Special Issue "High-performance Construction Materials: Latest Advances and Prospects"

A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Building Materials, and Repair & Renovation".

Deadline for manuscript submissions: closed (1 June 2022) | Viewed by 8498

Special Issue Editors

Dr. Shengwen Tang
E-Mail Website
Guest Editor
School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430072, China
Interests: monitoring hydration and microstructure of cement-based materials using non-destructive measurement; investigation of transportation property of cement-based materials; microstructure and durability analysis of cementitious materials; fractal analysis of porous media; electrical property of cement-based materials
Special Issues, Collections and Topics in MDPI journals
Dr. Lei Wang
E-Mail Website
Guest Editor
College of Materials Science and Engineering, Xi’an University of Architecture and Technology, Xi’an, China
Interests: cement hydration; concrete workability; mechanical property; crack resistance; freezing and thawing; ions permeability; fiber-enhanced materials; Portland cement; low heat Portland cement; fly ash
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Our civilization has used construction materials extensively, especially for infrastructure projects. The importance of construction materials in enhancing the sustainable performance of structures and buildings goes without saying. Therefore, the continued development of more advanced construction materials with improved performance is of paramount importance.

Many innovations in high-performance construction materials have enabled the design and construction of sustainable and durable infrastructure. For instance, concrete is the most widely used building material in the world. To overcome the brittleness of concrete, fibers are used throughout the world for the development of fiber-reinforced cementitious composites with high ductility. In recent years, low heat Portland cement has been used to lower the cement hydration heat in attempts to reduce the thermal cracking risk. To improve the mechanical properties and microstructure of concrete, nanomaterials, such as silica fume, have been adopted.

This Special Issue “High-Performance Construction Materials: Latest Advances and Prospects”, aims to reflect the current state-of-the-art and new developments in all topics relevant to high-performance construction materials. We encourage all researchers working in areas of knowledge related to construction materials to submit details of their research. We hope this Special Issue will provide a comprehensive background for material engineers, researchers, and experts in the field. The topics to be considered in this Special Issue include, but are not limited to, the following:  

  • Fiber-reinforced cementitious composites
  • Self-healing cementitious materials
  • Innovative building materials
  • Low energy consuming building materials
  • Use of recycled materials, including recycled concrete
  • Use of waste materials and industrial byproducts in concrete
  • Use of nanoadditions in buildings
  • Durability studies
  • Mechanical properties
  • New trends in the design of sustainable engineering materials
  • New experimental techniques

Prof. Dr. Shengwen Tang
Prof. Dr. Lei Wang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Buildings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • construction materials
  • hydraulic buildings
  • durability
  • experimental techniques
  • microstructure
  • admixture

Published Papers (15 papers)

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Research

Article
Effect of Municipal Solid Waste Incineration Ash on Microstructure and Hydration Mechanism of Geopolymer Composites
Buildings 2022, 12(6), 723; https://doi.org/10.3390/buildings12060723 - 26 May 2022
Viewed by 335
Abstract
The geopolymerization process is an appropriate way of disposing of municipal solid waste incineration fly ash (MSWIFA), and possesses the advantages of immobilizing the heavy metals and making full use of its pozzolanic properties in manufacturing green, cementitious materials. In this study, coal [...] Read more.
