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The objective of this work was to study the influence of crystalline admixtures on the durability of concrete. Four concrete mixtures – two reference concretes and two alternative mixtures-were produced during the first phase of the research. Influence of curing on the activation of the crystals was investigated on concrete slab specimens. The prop...
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... mixing ratio as well as the properties of the fresh concrete mixtures are shown in Table 2. The C30/37 PRAH mixture was produced with CEM II 32.5N cement instead of CEMI 42.5R in order to reduce the production cost of the alternative mixture. ...Context 2
... remaining three slabs were cast using the same concrete with the addition of crystalline admixtures (P-c20/25) at a percentage of 0.8% per weight of cement. The mix design characteristics of both concretes are presented in Table 2. Cubic specimens of 150X150X150mm were prepared and used for measuring the compressive strength at different ages. ...Similar publications
This study investigates the potential of permeable crystalline materials to improve the properties of recycled aggregates and recycled aggregate concrete (RAC). The use of recycled aggregates in concrete production has gained increasing attention due to environmental and economic benefits. However, the lower quality and poorer durability of recycle...
Citations
... The potential to sustain a reduced water absorption rate is suggested by the use of crystalline admixtures because of their nature as water-resistant and permeability-reducing materials [12]. This has been shown in several studies with various admixture components [18,19,[33][34][35]. However, due to nonlinearity in admixture composition and testing techniques [12,16], there is a lack of comparability in studies [16,17] regarding the usage of crystalline admixtures, which makes it difficult to evaluate its viability in comparison to the similarly well-documented performance of bacterial SHC. ...
Innovations designed to reduce the construction sector's infamously large carbon emissions prioritise the sustainability of the sector. Low-carbon concrete technology advancements are currently of utmost importance due to mounting political pressure. The majority of structures' exteriors are made of concrete, which makes it susceptible to weathering and persistent deterioration. If its engineering features could be restored intrinsically, structural resilience would see extraordinary breakthroughs. The advancement of self-healing concrete (SHC) research towards structural viability has frequently been hampered by the breadth of material development and assessment with contradictory field testing. This essay provides a summary of current developments in SHC and discusses the potential and drawbacks of well-known therapeutic approaches. Additionally, patterns are seen to look at how SHC affects engineering qualities.
... The decreased water absorption rate in bacterial SHC has been relatively consistent in research compared to OPC concrete [40][41][42][43][44][45], hence lower porosity is often found in microstructural analysis [28]. In using crystalline admixtures, its nature as water-resistant and permeability-reducing [12] hints at an ability to sustain a lower water absorption rate; this has been established in various experiments with different components of the admixture [18,19,[33][34][35]. However, in the use of crystalline admixtures, there is a lack of comparability in research [16,17] due to nonlinearity in admixture composition and testing methods [12,16], this hinders understanding its feasibility in relation to comparably well-documented performance of bacterial SHC. ...
The sustainability of the construction industry is a priority in innovations made towards mitigating its notoriously high carbon emissions. Developments in low-carbon concrete technology are of peak interest today under the scrutiny of emerging policy pressures. Concrete is the external part of most structures vulnerable to permanent degradation and weathering, the possibility of an intrinsic restoration of its engineering properties promises unprecedented advancements towards structural resilience. Existing research in self-healing concrete (SHC) has often concerned the scope of material development and evaluation with inconclusive field testing, hindering its progress towards structural feasibility. This paper presents an overview of recent progress in SHC, and possible opportunities and challenges of popular healing systems are discussed. Moreover, trends are observed to investigate SHC’s influence on the engineering properties of concrete, and future projections of SHC are suggested with identification of potential research needs.
... The result showed that the highest strength improvement of approximately 11.6% was achieved by the M4.1 mixture while an improvement of 8.4% was observed on the M4.2 mixture. Sideris et al. [65] incorporated 0.8% CA by the weight of cement in addition to the C20/25 mixtures (mix code M6). As can be seen from Figure 7, the addition of CA at a low percentage of 0.8% slightly increased the compressive strength by 5.5%. ...
