Powder Concrete Research Articles

Preparation and Properties of g-C3N4-TiO2 Cement-Based Materials Supported by Recycled Concrete Powder

In this paper, recycled concrete powder (RCP) is used as the carrier of g-C3N4-TiO2 instead of natural minerals. The prepared g-C3N4-TiO2/RCP composites were characterized by X-ray diffractometer, scanning electron microscope, infrared spectrometer, specific surface area analyzer, UV-visible spectrophotometer, and RhB solution degradation experiments. The results show that the rough, porous structure of RCP was beneficial to the stable load of g-C3N4-TiO2. Under the condition that the content of g-C3N4-TiO2 catalyst is constant, the agglomeration of g-C3N4-TiO2 can be reduced by using RCP as a carrier, thus improving its photocatalytic efficiency. Subsequently, g-C3N4-TiO2/RCP was loaded onto the surface of cement-based materials by coating bonding method to study its photocatalytic performance. It is found that the photocatalytic cement-based material has a similar degradation effect on the degradation of surface RhB as g-C3N4-TiO2/RCP in RhB solution. Our work may open up a new field for the recycling of RCP and provide new ideas for the development of photocatalytic cement-based materials.

Effect of belite-rich cement replacement on the properties enhancement of eco-friendly ultra-high performance concrete containing limestone powder and slag

Cement-slag-limestone (CSL) powder concrete is a new type of ternary concrete. Thus far, CSL powder application in ultra-high performance concrete (UHPC) remains relatively limited. Furthermore, the effects of different types of cements, including belite-rich Portland cement (BRC), on CSL concrete have not been investigated. Therefore, in this study, a new CSL-UHPC was designed, where the sustainability of CSL-UHPC was systematically improved by using BRC to replace the ordinary Portland cement (OPC) in CLS cementitious materials and realize a UHPC with a low heat of hydration, low autogenous shrinkage, low CO2 emissions, and high strength. According to the experimental data, the heat released by the hydration reaction during the early stages of BRC concrete was less than that released in the early stages of OPC concrete. The cumulative heat release from hydration and the maximum heat release rate were minimal, approximately 171.8 J/g and 1.41 mW/g of the binder, respectively, for 100% BRC replacement. Moreover, the autogenous shrinkage generation in the early stages was effectively reduced; notably, the reductions autogenous shrinkage were particularly pronounced (approximately 39.5–36.7%) for 66% and 100% BRC replacement. After 56 days of curing, the compressive strength of the BRC-infused concrete was similar to or higher than that of OPC concrete. In addition, the CO2 emissions and the CO2 emissions per unit strength decreased by 2.6–7.8% and 7.0%, respectively, as the percentage of BRC replacement increased. Thus, CSL-UHPC combined with BRC is more effective than OPC in terms of promoting a sustainable concrete industry.

Multi-scale characteristics of magnesium potassium phosphate cement enhanced by waste concrete powder

Using recycled concrete powder (RP) as an alternative binder can effectively reduce construction and demolition waste and contribute to developing eco-friendly repair materials. However, the effect of RP on magnesium potassium phosphate cement (MKPC) has not been sufficiently studied. In this study, MKPC pastes were prepared by replacing different contents of MgO with RP, and the evolution of the structural behavior was explained from nanoscale to microscale. The results show that incorporating an appropriate amount of RP can increase the fluidity and setting time of the MKPC mixture and improve its mechanical properties. The drying shrinkage and water resistance of MKPC specimens also improve with the increasing RP content. Incorporating an appropriate amount of RP can refine the pore structure of MKPC samples, while the generation of gel-like products can compensate for the adverse effects of reduced struvite-K content. The nanoscale characteristics of the MKPC samples also indicate that incorporating RP results in a decrease in the residual MgO and pore phase content, an increase in the content of the hydrated phase, and a decrease in the loss of the hydrated phase volume fraction due to water soaking. Upon optimizing the RP content, the MKPC mixture exhibits a lower cost and carbon footprint, with the 28-d compressive strength of the sample mixed with 10% RP increased by 7.36% relative to the plain sample, indicating that recycling RP is feasible in an eco-friendly MKPC system.

A Study on the Application of Recycled Concrete Powder in an Alkali-Activated Cementitious System

In this paper, recycled concrete powder (RCP) was used as a supplementary cementitious material (SCM) in an alkali-activation system. The contents of RCP in the cementitious materials were 0%, 10%, 20%, 30% and 40%, respectively. The fluidity, rheological properties and mechanical properties were tested, while the effects of RCP on the hydration properties of the alkali-activated system were studied by XRD, SEM-EDS, thermogravimetric analysis and the heat of hydration. The results show that the addition of RCP improves the fluidity of alkali-activated slag cementitious materials and changes the rheological index of paste. The change is greatest when the RCP content is 30%, which is 8.5% higher than that without RCP. With the increase in RCP content, the compressive strength of alkali-activated slag cementitious materials first increases and then decreases. The optimum compressive strength was attained with an RCP of 10%. The addition of RCP has little effect on the types of alkali-activated hydration products, but increases the quantity of hydration products. Further, the inactive particles in RCP combine with hydration products to form a dense microstructure. The addition of RCP reduces the early and total hydration heat of alkali-activated slag cementitious material, and delays the emergence of the second exothermic peak after the first peak.

Performance of asphalt mortar with recycled concrete powder under different filler-to-asphalt weight ratios

The feasibility of using recycled concrete powder (RCP) as fillers in asphalt mortar is investigated in this study, to achieve a sustainable and economical asphalt production. The differences in physical properties between limestone powder (LSP) and RCP are analyzed and compared. Moreover, the interactions of LSP and RCP with asphalt are studied as well. The properties of asphalt mortar studied include ductility, softening point, penetration, viscous and elastic behaviors of asphalt mortar. Compared to LSP, the RCP presented a rougher surface, additional pores, more complex pore structures, larger Brunauer, Emmett and Teller (BET) surface areas, and smaller particle size. At 0.6 and 0.9 of filler-to-asphalt weight ratio (F/A), the RCP is more effective for the performance enhancement of asphalt mortar compared with the LSP. When the F/A is 0.9 and LSP is completely replaced by RCP, the 15 °C penetration index (PI) and ductility of asphalt mortar decrease by 9.3% and 29.2% respectively. The softening point increases by 5.4%. By contrast, the RCP causes a considerable decrease in PI, equivalent brittle point (T1.2) and ductility when F/A ratio is 1.2. After RCP completely replace LSP, the PI, T1.2, and ductility of asphalt mortar decrease by 47.1%, 44.0%, and 29.0%, respectively. However, at F/A of 0.6, the asphalt mortar with 100% RCP replacement ratio presented both acceptable ductility and plasticity. Under the same temperature and F/A, the complex shear modulus G* and rutting resistance factor G* /sinδ of asphalt mortar raise with the increase of RCP replacement, which indicates that the RCP can better enhance the high-temperature rutting resistance of asphalt mortar than the counterpart LSP. It also implies that the modification of LSP and RCP in asphalt mortar mainly depends on the physical interactions rather than the chemical reactions.

Study on the Influence of SAP on Properties of White Fair-Faced Concrete with Limestone Powder

Introducing SAP internal curing material and limestone powder into white fair-faced concrete in order to greatly improve the durability of white fair-faced concrete, alleviate the influence of mechanical property deterioration caused by SAP, and facilitate the popularization and application of SAP and limestone powder in white fair-faced concrete. Therefore, this paper studies the effect of the content of SAP and limestone powder on the properties of white fair-faced concrete, conducts slump, electric flux, standard cube compressive strength, and splitting tensile strength tests, and examines SAP and limestone powder from a macroscopic perspective. The effect of the dosage on the properties of white, fair-faced concrete was explained by a scanning electron microscope (SEM) from a microscopic point of view. The results show that SAP can increase the slump of white fair-faced concrete, and the slump of SAP white fair-faced concrete increases with the addition of limestone powder content. Adding SAP can greatly reduce the electric flux of white fair-faced concrete. The addition of limestone powder can further reduce the electric flux and improve the durability and adding SAP will deteriorate the mechanical properties of white fair-faced concrete. Adding limestone powder is beneficial to the improvement of the mechanical properties of SAP mixed with white fair-faced concrete. Adding 30% limestone powder can give full play to the optimal performance of SAP white fair-faced concrete. SAP can refine the internal structure of white fair-faced concrete, and the filling and nucleation effects of limestone powder can improve the situation where SAP deteriorates the mechanical properties of white fair-faced concrete, further optimizing concrete internal structure.

Development of low carbon and energy-efficient geopolymer-based paving blocks

The development of energy-efficient and low-carbon geopolymer-based paving blocks made from waste, as an environmental-friendly material, was evaluated. Ground concrete (GC) and solid brick (SB) powder, as the representatives of construction and demolition waste (C&DW), with the addition of fly ash (FA) and silica fume (SF), were used. Waste samples were characterized in terms of surface functional groups and radioactivity. The FT-IR spectra showed the required amorphous or semi-crystalline alumino-silicate structure. The gamma spectrometry confirmed waste samples' radiological safety. Hardened geopolymer samples were subjected to physical-mechanical investigation comprising of density, water content, compressive and flexural strengths determination. Based on strength characteristics, the three best prototype mixtures were selected and subjected to further compressive strength determination and durability assessment. Prototype sample SBFASFp1, with a compressive strength of 18.7 MPa, was shown the highest value of all samples, almost the same as the corresponding SBFASF1 sample. Freeze-thaw and the subsequent carbonation tests, as durability indicators, showed that the SBFASF1 sample had the slightest strength decrease, making it most durable in these conditions. These satisfactory test results showed the favorable effects of alternatives to cementitious materials, encouraging their utilization and contributing to the sustainability of the construction sector.

Study on Partial Replacement of Cement and Coarse Aggregate by Egg Shell Powder and Steel Slag in Concrete

Abstract: In this research, eggshell powder (ESP) was used as a partial substitute for cement in concrete to decrease the usage of cement in concrete production. The main objective of the study was to determine the workability and reinforcing properties including compression, tensile and flexural strength of concrete using various percentages (0, 10, 20,&10) of ESP by weight instead of cement. A total of 38 concrete samples were cast (12 cubic meters, 12 cylinders and 12 prisms) with a target strength of 28 N/mm2. The compressive strength of a cube sample (150 × 150 × 150 mm) was tested after 7, and 28 days, while tensile strength were also measured for 7 days and 28 days using a cylindrical specimen (200 × 100 mm). The bending strength of the specimen (100 x 100 x 500 mm), cast during 7, and 28 days of curing. The test results showed that during the. With ESP 20%, tensile strength increased by 30%, and a maximum strength of 20% was obtained using ESP 20% during 28-day cure. As the percentage of ESP increases, the workability of fresh concrete decreases. ESP is used in concrete to enhance the power of a concert. Natural aggregates are becoming scarce and their production and shipments is also becoming more difficult. The main objective of this study is to identify alternative source of good quality aggregates which is depleting very fast rate due to the fast pace of construction activities in India and to improve the workability and durability of concrete. Use of steel slag as a waste industrial which is the by-Product of iron and steel production provides great opportunity to utilize it as an alternate to normally available coarse aggregates. In this study concrete of M30grade for a w/c ratio of 0.45 respectively for the replacement of 10%,20% and 30% of coarse aggregates by steel slag which is produced as a waste material in steel industry and has a negative impact on environment when disposed. The investigation reveals that the steel slag could be utilized as coarse aggregate in all the concrete applications and shows a considerable improvement in the compressive strength of concrete over the control mixes by 7 to 8%. Results show that the concrete incorporating steel slag has higher compressive strength and an increase in density and stability was clearly observed in the specimens replaced with steel slag as coarse aggregate

