Strength Of Cementitious Composites Research Articles

Indirect prediction of graphene nanoplatelets-reinforced cementitious composites compressive strength by using machine learning approaches

Graphene nanoplatelets (GrNs) emerge as promising conductive fillers to significantly enhance the electrical conductivity and strength of cementitious composites, contributing to the development of highly efficient composites and the advancement of non-destructive structural health monitoring techniques. However, the complexities involved in these nanoscale cementitious composites are markedly intricate. Conventional regression models encounter limitations in fully understanding these intricate compositions. Thus, the current study employed four machine learning (ML) methods such as decision tree (DT), categorical boosting machine (CatBoost), adaptive neuro-fuzzy inference system (ANFIS), and light gradient boosting machine (LightGBM) to establish strong prediction models for compressive strength (CS) of graphene nanoplatelets-based materials. An extensive dataset containing 172 data points was gathered from published literature for model development. The majority portion (70%) of the database was utilized for training the model while 30% was used for validating the model efficacy on unseen data. Different metrics were employed to assess the performance of the established ML models. In addition, SHapley Additve explanation (SHAP) for model interpretability. The DT, CatBoost, LightGBM, and ANFIS models exhibited excellent prediction efficacy with R-values of 0.8708, 0.9999, 0.9043, and 0.8662, respectively. While all the suggested models demonstrated acceptable accuracy in predicting compressive strength, the CatBoost model exhibited exceptional prediction efficiency. Furthermore, the SHAP analysis provided that the thickness of GrN plays a pivotal role in GrNCC, significantly influencing CS and consequently exhibiting the highest SHAP value of + 9.39. The diameter of GrN, curing age, and w/c ratio are also prominent features in estimating the strength of graphene nanoplatelets-based cementitious materials. This research underscores the efficacy of ML methods in accurately forecasting the characteristics of concrete reinforced with graphene nanoplatelets, providing a swift and economical substitute for laborious experimental procedures. It is suggested that to improve the generalization of the study, more inputs with increased datasets should be considered in future studies.

In‐situ compressive and tensile performances of high strength engineered cementitious composite at elevated temperatures

AbstractThe study provides novel insights on the compressive and tensile strength of high strength engineered cementitious composite (HSECC) at elevated temperatures under in‐situ testing condition. An optimized mix design was employed and cylinder and dogbone specimens were tested to study the compressive and tensile strength of HSECC at elevated temperature. The tested results under in‐situ test condition were compared with the residual state by exposing the specimens to temperature up to 600°C. It was found that specimens under in‐situ condition showed a drastic decrease in compressive strength (26.8%–34.5%) at 200°C and the performance was much inferior to that observed for residual state which showed only 12.2% decrease. This trend was consistent for both tensile and compression test results. After this, the in‐situ specimens underwent slight increase in the compressive strength with only around 25% decrease at 400°C and 14%–16% decrease at 600°C. However, the residual state specimens underwent continuous decrease in strength. Therefore, this study confirmed that for high strength cementitious composites exposed to elevated temperatures, the residual test results should not be considered as the lower limit and in‐situ testing results are essential for accurately predicting the behavior of cementitious composites. Thus, this research underscores the importance of conducting both in‐situ and residual state tests in the design of HSECC structural members.

Effect of Glass Powder on the Compressive Strength and Drying Shrinkage Behavior of OPC‐ and LC3‐50‐Based Cementitious Composites of Various Strengths

This study assesses the compressive strength and drying shrinkage behavior of cement and LC3‐50‐based cementitious composites containing glass powder. A total of four, i.e., 20, 35, 50, and 60 MPa, strengths of cementitious composites were targeted by varying the mix composition and water‐to‐cement ratios. In all four composite mix types, locally available glass powder was used as 0, 5, 10, and 15% added as a partial replacement of cement and LC3‐50. The novelty of this research is the addition of waste glass powder as an alternative to silica fume, especially in a high‐strength composite (including 50 and 60 MPa). The aim was to investigate the efficiency of waste glass powder in providing eco‐friendly composites. The compressive strength was determined following ASTM C 109 standard and the drying shrinkage test followed ASTM C 157 standard. The results of compressive strength in the enhancement using up to 10% waste glass powder are beneficial in enhancing strength and reducing drying shrinkage. Furthermore, the use of LC3‐50 initially reduced compressive strength up to 14 days while increased at 28 days compared to OPC. Contrariwise, the initial drying shrinkage was higher in LC3‐50 specimens and lower at later ages compared to OPC. A detailed investigation of existing shrinkage models for mortar/composite is assessed, and limitations are also discussed.

