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Article

Study on Mechanical Properties and Mechanism of Recycled Brick Powder UHPC

by
Chengfang Yuan
1,2,
Weicheng Fu
2,*,
Ali Raza
2 and
Haofei Li
2
1
Yellow River Laboratory, Zhengzhou University, Zhengzhou 450001, China
2
College of Water Resources and Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
*
Author to whom correspondence should be addressed.
Buildings 2022, 12(10), 1622; https://doi.org/10.3390/buildings12101622
Submission received: 16 September 2022 / Revised: 1 October 2022 / Accepted: 3 October 2022 / Published: 6 October 2022
(This article belongs to the Section Building Materials, and Repair & Renovation)
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Versions Notes

Abstract

:
Recycled brick powder (RBP) is a kind of solid waste material with pozzolanic activity, which can partially replace cement as a cementitious material to prepare concrete. In this paper, ultra-high-performance concrete (UHPC) was prepared by RBP. The effects of different RBP contents as a mineral admixture on the mechanical properties and microstructure of UHPC were studied by experiments. The results show that RBP has a certain weakening effect on the compressive strength development of UHPC. The compressive strength of UHPC decreases with the increase in the replacement rate of RBP, but the 28 d compressive strength of each group of specimens is not less than 140 MPa. The flexural toughness and tensile strain of RBP UHPC increased first and then decreased with the increase in brick powder replacement rate and reached the maximum at 40% and 30%, respectively. The material exhibits good strain-hardening characteristics. In addition, the incorporation of RBP can improve the bond strength between steel fiber and matrix and the ultimate bond strength reaches the maximum when the substitution rate is 40%. From the perspective of nano-scale characteristics, the RBP not only fills the pores as micro-aggregate, but also participates in the secondary hydration reaction to further optimize the pore structure of UHPC.

1. Introduction

In China, with the further development of urbanization, the amount of urban construction waste is increasing year by year. A billion tons of construction and demolition (C&D) waste is generated annually in China, reported to about 1.8 billion tons in 2017 [1] and has kept growing every year. A large amount of unused construction waste is often dumped or landfilled, which not only occupies land resources, but also pollutes the environment [2,3,4,5]. The waste bricks are one such waste, which, when broken, produce powder particles with particle sizes less than 75 μm. It has certain activity and can be activated by physical or chemical methods. The activated brick powder particles can be added to concrete as auxiliary cementitious materials [6,7]. This provides a new idea for recycling construction waste.
UHPC (ultra-high-performance concrete) generally has higher cement and silica fume (SF) content and lower water/binder ratio, and cement-based material with compressive strength above 100 MPa is classified as UHPC [8]. UHPC has been widely used in construction of bridges, nuclear power plants, municipal and marine fields due to its excellent mechanical properties and durability [9,10,11,12,13]. However, UHPC has the problems of low water–binder ratio (generally 0.16–0.20), large amount of cementitious materials and high cost, which to some extent, affects the further promotion and application of these materials [14]. Some scholars [15] found that the hydration degree of cement in UHPC mixture was low (only 30–40%). Some of these unhydrated cement particles only have a filling effect and some will be wrapped in the surface of Ca(OH)2 generated by cement hydration reaction, which hinders the pozzolanic reaction inside UHPC. In order to reduce the amount of cement and improve its utilization rate, it is effective to look for alternatives to cement with similar chemical composition and morphology. Based on the available literature, replacement of cement with sustainable supplementary cementitious materials (SCMs) reduces the content of cement without markedly sacrificing the mechanical properties of concrete [16,17,18]. It has been proved that replacing cement with SCMs in relatively large volumes can not only reduce costs, but also improve long-term strength and the corrosion resistance of UHPC. Ding et al. [19] used limestone powder with similar particle size to replace cement to prepare low-cement UHPC. The results showed that when the cement content was reduced to 280 kg/m3, the volume stability of UHPC was positively affected and the mechanical properties of the material did not decrease. Yalçınkaya [20] used slag powder to replace cement to prepare UHPC and found that the addition of slag powder reduced the hydration heat and early strength, thereby extending the curing time. When the substitution rate reached 60%, the hydration heat of UHPC could be reduced by 28–36%, the 28 d compressive strength was maintained at 160 MPa and the flexural strength was 45 MPa. Similarly, Ma et al. reported that the greater the fineness of recycled brick powder, the higher the pozzolanic activity and it can form a dense microstructure in concrete or mortar [21]. Zhao et al. [22,23] studied the pozzolanic activity of RBP and found that with the increase in grinding time, the particle size of RBP was refined and spherical, which could increase its specific surface area and pozzolanic activity. The decrease in particle size of RBP can accelerate the early hydration reaction and shorten the setting time. The decrease in CBP particle size in blended cement paste can accelerate the early-age hydration and decrease the setting time since the ultrafine RBP could become the crystallization nucleus. Lin [24] and Xue [25] studied the 28 d compressive strength of RBP cement-based materials with different substitution rates. It was found that regardless of the substitution rate, the partial substitution of RBP for cement will lead to a decrease in compressive strength. Meanwhile, by replacing 20% cement with recycled brick powder, Gonçalves et al. [26] found that it can meet the strength requirements and it may be caused by the decrease in the proportion of macropores with the addition of RBP. However, the strength decreases with the increase in replacement rate, also recorded by the scholars. Xiao et al. [27] stated that the mineral composition of RBP approximated fly ash, thereby substituting RBP for cement in concrete preparation, which was accessible.
Based on the above research conclusions, it is feasible to prepare UHPC by partially replacing cement with RBP [28]. The recycling of construction waste can not only result in environmental protection, energy saving, emission reduction and green development, but also reduce the production cost of traditional UHPC [29,30,31]. In view of this, UHPC was prepared by partially replacing cement with RBP treated by active excitation in this paper. The physical and mechanical properties of RBP UHPC were studied and analyzed. In addition, the micro mechanism of the material was revealed based on SEM (Scanning Electron Microscope), XRD (X-ray diffraction) and MIP (Mercury intrusion porosimetry) tests, in order to enrich and develop the theoretical research and application of recycled UHPC.

