Effects of nano and micro size of CaO and MgO, nano-clay and expanded perlite aggregate on the autogenous shrinkage of mortar Rıza Polat a , Ramazan Demirbog˘a a,b,⇑ , Waleed H. Khushefati b a Engineering Faculty, Department of Civil Engineering, Atatürk University, 25240 Erzurum, Turkey b Engineering Faculty, Civil Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia highlights  Reduction in AS due to nano-MgO was higher than that of MgO.  The maximum reduction in AS were observed for both CaO75 and nano-MgO75.  Nano-CaO was ineffective in the reduction of AS.  Reduction in AS due to 20% EPA equal to that of the nano-MgO25. article info Article history: Received 12 September 2014 Received in revised form 17 January 2015 Accepted 18 February 2015 Available online 4 March 2015 Keywords: Nano-CaO Nano-MgO CaO MgO Nano-clay Expanded perlite aggregate Autogenous shrinkage abstract When the water-to-binder ratio is lower than a critical value, a considerable self-desiccation may occur, leading to autogenous shrinkage (AS). This volume change can induce internal stresses when the shrink- age is restricted, and may cause micro cracks, endangering the durability of the cement based composites. It is essential to find appropriate ways to avoid such a risk of cracking at early ages. Methods based on the concept of internal concrete curing, expansive additives have been suggested in the literature. This paper focuses on the reduction of AS by both methods for the same mix proportions of the mortars to compare their effects. Thus, the effects of different percentages of pre-saturated expanded perlite aggregate (EPA), micro and nano size MgO, CaO and smectite (based) nano clays on AS of the mortars are discussed and compared. The highest reduction was observed for mixes containing 7.5% CaO and nano-MgO and resulting in a reduction of the autogenous shrinkage by 80%, at 28 days. However, reduction obtained by nano-CaO was negligible. EPA replacement of 30% of the fine aggregate reduced AS by 68% at 28 days. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction In recent years there have been an increase in the use of super plasticizer chemical additives in the application of high perfor- mance concrete (HPC) due to its superior properties [1], such as high strength and low permeability, which are achieved through its characteristically dense microstructure [2]. HPC significantly reduce maintenance costs and enhance service life [1,3]. The main problem of HSC, autogenous shrinkage (AS), becomes a dominant factor for crack control [4]. In case the free AS of a concrete structure is prevented, internal tensile stresses exceeding the ten- sile strength of the concrete may develop at early ages. As a result, premature cracks may propagate, making the concrete more vul- nerable to the ingress of potentially aggressive species, such as chlorides, sulfates, freezing water, CO 2 , thus severely reducing the durability and service life of concrete [5,6]. AS is a deformation not caused by external influences such as moisture loss or temperature changes [7]. Rather, AS can be thought of as an ‘‘internal drying’’ or ‘‘self-desiccation’’ caused by the hydration reactions resulting in chemical shrinkage. ‘‘Chemical shrinkage’’ occurs due to the cement reaction of cement with water as the reaction products occupy a smaller volume than the initial constituents [8]. High-performance concrete with low w/b-ratio develops a low permeability. Therefore, it can be expected that conventional external curing techniques may be relatively ineffective for pre- venting self-desiccation at the internal layers of a thick concrete layer. In that case, internal curing needs to be performed, which is a very promising technique that provides additional moisture http://dx.doi.org/10.1016/j.conbuildmat.2015.02.032 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Engineering Faculty, Department of Civil Engineering, Atatürk University, 25240 Erzurum, Turkey. Tel.: +966 535220816, +90 505 884 30 15; fax: +90 442 231 47 63. E-mail addresses: rdemirboga@yahoo.com, ramazan@atauni.edu.tr (R. Demirbog˘a). Construction and Building Materials 81 (2015) 268–275 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat