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Article

Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle

by
Heng Wang
and
Jianyong Pang
*
School of Civil Engineering and Architecture, Anhui University of Science and Technology, Huainan 232001, China
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(12), 9569; https://doi.org/10.3390/su15129569
Submission received: 8 May 2023 / Revised: 2 June 2023 / Accepted: 12 June 2023 / Published: 14 June 2023
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Abstract

:
In order to study the mechanical properties of rubber concrete (RC) with different rubber particle sizes after dry–wet cycles in a sulfate environment, apparent morphology analysis, mass loss analysis, relative dynamic elastic modulus analysis, compressive strength loss analysis, internal microscopic characteristics and deterioration degree analysis of ordinary concrete (NC) and rubber concrete after dry–wet cycles were compared and analyzed. The results show that with the increase in the number of dry–wet cycles, the surface caves of rubber concrete increase, the internal microcracks develop and penetrate, and the macroscopic strength increases first and then decreases significantly. The high elasticity of rubber effectively improves the expansion force caused by sulfate attack and the dry–wet cycle. The deterioration degree of RC in each dry–wet cycle stage is obviously better than that of NC. When the rubber particle size is 0.85 mm, the performance of the sample is the best. After 120 days of dry–wet cycle, the compressive strength is reduced by 37.4%, and the compressive strength of concrete with a rubber particle size of 0.85 mm is reduced by 11.2%. After cyclic loading, the deterioration degree of concrete is 5.1% lower than that of ordinary concrete.

1. Introduction

In recent years, with the rapid development of the automobile industry, there have been more and more waste rubber tires, and the utilization of waste rubber has also been widely studied [1,2,3]. It has been widely used in recent years to make rubber concrete by mixing waste rubber into rubber particles or rubber powder into concrete [4,5,6,7]. Compared with ordinary concrete, concrete mixed with a certain amount of rubber improves the frost resistance [8], toughness [9] and impact resistance [10] of concrete under certain conditions. Hanbing Liu et al. [11] used rubber to partially replace fine aggregate and mixture to produce rubber concrete. With an increase in the rubber content from 0% to 20%, the compressive strength of rubber concrete decreases from 34.76 MPa to 33.41 MPa, and the elastic modulus decreases from 31.75 GPa to 24.73 GPa. Osama Youssf et al. [12] prepared concrete mixtures with rubber contents of 0%, 10%, 20%, 30%, 40% and 50%. Different mechanical properties were measured. The results showed that the impact resistance of concrete increased by about 3.5 times when the rubber content of concrete increased from 0% to 50%. It has great potential in structural applications, especially in seismic zones. Jiaqing Wang et al. [13] prepared fiber rubber concrete by adding polypropylene fiber and rubber particles. Macro polypropylene fiber and rubber aggregate can improve the fracture energy of ordinary concrete. The ultrasonic pulse velocity shows that the quality of concrete samples is good. The fracture morphology and ESEM images show the positive effect of rubber polymer and polypropylene fiber on crack propagation. The incorporation of rubber particles can effectively alleviate the pollution problem of waste rubber tires and has good development prospects.
China contains a large amount of sulphate saline soil [14], which subtly erodes surrounding concrete houses, roads and tunnels [15]. Sulfate is a corrosive medium, which is extremely harmful and has a great influence on the durability of concrete [16,17,18]. The hydration products of ordinary Portland cement react with sulfate to form expansive crystals, such as ettringite, gypsum, etc., which produce volume expansion to induce the development of micro-cracks, and ultimately damage the concrete [19,20,21]. Dry–wet cycles caused by environmental conditions such as day and night temperature differences and rainy and snowy seasons will affect the strength of concrete. Dry–wet cycles accelerate the destruction process of concrete by sulfate erosion [22,23]. Jianming Gao et al. [24] outlined that, compared with the single sulfate attack damage process, the peak value of the dynamic elastic modulus under simple sulfate erosion is about 1.035. After 174 days of immersion, the dynamic elastic modulus decreased to 1.024. The dynamic elastic modulus value was 1.03 under the action of composite sulfate erosion and a 40% bending load, while the dynamic elastic modulus value decreased to 0.935 under the combined action of the sulfate and dry–wet cycle. Both the bending load and dry–wet cycle can accelerate the damage process of sulfate attacking concrete. Wu Ruidong et al. [25] carried out the sulfate dry–wet cycle test of concrete with different contents of metal tailings powder. The results show that the proper addition of metal tailings powder can improve the sulfate corrosion resistance of C50 concrete. Wei Tian et al. [26] revealed the damage evolution of concrete by scanning electron microscopy (SEM) and computerized tomography (CT); in the early stage of sulfate attack, the pore structure of concrete was destroyed, ettringite and gypsum were formed, and the quality and strength increased. As the deterioration progresses, the expansion force of the product and the salt crystallization pressure of the sulfate crystal act on the inner wall of the concrete and accelerate the deterioration. The quality and strength of concrete decreased sharply, indicating that the quality and strength of concrete increased first and then decreased with the increase in the number of dry and wet cycles of sulfate attack. Jin-Jun Guo et al. [27] studied the effect of different dry–wet time ratios on sulfate attack of concrete by designing different dry–wet time ratios. When the dry–wet ratio was 5:1, the compressive strength and splitting tensile strength of 252 days were reduced by 24% and 11%, respectively, compared with the initial value, and the concrete deterioration was the most serious. At present, the research on the dry–wet cycle of ordinary concrete by sulfate attack is relatively mature [28,29], but there is little research on the dry–wet cycle of rubber concrete by sulfate attack. Concrete roads and tunnels in the sulfate saline soil area are not only subjected to dry–wet cycles in a sulfate environment but are also damaged by cyclic loading [30,31,32]. Therefore, it is of great significance to ensure the durability and fatigue resistance of rubber concrete (RC) after a dry–wet cycle in a sulfate environment for the application of green concrete [33,34].
Therefore, in this paper, a dry–wet cycle test and cyclic loading–unloading test were carried out on rubber concrete with different rubber particle sizes in a sulfate environment. The damage and deterioration degree of RC after different dry–wet cycle stages and the fatigue performance of RC after cyclic loading–unloading were measured and analyzed. The internal damage of concrete was reflected by non-destructive ultrasonic testing technology [35] and scanning electron microscopy, and the microscopic mechanism was analyzed.

2. Test

2.1. Raw Materials

The test cement was P·C42.5-grade composite Portland cement produced by Huainan Bagongshan. The fly ash was grade I fly ash produced by Huainan Pingwei Power Plant. The main chemical composition of the cementitious material is shown in Table 1. The medium-sized sand of Huaihe River was used, with a fineness modulus of 2.67, bulk density of 1450 kg/m3 and apparent density of 2650 kg/m3. The stones used were gravel melon seeds with a particle size distribution of 5~15 mm. The rubber was produced by Dujiangyan Huayi Rubber Co., Ltd. (Deyang, China) The rubber particle size was 0.85 mm, 1–3 mm and 3–6 mm. The chemical composition of rubber particles is shown in Table 2, and the parameter index is shown in Table 3. The HPWR standard high-performance water-reducing agent produced by Shaanxi Qinfen Building Materials Factory (Weinan, China) in China was used as the water-reducing agent; the main component is polycarboxylic acid, the proportion is 1.0%, and the water reduction rate is 25.0%. The mixing water used was ordinary tap water.

2.2. Mix Proportion and Specimen Preparation

The test refers to the China ordinary concrete mix design specification to design the mix ratio, and the final mix ratio of ordinary concrete is determined as water:sand:stone:cement:fly ash:water reducer = 153:751:1121:330:43:3.5. The test rubber has 0.85 mm, 1–3 mm and 3–6 mm (three kinds of rubber particle size), with the rubber particles added according to a cementing material quality of 10% of the volume to an equal volume instead of sand. The rubber:concrete mix ratio is shown in Table 4.
The concrete specimens were prepared at room temperature. The concrete specimens in this test were cylindrical specimens of Φ50 mm × 100 mm. The specimens were placed in a standard curing room (relative humidity ≥ 95%, temperature 20 ± 2 °C) for 24 h after the concrete was molded. After the specimens were demoulded, they were placed in a saturated calcium hydroxide solution and maintained in a standard curing room for 90 days, and then the test was started. The concrete specimens were divided into four groups: NC, RC-0.85, RC-1-3 and RC-3-6. The uniaxial compressive strength and fatigue failure strength of each group of specimens after 0, 30, 60, 90, 120 cycles of dry and wet cycles were tested. Each group has 30 specimens, making up a total of 120 specimens.

2.3. Test Scheme Design

In this paper, the particle size of rubber particles is taken as the research parameter, and RC is taken as the research object. Among them, rubber particles are used as fine aggregate to replace sand in an equal volume, the dosage is designed to be 10%, and the particle sizes of rubber particles are 0.85 mm, 1–3 mm, and 3–6 mm, respectively. The high temperature of 105 ± 5 °C was set up in the electrothermal constant-temperature drying box to dry the test block, so as to avoid the error influence of the internal moisture of concrete on the dry–wet cycle damage, and the initial quality was weighed after drying and cooling to room temperature.
The dry–wet cycle test was carried out in an electrothermal constant-temperature drying oven. The sample was taken out after soaking in 5% Na2SO4 solution for 16 h, and then placed in an oven at 80 °C for 6 h. After drying, it was cooled for 2 h. One dry–wet cycle was 24 h, and the number of dry–wet cycles was 0, 30, 60, 90, and 120 times. To ensure the concentration of sodium chloride solution requirements, the solution was replaced every 30 days. After every 30 dry–wet cycles, the test block was placed in an electrothermal constant temperature drying oven and dried. After wiping the residual sulfate with clear water at both ends of the test block, the drying quality of RC and NC was measured. The NN-4B non-metallic ultrasonic detection analyzer was used to determine the ultrasonic parameters [36]. The sampling period was 0.4 µs and the emission voltage was 500 V.
The cyclic loading and unloading tests were carried out using an RDL-200 electronic creep relaxation tester. Two different test loading paths were designed for RC and NC with different dry–wet cycles, which were the uniaxial compression test path and cyclic loading–unloading test path. The uniaxial compression test adopts displacement control, the speed is set to 1 mm/min, until the test block is destroyed, and the uniaxial compressive failure load of the cylinder is measured. In the cyclic loading and unloading test, the test block is pre-loaded with a 500 N force to ensure the correct alignment and full contact between the test block and the test device. The test process adopts stress control, and the loading and unloading rate is 30 KN/min. The upper limit of the loading load is 60% of the uniaxial compressive failure load, and the lower limit of the unloading load is 100 N. A loading and unloading process is used as a cycle, and a total of 50 cycles are performed.

3. Experimental Results and Analysis

3.1. Appearance Analysis

In the early stage of dry–wet cycle, the appearance of RC specimens with three different rubber particle sizes did not change significantly. With the dry–wet cycle, the pit corrosion on the concrete surface increased significantly or small cracks appeared. The apparent morphology of RC specimens with different rubber particle sizes after 90 and 120 dry–wet cycles is shown in Figure 1.
As shown in Figure 1a,b, after 90 dry–wet cycles, there are many erosion holes on the surface of the concrete specimen, and the edges of the upper and lower ends are passivated. The cement mortar at the end of the RC specimen with a rubber particle size of 3–6 mm is slightly peeled off, and the damage is the most serious. After 120 dry–wet cycles, the concrete test block is seriously eroded, micro-cracks appear on the surface, the upper and lower ends are passivated, and even some test blocks appear to have fine aggregate shedding, exposing the internal coarse aggregate. This is due to the erosion of sulfate solution, and SO42− establishes a three-dimensional transmission area at the end of the test piece to accelerate the erosion process. In the middle and late stages of the dry–wet cycle, the sulfate solution accelerates the deterioration rate of the concrete. With the continuous immersion and drying of water molecules in the RC, the internal pores increase, the cracks gradually penetrate, the internal bonding force and friction force of the concrete decrease, the structure gradually loosens, and the surface of the test block peels off significantly. Secondly, the rubber particles in RC do not participate in the cement hydration reaction, and there is a lack of strong chemical bonding force between rubber particles and other aggregates, resulting in a large gap and accelerating the erosion rate of the sulfate solution. With the increase in the particle size of the rubber particles, the gap around the rubber particles increases, and the range of crystal erosion damage caused by SO42− to the concrete increases, which accelerates the invasion of SO42−. With the progress of the dry–wet cycle, the crystals accumulate in the pores of the concrete, forming a large crystal pressure, resulting in an increase in the pores and the penetration of the cracks, and the concrete surface forms more obvious cracks. The experimental phenomena show that with the increase in dry–wet cycles, the surface damage of RC specimens becomes more serious, and with the increase in rubber particles, the internal voids increase. At this time, the erosion damage of the sulfate solution to RC specimens becomes more serious, and the corrosion resistance of concrete specimens is worse. Among them, the damage of RC samples with a rubber particle size of 3–6 mm is the most serious, and the corrosion resistance of RC samples with a rubber particle size of 0.85 mm is the best.

3.2. Quality Loss Analysis

Mass loss is a macro damage index that can measure the concrete after dry–wet cycle to a certain extent. In the test of Gaowen Zhao et al. [37], the mass of concrete specimens increased first and then decreased with the increase in sulfate solution erosion time, and the higher the concentration of sulfate solution, the faster the mass growth and decline. Figure 2 plots the relative mass (Km) of NC and RC at different cycles. With the increase in dry–wet cycles, the mass of samples increased slightly and then decreased obviously. At 60 dry–wet cycles, the mass of the RC specimen reached the peak, and then the mass of the specimen began to decrease gradually, and the mass after 120 dry–wet cycles was less than that before erosion. This is due to the early dry and wet cycle of SO42− ions into the concrete, and cement hydration products to form ettringite and gypsum as well as other expansion, resulting in an increased sample quality. In the later stage of the dry–wet cycle, the high elasticity of rubber particles was unable to alleviate the damage caused by the expansion stress generated by the expansion, and the internal holes gradually penetrated into cracks, resulting in the spalling of cement mortar on the surface of the test block and a decrease in the quality of the test block. The calculation formula of the mass relative value is as follows:
K m = m n m 0 × 100 %
where Km represents the relative value of mass (%); and mn and m0 represent the mass of the specimen at the nth and 0th dry–wet cycles (kg).
In the 60 dry–wet cycles, the relative value of the mass of ordinary concrete is less than that of rubber concrete, which is due to a large number of SO42− ions entering the sample and reacting to generate expansion, and the mass is increased. The rubber particles in RC and the coarse and fine aggregates in RC optimize the gradation of concrete and slow down the rate of solution drying and immersion, and the mass loss is reduced compared with ordinary concrete. After 60 dry–wet cycles, the relative mass value of rubber concrete is significantly greater than that of ordinary concrete. This is because the high elasticity of rubber relieves the expansion stress generated by the expansion, and the crack generation rate is significantly slower than that of NC. The smaller the rubber particles, the greater the relative mass value of RC. The cement hydration products of concrete materials without sulfate attack are mainly composed of Ca(OH)2 and Ca4Al2O7·19H2O. After 120 dry–wet cycles in sulfate solution, Ca(OH)2 in cement hydrate gradually forms gypsum and ettringite under the chemical corrosion of sulfate solution and dry–wet cycles [38]. The damage of sulfate solution to concrete in the later stage is mainly due to the gradual accumulation of expansions caused by the main chemical reaction between Ca(OH)2 and SO42− ions in the solution.
C a ( O H ) 2 + S O 4 2 − + 2 H 2 O → C a S O 4 ⋅ 2 H 2 O + 2 O H −
3 C 3 A + 3 C a S O 4 ⋅ 2 H 2 O + 26 H 2 O → 3 C a O ⋅ A l 2 O 3 ⋅ 3 C a S O 4 ⋅ 32 H 2 O
The Km of samples with rubber particle sizes of 0.85 mm, 1–3 mm and 3–6 mm reached the maximum values, which were 0.66%, 1.24% and 2.06% different from that after 120 d dry–wet cycle. The larger the rubber particle size, the greater the change rate of Km, the worse the impermeability and the higher the mass loss rate. It can be seen that the damage of 0.85 mm rubber mixed with concrete under the coupling of dry–wet cycle and sulfate attack is the smallest, and the mass loss is significantly reduced.

3.3. Relative Dynamic Elastic Modulus Analysis

The relative dynamic elastic modulus [39,40] can be used to reflect the internal damage of concrete specimens after dry–wet cycles in a sulfate environment and to evaluate the durability of concrete. Using an NN-4B non-metallic ultrasonic testing analyzer to measure the relative wave velocity of the sample, to calculate the relative dynamic elastic modulus of the specimen, the following formula [41] was used:
E dr = E dt E d 0 × 100 % = T 0 2 T t 2 × 100 % = V t 2 V 0 2 × 100 %
where Edr represents the relative dynamic elastic modulus (%); Edt and Ed0 represent the dynamic elastic modulus (MPa) of the specimens after different dry–wet cycles and before dry–wet cycles. Tt and T0 represent the sound time (s) of the specimen after different dry–wet cycles and before dry–wet; Vt and V0 represent the ultrasonic wave velocity (m/s) of the specimens after different dry–wet cycles and before dry–wet cycles.
The relationship between the number of dry–wet cycles and the relative dynamic elastic modulus of RC and NC specimens is shown in Figure 3. From the diagram, it can be seen that with the increase in the number of dry–wet cycles, the relative dynamic elastic modulus of concrete increases first and then decreases, and the relative dynamic elastic modulus of NC specimens is smaller than that of RC specimens. This is due to a large number of SO42− ions entering the interior of the specimen to react to generate expansion, reducing the diffusion rate of sulfate, improving the compactness of concrete, and greatly reducing the speed of salt solution entering the void. The high elasticity of the rubber particles in the RC specimen alleviates the damage caused by the drying shrinkage force generated by the solution baking and immersion. In the 60 dry–wet cycles, the relative dynamic elastic modulus of RC specimens showed an increasing trend, and the relative dynamic elastic modulus of RC specimens with a rubber particle size of 1–3 mm was the highest. This is due to the rubber particles with a particle size of 3–6 mm. The interfacial transition zone between the rubber and the cement matrix in the RC specimen is obvious, the regional bonding force is weak, and it is easy to develop cracks. Therefore, the relative dynamic elastic modulus is lower than the test block with other rubber particle sizes.
The relative dynamic elastic modulus of concrete specimens reached the peak at 60 dry–wet cycles, and then decreased rapidly. The relative dynamic elastic modulus of RC and NC with rubber particle sizes of 0.85 mm, 1–3 mm and 3–6 mm decreased by 13.8%, 23.2%, 33.1% and 38.8%, respectively, at 120 dry–wet cycles. The four groups of concrete samples were damaged internally after dry–wet cycles. The internal damage to concrete mixed with 0.85 mm rubber was the smallest, and the internal damage to ordinary concrete was the largest. This is because after 60 dry–wet cycles, the expansion force generated by the expansion products inside the specimen is greater than the tensile strength of the internal structure, and the high elasticity of the rubber particles cannot alleviate the damage caused by the expansion force and dry–wet cycles. With the increase in the number of dry–wet cycles, the density of the test block decreases and the relative dynamic elastic modulus decreases. It can be seen that adding rubber can effectively improve the internal damage of concrete after the dry–wet cycle. The smaller the rubber particle size is, the smaller the damage is, and the 0.85 mm rubber particle size is the best.

3.4. Analysis of Compressive Strength Loss

In this paper, the compressive strength of the specimen was measured using an RDL electronic creep relaxation tester. The physical diagram and the damage morphology of the specimen are shown in Figure 4a,b.
The relative compressive strength Kf was used to measure the mechanical properties of concrete after dry–wet cycles of sulfate attack.
K f = f cn f c 0
where fcn is the strength value of sulfate attack after dry–wet cycle, and fc0 is the strength value of the same age under standard curing.
The relationship between dry–wet cycles and relative compressive strength of concrete specimens is shown in Figure 5. With the increase in dry–wet cycles, the compressive strength of RC and NC increased first and then decreased, which can be divided into the early growth stage and the later damage stage. The corrosion resistance coefficient of the compressive strength of the concrete specimens in the early stage of erosion is increasing. First, the concrete continues to undergo a cement hydration reaction in the sulfate solution and is still in the curing stage. At this time, the hydration reaction ability of the concrete is slightly greater than the sulfate erosion ability. Second, the SO42− ions in the sulfate solution enter the concrete and react with the cement hydration products to form ettringite, gypsum and other expansion substances, which fill the pores inside the concrete, increase the compactness of the concrete and increase the compressive strength. Under the combined action of the two, the Kf value of concrete specimens increased in the early stage of erosion. With the further progress of erosion, the expansions such as ettringite generated by concrete hydration products and SO42− ions increase, which promotes the rapid development of cracks. During the dry–wet cycle, the sulfate continuously eroded the weak interface connection between the coarse aggregate and the cement mortar, which had caused damage inside the concrete. Therefore, after 60 dry–wet cycles, the compressive strength of concrete samples continued to decline. This is consistent with its macroscopic quality loss and other changes.
In the process of the dry–wet cycle, the Kf value of rubber concrete is greater than that of ordinary concrete, and the smaller the rubber particle size, the stronger the sulfate resistance of the specimen and the better the durability. This is because the gypsum and ettringite formed by sulfate ions and cement hydration products fill the internal voids of concrete, and the air group at the interface between rubber particles in RC and cement mortar blocks the capillary pores, reduces the diffusion rate of sulfate ions and improves the compactness of concrete. The high elasticity of rubber particles alleviates the double damage caused by erosion and dry–wet cycle and alleviates the generation and development of cracks. The compactness of RC specimens is better than that of NC specimens, and the relative compressive strength is improved. The larger the particle size of rubber particles, the weaker the interfacial transition zone inside the RC specimen, the more prominent the defects, the easier the crack to develop and penetrate, the faster the erosion rate of sulfate solution, and the greater the compressive strength damage of the specimen. When the number of dry–wet cycles is 120, the Kf values of concrete with a rubber particle size of 0.85 mm, 1–3 mm and 3–6 mm is reduced by 11.2%, 25.1% and 26.3%, respectively, while the Kf value of ordinary concrete is reduced by 37.4%. The strength of concrete is greatly reduced, and the loss of compressive strength of RC with a particle size of 0.85 mm is the least. This shows that the rubber particles with an appropriate particle size enhance the corrosion resistance of concrete during the dry–wet cycle of sulfate solution. When the rubber particle size is large, the weak area of the RC interface is obvious, which makes the concrete specimen easy to damage.

