Carbon nano tubes (CNT) has been introduced as an efficient nanomaterial in order to improve the mechanical and durability properties of concrete. The effect of CNT on the microstructures of cementitious materials has been widely reported. This paper combines a critical review on the effect of CNT on the pore and microstructure of cement composite with a discussion on the porosity measurement of pastes containing CNT using mercury intrusion porosimetry techniques (MIP). It was found that, surface treatment by H2SO4 and HNO3 solution forms carboxyl acid groups on CNTs’ surfaces that lead to the improvement of reinforcement. In this scope, this review paper involves analyzing the effect of CNT on the microstructure and the pore structure of cementitious materials. The existing methods of measuring the porosity of cementitious material are reviewed, in particular, the contact angle measurement is discussed in detail in which the most effective parameters and possible errors of calculation is presented.
. [J]. Frontiers of Structural and Civil Engineering, 2018, 12(1): 137-147.
S.A. GHAHARI, E. GHAFARI, L. ASSI. Pore structure of cementitious material enhanced by graphitic nanomaterial: a critical review. Front. Struct. Civ. Eng., 2018, 12(1): 137-147.
Olivier J, Janssens-Maenhout G, Muntean M, Peters J. Trends in global CO2 emissions: 2015 Report. PBL Netherlands Environmental Assessment Agency, 2015, report number: JRC 98184
2
Marceau M, Nisbet M A, Van Geem M G. Life cycle inventory of portland cement manufacture. Portland Cement Association Skokie, 2006, PCA R&D Serial No. 2095b
3
Ramezanianpour A A, Ghahari S A, Esmaeili M. Effect of combined carbonation and chloride ion ingress by an accelerated test method on microscopic and mechanical properties of concrete. Construction & Building Materials, 2014, 58: 138–146 https://doi.org/10.1016/j.conbuildmat.2014.01.102
4
Heikal M, Abd El Aleem S, Morsi W M. Durability of composite cements containing granulated blast-furnace slag and silica nano-particles. Indian Journal of Engineering and Materials Sciences, 2016, 23(1): 88–100
5
Abd El. Aziz M, Abd El. Aleem S, Heikal M, El. Didamony H. Hydration and durability of sulphate-resisting and slag cement blends in Caron’s Lake water. Cement and Concrete Research, 2005, 35(8): 1592–1600 https://doi.org/10.1016/j.cemconres.2004.06.038
6
Ghahari S A, Ramezanianpour A M, Ramezanianpour A A, Esmaeili M. An accelerated test method of simultaneous carbonation and chloride ion ingress: durability of silica fume concrete in severe environments. Advances in Materials Science and Engineering, 2016, 2016: 1650979 https://doi.org/10.1155/2016/1650979
7
Assi L, Ghahari S A, Deaver E E, Leaphart D, Ziehl P. Improvement of the early and final compressive strength of fly ash-based geopolymer concrete at ambient conditions. Construction & Building Materials, 2016, 123: 806–813 https://doi.org/10.1016/j.conbuildmat.2016.07.069
8
Ahlborn T. Sustainability for the concrete bridge engineering community. ASPIRE, 2008, 15–19
9
Ramezanianpour A A, Ghahari S A, Khazaie A. Feasibility Study on Production and Sustainability of Poly Propylene Fiber Reinforced Concrete Ties Based on a Value Engineering Survey. In: The 3rd International Conference on Sustainable Construction Materials and Technologies (SCMT3). 2013. Coventry University, University of Wisconsin
10