A machine learning approach for assessing the compressive strength of cementitious composites reinforced by graphene derivatives

The potential reinforcement effect of graphene derivatives (GDs) on cementitious composites (CCs) has attracted significant attention. Previous studies, however, have produced varied results regarding the impact of GDs on CCs. This can be attributed to differences in the properties of GDs and the fabrication details of CCs reinforced by GDs. Experiments to explore these factors are both time-consuming and cost-ineffective. Additionally, no predictive model currently exists for assessing the influence of GDs on the compressive strength of CCs. In terms of Machine Learning (ML), most existing models focus on continuous parameters, including mixture design properties of CCs and reinforcing filler content, but ignore discontinuous parameters such as dispersion technique of GDs in CCs, curing type, and type of GDs.Compiling a unique dataset, this study tailors ML models to comprehensively explore the effect of GDs inclusion on the compressive strength of CCs, considering continuous and discontinuous parameters, including GD properties, fabrication details, and mixture design properties. The most used dispersion techniques and types of GDs were divided into different categories in this study. Moreover, the dataset included cement strength grade and fineness modules to distinguish between the effect of cement types' variety and GDs. Finally, the backwards elimination technique confirmed the necessity of such a customized dataset for trustworthy predictions.Artificial neural networks (ANN), decision trees, and support vector regressors could successfully investigate the impact of GDs' inclusion on the compressive strength of CCs, with ANN demonstrating superior prediction performance. Among the GDs properties, sensitivity analysis revealed that lateral size had the highest effect. Among the fabrication conditions, the dispersion technique had the greatest effect. Considering all investigated parameters, the water-to-cement ratio was considered the most influential, followed by lateral size and curing time. A low w/c significantly reduces the strength growth rate due to poor dispersion of GDs.

Effect of graphene oxide on cement mortar under quasi-static and dynamic loading

Cement composites are the most widely used construction material in the world; however, research on their resistance to high strain loads is lacking. This study investigated the effect of graphene oxide (GO) on the static and dynamic mechanical properties and microstructure of cement mortar. Dynamic tests were performed using a split Hopkinson pressure bar apparatus at strain rates up to approximately 290 s−1. The mechanical behaviors of mortar specimens infused with 0.005 and 0.01 wt% GO (weight% of GO to cement) were compared against control specimens made with ordinary Portland cement. Enhancement in the strength of cement composites was evident in both compression and split-tension when GO was added in specific doses, particularly at higher strain rates. Correlation between the dynamic increase factor and the applied strain rate is found based on the compressive and split-tensile experimental data of tested mortar specimens. The findings of this study highlight the great potential of GO for improving the performance of cement composites under high strain rate loading.

Impact of polyvinyl alcohol fiber on the full life-cycle shrinkage of cementitious composite

Engineered cementitious composite (ECC) enjoys huge potential in building structures thanks to its excellent tensile performance and energy absorption ability. However, free deformation of ECC deserves better understanding since large shrinkage strain usually induces internal tensile stress which would lead to cracking under constraint. Present study focuses on the full life-cycle shrinkage of polyvinyl alcohol (PVA) fiber reinforced ECC. Shrinkage and relative humidity (RH) at three water to cement (w/c) ratios were experimentally tested through novel integrated deformation measurement device. In contrast, plain mortars with the same w/c ratios were compared to evaluate the impact of PVA fiber on the over-time deformation and RH characteristics. Thereafter, shrinkage model considering fiber influence coefficient is established to simulate autogenous and drying shrinkage of PVA-ECC. Results show that full life-cycle shrinkage can be divided into two stages according to the internal RH measured. Distinct restraint effect of PVA fiber on both stages are observed. By comparing experimental and simulation results of PVA-ECC, the proposed fiber influence coefficient-based shrinkage model well illustrates the effect of PVA fiber, especially for high strength cementitious composites with relatively low w/c.

