

This study aimed to investigate the effect of poly(vinyl alcohol) (PVA) polymer on the thermal, mechanical, and surface properties on cementitious composites for sustainable development. Thermal properties of the PVA‐modified cement paste, including thermal insulation and energy absorption ability, were first studied and correlated with the porosity and microstructures. The experimental results indicated that the thermal conductivity of cement paste can be greatly reduced by 42.9% with 2.0 wt % addition of PVA due to the more porous structure. However, at the same time, more thermal energy can be captured and concentrated at the surface of cement paste with the increasing amount of PVA, causing an increased thermal load and a negative effect on thermal insulating efficiency of cement paste. The contradictory effect of PVA on thermal properties of cement paste should be balanced before it is used as a foaming modifier to fabricate cementitious composites with thermal insulation. In addition, the contact angle measurement revealed that PVA can be used as an effective additive to improve the hydrophobicity of cement‐based materials. Only 3.0% PVA can turn the surface nature from hydrophilicity to hydrophobicity for cement paste, which benefited to the development of self‐cleaning cementitious composites. Finally, the mechanical properties of the PVA‐modified cement paste, especially for the tensile strength that has been rarely reported, were investigated and correlated with its thermal and surface properties. Due to the compensative effects of irregular packing, formation of PVA films and microcracks, tensile strength of cement paste can be improved by 23.5% with a small scarifying of the compressive strength by adding 2.0% of PVA. In conclusion, the PVA‐modified cement‐based materials with lower thermal conductivity, hydrophobic surface nature and enhanced mechanical properties have a great potential to satisfy the high requirements in developing sustainable infrastructure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46177.     

Quantitative distribution patterns of additives in self-leveling flooring compounds (underlayments) as function of application, formulation and climatic conditions

The distributions of organic additives in self-leveling flooring compounds (SLCs) were investigated using laser-scanning microscopy for the selective visualization of the additives, which had been previously stained by a fluorescent dye. The distributions of latex (VC), polycarboxylate ether (PCE), cellulose ether (CE), casein (Cas) and polyvinyl alcohol (PVA, a component of redispersible powders) were analyzed in Portland (PC) and Calcium aluminate cement (CAC) dominated SLC formulations as a function of application thickness and different climatic conditions. It is shown that evaporation induced water flux through the communicating pore system causes considerable enrichments of these additives in the uppermost millimeter of the mortar layer. The resulting fractionation factors can be correlated with the different hydration kinetics of PC or CAC dominated mixed binders as well as with the drying conditions. Investigations on the additive distribution indicate that CAC dominated formulations develop more homogeneous enrichments than PC dominated systems.     

Influence of shrinkage and water transport mechanisms on microstructure and crack formation of tile adhesive mortars

Shrinkage and expansion of cementitious materials like tile adhesive mortars depend on the presence of water as well as on the drying and rewetting history. Particularly for large-sized tiles such volumetric changes induce stress concentrations, which may result in cracking. This study focuses on the interplay between water infiltration and cracking, starting at the early curing of the mortar during the first days after application until water transport in the hardened system. Based on laboratory experiments, different events concerning the effect of water transport were induced by variation of the experimental setups in order to provoke cracking. Cracks at the tile–mortar interfaces suggest these domains to reflect zones of mechanical weakness. Along these cracks, water can enter the system inducing precipitation of secondary minerals in cracks and pores already after one wetting cycle. These processes reveal increasing importance during repeated cycles of drying and wetting, i.e. under outdoor conditions and may lead to failures.     

新型复合早强剂对水泥砂浆力学性能的影响

本文试验研究了两种新型复合早强剂(甲酸钙-晶胚、甲基丙烯酸-晶胚)对水泥砂浆新拌性能和力学性能的影响,并通过X射线衍射仪(XRD)和扫描电子显微镜(SEM)进行了微观分析。结果表明,随着早强剂掺量增加,新拌水泥砂浆的流动度略有降低,凝结时间提前。两种复合早强剂均能够加速水泥早期水化,显著提高水泥砂浆的早期强度。甲酸钙-晶胚、甲基丙烯酸-晶胚两种复合早强剂可使水泥砂浆的12 h抗压强度分别提高96.7%和89.3%,抗折强度分别提高192.2%和211.1%;同时,对水泥砂浆28 d抗压强度的提高幅度仍高达50.0%左右,说明两类早强剂对水泥砂浆后期强度发展无负面影响。XRD和SEM分析均证实,掺两类复合早强剂使水泥水化程度提高,水化产物增多,结构密实度提高。     

The influence of polymers on the hydration of portland cement phases analyzed by soft X-ray transmission microscopy

The soft X-ray transmission microscope, which allows the in situ observation of wet samples of cement at normal pressures with high spatial resolutions (25 nm), was used to observe and compare the effects of two polymers — a water soluble polymer (HPMC — hydroxypropyl methylcellulose) and a latex [EVA-poly(ethylene-co-vinyl acetate)] on the early hydration of C₃S and C₃A. These polymers are used to modify the properties of fresh and hardened mortars and concretes, especially when adhesive characteristics are required. The images show that the cellulose ether delays the hydration of the cementitious particles and promotes the formation of inner products rather than outer products. On the other hand, EVA particles agglomerate around the hydrating C₃S grains, and act as nucleation agents in the development of the composite microstructure. While HPMC slightly changed the aspect of C₃A hydration, EVA inhibited or even prevented the formation of ettringite crystals during the early stage of hydration, and resulted in a cloud of small, bright particles concentrated around the hydrating C₃A grains.     

海水和矿物掺合料对硫铝酸盐水泥砂浆性能的影响

本文研究了不同拌和水以及海水拌和时粉煤灰和硅灰掺量对硫铝酸盐水泥(SAC)砂浆力学性能和表观孔隙率以及净浆凝结时间、化学收缩、孔溶液pH值和氯离子结合能力等的影响,并通过XRD、SEM和EDS分析水泥水化产物和微观结构。结果表明,海水能加快SAC早期水化并提高其早期强度,但后期强度和淡水拌和时无明显差别。粉煤灰和硅灰均会延长SAC凝结时间,对早期抗压强度不利,而掺加质量分数为5.0%和7.5%的硅灰能提高SAC砂浆28 d抗压强度。硅灰掺量增加时会提高用水量和表观孔隙率,降低流动性,使水泥化学收缩增大,降低净浆pH值且减少氯离子结合量;粉煤灰能够提高砂浆流动性,减少水泥化学收缩,但掺量越大对SAC砂浆抗压强度和抗折强度越不利,掺质量分数为10%的粉煤灰可小幅提高氯离子结合量且减小表观孔隙率。     

共混改性EVA水基胶粘剂的制备及其低温粘接性能

以EVA(乙烯-醋酸乙烯共聚物)乳液、PU(聚氨酯)乳液、PVA(聚乙烯醇)溶液和CaCO3为主要原料,制备出一种共混改性EVA乳液胶粘剂。考察了聚合物乳液组成、填料、PVA和使用温度等因素对该乳液胶粘剂的黏度、粘接强度、开放时间和耐水性等影响。结果表明:以DA-103型EVA乳液/U54型PU乳液作为复合基体,当m(EVA乳液)∶m(PU乳液)∶m(PVA溶液)∶m(CaCO3)=18∶27∶30∶25时,相应胶粘剂的低温粘接强度比市售白乳胶提高了50%以上。     

聚丙烯酸酯乳液在水泥砂浆中的应用

为了提高水泥砂浆的韧性,选用了能形成柔性薄膜结构的聚合物--聚丙烯酸酯乳液对水泥砂浆进行改性.研究了聚丙烯酸酯乳液对水泥砂浆体积密度、抗压强度、抗折强度、韧性、动弹模量和黏结抗拉强度的影响.结果表明:聚丙烯酸酯乳液在一定程度上降低了水泥砂浆体积密度和抗压强度,对抗折强度影响较小,改善了水泥砂浆的韧性,并且可提高黏结抗拉强度.当乳液掺量(质量分数)大于5%时,28 d混合养护聚丙烯酸酯乳液水泥砂浆的压折比降低到3以下,只有当乳液掺量大于10%时,水泥砂浆的黏结抗拉强度才明显提高.     

吐温⁃80对PB⁃g⁃PSG乳液改性水泥砂浆性能的影响及作用机理

以聚丁二烯（PB）接枝苯乙烯（St）和甲基丙烯酸环氧丙酯（GMA）为主要原料制备了水泥砂浆改性剂PB?g?PSG乳液,将吐温?80作为稳定剂加入至PB?g?PSG乳液,再将乳液与水泥、标准砂混合制备了改性水泥砂浆;通过扫描电子显微镜（SEM）、水泥胶砂流动度测定仪和激光粒度分析仪等仪器观察了改性水泥砂浆的微观形貌,并研究了吐温?80及PB?g?PSG乳液含量对改性水泥砂浆流动性、力学性能、保水率以及吸水性的影响,同时探讨了吐温?80对PB?g?PSG乳液的作用机理。结果表明,改性水泥砂浆的保水效果优异,保水率的最大值为99.3 %;改性水泥砂浆的吸水质量随吐温?80含量的增加先降后增;改性水泥砂浆的流动性增强,其抗压强度随PB?g?PSG乳液含量的增加而逐渐降低,且小于未改性的水泥砂浆,其抗折强度随PB?g?PSG乳液含量的增加先增后降,且基本高于未改性的水泥砂浆,当PB?g?PSG乳液含量为10 %（质量分数,下同）时,抗折强度最高,为9.52 MPa;PB?g?PSG乳液对水泥水化物具有黏合及桥接作用,二者能够形成互穿网络结构;吐温?80分子结构中的亲水基团能够将水吸附在PB?g?PSG乳液粒子的表面并形成一层很厚的水化层,使乳胶粒子之间被隔离而避免了凝聚的发生。     

外墙外保温系统用粘接砂浆研究进展

介绍了外墙外保温系统用粘接砂浆的性能要求,阐述了无机组分(如水泥、无机填料等)、聚合物添加剂(如可再分散乳胶粉、纤维素醚等)对粘接砂浆性能的影响。总结了目前粘接砂浆的研究成果和存在的主要问题(包括聚合物添加剂相互作用机制尚不明确、提高粘接性能与降低成本之间的矛盾、粘接强度检测方法不一致等)。     

A microstructural approach to adherence mechanism of poly(vinyl alcohol) modified cement systems to ceramic tiles

PVA is a water soluble polymer used as cement modifier. An important modification observed by addition of PVA is the increase of the bond strength between cement paste and aggregate. The purpose of this work was to investigate the effect of PVA on the mechanism of adherence of cement pastes to ceramic tiles. Pastes with and without PVA were applied on the back side of porcelain tiles and after 56 days the microstructures of the interfaces were evaluated by SEM. The mode of rupture changed from mostly interfacial failure to a mixed-mode interfacial-cohesive failure for the paste with polymer addition in which was observed the reduction of the thickness of the porous transition zone between tile and paste bulk. Also, in plain paste the formation of a duplex film (CH plus C-S-H) in contact with tile surface was observed while in modified paste a single layer of C-S-H was identified.