Ramezanianpour A M, Esmaeili K, Ghahari S A, Ramezanianpour A A. Influence of initial steam curing and different types of mineral additives on mechanical and durability properties of self-compacting concrete. Construction & Building Materials, 2014, 73: 187–194 https://doi.org/10.1016/j.conbuildmat.2014.09.072
11
Mackechnie J R, Alexander M G. Using durability to enhance concrete sustainability. Journal of Green building, 2009, 4(3): 52–60
12
Abd El-aleem Mohamed S, Abd El-rahman Ragab Khalil. Physico-mechanical properties and microstructure of blended cement incorporating nano-silica. International Journal of Engineering Research and Technology, 2014, 3(7): 339–358
13
Abd El. Aleem S, Heikal M, Morsi W M. Hydration characteristic, thermal expansion and microstructure of cement containing nano-silica. Construction & Building Materials, 2014, 59(0): 151–160 https://doi.org/10.1016/j.conbuildmat.2014.02.039
14
Heikal M, Abd El-Aleem S, Morsi W M. Characteristics of blended cements containing nano-silica. HBRC Journal, 2013, 9(3): 243–255 https://doi.org/10.1016/j.hbrcj.2013.09.001
15
Ghafari E, Costa H, Júlio E, Portugal A, Durães L. The effect of nanosilica addition on flowability, strength and transport properties of ultra high performance concrete. Materials & Design, 2014, 59: 1–9 https://doi.org/10.1016/j.matdes.2014.02.051
16
Ghafari E, Costa H, Júlio E. Critical review on eco-efficient ultra high performance concrete enhanced with nano-materials. Construction & Building Materials, 2015, 101(Part 1): 201–208 https://doi.org/10.1016/j.conbuildmat.2015.10.066
17
Lu L, Ouyang D, Xu W. Mechanical properties and durability of ultra high strength concrete incorporating multi-walled carbon nanotubes. Materials (Basel), 2016, 9(6): 419 https://doi.org/10.3390/ma9060419
18
Tamimi A, Hassan N M, Fattah K, Talachi A. Performance of cementitious materials produced by incorporating surface treated multiwall carbon nanotubes and silica fume. Construction & Building Materials, 2016, 114: 934–945 https://doi.org/10.1016/j.conbuildmat.2016.03.216
19
Eftekhari M, Mohammadi S. Multiscale dynamic fracture behavior of the carbon nanotube reinforced concrete under impact loading. International Journal of Impact Engineering, 2016, 87: 55–64 https://doi.org/10.1016/j.ijimpeng.2015.06.023
20
Nochaiya T, Chaipanich A. Behavior of multi-walled carbon nanotubes on the porosity and microstructure of cement-based materials. Applied Surface Science, 2011, 257(6): 1941–1945 https://doi.org/10.1016/j.apsusc.2010.09.030
21
Konsta-Gdoutos M S, Metaxa Z S, Shah S P. Multi-scale mechanical and fracture characteristics and early-age strain capacity of high performance carbon nanotube/cement nanocomposites. Cement and Concrete Composites, 2010, 32(2): 110–115 https://doi.org/10.1016/j.cemconcomp.2009.10.007
22
Metaxa Z S, Konsta-Gdoutos M S, Shah S P. Carbon nanotubes reinforced concrete. In: Konstantin S, Taha M E, eds. Nanotechnology of Concerete: the Next Big Thing is Small. ACI Special Publication, 2009, 267: 11–20
Vodák F, Trtík K, Kapičková O, Hošková Š, Demo P. The effect of temperature on strength–porosity relationship for concrete. Construction & Building Materials, 2004, 18(7): 529–534 https://doi.org/10.1016/j.conbuildmat.2004.04.009
25
Auskern A, Horn W. Capillary porosity in hardened cement paste. Journal of Testing and Evaluation, 1973, 1(1): 74–79 https://doi.org/10.1520/JTE11604J
26
Pantazopoulou S, Mills R. Microstructural aspects of the mechanical response of plain concrete. ACI Materials Journal, 1995, 92(6): 605–616
