Accident Rate as a Measure of Safety Assessment in Polish Civil Engineering

Civil engineering is characterised by high volatility with respect to working conditions, which are the source of many threats to worker life and health and contribute to high accident rates. The purpose of this paper is to analyse and evaluate the phenomenon of accidents in Polish civil engineering and define the direction of changes that should occur in the safety area. The studies included in this research covered the years 2004–2018. The following indicators were used to assess the accident rates: (1) The total number of persons injured in workplace accidents and this total divided into fatal, severe, and minor accidents; (2) indicators of frequency of accidents in total and this total divided into minor, severe, and fatal accidents; (3) and an indicator of the severity of accidents. From the analysis of statistical data for the years 200–2018, the changes in accident rate parameters demonstrate the continuous improvement of workplace safety in the Polish civil engineering sector. From the analysed data from the 15 years, a clear decrease in the value of the applied indicators is apparent, including both the number of people involved in accidents and the frequency and severity of accidents

The influence of nanomaterials on the thermal resistance of cement-based composites – a review

Exposure to elevated temperatures has detrimental effects on the properties of cementitious composites, leading to irreversible changes, up to total failure. Various methods have been used to suppress the deterioration of concrete under elevated temperature conditions. Recently, nanomaterials have been introduced as admixtures, which decrease the thermal degradation of cement-based composites after exposure to high temperatures. This paper presents a comprehensive review of recent developments related to the effects of nanoparticles on the thermal resistance of cementitious composites. The review provides an updated report on the effects of temperature on the properties of cement-based composites, as well as a detailed analysis of the available literature regarding the inclusion of nanomaterials and their effects on the thermal degradation of cementitious composites. The data from the studies reviewed indicate that the inclusion of nanoparticles in composites protects from strength loss, as well as contributing to a decrease in disruptive cracking, after thermal exposure. From all the nanomaterials presented, nanosilica has been studied the most extensively. However, there are other nanomaterials, such as carbon nanotubes, graphene oxide, nanoclays, nanoalumina or nano-iron oxides, that can be used to produce heat-resistant cementitious composites. Based on the data available, it can be concluded that the effects of nanomaterials have not been fully explored and that further investigations are required, so as to successfully utilize them in the production of heat-resistant cementitious composites.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

An Investigation of the Mechanical and Physical Characteristics of Cement Paste Incorporating Different Air Entraining Agents using X-ray Micro-Computed Tomography

Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for thermal insulation. In this research, lightweight cement pastes containing fly ash and cement were prepared and tested. In these mixes, three different techniques for producing air voids inside the cement paste were used through the incorporation of aluminum powder (AL), air entraining agent (AA), and hollow microspheres (AS). Several experiments were carried out in order to examine the structural and physical characteristics of the cement composites, including dry density, compressive strength, porosity and absorption. A Hot Disk device was used to evaluate the thermal conductivity of different cement composites. In addition, X-ray micro-computed tomography (micro-CT) was adopted to investigate the microstructure of the air-entrained cement pastes and the spatial distribution of the voids inside pastes without destroying the specimens. The experimental results obtained showed that AS specimens with admixture of hollow microspheres can improve the compressive strength of cement composites compared to other air entraining admixtures at the same density level. It was also confirmed that the incorporation of aluminum powder creates large voids, which have a negative effect on specimens’ strength and absorption.EC/H2020/841592/EU/Ultra-Lightweight Concrete for 3D printing technologies/Ultra-LightCon-3

Cement-Based Composites: Advancements in Development and Characterization

This Special Issue on “Cement-Based Composites: Advancements in Development and Characterization” presents the latest research and advances in the field of cement-based composites. This special issue covers a variety of experimental studies related to fibre-reinforced, photocatalytic, lightweight, and sustainable cement-based composites. Moreover, simulation studies are present in this special issue to provide the fundamental knowledge on designing and optimizing the properties of cementitious composites. The presented publications in this special issue show the most recent technology in the cement-based composite field.EC/H2020/841592/EU/Ultra-Lightweight Concrete for 3D printing technologies/Ultra-LightCon-3

Improvement of left ventricular function after percutaneous coronary intervention in patients with stable coronary artery disease and preserved ejection fraction: Impact of diabetes mellitus

Background: Many patients with stable coronary artery disease (CAD) have no visual segmental wall motion abnormalities and a left ventricular (LV) ejection fraction (LVEF) ≥ 50% at rest despite significant coronary artery stenosis. Here, the aim was to determine the impact of percutaneous coronary intervention (PCI) on LV function assessed by enhanced echocardiography in patients with stable CAD with or without diabetes mellitus type 2 and a preserved LVEF.Methods: Sixty-six consecutive patients with CAD and LVEF ≥ 50%, admitted to the hospital for planned coronary angiography, were prospectively assessed. PCI was performed for coronary artery stenosis > 70%. CAD extent was assessed using SYNTAX and EXTENT scores. To assess LV function, LVEF, global longitudinal strain (GLS), and LV peak systolic myocardial velocity (S’) were measured and Tei index was calculated before and 3 months after PCI.Results: Before PCI, LVEF, GLS, and Tei index were significantly worse in diabetic patients. LV functional indices improved significantly after PCI in all patients (p < 0.001). Multivariate linear regression analyses were performed to evaluate the impact of selected factors on LV function after PCI expressed as changes (D) of LVEF, GLS, S’, and Tei index. LV function improvement expressed as DGLS was associated only with SYNTAX score. Higher SYNTAX scores were related to greater GLS improvement (b = 0.003, 95% confidence interval: 0.0004–0.005; p = 0.02).Conclusions: Percutaneous coronary intervention significantly improved LV function in diabetic and non-diabetic CAD patients with preserved LVEF. Enhanced echocardiography allowed an assessment of subtle changes in LV function

Influence of Nanosilica on Mechanical Properties, Sorptivity, and Microstructure of Lightweight Concrete

This study presents the results of an experimental investigation of the effects of nanosilica (NS) on the strength development, transport properties, thermal conductivity, air-void, and pore characteristics of lightweight aggregate concrete (LWAC), with an oven-dry density 1 wt.%). NS contributed to compaction of the LWAC matrix and a modification of the air-void system, by increasing the amount of solid content and refining the fine pore structure, which translated to a noticeable improvement in mechanical and transport properties. On the other hand, NS decreased the consistency, while increasing the viscosity of the fresh mixture. An increment of superplasticizer (SP), along with a decrement of stabilizer (ST) dosages, are thus required.EC/H2020/841592/EU/Ultra-Lightweight Concrete for 3D printing technologies/Ultra-LightCon-3DDFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Solution of Inverse Problem by Infinite Boundary Elements and the Level Set Method

In this paper the inverse problem for the electric field is investigated. In order to solve the forward part of such problem we use the boundary element method coupled with infinite elements. The inverse problem is based on the gradient technique and the level set method. Such task can be considered as application of the electrical impedance tomography. Investigated structure is given in Fig. 1. We want to detect the closed curve localised on upper part of this plot

The Effect of Lightweight Concrete Cores on the Thermal Performance of Vacuum Insulation Panels

The performance of vacuum insulation panels (VIPs) is strongly affected by several factors, such as panel thickness, design, quality of vacuum, and material type. In particular, the core materials inside VIPs significantly influence their overall performance. Despite their superior insulation performance, VIPs are limited in their widespread use as structural materials, because of their low material strength and the relatively expensive core materials. As an alternative core material that can compensate these limitations, foamed concrete, a type of lightweight concrete with very low density, can be used. In this study, two different types of foamed concrete were used as VIP core materials, with their effects on the thermal behavior of the VIPs having been evaluated using experimental and numerical methods. To confirm and generate numerical models for VIP analysis, micro-computed tomography (micro-CT) was utilized. The obtained results show that insulation effects increase effectively when panels with lightweight concrete are in a vacuum, and both foamed concrete types can be effectively used as VIP core materials.BMBF, 13XP5010B, Verbundprojekt: Multifunktionale Leichtbetonbauteile mit inhomogenen Eigenschaften (MultiLC) - Teilvorhaben: Mechanische, Bauchemische und Bauphysikalische UntersuchungenEC/H2020/841592/EU/Ultra-Lightweight Concrete for 3D printing technologies/Ultra-LightCon-3