Percentage Of Substitution Research Articles

A novel modelling approach for realistically-wrapped state recycled aggregates and its application in meso-scale tensile behaviour simulation of recycled concrete

Most of the existing Finite Element (FE) simulations on the mechanical behaviour of Recycled Aggregate Concrete (RAC) generally simplified the Recycled Aggregates (RAs) as simple shapes (e.g., circular / elliptical and polygonal), with residual mortar created by proportional scaling or segmentation of these shapes, which is not consistent with the real situation. Hence, this study proposed an irregular shapes overlay method and a placement algorithm to randomly generate the real-shaped RAs and build the RAC’s mesoscale geometric model. Then, RAC’s mesoscale FE model was established based on the cohesive zone model and got calibrated. The effects of various key parameters (i.e., the RAs substitution percentage, the residual mortar content of substituted RAs and the relative strength of residual to new mortar) on the RAC’s tensile behaviour were studied. The proposed framework can effectively generate RAC’s mesoscale geometric models with various RAs substitution percentages and residual mortar contents. Embedding zero-thickness interface elements between all solid elements can perfectly simulate the RAC’s crack development under tensile loading, offering more realistic cracking paths compared to RAC with simple shape RAs. For the case of new mortar strength larger than the residual one, the tensile strengths of RAC decrease as the RAs substitution percentage and residual mortar content, with a reduction of up to 15%. Otherwise, the tensile strengths show no significant decrease.

Potential for material valorization of composites (glass fiber in polyester resin) in concrete: performance evaluation on mortar

IntroductionGlass fibers with polyester resin structural composites are highly sought after in many sectors such as transportation industries, thanks to their low density and fairly good mechanical properties. However, their end-of-life management is not yet satisfactory. Composites mostly end in energy recovery in the best-case scenario or, worse, in landfills. Transformation into shreds and powders for reuse as a new source of raw material for the construction sector (concrete) is an economically and environmentally attractive recovery solution. The present study investigates the development of a concrete filled with glass/polyester composite shreds.MethodsTo this end, rheological (cone spread) and physico-mechanical (density and mechanical strength in flexion and compression) characterization tests were carried out. Several mix designs were tested in order to understand the impact of introducing composite shreds as a substitute for sand. Composite shreds were introduced in the following ratios by volume: 0, 1, 1.5, 2, 2.5, 3, and 7% with water and cement ratio equal to 0.5, 0.6, and 0.7.Results and discussionThe results obtained indicate that workability decreases with the substitution of sand by shreds. For a substitution of sand by shreds of 2%, it is relatively small, and the pouring of the mortar is still feasible. The decrease can be attributed to the water absorption of the composite shreds. Concerning mechanical results, for formulations with a substitution percentage of composite shreds lower than 3%, the mechanical strength (both compression test and flexure test) is slightly higher than that of the reference sample. The increase in compressive strength that can be observed is at its maximum, equal to 10%, compared to that of the reference sample. These results are in line with density results, which are also slightly higher than that of the reference sample. This effect can be attributed to water absorption of composite shreds and the filling effect of the powders. For a percentage of substitution equal to 7%, the mechanical strength is lower than that of the reference sample (30% decrease), with a compressive strength equal to 33 MPa (47 MPa for the reference sample). For this percentage of substitution equal to 7%, a decrease in density is also observed (6% decrease) and can be explained by the porosity created by the incorporation of the composite shreds into the mortar.

Recycling of RAP (Reclaimed Asphalt Pavement) as aggregate for structural concrete: experimental study on physical and mechanical properties

The replacement of natural aggregate in concrete with artificial and/or recycled one has recently gained attention as meaningful strategy to reduce the environmental impact of structural concrete and promote circular economy principles. This study investigated the possibility to use Reclaimed Asphalt Pavement (RAP), in the “as received conditions”, as a partial or complete substitution of natural aggregate for structural concrete. RAP aggregate was firstly characterized in terms of grain size distribution, density, assessment of fines, chloride content, moisture content and water absorption. Subsequently, a total of twenty-four concrete mixes were designed, considering two cement types, two w/c ratios and several aggregate substitution percentages. For each mix, properties at the fresh and hardened state were investigated, such as workability, density and total open porosity, compressive strength, dynamic modulus of elasticity, and electrical resistivity. Results showed that RAP has a good potential to be used in reinforced concrete, provided that different water absorption and moisture content are considered in the mix design. RAP concrete was characterized by a lower density and increased total open porosity; however, an accurate tailoring of the concrete recipe could compensate the strength loss for several applications. Other properties, such as electrical resistivity and the relationship between dynamic modulus of elasticity and compressive strength did not result significantly altered by the presence of RAP.