3.5. Deterioration Analysis after Cyclic Loading

Constant amplitude cyclic loading–unloading tests were carried out on specimens subjected to different dry–wet cycles in sulfate solution, and the fatigue failure strength of the specimens was obtained. Compared with the initial uniaxial compressive strength of the specimens before cyclic loading–unloading, the degradation coefficient P was analyzed.
P = F 0 − F i F 0
P represents the deterioration coefficient; F0 represents the uniaxial compressive strength of concrete before cyclic loading and unloading; Fi represents the fatigue failure strength of concrete after cyclic loading and unloading.
The relationship between the uniaxial compressive strength and fatigue failure strength of concrete specimens under different dry–wet cycles is shown in Figure 6. It can be seen from the figure that the uniaxial compressive strength of the four groups of concrete decreased under cyclic loading and unloading, and the deterioration coefficient increased continuously. With the increase in dry–wet cycles, the deterioration coefficient of RC and NC specimens increased, and the fatigue damage of concrete specimens caused by cyclic loading was more obvious. It can be concluded that the initial damage of the specimen is aggravated under the dual action of dry–wet cycle and sulfate attack, and the more the number of cycles, the greater the fatigue damage of the specimen after 50 cycles of loading and unloading.
After 60 dry–wet cycles, the deterioration degree of ordinary concrete is always greater than that of rubber concrete, and the RC with rubber particle size of 0.85 mm has the best fatigue resistance. After 120 dry–wet cycle, the deterioration coefficient of concrete with a rubber particle size of 0.85 mm, 1–3 mm and 3–6 mm is 10.8%, 14.2% and 15.5%, respectively, and the deterioration coefficient of ordinary concrete is 16.9%. Under the action of fatigue load, rubber particles, as a part of concrete, play a role of energy absorption and dissipation in weak parts such as initial cracks and crack development by compression and extension, inhibit the generation and further expansion of microcracks, and effectively alleviate the fatigue damage caused by the cyclic load to concrete [42,43]. The results show that rubber particles can optimize the fatigue performance of concrete to a certain extent. The smaller the rubber particle size, the smaller the deterioration coefficient and the smaller the fatigue damage.

3.6. Microscopic Analysis

Figure 7a–c show the micro-morphology of RC specimens with rubber particle sizes of 0.85 mm, 1–3 mm, and 3–6 mm after 120 dry–wet cycles in a sulfate solution environment. Figure 7d shows the micro-morphology of NC specimens after 120 dry–wet cycles. As shown in Figure 7a,b, there are a small number of cracks and local micro-pores in the sample, and there are a large number of clusters of ettringite and plate-column gypsum and other expansions to fill the gap cracks. The high elasticity of rubber particles alleviates the damage caused by dry–wet cycle and sulfate attack, and the interior is denser. As shown in Figure 7c, the larger holes and cracks, larger particle size rubber and cement matrix interface transition zone are weak, and cracks develop easily. As shown in Figure 7d, the cracks and voids in NC are more obvious, and the damage to the specimen is more serious. The expansion stress generated by cement hydration products (C-S-H) and expansion products such as ettringite and gypsum is far greater than the tensile strength inside NC. The cracks develop and penetrate, and the internal structure is further damaged, which can be reflected from the micro level to the macro level, that is, the compressive strength is significantly reduced.
Through microscopic mechanism analysis, it is found that the larger the rubber particle size, the more serious the concrete damage. In order to more intuitively reflect the internal damage of the samples at different cycles, the SEM images of the samples with a rubber particle size of 3–6 mm in different dry–wet cycle stages were selected. Figure 8a,b show SEM images of rubber particle size of 3–6 mm in 60 and 120 sulfate attack dry–wet cycles.
As shown in Figure 8a, after 60 dry–wet cycles, a large number of products such as ettringite generated by sodium sulfate erosion appear inside the sample, which are flocculent and plate-like distributed in microcracks, excessive weak areas of the interface, etc., filling internal voids and cracks, improving the compactness of the specimen, and effectively improving the corrosion resistance and durability of the specimen. Figure 8b shows the microstructure of RC after 120 dry–wet cycles. With the increase in dry–wet cycles, more expansions are produced. The high elasticity of rubber particles can no longer alleviate the expansion stress caused by expansions and the damage caused by dry–wet cycles. Due to the large particle size of rubber particles, the defects in the transition zone between rubber and cement are more prominent, which is easy to develop through cracks and accelerate the destruction of concrete samples.

4. Conclusions

Based on the comparative analysis of apparent morphology, mass loss, relative dynamic elastic modulus, compressive strength loss, deterioration degree after cyclic loading and internal microstructure of ordinary concrete (NC) and rubberized concrete (RC) under 120 sulfate attack and dry–wet cycle coupling, the main conclusions are as follows:
(1)
Adding appropriate rubber particles into concrete, the mechanical properties decreased compared with NC, but its corrosion resistance and durability were significantly improved. RC with a particle size of 0.85 mm was the best. After 120 dry–wet cycles, the relative compressive strength of RC with a particle size of 0.85 mm was 26.2% higher than that of ordinary concrete.
(2)
With the increase in dry–wet cycles, the surface damage and mass loss of the specimens were more serious, and the deterioration degree of the relative dynamic elastic modulus and compressive strength was significantly optimized compared with NC, indicating that the incorporation of rubber effectively improved the durability of concrete. The maximum mass relative value of the sample with a rubber particle size of 0.85 mm, 1–3 mm, and 3–6 mm is 0.66%, 1.24%, and 2.06% lower than that after 120 dry–wet cycles. The smaller the rubber particle size is, the better the impermeability is, and the smaller the mass loss rate is.
(3)
After cyclic loading, the deterioration degree of ordinary concrete is greater than that of rubber concrete. The high elasticity of rubber effectively alleviates the fatigue damage caused by cyclic loading and inhibits the generation of cracks. The smaller the rubber particle size, the smaller the deterioration coefficient and the smaller the fatigue damage. After cyclic loading, the deterioration degree of concrete with a 0.85 mm rubber particle size was 5.1% lower than that of ordinary concrete.
(4)
After 120 days of dry–wet cycle of sulfate attack, there are many pore cracks in the sample. The smaller the rubber particle size, the smaller the internal damage. In the early stage of erosion, the expansion of ettringite and gypsum filled the internal cracks, improved the compactness of the sample, and effectively increased the compressive strength of the sample. With the increase in erosion time, more expansion was produced, and the internal cracks of the sample gradually developed through the occurrence of damage.

