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Open AccessEditor’s ChoiceArticle

Properties of Self-Compacting Concrete Produced with Optimized Volumes of Calcined Clay and Rice Husk Ash—Emphasis on Rheology, Flowability Retention and Durability

by

Abubakar Muhammad

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Karl-Christian Thienel

Materials 2023, 16(16), 5513; https://doi.org/10.3390/ma16165513 - 08 Aug 2023

Viewed by 354

Abstract

The durability of concrete requires a dense microstructure which can be achieved by using self-compacting concrete (SCC). Both calcined clay (CC) and rice husk ash (RHA) are promising supplementary cementitious materials (SCMs) that can partially replace cement, but their use in SCC is [...] Read more.

The durability of concrete requires a dense microstructure which can be achieved by using self-compacting concrete (SCC). Both calcined clay (CC) and rice husk ash (RHA) are promising supplementary cementitious materials (SCMs) that can partially replace cement, but their use in SCC is critical due to their higher water demand (WD) and specific surface area (SSA) compared to cement. The effect of partial substitution of cement at 20 vol-% with binary and ternary blends of CC and RHA on flowability retention and durability of SCC was investigated. The empirical method of SCC design was adopted considering the physical properties of both CC and RHA. The deformability of the SCC was evaluated using the slump flow and J-ring tests. The T₅₀₀ time and the V-funnel test were used to assess the viscosity of the SCC. The flowability retention was monitored by the plunger method, and flow resistance was determined based on the rheological measurements of SCC. The evolution of the hydrate phases of the binder in SCC was determined by thermogravimetric analysis, while the durability was evaluated by a rapid chloride migration test. Cement partial replacement with 20 vol-% CC has no significant effect on fresh SCC, flowability retention, compressive strength and durability properties. On the other hand, 20 vol-% RHA requires a higher dosage of SP to achieve self-compactability and increase the viscosity of SCC. Its flowability retention is only up to 30 min after mixing and exhibited higher flow resistance. It consumes more calcium hydroxide (CH) and improves the compressive strength and chloride resistance of SCC. The ternary blending with CC and RHA yielded better fresh SCC properties compared to the binary blend with RHA, while an improved chloride penetration resistance could be achieved compared to the binary CC blend. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Early-Age Cracking Behavior of Concrete Slabs with GFRP Reinforcement

by

Hossein Roghani

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Antonio Nanni

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John E. Bolander

Materials 2023, 16(15), 5489; https://doi.org/10.3390/ma16155489 - 06 Aug 2023

Viewed by 402

Abstract

This paper reports on a combined experimental and numerical modeling investigation of cracking of concrete slabs with GFRP reinforcement. At this stage of the project, attention is given to early-age cracking driven by plastic shrinkage, preceding longer term considerations of cracking resistance over [...] Read more.

This paper reports on a combined experimental and numerical modeling investigation of cracking of concrete slabs with GFRP reinforcement. At this stage of the project, attention is given to early-age cracking driven by plastic shrinkage, preceding longer term considerations of cracking resistance over the service life of field applications. Of interest is the effectiveness of GFRP reinforcement in restricting plastic shrinkage cracking. Nine small-scale slab specimens were subjected to controlled evaporation rates. Images of crack development were acquired periodically, from which crack width estimations were made. Comparisons were made between slabs reinforced with conventional steel and those reinforced with GFRP, along with control specimens lacking reinforcement. During the period of plastic shrinkage, the time of crack initiation and subsequent crack openings do not appear to be influenced by the presence of the reinforcing bars. To understand this behavior, six early-age bond tests were conducted for both types of the bars after 1, 2, and 3 h exposure to the controlled evaporation rate. In addition, concrete strength development and time of settings were measured using penetration resistance tests on a representative mortar. The numerical modeling component of this research is based on a Voronoi cell lattice model; in this approach, the relative humidity, temperature, and displacement fields are discretized in three-dimensions, allowing for a comprehensive investigation of material behavior within the controlled environment. Based on the measured bond properties, our simulations confirm that the reinforcing bars restrict crack development, though they do not prevent it entirely. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Calculation Method for the Cracking Resistance and Bearing Performance of SFRAC Beams

by

Qian Zhu

and

Jie Liu

Materials 2023, 16(13), 4769; https://doi.org/10.3390/ma16134769 - 01 Jul 2023

Viewed by 364

Abstract

The utilization of recycled aggregate (RCA) in preparing recycled concrete (RAC) is an effective measure to solve the increase in construction waste. Furthermore, applying RAC to flexural members is a viable practice. The addition of steel fiber to RAC to prepare steel fiber [...] Read more.

The utilization of recycled aggregate (RCA) in preparing recycled concrete (RAC) is an effective measure to solve the increase in construction waste. Furthermore, applying RAC to flexural members is a viable practice. The addition of steel fiber to RAC to prepare steel fiber recycled concrete (SFRAC) solves the performance deterioration caused by the recycled aggregate, so it is necessary to study the effects of the recycled aggregate replacement rate and fiber–volume ratio on the crack resistance and bending performance of SFRAC beams. In this study, 13 beams were designed and manufactured, with the water–cement ratio, recycled aggregate replacement rate, and fiber–volume ratio as the primary variables, and the cracking moment and ultimate moment of the SFRAC beams were systematically studied. The results show that the cracking and ultimate moments of the SFRAC beams increased with decreases in the water–cement ratio or with increases in the fiber–volume ratio and were unaffected by the replacement rate of recycled aggregates. Based on the experimental results and theoretical analysis, a calculation model and formula for the cracking moment were established. The ultimate bearing capacity of SFRAC beams can be accurately determined using the ACI 318 and ACI 544 standards. The research results serve as a valuable reference for the design of SFRAC beams, effectively address the issue of performance degradation in RAC structural members, and promote the use of green building materials. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Investigation of Water Absorption Behavior of Recycled Aggregates and its Effect on Concrete Strength

by

Yangfei Ding

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Anming She

and

Wu Yao

Materials 2023, 16(13), 4505; https://doi.org/10.3390/ma16134505 - 21 Jun 2023

Viewed by 324

Abstract

The water–cement ratio (w/c) has a significant effect on the strength of recycled concrete. In this study, considering the effects of water/cement ratio, strength, and water content of recycled aggregates, two kinds of pulse sequences of low-field nuclear magnetic resonance (LF-NMR) were applied [...] Read more.

The water–cement ratio (w/c) has a significant effect on the strength of recycled concrete. In this study, considering the effects of water/cement ratio, strength, and water content of recycled aggregates, two kinds of pulse sequences of low-field nuclear magnetic resonance (LF-NMR) were applied to investigate the water migration behavior between simulated recycled aggregates (SRA) and water or fresh mortar. Three sets of concrete strength tests were designed and the results were used to verify the findings of LF-NMR imaging tests. The results showed that the depth of water migration in the SRA increases with time: at first the change rate is rapid, then slows down, and eventually tends to remain stable. When the SRA is in contact with fresh mortar with low w/c, no water migration occurs because the hydration of the cement in the mixture consumes a large amount of water, resulting in the inability of water to migrate into the SRA through capillary pressure. For the recycled aggregate concrete with high strength, the addition of extra water will increase the effective w/c and reduce the compressive strength of the concrete. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Investigation of Workability and Mechanical Properties of PVA Fiber-Reinforced Phosphogypsum-Based Composite Materials

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Materials 2023, 16(12), 4244; https://doi.org/10.3390/ma16124244 - 08 Jun 2023

Viewed by 466

Abstract

To address the poor characteristics of low strength and poor toughness in phosphogypsum-based construction material, this study investigates the influence of different diameters, lengths, and dosages of polyvinyl alcohol (abbreviated as PVA) fibers on the workability and mechanical properties of phosphogypsum-based construction material. [...] Read more.

To address the poor characteristics of low strength and poor toughness in phosphogypsum-based construction material, this study investigates the influence of different diameters, lengths, and dosages of polyvinyl alcohol (abbreviated as PVA) fibers on the workability and mechanical properties of phosphogypsum-based construction material. The results show that as the length and dosage of PVA fibers increase, the flowability of the slurry gradually decreases, and the setting time also shortens. With an increase in the diameter of PVA fibers, the rate of decrease in flowability slows down, and the rate of shortening of setting time also gradually slows down. Moreover, the inclusion of PVA fibers significantly improves the mechanical strength of the specimens. When PVA fibers with a diameter of 15 μm, length of 12 mm, and dosage of 1.6% are used, the phosphogypsum-based construction material reinforced with PVA fibers exhibits optimal performance. Under this mixing ratio, the strength values of the specimens for flexural strength, bending strength, compressive strength, and tensile strength are 10.07 MPa, 10.73 MPa, 13.25 MPa, and 2.89 MPa, respectively. Compared to the control group, the strength enhancements are 273.00%, 164.29%, 15.32%, and 99.31%, respectively. SEM scanning of the microstructure provides a preliminary explanation for the mechanism of how PVA fibers affect the workability and mechanical properties of phosphogypsum-based construction material. The findings of this study can provide a reference for the research and application of fiber-reinforced phosphogypsum-based construction material. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Flexural Strength Characteristics of Fiber-Reinforced Cemented Soil

