Preparation and Compression Resistance of Lightweight Concrete Filled with Lightweight Calcium Carbonate Reinforced Expanded Polystyrene Foam

Lightweight concrete is widely used in the construction industry due to its low density and high strength. In this paper, lightweight concrete was prepared by a simple two-step method. Firstly, the light calcium carbonate reinforced epoxy macrospheres (LCR-EMS) material was obtained by adhering calcium lighter carbonate powder to the expanded polystyrene foam spheres (EPS) material using the “balling method”. In the second step, the LCR-EMS was mixed with water, cement, and the hollow glass microspheres (HGMS) material using the “molding method” to obtain lightweight concrete. The combination of macroscopic photographs and microscopic morphology shows that the LCR-EMS material itself is uniformly encapsulated and well bonded to the matrix. Test results show that the density of the lightweight concrete decreases with an increase in the volume fraction of stacked LCR-EMS, the diameter, and the proportion of HGMS in the matrix, but it decreases with a decrease in the number of layers of LCR-EMS. The compressive strength of lightweight concrete exhibits a completely opposite trend. When three layers of LCR-EMS were used as filler material, the density and compressive strength of the concrete were 1.246 g/cm3 and 8.19 MPa, respectively. The density and maximum compressive strength of lightweight concrete were 1.146 g/cm3 and 6.37 Mpa, respectively, when filled with 8–9 mm-2L-90 svol% of LCR-EMS and 40 wt% of HGMS in the matrix. Compared with lightweight concrete filled with 90% EPS, the density increased by 20% while the compressive strength increased by 300%.


Introduction
The building materials industry is an important basic industry of the national economy and provides support for improving living conditions, managing the ecological environment, and developing a circular economy [1,2].The building materials industry is a key area of industrial energy consumption, carbon emissions, and an important sector in achieving the "double carbon" goal.Lightweight concrete is a special type of concrete that has a Epoxy resin (Araldite ® LY 1564) and amine curing agent (Aradur ® 3486) were purchased from Huntsman Chemical Co., Ltd., The Woodlands, TX, USA.Regarding these materials, the bisphenol A-type epoxy resin was a colorless transparent liquid with a viscosity of 1200-1400 mPa-s at 25 • C, a density of 1.1-1.2g/cm 3 , and an epoxy index (ISO 3001 [32]) of 5.80-6.05eq/kg.The amine curing agent was a light yellow liquid with a viscosity range of 10-20 mPa-s at 25 • C, a density of 0.94-0.95g/cm 3 , and an amine value (ISO 9702 [33]) of 8.55-9.30eq/kg.Light calcium carbonate was purchased from Shandong Rongwei Chemical Co., Ltd., Jinan, China.The particle size of light calcium carbonate powder was 40-50 µm.The 42. 5 Portland cement was purchased from Shenzhen Zhongning Technology Co., Ltd., Shenzhen, China.Expanded polystyrene foams (EPS) are produced in Hangzhou Hangchao Packaging Materials Co., Ltd., Hangzhou, China, with a diameter of 8-11 mm.Hollow glass microspheres (HGMS) material of type K1 was purchased from the 3M Company in St. Paul, MN, USA.The compressive strength of K1 was 1.72 MPa, the true density was 0.125 g/cm 3 , and the particle size was 30~120 µm.

Preparation Process of LCR-EMS and Characterization
Figure 1 is a schematic diagram of the preparation process of LCR-EMS.From the figure, it can be seen that the preparation process of LCR-EMS is mainly divided into three steps.In the first step, EPS is added to the epoxy hardener system so that its surface is completely covered by the resin.In this experiment, the ratio of epoxy resin to hardener was 3:1.For bisphenol A-type epoxy resin, amine hardener, and EPS, the masses used were 39 g, 13 g, and 5 g, respectively.In the second step, the lightweight concrete powder was uniformly wrapped around the surface of EPS by the "rolling ball method".The lightweight calcium carbonate powder must be in excess to ensure that each EPS is completely encapsulated by the powder.In the third step, the preformed LCR-EMS was placed in an oven for curing with stepwise heating.The heating temperatures were 50 • C for 2 h and 80 • C for 1 h.Afterwards, the LCR-EMS with completed high temperature curing was subjected to room-temperature curing for more than 24 h.
Polymers 2023, 15, x FOR PEER REVIEW of LCR-EMS.The trend of the compressive strength of the lightweight concrete was pletely opposite.The density and strength of the overall material can be controll adjusting the ratio, size, and diameter of the LCR-EMS in the lightweight concrete.

Materials
Epoxy resin (Araldite ® LY 1564) and amine curing agent (Aradur ® 3486) wer chased from Huntsman Chemical Co., Ltd., The Woodlands, TX, USA.Regarding materials, the bisphenol A-type epoxy resin was a colorless transparent liquid with cosity of 1200-1400 mPa-s at 25 °C, a density of 1.1-1.2g/cm 3 , and an epoxy inde 3001 [32]) of 5.80-6.05eq/kg.The amine curing agent was a light yellow liquid w viscosity range of 10-20 mPa-s at 25 °C, a density of 0.94-0.95g/cm 3 , and an amine (ISO 9702 [33]) of 8.55-9.30eq/kg.Light calcium carbonate was purchased from Shan Rongwei Chemical Co., Ltd., Jinan, China.The particle size of light calcium carb powder was 40-50µm.The 42.5 Portland cement was purchased from She Zhongning Technology Co., Ltd., Shenzhen, China.Expanded polystyrene foams are produced in Hangzhou Hangchao Packaging Materials Co., Ltd., with a diame 8-11 mm.Hollow glass microspheres (HGMS) material of type K1 was purchased the 3M Company in the United States.The compressive strength of K1 was 1.72 MP true density was 0.125 g/cm 3 , and the particle size was 30~120µm.

Preparation Process of LCR-EMS and Characterization
Figure 1 is a schematic diagram of the preparation process of LCR-EMS.Fro figure, it can be seen that the preparation process of LCR-EMS is mainly divided into steps.In the first step, EPS is added to the epoxy hardener system so that its sur completely covered by the resin.In this experiment, the ratio of epoxy resin to har was 3:1.For bisphenol A-type epoxy resin, amine hardener, and EPS, the masses were 39 g, 13 g, and 5 g, respectively.In the second step, the lightweight concrete po was uniformly wrapped around the surface of EPS by the "rolling ball method".The weight calcium carbonate powder must be in excess to ensure that each EPS is comp encapsulated by the powder.In the third step, the preformed LCR-EMS was placed oven for curing with stepwise heating.The heating temperatures were 50 °C for 2 80 °C for 1 h.Afterwards, the LCR-EMS with completed high temperature curin subjected to room-temperature curing for more than 24 h. Figure 2 shows the macroscopic photographs and density characterization of EMS.From Figure 2a,b, it can be seen that the surface of LCR-EMS is more unif wrapped and the spheres are regular.Figure 2c,d show the relationship between t ameter and density of LCR-EMS.In order to avoid random data and reduce the er much as possible, 50 spheres of LCR-EMS were randomly selected from each gro mass and diameter measurements.From Figure 2c, it can be seen that when the diameter of EPS beads is in the range of 8-9 mm, the densities of LCR-EMS with diff layers are mainly distributed in three regions: 0.160-0.259g/cm 3 (LCR-EMS-1L), 0.502 g/cm 3 (LCR-EMS-2L), 0.472-0.618g/cm 3 (LCR-EMS-3L).This shows that bot diameter and number of wrapped layers play a positive role in LCR-EMS.The t Figure 2 shows the macroscopic photographs and density characterization of LCR-EMS.From Figure 2a,b, it can be seen that the surface of LCR-EMS is more uniformly wrapped and the spheres are regular.Figure 2c,d show the relationship between the diameter and density of LCR-EMS.In order to avoid random data and reduce the error as much as possible, 50 spheres of LCR-EMS were randomly selected from each group for mass and diameter measurements.From Figure 2c, it can be seen that when the initial diameter of EPS beads is in the range of 8-9 mm, the densities of LCR-EMS with different layers are mainly distributed in three regions: 0.160-0.259g/cm 3 (LCR-EMS-1L), 0.354-0.502g/cm 3 (LCR-EMS-2L), 0.472-0.618g/cm 3 (LCR-EMS-3L).This shows that both EPS diameter and number of wrapped layers play a positive role in LCR-EMS.The thicker LCR-EMS helps to increase its own compressive strength but also contribute to increase the density of the lightweight concrete.It can also be seen from the figure that the average densities of LCR-EMS with a different number of layers are 0.206 g/cm 3 (1L), 0.426 g/cm 3 (2L), and 0.547 g/cm 3 (3L), respectively.
Polymers 2023, 15, x FOR PEER REVIEW 4 of LCR-EMS helps to increase its own compressive strength but also contribute to increa the density of the lightweight concrete.It can also be seen from the figure that the averag densities of LCR-EMS with a different number of layers are 0.206 g/cm 3 (1L), 0.426 g/cm (2L), and 0.547 g/cm 3 (3L), respectively.

Preparation Process of Lightweight Concrete
Figure 3 shows a schematic diagram of the preparation process of lightweight co crete.In this paper, the preparation process is divided into three steps.First, the matr filler is configured.LCR-EMS, cement, water, and HGMS were stirred and mixed, whe the mass ratio of water to the sum of HGMS and cement was 1:3.The prepared initi samples were then poured into molds (70.7 mm × 70.7 mm × 70.7 mm).In order to redu the generation of bubbles, defects, etc., during the filling process, pre-compression can b used to prepare the lightweight concrete.Finally, after 48 hours of compaction, the spec mens were demolded and cured.The temperature of the curing box was controlled 25°C, the air humidity was 95%, and the curing time was 28 days.The main purpose this experiment was to investigate the effects of various factors on the compressive pro erties of lightweight concrete.The influencing factors were mainly the stacking volum fraction, the diameter and number of layers of LCR-EMS, and the grading of HGMS an cement.The specific mix designs for the experiment are shown in Table 1.The fille HGMS is the mass percentage of matrix cement.

Preparation Process of Lightweight Concrete
Figure 3 shows a schematic diagram of the preparation process of lightweight concrete.In this paper, the preparation process is divided into three steps.First, the matrix filler is configured.LCR-EMS, cement, water, and HGMS were stirred and mixed, where the mass ratio of water to the sum of HGMS and cement was 1:3.The prepared initial samples were then poured into molds (70.7 mm × 70.7 mm × 70.7 mm).In order to reduce the generation of bubbles, defects, etc., during the filling process, pre-compression can be used to prepare the lightweight concrete.Finally, after 48 hours of compaction, the specimens were demolded and cured.The temperature of the curing box was controlled at 25 • C, the air humidity was 95%, and the curing time was 28 days.The main purpose of this experiment was to investigate the effects of various factors on the compressive properties of lightweight concrete.The influencing factors were mainly the stacking volume fraction, the diameter and number of layers of LCR-EMS, and the grading of HGMS and cement.The specific mix designs for the experiment are shown in Table 1.The filled HGMS is the mass percentage of matrix cement.

Characterization of Composites
A digital analytical balance (Guangzhou BGD Experimental Instrument Supply Company, Guangzhou, China) and digital caliper were used to measure the mass and diameter of the LCR-EMS, respectively, which were used to calculate to obtain the density of the LCR-EMS.The compressive strength of lightweight concrete was measured and analyzed using a universal testing machine (CMT5350, Shenzhen Sansi Zongheng Technology Co., Ltd., Shenzhen, China).This experiment is based on GB/T16491-2008 as the testing standard.Among them, the maximum test force of the universal testing machine is 300 KN and the

Characterization of Composites
A digital analytical balance (Guangzhou BGD Experimental Instrument Supply Company, Guangzhou, China) and digital caliper were used to measure the mass and diameter of the LCR-EMS, respectively, which were used to calculate to obtain the density of the LCR-EMS.The compressive strength of lightweight concrete was measured and analyzed using a universal testing machine (CMT5350, Shenzhen Sansi Zongheng Technology Co., Ltd., Shenzhen, China).This experiment is based on GB/T16491-2008 as the testing standard.Among them, the maximum test force of the universal testing machine is 300 KN and the maximum test range is 1100 mm.A scanning electron microscope (SEM) (JEM-4701, JEOL, Tokyo, Japan) was used to observe the bonding problem of the interface in lightweight concrete.The observed specimens were brittle cross sections.

Characterization of Density and Compressive Strength of Lightweight Concrete Filled with Different Stacking Volume Fractions
In order to investigate the effect of LCR-EMS with different stacking ratios on the compressive strength and density of lightweight concrete, we set five parameters with different stacking volume fractions of 20%, 40%, 60%, 80%, and 90%. Figure 4a shows the density of lightweight concrete filled with different stacking volume fractions of LCR-EMS.The density of lightweight concrete decreases with an increasing LCR-EMS stacking volume fraction, where the density of unfilled LCR-EMS lightweight concrete is 1.679 g/cm 3 and the density of filled 90 svol% LCR-EMS lightweight concrete is 1.146 g/cm 3 .Figure 4b shows the compressive strength curves of lightweight concrete filled with different stacking volume fractions of LCR-EMS.The trend of compressive strength of lightweight concrete filled with different stacking volume fractions of LCR-EMS is the same as that of density.The higher the fraction volume of LCR-EMS, the lower the compressive strength of the concrete.In this case, the compressive strength of concrete filled with 90  In order to investigate the effect of LCR-EMS with different stacking ratios on the compressive strength and density of lightweight concrete, we set five parameters with different stacking volume fractions of 20%, 40%, 60%, 80%, and 90%. Figure 4a shows the density of lightweight concrete filled with different stacking volume fractions of LCR-EMS.The density of lightweight concrete decreases with an increasing LCR-EMS stacking volume fraction, where the density of unfilled LCR-EMS lightweight concrete is 1.679 g/cm 3 and the density of filled 90 svol% LCR-EMS lightweight concrete is 1.146 g/cm 3 .Figure 4b shows the compressive strength curves of lightweight concrete filled with different stacking volume fractions of LCR-EMS.The trend of compressive strength of lightweight concrete filled with different stacking volume fractions of LCR-EMS is the same as that of density.The higher the fraction volume of LCR-EMS, the lower the compressive strength of the concrete.In this case, the compressive strength of concrete filled with 90 svol% LCR-EMS is 6.37 MPa.The compressive strength decreases significantly compared to the concrete without LCR-EMS.The compressive strength of lightweight concrete decreased with the increase in the LCR-EMS stacking volume.When the LCR-EMS stacking volume is 20%, the decreasing trend of compressive strength of lightweight concrete is obvious, which indicates that the appropriate increase in the filling volume of LCR-EMS with a relatively small LCR-EMS stacking volume does not cause the destruction of the compressive strength of lightweight concrete.The maximum compressive strength of lightweight concrete was 6.79 MPa and 6.37 MPa when 80 svol% and 90 svol% LCR-EMS were added, respectively.There is a significant decrease in the maximum compressive strength of lightweight concrete Polymers 2023, 15, 4642 6 of 11 (12.68 MPa) as compared to the maximum compressive strength of lightweight concrete with 20 svol% LCR-EMS.As the stacking volume fraction of LCR-EMS increases, the probability of their contacting each other in the matrix increases, and when the material is subjected to compressive loading, the stress concentration phenomenon occurs at the point of contact.The LCR-EMS forms a pore structure inside the material, which can effectively reduce the density of the composite material.However, LCR-EMS is also a type of defect and is more susceptible to stress damage compared to the matrix.In addition, an increase in LCR-EMS void volume not only tends to create bubbles during concrete preparation but also increases the likelihood of interfacial defects in the material.
volume is 20%, the decreasing trend of compressive strength of lightweight conc obvious, which indicates that the appropriate increase in the filling volume of LCR with a relatively small LCR-EMS stacking volume does not cause the destruction compressive strength of lightweight concrete.The maximum compressive stren lightweight concrete was 6.79 MPa and 6.37 MPa when 80 svol% and 90 svol% LCR were added, respectively.There is a significant decrease in the maximum comp strength of lightweight concrete (12.68 MPa) as compared to the maximum comp strength of lightweight concrete with 20 svol% LCR-EMS.As the stacking volume fr of LCR-EMS increases, the probability of their contacting each other in the mat creases, and when the material is subjected to compressive loading, the stress conc tion phenomenon occurs at the point of contact.The LCR-EMS forms a pore str inside the material, which can effectively reduce the density of the composite m However, LCR-EMS is also a type of defect and is more susceptible to stress damag pared to the matrix.In addition, an increase in LCR-EMS void volume not only te create bubbles during concrete preparation but also increases the likelihood of inte defects in the material.