Author Contributions

Data curation, H.W.; formal analysis, H.W.; funding acquisition, J.P.; project administration, J.P.; writing—original draft, H.W.; writing—review and editing, J.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

References

  1. Ataei, H. Experimental Study of Rubber Tire Aggregates Effect on Compressive and Dynamic Load-Bearing Properties of Cylindrical Concrete Specimens. J. Mater. Cycles Waste Manag. 2016, 18, 665–676. [Google Scholar] [CrossRef]
  2. Saleh, T.A.; Danmaliki, G.I. Adsorptive Desulfurization of Dibenzothiophene from Fuels by Rubber Tyres-Derived Carbons: Kinetics and Isotherms Evaluation. Process Saf. Environ. Prot. 2016, 102, 9–19. [Google Scholar] [CrossRef]
  3. Akasaki, J.; Fioriti, C.; Queiroz, R.; Fugii, A.; Pinheiro, J. Performance of Simple Concrete Pipes Produced with the Incorporation of Rubber Tires. Rev. Ing. Constr. 2016, 31, 27–36. [Google Scholar] [CrossRef] [Green Version]
  4. Gao, Y.; Wang, B.; Liu, C.; Hui, D.; Xu, Q.; Zhao, Q.; Qin, Y.; Dong, W. Experimental Investigation on Static Compressive Toughness of Steel Fiber Rubber Concrete. Rev. Adv. Mater. Sci. 2022, 61, 576–586. [Google Scholar] [CrossRef]
  5. Alshaikh, I.M.H.; Abu Bakar, B.H.; Alwesabi, E.A.H.; Akil, H.M. Progressive Collapse of Reinforced Rubberised Concrete: Experimental Study. Constr. Build. Mater. 2019, 226, 307–316. [Google Scholar] [CrossRef]
  6. Wang, Z.; Hu, H.; Hajirasouliha, I.; Guadagnini, M.; Pilakoutas, K. Tensile Stress-Strain Characteristics of Rubberised Concrete from Flexural Tests. Constr. Build. Mater. 2020, 236, 117591. [Google Scholar] [CrossRef]
  7. Feng, L.Y.; Chen, A.J.; Liu, H.D. Effect of Waste Tire Rubber Particles on Concrete Abrasion Resistance Under High-Speed Water Flow. Int. J. Concr. Struct. Mater. 2021, 15, 37. [Google Scholar] [CrossRef]
  8. Luo, T.; Zhang, C.; Sun, C.; Zheng, X.; Ji, Y.; Yuan, X. Experimental Investigation on the Freeze-Thaw Resistance of Steel Fibers Reinforced Rubber Concrete. Materials 2020, 13, 1260. [Google Scholar] [CrossRef] [Green Version]
  9. Xie, Y.; Su, X.R.; Wang, H.X.; Luo, D.M.; Zhou, Y.L. Experimental Analysis of the Toughness Mechanism of Rubber Concrete. IOP Conf. Ser. Mater. Sci. Eng. 2019, 504, 012041. [Google Scholar] [CrossRef]
  10. Ismail, M.K.; Hassan, A.A.A. Impact Resistance and Mechanical Properties of Self-Consolidating Rubberized Concrete Reinforced with Steel Fibers. J. Mater. Civ. Eng. 2017, 29, 04016193. [Google Scholar] [CrossRef]
  11. Liu, H.; Wang, X.; Jiao, Y.; Sha, T. Experimental Investigation of the Mechanical and Durability Properties of Crumb Rubber Concrete. Materials 2016, 9, 172. [Google Scholar] [CrossRef] [Green Version]
  12. Youssf, O.; Hassanli, R.; Mills, J.E. Mechanical Performance of FRP-Confined and Unconfined Crumb Rubber Concrete Containing High Rubber Content. J. Build. Eng. 2017, 11, 115–126. [Google Scholar] [CrossRef]
  13. Wang, J.; Dai, Q.; Si, R.; Guo, S. Mechanical, Durability, and Microstructural Properties of Macro Synthetic Polypropylene (PP) Fiber-Reinforced Rubber Concrete. J. Clean. Prod. 2019, 234, 1351–1364. [Google Scholar] [CrossRef]
  14. Zhang, W.; Ma, J.; Tang, L. Experimental Study on Shear Strength Characteristics of Sulfate Saline Soil in Ningxia Region under Long-Term Freeze-Thaw Cycles. Cold Reg. Sci. Technol. 2019, 160, 48–57. [Google Scholar] [CrossRef]
  15. Chegenizadeh, A.; Keramatikerman, M.; Afzal, F.; Nikraz, H.; Lau, C.K. An Investigation into Performance of Cement-Stabilized Kaolinite Clay with Recycled Seashells Exposed to Sulphate. Sustainability 2020, 12, 8367. [Google Scholar] [CrossRef]
  16. Elahi, M.M.A.; Shearer, C.R.; Naser Rashid Reza, A.; Saha, A.K.; Khan, M.N.N.; Hossain, M.M.; Sarker, P.K. Improving the Sulfate Attack Resistance of Concrete by Using Supplementary Cementitious Materials (SCMs): A Review. Constr. Build. Mater. 2021, 281, 122628. [Google Scholar] [CrossRef]
  17. Kaufmann, J.; Loser, R.; Winnefeld, F.; Leemann, A. Sulfate Resistance Testing of Shotcrete—Sample Preparation in the Field and under Laboratory Conditions. Constr. Build. Mater. 2021, 276, 122233. [Google Scholar] [CrossRef]
  18. Viswanadha Varma, D.; Rama Rao, G.V.; Markandeya Raju, P.; Pavan Kumar, M. Compressive Strength and Durability of Metakaolin Blended Concrete Exposed to Acid and Sulphate Attack. IOP Conf. Ser. Mater. Sci. Eng. 2021, 1025, 012004. [Google Scholar] [CrossRef]
  19. Diaconu, L.I.; Rujanu, M.; Diaconu, A.C.; Erbǎnoiu, A.A.; Babor, D.T.; Plian, D. Improvement of the Concrete Behaviour to Sulphate Corrosion Using Fly Ash Admixture Collected by Wet Process. IOP Conf. Ser. Mater. Sci. Eng. 2020, 789, 012018. [Google Scholar] [CrossRef]