by

Gabriel Orquizas Mattielo Pedroso

,

Ricardo Domingos dos Santos Junior

,

Jefferson Lins da Silva

,

Mariana Ferreira Benessiuti Motta

and

Emerson Felipe Félix

Materials 2023, 16(11), 4185; https://doi.org/10.3390/ma16114185 - 04 Jun 2023

Cited by 1 | Viewed by 862

Abstract

This work deals with the flexural performance of a soil-cement for pavement reinforced by polypropylene and steel fibers, and the main purpose is to evaluate the effect of different curing times. In this sense, three different curing times were employed to investigate the [...] Read more.

This work deals with the flexural performance of a soil-cement for pavement reinforced by polypropylene and steel fibers, and the main purpose is to evaluate the effect of different curing times. In this sense, three different curing times were employed to investigate the influence of fibers on the material’s behavior at varying levels of strength and stiffness as the matrix became increasingly rigid. An experimental program was developed to analyze the effects of incorporating different fibers in a cemented matrix for pavement applications. Polypropylene and steel fibers were used at 0.5/1.0/1.5% fractions by volume for three different curing times (3/7/28 days) to assess the fiber effect in the cemented soil (CS) matrices throughout time. An evaluation of the material performance was carried out using the 4-Point Flexural Test. The results show that steel fibers with 1.0% content improved by approximately 20% in terms of initial strength and peak strength at small deflections without interfering the flexural static modulus of the material. The polypropylene fiber mixtures had better performance in terms of ductility index reaching values varying from 50 to 120, an increase of approximately 40% in residual strength, and improved cracking control at large deflections. The current study shows that fibers significantly affect the mechanical performance of CSF. Thus, the overall performance presented in this study is useful for selecting the most suitable fiber type corresponding to the different mechanisms as a function of curing time. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Axial Compressive Behavior of Cross-Shaped CFST Stub Columns with Steel Bar Truss Stiffening

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Materials 2023, 16(11), 4147; https://doi.org/10.3390/ma16114147 - 02 Jun 2023

Viewed by 462

Abstract

Concrete-filled steel tube (CFST) columns have been widely used in residential buildings due to their high bearing capacity, good ductility, and reliable seismic performance. However, conventional circular, square, or rectangular CFST columns may protrude from the adjacent walls, resulting in inconvenience in terms [...] Read more.

Concrete-filled steel tube (CFST) columns have been widely used in residential buildings due to their high bearing capacity, good ductility, and reliable seismic performance. However, conventional circular, square, or rectangular CFST columns may protrude from the adjacent walls, resulting in inconvenience in terms of the arrangement of furniture in a room. In order to solve the problem, special-shaped CFST columns, such as cross-shaped, L-shaped, and T-shaped columns, have been suggested and adopted in engineering practice. These special-shaped CFST columns have limbs with the same width as the adjacent walls. However, compared with conventional CFST columns, the special-shaped steel tube provides weaker confinement to the infilled concrete under axial compressive load, especially at concave corners. The parting at concave corners is the key factor affecting the bearing capacity and ductility of the members. Therefore, a cross-shaped CFST column with steel bar truss stiffening is suggested. In this paper, 12 cross-shaped CFST stub columns were designed and tested under axial compression loading. The effects of steel bar truss node spacing and column–steel ratio on the failure mode, bearing capacity, and ductility were discussed in detail. The results indicate that the columns with steel bar truss stiffening can change the final deformation mode of the steel plate from single-wave buckling to multiple-wave buckling, and the failure modes of columns also subsequently change from single-section concrete crushing failure to multiple-section concrete crushing failure. The steel bar truss stiffening shows no obvious effect on the axial bearing capacity of the member but significantly improves the ductility. The columns with a steel bar truss node spacing of 140 mm can only increase the bearing capacity by 6.8% while nearly doubling the ductility coefficient from 2.31 to 4.40. The experimental results are compared with those of six design codes worldwide. The results show that the Eurocode 4 (2004) and the Chinese code CECS159-2018 can be safely used to predict the axial bearing capacity of cross-shaped CFST stub columns with steel bar truss stiffening. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Study on Shrinkage in Alkali-Activated Slag–Fly Ash Cementitious Materials

