Transition Zone Enhancement with Waste Limestone Powder as a Reason for Concrete Compressive Strength Increase

Modification of concrete with waste materials is an increasingly common process, and they are primarily used as a partial substitution for cement. In the case of inert or nearly inert additions according to EN 206, the effectiveness of such a modification mainly concerns ecological aspects and, only to a small extent, mechanical properties. This article analyses the effect of modifying cement concrete with waste limestone powder as a partial substitution for fine aggregate. The analysed waste arises as a result of the accumulation of dust produced during the initial preparation of aggregate for the production of hot mix asphalt (HMA). In order to analyse the effect of waste on compressive strength, an experimental design was prepared with variable substitution levels and variable water/cement ratios. Compressive strength tests were performed after 28 to 90 days. Statistical analysis of the results was performed. Microscopic evaluation of the fractures of the samples was carried out to clarify the mechanism of transition zone enhancement, which resulted in an increase of compressive strength of the composite.

Analysis of the base of a reclamation dam when operating in a pressure variable mode

A calculation was carried out and a numerical modeling of the foundation of an hydromeliorative dam was carried out during its operation in a pressure-variable mode, using the MIDAS GTX NX software package, by building a computational model based on the real engineering-geological state of the object, when horizontal stresses (kN/m2) depending on the variable water level in the upstream and downstream, a mathematical model of the process is obtained from the named factors and the degree of influence of each of them is revealed.

The Coastline Evolution Model 2D (CEM2D) V1.1

Coasts are among the most intensely used environments on the planet, but they also present dynamic and unique hazards, including flooding and erosion. Sea level rise and changing wave climates will alter patterns of erosion and deposition, but some existing coastline evolution models are unable to simulate these effects due to their one-dimensional representation of the systems or the sediment transport processes. In this paper, the development and application of the Coastline Evolution Model 2D (CEM2D) are presented, a model which incorporates these influences. The model has been developed from the established CEM and is capable of simulating fundamental cause–effect relationships in coastal systems. The two-dimensional storage and transport of sediment in CEM2D, which are only done in one-dimension in CEM, mean it is also capable of exploring the influence of a variable water level on sediment transport and the formation and evolution of morphological features and landforms at the mesoscale. The model sits between one-dimensional and three-dimensional models, with the advantage of increased complexity and detail in model outputs compared to the former but with more efficiency and less computational expense than the latter.

Strength of Polypropylene Fiber Reinforced Cement Mortar Composites with Variable Water/Cement Ratio

For cement mortars the reinforcement techniques by randomly distributed short fibers, contribute highly to their micro-cracking stabilization and to improvement of their flexibility and tensile strength. Among the wide different types of short fiber reinforcement that have been used in the past for mortars, those made of steel, polymers and natural fibers dominate the area. It is a common sense that the reinforcement of mortars by polypropylene fibers (PP) is considered a very efficient method for reducing their curing shrinkage and enhanced toughness and strength of un-reinforced cemented material. In this study, PP fiber reinforced mortars were prepared with specific composition but with variable water to cement (W/C) ratio and appropriate superplasticizer amounts. For all mixtures their workability, air content and flexural and compressive strengths were measured. In conclusion it can be stated that even though W/C ratio of mortars is varied considerably, and also do their mechanical response, it is possible by appropriate mixture designing, for all studied compositions to produce suitable mortars that can be used successfully in a wide range of demands and applications, achieving high mortar strengths and ideal workability behavior.