Nano-Silicon Dioxide-Optimized Cementitious Composite Material in the Restoration of Concrete Cracks in House Building

This study aimed to investigate the restoration performance of nanocomposite materials used in house building. The ethyl orthosilicate was used as raw material, the sol–gel method was adopted to synthesize nano-silicon dioxide (SiO2), and the doped nano-SiO2 cementitious composite material was prepared. Then, the mechanical properties of the cementitious composite material based on different nano-SiO2 content was analysed through the characterization and performance test. The results showed that the nano-SiO2 prepared this time had regular crystal phases, small particle size, and certain thermal stability, with fully developed crystal grains. By analysing the mechanical properties of nano-SiO2 doped cementitious composites, it was found that the initial setting time and final setting time both showed an upward trend when the doped content of nano-SiO2 was less than 3%. Besides, the initial setting time and final setting time of cementitious composites decreased when the content was 3%–5%. The fluidity analysis indicated that the fluidity of cementified composites gradually dropped with the growth of nano-SiO2 content. The test results of mechanical properties of cementitious composites doped with nano-SiO2 revealed that the flexural strength and compressive strength of cementitious composites presented a trend of first rising and then falling, as the nano-SiO2 content rose. Shrinkage test results showed that the shrinkage rate of the gel composites increased with the growth of duration. The specific surface area and pore ratio measurement results indicated that the specific surface area of the cementitious composite doped with nano-SiO2 was 33.42 m2/g, and the porosity was small. In conclusion, the nano-SiO2-doped cementitious composite material synthesized in this study had good mechanical properties and could be applied in the repair of concrete cracks in house building.

Development of rapid-hardening ultra-high strength cementitious composites using superzeolite and N-C-S-H-PCE alkaline nanomodifier

It is shown that high operational reliability of structural materials, in particular at high temperatures, is achieved through the use of ultra-high strength cement composites. Studies of various types of Portland cements with mineral additives of the CEM II/A type have established that a stone based on Portland cement with superzeolite is the most resistant to high temperatures. It has been proven that due to the "self-autoclaving" effect, the strength of a stone based on CEM II/A-P 42.5 R is 1.2–1.3 times higher than a stone based on other types of CEM II/A. To obtain fast-hardening cement composites, a nanotechnological approach based on the use of sol-gel technology has been implemented. Using the methods of IR spectroscopy, electron microscopy, the fact of obtaining, by the chemical method of synthesis, an alkaline nanomodifier N-C-S-H-PCE, which is a nano–liquid based on nano-core seeds of sodium/calcium hydrosilicates, has been proved. It has been confirmed that the introduction of the alkaline nanomodifier N-C-S-H-PCE provides a significant intensification of the early structure formation processes in the paste based on Portland cement with superzeolite (after 12 hours, 24 hours and 28 days, the strength is 16.9; 30.5 and 104.1 MPa). It has been established that the complex combination of Portland cement with superzeolite, corundum aggregate, basalt fiber and alkaline nanomodifier provides rapid-hardening of ultra-high strength cement composites (T=400 °C) with improved operational properties. Thus, there is reason to assert the feasibility of developing rapid-hardening ultra-high strength cementitious composites. This solves the problems associated with the need to increase their early strength and performance. As a result, it is possible to carry out repair work to protect equipment from abrasive wear at elevated temperatures

