Crystalline Admixture Research Articles

Research on the properties of crystalline admixtures: Self-healing healing materials for concrete from multiple perspectives

The research on the self-healing of concrete promoted by crystal admixtures provides a new direction for the green development of construction industry. In this study, three crystal admixtures, i.e., l-aspartic acid (LAA), Na2SiO3 and nano-silica (NS), were screened from the experimental results in terms of promotion of hydration, fast reaction, and effective filling. The three components were mixed as concrete self-healing agents, and the experimental ratio was designed by response surface method. Finally, the optimal ratio was selected according to the visual healing effect. The durability of mortar with the optimum ratio of self-healing agent was studied by the experiment of resistance to chloride ion and sulfate attack; its preliminary heat release was studied by hydration microcalorimeter. The microscopic analysis was carried out by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) test and mercury injection method (MIP). The experimental results showed that the best healing effect was achieved when the dosage of LAA, Na2SiO3 and NS reached 0.5 %, 0.4 % and 0.15 % of the cement mass. In the process of healing, the early healing products are mainly calcium carbonate, and the late healing products are mainly ettringite and calcium silicate hydrate (CSH), and the healing agent effectively reduces the porosity and improves the pore structure, making the concrete matrix more dense.

Integral and Surface Treatment Method of Waterproofing: A Review and Comparative Analysis

Water seepage into concrete can cause deterioration and other aesthetic issues that limit the life of concrete constructions. This paper examines and contrasts the various kinds of waterproofing techniques. There are essentially two types: surface treatment method and integral method. Water repellents, crystalline admixtures, and densifiers are examples of integral methods. Surface treatment methods encompass pore-blocking, hydrophobic impregnation, surface coating, and multifunctional surface treatment. The processes of various approaches are examined in this article, followed by a comparison of their durability and mechanical properties. We discuss several properties, such as sulfate attack, chloride penetration, carbonation, reinforcement corrosion, water absorption and permeability, compressive, flexural, and tensile strength. The findings indicate that each has merits and demerits of their own. The inclusion of an integral admixture to concrete offers a number of advantages over surface protection, including convenience of application, the removal of the need for ongoing maintenance, and minimal to no deterioration over time. While surface treatment methods significantly reduce water permeability and porosity. In conclusion, we give a succinct summary of certain issues regarding the present state of research and future directions for the hydrophobic modification of concrete.

The Effects of Crystalline Admixtures on Concrete Permeability and Compressive Strength: A Review

The durability and strength of concrete in construction can be significantly compromised by permeability issues, which pose considerable challenges to its long-term effectiveness and reliability. By analyzing six selected articles from the Scopus database, this study meticulously synthesizes findings on the effectiveness of CAs in improving these essential properties of concrete. The research meticulously documents and analyzes key variables such as the CA dosage, water–cement ratio, evaluation duration, and treatment conditions, providing a thorough understanding of the factors that influence the performance of CAs in concrete. The results robustly indicate that CAs significantly reduce concrete permeability, thereby enhancing its resistance to water and other detrimental substances, and simultaneously boosts the compressive strength, leading to stronger and more durable concrete structures. However, the study also reveals that the impact of CAs can vary considerably depending on the specific conditions and methodologies employed in the individual studies. This underscores the importance of standardized testing procedures to ensure consistent and comparable results across different studies. This research provides valuable insights for optimizing the use of CAs in concrete formulations, ultimately aiming to improve the durability, performance, and sustainability of concrete in construction applications.

A synergetic self-sealing model for cement-based composite using granular expansive agent and crystalline admixture

The autogenous self-sealing model has been researched in previous work, which could help to characterize the self-sealing process with crystalline products. The model outcome was presented in the form of leakage water flow, which demonstrates the self-sealing capacity or the recovery of watertightness. While in the research area of cement-based material self-sealing, the expansive agent cannot be neglectable, for example the superabsorbent polymer (SAP). Especially for the building components exposed to free water, an efficient water flow blockage after cracking is crucial to ensure stable service. Hence in this study, the self-sealing process of a granular expansive agent inside the crack of cement-based material was simulated. The model outputs were compared with experimental results to verify the reliability. Additionally, the autogenous self-sealing model was incorporated into this model to simulate the “crystallization-expansion” synergetic self-sealing. The contribution of crystalline product and expanded EA to water flow blockage were compared during the crystallizing process. Overall, this model is of great use to evaluate the role of expansive agent on water flow blockage after the cement-based material cracking in hydraulic engineering or engineering components exposed to water.

