Magnesium Phosphate Cements formulated with a low-grade MgO by-product: Physico-mechanical and durability aspects J. Formosa a,⇑ , A.M. Lacasta b , A. Navarro c , R. del Valle-Zermeño a , M. Niubó a , J.R. Rosell c , J.M. Chimenos a a Departament de Ciència dels Materials i Enginyeria Metallúrgica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain b Departament de Física Aplicada, Universitat Politècnica de Catalunya, Av. Dr. Marañón 44-50, 08028 Barcelona, Spain c Departament de Construccions Arquitectòniques II, Universitat Politècnica de Catalunya, Av. Dr. Marañón 44-50, 08028 Barcelona, Spain highlights  MPC formulated with LG-MgO by-product were selected from preliminary study.  Evaluation as repairing mortar: adhesion and MOE tests.  Durability studies evaluating the porosity and sorptivity prior and post-aging.  MPCs formulated with LG-MgO by-product show good durability and repairing properties. article info Article history: Received 20 August 2014 Received in revised form 1 April 2015 Accepted 1 May 2015 Available online 16 May 2015 Keywords: Repair mortar Durability CBPC Magnesium oxide Low-grade magnesium oxide abstract Chemically Bonded Phosphate Ceramics (CBPCs) and, in particular, Magnesium Phosphate Cements (MPCs), show properties very adequate for using as repair mortar for concrete constructions. The obtainment of MPC using MgO-containing by-products as raw materials was proposed by the authors in previous works. There, formulations including boric acid as additive were optimized to obtain good mechanical properties and proper setting times. The current study aims to analyze the viability of the developed formulations to be used as repair mortar. Adhesion to concrete surfaces was evaluated, and in all cases good adhesion strength values were obtained. The durability tests, including freeze/thaw cycles and salts crystallization cycles, have shown an excellent behavior, especially the samples contain- ing the higher amount of boric acid. These promising results indicate that MPC formulated with a low-cost MgO by-product can be an interesting alternative to other repair mortars. In addition to economic benefits in terms of cost of production, the use of by-products has a positive impact on environmental and sustainability aspects. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Repairing materials for construction are a subject of increasing interest. The great number of existing concrete structures suppose a great potential demand of repairing material. Sometimes the reparation must be carried on a few years after the concrete struc- ture has been completed. The possibility of using a good repairing material or system supposes an economic benefit instead of substi- tuting the damage concrete. In this sense, it is of high interest to make improvements by developing new materials, reducing costs, and others aspects that have to be considered in the building and construction sector [1]. Nowadays, the most commonly used repairing materials are polymer mortars and ordinary Portland cement (OPC) mortars [2,3]. In general, the OPC mortars are used owing to their wide range of work and potential fields of application. However, the use of polymer mortars may cover other particular characteristics needed because of their higher adhesion to the substrate, lower shrinkage and permeability [4]. Nevertheless, polymer mortars have problems associated with the thermal behavior due to their glass transition temperature [5]. Moreover, most polymeric mate- rials undergo degradation when exposed to UV radiation and aggressive chemicals [6]. The exposition range of temperature must also be taken into account in resins binders [7]. However, over the last few years, more specific cements have been developed; which could extend the range of work and their application in other fields of technology. Chemically Bonded Phosphate Ceramic (CBPC) is one of those new developed cements, http://dx.doi.org/10.1016/j.conbuildmat.2015.05.071 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +34 934037244; fax: +34 934035438. E-mail address: joanformosa@ub.edu (J. Formosa). Construction and Building Materials 91 (2015) 150–157 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat