Documents published in Scipedia

• Tuning the incompatibility between recycled plastic aggregates and cement matrix with polymer-nano silica hybrids

  Q. Zeng, A. Al-Mansour

  DBMC 2023.

  
  

  Abstract

  Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental benefits. However, the soft plastics and rigid cement matrix can naturally induce the great aggregate-matrix incompatibility, which results in the degradation of engineering properties of cement-based materials containing recycled plastic aggregates (RPAs). To overcome this shortage, this work reports a strategy of tuning the cement matrix with polymer-nano silica (P-nS) hybrids. Ethylene vinyl acetate (EVA) and recycled polypropylene (PP) were selected as the coating polymer and RPA, respectively. Density, strength, water sorptivity and carbonation resistance were measured to assess the physical and mechanical properties of the mortars with recycled PP particles. Microstructure was analyzed using scanning electron microscopy (SEM) with backscattered electron (BSE) and energy-dispersive X-ray spectroscopy (EDS). Results showed that the addition of P-nS hybrids into cement decreases density, mitigates strength reduction, obstructs water sorption, but have positive and negative effects on carbonation resistance of the cement mortars with RPA. The P-nS hybrids build the organic–organic links between the cement matrix and RPA, and coordinate their deformations. The findings of this work proof the proposed strategy of tuning the compatibility between soft aggregates and rigid matrix with the engineered microstructure towards enhancing the recyclability of waste plastics in construction materials.

  Abstract
  Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental [...]

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• Recycling of Polypropylene Fibre Reinforced Concrete: Use of Recycled Aggregate and Recovered Fibre in New Concrete

  G. Liu, N. Tošić, A. de la Fuente

  DBMC 2023.

  
  

  Abstract

  The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete (PPFRC) in new concrete production. The mechanical properties were compared between a parent concrete, polypropylene fibre reinforced recycled aggregate concrete (PPRAC), and recovered polypropylene fibre concrete (Re-PPRFC). All concretes were designed to have the same compressive strength and slump. The parent concrete was produced with 9 kg/m3 of polypropylene fibre. After recycling, the RA and RF were collected and new concretes with RA and RF, PPRAC and PPRFC, respectively, were produced with the same fibre content as the parent concretes. The strain-stress relationship in compression and residual tensile strength were tested. The results obtained for PPFRC, PPRAC and rePPRFC were compared. The results show that the RA and RF obtained by PPFRC recycling can benefit new concrete production.

  Abstract
  The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete [...]

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• Numerical Simulation on the Influences of Wind Pressure on Jet Characteristics of Shotcrete

  S. Zhang, Y. Zhang, K. Wu, X. Kong

  DBMC 2023.

  
  

  Abstract

  A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding with a wall based on computational fluid dynamics theory, in which concrete was regarded as a Bingham fluid. The influences of wind pressures、 pumping speeds、 air incident angles and rheological parameters on five characteristic parameters including spouting velocity, jet velocity, jet trajectory, collision velocity and distribution of shotcrete on the wall were analyzed in depth. Results showed that concrete was gradually mixed well with air in the nozzle with an increasing average velocity, and the increase of velocity was most pronounced in the contraction section of nozzle. With the increases of wind pressures and pumping speeds, the spouting velocity and spouting mass of concrete both increased. Higher wind pressure and pumping speed led to larger jet velocity and more concentrated distribution, resulting in significantly longer jet distance, higher collision velocity and larger distribution area. The collision velocity and volume fraction of concrete on the wall were distributed symmetrically along Y axis, shifting towards the direction of gravity. With the increases of air incident angles, the spouting velocity and spouting mass of concrete both decreased, the shifting to gravity is weakened and the volume fraction decreased first and then increased. When plastic viscosity decreased, the spouting velocity and spouting mass of concrete both increased, accompanying with a higher jet velocity, a longer spraying distance and a larger distribution area.

  Abstract
  A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding [...]

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• Effect of Pre-calcination of Lead-zinc Tailings on the Activation of Blast Furnace Slag

  J. Ou, Z. Luo, Y. Mu

  DBMC 2023.

  
  

  Abstract

  Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs were pre-calcined at different temperatures and then explored whether it is capable of being the activator of slag. The effects of pre-calcination on the phase composition of LZTs were elucidated by XRD. The compressive strength of LZTs-activated slag pastes was investigated, and the mineral composition and microstructure of the pastes were detected by XRD and SEM. The results imply that with the elevating of heating temperature from 500 ℃ to 1000 ℃, the dolomite in LZTs decompose into CaO and MgO, and the oxidation of pyrite resulted in the formation of Fe2O3 and gaseous SO3, then SO3 reacted with a part of formed CaO to produce CaSO4. The resulting CaSO4 and CaO can become the sulfate activator and alkaline activator of slag, respectively. The LZTs-activated slag pastes prepared with the LZTs preheated at 800 ℃ exhibit the highest strength at 90 d, which yield 24 MPa. The hydration products of LZTs-activated slag were ettringite and calcium silicate hydrates (C-S-H gel). Large amounts of dense C-S-H gel bond together, connecting most of the ettringite networks into a whole, thus forming a dense structure and effectively improving the strength of LZTs-activated slag. The outcome of this study provides a potential disposing or reusing approach of the large amounts of LZTs.

  Abstract
  Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs [...]

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• Probability Durability Assessment of Existing Concrete Structures in Carbonation Environment

  H. Gu, J. Yao, Z. Meng

  DBMC 2023.

  
  

  Abstract

  In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. This paper presents a methodology for assessing the probability durability of existing structures, taking into account the nondestructive testing results and the target reliability index. The initial step involves introducing a correction coefficient into the carbonation and corrosion development theory model. This coefficient is necessary to account for the correction associated with the corrosion monitoring of steel. The values of this coefficient should be determined based on the actual testing results, specifically considering the presence of reinforcing steel corrosion. Next, a probability expression is proposed using the measured results of probability characteristics and the target reliability index. This approach takes inspiration from the design-value method and the existing theory of structure reliability. It also takes into account the specific variables of concrete protective cover thickness and the compressive strength as the fundamental random variables. The residual working life can be calculated as the outcome of a durability assessment through quantitative analysis. This calculation can serve as a valuable reference for the maintenance program.

  Abstract
  In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. [...]

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• Overview on Testing Method of Internal Damage to Special-shaped Stone Components in Palace Museum

  Y. Qian, F. Qi, K. Niu

  DBMC 2023.

  
  

  Abstract

  Irregular historic stone components are very important parts of the ancient architecture in the Palace Museum. They have been subjected to deteriorations from surface to interior under the combined effects of many factors such as wetting and drying, salt dissolution and recrystallization, selfload, external load, and environment action. The internal damages in these stone components are difficult to detect but are crucial for the assessment of the intact of these components. In order to detect the internal damage of stone components, especially the special-shaped stone components, which cannot be tested by comment methods. Taking evaluation on preservation status of stone components in a qualitative and quantitative way， with application of ultrasonic computerized tomography and regular inspection, a convenient, safe, economical, efficient, and readable method for detecting the internal damage of irregular stone components can be established in order to detect any safety hazards as early as possible and provide data support for assessment and conservation, achieving a better preventive conservation.

  Abstract
  Irregular historic stone components are very important parts of the ancient architecture in the Palace Museum. They have been subjected to deteriorations from surface to interior [...]

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• Evaluating the Future Moisture Performance of the Stucco-Clad Wall Assembly in Selected Canadian Cities

  O. Zhe, X. Xiao, H. Ge, M. Lacasse

  DBMC 2023.

  
  

  Abstract

  Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed to such climate could experience a higher moisture load than in the past, which could have a negative impact on its performance in the long run. The stucco-clad wall assembly, which has been widely employed in the construction of low-rise residential buildings throughout Canada may not be adequately designed to be resilient to the future climate. Thus, in the study described in this paper, the future moisture performance of the stucco-clad wall assembly located in two Canadian cities with different levels of moisture load, i.e., Vancouver and Calgary, subjected to projected future climate is investigated. The analysis includes two phases: conducting watertightness for a full-scale stucco wall specimen to determine the relationship between the climate data and the moisture load in the wall assembly and implementing hygrothermal simulations using the relationship obtained from the watertightness test for the performance assessment. Mould growth index at the exterior surface of the oriented strand board of stucco-clad wall assembly for the historical and projected future time periods is compared and discussed.

  Abstract
  Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed [...]

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• Analysis of Thermal Bridges in Concrete and Cross-Laminated Timber (CLT) Constructions: A Numerical Study

  A. Zegeye, F. Tariku

  DBMC 2023.

  
  

  Abstract

  The thermal efficiency of a building envelope relies on various factors, including insulation resistance, continuity, the thermal conductivity of structural materials, and the presence of thermal bridges. This study focuses on studying the thermal performance of thermal bridge details in two construction types: concrete and Concrete and Cross-Laminated Timber (CLT). For the study, two common building envelope details with significant thermal bridges are considered, balcony and intermediate wall-to-floor connections. Utilizing the finite element program COMSOL Multiphysics, hourly transient simulations were conducted over a one-year period to assess the heat loss/gain associated with thermal bridges, considering daily, seasonal, and annual heat flow for two diverse climatic conditions (hot weather Houston-Climate Zone 2 and cold weather Toronto-Climate Zone 6). The findings demonstrate that thermal bridges constructed from CLT outperformed those made of concrete. In Toronto, the annual heat flow for the concrete balcony was 146% higher compared to CLT, while in Houston, it was 67% higher. However, this trend was significantly reduced for the wall-to-floor detail, with a concrete detail showing a 13% increase in heat flow for Toronto and a 7% decrease in annual heat flow for Houston. Furthermore, the dynamic analysis revealed notable heat flow magnitude changes in the balcony detail, highlighting the importance of thermal conductivity, while the wall-to-floor detail exhibited dampening fluctuations in heat flow, emphasizing the material's heat capacity importance in this context.

  Abstract
  The thermal efficiency of a building envelope relies on various factors, including insulation resistance, continuity, the thermal conductivity of structural materials, and [...]

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• Use of Machine Learning in Processes Optimization for Drinking Water Treatment Plant Butoniga (Istria, Croatia)

  G. Volf, S. Zorko, I. Čule

  DBMC 2023.

  
  

  Abstract

  Drinking water treatment plant Butoniga is located in central Istria (Croatia) downstream of the Butoniga reservoir. The Butoniga reservoir is an artificial lake created in 1987 with two main objectives: 1) protection from adverse water impacts, and 2) drinking water supply. The operation of the drinking water treatment plant is mainly related to the tourist season, and the 5.000.000 m3 of produced and distributed drinking water annually, 3.000.000 m3 is produced and distributed during June 15 to September 15, when the raw water quality in the Butoniga reservoir is the worst. Regarding this, main problem with Butoniga reservoir and thus drinking water treatment plant appear in summer months when water temperature is the most critical parameter and raw water for the treatment process must be captured from the lowest layer of the reservoir which have increased concentrations of Mn, Fe, NH4 and lower pH values and thus influence on the treatment processes. To deal with this problem, model predicting Mn, seven days in advance is build using machine learning approaches. Build model have high accuracy compared to the measured data, with a good prediction of the peak values. As such, obtained model can help in optimization of the treatment processes which are depending on the quality of raw water, and overall, in sustainability and management of the drinking water treatment plant Butoniga.

  Abstract
  Drinking water treatment plant Butoniga is located in central Istria (Croatia) downstream of the Butoniga reservoir. The Butoniga reservoir is an artificial lake created in [...]

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• Proposal of Soundness Index for Existing RC Apartment Building for Proper Management Through Visual Monitoring

  N. Tsuchiya, N. Mishima, K. Nemoto, K. Matsuzawa, K. Nakada, T. Kage, H. Tanano

  DBMC 2023.

  
  

  Abstract

  A numerical index for housing complexes of reinforced concrete maintained properly was proposed. First, based on the literature review, deterioration grade and a method for evaluating soundness for RC housing complexes, which determined by visual inspection, was proposed. And then, accelerated deterioration experiments of small RC wall and investigation of existing buildings were conducted. From the study, a correlation between the deterioration grade determined visually and rebar corrosion grade was confirmed. By using building health H(t), that is proposed as index of soundness for existing RC housing complexes, RC housing complexes whose age were 46 to 69 years were evaluated. From the study, it was confirmed how much deterioration the evaluation value indicates.

  Abstract
  A numerical index for housing complexes of reinforced concrete maintained properly was proposed. First, based on the literature review, deterioration grade and a method for [...]

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