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The effect of nano silica on mechanical and durability properties of concretes containing recycled coarse aggregates (RCA) is investigated using seven series of concretes: the first is the control series, containing all natural aggregates and no nano silica. In the second and third series, 25% and 50% (by weight) natural coarse aggregates are repla...
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... Furthermore, Fig. 10 shows the comparison of the relative chloride diffusivity of R100 with different NS dosages between this experimental result and the data from the literature [36,61,62]. It is found that the experimental data in this study generally had a similar variation trend with the other relevant studies. ...
... Comparison of relative chloride diffusivity of RAC with different NS dosages[36,61,62]. ...
This paper conducted an experimental investigation on the compressive strength, transport properties behavior and its microstructure of recycled aggregate concrete (RAC) internally modified with nano-SiO2 (NS). The capillary water absorption and chloride penetration resistance of RAC incorporating 0, 30%, 50% and 100% weight replacement of RCAs (namely, R0, R30, R50 and R100) with different NS dosages (0, 1%, 2% and 3% of cementitious materials) were experimentally investigated. The coupled action of NS and RCAs on the resistance to water absorption and chloride penetration into concrete were further discussed. Mercury intrusion porosimetry (MIP) was used to determine the pore structure of mortar in RAC and scanning electronic microscopy-energy dispersive spectrum (SEM-EDS) was selected to characterize microstructural properties of ITZs and mortar. The results indicate that the optimum dosage of NS was determined to be 3%. The 28-day compressive strength of R100 with 3% NS addition was nearly 1.15 time that of R100 without NS addition, and the initial sorptivity and chloride diffusion coefficient of R100 with 3% NS addition was 23.1% and 37.10% lower, respectively, than that of R100 without NS addition. This phenomenon can be attributed to filling effect, nucleation effect and pozzolanic effect of NS. The coupled action of the RCA content and NS dosages has a slightly influence on the sorptivity and chloride diffusion coefficient. The initial sorptivity of R100 with 3% NS addition was about 1.47 time as much as that of R0 without NS addition. The pore structure of specimens is refined by NS according to the obtained MIP results, and a proportion of harmful pores and less harmful pores are transformed into harmless pores. In addition, the microscale analyses suggest that NS promises an optimization of ITZ structures and compacts the mortar matrix, thus improving the mechanical and durability-related properties of RAC.
... Also, aggregate properties have a great impact on the volume of permeable voids of concrete. According to Shaikh et al. [27] volume of permeable pores in concrete containing recycled coarse aggregate was not significantly influenced by nS addition. After the samples were conditioned for 18 days (3 days in a desiccator and 15 days in a sealed container), the test was performed following ASTM C1585-13, with results provided in Figure 5a. Figure 5b shows the calculated initial sorptivity and secondary sorptivity. ...
Fly ash class F from Thermal Power Plant “Stanari” was used in combination with highly plastic brick clay from Busovača to develop building bricks. The brick clay and fly ash were characterized for chemical and mineralogical composition, grain size distribution, and specific gravity. The fly ash has a higher proportion of larger particles and lower specific gravity than clay. The brick clay was mixed with 20, 40, and 60 wt. % of fly ash, formed in a prismatic shape, dried and then fired at 800, 900, and 1000 °C. The fired prisms were characterized for water absorption, apparent porosity, apparent density, and strength and compared with conventional clay prism. The addition of fly ash of 20, 40, and 60% reduced the mass of the samples by 14, 23, and 31 %, increased apparent porosity by 60, 100, and 160 %, and reduced the compressive strength by 50, 80 and 90%, respectively. Conducted tests and comparative study have shown that the fly ash “Stanari” can be used as an additive to the clay “Čavka” in the maximum amount of 20 % and the optimum firing temperature is 900 °C.
... proportions of nano-silica demonstrated the same results. According to Mukharjee and Barai (Mukharjee & Barai, 2014c), water absorption increased with an increase in the RCA replacement ratio and decreased with an increase in nano-silica doses. In comparison to traditional RAC with 100% RCA, the addition of 3% NP S reduced water absorption by 34%. Shaikh et al. (F. U. A. Shaikh et al., 2015) determined the rate of water absorption with 50 mm thick disk. Natural aggregates were replaced by RCA at 25% and 50%, and nano-silica was included at a dosage of 1% and 2% by weight of cement. It was concluded that the addition of 1% and 2% silica nanoparticles minimized the sorptivity by (12.5%, 35%) and (27%, 32%) in the RAC containi ...
... usion in RAC blends before and after RCA strengthening with nano-silica slurries. The resistance of chloride diffusion was considerably enhanced by about 15% compared to conventional RAC due to the improvement of the ITZ zones, which contributed to the densification of the microstructure and increased the durability of RAC against chloride attack. Shaikh et al. (F. U. A. Shaikh et al., 2015) showed a reduction in chloride diffusion by about 15% and 32% in RAC mixes with 25% RCA replacement ratios by adding silica nanoparticles at 1% and 2%, respectively. Higher RCA replacement rates up to 50% resulted in a reduction of 12% and 28% in blends mixed with 1% and 2% NP S , respectively. Moreover, pre-soaking of RCA in nano slurr ...
The use of recycled aggregates concrete (RAC) contributes effectively to reduce CO2 emissions from concrete manufacturing process while also protecting natural resources by utilizing existing available concrete as an aggregates source for a new one. Studies on the behaviour of RAC have revealed negative effects on concrete strength and microstructure development, resulting in deterioration of mechanical and durability properties. As a result, numerous practical studies have been implemented to enhance the RAC properties using various treatment techniques such as chemical, physical and heating treatments. However, most of these techniques are ineffective compared to conventional concrete applications due to poor mechanical performance of RAC, insufficient environmental requirements, and prolonged treatment times. Recently, the use of nanomaterials has been given significant concern in RAC research. Their nano-sized particles can help to reduce micropores formation by acting as a filling agent to produce a high-density microstructure, thereby enhancing the mechanical properties and durability of RAC. This had led to a wide range of studies being published on improving RAC properties by using nanomaterials. However, relatively few literatures had been conducted on the effects of different types of nanomaterials on the performance of RAC exposed to various types of loads and various external environmental impacts. Besides, the conditions used by authors in these literatures limit comparisons, and in some cases contradictory findings are observed. Thus, this paper aims to bridge the knowledge gap between researchers. This would allow the potential of nanotechnology in innovations to be applied in appropriate areas of RAC applications to benefit the general public good. This paper aims to provide a critical review and comprehensive conclusions on the performance of nano-modified RAC under external loads, environmental impacts and other various conditions. The effects of nanomaterials on the compressive, tensile, and flexural strength of RAC are discussed. The nanomaterials considered are nano-SiO2, nano-CaCO3, nano-TiO2, nano-Clay, nano-Al2O3, and nano-Carbon. Durability characteristics including water absorption, chloride penetration, fire exposure, abrasion resistance, acid and carbonation diffusions are extensively discussed. Microstructure characteristics using SEM, XRD, EDS, and micro-hardness of nano-modified RAC are addressed as well.
... The mechanical and deformation characteristics of concrete might be greatly enhanced by adding nanoparticles to the mix [9][10]. Recent advances in nano-concrete research, particularly in the areas of modified nano-B 4 C and nano-CaCO 3 concrete are main signs of things to come [11][12][13][14]. ...
Static and dynamic characteristics of 3 sort of nano-concrete, 2.0 % nano-B4C, 2.0 % nano-CaCO3, and 2.0 % nano-B4C –1.0 % nano-CaCO3 co-doped concretes, were studied using a 100-mm split Hopkinson pressure bar (SHPB) testing system. There is a clear strain rate consequence for concrete's dynamic compressive strength (DCS) and impact toughness (IT) and energy dissipation (ED) as well as affect failure mode, as shown by the results, which reveal that NC is stronger and has a greater elastic modulus than PC under static load. Even though NC's dynamic elastic modulus increases while its dynamic compressive properties and peak strain all reduction at the same strain rate. There are no significant differences between NS and PC in terms of DCS, peak strain (PS), IT and ED. But whereas NC's static and dynamic mechanical characteristics declined, NSC's are roughly in the middle between PC's and NC, but it has seen an uptick. Nano-CaCO3 has enhanced compactness, decreased weak areas and optimized pore size distribution, whereas nano-B4C has evident internal weak areas and destroyed pore structure.
... Also, aggregate properties have a great impact on the volume of permeable voids of concrete. According to Shaikh et al. [27] volume of permeable pores in concrete containing recycled coarse aggregate was not significantly influenced by nS addition. After the samples were conditioned for 18 days (3 days in a desiccator and 15 days in a sealed container), the test was performed following ASTM C1585-13, with results provided in Figure 5a. Figure 5b shows the calculated initial sorptivity and secondary sorptivity. ...
This paper presents the results of an experimental investigation into the effect of nano-silica addition on the mechanical properties and durability of concrete. Three mixes of concrete containing 0%, 2%, and 4% nano-silica by weight of cement were tested. The slump of fresh concrete as well as compressive strength, dynamic modulus of elasticity at 2, 7, 28, 90, and 180 days, and flexural strength at 2, 28, and 90 days of hardened concrete were determined. As for indicators of concrete durability, the total volume of permeable voids, water absorption, the rate of water absorption, and the freeze-thaw scaling resistance were determined. Test results showed that the incorporation of nano-silica in concrete resulted in an improvement of all mechanical properties of concrete, as well as concrete durability parameters that are tested.
... Also, aggregate properties have a great impact on the volume of permeable voids of concrete. According to Shaikh et al. [27] volume of permeable pores in concrete containing recycled coarse aggregate was not significantly influenced by nS addition. After the samples were conditioned for 18 days (3 days in a desiccator and 15 days in a sealed container), the test was performed following ASTM C1585-13, with results provided in Figure 5a. Figure 5b shows the calculated initial sorptivity and secondary sorptivity. ...
This paper presents the results of an experimental investigation into the effect of nano-silica addition on the mechanical properties and durability of concrete. Three mixes of concrete containing 0%, 2%, and 4% nano-silica by weight of cement were tested. The slump of fresh concrete as well as compressive strength, dynamic modulus of elasticity at 2, 7, 28, 90, and 180 days, and flexural strength at 2, 28, and 90 days of hardened concrete were determined. As for indicators of concrete durability, the total volume of permeable voids, water absorption, the rate of water absorption, and the freeze-thaw scaling resistance were determined. Test results showed that the incorporation of nano-silica in concrete resulted in an improvement of all mechanical properties of concrete, as well as concrete durability parameters that are tested.
... Micro silica (silica fume) belongs to the category of highly pozzolanic materials because it consists essentially of silica in non-crystalline form with a high specific surface and thus exhibits great pozzolanic activity. A new generations of nano silica has been used around the world and has attracted many researchers from different fields due to its high silicon dioxide content and its Nano-size particles (10-9mm) be able to fill the porosity between cement and micro silica particles (Shaikh and Supit, 2014, Jo et al., 2007; Shaikh et al., 2014, [8]; Supit and Shaikh, 2013, [ 9]. Nano silica is a fine amphorous material which t is generally available in the form of an emulsion of colloidal silica. ...
The effect of using Portland cement, nano silica (NS) and /or micro silica on the mechanical and physical properties of concretes containing fine aggregate only is investigated. Two groups divided into five series each have been designed and tested. The first group was containing the nano-silica only, while the second group contained different ratios of nano silica and a constant content of 8 % of silica fume (SF) (by weight) as partial replacement of cement. Water cementations ratio (w/c) of all mixtures was constant and equal to 0.22. The cement content in all series was 800 kg/m3. Commercially available nano silica (NS) was used in the mixture for the partial substitution of cement at ratios of 0, 0.5, 1.0, 2 and 3% by weight. It was found that the addition of nano –silica is significantly enhance compressive, tensile and modulus of elasticity of concrete. From the test results obtained it has been noted that the mix containing 2 % possess significantly improved mechanical properties, furthermore, the group samples of concrete containing binary cementations nano-silica and silica fume showed better results than concrete containing nano silica only.
... The residual materials generated is slag which floats above the iron when iron ore is reduced to iron [117,118]. Frequently this slag is tapped off as a molten liquid and has to be quenched rapidly with a huge amount of water in order to production GGBS [119]. ...
The environmental aspects of sustainable development in the construction industry consist of the utilization of secondary raw materials and materials which can be recycled in the design and construction of new structures. The preliminary and inevitable interest in the use of full or partial replacements of by-products as complementary pozzolanic materials was mostly induced by the enforcement of the reduction/elimination of the greenhouse gas emission from the production of Portland cement. With the significant evolution of geopolymer concrete as an alternative for Portland cement in the past decade, it is necessary to explore possible construction applications in which geopolymer concrete can be utilized. Hence, this review paper was carried out to explore various elements such as the precursors used in geopolymers concrete and their corresponding applications. The environmental impacts of various geopolymer concrete are also discussed. This paper also presents an overview of the real applications of geopolymer concrete for the construction of various infrastructures. Recommendations and prospects for geopolymer concrete are also provided.
... Fig. 13(b) shows the FESEM and EDX of the ITZ in RAC with and without nano-SiO 2 incorporation [237]. Fig. 13(c) further collects of the chloride diffusivity of RAC with various types and replacements of nano-particle [236,[238][239][240][241]. An optimal dosage exists for nanoparticles in RAC. ...
... In addition, the improvement of chloride resistance by nanoparticle modification is more obvious with increasing duration of curing. For instance, the chloride ingress depth in RAC with 1% nano-particle is respectively 4.3% and 13.7% lower than that of RAC without nano-particle incorpora-tion when the curing duration is 7 d and 28 d [240]; this is because the increased duration of curing promotes the activity effect between the nanoparticle and cementitious material. Attributed to the improvement of the pore structure and ITZ performance, the incorporation of nanoparticles further decreases the steel corrosion risk in reinforced RAC exposed to chloride attack conditions, as shown in Fig. 13(d) [242]. ...
... Adapted from Refs. [234,[236][237][238][239][240][241][242]. ...
Chloride ingress and resulting steel corrosion are the main reasons leading to durability degradation and structural failure of concrete. A body of literature on chloride transport and steel corrosion in recycled aggregate concrete (RAC) is currently available, but a systematic review has been lacking. This paper presents a critical review of chloride transport in RAC, and the induced steel corrosion behaviour and cracking patterns of reinforced RAC are introduced. Related modification methods are further discussed. The results showed that the incorporated recycled aggregate (RA) increased chloride ingress in RAC, and a time-dependent characteristic was observed for the chloride diffusion coefficient. The lower RA properties led to higher chloride ingress in preparing RAC when RA substitution rates were the same; the induced environmental damage accelerated chloride ingress in RAC. Incorporating RA increased the steel corrosion risk and shortened the initial corrosion time of reinforced RAC, and the cracking pattern of reinforced RAC was different from the cracking pattern of reinforced natural aggregate concrete. Removing and enhancing the adhered old mortar of RA improve the properties of RAC, and various modification methods can be employed to improve the resistance to chloride ingress and steel corrosion in RAC. In particular, a CO 2-curing treatment, which is eco-friendly, is recommended for improving the RA and RAC properties. The study of chloride ingress and steel corrosion in ultra-high performance RAC and 3D-printed RAC should be a focus in further studies.
... U. A. Shaikh et. al, 2014[39]. , investigated concretes containing recycled coarse aggregate with 25 and 50% by the weight as replacement of coarse aggregate incorporated with 1 and 2% nano silica by the weight of cement for each mix. Both mechanical and durability properties were studied at different ages. ...
This thesis aims to study the effect of using various types of materials as partial replacement of cement on the properties of high strength concrete. Nano SiO2, Nano CaCO3, micro SiO2, micro CaCO3, recycled silica gel (beads and powder) and limestone were used as replacements, all replacements were used with four different contents of 1%, 2%, 3% and 4% by weight of cement. also binary combination of (Nano SiO2 + Nano CaCO3), (micro CaCO3 + micro SiO2) and (recycled silica gel powder + limestone) were applied to investigate their combined effect. Ten groups of concrete mixes were made by progressive cement replacement (micro silica, micro CaCO3, micro silica+ micro CaCO3, nano silica, nano CaCO3, nano silica, + nano CaCO3, silica gel, crushed silica gel, limestone and crushed silica gel) in addition to control mix without replacement so the total mixes were 41 mixes.
Mechanical properties (compressive strength, split tensile strength and flexural strength) were done after 28 days of water curing. Also water absorption test and alkalinity test were carrying out for obtaining the durability properties of concrete specimen, while the workability of all mixes were obtained by applying the slump flow test on fresh concrete. Thermal analysis (TG-Thermogravimetric) and (DTG- Derivative Thermogravimetry) were performed to estimate the CH content for each concrete group. X-ray diffraction and SEM (scanning electron microscope) characterization were achieved to confirm and interpret the results of above tests.
Results of compressive strength tests manifested that the mix with 3% Nano silica showed the maximum enhancement 47.55 % at 3% dosage, followed by micro silica 30.75% at 4% dosage, binary nano mix 26.42% at 3% dosage, crushed silica gel and nano CaCO3 18.86% at 4% dosage, binary recycled mix 11.32% at 4% dosage, silica gel and binary micro mix 9.43% at 4% dosage, micro 7.55% at 4% dosage and finally limestone mix 0% at 4% dosage. Approximately same trend for
III
replacement effect was observed in the results of split tensile strength and flexural strength.
Results of water absorption test revealed that all replacements contributed in the reduction of water absorption due to the densification of concrete microstructure, the maximum reduction were observed in silica gel and crushed silica gel and binary mixes. High alkalinity (PH) value was recorded for concrete mixes, a slight dropping in this value was recognized after using replacements, and the maximum drop was found with Nano mixes. Calcium hydroxide (CH) content results depicted the lowest value with nano silica mix followed by binary nano mix and crushed silica gel mix, while other mixes exhibited approximate values but all of them were less than the control mix, this indicated larger amounts of calcium silicate hydrate (CSH) gel formed after employment of replacement which has contributed mainly to improving the strength and durability of concrete.
SEM (scanning electron microscope) micrographs displayed the presence of calcium silicate hydrate (CSH), Calcium hydroxide (CH) and Ettringite phases, which are evidence of the completeness of the hydration process, same results were confirmed from the X- ray diffraction analysis. A result of tests showed that silica series mixes (nano silica, micro silica, silica gel and crushed silica gel) had a higher affirmative effect on the properties and durability of high strength concrete than CaCO3 series (nano CaCO3, micro CaCO3, limestone).