The geopolymerization process is an appropriate way of disposing of municipal solid waste incineration fly ash (MSWIFA), and possesses the advantages of immobilizing the heavy metals and making full use of its pozzolanic properties in manufacturing green, cementitious materials. In this study, coal fly ash (FA) and metakaolin (MK) were used to prepare a geopolymer composite, with MK partially replaced by different proportions of MSWIFA through the alkali-activation method. The microstructure and hydration mechanism of the geopolymer composites containing MSWIFA were investigated through mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and Fourier transform-infrared spectroscopy (FT-IR) tests; and the immobilization effect of the geopolymer paste on heavy metal ions was explored through inductively coupled plasma-atomic emission spectrometry (ICP-AES). The MIP analysis showed that the addition of MFARR had an overall degrading effect on the pore structure of the matrix. When the content of MSWIFA reached the maximum of 35%, the porosity and average pore diameter increased by 25% and 16%, respectively, corresponding to the case without MSWIFA. However, the pore size distribution exhibited an improving trend when the MFARR was increased from 15% to 25%. The SEM images revealed that the integrity of the micromorphology of the geopolymer mortar became weaker after adding MSWIFA. When the MSWIFA content was increased to 35%, the microstructural compactness decreased and more pores and microcracks appeared in the matrix. The FT-IR pattern study suggested that all the geopolymer composites had a similar internal structure, consisting of O-H, C-O, Si-O-Si, and Si-O-Al. The main component of the geopolymer paste hydrated at 28 d remained dominated by calcium silica-aluminate (C-A-S-H), when the MSWIFA ranged from 0% to 35%. Finally, the ICP-AES results showed that the leaching concentrations of the geopolymer paste of J-40 at 28 d for Cd, Cr, Cu, Pb, and Zn met the requirements of Chinese standards. Full article
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Article
The Feasibility of Hydroxypropyl Methylcellulose as an Admixture for Porous Vegetarian Concrete Using Coarse Recycled Aggregates
Buildings 2022, 12(5), 676; https://doi.org/10.3390/buildings12050676 - 19 May 2022
Viewed by 366
Abstract
In this paper, hydroxypropyl methylcellulose (HPMC) is used as a new additive for porous vegetarian concrete (PVC) to improve its void structure and strength. The effect of the HPMC on the fluidity of the mortar was first investigated by a viscosity test. Then [...] Read more.
In this paper, hydroxypropyl methylcellulose (HPMC) is used as a new additive for porous vegetarian concrete (PVC) to improve its void structure and strength. The effect of the HPMC on the fluidity of the mortar was first investigated by a viscosity test. Then the cement hydration process was determined for analyzing the effect of the HPMC on the strength and durability of the hardened PVC. Subsequently, experiments to investigate the mass transport and compressive strength characteristics, as well as the vegetarian properties, of the concrete were carried out. The results show that the bonding forces between the recycled aggregates and packing layer are elevated by viscosity improvement. The viscocity and flowability are significantly related to the dosage of HPMC from 0.0‰ to 0.3‰. The harden time is also delayed while the content of HPMC increases.The segregation phenomenon caused by the recycled aggregate powder in porous concrete could also be relieved by adding HPMC. The durability of PVC in the wetting–drying cyclic test is significantly improved by incorporating HPMC. The results of the vegetarian test also prove that, with HPMC mixing, sufficient space would be created in porous concrete, which is more suitable for plant growth due to a large number of existing pore channels. Full article
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Article
Fracture Toughness of Reactive Powder Fibrous Concrete Composites under Pure and Mixed Modes (I/III)
Buildings 2022, 12(5), 599; https://doi.org/10.3390/buildings12050599 - 05 May 2022
Viewed by 354
Abstract
Reactive Powder Concretes (RPC) are well known for their exceptional strength properties and durability properties. The use of Supplementary Cementitious Materials (SCM) is the best way to enhance the strength and durability characteristics of RPCs further. Among various SCMs, the potential of Ground [...] Read more.
Reactive Powder Concretes (RPC) are well known for their exceptional strength properties and durability properties. The use of Supplementary Cementitious Materials (SCM) is the best way to enhance the strength and durability characteristics of RPCs further. Among various SCMs, the potential of Ground Granulated Blast-furnace Slag (GGBS) is proven by many researchers. However, the effect of GGBS on the fracture toughness of RPCs, especially under the tearing mode, is not explored. This study investigates the effect of partial replacement of OPC with GGBS in non-fibrous and fibrous RPCs, on its mode I (pure opening), mode III (pure tearing), and mixed-mode I/III fracture behaviour. A significant improvement in mode I, mode III, and mixed-mode I/III fracture toughness was observed due to incorporating GGBS and fibres in RPCs. The fibrous mix with 30% OPC, replaced with GGBS, exhibited the highest values of mode I and mode III fracture toughnesses, which were 2.35 MPa·m0.5 and 0.98 MPa·m0.5, respectively, and significantly high compared to the control non-fibrous and fibrous RPC mixes. The study reveals the ability of GGBS as an SCM to improve the fracture toughness of RPC mixes, thereby delaying the failure of the process of structural components. Full article
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Article
Response of Functionally Graded Preplaced Aggregate Fibrous Concrete with Superior Impact Strength
Buildings 2022, 12(5), 563; https://doi.org/10.3390/buildings12050563 - 27 Apr 2022
Cited by 1 | Viewed by 350
Abstract
This research examines the modified drop-mass impact performance on functionally graded preplaced aggregate fibrous concrete (FPAFC) against repeated low-velocity impacts. Three-layered FPAFCs were prepared with the outer layers reinforced with steel and polypropylene fibers to evaluate the impact resistance. For comparison, both one- [...] Read more.
This research examines the modified drop-mass impact performance on functionally graded preplaced aggregate fibrous concrete (FPAFC) against repeated low-velocity impacts. Three-layered FPAFCs were prepared with the outer layers reinforced with steel and polypropylene fibers to evaluate the impact resistance. For comparison, both one- and two-layered concretes were cast simultaneously. The modified version of the impact test was suggested to the ACI 544 drop-mass impact test to decrease the scattered test data. The modification was a replacement of the steel ball with a steel bar to apply a line impact instead of the single-point impact. This modification distributes the impact energy over a broader area and reduces the scattering of results. The study parameters for the tests were impact numbers, which cause first cracking and failure; ductility index; and mode of failure. In addition, three methods of the two-parameter Weibull distribution were used to examine the dispersed test results, which were presented in terms of reliability. Results revealed that the specimens comprising 3.6% steel fibers at the top layer and no fiber at the middle layer exhibited the highest percentage improvements of 633% and 2732% recorded for the cracking and failure impact number, respectively. The percentage difference in impact strength results between these two methods ranged from −14% to 75% for cracking impact number and from 6.8% to 57.2% for failure impact number. The coefficient of variation value calculated from the modified impact test was reduced and ranged from 20.3% to 56.1% for cracking impact number and from 15.2% to 65.3% for failure impact number, compared with the same mixtures from the ACI 544 test method. This phenomenon indicates that the modified impact test delivered a lower scattering of results by introducing a line of impact using a steel bar rather than a single-point impact. Full article
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Article
Application of Iron Ore Tailings and Phosphogypsum to Create Artificial Rockfills Used in Rock-Filled Concrete
Buildings 2022, 12(5), 555; https://doi.org/10.3390/buildings12050555 - 26 Apr 2022
Viewed by 446
Abstract
Rock-filled concrete (RFC) has good performance in terms of energy savings, cost reduction, and CO2 emissions as a novel massive concrete construction technology. There have been studies into replacing natural rocks in RFC with large blocks of solid waste, and this method [...] Read more.
Rock-filled concrete (RFC) has good performance in terms of energy savings, cost reduction, and CO2 emissions as a novel massive concrete construction technology. There have been studies into replacing natural rocks in RFC with large blocks of solid waste, and this method has been used on several construction sites. However, the granular and powdery solid waste utilized in RFC is limited, as a consequence of the special requirement of self-compacting concrete (SCC) in RFC. The goal of this paper is to increase the amount of granular and powdery solid waste in RFC. Iron ore tailing (IOT) and phosphogypsum (PG) were used separately as granular and powdery solid waste. The modified PG, ground blast-furnace slag (GBFS), steel slag, and cement clinker are combined to form parathion gypsum slag cement in a specific proportion, with the ratio of PG, GBFS, steel slag, and cement being 47:47:2:2. To replace the natural rocks in RFC, artificial rockfills made of IOT and parathion gypsum slag cement are used to increase the dosage of solid waste. The artificial rockfills were formed using three methods: compressing, roller compacting, and normal vibrating. When the compressive strength and material costs of the three types of artificial rockfills are compared, the compressing method is the best for maximizing the IOT. In artificial rockfills, the mass fraction of granular solid waste is 83.3%, and the mass fraction of total solid waste is 99.3%. Full article
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Article
Preparation of Magnesium Ammonium Phosphate Mortar by Manufactured Limestone Sand Using Compound Defoaming Agents for Improved Strength and Impermeability
Buildings 2022, 12(3), 267; https://doi.org/10.3390/buildings12030267 - 24 Feb 2022
Viewed by 563
Abstract
Magnesium ammonium phosphate cement (MAPC) mortar has recently risen up as high performance rapid repair material for concrete structures. But high costs of the raw materials limit its restoration and maintenance projects on a wide application range. This study proposes the use of [...] Read more.
Magnesium ammonium phosphate cement (MAPC) mortar has recently risen up as high performance rapid repair material for concrete structures. But high costs of the raw materials limit its restoration and maintenance projects on a wide application range. This study proposes the use of manufactured limestone sand with lower cost and wider range of sources in replacement of quartz sand as fine aggregates to produce MAPC mortar. However, the limestone fines of manufactured sand were initially found to have negative effects on the performance of MAPC mortar, causing significant blistering and volume expansion and decreased compressive strength and interfacial bonding strength. To minimize these negative effects, polyether modified silicone (PMS) defoamer and its compound use with mineral admixtures Portland cement and silica fume were investigated on the effectiveness in reducing expansion and improving other properties of MAPC mortar. Results showed that the compound use of PMS defoamer and Portland cement as a new defoaming formula effectively reduced the volume expansion from 7.92% to 0.91%. The compressive strength and interfacial bonding strength were significantly improved by over 34% and 60% respectively. Moreover, this defoaming formula showed improvements in water-tight performance and resistance to chloride penetration. According to the mercury intrusion porosimetry (MIP) analysis, the total porosity of MAPC mortar after defoaming treatment was decreased by about 40% and the pore structure was also modified to be finer by significantly reducing the harmful macropores. Overall, the use of manufactured limestone sands as fine aggregates turned out to be a feasible and economic approach for promoting the filed application of MAPC mortar. Full article
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Article
An Experimental Investigation on the Effects of Limestone Fines in Manufactured Sands on the Performance of Magnesia Ammonium Phosphate Mortar
Buildings 2022, 12(2), 249; https://doi.org/10.3390/buildings12020249 - 21 Feb 2022
Viewed by 349
Abstract
Magnesium ammonium phosphate cement (MAPC) prepared with ammonium dihydrogen phosphate (NH4H2PO4, ADP) and dead-burned Magnesium oxide (MgO) is a new type of rapid patch repair material for concrete structures. In order to reduce the material costs of [...] Read more.
Magnesium ammonium phosphate cement (MAPC) prepared with ammonium dihydrogen phosphate (NH4H2PO4, ADP) and dead-burned Magnesium oxide (MgO) is a new type of rapid patch repair material for concrete structures. In order to reduce the material costs of MAPC mortar, manufactured limestone sands, being a more widely-available resource with lower cost, was investigated in this study as an alternative to quartz sands for the preparation of MAPC mortar. The limestone fines in manufactured sands were found to be the key factor that influences properties of MAPC mortar by causing bubbling and volume expansion before hardening. As a result, the mechanical strength of MAPC mortar decreased with the increasing content of limestone fines due to increased porosity. According to microstructure analysis, the mechanism of these negative effects can be inferred as the reaction between limestone fines and ADP with the gas generation of CO2 and NH3. This reaction mainly occurred during a short period before setting while most limestone fines remained unreactive in the hardened MAPC mortar. Based on the above detailed experimental findings on the effects of limestone fines in manufactured sand on the properties of MAPC mortar, this paper pointed out that effective defoaming methods for inhibiting bubbling was the key to the utilization of manufactured sands in preparation of high performance MAPC mortar. Full article
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Article
Investigations on the Response of Novel Layered Geopolymer Fibrous Concrete to Drop Weight Impact
Buildings 2022, 12(2), 100; https://doi.org/10.3390/buildings12020100 - 21 Jan 2022
Cited by 5 | Viewed by 746
Abstract
In recent years, geopolymer concrete (GC) has become more popular in construction because of its multiple benefits, such as eco-friendliness, high temperature resistance and resistance to chemical attack in harsh environments. However, GC has limited deformation capability and tensile strength compared to ordinary [...] Read more.