A comprehensive overview of jute fiber reinforced cementitious composites

Natural fibers are eco-friendly, cost-effective, lightweight, renewable, have better thermal properties and corrosion resistance capabilities. The addition of natural fibers in cementitious composites (CCs) will be a sustainable step to enhance their mechanical properties as well as encouraging green construction. Jute fibers are cheap among all the natural fibers and are abundantly available in several developing countries. This study describes the impact of utilizing jute fibers in CCs for sustainable construction. The influence of jute fiber on the mechanical strength of CCs is reported, including compressive strength, split tensile strength, flexural strength. Additionally, the microstructure of jute fiber is discussed, and jute fiber-matrix interaction is explained. The effect of varying jute fiber length and content on the mechanical strength of CCs has been described, and optimum jute fiber length and content have been reported. The current research initiative expects to promote understanding of the concerns and difficulties encountered during the production of jute fiber reinforced CCs. It was concluded that incorporating jute fibers can enhance the strength properties of CCs if used in shorter lengths and lower volume contents, while higher volume content of jute fibers degraded the strength properties of CCs. In addition, the current research is quite limited in terms of practical applications of jute fiber reinforced CCs, and more research is needed in the future to determine their applications in civil engineering construction. Future research has been recommended in light of the different parameters discussed in this study. Moreover, this review will be helpful in promoting the use of jute fiber for the green construction of CCs.

Biodestruction of Buildings and Constructions and Improvement of Their Longevity and Environmental Friendliness at the Basis of Application of Bio-Resistant Materials

The article discusses the problem of negative biological effects in buildings and structures. The analysis of microflora released from damaged objects is given. Risk groups for the development of diseases caused by microbial biodestructors that are potentially dangerous to humans are given. The biodegradation of residential and public buildings causes a decrease in the level of people’s health, and their disability occurs due to the deterioration of the urban environment. Microbes contained in building structures, in finishing and protective materials, can settle on the skin, enter the bloodstream through the lungs, and also with food into the human body. A number of pathologies that are difficult to cure and life-threatening have arisen recently due to a sharp drop in human immune reactivity.The object of the study was cement composites, which include port-lance cement, a mixing fluid, a filler, a fine aggregate, and additionally silicon organic compounds. The hypothesis is that the latter in the form of aryl - (aryloxy) silanes, due to their hydrolysis in a humid environment, can become potent biocidal components.During the research, generally accepted physical-mechanical and biological methods were used. To assess biostability, samples of cement composites were infected with a test by microorganisms from the following set of mycelial fungi: Aspergillus niger van Tieghem, Aspergillus terreus Thom, Aspergillus oryzae (Ahlburg) Cohn, Chaetomium globosum Kunze, Paecilomyces varioti Bainierulicomillumium Penicillium peniciumium Penicomium Thiumllium Penicillium peniciumium, Trichoderma viride Pers. ex Fr.Tests have shown that silicon organic additives contribute to a significant increase in the biostability and strength of cement composites. Studies have revealed the presence of a correlation of the fungus resistance of building composites with the addition of silanes and their hydraulic activity.

Investigation of Mechanical and Durability Behaviour of High Strength Cementitious Composites Containing Natural Zeolite and Blast-furnace Slag

In this study, the changes in the mechanical and durability properties of the concrete mortar as a result of using artificial and natural pozzolanes (blast furnace slag (BFS), natural zeolite (Z) in clinoptilolite form respectively) in the production of concrete mortar separately or together as a replacement material were investigated. For this purpose, Z and BFS were used partially replace Portland cement at 5%,10%, 15% and 20% by weight. Flow table, compressive strength, drying shrinkage, abrassion resistance experiments, rapid chlorine permeability experiments and microstructural analysis were carried out for prepared samples. According to the results, optimum dosages of the puzzolans were found 20% for grounded blast furnace slag, 10% for natural zeolite and %20 for concrete mortar containing both 10% grounded blast furnace slag and 10% natural zeolite as substitution materials. It is concluded that these pozzolan substituted in the mortar at these rates improve some properties of the mortar in the best way. In general, the aim of the study is to reduce cement production and to recycle waste products, which have a great impact on the environment.