27
ASTM-D4404. Standard Test Method for Determination of Pore Volume and Pore Volume Distribution of Soil and Rock by Mercury Intrusion Porosimetry. ASTM International, West Conshohocken, PA, 2007, 1–7
28
Winslow D N, Cohen M D, Bentz D P, Snyder K A, Garboczi E J. Percolation and pore structure in mortars and concrete. Cement and Concrete Research, 1994, 24(1): 25–37 https://doi.org/10.1016/0008-8846(94)90079-5
29
Cook D J, Cao H T. An Investigation of the Pore Structure in Fly Ash/OPC Blends, Pore Structure and Construction Properties. Proceedings of the First International Congress, RILEM/AFREM, 1987, 1: 69–76
30
Ouellet S, Bussière B, Aubertin M, Benzaazoua M. Microstructural evolution of cemented paste backfill: mercury intrusion porosimetry test results. Cement and Concrete Research, 2007, 37(12): 1654–1665 https://doi.org/10.1016/j.cemconres.2007.08.016
31
Li G Y, Wang P M, Zhao X. Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes. Carbon, 2005, 43(6): 1239–1245 https://doi.org/10.1016/j.carbon.2004.12.017
32
Holly J, Hampton D, Thomas M D. Modelling relationships between permeability and cement paste pore microstructures. Cement and Concrete Research, 1993, 23(6): 1317–1330 https://doi.org/10.1016/0008-8846(93)90069-L
33
El-Dieb A, Hooton R. Evaluation of the Katz-Thompson model for estimating the water permeability of cement-based materials from mercury intrusion porosimetry data. Cement and Concrete Research, 1994, 24(3): 443–455 https://doi.org/10.1016/0008-8846(94)90131-7
34
Mehta P K, Manmohan D. Pore Size Distribution and Permeability of Hardened Cement Pastes. The 7th International Congress on the Chemistry of Cement, 1980, II: 1–5
35
Moon H Y, Kim H S, Choi D S. Relationship between average pore diameter and chloride diffusivity in various concretes. Construction & Building Materials, 2006, 20(9): 725–732 https://doi.org/10.1016/j.conbuildmat.2005.02.005
36
Moro F, Böhni H. Ink-bottle effect in mercury intrusion porosimetry of cement-based materials. Journal of Colloid and Interface Science, 2002, 246(1): 135–149 https://doi.org/10.1006/jcis.2001.7962
37
Diamond S. Mercury porosimetry: an inappropriate method for the measurement of pore size distributions in cement-based materials. Cement and Concrete Research, 2000, 30(10): 1517–1525 https://doi.org/10.1016/S0008-8846(00)00370-7
38
Gallé C. Effect of drying on cement-based materials pore structure as identified by mercury intrusion porosimetry: a comparative study between oven-, vacuum-, and freeze-drying. Cement and Concrete Research, 2001, 31(10): 1467–1477 https://doi.org/10.1016/S0008-8846(01)00594-4
39
Mehta P K, Monteiro P J. Concrete: Microstructure, Properties, and Materials (3rd ed). 2006. McGraw-Hill New York
Chen X, Wu S. Influence of water-to-cement ratio and curing period on pore structure of cement mortar. Construction & Building Materials, 2013, 38: 804–812 https://doi.org/10.1016/j.conbuildmat.2012.09.058
Zeng Q, Li K, Fen-chong T, Dangla P. Pore structure characterization of cement pastes blended with high-volume fly-ash. Cement and Concrete Research, 2012, 42(1): 194–204 https://doi.org/10.1016/j.cemconres.2011.09.012
45
Zhou J, Ye G, van Breugel K. Characterization of pore structure in cement-based materials using pressurization–depressurization cycling mercury intrusion porosimetry (PDC-MIP). Cement and Concrete Research, 2010, 40(7): 1120–1128 https://doi.org/10.1016/j.cemconres.2010.02.011
46
Felipe C, Cordero S, Kornhauser I, Zgrablich G, López R, Rojas F. Domain complexion diagrams related to mercury intrusion-extrusion in monte carlo-simulated porous networks. Particle & Particle Systems Characterization, 2006, 23(1): 48–60 https://doi.org/10.1002/ppsc.200601013
47
Porcheron F, Monson P A, Thommes M. Modeling mercury porosimetry using statistical mechanics. Langmuir, 2004, 20(15): 6482–6489 https://doi.org/10.1021/la049939e
48
Porcheron F, Thommes M, Ahmad R, Monson P A. Mercury porosimetry in mesoporous glasses: a comparison of experiments with results from a molecular model. Langmuir, 2007, 23(6): 3372–3380 https://doi.org/10.1021/la063080e
49
Moura M J, Ferreira P J, Figueiredo M M. Mercury intrusion porosimetry in pulp and paper technology. Powder Technology, 2005, 160(2): 61–66 https://doi.org/10.1016/j.powtec.2005.08.033
50
Bhuiyan I, Mouzon J, Forsmo S P E, Hedlund J. Quantitative image analysis of bubble cavities in iron ore green pellets. Powder Technology, 2011, 214(3): 306–312 https://doi.org/10.1016/j.powtec.2011.08.028
51
Wild S. A discussion of the paper “Mercury porosimetry—an inappropriate method for the measurement of pore size distributions in cement-based materials” by S. Diamond. Cement and Concrete Research, 2001, 31(11): 1653–1654 https://doi.org/10.1016/S0008-8846(01)00616-0
52
Gallé C. Reply to the discussion by S. Diamond of the paper “Effect of drying on cement-based materials pore structure as identified by mercury intrusion porosimetry: a comparative study between oven-, vacuum-and freeze-drying”. Cement and Concrete Research, 2003, 33(1): 171–172 https://doi.org/10.1016/S0008-8846(02)00941-9
53
Wang Y.Microstructural study of hardened cement paste by backscatter scanning electron microscopy and image analysis. Dissertation for PhD. degree. Purdue University, 1995
54
Liu Z, Winslow D. Sub-distributions of pore size: a new approach to correlate pore structure with permeability. Cement and Concrete Research, 1995, 25(4): 769–778 https://doi.org/10.1016/0008-8846(95)00067-M
55
Diamond S. A critical comparison of mercury porosimetry and capillary condensation pore size distributions of portland cement pastes. Cement and Concrete Research, 1971, 1(5): 531–545 https://doi.org/10.1016/0008-8846(71)90058-5
56
Katz A, Thompson A. Quantitative prediction of permeability in porous rock. Physical Review B: Condensed Matter and Materials Physics, 1986, 34(11): 8179–8181 https://doi.org/10.1103/PhysRevB.34.8179
57
Chatterji S. A discussion of the paper “Mercury porosimetry—an inappropriate method for the measurement of pore size distributions in cement-based materials” by S. Diamond. Cement and Concrete Research, 2001, 31(11): 1657–1658 https://doi.org/10.1016/S0008-8846(01)00618-4
58
Diamond S. Reply to the discussion by S. Chatterji of the paper “Mercury porosimetry—an inappropriate method for the measurement of pore size distributions in cement-based materials”. Cement and Concrete Research, 2001, 31(11): 1659 https://doi.org/10.1016/S0008-8846(01)00619-6
59
Wenzel R N. Resistance of solid surfaces to wetting by water. Industrial & Engineering Chemistry, 1936, 28(8): 988–994 https://doi.org/10.1021/ie50320a024
60
Marmur A. Soft contact: measurement and interpretation of contact angles. Soft Matter, 2006, 2(1): 12–17 https://doi.org/10.1039/B514811C
Moutinho I, Figueiredo M, Ferreira P. Evaluating the surface energy of laboratory-made paper sheets by contact angle measurements. Tappi Journal, 2007, 6(6): 26–32
63
Rosales-Leal J, Rodríguez-Valverde M A, Mazzaglia G, Ramón-Torregrosa P J, Díaz-Rodríguez L, García-Martínez O, Vallecillo-Capilla M, Ruiz C, Cabrerizo-Vílchez M A. Effect of roughness, wettability and morphology of engineered titanium surfaces on osteoblast-like cell adhesion. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010, 365(1−3): 222–229 https://doi.org/10.1016/j.colsurfa.2009.12.017
Walls J, Smith R. Surface science techniques. Vacuum, 2013, 45(6−7): 647
67
Hearn N, Hooton R D. Sample mass and dimension effects on mercury intrusion porosimetry results. Cement and Concrete Research, 1992, 22(5): 970–980 https://doi.org/10.1016/0008-8846(92)90121-B
68
Poon C S, Lam L, Wong Y L. A study on high strength concrete prepared with large volumes of low calcium fly ash. Cement and Concrete Research, 2000, 30(3): 447–455 https://doi.org/10.1016/S0008-8846(99)00271-9
69
Feldman R F, Beaudoin J J. Pretreatment of hardened hydrated cement pastes for mercury intrusion measurements. Cement and Concrete Research, 1991, 21(2−3): 297–308 https://doi.org/10.1016/0008-8846(91)90011-6
70
Korpa A, Trettin R. The influence of different drying methods on cement paste microstructures as reflected by gas adsorption: comparison between freeze-drying (F-drying), D-drying, P-drying and oven-drying methods. Cement and Concrete Research, 2006, 36(4): 634–649 https://doi.org/10.1016/j.cemconres.2005.11.021
71
Konecny L, Naqvi S J. The effect of different drying techniques on the pore size distribution of blended cement mortars. Cement and Concrete Research, 1993, 23(5): 1223–1228 https://doi.org/10.1016/0008-8846(93)90183-A
Ma H. Mercury intrusion porosimetry in concrete technology: tips in measurement, pore structure parameter acquisition and application. Journal of Porous Materials, 2014, 21(2): 207–215 https://doi.org/10.1007/s10934-013-9765-4
75
ISO15901-1. Evaluation of Pore Size Distribution and Porosimetry of Solid Materials by Mercury Porosimetry and Gas Adsorption—Part 1: Mercury Porosimetry (International Organization for Standardization. 2005. Geneva: 6–9
76
Kaufmann J, Loser R, Leemann A. Analysis of cement-bonded materials by multi-cycle mercury intrusion and nitrogen sorption. Journal of Colloid and Interface Science, 2009, 336(2): 730–737 https://doi.org/10.1016/j.jcis.2009.05.029
77
Kumar R, Bhattacharjee B. Study on some factors affecting the results in the use of MIP method in concrete research. Cement and Concrete Research, 2003, 33(3): 417–424 https://doi.org/10.1016/S0008-8846(02)00974-2
78
Ye G, Van Breugel K, Fraaij A. Three-dimensional microstructure analysis of numerically simulated cementitious materials. Cement and Concrete Research, 2003, 33(2): 215–222 https://doi.org/10.1016/S0008-8846(02)00889-X
79
Winslow D. Some experimental possibilities with mercury intrusion porosimetry. MRS Proceedings. Cambridge Univ Press, 1988
80
Bonard J M, Croci M, Klinke C, Kurt R, Noury O, Weiss N. Carbon nanotube films as electron field emitters. Carbon, 2002, 40(10): 1715–1728 https://doi.org/10.1016/S0008-6223(02)00011-8
81
Lau A K T, Hui D. The revolutionary creation of new advanced materials—carbon nanotube composites. Composites Part B: Engineering, 2002, 33(4): 263–277 https://doi.org/10.1016/S1359-8368(02)00012-4
82
Fragneaud B, Masenelli-Varlot K, Gonzalez-Montiel A, Terrones M, Cavaillé J Y. Mechanical behavior of polystyrene grafted carbon nanotubes/polystyrene nanocomposites. Composites Science and Technology, 2008, 68(15−16): 3265–3271 https://doi.org/10.1016/j.compscitech.2008.08.013
83
Li G Y, Wang P M, Zhao X. Pressure-sensitive properties and microstructure of carbon nanotube reinforced cement composites. Cement and Concrete Composites, 2007, 29(5): 377–382 https://doi.org/10.1016/j.cemconcomp.2006.12.011
84
Makar J, Margeson J, Luh J. Carbon nanotube/cement composites-early results and potential applications. Conference on Construction Materials, 2005
85
Moore E M, Ortiz D L, Marla V T, Shambaugh R L, Grady B P. Enhancing the strength of polypropylene fibers with carbon nanotubes. Journal of Applied Polymer Science, 2004, 93(6): 2926–2933 https://doi.org/10.1002/app.20703
86
Zhao Q, Gan Z, Zhuang Q. Electrochemical sensors based on carbon nanotubes. Electroanalysis, 2002, 14(23): 1609–1613 https://doi.org/10.1002/elan.200290000
87
Riggs J E, Guo Z, Carroll D L, Sun Y P. Strong luminescence of solubilized carbon nanotubes. Journal of the American Chemical Society, 2000, 122(24): 5879–5880 https://doi.org/10.1021/ja9942282
88
Makar J, Beaudoin J. Carbon nanotubes and their application in the construction industry. Special Publication- Royal Society of Chemistry, 2004, 292: 331–341 https://doi.org/10.1039/9781847551528-00331
89
Yu M F, Lourie O, Dyer M J, Moloni K, Kelly T F, Ruoff R S. Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load. Science, 2000, 287(5453): 637–640 https://doi.org/10.1126/science.287.5453.637
90
Salvetat J P, Bonard J M, Thomson N H, Kulik A J, Forró L, Benoit W, Zuppiroli L. Mechanical properties of carbon nanotubes. Applied Physics A: Materials Science & Processing, 1999, 69(3): 255–260 https://doi.org/10.1007/s003390050999
91
Walters D, Ericson L M, Casavant M J, Liu J, Colbert D T, Smith K A, Smalley R E. Elastic strain of freely suspended single-wall carbon nanotube ropes. Applied Physics Letters, 1999, 74(25): 3803–3805 https://doi.org/10.1063/1.124185
92
Berber S, Kwon Y K, Tomanek D. Unusually high thermal conductivity of carbon nanotubes. Physical Review Letters, 2000, 84(20): 4613–4616 https://doi.org/10.1103/PhysRevLett.84.4613
93
Louie S G. Electronic properties, junctions, and defects of carbon nanotubes. In: Dresselhaus M S, Dresselhaus G, Avouris P, eds. Carbon Nanotubes. Springer, 2001, 113–145
94
Cwirzen A, Habermehl-Cwirzen K, Penttala V. Surface decoration of carbon nanotubes and mechanical properties of cement/carbon nanotube composites. Advances in Cement Research, 2008, 20(2): 65–73 https://doi.org/10.1680/adcr.2008.20.2.65
95
Makar J M, Chan G W. Growth of cement hydration products on single-walled carbon nanotubes. Journal of the American Ceramic Society, 2009, 92(6): 1303–1310 https://doi.org/10.1111/j.1551-2916.2009.03055.x
96
Barraza H J, Pompeo F, O’Rea E A, Resasco D E. SWNT-filled thermoplastic and elastomeric composites prepared by miniemulsion polymerization. Nano Letters, 2002, 2(8): 797–802 https://doi.org/10.1021/nl0256208
97
Saez de Ibarra Y, Gaitero J J, Erkizia E, Campillo I. Atomic force microscopy and nanoindentation of cement pastes with nanotube dispersions. Physica Status Solidi (a), 2006, 203(6): 1076–1081
98
Ma R Z, Wu J, Wei B Q, Liang J, Wu D H. Processing and properties of carbon nanotubes–nano-SiC ceramic. Journal of Materials Science, 1998, 33(21): 5243–5246 https://doi.org/10.1023/A:1004492106337