Crack-healing and rheological properties of high content fly ash/slag/silica fume green and sustainable cement-based materials incorporating crystalline admixture and calcium alginate biomass hydrogel

Cracking is an important factor affecting the durability of concrete. Rheological properties are important performance indicators of the workability of fresh concrete. Ion chelator (CA) is one kind of crystalline admixture, which can enhance crack-healing of concrete by promoting the formation of calcium carbonate in wet environment. Calcium alginate hydrogel (CaAlg) can maintain the humidity of cementitious matrix and promote the crystallization of inorganic minerals. Therefore, in this study, CaAlg bead was prepared to further improve the crack-healing of cementitious materials containing CA. Self-healing performance was evaluated by visual crack closure and water permeability test. Rheological property was measured by rotor rheometer. Healing mechanism of cementitious materials with CA and CaAlg was analyzed. Results showed that with the increase of CaAlg dosage, yield stress and plastic viscosity of paste decreased gradually. Meanwhile, fly ash and slag reduced viscosity of pastes, while silica fume increased the viscosity of pastes. CA could evidently improve the permeability and mechanical properties of mortar, especially for slag mortar. Self-healing performance test and characterization showed that CaAlg could further enhance crack-healing process of mortar with CA, especially for pure cement and slag mortar. Microscopic testing indicates that CaAlg could induce the formation of vaterite and calcite on its surface to further improve crack-healing efficiency.

Self-healing concrete with a bacteria-based or crystalline admixture as healing agent to prevent chloride ingress and corrosion in a marine environment

Innovative solutions are needed to improve the durability of concrete structures in marine environment. Bacteria-based agents (BAS) and crystalline admixtures (CA) are explored as healing agents to enhance chloride resistance and prevent corrosion. Healing of 100 μm and 300 μm wide cracks was investigated, in combination with two conditioning methods. Either the samples were subjected to wet/dry cycles for 3 months before exposure (“healed”), or they were directly exposed to artificial seawater after crack creation (“unhealed”). After 12 months of submersion, BAS reduced chloride ingress even in the presence of cracks but showed limitations in preventing corrosion in cracked samples. In contrast, the CA series demonstrated a reduction in chloride ingress in both uncracked and cracked concrete and effectively prevented reinforcement corrosion in healed samples and samples with cracks of 100 μm. This highlights the potential of customized self-healing solutions to improve concrete durability in marine environments.

Composites with Immobilized Bioactive Spirulina on an Inorganic Substrate (Yellow Clay, Hydroxyapatite, SiO2, TiO2, ZnO).

In order to improve the structural properties of clays and composites of powdered spirulina, clay, nanosilica, hydroxyapatite, TiO2 and ZnO were used as an additive for mechanical processing. As a result, composites with natural nanostructured materials (NNM) are prepared with improved structural properties and bioactivity. The mixtures based on NNM with crystalline kaolinite, clays and admixtures were processed in a knife mill. The materials were characterized using FTIR spectroscopy, nitrogen adsorption and desorption, SEM release of bioactive components (anthocyanin 0,004-0,07 mg/g; chlorophyll 20-29 mg/g), composite toxicity level (below 25%), particle size measurement and surface charge density, zeta potential. Adsorption enthalpies during the formation of an intermolecular complex during the interactions of an anthocyanin molecule with the appropriate component of the composite were also calculated. There are regularities in the characteristics depending on the type of NNM, particle morphology and textural features of solids. The morphological and structural properties of the components changed slighty in the blends because the processing was conducted under relatively low mechanical stress. The morphological, textural and structural characteristics of the composites as well as the transformation to a nanostructured state, assume great bioactive activity of the composites, interesting for practical applications in medicine and cosmetics.

Experimental Study on Self Healing Concrete by using the Silicon Dioxide Nano Particles and Crystalline Admixture

Experimental Study on Self Healing Concrete by using the Silicon Dioxide Nano Particles and Crystalline Admixture

Experimental study on long-term impermeability of recycled aggregate concrete mixed with crystalline admixture and waste glass powder

The impermeability of recycled aggregate concrete (RAC) presents challenges for underground engineering, particularly concerning its larger pore. Combining crystalline admixture (CA) with waste glass powder (WGP) offers a feasible solution to enhance impermeability. To understand the collaborative mechanism of CA and WGP in improving RAC impermeability and establish an accurate mixture ratio, we conducted compressive strength tests and a series of permeability tests on WGP and CA modified recycled aggregate concrete (WRC). These tests involved different CA contents (0%, 1%, and 2%) and varying WGP replacement rates (0%, 10%, 20%, and 30%). Our findings indicated that when the WGP substitution rate exceeds 10%, the strength of the WRC decreases by approximately 23%. In contrast, the overall decline is about 5% when the CA content increases from 0% to 2%. Therefore, the WGP emerges as the primary factor influencing the compressive strength of WRC. Meanwhile, The WGP and CA play a major role in enhancing the short-term and long-term impermeability of WRC, respectively. Additionally, When the WGP substitution rate increases from 0% to 30% on same CA content, the RC increases by approximately 2%, indicating that elevated WGP content enhances the effectiveness of CA. Finally, the optimal combination to improve the impermeability of WRC is 10% WGP substitution and 1% CA content. Microscopic tests analyses show that under the influence of CA and WGP, C–S–H gel, C-A-S-H gel, and Ettringite are produced inside the WRC, effectively blocking pores and cracks, thus improving the specimen's impermeability. This research not only holds the potential to elevate impermeability but also offers a solution to the issue of waste glass accumulation, contributing to global sustainable development.

Self-healing properties of mortar with crystalline admixture: experimental investigation and parameter optimization

The inclusion of crystalline admixture (CA) is a highly effective method for enhancing the self-healing properties of mortar. This study examined the complexing abilities of different complexing agents under varying temperatures, pH levels, and ion species in order to select effective complexing agents for diverse environments, as complexing agents play a crucial role in CAs. After determining the type of complexing agent, an orthogonal array design was used to optimize the components of CA, and the strengthening mechanism of CA for mortar was discussed through microstructure analysis. The results showed that the complexation behavior of triethanolamine (TEA) and glycine performed better than sodium citrate for different pH levels, temperatures, and ion species. Meanwhile, TEA and glycine showed complementarity at different stages, so TEA and glycine were used as complexing agents in this study. Based on the orthogonal experiment, the optimal contents of Na2SiO3, Na2CO3, TEA, glycine, Ca(COOH)2, and nano-SiO2 in CA were determined to be 1.0%, 1.0%, 0.04%, 1.0%, 0.5%, and 1.0%, respectively. Under the synergistic effect of TEA and glycine, the hydration of aluminate and ferrialuminate was accelerated, and the hydration degree of cement paste was increased. At 28 d, the contents of CaCO3, calcium-silicate-hydrate (C-S-H) gel, and ettringite of cement paste with CA were higher than these of plain paste, but its Ca(OH)2 content was lower. Although the Ca(OH)2 content in the cement paste with CA was lower, the Ca(OH)2 crystal structure filled in the pores was larger. Therefore, the mortar mixed with CA exhibited higher compressive strength, water impermeability, and self-healing ability.

Water Proofing System in Concrete Structures

Water proof structure is a design concept that aims to repel water and prevent any moisture from seeping into the materials used in construction. This type of structure is particularly important in areas prone to heavy rainfall or flooding, as it helps maintain the integrity and durability of the building. Water proof concrete is formulated with additives and admixtures that create a barrier against water infiltration, making it ideal for areas prone to high levels of humidity or moisture. By incorporating this technology into construction projects, builders can ensure that their structures remain protected from the damaging effects of moisture, such as mold growth, deterioration of building materials, and potential structural issues. The use of abstract damp proof concrete represents a forward-thinking approach to building design and can greatly enhance the durability and longevity of a building.Crystalline admix water proofing with water stops, water proofing with Atactic Polypropylene membrane, and injection are the water proofing systems most commonly used in basements. Using non-shrinking cementitious grout for waterproofing, concrete must have crystalline admixtures made of cementitious powder and water. For toilets in non-sunken places, water proofing with an elastomeric cementitious coating is used. In sunken areas, brick jelly cement concrete with inherent water proofing compound is used.In this paper it deals with the different types of water proofing system..

