Physical and chemical effects of siliceous particles at nano, micro, and macro scales on properties of self-consolidating mortar overlays Parviz Ghoddousi, Ali Akbar Shirzadi Javid ⇑ , Maziar Zareechian, Asghar Habibnejad korayem School of Civil Engineering, Iran University of Science and Technology, P.O. Box 16765-163, Narmak, Tehran, Iran highlights  Effects of siliceous particles at nano, micro, and macro scales in self-consolidating mortars were assessed.  Mechanical and durability properties, surface characteristics and early age shrinkage were investigated.  Interfacial transition zone and the microstructures were studied by using SEM, TGA and AFM.  Based on TGA results, pozzolanic reaction of samples containing silica fume and nanosilica are almost the same.  Higher silica percentage in sand reduces improvement of abrasion resistance due to using SCMs.  According to AFM image, surface skid resistance was improved by using SCMs and sands with lower SiO 2 percent. article info Article history: Received 13 May 2018 Received in revised form 13 August 2018 Accepted 13 September 2018 Keywords: Self-consolidating mortar Siliceous particles Skid resistance Abrasion resistance Plastic shrinkage Water absorption abstract The aim of this experimental investigation is to study the effect of siliceous particle at nano (0, 1, and 2% of pyrogenic nanosilica), micro (silica fume with 0, 5, and 10% cement weight replacement), and macro scales (sand with SiO 2 percentages of 0, 50 and 100%) on mechanical properties, durability, and surface characteristics of self-consolidating mortars as an overlay. For this purpose, 27 self-consolidating mortar overlays (SCMOs) with a water to cement ratio of 0.4 and different mixture proportions were prepared. Mini-slump flow and V-funnel time values were determined experimentally in fresh SCMOs. Moreover, the compressive and flexural strength of mechanical strength, water absorption, porosity, abrasion resis- tance (as a durability property), skid resistance (as a surface characteristic), and early age shrinkage were measured. The interfacial transition zone and the microstructures were studied using scanning electron microscope (SEM), thermogravimetric analysis (TGA), and atomic force microscope (AFM). Based on the results, the synergic effect of silica based particles in nanoscale and microscale improved mechanical, durability, and frictional properties. SEM images showed that samples containing limestone sand had denser interfacial transition zone (ITZ) than siliceous sand samples due to better interlocking. Using the AFM images, high-silica sand mortar samples exhibit lower skid resistance compared to limestone type sand. Besides, incorporating siliceous sand improves the abrasion resistance (as a durability factor of the slip resistance) about 45.8% compared to lime-based samples. In addition, improvement in wear resistance caused by mineral additions is reduced by increasing the SiO 2 percentage in the sand. The rela- tion among porosity, compressive strength, and abrasion resistance was stronger in limestone type mixtures. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, concrete pavement is frequently used for many rea- sons including their high rigidity (ability to distribute the load on the foundation), a desirable behavior against fatigue, eco- friendliness (fully recyclable, not releasing chemicals in the air, not using oil, etc.), and, above which, cost-effectiveness [1]. Surface distresses have been shown as common defects that critically affect the quality of these pavements. Hydraulic cement overlays are used as a rehabilitation technique for deteriorated slabs [2,3]. The compressive and flexural strengths (as mechanical proper- ties), skid resistance (as a surface property), wear and abrasion resistance, and porosity and water absorption (as durability prop- erties) are the most important features of the cement-based pave- ments [4]. Skid resistance of concrete surface is an essential https://doi.org/10.1016/j.conbuildmat.2018.09.068 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: shirzad@iust.ac.ir (A.A. Shirzadi Javid). Construction and Building Materials 189 (2018) 1140–1154 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat