A SIMPLE AND RATIONAL METHODOLOGY FOR THE FORMULATION OF 1
SELF-COMPACTING CONCRETE MIXES 2
3
G. Rodriguez de Sensale
(1,2)*
; I. Rodriguez Viacava
(2)
; A. Aguado
(3)
4
5
6
Abstract 7
8
The increasing use of Self-Compacting Concrete (SCC) in the construction industry should 9
be assured by the development of mix designs adequates to improve their fresh/hardened 10
state properties and its economy. This paper presents a methodology for the formulation of 11
SCC that achieves some of these developmental goals without reliance on extensive 12
laboratory testing and batch trials. Applications, results in fresh and hardened state, and 13
discussion of the SCC obtained are presented. The proposed method can provide lower costs 14
when compared to a currant SCC mix design method and the literature used for comparison. 15
Keywords: Self-compacting concrete; Mix design; Proportioning. 16
17
(1) Instituto de la Construcción, Facultad de Arquitectura, Universidad de la República, Hugo Prato 2314, 18
11200, Montevideo, Uruguay. 19
(2) Instituto de Ensayo de Materiales, Facultad de Ingenieria, Universidad de la República, Julio Herrera y 20
Reissig 565, 11300, Montevideo, Uruguay. 21
(3) Escola Tècnica Superior d'Enginyers de Camins, Canals i Ports, UPC-BarcelonaTech, C/Jordi Girona 22
Salgado 1-3, Mod. C1, 08034, Barcelona, Spain. 23
24
Corresponding author: Gemma Rodríguez de Sensale 25
Instituto de la Construcción-Instituto de Ensayo de Materiales,Universidad de la República, Montevideo, 26
Uruguay. e-mail adress: gemma@fing.edu.uy 27
INTRODUCTION 28
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Over the last 25 years, self-compacting concrete (SCC) has witnessed a huge development, 30
which is due, mainly, to its intrinsic advantages (De Schutter et al, 2008). This development 31
took place initially, in chemistry incorporated into concrete (Okamura, 1997), and later was 32
extended into the rest of its constitutive materials, using all sort of natural aggregates, mineral 33
residues or recycled aggregates ( Najim and Hall, 2010; Topcu et al, 2010; Wang Choj et al, 34
2006; Cuenca et al, 2013), incorporation of other components (light aggregates, different 35
types of fibers, PCM, etc.) ( Hunger et al, 2009; Jalal et al, 2013; Azeredo and Dinis, 2013), 36
advancing on the influence of the chemical and mineral admixtures. 37
38
Later on, research advanced in diverse fields, such as durability (De Schutter and Audenaert, 39
2007), test methods (U-box, L-box, V-funnel, J-ring, etc.) (BIBM et al, 2005; JSCE 1999; 40
ACI 2007), and it transitioned, most recently, to the modeling of different behaviors in the 41
fresh and hardened states, with multiple statistical treatment methodologies (Pepe et al, 2013; 42
Almeida Filho et al, 2010; Sebaibi et al, 2010). 43
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Also recently, several methods for mix design have been proposed (Agullo et al, 1999; Su et 45
al, 2001; Saak et al, 2001; Xie et al, 2002; Su and Miao, 2003; Aguilar and Barrera, 2003; 46
Patel et al, 2004; Alyamac, 2009; Ferrara et al, 2007; Shen et al, 2009; Sebaibi et al, 2013) 47
without any clear unanimity about which is the most suitable, which is in part a reflex of 48
many conditionals such as different economic and social conditions in different countries, the 49
means available, environmental politics, access to different concrete components, and so on. 50
As a result, rather than making ad-hoc planning for each case, it is more important to enhance 51
a fundamental understanding that enables the design of self-compacting concrete with a 52
scientific methodology, taking into account, not only the components, but also the fabrication 53
means and application resources. 54
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A natural characteristic of SCC, because it has a larger amount of fine aggregates, is that its 56
mechanical properties tend to be higher than those of normal concrete. From this point of 57
view, the literatura on the topic, in referred journals as well as in international conference 58
communications (e.g., the International Congresses on Self Compacting Concrete, which take 59
place in Chicago) situates its mean value of resistance between 50 and 60 MPa (Vilanova 60
2009), which limits some applications in which low or medium resistances are required. In 61
practice, SCC, at least in Spain (Rodriguez Viacava et al. 2012, 2014), is used more often in 62
prefabricated elements than in in situ construction, which is a limiting factor. The 63
construction methods of the two cases are usually different. 64
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From this point of view, much work is emerging in terms of design and application of SCC 66
with low and medium resistances (25–35 MPa) (Sonebi 2004; Roncero et al. 2008; Bermejo 67
et al. 2010; Rodriguez Viacava et al. 2012) taking advantage of different types of local 68
materials and/or wastes, trying to enhance its application field with reasonable costs. 69
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The aim of this paper is to propose a rational procedure for SCC mix proportioning through 71
an optimization process using simple experimental techniques with locally available 72
materials, oriented to concretes with low or medium mechanical properties, which is 73
necessary in order to extend the utilization of SCC. 74
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The method is applied to different case studies; results obtained from concrete in the fresh 76
and hardened state are presented and discussed. In order to analyze the cost of the proposed 77
method, a comparative analysis with the method proposed by American Concrete Institute 78
(ACI) 237R-07 (ACI 2007) is developed (using the same materials). Moreover, laboratory 79
mixtures of SCC, which were obtained with the mix-proportioning method here proposed, 80
were compared with selected data from the literature (again, data using similar materials, and 81
also dealing with similar compressive strength ranges). 82
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PROPOSED METHOD 85
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Fundaments and Phases 87
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In order to achieve self-compactability, the method takes into consideration not only high 89
deformability and resistance to segregation, but also the packing density of the aggregates, in 90
order to obtain the minimum content of voids and a uniform concrete strength. That is, first it 91
deals with the physical part of the dosage (granular skeleton) and subsequently on the 92
chemical part (additives) 93
94
The proposed method assumes that SCC can be obtained by optimizing the composition of 95
the paste and the granular skeleton (as is common practice), each of them individually, as 96
well as by optimizing the paste content in the concrete. The model suggests that the viscosity 97
and flow resistance of the paste govern the fluidity and cohesion of the concrete, and the 98
filling capacity without blocking is ensured by the paste content in the concrete which is in 99
turn associated with the granular skeleton structure. 100
101
A schematic description of the proposed mix design is presented in Figure 1. The Method is 102
developed in three stages. The first stage is related to the concrete optimization of phases, 103
which involves the paste and the granular skeleton; this optimization allows adaptability of 104
the method to the use of local waste and aggregates. The second stage is related to the 105
calculation of the amount of materials needed in order to produce a cubic meter of concrete. 106
The produced concrete mixes allow, on a third stage, the adjustments of parameters (paste 107
volume, air entrainment and water/powder ratio) to ensure the SCC requirements. 108
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Figure 1. Schematic structure of proposed mix design method 110
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The methodology that is here introduced for the design of SCC considers the concrete as a 112
two-phase material consisting of paste and aggregates. The paste-aggregate model, two-113
phases, has also been utilized by other researchers for SCC (Su et al. Saak et al. 2001; Gomes 114
et al. 2002). The design method assume that the paste composition does not intervene in the 115
determination of the optimum proportion between the aggregate mix (de Larrard 1999; 116
Stage 3
Stage 2
Stage 1
