• Energy Research
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One effective method to minimize the increasing cost in the construction industry is by using coal bottom ash waste as a substitute material. The high volume of coal bottom ash waste generated each year and the improper disposal methods have raised a grave pollution concern because of the harmful impact of the waste on the environment and human health. Recycling coal bottom ash is an effective way to reduce the problems associated with its disposal. This paper reviews the current physical and chemical and utilization of coal bottom ash as a substitute material in the construction industry. The main objective of this review is to highlight the potential of recycling bottom ash in the field of civil construction. This review encourages and promotes effective recycling of coal bottom ash and identifies the vast range of coal bottom ash applications in the construction industry.

In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production.

Greece is divided into three earthquake hazard zones: Zone I, Zone II and Zone III. In the present research work, the same building in the three seismic zones in Greece was modeled, analyzed and dimensioned. Then, the construction cost of its structural body was estimated. The building modeling was performed in SAP2000 using frame elements. The analysis of the building was performed by dynamic spectral analysis methods using the design spectrum EC8. A five-story building with a standard rectangular floor plan per floor was used. The purpose of this research paper is to demonstrate whether the cost of construction of a load-bearing body of a reinforced concrete (R/C) building is influenced by the area of an earthquake hazard through a comparative analytical estimation of construction costs. It was determined if this impact is important and to what extent. Helpful conclusions were drawn in relation to the influence of seismicity on the construction cost of the load-bearing structure of R/C buildings. Furthermore, the probable environmental impact was examined.

Ordinary Portland cement (OPC) is the primary binder of concrete, accounting for approximately 5% to 7% of greenhouse gas (GHG) and carbon dioxide (CO2) emissions with an annual production rate of more than 4 billion tons. It is critical to reduce the carbon footprint of concrete without sacrificing its performance. To this end, this study focuses on the use of water hyacinth ash (WHA) as a pozzolanic binder in the production of concrete as a partial replacement for cement. Four mixes are designed to achieve C-25-grade concrete with varying proportions of cement replacement with WHA of 0%, 5%, 10%, and 15% of the cement weight. Extensive experiments are performed to examine the workability, strength, durability, and microstructure of concrete specimens. The test results confirm that incorporating WHA in concrete improved its workability, strength, and durability. The optimal results are obtained at the maximum OPC replacement level, with 10% WHA. The use of WHA as a partial replacement for cement greatly reduces the energy required for cement production and preserves natural resources. More research is needed to use WHA on a large scale to achieve greater sustainability in the concrete industry.

Abstract Sustainable retrofitting of existing buildings is a prerequisite for achieving climatic and energy objectives in the EU. Thus, practical tools supporting the evaluation and decision-making process when planning retrofit interventions are required. In specific areas, in addition to energy efficiency, the improvement in building resilience to natural hazards is requested; in several European regions, seismicity poses a significant hazard. This study aims to analyse the state-of-the-art of the integrated methods for the implementation of structural and energy retrofitting. The work consists of reviewing available tools, international sustainability protocols, and methods specifically developed for combined energy and seismic assessment. In the first group of methods, assessment is independently referred to specific criteria for energy performance and seismic safety, quantified according to available codes. Besides, in a second group, integrated evaluation is achieved considering ‘equivalent’ initial or life-cycle costs associated with energy consumption and seismic vulnerability. The collected methods were evaluated for qualitative requirements for optimal integration, such as multidisciplinary, life-cycle approaches, and other indicators. Finally, a critical evaluation is provided, highlighting what can be used for future developments toward a sustainable and resilient retrofitting of existing European buildings.

This paper assessed the service life of RC bridges subjected to carbonation under a changing climate based on time-dependent reliability analysis. First, a simplified carbonation model and the corresponding incremental method were briefly reviewed. Then, the fatigue damage prediction model and climate model were briefly introduced. Afterward, the Monte Carlo simulation-based time-dependent reliability analysis procedure for service life assessments was presented, which integrated the carbonation depth prediction model, fatigue damage prediction model and climate model. Based on the analysis procedure, a comprehensive case study was conducted to estimate the effects of climate change, fatigue damage, concrete cover thickness and concrete grade on the service life under different reliability levels. The case study showed that the service life under a reliability level of 2 is around half of that under the reliability level of 1. Under the reliability level of 1.5, the service life under RCP8.5 (a high emission scenario defined by Intergovernmental Panel on Climate Change) can be 28 years shorter than that under no climate changes. The service life at girder top undergoing compressive fatigue damage can be 49% shorter than that without fatigue damage and 25 years shorter than that at girder bottom undergoing tensile fatigue damage. The service life at girder top with a concrete cover thickness of 45 mm can reach 2.6 times that with a concrete cover thickness of 25 mm. The service life of C50 concrete can reach approximately 2–3 times that of C30 concrete. These findings inform civil engineers that for existing RC bridges, the effects of climate change and fatigue damage should be properly considered when the remaining service life of RC bridges is concerned. Moreover, for planned RC bridges, higher concrete grade and thicker concrete cover are two effective choices to achieve a longer service life.

Nowadays, the increasing demand for concrete is causing serious environmental impact including pollution and waste generation, rapid depletion of natural resources, and increased CO2 emission. Incorporating natural fibers in concrete can contribute toward environmental sustainability. This paper is concerned with the use of natural fibers obtained from the plant species Phragmites australis (PA). The plant is invasive, and rapidly grows abundantly along rivers and waterways, causing major ecological problems. This research is part of a wide range investigation on the use of natural fibers produced from the stem of PA plants in concrete. Using a machine, plant stems were crushed into fibers measuring 40 mm in length and 2 mm in width, and treated with 4% NaOH solution for 24 h. A total of four concrete mixes were prepared with varying additions of treated fibers, ranging from 0% to 1.5% (by volume) with water to cement ratio of 0.5% (by volume). Concrete specimens were tested at 3, 7, and 28 days. Testing included compressive strength, density, total water absorption, and capillary water absorption. The results show that incorporating PA natural fibers reduces the water absorption by total immersion and capillary action by up to 45%. Moreover, there is a negligible decrease in concrete density and strength when fibers were added. It is concluded that adding up to 1.5% natural PA fibers to concrete is a feasible strategy to produce an eco-friendly material which can be used in the production of sustainable building material with adequate mechanical and durability performance.