2. Materials and Experimental Program

2.1. Raw Materials and Mix Proportion

P·O52.5 ordinary Portland cement produced by Henan Mengdian Group Cement Co., Ltd. (Henan, China). was used to prepare the RBP UHPC with a specific surface area of 386 m2/kg. The main technical indicators are shown in Table 1. The admixtures are first grade fly ash (FA) and silica fume (SF) produced by Henan Yuanheng Environmental Protection Engineering Co., Ltd. (Henan, China). The main components of the materials are listed in Table 2 and Table 3. Meanwhile, the brick is from the waste sintered clay brick produced by the demolition of Zhengzhou City. After crushing and screening, the powder with particle size less than 0.075 mm is selected. Then the RBP used in the test is obtained by physical excitation method (ball milling 45 min). The main components and technical indicators are presented in Table 4. The natural river sand provided by Henan Yutang Company (Henan, China) was used to select the part with particle size of 0.075–1.25 mm as fine aggregate. After cleaning, drying and screening, the mud content was less than 0.1%. In addition, Zhitai brand (Hebei, China) copper plated micro steel fibers with aspect ratio 60 are used. The main technical indicators are shown in Table 5. The additive was CQJ-JSS polycarboxylate superplasticizer produced by Shanghai Chenqi Chemical Technology Co., Ltd. (Henan, China), with water reduction rate of 32%. The water used for mixing and maintenance was ordinary tap water in Zhengzhou.
Table 6 presents the designed UHPC mix proportions with W/B ratio of 0.17, 0–50% of cement was replaced by RBP.

2.2. Specimen Preparation

Table 3 presents the designed UHPC mix proportions with W/B ratio of 0.17 and 0–50% of cement was replaced by RBP. According to previous research, 2% (vol%) steel fiber was beneficial to improve the strengths and deformation behavior of UHPC [32]. Therefore, we use 2% volume fraction of steel fiber.
The powder materials include cement, silica fume, fly ash, water reducing agent and RPB, which are mixed and stirred for 2–3 min to achieve uniform dispersion. Then, add all water and stir for 3–5 min until the material is sticky. Continue to stir, in the process of stirring slowly add sand and this process takes about 1 min; after all the sand starts to join continue to stir 2 min. Finally, steel fiber is added while stirring and stirring is continued for no less than 2 min after all fibers are added until the fibers are evenly dispersed in the mixture. All specimens in the relative humidity are greater than 50%, the temperature is 20 ± 5 °C indoor static 1~2 d after the removal of mold and then placed in a rapid steam curing box, at a rate of 15 °C/h to 90 °C, constant temperature 48 h and then to 15 °C/h cooling rate to room temperature. After steam curing, the specimens were placed in the standard curing room and cured to the specified age.

2.3. Testing Methods

In order to explore the effect of RBP replacing cement on performance of UHPC, the mechanical properties including flexural and compressive strength and uniaxial tensile properties and bonding properties of fiber with matrix were tested. The cube compressive strength test of UHPC was carried out according to the standard of concrete physical performance test method (Chinese standard GB/T 50081-2019). The uniaxial tensile test of ultra-high-performance concrete (UHPC) was carried out according to the tensile test method in the technical requirements of UHPC (Chinese standard T/CECS 10107-2020). The flexural toughness test of UHPC and the bonding properties of fiber with matrix were carried out according to the standard of fiber concrete test method (Chinese standard CECS 13: 2009).
In the cube compressive strength test, cubic specimens of 100 mm × 100 mm × 100 mm were compressed axially with loading rate of 1.2 MPa/s as seen in Figure 1. Six specimens were tested for each UHPC proportion. In the bending toughness test, the beam specimens of 100 mm × 100 mm × 400 mm (Figure 2) were bent with a loading rate of 0.2 mm/min until the initial crack deflection of the specimen with midspan deflection greater than 10.5-times or the specimen is about to be broken. Three specimens were tested for each group. In the axial tensile test, the dog-bone specimens were subjected to axial tension loads with a loading rate of 0.2 mm/min after pre-pull, as seen in Figure 3. Six specimens were tested for each UHPC proportion group. The specimen of fiber pull-out test is made by model method, with 5 specimens in each group. The loading diagram is shown in Figure 4.
In order to investigate the internal morphology of UHPC, the reaction process and hydration products of cementitious materials, the MIP, SEM and XRD measurements were conducted. Scanning electron microscope (SEM) produced by Hitachi, Japan, was used to conduct SEM test on UHPC samples after 28 days of curing. After drying the UHPC paste test block for 2 h, the central part was ground into powder and XRD test was carried out by ULTIMA IV X-ray powder diffractometer. Before the MIP test, UHPC samples with a side length of about 10 mm was taken and placed in a vacuum drying oven at 50 °C for 24 h and then sealed immediately. Then the pore structure of UHPC was analyzed by automatic mercury intrusion porosimetry and the apparent density, porosity and the content of each grade of pore size were tested to further explore the mechanism of recycled brick powder.

