Replacement Of Natural Fine Aggregate Research Articles

Evaluation of tire rubber surface pre-treatment and silica fume on physical-mechanical behavior and microstructural properties of concrete

The increasing accumulation of tire waste has become a social environmental and public health problem because rubber degradation is extremely difficult to achieve and time consuming. The incorporation of rubber waste in concrete has become a recourse to assist in the disposal of this solid waste. This investigation evaluated the influence of a chemical pretreatment with sodium hydroxide solution (NaOH) on the physical, mechanical, microstructural properties of concretes with two rubber residue contents (15% and 30%) as a natural fine aggregate replacement, and the addition of silica fume (7.5% and 15%) to replace Portland cement. X-ray microtomography and scanning electron microscopy were used to investigate the influence of treatment rubber and silica fume in the microstructure of concretes. The use of rubber in the cement matrix, regardless of the treatment (or lack thereof), decreases the concrete density (lower 10.5%) and compressive strength at 28 d (54%), besides the increase the porosity (18%) than reference concretes. The rubber pre-treatment did not significantly influence the concrete behavior. In contrast, the use of silica fume showed significant compressive strength gains, up to 80% for concretes with 30% of rubber replacement at 28 days. These gains were confirmed by the microstructural analysis and the densification of the interfacial transition zone.

Effect of Mill-Rejected Granular Cement Grains on Healing Concrete Cracks.

The effect of mill-rejected granular cement (MRGC) on enabling concrete to autogenously heal its cracks was investigated. The crack-healing efficiency of concrete containing 5%, 10%, 15%, and 20% wt. of MRGC as a replacement for natural fine aggregate was investigated at the age of 28 days. Concrete specimens were induced with artificial cracks and placed in water or air at 20 ± 2 °C to cure and heal the cracks for an additional 28 days. Compressive, flexural, and tensile strengths and water permeability tests were carried out to evaluate crack-healing by evaluating the strength to regain and the reduction in water permeability of concrete. For the air-cured specimens, the gain in compressive strength was between 45% and 79%, the flexural strength was between 74% and 87%, and the tensile strength was between 75% and 84% of the reference specimens for the MRGC content was between 0% and 20%, respectively. For the water-cured specimens, the gain in compressive strength was between 54% and 92%, the flexural strength was between 76% and 94%, the tensile strength was between 83% and 96% of the reference specimens for the MRGC content between 0% and 20%. The water permeability coefficients of the concrete specimens cured in water after cracking decreased by one order of magnitude, while those of the specimens cured in the air increased by the same order of magnitude. The crack-healing efficiency of concrete could be enhanced by increasing the MRGC content of concrete and hydration water.

Utilization of Pyrolytic Carbon Black Waste for the Development of Sustainable Materials

The sustainable development of materials is one of the key targets in the modern era of engineering. These materials are developed by different waste products, following the concept of the circular economy. This study focuses on investigating the properties of concrete using carbon black as a partial replacement of natural fine aggregate at different percentages. Experiments were designed according to the British Standard (BS1881-Part-119) and American Standard (ASTM C-78) by including carbon black in concrete beams to perform as filler material to develop sustainable concrete. In this study, mechanical properties of concrete were targeted by developing beams using different percentages (0%, 25%, 50%, 75%, and 100%) as a replacement of fine aggregates. These beams were tested for flexural strength and, later on, the same beams were cut in the form of cubes, following the equivalent cube test mechanism for the compressive strength test. The waste carbon black lightweight concrete developed in this study was utilized for both structural and non-structural purposes. At 25% and 50% replacement, the strength of lightweight concrete varied from 20–18 MPa, and according to American Concrete Institute (ACI) standards, lightweight concrete at 28 days strength with ≥17 MPa can be used as structural concrete, and the remaining 75% and 100% replacement concrete can be used for non-structural purposes. This study will help in the development of economical eco-friendly sustainable concrete materials.

A Critical Review on the Influence of Fine Recycled Aggregates on Technical Performance, Environmental Impact and Cost of Concrete

The aim of this critical review is to show the applicability of recycled fine aggregates (RFA) in concrete regarding technical performance, environmental impact, energy consumption and cost. It is not possible to judge the performance of concrete by considering one dimension. Thus, this study focussed on the fresh and hardened (e.g., mechanical and durability) properties and environmental and economic life cycle assessment of concrete. Most literature investigated showed that any addition of recycled fine aggregates from construction and demolition waste as a replacement for natural fine aggregates proves detrimental to the functional properties (quality) of the resulting concrete. However, the incorporation of recycled fine aggregates in concrete was proven to enhance the environmental and economic performance. In this study, an extensive literature review based multi criteria decision making analysis framework was made to evaluate the effect of RFA on functional, environmental, and economic parameters of concrete. The results show that sustainability of RFA based concrete is very sensitive to transportation distances. Several scenarios for the transportation distances of natural and recycled fine aggregates and their results show that only if the transportation distance of the natural aggregates is more than double that of RFA, e the RFA based concrete alternatives would be considered as more sustainable.

Leaching behavior of copper slag aggregate cement-mortar by atomic absorption spectroscopy (AAS)

Leaching behavior of copper slag aggregate cement mortar was analysed using atomic absorption spectrometry (AAS)with different mix proportion immersed in two aqueous fluids: conventional water and ammonia nitrate solution. Four types of cement-mortar mix i.e. M-type, S-type, N-type and O-type were cast with constant water/cement ratio to study the leaching effect with total replacement of natural fine aggregate with copper slag. Compressive strength test of hydraulic cement-mortar along with sorptivity test of all cement-mortar mix was also conducted. Experimental results of leaching study showed minimal leaching of copper slag incorporated cement-mortar for all proportion after 95 days of subjection to two aqueous fluids. Improved compressive strength was observed for all types of cement-mortar mix and also found to be increased with higher curing age. Rate of water absorption was found to be decreased with increased content of copper slag in cement-mortar for all mix proportion.

Recycled microbial mortar: Effects of bacterial concentration and calcium lactate content

This study investigated the optimum bacterial concentration and calcium lactate content in mortars containing recycled concrete aggregate (RCA) as full replacement of natural fine aggregate (NFA) for the first time. For this purpose, bacterial mortars with cells concentration of 103, 105 and 107 cells/ml were prepared. Calcium lactate was used as the organic precursor at dosages of 1%, 3%, and 5% of cement weight. The mechanical, durability, crack healing, and microstructural characteristics of the bacterial mixes were examined and compared to those of the control mix. The results indicated that incorporating bacterial cells with concentration of 105 cells/ml treated with 1% calcium lactate led to the optimal mix. The 28-day compressive strength of the optimal mix increased by 21% over that of the control mix. The lowest water absorption was also recorded for this mix, which was about 7% lower than that of the control mix. The scanning electron microscopy (SEM) images of the optimal mix showed a dense and compact microstructure as a result of calcite precipitation, which filled the air voids and reduced the pore size. Increasing the calcium lactate content lowered the quality of the pore system due to overproduction of calcium carbonate (CaCO3) crystals. This was confirmed by the results of porosimetry test using mercury injection method where the sample prepared with 5% calcium lactate and bacterial concentration of 103 cells/ml showed 450% higher total porosity as compared to the control sample. On the other hand, crack healing analysis revealed that the maximum healing in surface cracks occurred at the maximum bacterial concentration and calcium lactate content.

The Structural Performance of RCC Beams Made With M30 Grade SCC Mix While Fine Aggregate Is Partially Replaced By Crystal Stones

The economy of a developing country depends to a great extent on the construction industry. Developing countries like India are investing heavily in infrastructure development. The excessive exploitation of natural resources for construction threatens the sustainability of aggregates and poses a number of serious problems. At the same time, the disposal of fly ash and stone residues in landfills cause several environmental crises and pollute the environment. This article deals with a study on the structural behavior of the partial replacement of fine natural aggregates by 0 -40% crystal stones in order to obtain the flow properties of fly-ash-based self-compacting concrete (SCC) by using super plasticizers. Many tests have been done to test the feasibility of using crystal stones in M30 grade SCC. On the basis of the results obtained, the optimum percentage of fine aggregates with crystal stone was calculated at 30% and it was concluded that the increasing percentage of crystal stone replacement by fine aggregates did not affect its workability. The structural performance of simply supported RCC beams of size 150 × 200 × 1500 mm made from SCC with crystalline stone was tested.

Flow behavior, microstructure, strength and shrinkage properties of self-compacting concrete incorporating recycled fine aggregate

The present research investigates the behavior of flowable concrete by reusing the construction and demolition (C&D) waste to replace natural resources. It gives an insight into the feasibility and effectiveness of developing an eco-friendly self-compacting concrete (SCC) using recycled fine aggregate (RFA) with maximum cement replacement. This study aims at evaluating the flow behavior, mechanical strength, shrinkage characteristics and the microstructure of SCC ascertaining the synergistic effect of RFA with the binary or ternary blend binder as a partial substitution of cement. From performance point of view, it is observed that the presence of RFA enhances the flowability, but certainly affects the other flow attributes to a certain extent with time at a higher replacement level. The interaction between RFA particles and the fluid media to maintain the flowability and to achieve the functional requirements of SCC have also been explored. It is found that the desired flow could be achieved for all the SCC mixes based on three independent variables (water absorption kinetics, SP and VMA dosage) by maintaining the powder content constant. The target strength is achieved for all the mixes except the mix with 40% fly ash and 100% RFA. This study reveals that the stability of the resulting SCC made with RFA can be acquired by properly designing the fluid media, considering the material properties. However, the complete replacement of natural fine aggregate with RFA has significantly influenced the performances of SCC and so with binary blend binder.

Abrasion Resistance of Manufactured Sand (MS) Concrete and Its Influence Factors

The feasibility of using MS to replace river sand (RS) in concrete pavement has been widely concerned by scholars, however the abrasion resistance of MS concrete pavement serves as a major factor restricting application. Published literature shows huge potential of MS as a replacement of natural fine aggregate. A detailed overview of published literature on property of MS and influencing factors on abrasion resistance of MS concrete is being presented. Regarding the characteristics of MS, the granular shape is characterized by irregular shape, multi-angle and large aspect ratio, the gradation shows a phenomenon of less in the middle and more on both ends, and MS contains high content of stone powder and little mud powder. The influencing factors include mix ratio, lithology, stone powder, admixture, polymer, etc. Among them, stone powder has attracted the attention of many scholars. Nevertheless, few related studies exist at present, source selection and in-depth research merit consideration.

Performance of Various Pozzolanic Materials on Shear and Impact Strength of Concrete made with Partial Replacement of Natural Fine Aggregate by Manufactured Sand

Nowadays concrete is the widely used construction material in civil engineering field because of its extraordinary strength and durability. The over-utilization of cement and natural sand for civil industry has several undesirable social and ecological consequences. As an answer for this, industrial wastes called as by-products (pozzolanic materials) such as fly ash, GGBFS, silica fume and metakaolin can be used to interchange partially cement and natural fine aggregate by manufacturing sand (M-sand). This research aims to investigate the possibility of replacing natural fine aggregate by M-sand and with 20% of above pozzolanic materials substitute in concrete. In this experimentation, natural fine aggregate was partially replaced by M-sand in various percentages (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%), with water cement ratio of 0.45 and cement was partially substituted by 20% of pozzolanic materials. M30 concrete grade proportions were considered as per IS 10262:2019 guidelines. The shear strength and impact strength results were checked for the different concrete mix proportions and compared with conventional concrete. From this research work, it is concluded that for partially replacing of 60% natural fine aggregate by M-sand and 20% cement by silica fume yields maximum shear and impact strength than conventional concrete.

Use of iron ore mine tailings in infrastructure projects

Utilisation of iron ore tailings in bricks as a replacement for sand will help in sustainable and greener development. The literature shows the potential use of iron ore tailings as a replacement of natural fine aggregates. As natural sand reserves are depleting day by day, there is a need for substitution for sand in bricks. A comprehensive overview of the published literature on the use of iron ore tailings and other industrial waste is being presented. The effects of various properties such as compressive strength, thermal conductivity and durability of bricks have been presented in this paper.

Validation of carbonation behavior of self compacting concrete made with recycled aggregates using microstructural and crystallization investigations

The sustainable binary and ternary blends of Self compacting concrete (SCC) were prepared with replacement of natural fine aggregates (NFA) and natural coarse aggregates (NCA) with recycled fine aggregates (RFA) and recycled coarse aggregates (RCA) respectively sourced from construction and demolition (C&D). Accelerated carbonation tests were conducted using conventional acid/base method. The results indicate that with the increase in RFA and RCA content as replacement of NFA and NCA, decrease in the carbonation resistance of SCC has been observed. The addition of Metakaolin (MK) has been found in recompensing the respective loss in carbonation resistance up to some extent. For validating the results, microstructural and crystallization studies have been performed with the help of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. In addition to above, compressive strength tests were also conducted for reference.

Strength and Chloride Diffusion Behaviour of Three Generations of Repeated Recycled Fine Aggregate Concrete

The feasibility of using different generations of recycled fine aggregate (RFA) in structural concrete in a chloride environment was evaluated by studying the performance of the RFA and the corresponding concrete. The different generations of RFA were recycled by following the cycle of ‘concrete - waste concrete - fine aggregate - concrete’. The properties of three generations of repeatedly recycled fine aggregate (RRFA) were systematically investigated, and we focused on the compressive strength and splitting tensile strength and chloride ion permeability of the related structural concretes with 25%, 75%, and 100% replacement of natural fine aggregates with RFA. The results indicated that the quality of RRFA presents a trend of slow deterioration, but the overall performance of all RRFA still fulfils the quality requirements of recycled fine aggregate for structural concrete. All RRFA concretes achieved the target compressive strength of 40 MPa after 28 days except for the second generation of the recycled aggregate concrete and the third generation of the recycled aggregate concrete with 100% replacement, and all the concrete mixes achieved the target compressive strength after 90 days. The insights obtained in this study demonstrate the feasibility of using at least three generations of RRFA for the production of normal structural concrete with a design service life of 100 years in a chloride environment.

Influence of RAP aggregates on strength, durability and porosity of cement mortar

The influence of fine fraction of Reclaimed Asphalt Pavement (RAP) aggregates on mechanical, durability and porosity characteristics of cement mortar was studied when the same was used as a replacement of Natural fine aggregates (NA) at 25%, 50%, 75% and 100% by volume. The stipulated 28-day characteristic compressive strength was achieved by mortar mixes with 25% and 50% of RAP content. Porosity, determined through Mercury Intrusion Porosimetry (MIP), increases with RAP content and existing strength – porosity models (Hasselman D.P.H, Balshin M.Y, Ryshkewitch E. and Schiller K.K.) holds good. Drying shrinkage of RAP mortar mixes showed erratic behavior, whereas partially replaced mixes (25% and 50%) showed increase in compressive strength under sulfate attack.

Resistencia al impacto de hormigón armado con fibra de basalto de alta resistencia

There is an increasing quest for sustainable development in the built environmental through the use of alternative construction materials. Basalt fibre is one of those materials that is currently gaining interest in concrete production, because it is environmentally friendly, and also has good mechanical features. The current study evaluates the workability, strength properties, impact resistance and hydration characteristics of high strength chopped basalt fibre-reinforced concrete. Basalt fibre was used in varying proportions, and manufactured sand was used as a total replacement of natural fine aggregate, while other natural materials were kept constant, when casting concrete specimens. The results showed that increasing the cut length of basalt fibre could enhance the strength characteristics and impact resistance of concrete. Overall, the study revealed an improved impact resistance in the tested concrete, which could be traced to be a result of rapid hydration.

Use of recycled aggregates in road sub-base construction and concrete manufacturing

This paper investigates the use of construction and demolition waste in road embankment and concrete manufacturing. The aggregates are recycled from the demolition waste of a building and in particular from basalt, sandstone, structural concrete and vibrated concrete blocks. The main physical characteristics of recycled aggregates for road applications and the performance of road sub-base layers containing recycled components are determined and validated on the basis of the latest Italian specifications. The study demonstrates that recycled mixes have sufficient mechanical characteristics and are hence suitable in road sub-base construction, even if only limited to minor technical importance works. Moreover, the mechanical properties of concrete mixtures that use recycled aggregates as replacement for natural aggregates are evaluated and compared to those of standard concrete mixtures. Three types of recycled aggregates are considered (structural concrete, basalt, vibrated concrete blocks) at different replacement ratios. A higher percentage of recycled aggregates than the one prescribed by the current legislations can be effectively used in concrete preparation, especially in the case of aggregates derived from crushed basalt waste or from structural concrete manufactured using basaltic fine and coarse aggregates. The effect of natural fine aggregate replacement with recycled fine fractions on concrete is investigated. The results of the experimental program are significant and encourage the use of 100% recycled basalt aggregate in concrete. Therefore, in areas where the use of basalt stone as primary masonry building material is widespread, the reuse of demolition waste is highly recommended.

Resonant column testing on Portland cement concrete containing recycled asphalt pavement (RAP) aggregates

This study deals with material properties of Portland cement concrete (PCC) made with aggregate that is replaced with recycled asphalt pavement (RAP). A series of PCC mixtures were produced and tested in uniaxial compression using RAP aggregate as substitute of fine and coarse natural aggregate. The main variable was the percentage content by weight of RAP aggregates in the concrete mixture. Both fresh and hardened properties of concrete were examined. Moreover, a relatively new non-destructive technique (free-free resonant column – FFRC) was used to measure concrete’s elastic modulus. The experimental results indicate that the compressive strength and the elastic modulus decrease with increasing RAP aggregate replacement, while all mixtures containing RAP aggregates remain workable. Additionally, the replacement of fine natural aggregates has a more pronounced effect on the examined properties. Finally, the FFRC can provide good estimation of elastic modulus.

Properties of mortar with waste clay bricks as fine aggregate

In order to solve the problem existing in the utilization of fine recycled aggregates from crushed bricks (RCBA), the replacement of natural fine aggregate (NA) by RCBA to produce a new green recycled mortar is an important technology to develop renewable resource products and realize waste resources recycling. In this paper, in order to deeply understand the mechanism of RCBA, macroscopic and microscopic tests are carried out to study the influence of RCBA with different replacement ratios, particle sizes and additional water contents on the flowability, compressive strength and flexural strength of mortar. And the physical properties, chemical composition, mineral composition and microscopic morphology of RCBA are analyzed. The results show that the porous structure of the waste clay bricks together with the secondary mechanical crushing treatment result in the decline of the physical properties of RCBA. The fully additional water content in RCBA is beneficial to improve the flowability of mortar, but the partially additional water content in RCBA has an adverse impact. In addition, the RCBA with partially additional water content and particle size of 0–5 mm is beneficial to the improvement of mortar strength. However, the RCBA with fully additional water content and particle size of 0.15–5 mm is detrimental to the development of mortar strength. The microscopic test indicates the rough surface and pozzolanic activity of RCBA produce relatively stable and dense interfacial transition zone between the RCBA and cement paste.

Economical graphene reinforced fly ash cement composite made with recycled aggregates for improved sulphate resistance and mechanical performance

The paper reports the incorporation of graphene into fly ash cement mortars at different doses (% by weight of cement) and evaluation of compressive and flexural strength and resistance to sulphate attack of composites at different hydration times. Fine recycled aggregates (FRA) from have been used as total replacement of fine natural aggregates (FNA) in mortars. Compressive strength and flexural strength results showed that 0.05% graphene produced maximum increase of 8% and 13% respectively with respect to FNA mortar. Excellent resistance to sulphate attack in 0.05% graphene composite could be achieved with minimum loss in compressive strength of 21%.

Influence of recycled fine aggregate on microstructure and hardened properties of concrete

The objective of this work was to investigate the effect of commercially produced recycled fine aggregate (RFA) on the compressive, tensile and microstructural behaviour of recycled aggregate concrete (RAC). The effect of RFA as a substitute for natural sand at various volume replacement levels (0, 25, 50, 75 and 100%) on the compressive strength, splitting tensile strength and flexural strength of RAC was studied. For 100% replacement of natural fine aggregate (NFA) by RFA, the compressive, splitting tensile and flexural strengths were found to decrease by 13·51, 6·46 and 22·62% respectively. Microstructures of a control concrete and concrete made with RFA (RFAC) were compared, and scanning electron microscopy observations showed that the RFAC contained more unhydrated cement particles and more voids, and its calcium silicate hydrate gel was less dense than that observed in the concrete made with NFA.