Review Effect of carbon nanotubes on properties of cement mortars Rafat Siddique, Ankur Mehta ⇑ Civil Engineering Department, Thapar University, Patiala 147004, India highlights  Classification of carbon nanotubes.  Uses and applications of carbon nanotubes.  Review of synthesis of carbon nanotubes in previous researches.  Review of various properties like, compressive strength, flexural strength.  Review of properties like microstructure, Youngs modulus, porosity. article info Article history: Received 22 July 2013 Received in revised form 17 September 2013 Accepted 19 September 2013 Available online 12 October 2013 Keywords: Carbon NanoTubes (CNTs) Synthesis of CNTs Applications of CNTs Compressive strength Flexural strength Porosity Young‘s modulus abstract Carbon NanoTubes (CNTs) are primarily elemental carbon consisting of curved graphene layer which con- sists of a single layer of carbon atoms in a honeycomb structure that may contain varying amounts of metal impurities, depending on the method of manufacture. After various years from its detailed charac- terization CNTs have grown from a material of dreams to a real world material that has already found its application fields. The production capability for carbon nanotubes is growing every year in an exponen- tial degree and as a consequence the price is steeply descending. In addition to their remarkable strength, which is usually quoted as 100 times that of tensile strength of steel at one-sixth of the weight, CNTs have shown a surprising array of other properties. It has a wide range of its use in various applications like its use in energy sector, medicine sector, environmental sectors, electronics sectors, etc. In Civil Engineering applications CNTs are being effectively used in various research works which remarkably improves the mechanical properties of cement mortars, when added into it. Published literature has shown that CNTs could be used in manufacturing concrete and mortars. This paper presents an overview of some of the research published on the use of CNT in concrete/mortars. Effect of CNTs on properties such as compressive strength, tensile strength, modulus of elasticity, flexural strength, porosity, electrical conductivity and autogeneous shrinkage are presented in this paper. Ó 2013 Elsevier Ltd. All rights reserved. Contents 1. Introduction ......................................................................................................... 117 2. Properties of carbon nanotubes .......................................................................................... 118 2.1. Electrical properties ............................................................................................. 118 2.2. Mechanical properties ............................................................................................ 118 2.3. Thermal properties .............................................................................................. 118 2.4. Strength ....................................................................................................... 118 2.5. Kinetic properties ............................................................................................... 118 2.6. Toxicity ....................................................................................................... 118 3. Applications of carbon nanotubes ........................................................................................ 119 4. Synthesis of Carbon NanoTubes (CNTs) ................................................................................... 119 5. Properties of cement mortars containing CNTs ............................................................................. 120 5.1. Microstructure .................................................................................................. 121 5.2. Compressive strength ............................................................................................ 122 5.3. Flexural strength ................................................................................................ 125 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.09.019 ⇑ Corresponding author. Tel.: +91 9646493986; fax: +91 175 2393005. E-mail address: ankurmehta07@gmail.com (A. Mehta). Construction and Building Materials 50 (2014) 116–129 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat