Effects of lignin cellulose and expansive agent on microstructure and macro-property of polymer-modified mortar containing fly ash

The influence of polymer-modified mortar with fly ash was researched, when lignin cellulose and calcium sulphoaluminate expansive agent was added into mortar. The consistency, mechanical properties and shrinkage performance of mortar were studied by orthogonal experiment. Lignin cellulose was wrapped by the hydration products of binding materials. As the expansive agent and fly ash increasing, the consistency of mortar can be improved. Moreover, the influence of cement-based self-leveling material containing fly ash was also studied, when the different quantity of calcium oxide added into the material. The proper added quantity of CaO can largely improve the mechanical property and restrain the shrinkage of self-leveling material.

Construction and Building Materials 23 (2009) 2467–2471 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat Effects of lignin cellulose and expansive agent on microstructure and macro-property of polymer-modified mortar containing fly ash Quan Liuquan a, Li Dongxu a,*, Li Zongjin b a b College of Material Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu 210009, China Department of Civil Engineering, The Hong Kong University of Science and Technology, Hong Kong, China a r t i c l e i n f o Article history: Received 14 July 2007 Received in revised form July 2008 Accepted July 2008 Available online February 2009 Keywords: Microstructure Macro-property Variance analysis Lignin cellulose Expansive agent Polymer-modified mortar a b s t r a c t The influence of polymer-modified mortar with fly ash was researched, when lignin cellulose and calcium sulphoaluminate expansive agent was added into mortar The consistency, mechanical properties and shrinkage performance of mortar were studied by orthogonal experiment Lignin cellulose was wrapped by the hydration products of binding materials As the expansive agent and fly ash increasing, the consistency of mortar can be improved Moreover, the influence of cement-based self-leveling material containing fly ash was also studied, when the different quantity of calcium oxide added into the material The proper added quantity of CaO can largely improve the mechanical property and restrain the shrinkage of self-leveling material Ó 2009 Published by Elsevier Ltd Introduction Shrinkage of cement-based material is due to the loss of capillary water in the process cement harden, main including dry shrinkage due to water evaporation and spontaneous shrinkage due to chemical shrinkage [1] When the shrinkage stress reaching the some extent, cement-based material generate crack, so that the mechanical property and durability would become bad When fiber added into cement-based material, the amount of crack will be significant reduced, meanwhile, the anti-crack, ductility and durability of material will be significant improved [2,3] At present, there are lots of researches about cement-based material with fibers, these fibers including: nylon, polyethylene, polyamide fiber, polyester fiber and so on [4,5] Fly ash is the type of admixture material possessing potential hydration activity Expansive agent is chemical material that can react with cement and else gel, finally produce new substances that can increase the volume of plaster [6,7] The research of lignin cellulose added into polymer-modified mortar, especially the research of polymer-modified mortar containing fly ash with both lignin cellulose and expansive agent is few In view of this, the performances of polymer-modified mortar with different quantity of expansive agent, fly ash and lignin cellulose were studied in the paper, moreover, the influences of cement-based self-leveling material containing fly ash were researched, when added calcium * Corresponding author Tel.: +86 25 83587258; fax: +86 25 83588967 E-mail address: dongxuli@njut.edu.cn (L Dongxu) 0950-0618/$ - see front matter Ó 2009 Published by Elsevier Ltd doi:10.1016/j.conbuildmat.2008.07.005 oxide Cement-based self-leveling material also belongs to polymer-modified mortar Materials and methods 2.1 Raw materials Lignin cellulose (length is about 250 lm); calcium oxide expansive agent and calcium sulphoaluminate expansive agent; methyl hydroxyethyl cellulose ether (H300P2); redispersionable glue-powder (FL32); fly ash (the value of screen residue is 0.4%, 0.08 mm); 52.5 grade Portland cement; fine sand and superfine sand; calcium lignosulfonate reducing agent; antifoamer The chemical composition of cement and fly ash were showed Table 2.2 The orthogonal experiment of polymer-modified mortar The experiments were adopted by orthogonal design [8] Orthogonal experiment is arranged many influence shows the mixing proportions of self-leveling material adding calcium oxide The flowability, shrinkage and 24 h strength of self-leveling material was tested by the Chinese standard JC/T985-2000 (cementitious self-leveling floor mortar) Results and discussion (33), the experiment scheme was arranged, the programs of