Mix Design
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2022 ◽  
Vol 320 ◽  
pp. 126218
Author(s):  
Rawaz Kurda ◽  
Ahmed Salih ◽  
Pshtiwan Shakor ◽  
Peshkawt Saleh ◽  
Rayed Alyousef ◽  
...  

Buildings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 65
Author(s):  
Junbo Sun ◽  
Jiaqing Wang ◽  
Zhaoyue Zhu ◽  
Rui He ◽  
Cheng Peng ◽  
...  

High-strength concrete (HSC) is a functional material possessing superior mechanical performance and considerable durability, which has been widely used in long-span bridges and high-rise buildings. Unconfined compressive strength (UCS) is one of the most crucial parameters for evaluating HSC performance. Previously, the mix design of HSC is based on the laboratory test results which is time and money consuming. Nowadays, the UCS can be predicted based on the existing database to guide the mix design with the development of machine learning (ML) such as back-propagation neural network (BPNN). However, the BPNN’s hyperparameters (the number of hidden layers, the number of neurons in each layer), which is commonly adjusted by the traditional trial and error method, usually influence the prediction accuracy. Therefore, in this study, BPNN is utilised to predict the UCS of HSC with the hyperparameters tuned by a bio-inspired beetle antennae search (BAS) algorithm. The database is established based on the results of 324 HSC samples from previous literature. The established BAS-BPNN model possesses excellent prediction reliability and accuracy as shown in the high correlation coefficient (R = 0.9893) and low Root-mean-square error (RMSE = 1.5158 MPa). By introducing the BAS algorithm, the prediction process can be totally automatical since the optimal hyperparameters of BPNN are obtained automatically. The established BPNN model has the benefit of being applied in practice to support the HSC mix design. In addition, sensitivity analysis is conducted to investigate the significance of input variables. Cement content is proved to influence the UCS most significantly while superplasticizer content has the least significance. However, owing to the dataset limitation and limited performance of ML models which affect the UCS prediction accuracy, further data collection and model update must be implemented.


Author(s):  
Rayane de Lima Moura Paiva ◽  
Adriana Paiva Souza Martins ◽  
Lucas Rosse Caldas ◽  
Oscar A.M. Reales ◽  
Romildo Dias Toledo Filho

The incorporation of sustainable materials in the civil construction sector has grown in recent years to minimize environmental impacts. Among these materials, the use of earth, a local raw material that does not require much energy for its processing, appears as an advantageous and promising alternative. Earth mortars stabilized with natural binders, when compared to conventional mortars, can have technological, economic and environmental advantages. The objective of this work was to develop an earth-based mortar stabilized with mineral binders using a 1:3 binder to aggregate mass proportion, and to evaluate its fresh and hardened state properties, as well as its environmental impacts using Life Cycle Assessment (LCA) with a cradle to gate scope. The selected materials were divided in four groups: (i) cement, hydrated lime, fly ash and metakaolinite (binders), (ii) natural sand and coarse fraction of the earth (aggregates), (iii) calcium chloride and superplasticizer (additives) and (iv) water. In the matrix formulation the clay fraction from earth constituted the majority of the binder. The selection of supplementary cementitious materials as additional binders provided improvements in workability and mechanical properties of the mortar. A mix design was carried out using different cement (5; 7.5 and 10%) and fly ash (11; 13.5 and 16%) mass percentages. The water/binder material ratio, superplasticizer content and calcium chloride content were 0.65; 2% and 1%, respectively. The results showed that an increase in fly ash content combined with a decrease in cement content provided an increase in workability and a decrease in mechanical properties of mortars. Nevertheless, the mechanical performance of the mortars remained above the minimum values prescribed in Brazilian construction codes. From the results analysis it was concluded that partial replacement of cement by fly ash provided greater workability in the fresh state and reduced the environmental impacts of the earth-based mortar.


