Influence of temperature in the evolution of compressive strength and in its correlations with UPV in eco-concretes with recycled materials

This research studies the influence of temperature on the evolution of compressive strength and on its correlations with the ultrasonic pulse velocity in concretes and eco-concretes, with a focus on the ages between 1 and 28 days. To that end, 9 concrete mixtures are studied, with parametric variations in the following components: (i) the type of aggregate, including several replacement ratios of recycled aggregate; (ii) water/cement ratio; (iii) cement content, as well as its partial replacement with biomass ashes. These 9 mixtures can be further divided in two major groups: 6 vibrated concretes and 3 self-compacting concretes. The 6 mixtures of vibrated concretes are: a mixture of reference, three mixtures with partial replacement of fine and coarse recycled concrete aggregates (8%, 20% and 31% replacement), and two mixtures with partial replacement of cement with biomass ashes from the paper industry (15% and 30% replacement). The 3 remaining mixtures corresponding to self-compacting concretes are: one reference mixture of self-compacting concrete and two additional mixtures with partial replacement of fine and coarse recycled concrete aggregates from precast elements (20% and 50% replacement). The influence of temperature on the evolution of strength in each of the mixtures is determined for curing temperatures of 5 C, 20 C and 45 C. The study further includes the evaluation of the influence that temperature and mixture parameters (particularly those of eco-concretes) have on the relationship between compressive strength and ultrasonic pulse velocity.This study was developed with the support of the projects of Program FEDER-INNTERCONECTA ITC-20133075 "Use of paper and tire industry wastes other than their use in building lightweight ecological embankments and other construction materials" and ITC-20113055 "Development of value adding technologies for RCDs for innovative applications", convened by the Center for Industrial Technological Development (CDTI, for its initials in Spanish), dependent on the Ministry of Economy and Competitiveness (Spain) and co-funded by the Technological Fund - FEDER Funds.This work is partly financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT - Portuguese Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633