3. Results and Discussion

3.1. Compressive Strength

Figure 5 shows the change in compressive strength of RBP UHPC with different replacement rates with age.
From Figure 5, the compressive strength of UHPC in each group increased with the increase in curing time and at the same age, the compressive strength of each group decreased with an increase in RBP substitution amount. The 28 d strength of 50% substitution rate can still reach 143.2 MPa. At 28 d, the strength of 10–40% substitution rate decreased gradually, but the decrease was small.
The compressive strength of the reference group UHPC increases slightly with age, indicating that the hydration reaction inside the reference UHPC group has been basically completed after steam curing. With the increase in age, the strength at 7 d, 14 d and 28 d of UHPC in group R3 increased by 3.0%, 6.8% and 11.5% compared with that at 3 d, respectively. The 28 d strength of R1, R2, R4 and R5 increased by 3.4%, 9.1%, 13.5% and 13.3% compared with that at 3 d, respectively. It can be seen that with the increase in brick powder substitution rate, the strength of UHPC increases more with age. It also indicates that the hydration reaction inside the material lasted longer with the increase in brick powder substitution rate and the brick powder gradually played the pozzolanic activity.
The low early strength of RBP UHPC is due to the large specific surface area of brick powder, which adsorbs part of water and reduces the hydration reaction rate. In addition, the incorporation of brick powder reduces the early hydration of cement and small brick powder particles are wrapped on the surface of cement particles and hydration products, which also affects the rate of hydration reaction to a certain extent.
Hence, it can be summarized that though the addition of RBP could reduce the compressive strength of UHPC at early ages, the late strength growth rate of the material increased significantly with the increase in curing time. When the replacement ratio of RBP is less than 30%, the 28 d compressive strength of UHPC can still reach more than 150 MPa, which meets the requirements of the current specification for Ultra-High-Performance Concrete (UHPC); Technical Requirements (T/CECS 10107-2020); for compressive strength and reaches UC3 level (150 ≤ fcu < 180).

3.2. Flexural Strength

According to the specification titled fiber concrete test method standard (Chinese standard CECS 13:2009), the flexural toughness of the material can be evaluated according to the area ratios I5, I10 and I20 formed by the load–deflection curve corresponding to the initial crack deflection. The load–deflection curves of RBP UHPC specimens with different replacement rates are shown in Figure 6 and the calculation results of flexural toughness index are shown in Table 7.
It can be seen from Table 7 that the toughness indices I5, I10 and I20 of UHPC with RBP increased first and then decreased with the increase in recycled brick powder substitution rate. When the substitution rate was 40%, all the three indices reached the maximum values of 8.569, 22.507 and 38.169, respectively. Compared with group B, the flexural toughness indexes I5, I10 and I20 of group R4 increased by 19.3%, 90.9% and 173.8%, respectively. Compared with group R4, the flexural toughness index of group R5 decreased, but it still increased significantly for group B of the benchmark group.
When the replacement rate of brick powder was less than 30%, the initial cracking load of UHPC decreases with the increase in brick powder replacement rate, which is basically consistent with the influence of brick powder on the compressive strength of UHPC. Meanwhile, when the replacement rate of brick powder was ≥30%, the bending ultimate load of UHPC was higher than that of the reference group. Small brick powder particles can fill the pores inside the material and a large number of irregular brick powder particles increase the friction between steel fiber and UHPC matrix, thus, improving the bending ultimate load and bending toughness of the material. However, after brick powder replaced cement, the matrix strength of the material decreased and the stress before cracking of the specimen was mainly borne by the matrix, thus, reducing the initial cracking load of UHPC. When the replacement of brick powder reached 50%, the compressive strength of UHPC decreased significantly, resulting in the flexural toughness index of R5 group lower than R4.
For ideal elastoplastic materials, the values of I5, I10 and I20 are 5, 10 and 20, respectively [33]. Under the experimental conditions in this paper, the I5 value of UHPC is much larger than 5 and the I5, I10 and I20 values of the ideal elastic–plastic material are much higher than those of the ideal elastic–plastic material after the brick powder substitution rate reaches 40%. When the ideal elastic–plastic material reaches the initial crack, the load will no longer increase, while RBP UHPC has a stable strengthening stage after the initial crack and the peak load is about two times of the initial crack load. In addition, the initial crack deflection value of three times used in I5 calculation corresponds to the deflection limits. When the replacement rate of brick powder was greater than 30%, the value of I20 is much larger than 20, indicating that the flexural toughness of uhpc is significantly enhanced.

3.3. Uniaxial Tensile Property

The uniaxial tensile stress–strain curve of UHPC is shown in Figure 7 and the calculation results of uniaxial tensile properties are shown in Table 8.
It can be seen from Table 8 that the tensile elastic modulus and tensile strain of UHPC with RBP at different substitution rates first increase and then decrease with the increase in brick powder substitution rate and reach a maximum value at 40%. The elastic ultimate tensile strength of R1~R5 is greater than that of the reference group and R3 and R4 groups are better. It is proved that the incorporation of RBP improves the initial cracking strength of UHPC under uniaxial tensile load to a certain extent. Compared with the reference group, the elastic modulus of R1~R5 group increased by 87.8%, 167.9%, 259.3%, 387.6% and 113.1%, respectively. The slope of the linear phase of the stress–strain curve is the tensile elastic modulus. Larger tensile elastic modulus indicates stronger resistance to tensile deformation before initial cracking. With the increase in replacement rate of recycled brick powder, the tensile strength of UHPC increases first and then decreases and reaches the maximum when the replacement rate is 30%.
The addition of RBP could reduce the matrix strength of UHPC. However, under the axial tensile stress, the internal stress of the material is borne by the matrix and the fiber. The irregular appearance of the brick powder increases the friction between the fiber and the matrix and a large number of small brick powder particles fill the pores inside the material, tightly wrapped in the surface of the steel fiber, and then increase the tensile strength of the material. The tensile strain of UHPC reached the maximum when the cement is substituted by 40% RBP, which increased by 212.3% compared with the reference group.
In addition, the statistics of the data obtained in the experiment show that when the brick powder substitution rate is lower than 40%, the tensile strain of UHPC and the brick powder substitution rate are approximately in line with the following functional relationship:
μ t u = 1.672 r 2 − 19.575 r + 1026.429
In the formula: μtu is tensile strain (×10−6); r is the substitution rate of brick powder (%).

3.4. Bonding Properties of Fiber and Matrix

Sadoon et al. [34] believed that fiber pull-out test was one of the most suitable methods for studying the bonding properties of materials. The efficiency of fiber transfer stress depends largely on the bonding performance of fiber-matrix in UHPC. The ultimate bond strength (ffb) of steel fiber and matrix and the work (WFmax) of fiber under the maximum load when pulled out can accurately evaluate the bonding performance. Table 9 shows the calculation results for related indicators.
It can be seen from the table that the ultimate bond strength (ffb) and the maximum fiber pull-out load (Fmax) increase first and then decrease with the increase in brick powder substitution rate and reach the maximum value when the cement is replaced by 40% of RBP. It is similar to the bending toughness test. The ultimate bond strength between steel fiber and matrix is only related to the perimeter of steel fiber cross section, the length of embedded end and the maximum load. In this paper, the perimeter of the cross section and the length of the embedded end of the steel fiber are both fixed values, so the variation law for the maximum load and the ultimate bond strength is consistent and the two are linear. The bond strength between steel fiber and matrix in R4 group was the highest, which increased by 67.7% compared with the reference group. When the replacement rate of brick powder exceeded 40%, the ultimate bond strength began to decrease, but still increased by 44.6% compared with the reference group. The order of ultimate bond strength between steel fiber and matrix is: R4 > R3 > R5 > R2 > R1 > B. When the substitution rate of brick powder is ≤40%, the experimental data are fitted to obtain Figure 8. The ultimate bond strength is linearly positively correlated with the substitution rate of brick powder.
In uncracked composites, the stress is mainly transferred to the fiber longitudinal axis through friction at the interface. When the matrix is cracked, the load is transferred to the fiber that spans the crack; as the load increases, the final fiber is pulled out from the matrix. It can be seen from Table 9 that with the increase in brick powder substitution rate, the work performed at the maximum load in the test also increases. Compared with the reference group, the work under the maximum load of R1~R5 increased by 23.8%, 14.8%, 45.9%, 102.0% and 172.4%, respectively. The work of fibers at the maximum load increases, indicating that UHPC with brick powder has more excellent energy dissipation capacity and can effectively prevent crack propagation.

4. Microstructure of the UHPC

4.1. SEM Test

Figure 9 presents SEM images of UHPC with various RBP contents at 28 days. It shows the micro-morphology of the specimen magnified by 5000-times in SEM test. The specimen was selected from UHPC test block after 28 d compressive strength test.
SEM was used to study the morphology and microstructure of the reference sample and the samples containing RBP. When the RBP replacement of cement was 0, a large number of amorphous C-S-H gels can be observed and many fine powder particles adhere to its surface (Figure 9a). The microstructure compactness of UHPC sample with 10% RBP was slightly lower than that of the control group (0% RBP), which was mainly due to the decrease in cement content, resulting in a decrease in C-S-H gel, too little calcium hydroxide content and insufficient pozzolanic reaction (Figure 9b). When the RBP replacement of cement was 40%, it can be seen that the internal structure is relatively dense and a large number of C-S-H deposits together form a wavy layered structure. A small amount of powder particles is attached to the surface and no obvious holes are found (Figure 9c). The high content of SiO2 in RBP further reacts with calcium hydroxide to form C-S-H due to its pozzolanic activity [35]. However, with the further increase in brick powder substitution rate, the hydration products become relatively single, with only a small amount of C-S-H gel and a large number of pores (about 1 μm) on the surface of the hydration products can be seen (Figure 9d). Combined with its compressive strength, it can be seen that this is the main reason for the decrease in its strength. The microstructure change in UHPC is consistent with its mechanical properties. This is similar to the findings of ZMA B et al. [36,37].

4.2. XRD Test

The XRD tests were conducted on the specimens of UHPC. After drying the UHPC block paste for 2 h, the central part was grinded into powder and the test sample was obtained. The test results are shown in Figure 10.
It can be seen from the figure that the main crystalline phases measured in the experiment are SiO2, unhydrated cement clinker (C2S and C3S), Ca(OH)2, C-S-H, etc. The peaks at about 21° and 27°are silicon dioxide and there are few peaks in the reference group. With the addition of RBP, silicon dioxide increases and the peak gradually increases. This indicates that when the RBP replacement of cement was low, pozzolanic reaction between Ca(OH)2, RBP and mineral admixtures (fly ash, silica fume) takes place. A large amount of Ca(OH)2 is eliminated and plenty of C-S-H gel is formed [24,38]. This reaction leads to obvious enhancement in the of UHPC matrix in the later stage. When the RBP replacement of cement was high, although there is a large number of RBP, there is less cement and the Ca(OH)2 generated by cement hydration is insufficient to fully react with mineral admixtures to generate new C-S-H. This is also confirmed by the decrease in Ca(OH)2 peak with the increase in brick replacement ratio. It is worth noting that C2S and C3S mainly come from unhydrated cement clinker. The decrease in the peak value of the two indicates that when the RBP content reaches more than 30%, the unhydrated cement particles in UHPC decrease and the utilization rate of cement increases. Combined with the increase in the peak value of SiO2, it can be considered that the cement particles as filler are basically replaced by RBP.

4.3. MIP Test

The UHPC specimens were tested by mercury intrusion porosimetry (MIP) measurement. The pore distribution curves of RBP UHPC samples under different substitution rates are presented in Figure 11 and the tests data are shown in Table 10.
It can be seen from Figure 11 that with the increase in RBP content, the pore size distribution curve moves to the left as a whole, indicating that the addition of RBP refines the pore structure of UHPC and reduces the pore size of the material as a whole [39,40]. Meanwhile, it can be seen from Table 10 that when RBP replaces 10% cement, the porosity of UHPC decreases sharply, which is 8% lower than that of the reference group. However, with the increase in RBP replacement rate, the porosity of the material increases slowly. It can be seen that as the values of R3, R4 and R5 are so much smaller than that of B, R1 and R2, there may be an inflection point in the replacement rate of RBP and the median pore size decreases sharply after reaching a certain value. The most probable pore size is an important parameter reflecting the pore structure characteristics of materials. It represents the pore size corresponding to the maximum peak value on the pore size differential distribution curve and its physical meaning is the pore size with the maximum probability inside the material. It can be seen from the table that with the increase in RBP replacement rate, the most probable pore size in the material decreases first and then increases and the most probable pore size of UHPC samples in each group is less than 8 nm. The water and chloride penetrations into the UHPC are mainly by the pores; hence [41,42,43], it can be expected that UHPC will have better impermeability under a certain amount of RBP content.

5. Conclusions

  • The RBP has a certain weakening effect on the compressive strength development of UHPC. The compressive strength of UHPC decreases with the increase in RBP substitution rate, but the 28 d compressive strength of each group of specimens is not less than 140 MPa.
  • The initial cracking load of UHPC decreases with the increase in brick powder replacement rate. When the replacement rate of RBP was ≥30%, the bending ultimate load of UHPC was higher than that of the reference group. When the replacement rate is 40%, the flexural toughness of UHPC is optimal.
  • The tensile elastic modulus and tensile strain of UHPC with RBP at different substitution rates first increase and then decrease with the increase in brick powder substitution rate and reach the maximum value at 40%. With the increase in replacement rate of RBP, the tensile strength of UHPC increases first and then decreases and reaches the maximum 8.87 MPa when the replacement rate is 30%.
  • Adding recycled brick powder as cementitious material into UHPC can improve the bonding ability of steel fiber matrix and improve the energy dissipation capacity of the material. With the increase in RBP substitution rate, the ultimate bond strength of the specimen increases first and then decreases. The work at the maximum load increases continuously when the fiber is pulled out. When the replacement rate is 40%, the ultimate bond strength of RBP UHPC reaches the maximum value of 10.9 MPa.
  • The incorporation of RBP refines the pore structure of the UHPC matrix. In addition, RBP can increase the hydration degree of the cement paste and reduce the content of unhydrated cement particles. Meanwhile, the pozzolanic reactivity of RBP can also promote the further improvement of the hydration degree of the cementitious material.

Author Contributions

Conceptualization, C.Y.; data curation, W.F. and H.L.; formal analysis, W.F.; funding acquisition, C.Y.; investigation, H.L.; project administration, C.Y.; resources, C.Y.; supervision, C.Y.; visualization, W.F. and A.R.; writing—original draft, W.F. and H.L.; writing—review and editing, W.F., A.R. and H.L. All authors have read and agreed to the published version of the manuscript.