In recent years, geopolymer concrete (GC) has become more popular in construction because of its multiple benefits, such as eco-friendliness, high temperature resistance and resistance to chemical attack in harsh environments. However, GC has limited deformation capability and tensile strength compared to ordinary concrete. Geopolymer fibrous concrete (GFC) exhibits high mechanical properties, such as compressive strength and impact strength. This study aimed to develop a novel composite comprising GFC at the tension zone and GC at the compression zone, and vice versa, are these composites were examined. The impact resistance of two-layered GC-GFC with various ratios (25–75, 50–50, 75–25%) was examined. In addition, a single layer specimen comprising GC and GFC was fabricated and tested as the reference specimen. Twenty-nine mixtures were developed and divided into four series. Four different types of fibre were used in this study; short polypropylene fibre, long polypropylene fibre, short steel fibre and long steel fibre. The ACI committee 544 drop weight test was used to evaluate the impact strength of specimens. Results indicated that the impact strength of GFC was significantly improved in long steel fibre-based specimens. In addition, two-layered specimens comprising different fibres—short polypropylene, long polypropylene, short steel and long steel—exhibited a positive influence on impact strength. Compared to a single-layer specimen, inferior impact strength was recorded in the two-layered specimen. Full article
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Article
Early-Age Performance of Graphene-Nanoplatelet-Modified High-Strength Concrete Cured by Electric Thermal Curing in Severe Cold Regions
Buildings 2022, 12(2), 86; https://doi.org/10.3390/buildings12020086 - 18 Jan 2022
Viewed by 438
Abstract
Concrete structure construction with a high strength grade in cold regions is a significant problem that has elicited considerable research attention. In this work, we firstly prepared steel-fiber-reinforced high-strength concrete (HSC) at −20 °C for winter concrete construction in a cold region. Specifically, [...] Read more.
Concrete structure construction with a high strength grade in cold regions is a significant problem that has elicited considerable research attention. In this work, we firstly prepared steel-fiber-reinforced high-strength concrete (HSC) at −20 °C for winter concrete construction in a cold region. Specifically, the combination of graphene nanoplatelet (GNP) incorporation and electric thermal (ET) curing could effectively improve the performance when preparing high-strength concrete (GNP-HSC) at −20 °C. The optimal amount of steel fiber added in this work was determined numerically and experimentally to be 2.5 vol%. The temperature development regularity of the ET-cured sample was also recorded during the whole curing process. Mechanical property results indicated that the combination of GNP incorporation and ET curing could effectively stimulate the strength formation of HSC samples to 91.2 MPa at early age, which is remarkable for concrete construction at −20 °C. Moreover, microstructural analyses (including XRD, TG and SEM analyses) were further conducted to verify the advantages of GNP incorporation and ET curing on the hydration products, hydration degree and microstructure of HSC samples. This work provides new insights into the application of GNP as a nanoscale material to improve the performance of HSC structures at extremely low temperatures. Full article
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Article
Effect of Silica Fume and Polyvinyl Alcohol Fiber on Mechanical Properties and Frost Resistance of Concrete
Buildings 2022, 12(1), 47; https://doi.org/10.3390/buildings12010047 - 05 Jan 2022
Cited by 2 | Viewed by 364
Abstract
To improve the mechanical properties and frost resistance of concrete, silica fume, and polyvinyl alcohol fiber compounded in concrete. The mechanical and frost resistance of concrete were comprehensively analyzed and evaluated for strength change, mass loss, and relative dynamic elastic modulus change by [...] Read more.
To improve the mechanical properties and frost resistance of concrete, silica fume, and polyvinyl alcohol fiber compounded in concrete. The mechanical and frost resistance of concrete were comprehensively analyzed and evaluated for strength change, mass loss, and relative dynamic elastic modulus change by compressive strength test, flexural strength test, and rapid freeze-thaw test. The results showed that with the incorporation of silica fume and polyvinyl alcohol fiber, the compressive and flexural strengths of concrete were improved, and the decrease in mass loss rate and relative dynamic elastic modulus of concrete after freeze-thaw cycles were significantly reduced, which indicated that the compounding of silica fume and polyvinyl alcohol fiber improved the frost resistance of concrete. When the content of silica fume was 10% and the volume content of polyvinyl alcohol fiber was 1%, the comprehensive mechanical performance and frost resistance of concrete is the best. The compressive strength increased by 26.6% and flexural strength increased by 29.17% compared to ordinary concrete. Based on the test data, to study the macroscopic damage evolution of concrete compound silica fume and polyvinyl alcohol fiber under repeated freeze-thaw conditions. The Weibull distribution probability model and GM (1, 1) model were established. The average relative errors between the predicted and actual data of the two models are small and very close. It is shown that both models can reflect well the development of concrete damage under a freeze-thaw environment. This provides an important reference value and theoretical basis for the durability evaluation and life prediction of compound silica fume and polyvinyl alcohol fiber concrete in cold regions. Full article
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Article
Influence of Waste Tire Particles on Freeze–Thaw Resistance and Impermeability Performance of Waste Tires/Sand-Based Autoclaved Aerated Concrete Composites
Buildings 2022, 12(1), 33; https://doi.org/10.3390/buildings12010033 - 01 Jan 2022
Cited by 3 | Viewed by 299
Abstract
Waste tires/sand-based autoclaved aerated concrete (SAAC) composites were prepared by mixing waste tires, which have different particle sizes and content. The physical performance, mechanical properties, freeze–thaw resistance, impermeability performance, phase composition, and microstructure of waste tires/sand-based autoclaved aerated concrete composite materials were examined. [...] Read more.