Author(s):  
Chems Anwar ◽  
Abdeslam Benamara ◽  
Abdelhak Kaci

This preliminary work deals with potential use of additive manufacturing to print a bio-based composite. For this, mixture of clay and flax fibers was used. First, we proceeded to the optimization of the printability conditions by ensuring that the water dosage allows a good extrusion with a continuous volume flow rate. Moreover, the yield stress obtained must allow to deposit several layers without loss of stability. This criterion was verified and then we printed a square element of 20 cm length where 4x4x16cm3 specimens were cut and used to evaluate bending strength. We have shown that under some conditions we are able to print with different layers this composite. To improve the limit height of a printed element, additional tests are necessary to increase the resistance of this type of composite. This study will be continued by Optimizing mix design using other additives and introducing of reinforcement.


Author(s):  
Daria Ardant ◽  
Coralie Brumaud ◽  
Guillaume Habert

Locally available and with infinite recycling possibilities, the use of earth as building material leads to one of the lowest environmental impacts in the construction sector. Recent advances in the earth materials field have been made based on concrete and ceramics technologies to facilitate its uses in dense areas. It is possible to modify clay particle interactions and the material's whole behavior by adding inorganic dispersants and flocculants into clay paste. Earth becomes easy to cast and unmold into formworks, and by removing cement in its composition, poured earth can reach a low CO2 emission rate. Even if this technology is promising, further work has to be performed, as it cannot be implemented on earth from excavation sites with high variability. Tackling the clay nature variability is now the main issue to push this product on the market with robust properties. This research investigates the robustness of the poured earth binder. In this way, several clays (three montmorillonites, two kaolinites, and binary mixes at different proportions) were investigated. Their compacity (C) was determined following the water demand protocol with Vicat apparatus and compared to their consistency properties (liquidity and plasticity limits), and a correlation between these values is established. Different clay pastes prepared at different solid volume fractions were tested to define the influence of the clay nature on the paste consistency evolution. The results showed that clay nature for paste at high solid volume fraction does not influence constituency's evolution when their respectivecompacity is taking into account. It can be suggested that for a clay binder with a consistency close to C, which might be mandatory for poured earth application, only the swelling capacity might influence the mix design.


2022 ◽  
Vol 12 (1) ◽  
pp. 524
Author(s):  
Chao-Wei Tang ◽  
Chiu-Kuei Cheng ◽  
Lee-Woen Ean

The main purpose of this study was to investigate the mix design and performance of fiber-reinforced pervious concrete using lightweight coarse aggregates instead of ordinary coarse aggregates. There were two main stages in the relevant testing work. First, the properties of the matrix were tested with a rheological test and then different amounts of lightweight coarse aggregate and fine aggregate were added to the matrix to measure the properties of the obtained lightweight pervious concrete (LPC). In order to greatly reduce the experimental workload, the Taguchi experimental design method was adopted. An orthogonal array L9(34) was used, which was composed of four controllable three-level factors. There were four test parameters in this study, which were the lightweight coarse aggregate size, ordinary fine aggregate content, matrix type, and aggregate/binder ratio. The research results confirmed that the use of suitable materials and the optimal mix proportions were the key factors for improving the mechanical properties of the LPC. Due to the use of silica fume, ultrafine silica powder, and polypropylene fibers, the 28-day compressive strength, 28-day flexural strength, and 28-day split tensile strength of the LPC specimens prepared in this study were 4.80–7.78, 1.19–1.86, and 0.78–1.11 MPa, respectively. On the whole, the mechanical properties of the prepared LPC specimens were better than those of the LPC with general composition.


2022 ◽  
Vol 12 (1) ◽  
pp. 490
Author(s):  
Caroline Moura ◽  
Lucas Nascimento ◽  
Carlos Loureiro ◽  
Mafalda Rodrigues ◽  
Joel Oliveira ◽  
...  