composition of mortar were showed in Table L9 (33) means that the number of levels and factors were separate three, and the number of experiment group was nine      Cement preparation of mixes and of the drying process (2 days at 60 °C) In order to obtain the original interfacial structure of images, the polished treatment was not adopted After metallization, the sections were examined in a SEM, where the secondary electrons mode was used for imaging: compositions appear in white, and pores in blank Table L9(33)The programs of composition and the testing results eẳ Serial number 1ị The results of experiments were analyzed by variance analysis Table shows the added dosage of expansive agent, lignin cellulose and fly ash can have some influence on the consistency of mortar The consistency of mortar can be improved by increasing the added dosage of expansive agent and fly ash But lignin cellulose has bad effect on the consistency of mortar The optimum mix proportion was M7 based on their consistency, from the results of experiments The added dosage of fly ash and expansive agent were more, but the added dosage of lignin cellulose was less in M7 than others The consistency of mortar can be improved by adding with fly ash The addition of fly ash can improve the fluidity of cement paste, showing a water-reducing effect [10] The physical and chemical characteristics of the fly ash, such as the grain morphology, volcanic glass structure, density, specific area, and grain diameter, have great influence on the water-reducing effect of mortar There were lots of spherical grains (glass micro bead) in fly ash But cement grains was irregular geometrically These glass micro beads play balls role in cement grains The resistance of slippage of cement grains was reduced, so that the consistency of mortar was increased The lignin cellulose was short rod structure, the length was about 250 lm When lignin cellulose mixed with plaster, they splice graft each other, so that lignin cellulose has bad effect on the consistency of mortar The testing of mortar consistency was finished in very short time, after added water into mixture Therefore, the physics structure of materials makes great- Annotate e – the shrinkage ratio of cement mortar (10À4) L0 – the initial length of mortar specimens (mm) Lt – the length of mortar specimens every curing age (mm) 280 – the effective length of mortar specimens (mm) 2.4 The SEM of polymer-modified mortar An approach of the microstructure can be made by means of image analysis For this purpose, images were obtained in three steps: the preparation of plaster specimens, the acquisition of images in the SEM, and the processing of images to obtain binary images by thresholding Specimens were obtained with a controlled time of Table Variance analysis of consistency Expansive agent Lignin cellulose Fly ash Error Sum * SS Degree of freedom MS F Significance 239.628 625.360 39.979 116.797 1021.765 2 2 119.8142 312.6800 19.9896 58.3987 2.05166 5.35423 0.34230 * Show relatively significance influence factor * * 2469 Q Liuquan et al / Construction and Building Materials 23 (2009) 2467–2471 Table Variance analysis of flexural strength Expansive agent Lignin cellulose Fly ash Error Sum * SS Degree of freedom MS F Significance 1.70042 0.18389 1.43429 0.19876 3.51736 2 2 0.85021 0.09194 0.71714 0.09938 8.55534 0.92520 7.21635 * * * Show relatively significance influence factor 3.2 Results of shrinkage of polymer-modified mortar Table Variance analysis of compressive strength Expansive agent Lignin cellulose Fly ash Error Sum * ** Al2O3 can react with Ca(OH)2, produced hydraulicity gel The effect of expansive agent and fly ash can exert, only when expansive agent and fly ash react with Ca(OH)2 In the experiments, the mortar specimens were made by adding fly ash and expansive agent, which equivalent replaced cement When the added dosage of fly ash and expansive agent to some degree, the quantity of Ca(OH)2 is not enough, expansive agent and fly ash effect would be not preferable exerted SS Degree of freedom MS F Significance 50.18002 2.96949 32.28336 1.82802 87.26089 2 2 25.09001 1.48474 16.14168 0.91401 27.45044 1.62443 17.66026 ** * Show relatively significance influence factor Show significance influence factor er influence on the consistency of mortar than the chemical property of materials The fineness of expansive agent was very large When mixed with other materials, expansive agent fills in both cement grains and fly ash grains The grain distribution of gel material was meliorated, so that the consistency of mortar was improved Table shows expansive agent, lignin cellulose and fly ash have some influence on the flexural strength of mortar Table shows according to the effects of composition on compression strength, expansive agent was significance influence factor Fly ash was relatively significance factor Both flexural strength and compression strength of M7 were biggest in all programs of composition Increasing the dosage of fly ash or expansive agent has bad effect on the flexural strength and compression strength of