Titania nanoparticles are intensely studied for photodegradation applications. Control of nanoscale morphology and microstructural properties of these materials is critical for photocatalytic performance. Uniform anatase-type TiO₂ nanoparticles were prepared by the sol-gel process using titanium isopropoxide as precursor. Controlled annealing up to 400 °C established crystallization and particle size ranging between 20 and 30 nm. Detailed thermal examination reveals that anatase phase transformation into rutile is affected by the annealing temperature and by the initial particle size. The anatase to rutile phase transformation occurs in the nanoparticles at 550 °C. The Total Reflection X-ray Fluorescence (TXRF) study of the anatase nanoparticles shows a shift towards higher energy in the Ka Ti line of 10 eV, related to structural defects. These features were discussed in the photocatalytic behavior of several cement-based materials modified with the so-prepared anatase nanoparticles. The photocatalytic activity of the anatase-type TiO₂/cement mortar system is evaluated from the degradation of Methylene Blue (MB) under UV irradiation, monitored through the absorbance at 665 nm. The results show that the photocatalytic composites exhibit up to 76.6% degradation efficiency. Mechanical testing of the nano-TiO₂ modified cementitious composites evinces a moderate reinforcement of the strength properties at long ages.

This work aims to investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the strength and electrical properties of cement mortar. MWCNTs were added to cement mortar in four different concentrations: 0.00 wt.%, 0.01 wt.%, 0.015 wt.%, and 0.02 wt.% by the mass of cement. The consistency, density, setting time and compressive and flexural strength of mixes were tested and analyzed at 28 and 90 days curing time. Mechanical performance tests confirm an increase of 25% and 20% in the ultimate compressive and flexural strength respectively, which results from MWCNT 0.02 wt.% loading at 90 days curing time. The resistivity measurements in mortars with 0.01 and 0.015 wt.% MWCNT loading result up to 10% decrement at both 28 and 90 days curing. Activation energy calculations show fully accordance with these statements, resuming that 0.01 wt.% MWCNT appears to be the most effective loading scheme to produce certain conductivity enhancement in cement mortar.

A wide range of granular soils were laboratory prepared as base and sub-base materials in flexible pavements technology. The samples were produced according to the requirements defined in the Spanish General Technical Specifications for Roads and Bridge Works (PG-3), which links to the American Unified Soil Classification System (USCS). The lab-prepared granular soils were characterized by means of particle size distribution, Atterberg limits, non-standard Proctor and California Bearing Ratio (CBR). The determination of CBR has been performed considering the evolution of the penetrability up to one, two, three and four days of immersion. The results show that repeatable values within an acceptable degree of accuracy can be obtained, which indicates good quality laboratory testing conditions. Detailed analytical study is performed on the relationship between CBR index and maximum dry density, finding that a predicting model can be obtained from density variation to estimate representative CBR values for design. The results were compiled in a decision matrix using the Analytical Hierarchy Process (AHP) to estimate a California bearing ratio value (CBR) versus maximum dry density.

Today, the new pavement management tools encourage preventive action, whereas more traditional approaches focus on acting on observed damage. An adequate initial evaluation is essential to properly manage pavement maintenance. In this regard, non-destructive tests such as deflection tests make it possible to obtain first-hand information without altering the condition of the pavement, and their use is becoming increasingly more common. This paper presents a study of the structural evaluation of rigid pavements based on measured deflections. Several aspects are identified which will make it possible to improve these procedures. A 62-kilometre stretch a motorway in Mexico has been used as a case study. A campaign of on-site measurements was carried out using a Falling Weight Deflectometer (FWD). The deflection values were used in several iterative methods with calculation programs and manual analytical methods, comparing the results obtained. The elastic moduli of the pavement layers were determined. These are the main parameters for calculating the remaining life of the structure, which facilitate decision-making around pavement management. The results obtained in this study demonstrate the usefulness of back-calculation methods for analysing the structural condition of rigid pavements as an initial stage in the development of pavement management systems. The conclusions validate the use of back-calculation programs in the structural analysis of rigid pavements, by comparing the results obtained with manual analytical methods.