Characterization of Density and Compressive Strength of Lightweight Concrete Filled LCR-EMS of Different Diameters
Figure 5 shows the density and compressive strength curves of lightweight co filled with different diameters of LCR-EMS.From the figure, it can be obtained th densities of the lightweight concrete are 1.146 g/cm 3 (8-9 mm) and 1.010 g/cm 3 (10-1 and the corresponding maximum compressive strengths are 6.37 MPa and 6.29 MP compressive strength of lightweight concrete decreases with an increasing inner dia This is mainly due to the fact that the smaller the diameter of the LCR-EMS, the fas force transmission rate at its surface, that is, the faster the force diffusion rate.The the force diffusion rate, the faster the rate of stress concentration inside the concrete fore, the smaller the diameter of the filled LCR-EMS, the greater the compressive str

Characterization of Density and Compressive Strength of Lightweight Concrete Filled with LCR-EMS of Different Diameters
Figure 5 shows the density and compressive strength curves of lightweight concrete filled with different diameters of LCR-EMS.From the figure, it can be obtained that the densities of the lightweight concrete are 1.146 g/cm 3 (8-9 mm) and 1.010 g/cm 3 (10-11 mm), and the corresponding maximum compressive strengths are 6.37 MPa and 6.29 MPa.The compressive strength of lightweight concrete decreases with an increasing inner diameter.This is mainly due to the fact that the smaller the diameter of the LCR-EMS, the faster the force transmission rate at its surface, that is, the faster the force diffusion rate.The faster the force diffusion rate, the faster the rate of stress concentration inside the concrete; therefore, the smaller the diameter of the filled LCR-EMS, the greater the compressive strength.

Characterization of Density and Compressive Strength a of Lightweight Concrete Filled LCR-EMS of Different Layers
The improved performance of single-component LCR-EMS inevitably leads to crease in the mechanical properties of multi-component lightweight concrete.In ord investigate the effect of reinforcing body layers on the compressive strength of m

Characterization of Density and Compressive Strength a of Lightweight Concrete Filled with LCR-EMS of Different Layers
The improved performance of single-component LCR-EMS inevitably leads to an increase in the mechanical properties of multi-component lightweight concrete.In order to investigate the effect of reinforcing body layers on the compressive strength of multi-phase composite lightweight concrete, LCR-EMS with an inner diameter of 8-9 mm was used in this series of experiments, and the stacking volume fraction of LCR-EMS added to the matrix was 90%.One, two, and three reinforcing layers were selected and a control group of EPS was established.Figure 6 shows the density and compressive strength curves of lightweight concrete filled with different layers of LCR-EMS.It can be seen from the figure that the variation in the number of LCR-EMS layers also affects the density and compressive strength of concrete.As the number of LCR-EMS layers increases, the density and compressive strength of lightweight concrete increases.When three layers of LCR-EMS were used as filler material, the density and compressive strength of the concrete were 1.246 g/cm 3 and 8.19 MPa, respectively.The compressive strength of lightweight concrete increased with the increase in the number of layers of LCR-EMS.In particular, compared to the compressive strength of EPS-filled concrete, the compressive strength of filled reinforced layers increased by 98.1% (one layer); 300.6% (two layers); and 415.1 (three layers), respectively.As the number of layers of LCR-EMS increases, the trend of increasing compressive strength improvement of lightweight concrete becomes more and more evident.This is due to the fact that as the number of layers increases, the lightweight calcium carbonate/epoxy structure becomes more robust and less susceptible to damage under stress.The increase in the compressive strength of the filler also benefits the compressive properties of the overall composite.