99
Wansom S, Kidner N J, Woo L Y, Mason T O. AC-impedance response of multi-walled carbon nanotube/cement composites. Cement and Concrete Composites, 2006, 28(6): 509–519 https://doi.org/10.1016/j.cemconcomp.2006.01.014
Eitan A, Jiang K, Dukes D, Andrews R, Schadler L S. Surface modification of multiwalled carbon nanotubes: toward the tailoring of the interface in polymer composites. Chemistry of Materials, 2003, 15(16): 3198–3201 https://doi.org/10.1021/cm020975d
102
Cwirzen A, Habermehl-Cwirzen K, Nasibulin A G, Kaupinen E I, Mudimela P R, Penttala V. SEM/AFM studies of cementitious binder modified by MWCNT and nano-sized Fe needles. Materials Characterization, 2009, 60(7): 735–740 https://doi.org/10.1016/j.matchar.2008.11.001
103
Musso S, Tulliani J M, Ferro G, Tagliaferro A. Influence of carbon nanotubes structure on the mechanical behavior of cement composites. Composites Science and Technology, 2009, 69(11−12): 1985–1990 https://doi.org/10.1016/j.compscitech.2009.05.002
104
Konsta-Gdoutos M S, Metaxa Z S, Shah S P. Multi-scale mechanical and fracture characteristics and early-age strain capacity of high performance carbon nanotube/cement nanocomposites. Cement and Concrete Composites, 2010, 32(2): 110–115 https://doi.org/10.1016/j.cemconcomp.2009.10.007
105
Sanchez F, Ince C. Microstructure and macroscopic properties of hybrid carbon nanofiber/silica fume cement composites. Composites Science and Technology, 2009, 69(7−8): 1310–1318 https://doi.org/10.1016/j.compscitech.2009.03.006
106
Musso S, Porro S, Vinante M, Vanzetti L, Ploeger R, Giorcelli M, Possetti B, Trotta F, Pederzolli C, Tagliaferro A. Modification of MWNTs obtained by thermal-CVD. Diamond and Related Materials, 2007, 16(4): 1183–1187 https://doi.org/10.1016/j.diamond.2006.11.087
107
Chaipanich A, Nochaiya T, Wongkeo W, Torkittikul P. Compressive strength and microstructure of carbon nanotubes–fly ash cement composites. Materials Science and Engineering A, 2010, 527(4): 1063–1067 https://doi.org/10.1016/j.msea.2009.09.039
108
Nochaiya T, Tolkidtikul P, Singjai P, Chaipanich A. Microstructure and characterizations of Portland-carbon nanotubes pastes. Advanced Materials Research, 2008, 55: 549–552 https://doi.org/10.4028/www.scientific.net/AMR.55-57.549
109
Pandey S, Sharma R. The influence of mineral additives on the strength and porosity of OPC mortar. Cement and Concrete Research, 2000, 30(1): 19–23 https://doi.org/10.1016/S0008-8846(99)00180-5
110
Abell A, Willis K, Lange D. Mercury intrusion porosimetry and image analysis of cement-based materials. Journal of Colloid and Interface Science, 1999, 211(1): 39–44 https://doi.org/10.1006/jcis.1998.5986
111
Pipilikaki P, Beazi-Katsioti M. The assessment of porosity and pore size distribution of limestone Portland cement pastes. Construction & Building Materials, 2009, 23(5): 1966–1970 https://doi.org/10.1016/j.conbuildmat.2008.08.028
112
Atahan H N, Oktar O N, Taşdemir M A. Effects of water–cement ratio and curing time on the critical pore width of hardened cement paste. Construction & Building Materials, 2009, 23(3): 1196– 1200 https://doi.org/10.1016/j.conbuildmat.2008.08.011
113
Lu Z, Hou D, Meng L, Sun G, Lu C, Li Z. Mechanism of cement paste reinforced by graphene oxide/carbon nanotubes composites with enhanced mechanical properties. RSC Advances, 2015, 5(122): 100598–100605 https://doi.org/10.1039/C5RA18602A