mortar Table shows when the interaction of both expansive agent and fly ash being considered in variance analysis, both expansive agent and fly ash played significance role on mechanical property of mortar Moreover, the interaction of both expansive and fly ash was relatively significance factor also There was alunite, gypsum and so on in calcium sulphoaluminate expansive agent These chemical substances can react with Ca(OH)2, producing AFm and AFt Fly ash is pozzolanicity admixture and have potential activity, SiO2 and The shrinkage ratios of polymer-modified mortar are showed in Table The shrinkage ratios of mortar specimens were analyzed by variance analysis The research results show that significance factors were alteration as the shrinkage of mortar specimens at different curing age In response to the seventh day shrinkage ratios of mortar s specimens, three influence factors (expansive agent, lignin cellulose, fly ash) were all not significance However, according to the 14th day shrinkage ratios of mortar specimens, three influence factors were all significance influence factor The phenomenon was largely related to the property of added materials [11] Fly ash was the type of admixture material possessing potential hydration activity In the prior period of hydration, the hydration ability and surface energy of fly ash was low, the inter-particles water was easy evaporated, so that the dry shrinkage of mortar with fly ash was larger In the final period of hydration, fly ash take part in hydration with Ca(OH)2, which coming form the cement hydration [12] With the help of fly ash hydration, on the one hand, the carbonization shrinkage was reduced, on the other hand, the characteristics of mortar interface become dense, the loss of water was reduced and the dry shrinkage ratio of mortar were decreased [13] So that the ratio shrinkage of mortar containing fly ash was less than normal mortar’s in the final period There was alunite, gypsum and so on in expansive agent These compositions can react with cement hydration product, producing possess of expansibility ettringite The expansive effect of expansive agent was largely related to the quantity of cement hydration products In the prior period of cement hydration, the quantity of cement hydration products was relatively few, So that the effect of expansive agent was not exerted In the final period of cement hydration, the quantity of Ca(OH)2 was few also, because Ca(OH)2 reacted with fly ash, the effect of expansive agent was weakened The phenomenon was certified by variance analysis of the 28th day shrinkage ratios, the expansive agent was not significance factor at the curing age According to 14th day shrinkage ratios of mortar specimens, lignin cellulose was significance factor Lignin cellulose was wrapped by the cement hydration products The shrinkage and expansion of mortar was controlled by the cohesive stress of between lignin cellulose and the hydrate of cement Table Variance analysis of flexural strength when the interaction of both expansive agent and fly ash was considered Expansive agent Lignin cellulose Fly ash Interaction Error Sum * ** SS Degree of freedom MS F Significance Table The shrinkage ratios of polymer-modified mortar (10À4) 1.70042 0.85021 354.2546 ** Serial number 7d 14d 21d 28d M1 M2 M3 M4 M5 M6 M7 M8 M9 2.29 0.64 À0.78 0.22 0.42 1.41 2.63 2.20 À0.05 2.33 À2.15 À1.36 À0.38 À0.71 2.48 0.29 2.27 À0.69 1.55 0.78 À1.98 À1.83 0.52 2.38 0.23 2.17 À0.60 3.14 1.26 À0.86 À1.49 À0.91 2.90 0.25 2.57 0.01 0.28722 0.14361 59.8374 1.43429 0.19635 0.00240 3.51736 1 0.71714 0.19636 0.00240 298.8102 81.8148 Show relatively significance influence factor Show significance influence factor * ** * 2470 Q Liuquan et al / Construction and Building Materials 23 (2009) 2467–2471 3.3 The SEM of polymer-modified mortar Fig 1a shows that lignin cellulose (A) and aggregates (B) were wrapped by the hydration products of binding material (C) The bond of lignin cellulose and cement mortar matrix was better There was a good agreement with the result of Fig 1b Fig 1a also shows that there were a lots of C–S–H gel on the surface of aggregates There was appreciable variance the microstructure of both pure cement mortar matrix and cement mortar matrix with fly ash [14] There were lots of needle-volume hydration products in the pure cement mortar matrix The microstructure of pure cement mortar matrix was relatively loose The bond of needle-volume hydration products was little Fig 1c shows that there were dense flocculent gel in cement mortar matrix with fly ash, and the bond of the gel 3.4 Study of the property of cement-based self-leveling material The results of flowability and mechanical property were showed Table 10 When the added quantity of calcium oxide was below 1%, the flowability of the material was better than normal material’s However, the added quantity of calcium oxide was more than 1%, as the added quantity of calcium oxide increasing, the flowability of material become badly The added quantity of calcium oxide had not largely related to the material flowability