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A Survey Paper on Enhancing Properties and Economy in Self-Healing Concrete Prof. P. V. Kapure1, K. M. Katare2 1Lecturer in Department of Civil Engineering, AISSMS Polytechnic, Pune, Maharashtra, India 2Student of Final Year Diploma in Civil Engineering, AISSMS Polytechnic, Pune, Maharashtra, India

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Abstract - Concrete cracking can reduce durability and

generation method, and evaluation criteria make direct comparison of their performance difficult. In the present study, sodium silicate is selected as the primary chemical healing agent because its silicate species can participate in reactions with calcium-bearing phases and contribute to the formation of healing products within cracks. Crystalline admixture is incorporated as a supporting healing material because its moisture-activated action can promote the formation of insoluble crystalline products that contribute to crack sealing. Silica fume is used as a supplementary cementitious material because it is very fine and reactive particles can refine the pore structure, densify the cementitious matrix, and support compressive-strength development. A PCE-based superplasticizer is used to improve workability while maintaining a controlled water-to-binder ratio. Thus, each material has a specific function in the proposed concrete system rather than being used only for increasing the number of additives. The five research studies considered in this work indicate that existing investigations have mainly focused on individual healing mechanisms, particularly bacterial systems, while comparatively limited attention has been given to a simple chemical healing system evaluated using a consistent methodology. The literature also shows variations in concrete grades, crack widths, healing conditions and testing procedures, with comparatively less emphasis on quantitative compressivestrength recovery. Therefore, this study investigates M20, M25 and M30 concrete incorporating silica fume and crystalline admixture, with sodium silicate used as the principal post-cracking healing treatment. A common experimental procedure is adopted for the three concrete grades, including controlled cracking, healing and compressive-strength evaluation before cracking, after cracking, and after healing. The study aims to determine the influence of concrete grade and the proposed healing system on strength recovery and crack-healing performance, thereby addressing the identified gaps through a simple and practically achievable experimental methodology.

service life by allowing the ingress of water and other aggressive agents. Self-healing concrete offers a potential solution by enabling cracked concrete to partially restore its properties. The present study investigates a simplified selfhealing concrete system using sodium silicate as the primary chemical healing agent, crystalline admixture as a supporting healing component, and silica fume for matrix densification and strength improvement. A PCE-based super-plasticizer is used to maintain workability while controlling the water-to-binder ratio. M20, M25 and M30 concrete grades are investigated using a common experimental procedure. Controlled cracking is introduced after curing, followed by sodium-silicate treatment and a specified healing period. Compressive strength is evaluated before cracking, after cracking, and after healing to determine the percentage strength recovery. The study aims to address gaps in previous research by using a consistent methodology and quantitatively evaluating mechanical recovery across different concrete grades, providing a simple and practical approach to self-healing concrete. Key Words: Self-healing concrete, Sodium silicate, Crystalline admixture, Silica fume, Super-plasticizer, Strength recovery, M20, M25, M30.

1. INTRODUCTION Concrete is one of the most widely used construction materials because of its high compressive strength, durability, availability, and economical nature. However, cracking is an inherent problem in concrete and may occur due to drying shrinkage, thermal variations, mechanical loading, inadequate curing, and environmental exposure. Even relatively small cracks can provide pathways for water and aggressive agents, which may accelerate deterioration and reduce the service life of concrete structures. Conventional crack-repair techniques such as sealing, grouting, and injection require external intervention and may become difficult when cracks repeatedly occur or are located in inaccessible regions. This has led to increasing interest in self-healing concrete, which can partially restore its properties after cracking through autogenous or autonomous healing mechanisms. Previous studies have investigated bacterial, chemical, mineral and polymer-based approaches; however, differences in concrete grade, healing procedure, crack-

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2. LITERATURE REVIEW Self-healing concrete has been investigated as an approach for reducing the effects of cracking and improving the durability and service life of concrete structures. The reviewed studies mainly investigate biological self-healing,