Funding

This study was funded by the Natural Foundation of China (numbers 52178258), Henan Province key research and development and promotion projects (numbers 202102310255), the Henan Province transportation science and technology plan project (numbers 2020J-2-7) and the Henan Provincial department of transportation Science and Technology plan project (numbers 2021J3).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The general data are included in the article. Additional data are available on request.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. NPCSC. Implementation Report on the Republic of Solid Waste Pollution Prevention Law; NPCSC 444; NPCSC: Beijing, China, 2017. [Google Scholar]
  2. Kırgız, M. Fresh and hardened properties of green binder concrete containing marble powder and brick powder. Eur. J. Environ. Civ. Eng. 2016, 20, 1–38. [Google Scholar] [CrossRef]
  3. Huang, B.; Wang, X.; Kua, H.; Geng, Y.; Bleischwitz, R.; Ren, J. Construction and demolition waste management in china through the 3r principle. Resour. Conserv. Recycl. 2018, 129, 36–44. [Google Scholar] [CrossRef]
  4. Batayneh, M.; Marie, I.; Asi, I. Use of selected waste materials in concrete mixes. Waste Manag. 2007, 27, 1870–1876. [Google Scholar] [CrossRef]
  5. Nigri, G.; Cherait, Y.; Nigri, S. Physical characterization and durability of blended cements based on brick powder. Civ. Environ. Eng. Rep. 2020, 30, 201–213. [Google Scholar] [CrossRef]
  6. Kirgiz, M.S. Use of ultrafine marble and brick particles as raw materials in cement manufacturing. Mater. Struct. 2015, 48, 2929–2941. [Google Scholar] [CrossRef]
  7. Wild, S.; Gailius, A.; Hansen, H.; Pederson, L.; Szwabowski, J. Pozzolanic properties of a variety of european clay bricks. Build. Res. Inf. 1997, 25, 170–175. [Google Scholar] [CrossRef]
  8. He, Z.H.; Zhu, H.N.; Zhang, M.Y.; Shi, J.Y.; Du, S.G.; Liu, B. Autogenous shrinkage and nano-mechanical properties of uhpc containing waste brick powder derived from construction and demolition waste. Constr. Build. Mater. 2021, 306, 124869. [Google Scholar] [CrossRef]
  9. Richard, P.; Cheyrezy, M. Composition of reactive powder concretes. Cem. Concr. Res. 1995, 25, 1501–1511. [Google Scholar] [CrossRef]
  10. Schmidt, M.; Fehling, E. Ultra-High-Performance Concrete: Research, Development and Application in Europe. Symp. Pap. 2005, 228, 51–78. [Google Scholar]
  11. Soliman, N.A.; Omran, A.F.; Tagnit-Hamou, A. Laboratory characterization and field application of novel ultra-high-performance glass concrete. ACI Mater. J. 2016, 113, 307–316. [Google Scholar] [CrossRef]
  12. Klemens, T. Flexible concrete offers new solutions. Concr. Constr. 2004, 49, 72–74. [Google Scholar]
  13. Zhang, Y.; Wei, S.; Liu, S.; Jiao, C.; Lai, J. Preparation of c200 green reactive powder concrete and its static–dynamic behaviors—Sciencedirect. Cem. Concr. Compos. 2008, 30, 831–838. [Google Scholar]
  14. Wang, D.; Shi, C.; Wu, Z.; Xiao, J.; Huang, Z.; Fang, Z. A review on ultra high performance concrete: Part II. hydration, microstructure and properties. Constr. Build. Mater. 2015, 96, 368–377. [Google Scholar] [CrossRef]
  15. Korpa, A.; Kowald, T.; Trettin, R. Phase development in normal and ultra high performance cementitious systems by quantitative X-ray analysis and thermoanalytical methods. Cem. Concr. Res. 2009, 39, 69–76. [Google Scholar] [CrossRef]
  16. Wang, X.; Yu, R.; Shui, Z.; Song, Q.; Zhang, Z. Mix design and characteristics evaluation of an eco-friendly ultra-high performance concrete incorporating recycled coral based materials. J. Clean. Prod. 2017, 165, 70–80. [Google Scholar] [CrossRef]
  17. El-Dieb, A.S. Mechanical, durability and microstructural characteristics of ultra-high-strength self-compacting concrete incorporating steel fibers. Mater. Des. 2009, 30, 4286–4292. [Google Scholar] [CrossRef]
  18. Juenger, M.; Siddique, R. Recent advances in understanding the role of supplementary cementitious materials in concrete. Cem. Concr. Res. 2015, 78, 71–80. [Google Scholar] [CrossRef]
  19. Ding, M.; Yu, R.; Feng, Y.; Wang, S.; Chen, L. Possibility and advantages of producing an ultra-high performance concrete (uhpc) with ultra-low cement content. Constr. Build. Mater. 2021, 273, 122023. [Google Scholar]
  20. Yalnkaya, A.; Opurolu, O. Hydration heat, strength and microstructure characteristics of uhpc containing blast furnace slag. J. Build. Eng. 2020, 34, 101915. [Google Scholar] [CrossRef]
  21. Ma, Z.; Tang, Q.; Wu, H.; Xu, J.; Liang, C. Mechanical properties and water absorption of cement composites with various fineness and contents of waste brick powder from c&d waste. Cem. Concr. Compos. 2020, 114, 103758. [Google Scholar]
  22. Zhao, Y.; Gao, J.; Liu, C.; Chen, X.; Xu, Z. The particle-size effect of waste clay brick powder on its pozzolanic activity and properties of blended cement. J. Clean. Prod. 2020, 242, 118521. [Google Scholar] [CrossRef]
  23. Zhao, Y.; Gao, J.; Xu, Z.; Li, S.; Chen, G. Long-term hydration and microstructure evolution of blended cement containing ground granulated blast furnace slag and waste clay brick. Cem. Concr. Compos. 2021, 118, 103982. [Google Scholar] [CrossRef]