Modification of Concrete Mix Design with Crystalline Admixture for Self-healing Improvement

Modification of Concrete Mix Design with Crystalline Admixture for Self-healing Improvement

The influence of crystalline technology as concrete admixture on compressive strength and permeability

In regions prone to frequent rainfall or coastal exposure, concrete gradually becomes porous due to environmental influences. This study systematically examines the impact of different concrete formulations on compressive strength and permeability. It evaluates standard concrete, concrete with 1% and 2% crystalline admixtures, and concrete utilizing Portland cement type V. Compressive strength tests reveal that concrete with 1% and 2% crystalline admixtures, alongside Portland cement type V concrete, exhibit superior quality compared to standard concrete. Permeability assessments unveil intriguing trends: Portland cement type V concrete displays heightened permeability relative to standard concrete, while 1% and 2% crystalline admixture concretes exhibit significantly reduced permeability, surpassing both standard concrete and Portland cement type V concrete. The heightened concrete density associated with crystalline admixtures can be attributed to their dual influence on augmenting compressive strength and decreasing permeability. By reinforcing these mechanisms, crystalline admixtures effectively enhance concrete durability. This research contributes to the understanding of advanced construction materials and offers insights into sustainable infrastructure development possibilities. Subsequent sections delve into experimental intricacies, result explications, and wider implications of these findings, shaping the trajectory of future construction practices.

Effect of crystalline admixtures on shrinkage and alkali-silica reaction of biochar-cementitious composites

This study investigated effects of crystalline admixture (CA) on shrinkage and alkali-silica reaction behaviours of biochar-cementitious composites. Addition of 1–1.5 wt% superabsorbent polymer (SAP) completely mitigated autogenous shrinkage while slightly increasing the 120-day total shrinkage of the SP-cement composite by 5.7%, resulting in the highest apparent porosity. 1–1.5 wt% CA addition did not affect autogenous shrinkage while slightly reducing the 120-day total shrinkage by 10.1%. The combination of CA and waste wood biochar (WWB) reduced autogenous shrinkage by 24.23% and 120-day total shrinkage by 23.6%, resulting in the lowest apparent porosity. The formation of hydration products in the WWB pores and on WWB surface densified the cementitious matrix, leading to a reduction in water evaporation. Furthermore, for specimens exposed to 1 M NaOH solution at 80 °C, CA addition significantly reduced the 120-day expansion by 50.6%, while the combination of CA and WWB addition reduced the 120-day expansion by 42.9%.

Influence of crystallizing type chemical admixture on precast micro concretes: a statistical analysis and holistic engineering overview

The aim of this paper is to evaluate the influence of a crystallizing chemical admixture on precast micro concretes with two water contents (7% and 11%, by dried mass) and two different conditions of exposure. Thus, precast micro concretes with a composition of 1:3 (cement: fines) with and without crystalline chemical admixture were evaluated on compressive strength (at the age of 28 and 154 days) and water absorption by immersion (at the age of 154 days). Statistical analysis showed that the only significant factor was the effect of the water content on the compressive strength. Besides that, the most significant factors for the water absorption and voids index properties were the water content, followed by the exposure conditions, and the interaction between the water content and the presence of the chemical admixture. The crystalline admixture was insignificant in the conditions of this research.

Effect of hemp fibers and crystalline admixtures on the properties and self-healing efficiency of lime and clay-based mortars

This study investigates the impact of hemp fibers on two fiber-reinforced compositions, clay-based and lime-pozzolan mortar. Three compositions were prepared for each mortar, reference samples without fiber incorporation, samples with untreated hemp fibers, and samples with hydrothermally treated hemp fibers with crystallines. Crystalline admixtures (CAs) were incorporated into the hydrothermal pretreatment of fibers to promote the self-healing properties of the mortar when needed. Physico-mechanical and thermal properties took place to address the overall effect of hemp on the mortars. Adding hemp fibers enhanced the mechanical strength and reduced the mortars' shrinkage. The hydrothermally treated fibers have better cohesion with mortars, preserving the best results. To evaluate self-healing efficiency, pre-damaged cubic samples from each composition were subjected to tap water immersion for lime-pozzolan mortars and a controlled humid chamber for clay mortars after a curing period. The healing rate was assessed by measuring crack closure, compressive strength recovery, and the dynamic modulus of elasticity recovery. The results indicated significant strength recovery in lime-pozzolan mortars with hemp fibers. Clay-based mortars showed moderate strength increases and limited self-healing.

Effect of a Crystalline Admixture on the Permeability Properties of Concrete and the Resistance to Corrosion of Embedded Steel

Reinforced concrete structure durability hinges on concrete permeability, which relies on the characteristics of the inner porous network. Harmful ions and gases can accelerate steel corrosion. Permeability-reducing admixtures (PRA), including crystalline admixtures (CA), are commonly used to mitigate this. This study examines a commercial CA’s impact on durability-related aspects in concrete specimens. Two concrete mixtures with matching proportions were prepared: a reference mix and another mix with a commercial crystalline admixture. Several properties were studied, such as compressive strength, density, porosity, electrical resistivity, water absorption capacity, chloride diffusion, air permeability, and corrosion resistance. The studied admixture in concrete yields several positive outcomes such as a slight reduction in mixing water, a potential 6% increase in concrete’s compressive strength and the development of a denser and less permeable structure with 3% lower porosity and water absorption than the reference mix. Electrical resistivity improves by 10%. Unidirectional chloride diffusion tests show no differences. Air permeability decreases by from 36% to 55%, and the water absorption rate diminishes by 23%. The admixture potentially reduces the scatter in corrosion initiation periods for steel reinforcements, delaying corrosion onset by around 60 days, although more extensive experiments are needed for definitive conclusions.

Evolution of self-healing performance of UHPC exposed to aggressive environments and cracking/healing cycles

This paper investigates the resilience of UHPC's self-healing capabilities under aggressive environmental conditions and cracking/healing cycles. UHPC specimens ‘with a double-edged wedge splitting geometry were made, incorporating a commercial crystalline admixture (Penetron Admix®). The evaluation of UHPC's healing capacity involved subjecting pre-cracked samples to three different water immersion conditions: tap water, saltwater, and geothermal water. The closure of cracks during different curing periods was meticulously recorded using optical microscopy. Furthermore, specialized tests, including ultrasonic pulse velocity (UPV) measurements and splitting tensile tests, were conducted to quantify the recovery of mechanical properties. The results reveal that extended exposure results in a gradual closure of cracks, where salt water and geothermal water exhibit lower self-healing capabilities. Self-healing improves after the 1st crack/self-healing cycle but decline rapidly after the 2nd cycle. Mechanical property is strongly correlated with the extent of self-healing, and all samples display varying degrees of stiffness recovery, with the most pronounced recovery occurring after the 1st cycle. However, following the 2nd cycle, the stiffness recovery values decrease due to repeated loading, resulting in increased damage and a reduced number of reactive particles, thereby compromising self-healing and stiffness recovery. Despite enduring multiple instances of crack damage, UHPC samples still exhibit notable toughness recovery, underscoring the enduring efficacy of the self-healing mechanism even in challenging conditions.

Investigation into the Effects of Crystalline Admixtures and Coatings on the Properties of Self-Healing Concrete.

One fascinating concept for enhancing the durability and lifespan of concrete buildings involves the use of self-healing concrete. This study focuses on the effect of crystalline admixtures and coatings on various properties of self-healing concrete and provides a comparison with traditional concrete. Four different concrete mixtures were prepared to assess their effectiveness in bridging crack openings, their flexural and compressive strengths, and water absorption. Various testing methods, including destructive, semi-destructive, and non-destructive tests, were used in this research. The capacity of the mixes to repair themselves was assessed on the destroyed and semi-destroyed test specimens using crack-healing and microstructure testing. Additionally, all mixtures were also subjected to the slump cone test and air content test in order to investigate the characteristics of the concrete in its fresh state. The findings demonstrate that crystalline coating and admixture combinations have significant potential for healing concrete. The compressive and bending strengths of self-healing concrete mixtures were shown to be slightly higher compared to traditional concrete when the additive dose was increased. Self-healing concrete mixtures also exhibited much lower water absorption, a tightly packed and improved microstructure, and signs of healed gaps, all of which indicate greater durability.

Influence of engineered self-healing systems on ASR damage development in concrete

Supplementary cementing materials (SCMs) have proven effective in minimizing alkali-silica reaction (ASR) development. In addition, crystalline admixtures (CAs) have been identified as potential solutions to counteract damage in concrete. However, limited data on this topic is available in the literature. This study investigates the impact of CA on concrete damage and is divided into two phases: 1) the effectiveness of CA in self-healing cracks and restoring the mechanical properties of mechanically damaged concrete; 2) it explores concrete mixtures incorporating a wide range of binder compositions (i.e., general use type cement, silica fume, fly ash, slag and Metakaolin) and chemical admixtures (i.e., commercially available CAs and modified versions) in conditions enabling ASR development. Both phases involve microscopic/mechanical analyses to assess the effects of CA on damage, and comparisons with concrete mixtures without CAs are made. The results reveal that CA enhanced the self-healing of cracks up to 82 % of cracks in cement paste (115 % higher values than concrete mixtures without CA) and restored 69 % of compressive strength. Furthermore, although CAs could change the damage mechanism of ASR, they did not “safely” mitigate it. However, combining SCMs and CAs effectively reduces ASR-induced expansion.