loss, moreover, in some material mixing proportions, the 20 min’s flowability of materials were better than the initial flowability Table 10 shows as the added quantity of calcium oxide increasing, even though the added quantity of calcium oxide was very low, the mechanical property of cement-based self-leveling material can be largely improved When the added quantity of calcium oxide was 1%, the flexural strength can improved 2.05 times than normal material, and the compression strength can improved 1.92 times After fly ash grinded, glass structure of fly ash was destroyed, active SiO2 was exposed from glass structure and the surface area of fly ash was increased also This is due to grinded fly ash that exhibits pozzolanic properties and packing effect These characteristics tend to improve mortar strength as well as its density [15] The active SiO2 can react with Ca(OH)2, produced hydraulicity gel [16] As a result that calcium oxide can produce lots of Ca(OH)2 in relatively short time, the self-leveling material added CaO can produce more hydraulicity gel than self-leveling material nonadded CaO The early mechanical property of cement-based selfleveling material can be largely improved Table 11 shows as the added quantity of calcium oxide increasing, the shrinkage ratios of material were reduced When the added quantity of calcium oxide was 6%, the self-leveling material appears slightly expanse When cement clinker react with water, the absolute volume of the system of cement–water is decreased, Table 10 The testing results of flowability and mechanical of self-leveling material Serial number Flowability (cm) 20 flowability (cm) Flexural strength (MPa) Compression strength (MPa) 11.7 12.7 11.0 10.2 10.3 8.5 8.0 12.0 12.4 12.3 10.0 9.1 9.1 9.6 0.38 0.78 1.25 1.35 1.90 2.09 2.05 1.3 2.5 3.6 5.0 7.2 6.7 7.7 Table 11 The ratios of shrinkage of self-leveling material (%) Fig SEM micrographs of the plasters Serial number 7d 14d 21d 28d À0.183 À0.168 À0.132 À0.112 À0.086 À0.044 0.166 À0.210 À0.185 À0.191 À0.146 À0.158 À0.065 0.090 À0.232 À0.220 À0.218 À0.180 À0.162 À0.122 0.026 À0.224 À0.218 À0.258 À0.222 À0.195 À0.133 0.020 Q Liuquan et al / Construction and Building Materials 23 (2009) 2467–2471 the phenomenon was said chemical shrinkage of material In the hydration progress of cement, the shrinkage ratio of material increased When calcium oxide added into cement-based self-leveling material, calcium oxide reacted with water, producing Ca(OH)2 In the progress, the volume of product increased 1.98 times than calcium oxide’s The hydration rate of calcium oxide was quick, so that the expanse effect of calcium oxide has greater influence than the chemical shrinkage of cement hydration in the prior period of hydration The early shrinkage ratios of self-leveling material containing calcium oxide appeared relatively small Conclusions As expansive agent and fly ash increasing, the consistency of polymer-modified mortar can be improved Lignin cellulose has bad effect on the consistency of polymer-modified mortar When fly ash and calcium sulphoaluminate expansive agent were added into mortar together, fly ash have not obvious effect on the final strength of mortar, at the same time, the expanse effect of expansive agent was also restricted This was not good idea that both fly ash and calcium sulphoaluminate expansive agent were added into mortar together Lignin cellulose not only has advantage on the strength of polymer-modified mortar, but also can effective control the shrinkage property of polymer-modified mortar The proper added quantity of CaO can largely improve the mechanical property and restrain the shrinkage of material Acknowledgments The authors gratefully acknowledge the financial support for this research from the National Basic Research Program of China (2001CB610703) and a National Starch & Chemical Business 2471 References [1] Chindaprasirt P, Honwuttiwong S, Sirivivatnanon V Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar Cem Concr Res 2004;34:1087–92 [2] Toutanji Houssam A Properties of polypropylene fiber reinforced silica fume expansive-cement concrete Constr Build Mater 1999;13:171–7 [3] Haddad Rami H, Smadi Mohammed M Role of fibers in controlling unrestrained expansion and arresting cracking in Portland cement concrete undergoing alkali-silica 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investigation on microstructure of cement paste containing fly ash and silica fume Cem Concr Res 2002;32:1131–2  ... stress of between lignin cellulose and the hydrate of cement Table Variance analysis of flexural strength when the interaction of both expansive agent and fly ash was considered Expansive agent Lignin. .. effect of expansive agent and fly ash can exert, only when expansive agent and fly ash react with Ca(OH)2 In the experiments, the mortar specimens were made by adding fly ash and expansive agent, ... and compression strength of M7 were biggest in all programs of composition Increasing the dosage of fly ash or expansive agent has bad effect on the flexural strength and compression strength of