  24. Lin, K.L.; Chen, B.Y.; Chiou, C.S.; Cheng, A. Waste brick’s potential for use as a pozzolan in blended portland cement. Waste Manag. Res. J. Int. Solid Wastes Public Clean. Assoc. Iswa 2010, 28, 647–652. [Google Scholar] [CrossRef] [PubMed]
  25. Cui, Z.; Ai, Q.; Yan, T.; Dong, L. The Study of the Construction Waste Brick Powder’s Activity. Adv. Mater. Res. 2014, 1079–1080, 309–311. [Google Scholar]
  26. Goncalves, J.P.; Tavares, L.M.; Filho, R.; Fairbairn, E. Performance evaluation of cement mortars modified with metakaolin or ground brick. Constr. Build. Mater. 2009, 23, 1971–1979. [Google Scholar] [CrossRef]
  27. Wu, H.; Liang, C.; Xiao, J.; Xu, J.; Ma, Z. Early-age behavior and mechanical properties of cement-based materials with various types and fineness of recycled powder. Struct. Concr. 2022, 23, 1253–1272. [Google Scholar] [CrossRef]
  28. Xiao, J.; Ma, Z.; Sui, T.; Ali, A.; Duan, Z. Mechanical properties of concrete mixed with recycled powder produced from construction and demolition waste. J. Clean. Prod. 2018, 188, 720–731. [Google Scholar] [CrossRef]
  29. He, Z.H.; Han, X.D.; Zhang, M.Y.; Yuan, Q.; Shi, J.Y.; Zhan, P.M. A novel development of green UHPC containing waste concrete powder derived from construction and demolition waste—ScienceDirect. Powder Technol. 2022, 398, 117075. [Google Scholar] [CrossRef]
  30. Tang, Q.; Ma, Z.; Wu, H.; Wang, W. The utilization of eco-friendly recycled powder from concrete and brick waste in new concrete: A critical review. Cem. Concr. Compos. 2020, 114, 103807. [Google Scholar] [CrossRef]
  31. Duan, Z.; Hou, S.; Xiao, J.; Li, B. Study on the essential properties of recycled powders from construction and demolition waste—Sciencedirect. J. Clean. Prod. 2020, 253, 119865. [Google Scholar] [CrossRef]
  32. Wu, Z.; Shi, C.; Khayat, K.H. Investigation of mechanical properties and shrinkage of ultra-high performance concrete: Influence of steel fiber content and shape. Composites 2019, 174, 107021.1–107021.12. [Google Scholar] [CrossRef]
  33. Gao, D.; Zhao, L.; Feng, H. Flexural toughness of steel fiber reinforced concrete and its evaluation method. J. Build. Mater. 2014, 17, 783–789. (In Chinese) [Google Scholar]
  34. Abdallah, S.; Fan, M.; Zhou, X. Pull-Out Behaviour of Hooked End Steel Fibres Embedded in Ultra-high Performance Mortar with Various W/B Ratios. Int. J. Concr. Struct. Mater. 2017, 11, 301–313. [Google Scholar] [CrossRef]
  35. Lin, K.L.; Wu, H.H.; Shie, J.L.; Hwang, C.L.; Cheng, A. Recycling waste brick from construction and demolition of buildings as pozzolanic materials. Waste Manag. Res. 2010, 28, 653–659. [Google Scholar] [CrossRef] [PubMed]
  36. Ma, Z.; Liu, M.; Duan, Z.; Liang, C.; Wu, H. Effects of active waste powder obtained from c&d waste on the microproperties and water permeability of concrete. J. Clean. Prod. 2020, 257, 120518. [Google Scholar]
  37. Sun, Z.; Liu, F.; Tong, T.; Qi, C.; Yu, Q. Hydration of Concrete Containing Hybrid Recycled Demolition Powders. J. Mater. Civ. Eng. 2017, 29, 1–7. [Google Scholar] [CrossRef]
  38. Shao, J.; Gao, J.; Zhao, Y. Characteristics of recycled clay brick powder-cement cementitious system. J. Southeast Univ. 2019, 49, 375–379. (In Chinese) [Google Scholar]
  39. Langan, B.W.; Weng, K.; Ward, M.A. Effect of silica fume and fly ash on heat of hydration of portland cement. Cem. Concr. Res. 2002, 37, 1045–1051. [Google Scholar] [CrossRef]
  40. Metin, D.; Hakan, C.; IlkerBekir, T.; Tayfun, U. Pozzolanic effect of andesite waste powder on mechanical properties of high strength concrete. Constr. Build. Mater. 2018, 165, 494–503. [Google Scholar]
  41. Lian, C.; Zhuge, Y.; Beechama, S. The relationship between porosity and strength for porous concrete. Constr. Build. Mater. 2011, 25, 4294–4298. [Google Scholar] [CrossRef]
  42. Xue, S.; Zhang, P.; Bao, J.; He, L.; Yang, S. Comparison of mercury intrusion porosimetry and multi-scale x-ray ct on characterizing the microstructure of heat-treated cement mortar. Mater. Charact. 2019, 160, 110085. [Google Scholar] [CrossRef]
  43. Liang, C.; Pan, B.; Ma, Z.; He, Z.; Duan, Z. Utilization of CO2 curing to enhance the properties of recycled aggregate and prepared concrete: A review. Cem. Concr. Compos. 2019, 105, 103446. [Google Scholar] [CrossRef]
Buildings 12 01622 g001 550
Figure 1. Loading diagram of cube compressive test.
Figure 1. Loading diagram of cube compressive test.
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Figure 2. Loading diagram of bending toughness test.
Figure 2. Loading diagram of bending toughness test.
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Figure 3. Loading diagram of uniaxial tensile specimen.
Figure 3. Loading diagram of uniaxial tensile specimen.
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Buildings 12 01622 g004 550
Figure 4. Loading diagram of fiber pull-out test.
Figure 4. Loading diagram of fiber pull-out test.
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Buildings 12 01622 g005 550
Figure 5. Changes in compressive strength of RBP UHPC with age.
Figure 5. Changes in compressive strength of RBP UHPC with age.
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Buildings 12 01622 g006 550
Figure 6. Load–deflection curve of recycled brick powder UHPC.
Figure 6. Load–deflection curve of recycled brick powder UHPC.
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Buildings 12 01622 g007 550