Waste tires/sand-based autoclaved aerated concrete (SAAC) composites were prepared by mixing waste tires, which have different particle sizes and content. The physical performance, mechanical properties, freeze–thaw resistance, impermeability performance, phase composition, and microstructure of waste tires/sand-based autoclaved aerated concrete composite materials were examined. The results demonstrated that the 750-μm-sized waste tire particles on the surface of the SAAC composite did not agglomerate. Moreover, these particles did not damage the pore structure of the composites. The SAAC composites, with a relatively high compressive strength and low mass-loss rate, were obtained when the contents of waste tire particles ranged from 1.0 to 2.5 wt.%. For composites prepared with 2.0 wt.% of 750-μm-sized waste tire particles, the optimal compressive and flexural strength values were 3.20 and 0.95 MPa, respectively. The increase in the rate of water absorption on SAAC composites was lowest (i.e., 16.3%) when the soaking time was from 24 to 120 h. Full article
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Article
Influence of Graphite Powder on the Mechanical and Acoustic Emission Characteristics of Concrete
Buildings 2022, 12(1), 18; https://doi.org/10.3390/buildings12010018 - 28 Dec 2021
Cited by 3 | Viewed by 375
Abstract
In this paper, uniaxial compressive strength (UCS) test and three-point bending (TPB) test, together with an acoustic emission (AE) system, were performed to investigate the mechanical properties and AE characteristic changes of concrete with different graphite powder (GP) content. The results show that: [...] Read more.
In this paper, uniaxial compressive strength (UCS) test and three-point bending (TPB) test, together with an acoustic emission (AE) system, were performed to investigate the mechanical properties and AE characteristic changes of concrete with different graphite powder (GP) content. The results show that: (1) Poor adhesion and low interlocking of graphite with cement stone increase the initial defects of concrete, reducing its elastic modulus and the cyclo-hoop effect, and thus weakening the compressive strength. (2) For concrete with a low graphite content, the second sharp rise in ringing counts or energy released during the compressive process can be regarded as a failure alarm. However, as GP content increases, the second sharp rise fades away, while the first sharp rise becomes more visible. At high GP content, the first sharp rise is better for predicting failure. (3) The initial defects caused by GP significantly lower the initial fracture toughness, but its bridging effect greatly increases the critical crack mouth opening displacement and thus significantly enhances the unstable fracture toughness of concrete, by up to 9.9% at 9% GP content. (4) In contrast to compressive process, the sharp increase in AE signals preceding failure during the fracture process cannot be used to predict failure because it occurs too close to the ultimate load. However, as GP can significantly increase the AE signals and damage value in the stable period, such failure precursor information can provide a safety warning for damage development. Full article
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Article
Effect of Needle Type, Number of Layers on FPAFC Composite against Low-Velocity Projectile Impact
Buildings 2021, 11(12), 668; https://doi.org/10.3390/buildings11120668 - 20 Dec 2021
Cited by 6 | Viewed by 962
Abstract
Protective structures subjected to intensive loads that may benefit from the use of multilayer composite structures with excellent hardness and impact resistance represent an emerging research field in recent times. In this study, low-velocity projectile impact tests were performed on Functionally-graded Preplaced Aggregate [...] Read more.