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particularly bacterial systems, and demonstrate the potential of such systems to reduce crack width and improve concrete performance. However, differences in concrete grade, healing conditions, crack-generation procedures and evaluation methods indicate the need for a simpler and more consistent experimental approach. Meera and Vishnudas (2025) investigated the mechanical and micro-structural behavior of bacterial and twocomponent bacterial concrete and evaluated their selfhealing capability. Their study demonstrated the potential of bacterial systems for crack healing and improvement in concrete performance, while micro-structural observations supported the formation of healing products. However, the study mainly concentrated on bacterial systems, with comparatively less emphasis on a simple chemical healing system and systematic comparison of strength recovery across different concrete grades. Adil et al. (2024) investigated the ability of Bacillus subtilis to heal cracks and improve the performance of concrete after cracking. The study demonstrated that bacterial activity contributed to crack closure and showed the potential of biological self-healing concrete. However, biological healing involves additional considerations such as bacterial viability and nutrient availability. Therefore, the study indicates the need for investigating comparatively simpler chemical healing approaches for practical concrete applications. Vishal, Chepuri et al. (2025) experimentally investigated bacteria-based self-healing concrete and evaluated the effect of bacterial action on cracked concrete. Their findings indicated that bacterial concrete could reduce crack width and improve concrete properties after the healing period. However, differences in concrete grade, crack-generation procedures and testing methodology limit direct comparison with other studies. A common experimental methodology and systematic evaluation of strength recovery are therefore required. Joshi and Rai (2018) investigated the selfhealing characteristics of concrete using Bacillus subtilis and examined factors affecting crack-healing performance. The study demonstrated the potential of self-healing mechanisms for reducing the effects of cracking, and the reviewed manuscript reports approximately 65–70% recovery of original strength after 30–40 days of selfhealing in the investigated bacterial specimens. However, greater emphasis was identified as necessary on quantitative post-healing mechanical recovery and comparison between different concrete grades using a common healing system. Meghashree et al. (2025) investigated self-healing behavior and evaluated the effectiveness of a healing technique in improving concrete performance. The investigated approach showed potential for reducing the effects of cracking and improving concrete durability and performance. However, the study identified the need for further systematic investigation using a comparatively simple chemical healing system and quantitative compressive-strength recovery across M20, M25 and M30 concrete grades.

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Table -1: Summary of Literature Review and Identified Research Gaps

S Title of Author Aim/ r Research and Year Objective . Paper N o

Major Findings / Conclusi on

Research Gap

1 Mechanica l and Microstruc tural Evaluation of Bacterial and TwoComponen t Bacterial Concretes

Meera and Vishnuda s (2025)

To evaluate the mechanica l and microstructural behavior of bacterial and twocomponen t bacterial concrete and investigate their selfhealing capability.

Bacterial systems demonstr ated potential for crack healing and improve ment in concrete performa nce. Microstructural observati ons supporte d the formation of healing products.

Mainly focuses on bacterial systems; comparat ively less emphasis on a simple chemical healing system combined with strengthenhancin g matrix modificat ion.

2 Investigati Adil et al. on on (2024) SelfHealing Concrete Using Bacillus subtilis Bacteria

To investigate the ability of Bacillus subtilis to heal cracks and improve the performan ce of concrete after cracking.

Bacterial activity contribut ed to crack closure and demonstr ated the potential of biological selfhealing concrete.

Biological healing requires considera tions such as bacterial viability and nutrient availabilit y; a simpler chemical healing approach requires further investigat ion.

3 Bacterial SelfHealing Concrete / Related

To investigate bacterial selfhealing

Bacterial concrete showed potential for

Differenc es in concrete grade, crack-

Vishal, Chepuri et al. (2025)

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Bacterial Healing Study

behavior and evaluate the effect of bacterial action on cracked concrete.

4 SelfJoshi and Healing Rai Concrete: (2018). Related Investigati on

To study the selfhealing characteri stics of concrete and the factors affecting crackhealing performan ce.

reducing crack width and improvin g propertie s after the healing period.

generatio n procedur e and testing methodol ogy limit direct comparis on; a common methodol ogy for quantitati ve strength recovery is required.

Selfhealing mechanis ms demonstr ated potential for reducing crack effects.

Greater emphasis is required on quantitati ve posthealing mechanic al recovery and comparis on across concrete grades using a common healing system.

5 SelfMeghashr To The Healing ee et al. investigate investigat Concrete: (2025) selfed Recent healing approach Investigati behavior showed on and potential evaluate for the reducing effectivene crack ss of a effects healing and technique improvin in g improving concrete concrete durability performan /perform ce ance.

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recovery across M20, M25 and M30 grades. 2.1. Research Gap The reviewed studies demonstrate the potential of selfhealing concrete, particularly bacterial systems, for reducing crack effects and improving concrete performance. However, limited attention has been given to simple chemical healing systems that can be practically implemented in conventional concrete. Variations in concrete grades, crack-generation procedures, healing conditions, healing periods, and testing methods also make direct comparison between existing studies difficult. Furthermore, visual crack closure alone does not necessarily indicate recovery of the mechanical capacity of cracked concrete. Therefore, greater emphasis is required on quantitative post-healing compressive-strength recovery using a common experimental methodology across different concrete grades. Accordingly, the present study addresses these gaps by investigating a simple chemical self-healing system using sodium silicate as the primary healing agent, supported by crystalline admixture, while silica fume is incorporated to improve matrix density and strength development. The study considers M20, M25, and M30 concrete grades and applies a common procedure involving controlled cracking, healing treatment, and compressive-strength evaluation. The percentage recovery of compressive strength is used as the principal quantitative measure of healing performance. This approach aims to provide a practical and consistent framework for evaluating self-healing performance across different concrete grades.

3. AIMS AND OBJECTIVES

Further systemati c investigat ion is required using a simple chemical healing system with quantitati ve compress ivestrength

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The present study is focused on evaluating a simple chemical self-healing concrete system using sodium silicate as the primary healing agent, supported by crystalline admixture and silica fume. The study considers M20, M25 and M30 concrete grades and evaluates their self-healing performance through controlled cracking and compressive-strength recovery. 3.1. Aims   

To investigate the self-healing performance of M20, M25 and M30 grade concrete. To evaluate the recovery of compressive strength after controlled cracking and healing. To study the influence of concrete grade on the healing performance.

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3.2. Objectives 



To add and prepare M20, M25 and M30 concrete mixes incorporating/ using sodium silicate as the primary chemical healing agent, silica fume, crystalline admixture and PCE-based superplasticize to improve workability while maintaining a controlled water-to-binder ratio during concrete production

To investigate the effectiveness of sodium silicate as the primary chemical healing agent for sealing controlled cracks and improving the mechanical properties with percentage recovery of crack.

The experimental program was designed to investigate the self-healing performance of M20, M25 and M30 concrete using sodium silicate as the primary chemical healing agent. Crystalline admixture was incorporated as a supporting healing component, while silica fume was used to improve matrix density and compressive strength. PCEbased super-plasticizer was used to maintain workability at a controlled water-to-binder ratio.

To calculate and compare the percentage recovery of compressive strength after healing and evaluate the influence of concrete grade on the self-healing performance.

Identified Research Gap Previous studies mainly focused on bacterial selfhealing systems.

Different studies used different concrete grades and methodologies, making comparison difficult. Many studies emphasize visual crack closure as an indication of healing. Limited comparison of healing performance across different concrete grades using one healing system. Different crackgeneration and healing

defined and consistent healing period for the specimens. The present study compares pre-cracking, post-cracking and post-healing compressive strength and calculates the percentage strength recovery to quantitatively assess healing performance.

4. METHODOLOGY

Table -2: How the Present Study Fills the Research Gaps SR. no. 1

procedures make results difficult to compare. Mechanical recovery after cracking and healing is not consistently evaluated.

How are practical work fills the Gaps The present study investigates a simple chemical self-healing system using sodium silicate as the primary healing agent, supported by crystalline admixture and silica fume, with super-plasticizer for workability control. The present study uses a common experimental methodology for M20, M25 and M30 concrete grades to enable systematic comparison.

4.1 Materials The materials used were OPC 53 grade cement, fine aggregate, 20 mm coarse aggregate, silica fume, crystalline admixture, sodium silicate solution, PCE-based superplasticizer and water.

The present study quantitatively evaluates compressive-strength recovery before cracking, after cracking and after the healing period. The present study compares the healing performance of M20, M25 and M30 concrete under the same healing conditions and using the same sodium-silicate-based healing system.



Silica fume: 5% of cementitious material for matrix densification and strength improvement.



Crystalline admixture: 0.5% of cementitious material as a supporting moisture-activated healing component.



Sodium silicate: primary chemical healing agent applied to controlled cracks after pre-cracking.



PCE super-plasticizer: used to improve workability while maintaining the selected waterto-binder ratio.

