Time-dependent fibre pull-out behaviour in self-compacting concrete

In the present study, the effectiveness of a fibre as an element for transferring stresses across cracks under a sustained load was assessed. Single fibre pull-out creep tests were performed, in which fibre slip was monitored as a function of the time. The influence of the fibre orientation angle (0, 30 and 60 degrees), as well as pre-imposed fibre slip levels, spr, 0.3 and 0.5 mm on the creep response was investigated. Additionally, instantaneous fibre pull-out tests were carried out on undamaged-bond specimens in order to quantify the effects of the pull-out creep behaviour. The damage introduced by the pre-slip levels in the bond of the fibre/matrix interface influenced the long-term fibre pull-out behaviour and, consequently, accelerated the creep rate. However, the assembled pull-out creep behaviour did not differ considerably from the instantaneous pull-out behaviour for the adopted pre-imposed fibre slip levels.This work is supported by the FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project 18 SlabSys-HFRC-PTDC/ECM/120394/2010. The authors would like to acknowledge the materials supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash).info:eu-repo/semantics/publishedVersio

Long term deformations by creep and shrinkage in recycled aggregate concrete

The main aim of this work was to determine creep and shrinkage variations experienced in recycled concrete, made by replacing the main fraction of the natural aggregate with a recycled aggregate coming from waste concrete and comparing it to a control concrete. It was possible to state that the evolution of deformation by shrinkage and creep was similar to a conventional concrete, although the results after a period of 180 days showed the influence of the substitution percentage in the recycled aggregates present in the mixture. In the case when 100% coarse natural aggregate was replaced by recycled aggregate there was an increase in the deformations by creep of 51% and by shrinkage of 70% as compared to those experienced by the control concrete. The substitution percentages of coarse natural aggregate by coarse recycled aggregate were 20, 50 and 100%. Fine natural aggregate was used in all cases and the amount of cement and water–cement ratio remained constant in the mixture.Domingo Cabo, A.; Lazaro, C.; López Gayarre, F.; Serrano, MA.; López Codina, C. (2009). Long term deformations by creep and shrinkage in recycled aggregate concrete. Materials and Structures. 43(8):1147-1160. doi:10.1617/s11527-009-9573-0S11471160438Alaejos Gutierrez P (2006) Utilización de árido reciclado para la fabricación de hormigón estructural. ACHE (Asociación científico-Técnica del Hormigón Estructural)EHE, Annex 19 (2008) Instrucción de Hormigón Estructural. Ministerio de FomentoSánchez de Juan M (2005) Estudio sobre la utilización de árido reciclado para la fabricación de hormigón estructural. PhD Thesis, Polytechnic University of Madrid, SpainGómez-Soberón JMV (2003) Relationship between gas absorption and the shrinkage and creep of recycled aggregate concrete. Cem Concr Aggreg 25(2):42–48Amnon K (2003) Properties of concrete made with recycled aggregate from partially hydrates old concrete. Cem Concr Resour 33:703–711Kishore R, Bairagi NK (2007) Creep and drying shrinkage of recycled aggregate concrete. In: Proceedings of the first international conference on recent advances in concrete technology, pp 289–298Poon CS, Kou SC, Chan D (2006) Influence of steam curing on hardened properties of recycled aggregate concrete. Mag Concr Res 58:289–299Sato R, Maruyama I, Sogabe T et al (2007) Flexural behavior of reinforced recycled concrete beams. J Adv Concr Technol 5:43–61Zaharieva R (2003) Assessment of the surface permeation properties of recycled aggregate concrete. Cem Concr Compos 25:223–232Torben CH (1986) The second RILEM state of the art report on recycled aggregate and recycled aggregates concrete. Mater Struct 1(111):201–246Barra M (1996) Estudio de la durabilidad del hormigón de arido reciclado en su aplicación como hormigón estructural. PhD Thesis, Polytechnic University of Cataluña, SpainEtxeberria M (2006) Recycled aggregate concrete as structural material. Mater Struct 40:529–541ASTM C512-02 (2002) Standard test method for creep of concrete in compression. American Society for Testing and Materials, PhiladelphiaKakizaki M, Harada M, Soshiroda T, Kubota S, Ikeda T, Kasai Y (1988) Strength and elastic modulus of recycled aggregate concrete. In: Proceedings of the second international RILEM symposium on demolition and reuse of concrete and masonry, vol 2. Reuse of Demolition Waste, pp 565–574CEB-FIP (1990) Model code. Comité Euro-International du Béton–Fédération Internationale de la PrécontrainteRILEM Model B3 (1995) Creep and shrinkage model for analysis and design of concrete structuresGardner NJ, Lockman MJ (2001) Design provisions for drying shrinkage and creep of normal strength concrete. ACI Mater J 98(2):159–16

Creep and Shrinkage of SCC

Creep and shrinkage are an important factor related to serviceability conditions for concrete structures. Self-consolidating concrete (SCC) requires modifications in mix design to produce flowable and nonsegregating concrete. These modifications raise concerns on SCC creep and shrinkage predicting models which originally developed based on collected data of conventional concrete and whether these models can predict the creep and shrinkage of SCC accurately. In this chapter, creep and shrinkage of various grades and types of SCC (such as high strength-self consolidating concrete (HS-SCC) and high performance-self consolidating concrete (HP-SCC)) were included and discussed. In addition, comparisons were included between measured data of SCC and common predicting models used by designers. This chapter found that none of these current models are able to include the broad range of SCC mixes that may be produced for specialized SCC applications in today\u27s market