Protective structures subjected to intensive loads that may benefit from the use of multilayer composite structures with excellent hardness and impact resistance represent an emerging research field in recent times. In this study, low-velocity projectile impact tests were performed on Functionally-graded Preplaced Aggregate Fibrous Concrete (FPAFC) mixtures to evaluate their performance. The effects of projectile needle type, fibre type and hybridization in addition to the number of layers in the composites on projectile impact were investigated. The bioinspiration of the excellent impact strength of turtle shells was used to design an FPAFC comprising a higher amount of steel and polypropylene fibres at the outer layers. In parallel, one and two-layered concretes were also cast to assess the effectiveness of three-layered FPAFC. The tests were performed on disc specimens using non-deformable compound bevel, convex edge and hollow edge projectiles. The damage severity was quantified by the top damage area, bottom damage area and depth of penetration. In addition, a simple analytical model for predicting the composite mass expulsion was developed and implemented. Findings indicated that regardless of fiber type and distribution, the compound bevel projectile needle produced the lowest impact numbers for all single, double and triple-layer specimens compared to the convex edge and hollow edge projectiles. Repeated projectile impacts increased the penetration depth and damaged area at the top and bottom surfaces of all targets. Targets were more resistant to convex edge and hollow edge projectile penetration than the compound bevel. The experimental and analytical model results for mass expelled from the top surface are reasonably acceptable. This research gives an idea of developing advanced fibrous composite with superior impact resistance for the promising protective structures. Full article
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Article
Preparation and Properties Study of Cementitious Grouts Containing Crumb Rubber
Buildings 2021, 11(11), 555; https://doi.org/10.3390/buildings11110555 - 18 Nov 2021
Cited by 1 | Viewed by 433
Abstract
This article aims to improve the toughness of pre-packaged grouts (PPG) by incorporating crumb rubber. The mechanism for toughness of PPG with crumb rubber was analyzed based on the uniaxial compression model. Crumb rubber with surfaces treated by different methods (NaOH solutions or [...] Read more.
This article aims to improve the toughness of pre-packaged grouts (PPG) by incorporating crumb rubber. The mechanism for toughness of PPG with crumb rubber was analyzed based on the uniaxial compression model. Crumb rubber with surfaces treated by different methods (NaOH solutions or microwave treatment) was observed by scanning electron microscopy (SEM). The effects of mesh sizes, amounts, surface-treated methods of crumb rubber, and mixing procedures on the PPG’s mechanical strength and rheological properties were investigated. The results showed that, firstly, the addition of crumb rubber improves the PPG’s toughness, while its mechanical strength is reduced. Adding NaOH solutions or microwave-treated crumb rubber into PPG can weaken the negative effects of crumb rubber on the PPG’s mechanical strength; however, this function is limited. Secondly, the crumb rubber grouts’ rheological properties can be fully exploited by increasing the stirring rate and time so that the fluidity of crumb rubber grouts is improved, which fulfils the characteristics of no bleeding and micro-expansion. Finally, the optimal formula and mixing technique of crumb rubber grouts were proposed in this paper.The results of this paper can provide a significant reference for the application of scrap tires. Full article
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Article
The Effect of Sand Type on the Rheological Properties of Self-Compacting Mortar
Buildings 2021, 11(10), 441; https://doi.org/10.3390/buildings11100441 - 28 Sep 2021
Cited by 1 | Viewed by 555
Abstract
In order to understand the effect of sand type on the rheological properties of self-compacting mortar, four varieties of sand, namely, quartz sand (QS), river sand (RS), and two kinds of manufactured sand, marked as MS-A and MS-B, were studied. As part of [...] Read more.
In order to understand the effect of sand type on the rheological properties of self-compacting mortar, four varieties of sand, namely, quartz sand (QS), river sand (RS), and two kinds of manufactured sand, marked as MS-A and MS-B, were studied. As part of this study, the sands’ particle shape parameters, such as their length:width ratio and roundness, were determined. Mortars containing the four varieties of sand were tested using the slump flow test and the V-funnel test in oven-dried (OD) and saturated surface-dried (SSD) conditions in order to identify the water absorption, shape-related differences, and specific gravity in their rheological performance. The changing trends of the slump flows and the V-funnel times of the different mortars in OD and SSD were similar. By eliminating the influence of water absorption on mortar rheology, shape–weight parameters, such as the ratio between the length:width ratio and specific gravity (LWS) and the product of roundness and specific gravity (ROS), were defined in order to quantify the compound effects of sand type on mortar rheology. The regression analysis showed an excellent linear correlation between slump flow and both LWS and ROS, and a very good linear correlation was also demonstrated between the V-funnel time and both LWS and ROS. Based on the particle shape–weight parameters, the rheological properties of mortars can be predicted. Based on the mortar rheological threshold theory, the self-compacting mortar (SCM) zone can be drawn. The predicted SCM zone overlaps considerably with the experimental SCM zone for MS-A. Full article
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