ISSN 1392–3730 print / ISSN 1822–3605 online
JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT
2006, Vol XII, No 3, 215–220
STUDY OF SORPTIVITY OF SELF-COMPACTING CONCRETE WITH MINERAL ADDITIVES Luiz Antonio Pereira de Oliveira1, João Paulo de Castro Gomes2, Cristiana Nadir Gonilho Pereira3 1
University of Beira Interior, Dept of Civil Engineering and Architecture, Calçada Fonte do Lameiro, 6201-001 Covilhã, Portugal. E-mail: email@example.com 2 University of Beira Interior, Dept of Civil Engineering and Architecture, Calçada Fonte do Lameiro, 6201-001 Covilhã, Portugal. E-mail: firstname.lastname@example.org 3 University of Beira Interior, Dept of Civil Engineering and Architecture, Calçada Fonte do Lameiro, 6201-001 Covilhã, Portugal. E-mail: email@example.com Received 02 Nov 2005; accepted 06 Jan 2006 Abstract. This work presents the results of a comparative study of the sorptivity, accomplished in mixtures of selfcompacting concrete with different types of additives and a normal concrete compacted by vibration. The self-compacting concrete mixtures present slump-flow of 650 ± 50 mm and have the same cement contents. In the self-compacting mixtures, were used as additives, fly ash, silica fume, hydraulic lime and a mixture of fly ash and hydraulic lime. A modified carboxylates superplasticiser was used to obtain a specific workability. The capillary absorption was carried out at 7, 14 and 28 days of age, through a methodology described in the work. The results permit to conclude that the used additives propitiate the self-compacting concrete. In terms of capillary absorption, the mixtures with fly ash have a better performance. Keywords: capillarity, fly ash, hydraulic lime, water absorption, self-compacting concrete, silica fume, sorptivity.
1. Introduction In recent years, there is a growing interest in the use of self-compacting concrete (SCC), which provides an overall structure durability [1, 2]. The self-compacting concrete is characterised by its capacity to flow and to fill out the most restricted places of the formwork, without losing homogeneity. On the other hand, a self-compacting concrete should have the capacity of self-densification, resulting in a material whose properties in the hardened state are at least the same achieved with concrete compacted by vibration. One of the employed techniques to produce a selfcompacting concrete is to use fine materials in the concrete, beside the cement. Those fine materials are denominated additions and they can have, or not, a chemical activity. The uses of mineral additions or powders have a purpose, beside substituting a part of the cement, it propitiate the appropriate viscosity so that the self-compaction is reached. It is expected that the addition of high fineness materials can contribute to the improvement of the properties that concern the mechanical resistance, as well as the durability. The fineness of a mineral admixture is very important for the modification of aggregate-cement interface zone, which is the weakest link in concrete [3, 4]. When the use of mineral admixtures is combined with superplasticisers, the pore structure is greatly affected and a significant reduction in the volume of pores is obtained
[5, 6]. In relation to durability, the concretes are appraised through several properties, among them the capillary sorptivity, whose importance is allied to the factor that this is the first phenomenon of transport of aggressive agents that takes place in concrete. Sorptivity, which is an index of moisture transport into unsaturated specimens, has been recognised as an important index of concrete durability, because the test method used for its determination reflects the way that most concretes will be penetrated by water and other injurious agents and it is an especially good measure of the quality of near surface concrete, which governs durability related to reinforcement corrosion . Martys and Ferraris ...