An Experimental Investigation on Nano-Enhanced Tertiary Blended Concrete Incorporating Industrial Wastes

Concrete is a crucial material in the construction industry; however, its production process releases carbon dioxide into the atmosphere. Undoubtedly, the building sector's increasing global interest unveils a challenge to its ability to withstand cement alternatives and manage the resulting outflows. Fly ash, GGBS (ground granulated blast furnace slag), Zeolite, rice husk, silica fume, metakaolin, and various industry by-products can typically replace cement. This research study aims to replace cement with multiple cementitious materials, individually and in combination, to evaluate the strength characteristics of blended concrete. The replacement percentages ranged from 0 to 30% for each substitute material, such as fly ash, GGBS, and Zeolite, and strength tests were done to assess the performance of the modified concrete after 7 and 28 days of water curing. Ordinary Portland Cement (OPC) is used to create M30 and M50 grades of concrete. Similarly, cement was replaced with fly ash, GGBS, and Zeolite in amounts ranging from 10 to 30% for M30 and M50 grades, and their strength was evaluated after 7 and 28 days of curing. The most efficient percentage of substitution for both the concrete grades is determined, and the corresponding replacement ratio is used to produce the blended concrete, which incorporates cement, fly ash, GGBS, and Zeolite. The overall findings reveal that the composite concrete, comprising four binding materials, demonstrated superior strength for the concrete grade compared to alternative substitutes. The optimal mixture ratios for M30 concrete after 28 days consist of 20% fly ash, 20% GGBS, and 10% zeolite. Moreover, different ratios of Zeolite-10%, Fly-Ash-30%, and GGBS-20% were used to produce M50 concrete.

Hydrothermal and mechanical performance of mortars containing waste brick powder

It is widely recognised that green building, environmental sustainability, and technical performance have recently become requirements in the field of civil engineering. For this reason, the new trend in research is to focus on the recycling and recovery of materials, even if some of them such as industrial waste are still underexplored. In this perspective, the main objective of this work is to study the influence of brick powder on the thermophysical and mechanical properties of mortars containing this type of waste, in different environments, and within the temperature range between ambient temperature and 50 °C. To this end, a number of mortar mixtures, in which cement was replaced by brick powder in different proportions, were studied and characterised according to technical standards in order to define the optimal substitution percentage. Three batches of samples were examined at different ages, i.e., 3, 7, 28, and 90 days. The samples of the first batch were kept in water at a temperature of 20 ± 2 °C with a relative humidity RH = 100 %, while those of the second batch were immersed and stored in water at 50 °C in order to simulate a hot and humid climate. As for the samples of the third batch, they were kept in a dry oven at 50 °C in order to investigate the effect of the hot and dry climate. The results obtained revealed that the partial replacement of cement by brick powder makes it possible to improve the thermal insulation characteristics but reduce the mechanical strength of the mortar. In addition, it was shown that in a hot and dry environment, the mechanical characteristics of the different mortars decrease as the rate of weight substitution of cement by brick powder rises. However, in a hot and humid environment, a reverse trend is observed. The findings also suggested that the optimal recommended rate of substitution of cement by brick powder is 20 %.

Changes in the physical, chemical and sensory properties of pasta made by partially substituting wheat flour with black glutinous rice flour

Black glutinous rice flour (BGRF) had the potential to be used as a wheat substitute to increase the health-promoting nutritional value of pasta products. The purpose of this study was to investigate the possibility of using BGRF as an alternative to wheat flour in the production of pasta to improve its nutritional value. The research explored the physical, chemical, sensory properties, and consumer acceptance of pasta formulations with 0%, 20%, 40%, and 60% BGRF substitution. The findings revealed that pigmentation of BGRF contributed to increased phenolic compounds and antioxidant properties, which impacted physical and chemical properties of the pasta. The results indicated that a 40% substitution of BGRF was well-liked by consumers, while a 60% substitution led to decreased acceptance. The physical properties of uncooked pasta (UC-PAS) and cooked pasta (CK-PAS), such as moisture content and color values, were significantly influenced by the percentage of BGRF substitution. Specifically, the moisture content of UC-PAS decreased with higher BGRF substitution, resulting in changes in color values. These changes included an increase in redness, as well as a decrease in lightness and yellowness. Additionally, the pigmentation of BGRF contributed to increased phenolic compounds and antioxidant properties, which affected physical and chemical properties of the pasta. The pasta’s cooking quality, including cooking time (CKT), cooking loss (CKL), and cooking yield (CKY), also showed significant differences with varying percentages of BGRF substitution. Furthermore, the proximate composition indicated that the percentages of ash, protein, fat, and fiber increased as the proportion of BGRF increased, with pasta containing 60% BGRF demonstrating the highest values for these properties. All these findings provide evidence that BGRF substitution had a significant positive impact on the physical, chemical, and sensory properties of pasta. For example, the pasta had better antioxidant properties and was well-accepted by consumers. The potential for enhancing the nutritional profile of pasta products by substituting wheat flour with BGRF is noteworthy. Key words: black glutinous rice, wheat, rice flour, pasta, antioxidant, bioactive compounds

Comparative analysis of long-term and high temperature performances of OPC based high strength mortar and silica fume based high strength geopolymer mortars

The effects of Class C fly ash (FA) contents on the performance of silica fume (SF) based high strength geopolymer mortars (HSGM) subjected to high temperatures up to 1000 ºC are investigated. The percentages of FA substitution by SF are 10 %, 15 %, 20 % and 25 % by weight. The alkali activators used consist of sodium silicate (SS) and sodium hydroxide (SH) and are used in mixtures with SH/SS ratios of 0.3, 0.4, 0.5 and 0.6. In order to compare SF based HSGMs, ordinary Portland cement (OPC) based high strength mortar (HSM) as a control mortar is also produced with the same dosage and water content. The results at environmental temperature show that higher mechanical properties are obtained from SF based HSGMs compared to OPC based HSM. The optimum replacements of Class C FA and SH/SS ratios are 15 % and 0.3 or 0.4 in terms of mechanical properties. At 28 days, SF based HSGMs with flexural strength (ffs) of 15 MPa and compressive strength (fc) of 100 MPa can be produced without thermal curing. High reductions in the mechanical properties are seen on the OPC based HSM and SF based HSGMs subjected to high temperatures. In addition, SF based HSGMs with fc values above 25 MPa can also be obtained after exposure to 1000 ºC. Alterations in the microstructure of OPC based HSM and SF based HSGMs under the influence of high temperatures are also examined with XRD, FTIR, SM, and FESEM/EDX analyses. Particularly, a spongy structure with volumetric expansion is seen with the formation of the glassy phase in the matrix of SF based HSGMs subjected to a temperature of 1000 °C.

Pemanfaatan Abu Cangkang Kopi Sebagai Substitusi Semen Untuk Bahan Beton Ringan Menggunakan Bahan Tambah Sikament NN

The chemical reaction of cement and water produces compounds that are alkaline and react with various acids so that they can reduce the quality of concrete. To minimize this effect, pozzolanic materials need to be added. Organic pozzolan materials such as coffee shell ash waste can be used as material for making lightweight foam concrete which can be applied to non-structural buildings such as lightweight bricks. This research was conducted to see the effect of coffee shell ash substitution for cement on the properties of fresh concrete and the mechanical properties of lightweight foam concrete and to find the most optimal substitution composition for coffee shell ash for cement as well as lightweight foam concrete with FAS 0.5. Substitution of coffee shell ash for cement weight was carried out with variations of 0% BBN, 5% BBAAK1, 10% BBAAK2, and 15% BBAAK3 using 1% superplasticizer additive. The test object used is a cylinder with dimensions of 15 cm x 30 cm. The number of test objects used was 24 pieces. Tests for compressive strength and split tensile strength were carried out at the age of 28 days. The results of compressive strength tests carried out at 28 days for the lightweight foam concrete variations BBN, BBAAK 1, BBAAK 2 and BBAAK 3 were respectively 15.29 MPa, 12.21 MPa, 18.29 MPa and 19.52 MPa. The greater showing variation in the percentage of coffee shell ash substitution used, the greater the resulting compressive strength and split tensile strength values. This is because Sikament NN also plays a role in increasing the compressive strength of concrete

