An experimental programme was carried out on the shear strength behaviour of sandy and clayey soils reinforced with short, randomly distributed, polypropylene (PP) microfibres. The influence of fibre texture, fibre content, fibre length and normal stress level was investigated by means of direct shear tests. The best procedure to mix the soil with the fibres in order to achieve homogeneous and isotropic samples is described. This study shows that fibres increase the shear strength and significantly modify the shear stress displacement behaviour of the tested soils. Shear strength increases with increase in fibre content, fibre length and displacement. No appreciable advantage is achieved by using crimped (texturised) fibres as far as shear strength is concerned. Furthermore, mixture is achieved with greater difficulty when compared with straight fibres. There is an increase in both the apparent cohesion and the angle of shearing resistance of soils, owing to the short PP microfibres. The fibre contribution is especially significant for low normal stress levels. Despite the occurrence of some fibre damage, damaged fibres are still suitable for reinforcement.

The present work focuses on the further development of a new family of geopolymers obtained by the alkaline activation of a binder. The aim is to find a viable alternative to concrete that can be used in civil construction. Regarding the influence of the curing temperature on this type of mixture, the recommendations in the existing literature are different for fly ash, ground granulated blast-furnace slag, and metakaolin-based geopolymers. While for fly ash and slag, increasing the curing temperature above 60 °C is reported to be advantageous, for metakaolin geopolymers, the opposite is reported. In this context, the objective of this work is to evaluate the mechanical strength of several metakaolin-based geopolymer specimens subjected to different curing temperatures (10, 15, 20, 30, 40 and 50 °C). Furthermore, several stress-strain diagrams are also shown. Based on the results, we recommend using curing temperatures below 30 °C in order to avoid reducing the strength of metakaolin-based geopolymers. Curing at 50 °C, relative to room temperature, results in a reduction of more than 35% in flexural strength and a reduction of more than 60% in compressive strength. Regarding the behavior of the geopolymers, it was found that the strain, at the ultimate stress, is about 2 to 2.5 times the strain of an equivalent cement mortar.

Scale models are a powerful means of studying engineering problems; they are versatile because it is easier to make alterations, relatively inexpensive because less space is required, as well as requiring less time for construction, instrumentation, and testing. This paper describes the work carried out in an experimental study on the behaviour of geotextile-reinforced, brick-faced soil retaining walls by means of one-fifth (1/5) scale models under normal gravity (1g) and compares the model results with data from a previous research programme on prototype-scale walls. The modelling was based on the principles of similarity and dimensional analysis. An experimental apparatus was designed and suitable materials were selected taking into account the modelling requirements. Comparisons between the model results and those obtained in previous prototype-scale tests were undertaken. An acceptable degree of agreement was achieved.

This paper presents some important results of a full-scale experiment with a soil reinforced with short, randomly distributed polypropylene (PP) microfibres. A trial embankment 50 m long × 10 m wide with different sections of different reinforcing characteristics was built to verify the feasibility of this type of construction, and to study the most suitable procedures on site for both embankment construction and soil–fibre mixing. The experiment also aims at the validation of laboratory studies. The construction and quality control of the embankment layers are described, with special attention given to the mixture production. The full-scale experiment showed a reinforced soil behaviour broadly in agreement with the results of the laboratory studies. Soil reinforced with thinner fibres showed higher compressibility but also a higher recovery capacity when compared with unreinforced soil or soil reinforced with thicker fibres. This composite material complies with the stiffness requirements for several construction applications, proving to be a suitable material for construction.

Geopolymer materials are characterized by their high durability and low carbon dioxide emissions, when compared with more traditional materials, like concrete made from ordinary Portland cement. These are interesting advantages and might lead to a more sustainable construction industry. The aim of this study is the characterization of the mechanical behavior of the materials obtained by the activation of metakaolin. The activator is a mixture of sodium hydroxide with sodium silicate in different proportions. The influence of the composition of activator is studied. For the analysis of the mechanical properties of the different mixtures two different types of tests were performed, bending tensile strength tests and compressive strength tests. The results show that an activator with not less than 300 g of sodium hydroxide and not exceeding 600 g of sodium silicate per 750 g of metakaolin gives the best results, for both tensile strength and compressive strength.