Steel slag is a byproduct generated as waste during the steelmaking process and can be considered a cost-effective and environmentally acceptable alternative to replace natural aggregates. Using steel slag aggregates (SSA) to produce asphalt mixtures promotes sustainability and circular economy principles by using an industrial byproduct as a raw material. Thus, this work mainly aims to design more sustainable asphalt mixtures with high amounts of SSA that fit the circular economy expectations. This work developed two asphalt mixtures with SSA for surface (AC 14 surf) and binder/base (AC 20 bin/base) courses. Initially, the excellent wearing and polishing resistance of SSA and their good affinity with bitumen demonstrated the potential of this byproduct to be used in asphalt mixtures. Then, when analyzing the influence of using two different SSA incorporation rates (50% and a percentage close to 100%) in both asphalt mixtures, it was concluded that the use of SSA should be limited to 75% to avoid excessive air void contents and durability problems. The importance of considering the different particle densities of SSA and natural aggregates was highlighted during the mix design by defining a relationship between an effective and equivalent binder content. Finally, the mechanical performance of AC 14 and AC 20 with 75% SSA incorporation was compared to identical conventional mixtures produced with natural granite aggregates. The results obtained showed that the asphalt mixtures with 75% SSA have some workability problems due to the rough and porous surface of SSA. However, they present an excellent water sensitivity and permanent deformation resistance, surpassing the performance of the conventional asphalt mixtures.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 54
Author(s):  
Nicola Baldo ◽  
Matteo Miani ◽  
Fabio Rondinella ◽  
Jan Valentin ◽  
Pavla Vackcová ◽  
...  

This paper presents a study about a Machine Learning approach for modeling the stiffness of different high-modulus asphalt concretes (HMAC) prepared in the laboratory with harder paving grades or polymer-modified bitumen which were designed with or without reclaimed asphalt (RA) content. Notably, the mixtures considered in this study are not part of purposeful experimentation in support of modeling, but practical solutions developed in actual mix design processes. Since Machine Learning models require a careful definition of the network hyperparameters, a Bayesian optimization process was used to identify the neural topology, as well as the transfer function, optimal for the type of modeling needed. By employing different performance metrics, it was possible to compare the optimal models obtained by diversifying the type of inputs. Using variables related to the mix composition, namely bitumen content, air voids, maximum and average bulk density, along with a categorical variable that distinguishes the bitumen type and RAP percentages, successful predictions of the Stiffness have been obtained, with a determination coefficient (R2) value equal to 0.9909. Nevertheless, the use of additional input, namely the Marshall stability or quotient, allows the Stiffness prediction to be further improved, with R2 values equal to 0.9938 or 0.9922, respectively. However, the cost and time involved in the Marshall test may not justify such a slight prediction improvement.


2022 ◽  
Vol 2148 (1) ◽  
pp. 012055
Author(s):  
Qiuxiang Li ◽  
Jie Zheng ◽  
Mingfu Fu

Abstract Despite the common use of pervious concrete (PC), there is no standard way of producing the test specimens, which undergo testing to infer the behaviour of PC in the field. Vibrating table is the most common method but greatly reduced in vibration time compare with normal concrete in the laboratory. Marshall compaction and superpave gyratory compactor (SGC) are recommended standard molding methods for porous asphalt mixtures manufactured in the laboratory environment. Three kinds of pervious concrete samples with three target porosities were prepared by the above three methods, and the effects of the molding method on the physical properties, mechanical properties and durability of the samples were investigated in the study. Experimental results showed, with different molding methods adopting, pervious concrete with the same mixture design exhibits slightly different physical and mechanical properties. After analysis and comparison, SGC is the best choice to obtain concrete with high permeability, good freeze-thaw resistance and high strength, followed by Marshall compaction molding, and vibration molding is the last one. As a result, a win-win situation of the hydraulic characteristics and mechanical properties of pervious concrete can be achieved due to both optimized mix-design and appropriate molding method.


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