Figure 7. Tensile stress–strain curves of RBP UHPC under different substitution rates.
Figure 7. Tensile stress–strain curves of RBP UHPC under different substitution rates.
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Buildings 12 01622 g008 550
Figure 8. Relationship between brick powder substitution rate and bond strength.
Figure 8. Relationship between brick powder substitution rate and bond strength.
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Buildings 12 01622 g009 550
Figure 9. SEM images of UHPC specimens in each group. (a) B group. (b) R1 group. (c) R4 group. (d) R5 group.
Figure 9. SEM images of UHPC specimens in each group. (a) B group. (b) R1 group. (c) R4 group. (d) R5 group.
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Figure 10. XRD analysis of each group of specimens.
Figure 10. XRD analysis of each group of specimens.
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Figure 11. The pore size distribution of recycled brick powder UHPC under different substitution rates.
Figure 11. The pore size distribution of recycled brick powder UHPC under different substitution rates.
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Table
Table 1. Main technical indicators of cement.
Table 1. Main technical indicators of cement.
Specific Surface Area/m2·kg−1StabilitySO3/%Cl−/%MgO/%Ignition Loss/%Setting Time/min28 d Strength/MPa
Initial SetFinal SetBreak off StrengthCompressive Strength
386qualification2.380.0463.933.061502008.963.4
Table
Table 2. The main components of fly ash.
Table 2. The main components of fly ash.
ComponentSiO2Al2O3Fe2O3CaOTiO2SO3
content/%54.7624.566.544.851.851.32
Table
Table 3. Main components of silica fume.
Table 3. Main components of silica fume.
ComponentSiO2Al2O3Fe2O3CaONaO2MgO
content/%96.760.310.070.100.970.11
Table
Table 4. Main indexes and components of recycled brick powder.
Table 4. Main indexes and components of recycled brick powder.
Specific Surface Area m2·kg−1Moisture Content/%Major Contents of Components/%
SiO2Al2O3Fe2O3CaOMgONa2O
600≤0.5068.1516.517.201.800.940.65
Table
Table 5. Main technical indexes of steel fiber.
Table 5. Main technical indexes of steel fiber.
Length/mmDiameter/mmDensity/g·cm−3FormTensile Strength/MPa
12.00.27.8formed straight and smooth>2000.0
Table
Table 6. UHPC mixture ratio of RBP (kg/m3).
Table 6. UHPC mixture ratio of RBP (kg/m3).
GroupReplacement
Ratio (%)		CementRBPFly AshSilica FumeRiver SandWater
Reducing Admixture		Water
B07000100200100030170
R11063070100200100030170
R220560140100200100030170
R330490210100200100030170
R440420280100200100030170
R550350350100200100030170
Table
Table 7. Calculation results of bending toughness index.
Table 7. Calculation results of bending toughness index.
GroupCracking Load
(Fcr/KN)		Initial Crack Deflection (δ/mm)Initial Rupture Strength
(fcr/MPa)		Ultimate Load (F/KN)I5I10I20Equivalent Bending Strength (fe/MPa)Flexural Toughness Ratio Re
B45.5320.70913.66077.9657.18511.82213.93515.3231.122
R143.7930.65413.13873.4236.38710.97314.05215.2771.163
R239.8520.51611.95668.2357.30313.71018.37714.3201.197
R343.6200.74113.14681.1107.53613.30317.81015.1291.151
R435.1920.54510.55894.7278.56922.50738.16915.8621.502
R535.3580.58510.60780.2528.23120.02533.14913.7021.292
Table
Table 8. Tensile properties of recycled brick powder UHPC under different substitution rates.
Table 8. Tensile properties of recycled brick powder UHPC under different substitution rates.
GroupElastic Ultimate Tensile Strength (fte/MPa)Elasticity Ultimate Strain
(μte/×10−6)		Modulus of Elongation (Ete/GPa)Tensile Strength (ftu/MPa)Tensile Strain (μtu/×10−6)
B5.8939015.106.13975
R16.2722128.377.111026
R26.1915340.457.551528
R38.4115554.258.871617
R46.488873.636.673045
R56.3419732.186.381830
Table
Table 9. Fiber pull-out test results.
Table 9. Fiber pull-out test results.
GroupLoad when Sliding Begins (Fuf/N)Maximum Load (Fmax/N)Work at Maximum Load (WFmax/N·mm)Ultimate Bond Strength between Steel Fiber and Matrix (ffb/MPa)
B71.578.429.06.50
R163.198.235.98.1
R257.4107.433.38.9
R360.1126.342.310.5
R484.0131.558.610.9
R5106.8113.479.79.4
Table
Table 10. The pore structure parameters of recycled brick powder UHPC with different substitution rates.
Table 10. The pore structure parameters of recycled brick powder UHPC with different substitution rates.
GroupPorosity (%)Average Pore Size (nm)Median Pore Diameter (nm)Most
Probable Pore Size (nm)		Apparent Density (g/mL)
B4.8643.10136.747.432.306
R14.4939.2074.295.432.342
R24.6334.10122.865.392.239
R34.7720.727.925.322.336
R44.8016.065.905.302.206
R55.7120.496.965.342.270
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Yuan, C.; Fu, W.; Raza, A.; Li, H. Study on Mechanical Properties and Mechanism of Recycled Brick Powder UHPC. Buildings 2022, 12, 1622. https://doi.org/10.3390/buildings12101622

AMA Style

Yuan C, Fu W, Raza A, Li H. Study on Mechanical Properties and Mechanism of Recycled Brick Powder UHPC. Buildings. 2022; 12(10):1622. https://doi.org/10.3390/buildings12101622

Chicago/Turabian Style

Yuan, Chengfang, Weicheng Fu, Ali Raza, and Haofei Li. 2022. "Study on Mechanical Properties and Mechanism of Recycled Brick Powder UHPC" Buildings 12, no. 10: 1622. https://doi.org/10.3390/buildings12101622

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