  20. Ghafoori, N.; Batilov, I.; Najimi, M. Resistance to Sulfate Attack of Mortars Containing Colloidal Nanosilica and Silica Fume. J. Mater. Civ. Eng. 2020, 32, 06020019. [Google Scholar] [CrossRef]
  21. Zhang, Z.; Zhou, J.; Yang, J.; Zou, Y.; Wang, Z. Understanding of the Deterioration Characteristic of Concrete Exposed to External Sulfate Attack: Insight into Mesoscopic Pore Structures. Constr. Build. Mater. 2020, 260, 119932. [Google Scholar] [CrossRef]
  22. Liu, F.; You, Z.; Xiong, R.; Yang, X. Effects of Sodium Sulfate Attack on Concrete Incorporated with Drying-Wetting Cycles. Adv. Civ. Eng. 2021, 2021, 5393504. [Google Scholar] [CrossRef]
  23. Wei, Y.; Chai, J.; Qin, Y.; Li, Y.; Xu, Z.; Li, Y.; Ma, Y. Effect of Fly Ash on Mechanical Properties and Microstructure of Cellulose Fiber-Reinforced Concrete under Sulfate Dry–Wet Cycle Attack. Constr. Build. Mater. 2021, 302, 124207. [Google Scholar] [CrossRef]
  24. Gao, J.; Yu, Z.; Song, L.; Wang, T.; Wei, S. Durability of Concrete Exposed to Sulfate Attack under Flexural Loading and Drying-Wetting Cycles. Constr. Build. Mater. 2013, 39, 33–38. [Google Scholar] [CrossRef]
  25. Wu, R.; Zou, M.; Liu, J.; Zhang, G.; Zhang, Y. Experimental Study on Sulfate Wetting–Drying Cycle of Metal Tailings Powder Concrete. Front. Mater. 2022, 9, 86. [Google Scholar] [CrossRef]
  26. Tian, W.; Han, N. Experiment Analysis of Concrete’s Mechanical Property Deterioration Suffered Sulfate Attack and Drying-Wetting Cycles. Adv. Mater. Sci. Eng. 2017, 2017, 5673985. [Google Scholar] [CrossRef] [Green Version]
  27. Guo, J.J.; Wang, K.; Guo, T.; Yang, Z.Y.; Zhang, P. Effect of Dry-Wet Ratio on Properties of Concrete under Sulfate Attack. Materials 2019, 12, 2755. [Google Scholar] [CrossRef] [Green Version]
  28. Jiang, L.; Niu, D. Damage Evolution of Concrete Exposed to Sulfate Attack Under Drying-Wetting Cycles. Open Constr. Build. Technol. J. 2015, 8, 444–449. [Google Scholar] [CrossRef] [Green Version]
  29. He, P.; Yu, J.; Wan, Y.; Wang, R.; Han, X.; Gu, S.; Liu, Q. Effect of Ion Chelator on Microstructure and Properties of Cement-Based Materials under Sulfate Dry-Wet Cycle Attack. Constr. Build. Mater. 2020, 257, 119527. [Google Scholar] [CrossRef]
  30. Tran, N.L.; Deutscher, M.; Scheerer, S. An Investigation of the Heat Generated during Cyclic Loading of Ultra-high Performance Concrete. PAMM 2019, 19, e201900469. [Google Scholar] [CrossRef] [Green Version]
  31. Moharrami, M.; Koutromanos, I. Triaxial Constitutive Model for Concrete under Cyclic Loading. J. Struct. Eng. 2016, 142, 04016039. [Google Scholar] [CrossRef]
  32. Monnamitheen Abdul Gafoor, A.H.; Dinkler, D. A Macroscopic Gradient-Enhanced Damage Model for Deformation Behavior of Concrete under Cyclic Loadings. Arch. Appl. Mech. 2020, 90, 1179–1199. [Google Scholar] [CrossRef] [Green Version]
  33. Boobalan, S.C.; Salman Shereef, M.; Saravanaboopathi, P.; Siranjeevi, K. Studies on Green Concrete—A Review. Mater. Today Proc. 2022, 65, 1404–1409. [Google Scholar] [CrossRef]
  34. Błaszczyński, T.; Król, M. Usage of Green Concrete Technology in Civil Engineering. Procedia Eng. 2015, 122, 296–301. [Google Scholar] [CrossRef] [Green Version]
  35. Rhim, H.C.; Kim, D.Y.; Cho, C.S.; Kim, D.H. Effect of Steel Plates on Estimation of the Compressive Strength of Concrete via Ultrasonic Testing. Materials 2020, 13, 887. [Google Scholar] [CrossRef] [Green Version]
  36. Gong, J.; Deng, G.; Shan, B. Performance Evaluation of RPC Exposed to High Temperature Combining Ultrasonic Test: A Case Study. Constr. Build. Mater. 2017, 157, 194–202. [Google Scholar] [CrossRef]
  37. Zhao, G.; Li, J.; Shao, W. Effect of Mixed Chlorides on the Degradation and Sulfate Diffusion of Cast-in-Situ Concrete Due to Sulfate Attack. Constr. Build. Mater. 2018, 181, 49–58. [Google Scholar] [CrossRef]
  38. Liu, P.; Chen, Y.; Yu, Z.; Lu, Z. Effect of Sulfate Solution Concentration on the Deterioration Mechanism and Physical Properties of Concrete. Constr. Build. Mater. 2019, 227, 116641. [Google Scholar] [CrossRef]
  39. Lee, J.; Lee, T. Durability and Engineering Performance Evaluation of CaO Content and Ratio of Binary Blended Concrete Containing Ground Granulated Blast-Furnace Slag. Appl. Sci. 2020, 10, 2504. [Google Scholar] [CrossRef] [Green Version]
  40. Lee, J.; Lee, T.; Jeong, J.; Jeong, J. Engineering, Durability, and Sustainability Properties Analysis of High-Volume, PCC Ash-Based Concrete. Sustainability 2020, 12, 3520. [Google Scholar] [CrossRef]
  41. Yao, W.; Bai, M.; Pang, J.; Liu, T. Performance Degradation and Damage Model of Rice Husk Ash Concrete under Dry–Wet Cycles of Sulfate Environment. Environ. Sci. Pollut. Res. 2022, 29, 59173–59189. [Google Scholar] [CrossRef] [PubMed]
  42. Pacheco-Torres, R.; Cerro-Prada, E.; Escolano, F.; Varela, F. Fatigue Performance of Waste Rubber Concrete for Rigid Road Pavements. Constr. Build. Mater. 2018, 176, 539–548. [Google Scholar] [CrossRef]
  43. Liu, M.; Lu, J.; Jiang, W.; Ming, P. Study on Fatigue Damage and Fatigue Crack Propagation of Rubber Concrete. J. Build. Eng. 2023, 65, 105718. [Google Scholar] [CrossRef]
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Figure 1. Apparent phenomenon of RC with different rubber particle sizes after dry–wet cycle; (a) 90 dry–wet cycles; (b) 120 dry–wet cycles.
Figure 1. Apparent phenomenon of RC with different rubber particle sizes after dry–wet cycle; (a) 90 dry–wet cycles; (b) 120 dry–wet cycles.
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Figure 2. The relationship between the number of dry–wet cycles of concrete specimens and the relative mass value Km(%).
Figure 2. The relationship between the number of dry–wet cycles of concrete specimens and the relative mass value Km(%).
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Figure 3. The relationship between dry–wet cycles and relative dynamic elastic modulus Edr(%) of concrete block.
Figure 3. The relationship between dry–wet cycles and relative dynamic elastic modulus Edr(%) of concrete block.
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Figure 4. (a) Electronic creep relaxation tester; (b) specimen damage pattern.
Figure 4. (a) Electronic creep relaxation tester; (b) specimen damage pattern.
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Figure 5. Relationship between dry–wet cycles and relative compressive strength of concrete specimens Kf.
Figure 5. Relationship between dry–wet cycles and relative compressive strength of concrete specimens Kf.
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Figure 6. The relationship between uniaxial compressive strength and fatigue failure strength P(%) of concrete specimens under different dry–wet cycles.
Figure 6. The relationship between uniaxial compressive strength and fatigue failure strength P(%) of concrete specimens under different dry–wet cycles.
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Figure 7. Micromorphology of concrete specimens under 120 wetting–drying cycles. (a) RC-0.85; (b) RC-1-3; (c) RC-3-6; (d) NC.
Figure 7. Micromorphology of concrete specimens under 120 wetting–drying cycles. (a) RC-0.85; (b) RC-1-3; (c) RC-3-6; (d) NC.
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Figure 8. Microstructure of concrete with rubber particle size of 3–6 mm in each stage of dry–wet cycle; (a) 60 dry–wet cycles; (b) 120 dry–wet cycles.
Figure 8. Microstructure of concrete with rubber particle size of 3–6 mm in each stage of dry–wet cycle; (a) 60 dry–wet cycles; (b) 120 dry–wet cycles.
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Table
Table 1. Chemical composition of cementin material.
Table 1. Chemical composition of cementin material.
ComponentCaOSiO2Fe2O3MgOAl2O3Na2OSO3Ignition Loss
content/%cement63.1122.604.381.465.03-2.241.18
fly ash2.4553.214.090.3934.751.92-4.05
Table
Table 2. Chemical composition of rubber particles.
Table 2. Chemical composition of rubber particles.
Ultimate CompositionSSiZnCO
content/%2.860.111.6392.193.23
Table
Table 3. Rubber particle parameter index.
Table 3. Rubber particle parameter index.
Rubber Particle Size/mmBreaking Strength/MPaBreaking Elongation/%Iron Content/%Fiber Content/%Heating Loss/%Ash Content/%Sieve Residue/%
0.8517.25840.0200.588.450.012
1–3
3–6
Table
Table 4. Rubber concrete mixture ratio/(kg·m−3).
Table 4. Rubber concrete mixture ratio/(kg·m−3).
Concrete NumberCementing MaterialFine AggregateGravelWaterWater Reducer
CementFly AshSandRubber
RC-0.8533043680.637.311211533.5
RC-1-333043678.837.311211533.5
RC-3-633043675.237.311211533.5
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Wang, H.; Pang, J. Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle. Sustainability 2023, 15, 9569. https://doi.org/10.3390/su15129569

AMA Style

Wang H, Pang J. Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle. Sustainability. 2023; 15(12):9569. https://doi.org/10.3390/su15129569

Chicago/Turabian Style

Wang, Heng, and Jianyong Pang. 2023. "Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle" Sustainability 15, no. 12: 9569. https://doi.org/10.3390/su15129569

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