Chloride corrosion resistance of cement mortar with recycled concrete powder modified by nano-silica

In the marine environment, the service life of coastal structures can be significantly reduced on account of chloride corrosion. This study employed nano-silica (NS) to improve the chloride corrosion resistance of mortar samples prepared with recycled concrete powder (RCP). The free chloride ion concentration and mechanical strength of mortar samples in 3.5% NaCl solution up to 12 months were measured. Rapid chloride migration (RCM) and electric flux experiments were carried out. Compared with the pure RCP mortar, the 2% NS incorporated RCP mortar experienced a significant decrease in the chloride ion diffusion coefficient, electric flux and corrosion rate of internal rebar. Moreover, the RCP mortar with 2% NS also had the slowest increase in the free chloride ion concentration and surface chloride ion concentration. The addition of RCP in cement mortar reduced the chloride corrosion resistance, while the inclusion of 2% NS compensated for the RCP induced degradation, resulting in an improvement in chloride corrosion resistance. The X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) results showed that the addition of RCP and NS consumed Ca(OH)2 to generate more C-S-H gels and C-A-S-H gels and thereby improved the physical chloride-binding ability of the sample. In addition, the formation of Friedel’s salt via the combination of chloride ion with aluminosilicate further improved the chlorine ion corrosion resistance.

Researching the Use of Marble Powder in Self-Compacting Light Concrete

Bu çalışmada, doğal kaynaklarımızdan biri olan Nevşehir bölgesine ait asidik pomza agregası ile Kırşehir bölgesinden elde edilen endüstriyel atık olan atık mermer tozunun kullanılması sonucu kendiliğinden yerleşen hafif beton üretilmesi amaçlanmaktadır. çimento ikame malzemesi olarak farklı oranlarda (%0, %5, %10 ve %15). Çalışma sonucunda fiziksel ve mekanik olarak kendiliğinden yerleşen hafif betondan üstün bir yapı malzemesi elde edilmesi hedeflenmiştir.
 
 Bu kapsamda, kendiliğinden yerleşen hafif betonların taze ve sertleşmiş özellikleri araştırılmıştır. Taze beton özelliklerini belirlemek için; taze beton birim ağırlık, çökme-yayılma, V hunisi, L kutu ve U kutu testi ve taze beton birim hacim ağırlık testi yapılmıştır. Sertleşmiş beton özelliklerini belirlemek için su emme, kuru birim ağırlık testi, basınç dayanımı testi, yarmada çekme dayanımı testleri uygulanmıştır.
 
 Çalışma sonucunda; %15 mermer tozu kullanımının uygun olacağı kendiliğinden yerleşen hafif beton üretiminde kullanılmasında bir sakınca olmadığı belirlenmiştir. Mermer tozu gibi endüstriyel atıkların beton üretiminde kullanılması hem çevre kirliliği hem de sürdürülebilirlik açısından önemlidir.

Recycling Old Concrete as Waste Concrete Powder for Use in Pervious Concrete: Effects on Permeability, Strength and Eco-Friendliness

The fine portion of crushed old concrete is difficult to be recycled for use in new concrete because it contains old cement paste, which generally has high porosity and low strength. Hence, in practice, the coarse portion is recycled as coarse aggregate and the fine portion is mostly not recycled. Nevertheless, attempts have been made in recent years to recycle the fine portion as waste concrete powder (WCP) by grinding before use. In this research, WCP was used to make pervious concrete. The WCP was added using the paste replacement method (PR method) of replacing an equal volume of cementitious paste. A series of pervious concrete mixes containing 100% recycled coarse aggregate and having different amounts of WCP added were produced for testing of interconnected porosity, water permeability and strength. The results showed that the addition of WCP using the PR method can improve the interconnected porosity by 9% and water permeability by 18%, greatly enhance the strength by 86%, as well as decrease the cement consumption by 10% at the same time. Therefore, the addition of WCP as paste replacement has great potential to be applied to the production of eco-friendly high-performance pervious concrete.

Recycled concrete fine powder (RFP) as cement partial replacement: Influences on the physical properties, hydration characteristics, and microstructure of blended cement

Construction and demolition (C&D) waste has caused various economic, environmental, and social problems. This paper investigates the potential of recycled concrete fine powder (RFP) as a supplementary cementitious material. The effect of RFP with different replacement levels on the properties of cement and the mechanism of action were explored from the physical characteristics, mechanical properties, hydration kinetics, hydration products, and pore structure. In this study, scanning electron microscopy, Energy Dispersive X-Ray Spectroscopy, X-ray diffraction, X-ray fluorescence, Thermogravimetric analysis, and Isothermal calorimeter were applied. The results showed that RFP (less than 30%) shortened the setting time and improved the fluidity of cement. The early compressive strength increased by 17.62% of the cement mortar with 10% RFP. When the RFP content was 10%, the flowability of the blended slurry (175.5 mm) increased by 8.0% compared to the pure cement (162.5 mm). With the RFP content increase of the blended cement, the hydration induction period was prolonged, and the peak hydration exothermic rate and the accumulated heat release showed an apparent decreasing trend. The reaction rate of the nucleation and crystal growth (NG) process was much higher than that of the interface (I) and diffusion (D) processes. The low field nuclear magnetic resonance (NMR) technique revealed that RFP filled the large and medium pores of the mortar. The non-destructive layered scanning found that the pores were distributed mainly in the central zone and had a gradient distribution law of gradually decreasing from the middle area to the edge area. Visual analysis of the dynamic distribution of water molecules in the pores and the non-homogeneous characterization also demonstrated the good filling effect of RFP on the mortar. Therefore, RFP can be used as an economical and environmentally friendly cement mixing material to replace partial cement and contribute to reducing carbon emissions in the construction industry.

Simulation and Experimental Substantiation of the Thermal Properties of Non-Autoclaved Aerated Concrete with Recycled Concrete Powder

Non-autoclaved aerated concrete (NAAC) is a two-phase material with a concrete matrix and air, exhibits good thermal insulation performance and shows good potential in the insulating construction industry. In this study, recycled concrete fine powder was used as an auxiliary cementing material, and the NAAC with different porosity and distribution was fabricated by the non-autoclaved method at different curing temperatures. The effect of porosity on the thermal conductivity and mechanical strength of NAAC is analyzed by experimental tests. A prediction method of thermal conductivity combining pore structure reconstruction and numerical simulation was proposed, which is established by two steps. Firstly, the pore size distributions of NAAC with different porosities were characterized by stereology image analyses. Secondly, the thermal conductivity prediction model based on the pore structure information was established by a COMSOL steady-state heat transfer module. The thermal conductivity results of COMSOL simulations were compared with the experiments and other theoretical models to verify the reliability of the model. The model was used to evaluate the effect of porosity, pore size distribution and the concrete matrix's thermal conductivity on the thermal conductivity of NAAC; these are hard to measure when only using laboratory experiments. The results show that with the increase in curing temperature, the porosity of NAAC increases, and the number and volume proportion of macropores increase. The numerical results suggest that the error between the COMSOL simulations and the experiments was less than 10% under different porosities, which is smaller than other models and has strong reliability. The prediction accuracy of this model increases with the increase in NAAC porosity. The steady thermal conductivity of NAAC is less sensitive to the distribution and dispersion of pore size in a given porosity. With the increase in porosity, the thermal conductivity of NAAC is linearly negatively correlated with that of the concrete matrix, and the correlation is close to 1.

Effect of thermo-mechanical activation of waste concrete powder (WCP) on the characteristics of cement mixtures

The objective of present study is to utilize and study the reactivity and hydration behaviour of thermo-mechanically activated waste concrete powder (WCP). For activation, the WCP was burned for 2 h at 650 °C, followed by mechanical grinding through ball milling. The reactivity of the activated WCP was improved significantly, as corroborated through the Chapelle test, hydration analysis and compressive strength analysis. Different blends were prepared with 10 to 40 % OPC replacement. Activated WCP was found to be effective in enhancing the reactivity of cement mixtures for all replacement proportions and developed comparable compressive strength in comparison to OPC. At 56 days, the application of activated WCP resulted in the developed of 75.5 % better compressive strength than the application of as received WCP. Mineralogical analysis exhibited the development of more secondary C-S-H gel with the formation of calcite at the later age. Using lifecycle analysis software, the replacement of 40 wt% of OPC with activated WCP was calculated with 37.6 %, 39.8 % and 19.7 % less CO2 emissions, less mineral resources consumption and less energy consumption, respectively.

Utilizing nano-SiO2 for modifying the microstructure, strength and transport properties of sustainable cementitious materials with waste concrete powder

Using waste concrete powder as an alternative binder in green cementitious materials contributes to reduce the number of construction and demolition waste, and developing an effective method to modify the performance of waste concrete powder blended cementitious materials is necessary. The influences of nano-SiO2 at 0–3% dosage on cementitious materials containing waste concrete powder as partial cement replacement (0–50%), under a ratio of 1:2 for both water-to-binder and binder-to-sand, were investigated in this study with the aspects of micro-structure and macro-performance. The results illustrated that mixing waste concrete powder negatively impacted the hydration reaction and micro-structure of cement paste; however, the mix of nano-SiO2 promoted the secondary hydration reaction and refined pore diameter of waste concrete powder mixed paste. Mixing nano-SiO2 raised the drying shrinkage but reduced the water loss of paste including waste concrete powder. The replacement of cement by waste concrete powder caused the reduction in compressive strength of paste. But at a fixed substitution level of waste concrete powder in paste, the compressive strength rose with the increment of nano-SiO2 content up to 3%. The transport properties rose as waste concrete powder was incorporated in mortar, but the mix of nano-SiO2 significantly reduced the transport properties of waste concrete powder incorporated mortar. Particularly, the effects of nano-SiO2 addition on the decrease in water absorption became more distinct as high content of waste concrete powder was blended. Optimizing the content of waste concrete powder and nano-SiO2 can obtain green cementitious materials owning good strength and low transport properties.

Numerical study on flexural and bond-slip behaviours of GFRP profiled-concrete composite beams with groove shear connector

GFRP profiled-concrete composite beams with groove shear connectors are analyzed using finite the element (FE) analysis. The concrete damaged plasticity (CDP) model was adopted for normal strength concrete (NSC) and reactive powder concrete (RPC). The orthotropic behaviour of GFRP profile was taken into consideration, and the bi-linear traction-separation model was used to investigate the bond-slip behavior between GFRP profile and concrete. Furthermore, parametric studies were conducted to investigate the effects of strength and the cross-sectional dimensions of concrete, strength (orthotropy), and the cross-sectional dimensions (the web height and the thickness of FRP plate). Numerical analysis results correlate well with experimental results. Based on numerical analysis, the composite beam with shear connectors spacing at 100 mm has a deflection-limit load of 21.4 % higher than the specimens with 150 mm spacing. It is possible to improve the bonding behavior of interfaces by using groove shear connectors. The ultimate load and deformation, and pseudo-ductility were significantly improved by using RPC with high strength and toughness (ultimate compressive strain). GFRP profiles with greater orthotropy coefficients provide fully utilized concrete's compressive strength, preventing premature crushing and enhancing composite structure stiffness. Flexural performance of the composite beams can be improved efficiently by choosing the appropriate sectional size during design and construction.

Orthogonal experimental and theoretical study on mechanical properties of fiber-reinforced recycled powder concrete

With the goal of "low cement, low cost, high environmental protection and high performance", building solid wastes are applied to concrete manufacture. This study investigated the mechanical properties of fiber-reinforced recycled powder concrete (FRPC) by orthogonal test, and optimized the mix proportion of FRPC. The research variables included water-binder ratio, sand-binder ratio, the volume content and aspect ratio of basalt fiber (BF), and recycled concrete powder (RCP) replacement rate. The results showed that the ductility of FRPC is the best when the replacement rate of RCP is 45%. The mechanical properties of FRPC are the best when the volume content of BF is 0.1% and the aspect ratio is 1059. A trilinear model and constitutive equation of tensile stress-strain curve of FRPC were proposed. Additionally, the microscopic mechanism of fibers in FRPC was analyzed by scanning electron microscope (SEM).

Bonding mechanism of botanical concrete: Microstructural changes between waste concrete powder and wood

An in-depth understanding of the bonding mechanism of botanical concrete (BC) can facilitate its development and improve its performance. For this purpose, six hot-pressed BC samples comprising mixtures of wood with concrete powder, carbonated concrete, and sand were prepared in this study. The effects of individual and synergistic interactions in the prepared mixtures on the microstructure during hot-pressing were investigated. Fourier transform infrared spectroscopy, solid-state cross-polarization/magic angle spinning 13C nuclear magnetic resonance, X-ray diffraction, and thermogravimetry analyses revealed the absence of such interactions. Only self-degradation of concrete and wood was observed, and the alkalinity of concrete waste favored BC bonding. Furthermore, principal component analysis indicated that the effect of the alkalinity of concrete on wood was more significant than that of temperature. These results indicate that combining BC with alkaline industrial wastes or novel geopolymers can improve its applicability.

Economical and eco-friendly masonry mortar containing waste concrete powder as a supplementary cementitious material

Research on the feasibility of using waste concrete powder (WCP) as a replacement for cement in mortar production is available in the literature. However, the WCP-mortar related studies are centered on the material characterization and the performance of the mortars. For sustainability purposes, the mortars should provide the required strength as well as the economic and environmental benefits. Hence, the aim of this study is to evaluate the properties of cement masonry mortar containing WCP, along with their economic and environmental advantages. In the experimental study, mortars were prepared by replacing ordinary Portland cement (OPC) with WCP in various fractions of 0%, 15%, 30%, 40%, 60%, 75%, and 100% by mass. The influence of WCP on the fresh and hardened properties of the mortars was examined. It was found that the strengths of the masonry mortars were reduced significantly as the quantity of WCP increased, yet mortar mixtures containing 40–75% WCP met the strength criteria for masonry mortar. Also, using WCP resulted in tremendous reductions in the cost and environmental factors of the mortars. In conclusion, the mortars provided the specified strength requirement for masonry work as well as economic and environmental gains, making them sustainable.

Effect of waste concrete powder on slag-based sustainable geopolymer composite mortars

In this study, the effect of waste concrete powder (WCP) on slag-based geopolymer composite mortars was investigated. Blast furnace slag (BFS) and WCP were used as binders in geopolymer mortars. WCP was substituted into the geopolymer mortar composites at rates of 10%, 20%, 30%, and 40% by weight of slag. Sodium hydroxide (NaOH) solution was used as the alkali activator in the mixtures and the solution activator concentration was chosen as 16 molars (M). After the prepared mortars were cured at 100°C for 24 hours, they were subjected to flexural strength (ffs), compressive strength (fcs), and ultrasonic pulse velocity (UPV) tests. When the obtained results were examined, it was observed that ffs, fcs, and UPV results decreased with the increase in WCP replacement ratio. These decrements were seen clearly, especially after the 20% replacement ratio. However, despite these decrements, the compressive strengths of all groups were found to be above 50 MPa. In addition, it is thought that environmental pollution can be reduced by using WCP in geopolymer composite mortars.