... It was also reported that commercial CAs from Xypex and Penetron reduced the water vapor permeability by 16% and 20%, respectively [28]. In addition, CA helped the concrete structure to withstand the chloride attack and induces lower carbonation depth, thus enhancing the concrete durability and prolonging the service life of the structure [65]. ...
... Consequently, CA acts as a stimulator of the autogenous healing mechanism of concrete [45] and simultaneously may promote a durable concrete. Sideris et al. [65] estimated that the service life of their concrete slabs without CA was about 40 years, while concrete slabs treated with 0.8% CA could reach 48 years and even more than 50 years in case an improved curing was applied, indicating the positive effect of the combination between the utilization of CA and the extension of the curing period. ...
Self-healing concrete has emerged as one of the prospective materials to be used in future constructions, substituting conventional concrete with the view of extending the service life of the structures. As a proof of concept, over the last several years, many studies have been executed on the effectiveness of the addition of self-healing agents on crack sealing and healing in mortar, while studies on the concrete level are still rather limited. In most cases, mix designs were not optimized regarding the properties of the fresh concrete mixture, properties of the hardened concrete and self-healing efficiency, meaning that the healing agent was just added on top of the normal mix (no adaptations of the concrete mix design for the introduction of healing agents). A comprehensive review has been conducted on the concrete mix design and the impact of healing agents (e.g., crystalline admixtures, bacteria, polymers and minerals, of which some are encapsulated in microcapsules or macrocapsules) on the properties of fresh and hardened concrete. Eventually, the remaining research gaps in knowledge are identified.
... Since the durability of concrete is one of the most important properties, both from a financial and a sustainability point of view, the reduction or better still the minimization of water penetration should be a top priority. It is well known that a carefully designed concrete mix, properly manufactured and executed (delivered to site, cast, vibrated and cured) and with a low water-binder ratio, results in a final product with low permeability and increased durability [2,3]. A well-known and widely accepted method to reduce the permeability of concrete mixtures and thus increase ...
... According to the results presented here, CWA seemed to be more effective in mixes with a lower water-binder ratio, which is contrary to the conclusion given in [21]. Comparing the water penetration depths of the M-0.45-R and M-0.55-R mixes, it can be seen that water penetration depth can also be reduced at a lower water-binder ratio, as indicated in [2,3]. However, it should be noted here that the standard deviations for water penetration depth are significant, suggesting that the admixture was not uniformly distributed in the mixes. ...
This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were prepared; two of them with a water–binder ratio of 0.45 and two of them with a water–binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanisms; one is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded.
This paper reported the effect of two types of crystalline waterproofing materials (CWPM), namely coating and mixing type, on concrete durability, focusing on reinforcing steel corrosion and the change in concrete microstructure. The application of coating type on concrete specimens follows the manufacturer’s recommendation. For mixing type CWPM, 0.5, 0.8, 1 and 2% by weight of cement (for small, mild, moderate and high doses) were used. All specimens were exposed to 5% NaCl solution by weight, under dry/wet cycles for 168 days. Water permeability, half-cell potential and surface resistivity were measured for concrete durability and corrosion evaluation. The results indicated that while coating type significantly improved corrosion protection, the mixing type performed better, with the 2% dosage yielding best improvement. Microstructure investigation indicated abundance of needle-like crystal structures in both specimen types. This at least partially accounted for permeability and charge pass reduction.
Cementitious composite materials are the most used material in the realization of transport infrastructures. In order to increase the service life of these structures, it is necessary to design cementitious composite materials with special properties, such as the self-healing capacity, which allows the occurrence of a self-closing phenomenon after cracking. This paper shows the performance recorded for two cementitious composites with self-healing capacity induced by the use of an integral waterproofing admixture by mass crystallization. The experimental results obtained indicate a good self-healing capacity, quantified by a degree of healing of at least 57% after 192 h of conditioning, respectively, total closure of cracks after 336 h of conditioning. This work contributes to the increase of knowledge in the field of cementitious materials with self-healing capacity, indicating a possibility of obtaining this effect through the use of a waterproofing admixture by mass crystallization, simultaneously with the presentation of the possibilities of use of industrial waste such as fly ash and limestone slurry.
