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Biocementation is being used to seal cracks in stone and concrete for retrofitting and consolidation works, as alternative to conventional solutions such as using polymeric mortar. As when such traditional techniques are used, joint thickness and roughness play an important role on sealing efficiency and this must be investigated when using biocement. The efficiency of biocementation to seal joints in stone samples considering simultaneously their width and roughness is discussed in this paper. Joints with 0.4, 0.7 and 1 mm width, having smooth and rough surfaces, were artificially created on basalt stone disks. The joints were treated by biocementation until become sealed, i.e., until fluid stop flowing through the joint. Adhesion achieved with the treatment was evaluated by tensile strength measurements in Brazilian splitting tests, in which the samples were split by the sealed joint. The joint surfaces separated after the splitting test were analysed by digital analysis of photographs and stereomicroscope images to check the presence and homogeneity of the precipitated biocement. The tensile strength was larger for the artificial joints with larger width and rough surfaces (maximum values found are 3.94 and 5.67 MPa for the smooth and rough surfaces, respectively). The values found were half the values measured for the intact rock (8 MPa), but still in the order of magnitude of Mega Pascal, therefore indicating strong adhesion between the stone and biocement. Biocementation treatment therefore appears to be adequate for sealing stone joints with different widths within the range investigated and variable roughness.

This paper aims to contribute to a better knowledge of the production and rehydration of thermo activated recycled cement (TRC) and its incorporation in cement based materials. To this end, the influence of different factors in the fresh and hardened properties of mortars with TRC was analysed, such as the water/binder ratio, the treatment temperature, incorporation percentage and particle fineness of TRC. Thermogravimetry, X-ray diffraction, isothermal calorimetry, scanning electron microscopy and 29Si nuclear magnetic resonance spectroscopy were carried out to better understand the hydration behaviour and microstructure development of TRC mortars. Optimal rehydration properties and strength development were obtained for recycled cement thermo activated at 600–800 °C. Binders with CEM I 42.5R and 20, 50 and 100% TRC could be framed in the European normative strength classes 52.5, 42.5 and 32.5, respectively. The main obstacles that hinder the application of TRC are its low setting time and high water demand. However, the water demand and setting time were not significantly affected for up to 50% TRC incorporation. Moreover, the mechanical strength was little affected for up to 20% TRC replacement and was only 12% reduced for 50%TRC incorporation. Therefore, TRC proved to be a very promising supplementary cementitious material for cement replacement.

The objective of this paper is to characterize self-compacting concretes produced with lightweight aggregates (SCLC) available in the Iberian Peninsula. The influence of different compositions on the self-compactability of SCLC is analyzed and some limits are suggested for their formulation. The usual self-compacting tests and additional segregation tests were considered. SCLC of adequate stability and self-compactability could be produced for compressive strengths between 37.4 and 60.8 MPa, density classes D1.8–D2.0 and 490–599 kg/m 3 of fines content with 33% fly ash by weight. Promising results were obtained in the SCLC mechanical characterization.