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Materials 2023, 16(11), 3958; https://doi.org/10.3390/ma16113958 - 25 May 2023

Cited by 2 | Viewed by 711

Abstract

Traditional silicate cement materials produce a large amount of CO₂ during production, making it urgent to seek alternatives. Alkali-activated slag cement is a good substitute, as its production process has low carbon emissions and energy consumption, and it can comprehensively utilize various [...] Read more.

Traditional silicate cement materials produce a large amount of CO₂ during production, making it urgent to seek alternatives. Alkali-activated slag cement is a good substitute, as its production process has low carbon emissions and energy consumption, and it can comprehensively utilize various types of industrial waste residue while possessing superior physical and chemical properties. However, the shrinkage of alkali-activated concrete can be larger than that of traditional silicate concrete. To address this issue, the present study utilized slag powder as the raw material, sodium silicate (water glass) as the alkaline activator, and incorporated fly ash and fine sand to study the dry shrinkage and autogenous shrinkage values of alkali cementitious material under different content. Furthermore, combined with the change trend of pore structure, the impact of their content on the drying shrinkage and autogenous shrinkage of alkali-activated slag cement was discussed. Based on the author’s previous research, it was found that by sacrificing a certain mechanical strength, adding fly ash and fine sand can effectively reduce the drying shrinkage and autogenous shrinkage values of alkali-activated slag cement. The higher the content, the greater the strength loss of the material and the lower the shrinkage value. When the fly ash content was 60%, the drying shrinkage and autogenous shrinkage of the alkali-activated slag cement mortar specimens decreased by about 30% and 24%, respectively. When the fine sand content was 40%, the drying shrinkage and autogenous shrinkage of the alkali-activated slag cement mortar specimens decreased by about 14% and 4%, respectively. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

High Performance Concretes with Highly Reactive Rice Husk Ash and Silica Fume

by

Andres Salas Montoya

,

Chul-Woo Chung

and

Ji-Hyun Kim

Materials 2023, 16(11), 3903; https://doi.org/10.3390/ma16113903 - 23 May 2023

Cited by 3 | Viewed by 771

Abstract

The search for new sources of high-quality non-crystalline silica as a construction material for high-performance concrete has attracted the interest of researchers for several decades. Numerous investigations have shown that highly reactive silica can be produced from rice husk, an agricultural waste that [...] Read more.

The search for new sources of high-quality non-crystalline silica as a construction material for high-performance concrete has attracted the interest of researchers for several decades. Numerous investigations have shown that highly reactive silica can be produced from rice husk, an agricultural waste that is abundantly available in the world. Among others, the production of rice husk ash (RHA) by chemical washing with hydrochloric acid prior to the controlled combustion process has been reported to provide higher reactivity because such a process removes alkali metal impurities from RHA and provides an amorphous structure with higher surface area. This paper presents an experimental work in which a highly reactive rice husk ash (TRHA) is prepared and evaluated as a replacement for Portland cement in high-performance concretes. The performance of RHA and TRHA was compared with that of conventional silica fume (SF). Experimental results showed that the increase in compressive strength of concrete with TRHA was clearly observed at all ages, generally higher than 20% of the strength obtained with the control concrete. The increase in flexural strength was even more significant, showing that concrete with RHA, TRHA and SF increased by 20%, 46%, and 36%, respectively. Some synergistic effect was observed when polyethylene–polypropylene fiber was used for concrete with TRHA and SF. The chloride ion penetration results also indicated that the use of TRHA had similar performance compared to that of SF. Based on the results of statistical analysis, the performance of TRHA is found to be identical to that of SF. The use of TRHA should be further promoted considering the economic and environmental impact that will be achieved by utilizing agricultural waste. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Study on Kinetics of Carbonization Reaction of Hardened Cement Paste Powder Based on Carbonization Degree

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Materials 2023, 16(7), 2584; https://doi.org/10.3390/ma16072584 - 24 Mar 2023

Viewed by 621

Abstract

The hardened cement paste powder (HCP) powder, devoid of the hydration cementing property, can be regenerated and cemented into a test block with practical strength of almost 60 MPa via CO₂ carbonization using appropriate means. This study established a kinetic model of [...] Read more.