Characterization of Density and Compressive Strength of Lightweight Concrete Filled Different HGMS Volume Ratios in the Matrix
In addition to the stacking volume fraction, number of layers, and internal di of LCR-EMS filled in concrete affecting the performance of lightweight concrete, t trix composition also affects the performance of lightweight concrete.In this serie periments, K1-grade HGMS and cement mixed with volume proportions of 20%, 40 60% were selected as the matrix for lightweight concrete.Figure 7 shows the dens compressive strength curves of lightweight concrete filled with a matrix of d HGMS volume ratios.From the figure, it can be seen that the filler content of HG the matrix also affects the density and compressive strength of lightweight concre to the lightweight nature of HGMS, the overall density and compressive strength matrix decreases as the filler content increases.The density and maximum comp strength of the concrete were 0.992 g/cm 3 and 6.01 MPa, respectively, when the filling content in the matrix was 60%.The compressive strength of lightweight c decreases with increasing HGMS content in the matrix.The decrease in the comp strength of lightweight concrete with the increase in the proportion of HGMS in the is mainly due to the fact that HGMS is a tiny, hollow, spherical powder, which is

Characterization of Density and Compressive Strength of Lightweight Concrete Filled with Different HGMS Volume Ratios in the Matrix
In addition to the stacking volume fraction, number of layers, and internal diameter of LCR-EMS filled in concrete affecting the performance of lightweight concrete, the matrix composition also affects the performance of lightweight concrete.In this series of experiments, K1-grade HGMS and cement mixed with volume proportions of 20%, 40%, and 60% were selected as the matrix for lightweight concrete.Figure 7 shows the density and compressive strength curves of lightweight concrete filled with a matrix of different HGMS volume ratios.From the figure, it can be seen that the filler content of HGMS in the matrix also affects the density and compressive strength of lightweight concrete.Due to the lightweight nature of HGMS, the overall density and compressive strength of the matrix decreases as the filler content increases.The density and maximum compressive strength of the concrete were 0.992 g/cm 3 and 6.01 MPa, respectively, when the HGMS filling content in the matrix was 60%.The compressive strength of lightweight concrete decreases with increasing HGMS content in the matrix.The decrease in the compressive strength of lightweight concrete with the increase in the proportion of HGMS in the matrix is mainly due to the fact that HGMS is a tiny, hollow, spherical powder, which is inherently self-lubricating and non-absorbent.Due to the smooth surface of HGMS and insufficient bonding with cement paste, it leads to more brittle defects in the concrete.
compressive strength curves of lightweight concrete filled with a matrix of d HGMS volume ratios.From the figure, it can be seen that the filler content of HG the matrix also affects the density and compressive strength of lightweight concre to the lightweight nature of HGMS, the overall density and compressive strength matrix decreases as the filler content increases.The density and maximum comp strength of the concrete were 0.992 g/cm 3 and 6.01 MPa, respectively, when the filling content in the matrix was 60%.The compressive strength of lightweight c decreases with increasing HGMS content in the matrix.The decrease in the comp strength of lightweight concrete with the increase in the proportion of HGMS in the is mainly due to the fact that HGMS is a tiny, hollow, spherical powder, which is ently self-lubricating and non-absorbent.Due to the smooth surface of HGMS and ficient bonding with cement paste, it leads to more brittle defects in the concrete.

Cross-Section SEM and EDS Mapping of Lightweight Concrete
Figure 8 shows the SEM and EDS mapping of the lightweight concrete.From Figure 8a, it can be seen that the average thickness of the LCR-EMS-2 layer can be up to about 745 µm, but there is still a clear demarcation line between the ball and the matrix; but due to the material variability of the ball wall and the matrix and the human factor during the filling process leading to the bonding not being close enough, which leads to the compressive strength of the lightweight concrete, the improvement is not much.Figure 8c also shows that there are still some defects and holes inside the lightweight concrete.Figure 8c-f show the EDS mapping of the lightweight concrete, from which it can be seen that the elements in the mapping are consistent with the elements contained in the raw material.

Compression Resistance Mechanism of AR-EMS Filled Composite Lightweight Concrete
Figure 9 shows the compressor mechanism of LCR-EMS filled lightweight concrete.From the figure, it can be seen that when the concrete is compressed by an external force, the force is quickly transferred from the concrete matrix to the LCR-EMS, and then from the LCR-EMS to the matrix or to the next LCR-EMS.The defects of the lightweight concrete are mainly divided into two parts, one is the pore defects in the matrix, and the other is the LCR-EMS.The compressive strength of the whole lightweight concrete depends not only on the strength of the matrix, but also on the compressive strength of LCR-EMS.If the compressive strength of the LCR-EMS itself is very poor, then when the force is transferred to the ball a stress concentration will immediately occur, and thus the damage will start from the LCR-EMS and then be transferred to the matrix, which will eventually lead to the failure of the material.The same phenomenon of material fatigue failure occurs when there are many defects in the matrix.Once the destructive force exceeds the maximum compressive strength of the concrete, the lightweight concrete will fail.
to the material variability of the ball wall and the matrix and the human factor during the filling process leading to the bonding not being close enough, which leads to the compressive strength of the lightweight concrete, the improvement is not much.Figure 8c also shows that there are still some defects and holes inside the lightweight concrete.Figure 8c-f show the EDS mapping of the lightweight concrete, from which it can be seen that the elements in the mapping are consistent with the elements contained in the raw material.

Compression Resistance Mechanism of AR-EMS Filled Composite Lightweight Concrete
Figure 9 shows the compressor mechanism of LCR-EMS filled lightweight concrete.
From the figure, it can be seen that when the concrete is compressed by an external force, the force is quickly transferred from the concrete matrix to the LCR-EMS, and then from the LCR-EMS to the matrix or to the next LCR-EMS.The defects of the lightweight concrete are mainly divided into two parts, one is the pore defects in the matrix, and the other is the LCR-EMS.The compressive strength of the whole lightweight concrete depends not only on the strength of the matrix, but also on the compressive strength of LCR-EMS.If the compressive strength of the LCR-EMS itself is very poor, then when the force is transferred to the ball a stress concentration will immediately occur, and thus the damage will start from the LCR-EMS and then be transferred to the matrix, which will eventually lead to the failure of the material.The same phenomenon of material fatigue failure occurs

Conclusions
Calcium carbonate-reinforced LCR-EMS is obtained by adhering calcium carbo powder to EPS using the "balling method", and lightweight concrete is obtained by ing LCR-EMS with cement, hollow glass microspheres, etc., using the "molding meth Lightweight concrete has different properties depending on the influencing factors addition of hollow glass microspheres to the filler can further reduce the occurren defects and thus improve the mechanical properties of the concrete.The compre strength of lightweight concrete was negatively correlated with the stacking volume tion of LCR-EMS, the initial inner diameter of epoxy composite spheres, and the fi amount of HGMS in the matrix.However, it is positively correlated with the numb reinforcing layers of LCR-EMS.When three layers of LCR-EMS were used as the fille density and compressive strength of concrete were 1.246 g/cm 3 and 8.19 MPa, respecti The density and maximum compressive strength of the concrete filled with a 90% sta volume fraction of LCR-EMS were 1.146 g/cm 3 and 6.37 MPa, respectively.Compared