Influence of Steel Fiber Addition on the Vibrational Characteristic of High Strength Cementitious Composites

Structural materials and their properties in different applications with next-generation composite production techniques are quite promising areas. In this study, new composite blocks were produced with the addition of industrial and recycled steel fibers to high strength cementitious composites (HSCCs). The vibrational damping capabilities of the blocks produced in standard dimensions (16 cm × 4 cm × 4 cm) were tested by using the modal analysis method. In many different applications, structural materials are expected to absorb vibrations such as earthquakes or artificial vibrations from machine systems operating in industrial areas. In this study, the vibration damping capability of HSCCs was investigated and improved by adding steel fiber to HSCCs. The experimental study shows that adding steel fibers improves the bending stress by up to 127% and damping ratio over 200%. The fiber size and distribution play a significant role in this improvement. This effect was also achieved to a certain extent in the samples produced using recycled steel fibers obtained from waste tires. In this way, the vibration damping ability of the HSCCs is increased with an environmentally friendly approach.

Experimental Investigation of Mechanical and Dynamic Impact Properties of High Strength Cementitious Composite Containing Micro Steel and PP Fibers

Cementitious composites are one of the most consumed construction materials in the world. The use of cementitious composites is increasing due to their special characteristics. The behavior of high strength cementitious composites is improved by increasing the fiber percentage. In the present paper, the effects of steel microfibers and polypropylene fibers on mechanical properties and impact resistance of high strength cementitious composites are investigated. The percentage of fibers used in the study was 0, 0.5, and 1.5% in seven separate and three combined mix designs. Experiments were carried out on 120 specimens in 10 mix designs. Compressive strength, tensile strength, flexural strength, and dynamic impact tests were carried out on 10 mix designs manufactured in this research. The dynamic impact strength of the disc specimen was investigated by a drop hammer test machine with a capacity of 7500J. After testing the samples, it was shown that using a high percentage of steel and polypropylene fibers reduces the compressive strength and increases tensile strength, flexural strength, and impact strength. The effects of steel microfibers on the reduction of the crush displacement resulting from the dynamic impact were higher than that of polypropylene fibers.

Performance of High Strength Cementitious Composites with High Volume Supplementary Cementitious Materials

Portland cement (PC) is the major binder used for cementitious composites. However, due to the increase in the demand for cementitious composites for the construction of infrastructures, there’s a consequential effect of the production of this binder (i.e. PC) on the sustainability of our environment. The production of PC emits huge amounts of carbon dioxide into the environment and posses a huge strain on the natural deposits of its raw material. In order to create a sustainable environment while meeting the high demand for cementitious composites; it is paramount to replace the PC with locally available waste materials. This study incorporates a high volume of slag alongside silica fume at a ratio of 2.2 to that of PC to produce high strength cementitious composites. The effects of these compositions were determined experimentally on its fresh and hardened properties. Results from this study showed that high strength cementitious composites can be produced with a high volume of supplementary cementitious composites up to 80%. The use of slag as 80% replacement of slag resulted in a 9.3% increase in the compressive strength and a 48.1% decrease in sorption.

Создание биоцидных препаратов «Тефлекс»: от синтеза нового полимера до линейки продукции. Часть 2. Исследование влияния препаратов «Тефлекс» на свойства цементных композитов

Повреждения строительных материалов, вызванные ро­стом и развитием на них бактерий и мицелиальных грибов представляют серьёзную опасность как для конструкций зданий и сооружений, так и для здоровья людей. Один из эффективных способов устранения данных негативных фак­торов - это введение в их состав биоцидных добавок.
 Приводятся результаты исследования свойств цементных композитов, содержащих в своем составе различные био­цидные препараты на основе гуанидиновой группировки (ПГМГ), которые выпускаются в РФ в промышленном масштабе под маркой «Тефлекс». При выполнении исследований рас­сматривались препараты марок: «Тефлекс Антиплесень», «Тефлекс Антисоль смывка», «Тефлекс Реставратор», «Тефлекс Защита для металла», «Тефлекс дезинфицирующий», «Тефлекс индустриальный». Показано, что применение биоцидных препаратов способствует снижению обрастаемости образцов цементных композитов мицелиальными грибами и проявле­ние у них грибостойких и фунгицидных свойств.
 С использованием метода рентгеноструктурного анализа выявлено, что при введении в составы соединений гуанидина изменяется количественное содержание минералов алита и белита. Исследованы цементные композиты, твердеющие как в нормальных температурно-влажностных условиях, так и подвергнутые термовлажностной обработке. Установлено, что введение всех рассмотренных добавок оказывает пластифи­цирующее действие и изменяет ряд других свойств. Прочность цементных композитов с добавками в количестве 3-5 мас. ч увеличивается. Приведены результаты исследования свойств композитов, наполненных кварцевыми порошками различной дисперсности и препаратом «Тефлекс». При этом наряду с одно­фракционными рассматривались многофракционные составы. Полученные результаты дают основание рекомендовать цемент­ные композиции, содержащие добавки на основе гуанидина, для использования в зданиях и сооружениях с биологическими средами. Приведены сведения о результатах использования цементных материалов и изделий в строительной отрасли.

Experimental study on Portland cement/calcium sulfoaluminate binder of paste filling

The curing time and compressive strength of ordinary Portland cement have its limitations, which limits its application range. In this article, the ratio of ordinary Portland cement/CSA ratio is optimized by laboratory test, and the composition and structure of hydration products are changed to achieve the performance adjustment. Then, the microstructures of the optimized cementing materials at different stages were observed and compared by the analysis of hydration process and scanning electron microscopy. The experimental results show that the setting time decreases with the increase of sulphoaluminate cement content in the system and prolongs with the increase of gypsum content, and the change trend of initial setting time and final setting time is consistent. When the content of sulphoaluminate cement exceeds 14% or the content of gypsum exceeds 16%, the compressive strength of cementing material decreases greatly in the early and late stages, but the strength of cementing material does not increase beyond this range. Composite admixtures H3BO3 (0.3%) + Na2SO4 (0.1%) and H3BO3 (0.3%) + NaNO3 (0.1%) can not only improve the setting time of composite cementing materials, but also improve the strength of composite cement.

On structural properties of the matrix phase of high-strength cement composites

From the standpoint of structural mechanics of the destruction of materials, the most important element of the structure of cement composites is the cement matrix phase, which predetermines the quality of structural strength and the mechanical behavior of the composite as a whole. The disclosure of the functional relationship between the acting stresses and deformations is one of the main stages in the study of the mechanical behavior of any solids of structural purpose. A comparative comparison of the mechanical behavior of macrostructures of experimental samples of cement composites of different composition on three varieties of quartz sand under axial compression is shown experimentally. The assessment of diagrams on the ultimate longitudinal and transverse relative deformation, longitudinal and transverse relative deformation of short-term ductility (creep), transverse deformation coefficient and differential coefficient of volumetric deformation and its increments, plasticity measures, location level of parametric point, the initial elastic modulus and elastic characteristics, and the specific fracture energy on the total longitudinal strains and strains of short ductility is made. A comprehensive methodology for assessing the structural and mechanical parameters of the structural strength of cement composites, obtained together on each prototype, makes it possible to obtain more differentiated characteristics. They reflect the synergistic effects of the mutual influence of structural and destructive structure formation and hardening of cement disperse systems, due to the filler concentration and quality indicators of the dispersed phase of cement composites. This makes it possible to more fully study the mechanical behavior of the material under load that, in turn, makes it possible to move from simple determination of quality parameters to active material quality management.

Effect of Inorganic SiO2 Nanofibers in High Strength Cementitious Composites

The paper deals with the verification of the effect of the addition of inorganic SiO2 nanofibers to cement composites. In the first stage, a stable suspension of SiO2 nanofibers was prepared in an aqueous medium. It is important to distribute nanofibers so that the nanofibers do not appear in the form of clumps and at the same time do not get damaged during the dispersion process. The ultrasonification process was used for dispersion. The dispersed suspension of SiO2 nanofibers and water was dosed together with the superplasticizing admixtures into the dry components of the cement composite and the components were homogenized. The properties of the cement composite with SiO2 nanofibers have been tested – compressive strength, flexural strength, density. Composites with the addition of SiO2 nanofibers at a dose of 0.008 % by weight of cement exhibited an increased compressive strength of up to 33 % and a 19 % greater flexural strength at doses of 0.016 and 0.032 % of cement weight than the reference sample without nanofibers. The presence of SiO2 nanofibers in the composite was monitored by scanning electron microscopy (SEM).

The mechanical strength and durability properties of ternary blended cementitious composites containing granite quarry dust (GQD) as natural sand replacement

Cementitious composites are the most used man-made materials in the world with a global annual production quantum of 25 billion tonnes worldwide, contributing approximately 5% to the global greenhouse gas emissions. In the initiative to reduce the carbon footprint of cementitious composite production, are growing interests in the large volume reuse of industrial by products such as ground granulated blast-furnace slag (GGBS), pulverized fuel ash (PFA) and granite quarry dust (GQD) in cementitious composites production. Such an approach offers a two-fold solution towards addressing the waste management problem related to those industry by-products. At the same time however; reduction of carbon footprints of cementitious composite materials exists. However, in order to enable scalable applications of such a recycling approach, a comprehensive body of knowledge on the mechanical strength and durability performance of the cementitious composite products containing a large volume of the materials needs to be established. Hence, it is the primary aim of the study to report a comprehensive assessment on the mechanical strength and durability properties of high strength cementitious composites. These materials are produced with a large volume of the aforementioned materials as the primary binder and aggregate phase. Throughout the investigation, high strength cementitious composites mixes were produced with a large volume of PFA and GGBS binder. Then phase coupled with ordinary Portland cement (OPC). GQD was used as the fine aggregate phase in substitution of natural river sand at various level of substitution ranging between 0 and 100% by volume. The cementitious composites were characterized in terms of its fresh cementitious composites. Its flowability and hardened cementitious composites properties mainly bulk density, compressive strength, flexural strength, and Ultrasonic Pulse Velocity were also assessed. In addition, the durability properties such as water absorptivity and porosity were also covered in this experimental program. Pore continuity was assessed in terms of air permeability and capillary absorption of the hardened specimens according to the testing age. This paper has also covered the dimensional stability assessment in terms of drying shrinkage. Besides, a comprehensive microstructural assessment was also performed to examine the microstructure morphology. From the results, we found full incorporation of GQD as NRS without significant impairment to the mechanical, durability and length change performance. Thus, the production of sustainable high strength cementitious composites with large volume recycling of GQD is feasible which in turn reduces the depletion on the natural river sand resources.

Flexural Performance and Reflective Cracking Behavior of Repair Systems Produced with High Early Strength Cementitious Composites

Çalışma kapsamında, yüksek süneklilik ve çekme yüklemeleri altında sergilenen çoklu dar çatlak genişlikleri özelliklerinden ödün vermeden erken yaş yüksek dayanımlı ve onarılacak beton ile en yüksek derecede bağ kuracak yeni nesil onarım malzemeleri tasarlanmış ve bu malzemelerin performansı piyasada yaygın olarak kullanılan bir başka onarım malzemesiyle karşılaştırılmıştır. Çalışmanın birinci bölümünde monolitik halde test edilen karışımların temel mekanik özellikleri değerlendirilmiştir. İkinci bölümde ise tabakalı olarak hazırlanan karışımların onarım malzemesi olarak kullanılabilirlikleri eğilme performansı ve yansıma çatlağı davranışları göz önünde bulundurularak değerlendirilmiştir. Çalışma kapsamında üretilen HESECC karışımlarının tamamı literatürde bir onarım malzemesinden erken yaşta beklenen temel mekanik özelliklerin tamamını fazlasıyla karşılamış ve üretilen tabakalı numuneler, piyasada yaygın bir şekilde kullanılan OM numunelerine kıyasla çok daha sünek bir davranış sergileyerek yansıma çatlağının yayılımını önemli ölçüde azaltmıştır.