4.2 Mix Design M20, M25 and M30 concrete mixes were prepared using the absolute-volume method as per IS 10262:2019. The same material system and general procedure were followed for all three grades to enable comparison.

The present study uses a controlled cracking procedure followed by a

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5. RESULTS AND DISCUSSION

Table -3: Mix design (Preliminary values to be verified by laboratory trial mixes) Parameter to add By weight Silica fume Crystalline admixture Water/binder ratio Sodium silica (Postcracking)

M20

M25

M30

0.78% 0.08%

0.87% 0.09%

0.97 % 0.10%

≈0.50

≈0.45

≈0.40

1.0%

The results are evaluated to determine the effect of the proposed self-healing system on M20, M25 and M30 concrete. Compressive strength before cracking, after controlled cracking and after the healing period is considered to assess the mechanical recovery and compare the healing performance of the three concrete grades. 5.1. Results Expected Compressive Strength:The expected compressive-strength results for M20, M25 and M30 concrete are presented in Table 4. The original compressive strength is expected to increase with the concrete grade, while controlled cracking is expected to cause a reduction in strength for all three grades. After the healing period, the sodium-silicate-treated specimens are expected to recover a significant portion of the lost compressive strength. This recovery is primarily attributed to the action of sodium silicate as the main chemical healing agent, with crystalline admixture providing a supporting moisture-activated healing mechanism. The incorporation of silica fume is expected to contribute to matrix densification and improved strength development.

4.3 Casting and Curing The cement, silica fume and crystalline admixture were dry-mixed with the aggregates. Water containing the required PCE super-plasticizer was then added gradually and the concrete was mixed until uniform. The concrete was cast into 150 mm cube moulds, compacted properly and label. After de-moulding, the specimens were watercured, with 28 days adopted as the principal curing age. 4.4 Controlled Cracking and Healing After curing, controlled hairline cracks were introduced using a compression-testing machine. Loading was stopped immediately after the desired crack formation without completely crushing the specimen.

Table -4: Expected compressive-strength results

Sodium silicate was then applied directly to the crack as the primary healing treatment. The specimens were maintained under the same controlled healing condition for the specified healing period. Crack-width observations were recorded where possible. 4.5. Compressive Strength and Strength Recovery Compressive strength was evaluated at three stages:   

The results for M20, M25 and M30 were compared to evaluate the influence of concrete grade on self-healing performance.

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Cracked Strength (MPa)

M20 M25 M30

24.0 30.0 36.0

17.0 21.5 26.0

Expected Posthealing Strength (MPa) 21.8 27.8 33.0

The expected compressive-strength recovery values for M20, M25 and M30 concrete are presented in Table 5. The proposed healing system is expected to restore a considerable portion of the compressive strength lost after controlled cracking. The recovery is attributed mainly to the sodium-silicate treatment, supported by the crystalline admixture and the dense cementitious matrix provided by silica fume. The percentage strength recovery is calculated by comparing the strength lost during cracking with the strength regained after the healing period. The expected results indicate that the proposed system has the potential to provide measurable mechanical recovery across all three concrete grades. These values are provisional expected values and will be replaced by the actual experimental results after cube casting and testing.

The percentage strength recovery was calculated using

Original Strength (MPa)

Expected Compressive Strength recovery:-

Before cracking After controlled cracking After healing

Concrete Grade

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Table -5: Expected Compressive-Strength Recovery:Concrete Grade

Original Strength (MPa)

Cracked Strength (MPa)

M20 M25 M30

24.0 30.0 36.0

17.0 21.5 26.0

Expected Posthealing Strength (MPa) 21.8 27.8 33.0

values obtained from cube casting and testing. The numerical values currently presented in Tables 4 and 5 are expected values and should not be considered measured experimental results.

Expected Strength Recovery (%) 68.6% 74.1% 70.0%

5.2. Discussion The expected results indicate that controlled cracking is likely to reduce the compressive strength of M20, M25 and M30 concrete. After the healing period, the sodiumsilicate-treated specimens are expected to recover a significant portion of the strength lost during cracking. The expected recovery suggests that the proposed chemical healing system can contribute to restoration of the damaged cementitious matrix.

Chart-1: Expected compressive Strength Graph

The healing performance is expected to result primarily from sodium silicate, which acts as the main chemical healing agent and can contribute to the formation of healing products within the cracked region. The crystalline admixture provides a supporting moisture-activated mechanism that may promote additional crystalline products in cracks and pores. The combined action of these materials is expected to improve crack sealing and mechanical recovery compared with the cracked condition.

Chart-2: Expected compressive Strength recovery Graph

6. CONCLUSIONS

The incorporation of silica fume is expected to improve the density and compactness of the cementitious matrix because of its fine particle size and pozzolanic activity. This may contribute to higher initial compressive strength and provide a relatively dense matrix for the healing process. The PCE-based super-plasticizer supports the required workability while maintaining the selected water-to-binder ratio.

The present study proposes a simple and practical selfhealing concrete system for M20, M25 and M30 grades using sodium silicate as the primary chemical healing agent, crystalline admixture as a supporting healing component, and silica fume for matrix densification and strength improvement. PCE-based super-plasticizer is used to maintain suitable workability while controlling the water-to-binder ratio.

The comparison of M20, M25 and M30 is expected to show that concrete grade influences both initial strength and post-healing performance. However, a higher concrete grade cannot be assumed to provide a proportionally higher percentage of strength recovery, since healing performance also depends on crack characteristics, moisture availability, healing-agent penetration and the condition of the cementitious matrix.

The proposed methodology uses a common procedure involving concrete casting, curing, controlled crack formation, sodium-silicate treatment and subsequent healing. Compressive strength before cracking, after cracking and after healing is considered as the principal parameter for evaluating the effectiveness of the healing system.

Overall, the proposed system provides a simple and practical approach to self-healing concrete by combining a primary chemical healing agent with a supporting crystalline mechanism and a strength-supporting silicafume-modified matrix. The final discussion and conclusions will be updated using the actual experimental

The expected results indicate that the proposed system can recover a considerable portion of the compressive strength lost due to controlled cracking. The combined action of sodium silicate and crystalline admixture is expected to promote healing within the cracked region, while silica fume is expected to contribute to a denser and stronger cementitious matrix.

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The comparison of M20, M25 and M30 concrete is expected to provide an understanding of the influence of concrete grade on strength recovery under similar healing conditions. The study therefore provides a comparatively simple experimental approach for investigating chemical self-healing concrete and addressing the research gaps identified from the reviewed literature.

Author 2: K.M. Katare is a 3rd year Civil Engineering student at AISSMS Polytechnic Pune, Maharashtra. He is interested in construction materials, concrete technology and sustainable construction practices. He has worked on the study of self-healing concrete and the application of sodium silicate for improving concrete properties and economy. This research work was carried out as part of his academic project.

The numerical values presented in the present manuscript are provisional expected values and will be replaced by the actual experimental results obtained after casting, cracking, healing and compressive-strength testing.

REFERENCES [1] Joshi, R., & Rai, S. P. (2018). An Experimental Study on Self Healing of Concrete Using Bacillus subtilis in Cultured Form. International Journal of Creative Research Thoughts (IJCRT), 6(2), 1328–1332. [2] Adil, M. R., Khatun, S., Jamal, M., & Mondal, A. (2024). Investigation on Self-Healing Concrete Using Bacillus subtilis Bacteria. MATEC Web of Conferences, 400, 01002. [3] Vishal, A., Chepuri, A., & Chandana, N. (2025). Assessment of Bacteria-Based Self-Healing Concrete Through Experimental Investigations—A Sustainable Approach. Journal of Materials Science: Materials in Engineering, 20, 15. [4] Meera, C. M., & Vishnudas, S. (2025). Mechanical and Microstructural Evaluation of Bacterial and TwoComponent Bacterial Concretes. [5] Meghashree, M., Urs, N., Geetha, N. K., Tahera, & Reshma, E. K. (2025). Advancing Sustainable Concrete with Bacterial Self-Healing Technology and Kuhn-Tucker Condition. Scientific Reports, 15, 33736.

BIOGRAPHIES Author 1:Prof. P. V. Kapure is a Professor in the Department of Civil Engineering at AISSMS Polytechnic Pune, Maharashtra. He has experience in civil engineering areas such as Engineering Mechanics, Construction Materials and Design of Steel & RCC Structures etc. He has guided various academic projects and research activities. His guidance and technical knowledge contributed significantly to the completion of this survey paper.

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