Conclusions
Calcium carbonate-reinforced LCR-EMS is obtained by adhering calcium carbonate powder to EPS using the "balling method", and lightweight concrete is obtained by mixing LCR-EMS with cement, hollow glass microspheres, etc., using the "molding method".Lightweight concrete has different properties depending on the influencing factors.The addition of hollow glass microspheres to the filler can further reduce the occurrence of defects and thus improve the mechanical properties of the concrete.The compressive strength of lightweight concrete was negatively correlated with the stacking volume fraction of LCR-EMS, the initial inner diameter of epoxy composite spheres, and the filling amount of HGMS in the matrix.However, it is positively correlated with the number of reinforcing layers of LCR-EMS.When three layers of LCR-EMS were used as the filler, the density and compressive strength of concrete were 1.246 g/cm 3 and 8.19 MPa, respectively.The density and maximum compressive strength of the concrete filled with a 90% stacked volume fraction of LCR-EMS were 1.146 g/cm 3 and 6.37 MPa, respectively.Compared with the lightweight concrete filled with 90% EPS, the density increased by 20%, but the compressive strength increased by 300%.A hard-shell structure can be formed by encapsulating expanded polystyrene foam beads with calcium carbonate powder.The more layers there are, the more stable and solid the hard-shell structure becomes, thus making it easier to resist external destructive forces.The reduction in the diameter of the filled LCR-EMS results in fewer pores and fewer defects between them, which ultimately increases the compressive strength of the concrete.

Figure 1 .
Figure 1.Schematic diagram of the preparation process of LCR-EMS.

Figure 1 .
Figure 1.Schematic diagram of the preparation process of LCR-EMS.

Figure 2 .
Figure 2. Macroscopic photographs and the density characterization of LCR-EMS.(a) Photograp of LCR-EMS with a different number of layers.(b) Photographs of LCR-EMS with different diam ters in the same number of layers.(c) Diameter and density distribution graph of LCR-EMS in d ferent layers.(d) Diameter and density distribution graph of LCR-EMS with different diameters the same number of layers.

Figure 2 .
Figure 2. Macroscopic photographs and the density characterization of LCR-EMS.(a) Photographs of LCR-EMS with a different number of layers.(b) Photographs of LCR-EMS with different diameters in the same number of layers.(c) Diameter and density distribution graph of LCR-EMS in different layers.(d) Diameter and density distribution graph of LCR-EMS with different diameters at the same number of layers.

Figure 3 .
Figure 3. Schematic diagram of lightweight concrete preparation process.

Figure 4 .
Figure 4. Density (a) and compressive strength (b) curves of lightweight concrete filled with ent stacking volumes of LCR-EMS.

Figure 4 .
Figure 4. Density (a) and compressive strength (b) curves of lightweight concrete filled with different stacking volumes of LCR-EMS.

Polymers 2023 ,Figure 5 .
Figure 5. Density (a) and compressive strength (b) curves of lightweight concrete filled with ent diameters of LCR-EMS.

Figure 5 .
Figure 5. Density (a) and compressive strength (b) curves of lightweight concrete filled with different diameters of LCR-EMS.

Figure 6 .
Figure 6.Density (a) and compressive strength (b) curves of lightweight concrete filled wit ent layers of LCR-EMS.

Figure 6 .
Figure 6.Density (a) and compressive strength (b) curves of lightweight concrete filled with different layers of LCR-EMS.

Figure 7 .
Figure 7. Density (a) and compressive strength (b) curves of lightweight concrete filled with of different HGMS volume ratios.

Figure 7 .
Figure 7. Density (a) and compressive strength (b) curves of lightweight concrete filled with matrix of different HGMS volume ratios.

Figure 8 .
Figure 8. Cross-sectional SEM and EDS mapping of lightweight concrete.(a) Lightweight concrete profile at low magnification including matrix, LCR-EMS inner wall and wall thickness.(b) Matrix SEM of lightweight concrete.(c) High magnification profile of lightweight concrete.(d) Mapping of the Ca element.(e) Mapping of the Si element.(f) Mapping of the O element.

Figure 8 .
Figure 8. Cross-sectional SEM and EDS mapping of lightweight concrete.(a) Lightweight concrete profile at low magnification including matrix, LCR-EMS inner wall and wall thickness.(b) Matrix SEM of lightweight concrete.(c) High magnification profile of lightweight concrete.(d) Mapping of the Ca element.(e) Mapping of the Si element.(f) Mapping of the O element.

Table 1 .
Lightweight concrete samples with different parameters.

Table 1 .
Lightweight concrete samples with different parameters.