Concrete mix design containing calcareous tuffs as a partial sand substitution Messaouda Cherrak ⇑ , Abderrahim Bali, Kamel Silhadi Laboratoire Construction et Environnement, Ecole Nationale Polytechnique (ENP), 10 Avenue Hassan BADI, El Harrach, Alger, Algeria highlights  This research investigates the effects of calcareous tuff on concrete properties.  Two tuffs, distinct by their fines contents of 27% and 34% respectively, are studied.  Sand is partially replaced by tuffs at the following proportions (5%, 15%, 25%, 35%).  The compressive strength increase from 13% to 33% for 25% of tuff with superplasticizer.  The durability of tuff concrete is reduced and therefore needs a protection against external aggressions. article info Article history: Received 24 December 2012 Received in revised form 8 April 2013 Accepted 4 May 2013 Available online 5 June 2013 Keywords: Calcareous tuffs Sand Ordinary concrete Mechanical performances Acid environments abstract This paper reports results of the use of calcareous tuff in ordinary concrete as a partial sand substitution. The compressive and tensile strengths, water absorption (total and capillary) and resistance to acid envi- ronments of concretes produced with two tuffs using varying percentages (5–35%) are studied. The incor- poration of calcareous tuff in concrete requires the use of a superplasticizer to overcome the workability loss resulting from the high fines content in tuffs. High concrete performances have been developed with the use of an optimum of 25% of tuff addition. The increase in compressive strength reaches 33%. How- ever, absorption and chemical resistance were reduced probably due to the absorbing character and cal- careous nature of tuffs. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The increase in demand for sand in Algeria during this last dec- ade, resulting from the significant development construction industry (large housing programmes and infrastructures) induced a huge material deficit. To overcome this problem, it is important to use materials of substitution such as crushed sand [1], dune sand [2–4], limestone fines, natural pozzolana, blast furnaces slag and different wastes [5–7]. However, even with these palliative materials, the expectations of the market are still far from being satisfied and the search for other alternatives remains necessary. The work presented in this paper aims to valorise tuffs as a new material of replacement of sand in concrete because of its abun- dance in Algeria which covers a large area of about 300,000 km 2 [8–10]. A literature review revealed that there is a few or no research undertaken on the use of tuffs in structural concrete. However, only works on the stabilised cement calcareous tuffs used in road construction in some countries such as Argentina and Tunisia have been reported in the literature [11–13]. It should be noted that both calcareous tuffs and crushed sand are nearly similar because of the similarity of their mineralogical nature and high fines content. Thus it is very relevant to use tuffs as a material of substitution. For the purpose of our investigation, tuffs of the different exist- ing quarries of the North of Algeria have been analysed in order to determine their main characteristics. Consequently and in order to study tuff addition effects on a fresh and hardened ordinary concrete respectively, several mixes containing tuffs have been considered. 2. Materials and methods 2.1. Materials used A list of more than 80 calcareous tuff exploited deposits has been provided by the National Public Works Laboratory (LCTP) [14]. The examination of the data emphasises that tuffs differ mainly by their fines content and their geotechnical 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.05.051 ⇑ Corresponding author. Tel.: +213 555 62 87 90; fax: +213 21 54 05 88. E-mail address: messaoudacherrak@yahoo.fr (M. Cherrak). Construction and Building Materials 47 (2013) 318–323 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat