A SELF-HEALING CONCRETE COMPOSITION FOR ENHANCED INFRASTRUCTURE DURABILITY

Abstract

7. ABSTRACT The present invention relates to a self-healing concrete composition (100) designed to enhance the durability of infrastructure by autonomously repairing microcracks that may occur over time. Self-healing concrete is an innovative material that possesses the ability to autonomously repair microcracks, significantly extending the lifespan of concrete structures. This technology incorporates various mechanisms, including capsule-based, bacterial, and mineral-based approaches, to enable self-repair. By integrating healing agents within the concrete matrix (102), these mechanisms are activated upon crack formation, leading to the sealing of the crack and restoration of structural integrity. The implementation of self-healing concrete offers numerous advantages, such as enhanced durability, reduced maintenance costs, and improved sustainability. By mitigating the detrimental effects of cracking, this technology can significantly prolong the service life of infrastructure, including bridges, highways, tunnels, and coastal structures, thereby reducing the frequency and cost of repairs, minimizing resource consumption, and contributing to a more sustainable built environment. The figure associated with abstract is Fig. 1.

Specification

Description:4. DESCRIPTION
Technical Field of the Invention

The present invention relates to self-healing concrete compositions. More particularly, it pertains to methods of incorporating various self-healing agents within the concrete matrix to enable autonomous repair of microcracks, thereby enhancing the durability and lifespan of concrete structures.

Background of the Invention

Concrete is one of the most widely used construction materials globally, valued for its exceptional strength, durability, and versatility. However, despite its numerous advantages, concrete is not impervious to degradation. One of the most significant challenges facing concrete structures is their susceptibility to cracking. These cracks can arise from various factors, including thermal expansion and contraction, shrinkage during curing, and exposure to environmental stresses such as freeze-thaw cycles, moisture infiltration, and chemical attacks.

Cracking poses serious risks to the structural integrity of concrete. When cracks form, they can lead to several detrimental outcomes, including water ingress, which can initiate corrosion of the embedded steel reinforcement, further weakening the structure. This degradation not only compromises the safety and performance of the infrastructure but also necessitates expensive and disruptive repair interventions.

Traditional repair methods for concrete cracks often involve manual labor and extensive downtime, which can be costly and inefficient. Techniques such as sealing, patching, and resurfacing require significant resources and can disrupt normal operations in infrastructure applications. Furthermore, these methods do not address the root cause of the cracking; they merely serve as temporary solutions.

To combat these challenges, there is an urgent need for innovative approaches that can enhance the durability and longevity of concrete. Researchers and engineers have begun exploring the concept of self-healing concrete-a technology designed to autonomously repair cracks as they occur. This groundbreaking approach leverages advanced materials science to introduce mechanisms that allow concrete to heal itself, thereby improving its resilience against environmental factors and extending its service life.

Self-healing concrete represents a significant advancement over traditional repair techniques, promising to reduce maintenance costs, enhance safety, and contribute to more sustainable construction practices. By addressing the limitations of conventional concrete repair methods, self-healing technology has the potential to revolutionize infrastructure durability and performance.

Brief Summary of the Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

It is a primary objective of the invention is to enhance the durability, longevity, and overall performance of concrete infrastructure by enabling it to autonomously repair minor cracks and damage.

It is yet another object of the invention to lower maintenance costs by enabling the concrete to self-repair, which decreases the frequency and expense of traditional repair methods.

It is yet another object of the invention to enhance the structural integrity of concrete by effectively filling cracks and preventing further damage, ensuring safety and reliability.

It is yet another object of the invention to support sustainable infrastructure by reducing the environmental impact associated with concrete production and maintenance through extended lifespan and fewer repairs.

It is yet another object of the invention to advance concrete technology by developing innovative self-healing mechanisms, promoting further research and application in the field.

According to an aspect of the present invention, a self-healing concrete represents a groundbreaking advancement in construction technology, enabling concrete structures to autonomously repair cracks and thereby significantly prolong their lifespan while reducing costly maintenance requirements. This innovative solution addresses a critical challenge in the construction industry the vulnerability of concrete to cracking, which can lead to structural degradation, reinforcement corrosion, and water ingress.

The self-healing concrete composition is characterized by several key benefits:

Enhanced Durability: This concrete can withstand harmful environmental factors, including freeze-thaw cycles, de-icing salts, and acidic substances, thereby improving its overall performance.

Reduced Maintenance Costs: The inherent ability of self-healing concrete to repair itself minimizes the frequency and expenses associated with repair and replacement work, leading to cost savings over time.

Improved Sustainability: By extending the lifespan of concrete structures, this technology supports resource conservation and decreases the environmental impact linked to construction and demolition activities.

To achieve these self-healing properties, various innovative approaches are being employed:

Microbially Induced Calcium Carbonate Precipitation (MICP): This method involves the introduction of bacteria into the concrete mix, which can produce calcium carbonate that fills cracks upon activation by moisture.

Encapsulation Systems: Microcapsules containing healing agents such as polymers, resins, or adhesives are embedded in the concrete. When cracks occur, these capsules rupture, releasing the healing agents to seal the cracks.

Shape Memory Polymers (SMPs): These polymers are integrated into the concrete and respond to specific stimuli, such as temperature changes, to close cracks through adjustments in internal stresses.

The invention further encompasses a self-healing concrete composition, comprising a concrete matrix formed from a mixture of cement, aggregates, and water, along with uniformly distributed self-healing agents selected from various mechanisms, including microcapsules, bacterial agents, and shape memory alloys. The embedded self-healing agents activate upon crack formation through mechanical rupture, chemical reaction, or biological activation, enabling the concrete to effectively seal, fill, or bond the damaged areas.

Moreover, a method for producing this self-healing concrete includes mixing the concrete components, incorporating self-healing agents, and allowing the mixture to cure. Upon the formation of cracks due to external factors, the self-healing agents activate to repair the damage, restoring structural integrity.

This innovative self-healing concrete technology is still in its early stages but holds immense potential to revolutionize the construction industry by providing a more durable and sustainable solution to infrastructure development, effectively addressing the challenges of aging infrastructure and climate change.
Brief Summary of the Drawings

The invention will be further understood from the following detailed description of a preferred embodiment taken in conjunction with an appended drawing, in which:

Figure 1 illustrates the comparison between traditional concrete repair methods and self-healing concrete, in accordance with the exemplary embodiment of the present invention.

Figure 2 illustrates the self-healing process of concrete utilizing bacteria, demonstrating the activation of dormant bacterial spores and the subsequent production of calcium carbonate to fill cracks, in accordance with the exemplary embodiment of the present invention.

Figure 3 illustrates the incorporation of self-healing agents into lightweight aggregates for concrete production, in accordance with the exemplary embodiment of the present invention.

Figure 4 outlines the four key stages involved in the self-healing mechanism of concrete, in accordance with the exemplary embodiment of the present invention.

Figure 5 demonstrates the effectiveness of the self-healing process in reducing crack width in concrete, in accordance with the exemplary embodiment of the present invention.

Detailed Description of the Invention

The present disclosure emphasises that its application is not restricted to specific details of construction and component arrangement, as illustrated in the drawings. It is adaptable to various embodiments and implementations. The phraseology and terminology used should be regarded for descriptive purposes, not as limitations.

The terms "including," "comprising," or "having" and variations thereof are meant to encompass listed items and their equivalents, as well as additional items. The terms "a" and "an" do not denote quantity limitations but signify the presence of at least one of the referenced items. Terms like "first," "second," and "third" are used to distinguish elements without implying order, quantity, or importance.

According to the exemplary embodiment of the present invention, a self-healing concrete represents a groundbreaking advancement in construction technology, enabling concrete structures to autonomously repair cracks and thereby significantly prolong their lifespan while reducing costly maintenance requirements. This innovative solution addresses a critical challenge in the construction industry the vulnerability of concrete to cracking, which can lead to structural degradation, reinforcement corrosion, and water ingress.

In accordance with the exemplary embodiment of the present invention, wherein the self-healing concrete technology is described as a revolutionary material that possesses the remarkable ability to autonomously repair minor cracks that may develop over time. This groundbreaking innovation significantly enhances the durability and lifespan of concrete structures, effectively reducing the need for costly maintenance and repairs.

In accordance with the exemplary embodiment of the present invention, wherein the self-healing capabilities of this concrete are achieved through several primary mechanisms. These mechanisms include microcapsule-based healing, bacterial-based healing, mineral-based healing, and the use of shape memory alloys, each contributing to the overall effectiveness of the material in repairing itself.

In accordance with the exemplary embodiment of the present invention, wherein the microcapsule-based healing mechanism involves encapsulating microscopic capsules within the concrete matrix that contain a healing agent, such as epoxy resin or polyurethane. When a crack forms, the mechanical stress causes the capsules to rupture, releasing the healing agent, which then flows into the crack, polymerizes, and seals the damage, restoring the structural integrity of the concrete.

In accordance with the exemplary embodiment of the present invention, wherein the bacterial-based healing mechanism incorporates spores of specific bacteria, such as Bacillus subtilis, Bacillus pasteurii, and Bacillus megaterium, into the concrete mix. When moisture enters a crack, it activates the dormant spores, which metabolize and produce calcium carbonate that precipitates in the crack, effectively filling it and restoring the mechanical strength of the concrete.

In accordance with the exemplary embodiment of the present invention, wherein the mineral-based healing mechanism involves the addition of minerals like calcium carbonate or magnesium oxide to the concrete mix. These minerals undergo hydration reactions when exposed to moisture, producing compounds that can fill and seal cracks, thus preventing further damage to the concrete.

In accordance with the exemplary embodiment of the present invention, wherein the shape memory alloys (SMAs) are integrated within the concrete matrix. These alloys undergo expansion or contraction in response to specific thermal or mechanical stimuli, assisting in the closure of cracks by exerting pressure on the surrounding concrete, thereby enhancing the self-healing capability of the structure.

In accordance with the exemplary embodiment of the present invention, wherein the incorporation of self-healing mechanisms into concrete offers numerous advantages. These include enhanced durability, reduced maintenance costs, improved structural integrity, increased sustainability, and enhanced resilience against environmental stressors, all of which contribute to the long-term performance of concrete structures.

Figure 1 illustrates the comparison between traditional concrete repair methods and self-healing concrete. On the left side, the figure depicts the performance of a concrete structure as a line graph with dips that represent damage or cracks. A horizontal line indicates a critical safety threshold, below which the structure's performance is deemed unacceptable. Following each dip, sharp upward spikes illustrate that human intervention is necessary to repair the damage, emphasizing the reliance on manual repairs in traditional methods.

In contrast, the right side of the figure showcases self-healing concrete. Similar to the left side, the performance line shows dips representing damage or cracks. The critical safety level is again marked by a horizontal line. However, instead of sharp upward spikes, the performance line recovers gradually after each dip. This gradual recovery highlights the self-healing process, where the concrete autonomously repairs itself without the need for human intervention.

The key points derived from this figure demonstrate several advantages of self-healing concrete. First, it maintains a higher level of performance over time since it can continuously repair itself, thereby reducing the frequency of human intervention required. Second, the self-healing process leads to reduced maintenance costs and frequency, resulting in significant long-term savings. Additionally, self-healing concrete enhances the durability of structures by resisting degradation caused by cracking and environmental factors, ultimately extending their lifespan. Lastly, this innovative technology promotes sustainability by decreasing the need for frequent repairs and material replacements.

The diagram further emphasizes the importance of keeping the performance of a concrete structure above the critical safety level. Self-healing concrete provides a proactive solution by continuously addressing damage, thereby mitigating the risk of catastrophic failure. The gradual recovery observed in the self-healing scenario suggests that while the healing process may take some time, it ultimately restores the structure's original strength and integrity. The contrast between the sharp spikes associated with man-made repairs and the smooth, gradual recovery of self-healing concrete underscores the efficiency and cost-effectiveness of this revolutionary technology.

Figure 2 illustrates the self-healing process of concrete utilizing bacteria. The diagram begins with the formation of a crack in the concrete structure, which serves as the initial stage of the self-healing process. Within the concrete matrix, dormant bacterial spores are embedded and remain inactive until activated by the presence of water. The figure effectively depicts how, upon water ingress due to external factors such as rain or moisture the spores are triggered to activate.

Following the activation, the figure shows the growth of the bacteria as they germinate and multiply, forming colonies within the crack. This bacterial growth leads to the production of calcium carbonate (calcite) as a byproduct of their metabolic processes. The calcite precipitates and fills the crack, effectively repairing the damage and restoring the structural integrity of the concrete. This visual representation communicates the significant advantages of self-healing concrete over traditional repair methods, showcasing its innovative potential to develop more durable and sustainable infrastructure.

The benefits of bacterial self-healing concrete are notable. First, the self-healing mechanism extends the lifespan of concrete structures by addressing cracks before they can propagate and cause further damage. This capability is especially crucial in harsh environments where concrete faces constant weathering and stress. Additionally, the need for frequent repairs and maintenance is significantly reduced, leading to considerable cost savings, which can positively impact the overall financial management of infrastructure projects and maintenance budgets. Furthermore, by minimizing the need for material replacements and energy-intensive repair processes, bacterial self-healing concrete aligns with sustainable building practices and environmental conservation efforts.

The selection of an appropriate bacterial strain is crucial; the bacteria must be compatible with the concrete environment, possess a high calcite precipitation rate, and be non-pathogenic. Moreover, the availability of nutrients within the concrete matrix is essential for bacterial growth and calcite production. Researchers are currently exploring methods to incorporate nutrient-rich additives into the concrete mix to enhance the self-healing process further. Environmental factors such as temperature, humidity, and exposure to harmful chemicals can also influence the effectiveness of bacterial self-healing, making it vital to consider these variables when designing and implementing self-healing concrete structures.

Figure 3 illustrates the concept of incorporating self-healing agents into lightweight aggregates for concrete production. It begins with the initial state, where lightweight aggregates porous materials that reduce the weight of concrete are displayed alongside two types of self-healing agents are dormant bacterial spores and bio-mineral precursors. The process progresses with the addition of these self-healing agents into the lightweight aggregates, which can be accomplished through methods such as coating or impregnation with a suitable solution.

Once the modified aggregates are prepared, they are used to produce concrete. Over time, cracks may develop in the concrete due to factors such as thermal expansion, shrinkage, or external loads. When a crack forms, water can infiltrate the concrete, triggering the activation of the self-healing agents embedded in the lightweight aggregates. The activated agents either the bacteria or the bio-mineral precursors react with the water and available minerals in the concrete, resulting in the formation of a healing product. This product fills the crack, effectively restoring the structural integrity of the concrete.

Figure 4 outlines the four key stages involved in the self-healing mechanism of concrete.

Stage A illustrates the formation of calcium carbonate within the crack. This mineral typically forms as a result of chemical reactions between calcium ions and carbonate ions present in the concrete mix. The generation of calcium carbonate is vital because it acts as a filler material, helping to bridge the crack and restore the structural integrity of the concrete.

Stage B depicts the presence of impurities within the crack, such as aggregates, cement particles, or other debris. These impurities can block the pathways for healing agents and hinder the self-healing process, reducing its effectiveness.

Stage C shows the hydration of unreacted cement particles within the crack. Hydration occurs when cement interacts with water, leading to the formation of hydrated cement paste. This step is crucial as it provides additional material to fill the crack and strengthen the concrete.

Stage D illustrates the expansion of the hydrated cement within the crack. As the cement hydrates, it expands and exerts pressure on the crack walls, aiding in the closure of the crack and enhancing the structural integrity of the concrete.

Overall, the self-healing process depicted in the diagram combines various chemical reactions and physical processes to effectively repair cracks in concrete, emphasizing the intricate interplay of these stages in ensuring the durability and longevity of concrete structures.

Figure 5 demonstrates the effectiveness of the self-healing process in reducing crack width in concrete. In the left image, the crack in the concrete is visible before any healing has occurred, measuring 0.17 mm in width. This initial state highlights the extent of the damage present in the concrete structure. The right image illustrates the same crack after the self-healing process has taken place. Here, the crack shows significant width reduction, measuring 0.14 mm at the widest point (L1) and 0.10 mm at the narrowest point (L2). This visual comparison emphasizes the potential of self-healing technology to effectively fill in cracks and restore the structural integrity of concrete.

Key observations from this figure include the substantial reduction in crack width, indicating that the self-healing process has successfully filled the crack with healing materials. Although the diagram does not explicitly detail the mechanisms at work, it is likely that factors such as the formation of calcium carbonate, hydration of unreacted cement, and expansion of hydrated cement contributed to this reduction.

Advantages of Self-Healing Concrete
One of the primary benefits of self-healing concrete is its enhanced durability. This innovative material is designed to autonomously repair minor cracks, preventing the propagation of damage and prolonging the lifespan of structures. This attribute is crucial in maintaining the structural integrity of buildings, bridges, and other infrastructure, thereby reducing the frequency of repairs and replacements over time.

Self-healing concrete also contributes to reduced maintenance costs, as its ability to self-repair translates to significant savings for building owners and infrastructure managers. By minimizing the need for regular maintenance work, such as filling cracks and resurfacing, organizations can allocate resources more effectively, focusing on other critical areas of infrastructure management. This economic advantage is particularly beneficial in large-scale projects where maintenance costs can accumulate over time.

Moreover, the improved structural integrity of self-healing concrete ensures safety and reliability. This technology restores the original strength and performance of damaged concrete by actively sealing cracks and preventing water ingress, which reduces the risk of corrosion of reinforcement materials. This aspect is especially vital for critical infrastructure, where failure could result in significant hazards and economic losses.

Additionally, self-healing concrete promotes increased sustainability, aligning with modern construction goals of reducing environmental impact. By extending the service life of concrete structures, the demand for new materials is decreased, leading to less resource consumption and reduced waste. Furthermore, the reduced frequency of repairs minimizes the energy and resources required for construction activities, contributing to a more sustainable built environment.

Applications of Self-Healing Concrete
The applications of self-healing concrete span various sectors, with particular advantages in civil infrastructure. Bridges and overpasses, subjected to constant stress and environmental challenges, benefit from the extended durability provided by self-healing properties. This innovation not only enhances safety by reducing the risk of structural failure but also prolongs the operational life of these critical assets.

Self-healing concrete is also applied in buildings and structures, significantly improving the resilience of residential, commercial, and industrial buildings. By mitigating damage from natural disasters such as earthquakes or floods, self-healing concrete can enhance occupant safety and reduce recovery costs, ensuring that communities can rebound more quickly from adverse events.

In pavements and roads, the use of self-healing concrete presents considerable advantages. The technology helps reduce the frequency of road repairs, leading to improved driving conditions and decreased traffic congestion. This efficiency not only enhances user experience but also reduces maintenance-related disruptions, benefiting the economy as a whole.

Furthermore, self-healing concrete finds applications in marine infrastructure, protecting concrete structures from the harsh conditions of marine environments. Coastal structures, docks, and seawalls, which face challenges from saltwater corrosion and wave impact, can greatly benefit from the durability and self-repair capabilities of this innovative material, ensuring long-lasting protection against the elements.

In summary, the potential applications of self-healing concrete extend to underground infrastructure, safeguarding underground pipes, tunnels, and sewers from corrosion and erosion. This reliability ensures the efficient operation of vital systems and services, minimizing disruptions caused by infrastructure failure and enhancing overall urban resilience.
, Claims:5. CLAIMS
I/We Claim:
1. A self-healing concrete composition (100) for enhanced infrastructure durability, comprising:
a concrete matrix (102) formed from a mixture of cement, aggregates, water, and optionally additional additives for enhanced binding properties;
a plurality of self-healing agents (104) uniformly distributed within the concrete matrix, wherein the self-healing agents are selected from:
i. microcapsules containing healing agents, wherein said healing agents are selected from polymers, resins, or adhesives that are released upon rupture of said microcapsules upon occurrence of a crack;
ii. bacteria-based healing agents comprising dormant bacterial spores, said spores being of bacteria selected from the group consisting of Bacillus subtilis, Bacillus pasteurii, and Bacillus megaterium, capable of producing calcium carbonate upon activation by exposure to water, whereby said calcium carbonate precipitates and fills the crack;
iii. shape memory alloys (SMAs), embedded within the matrix, wherein said SMAs are adapted to undergo expansion, contraction, or other shape modifications upon a specific thermal or mechanical stimulus, thereby facilitating closure of cracks by adjusting internal stresses within the concrete matrix;
wherein the embedded self-healing agents are activated upon formation of a crack through mechanical rupture, chemical reaction, or biological activation to release the healing materials to fill, seal, or re-bond the cracked matrix structure;

2. The self-healing concrete composition (100) as claimed in claim 1, wherein the healing agent (102) is an epoxy resin or polyurethane encapsulated within the microcapsules.

3. The self-healing concrete composition (100) as claimed in claim 1, wherein the bacteria are selected from the genus Bacillus, including Bacillus subtilis, and are capable of precipitating calcium carbonate when activated.

4. The self-healing concrete composition (100) as claimed in claim 1, wherein the mineral precursor is selected from the group consisting of calcium carbonate, magnesium oxide, and silica, and is capable of reacting with moisture to form a healing product.

5. The self-healing concrete composition (100) as claimed in claim 1, wherein the self-healing agent is distributed throughout the concrete matrix in a uniform manner to maximize healing efficiency.

6. A method for producing self-healing concrete, comprising the steps of:
a. mixing cement, aggregates, and water to form a concrete matrix;
b. incorporating at least one self-healing agent selected from the group consisting of microcapsules containing a healing agent, bacterial spores, and shape memory alloys into the concrete matrix;
c. allowing the mixture to cure, whereby the self-healing agents are embedded within the cured concrete;
d. activating the self-healing agents upon the formation of a crack in the concrete due to external factors such as moisture ingress, thermal changes, or mechanical stress;
e. enabling the self-healing agents to repair the crack by releasing the healing agent, producing precipitates, or exerting pressure to close the crack;
f. allowing the concrete to regain structural integrity as the self-healing process occurs.

7. The method as claimed in claim 6, further comprising the step of controlling the moisture content in the concrete matrix to ensure activation of the self-healing agent upon crack formation.

8. The method as claimed in claim 6, wherein the structure demonstrates enhanced durability and reduced crack propagation compared to traditional concrete structures.

9. The method as claimed in claim 6, wherein the reduction in crack width is quantified by at least a 20% decrease compared to non-self-healing concrete structures after exposure to environmental stressors.

Documents