Impact of the partial substitution of cement and sand by ash from several types of wood species in cementitious materials manufacture: valorization in the industrial field

The main objective of this article is to evaluate the potential use of wood ash as a substitute for cement and sand in mortars. Three types of wood were selected: Ayous, Sapelli and Fraké, all of which were sourced from carpentry in Cameroon. The sawdust was dried and combusted to obtain ash, then ground and sieved. Six types of mortar were produced, with cement substitution at 0%, 5%, 10%, 15%, 20% and 25%. The physico-mechanical properties of these substitutions were determined after 7, 28 and 56 days. The results of the cement paste consistency show that it increases with the addition of ash, due to the fact that sawdust ash requires a large quantity of water. The addition of ash caused an increase in setting time due to the fact that sawdust ash is less reactive than Ordinary Portland cement, resulting in a delay in the rate of cement hydration. Apparent density values decreased with the addition of sawdust ash, probably due to the hygroscopic behavior of type of ash in mortar specimens. The highest pozzolanic index is that of 5% replacement by ash and almost identical absorption for all mortars at this substitution percentage. Acid attack results revealed a higher durability of mortar specimens with the higher percentage of ash substitution. Optimum compressive strengths for the different substitution percentages were observed at 5%, 15% and 10% respectively for Ayous, Sapelli and Fraké. The best wood ash is Sapelli because of its chemical composition and resistance to compression in mortars. At 56 days, compressive strength values exceed those of the reference composition. This may be due to pozzolanic reactions in the mortars of ash.

Effects of replacing fishmeal with Spirulina platensis powder on the Zig-zag eel (Mastacembelus armatus): Growth performance, flesh quality, digestibility, and gut microbial composition

Protein demand from aquaculture exacerbates environmental pressures. Zig-zag eel (Mastacembelus armatus, MA) is a new aquaculture species in southern China and has great potential for future promotion. In this study, we used Spirulina platensis powder (SPP) to replace 0–20 % of fishmeal in the feed, respectively. A 10-week aquaculture experiment was conducted on 600 MAs with five groups of F0 (0 %), F1 (5 %), F2 (10 %), F3 (15 %), and F4 (20 %) set up with equal nitrogen (approximately 50.00 % crude protein) and equal fat (about 5.50 % crude fat) feeds. The experimental results showed that replacing fishmeal with different proportions of SPP significantly reduced FCR (p < 0.05), increased WGR and SGR (p < 0.05), and reduced the feeding cost, with the best performance in F2. Polynomial analysis combining WGR and SGR showed that the optimum percentage of substitution was 10.93 % and 11.09 % in MA diets, respectively. The addition of SPP significantly reduced the levels of EPA and DHA content (p < 0.05), significantly increased the proportion of C14:0, C16:1, C20:5n3, and C22:6n3 (p < 0.05), and a high proportion of SPP addition significantly decreased saturated fatty acid content (p < 0.05). The length of intestinal villi and the secretion levels of Chymotrypsin and Pepsin were significantly increased (p < 0.05), and the secretion level of Lipase was significantly decreased (p < 0.05) in the experimental group. A low percentage of SPP increased microbial diversity in MA’s gut. Functional pathways related to metabolic functions were the most obvious broad groups with the most significant changes in relative abundance in the experimental group, and Plesiomonas and Aeromonas may be the key microorganisms involved in regulating the digestion and metabolism of SPP in the gut of MA.