The hardened cement paste powder (HCP) powder, devoid of the hydration cementing property, can be regenerated and cemented into a test block with practical strength of almost 60 MPa via CO₂ carbonization using appropriate means. This study established a kinetic model of CO₂ curing of an HCP powder test block based on the degree of carbonization to study the carbonization reaction kinetic characteristics of the test block. The model was modified according to the characteristics of the evident temperature differences in the reaction kettle in the early, middle, and late stages of the carbonization process. The proposed model can be used to formulate and control the carbonization and cementation processes of HCP powder and can also be applied to describe the kinetics of the reaction processes of other similar systems. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessArticle

Influence of Mixing Water Content and Curing Time on Bond Strength of Clinker Masonry: The Wrench Test Method

by

Jan Kubica

and

Iwona Galman

Materials 2023, 16(6), 2171; https://doi.org/10.3390/ma16062171 - 08 Mar 2023

Viewed by 852

Abstract

In the present study, experimental investigations on the influence of mixing water content used for the preparation of mortar mix using factory-made dry-mix mortar dedicated to bricklaying with clinker masonry units are presented, as well as the curing time on flexural bond strength [...] Read more.

In the present study, experimental investigations on the influence of mixing water content used for the preparation of mortar mix using factory-made dry-mix mortar dedicated to bricklaying with clinker masonry units are presented, as well as the curing time on flexural bond strength of masonry made of these two materials. The flexural bond strength was tested using the “wrench test” method. The masonry tests specimens were prepared using three volumes of mixing water as follows: 4.0 L (the value recommended by the mortar manufacturer); 4.5 L; and 5 L of tap water per one 25 kg bag of dry pre-mixed mortar. The influence of the mixing water content was analyzed in relation to curing time. All masonry specimens were tested in four series after 9, 14, 21, and 28 days of sample curing. The results showed that the use of 6 and 18% more mixing water than recommended by the manufacturer (4.5 and 5 L per bag) adversely affected flexural bond strength. Moreover, for all three mixing water amounts, it was found that the maximum values of bonding strength were reached after 9 days of curing, which decreased over time. The largest decreases (30–40%) were recorded after 14 days. After 21 days, these values continued to decrease, but more slowly. The final value of the ratio of bond strength to flexural strength of the mortar was similar for all amounts of mixing water and for the 28-day curing time, it oscillated around 0.2. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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Open AccessReview

Recent Advances in Properties and Applications of Carbon Fiber-Reinforced Smart Cement-Based Composites

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Materials 2023, 16(7), 2552; https://doi.org/10.3390/ma16072552 - 23 Mar 2023

Cited by 2 | Viewed by 1460

Abstract

Under the strategies of low-carbon and environmental protection, promoting green technology innovation to achieve carbon neutrality in the construction field has become a universal goal. As the building material with the highest consumption, concrete has gradually begun to transform into a multi-functional and [...] Read more.

Under the strategies of low-carbon and environmental protection, promoting green technology innovation to achieve carbon neutrality in the construction field has become a universal goal. As the building material with the highest consumption, concrete has gradually begun to transform into a multi-functional and intelligent product. Therefore, the research on carbon fiber-reinforced cement-based composites (CFRCs) is of relative interest. It mainly uses carbon fibers (CFs) with high elasticity, strength, and conductivity to disperse evenly into the concrete as a functional filler, to achieve the intelligent integration of concrete structures and function innovatively. Furthermore, the electrical conductivity of CFRC is not only related to the content of CFs and environmental factors but also largely depends on the uniform dispersion and the interfacial bonding strength of CFs in cement paste. This work systematically presents a review of the current research status of the enhancement and modification mechanism of CFRC and the evaluation methods of CF dispersion. Moreover, it further discusses the improvement effects of different strengthening mechanisms on the mechanical properties, durability, and smart properties (thermoelectric effect, electrothermal effect, strain-sensitive effect) of CFRC, as well as the application feasibility of CFRC in structural real-time health monitoring, thermal energy harvesting, intelligent deformation adjustment, and other fields. Furthermore, this paper summarizes the problems and challenges faced in the efficient and large-scale applications of CFRCs in civil engineering structures, and accordingly promotes some proposals for future research. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Construction and Building Materials)

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