Investigation of the static constitutive relationship of rubberized self-compacting concrete after high-temperature exposure

Rubber self-compacting concrete (RSCC), recognized as an environmentally friendly material, possesses excellent resistance to impact. However, the inclusion of rubber particles significantly decreases its compressive strength. This study investigated the compressive properties of RSCC with rubber particles substituting for fine aggregate volume percentages of 0 %, 10 %, 20 %, and 30 % after exposure at 25, 300, 600, and 900 °C for 3 h. The interface conditions among the rubber particles and the mortar were examined using scanning electron microscopy (SEM). The findings reveal that: (1) Both the compressive strength and the modulus of elasticity of RSCC exhibit a pronounced decline as the exposure elevates, with the maximum reduction reaching 84.25 % and 89.42 % respectively (where the substitution percentage of rubber particles is 30 %), compared to values at room temperature. Conversely, the peak strain exhibited an increase of 130.41 % (with the substitution percentage of rubber particles being 30 %). (2) As the substitution percentage of rubber particles increases, the decline in RSCC's compressive strength and elastic modulus after cooling at elevated temperatures is less noticeable than at room temperature, and the peak strain of RSCC exhibits negligible increase after being subjected to high temperatures. (3) Prediction equations and constitutive models for the compressive strength and peak strain of RSCC post-high temperature exposure are proposed in light of the experimental data. The comparison shows an obvious connection between the experimental outcomes and the predictive results.

Investigation of Physical-Mechanical Properties and Microstructure of Mortars with Perlite and Thermal-Treated Materials.

This study aimed to obtain and characterize a mortar with perlite aggregate and thermal-treated materials that could substitute for Portland cement. First, the thermally treated materials were obtained by calcinating old Portland cement (OC-tt) and concrete demolition waste (CC-tt) at 550 °C, for 3 h. Second, plastic mortars with a perlite: cement volume ratio of 3:1 were prepared and tested for water absorption, mechanical strength, and thermal conductivity. The microstructure was also analyzed. Portland cement (R) was partially substituted with 10%, 30%, and 50% OC-tt. Thermal-treated materials negatively influenced the compressive and flexural strengths at 7 and 28 days. With an increase in the substitution percentage to 50%, the decrease in the compressive strength was 40% for OC-tt and 62.5% for CC-tt. The presence of 10% OC-tt/CC-tt positively influenced the water absorption. The thermal conductivity of the tested mortars was in the range of 0.37-0.48 W/m·K. SEM analysis shows the expanded perlite pores remained unbroken.

Hydrochar production through co-hydrothermal carbonization of water hyacinth and plastic waste

Abstract The global expansion of the economy and concerns about greenhouse gas emissions and climate change necessitate the exploration of sustainable alternatives to fossil fuels. Water hyacinth (WH) is globally recognized as one of the most problematic aquatic weeds, posing significant challenges to urban management by clogging waterways, polluting water sources, and causing harm to ecosystems. However, water hyacinth is enriched with hemicellulose, cellulose, and lignin, making it a noteworthy and superior biomass resource. Hence, this study focuses on the hydrothermal carbonization of water hyacinth into a renewable fuel source, the hydrochar. Hydrothermal treatment was implemented in this work as it can treat wet biomass, in this case, the water hyacinth, without the need of energy-extensive drying process. Plastic waste (PW), or more specifically low-density polyethylene (LDPE), was added as the co-feedstock during the HTC process with the purpose to boost the higher heating value (HHV) of the end product. The co-hydrothermal carbonization (co-HTC) process of the mixture of WH and PW at various ratios and temperatures were conducted to investigate the optimal HTC condition for high hydrochar yields. As the result, the highest hydrochar yield of 29.23 wt% was obtained with 12.5% LDPE substitution percentage, at 200 °C after a holding time of 90 min. However, in term of energy recovery efficiency (ER), the highest efficiency (27.28%) was achieved with 12.5% LDPE substitution percentage at 260 °C. The HHV value of the hydrochar produced in this work is in the range of 17.71-24.69 MJ/kg. In summary, the co-HTC of WH and LDPE could definitely be a promising alternative to bridge the gap from solid waste to renewable fuels.

Experimental study on fiber-reinforced cement tailings sand-based grouting material preparation and factors influencing the grouting effect

To address the problem of permeation of tailings pond initial dams rockfill dams, fiber-reinforced cement tailings sand-based grouting (FRCTG) material, which can be used for rockfill dam reinforcement, was prepared by selecting ordinary portland cement (OPC), iron tailings sand (ITS), basalt fiber (BF), fly ash (FA) and water as the raw materials. Orthogonal tests were used to investigate the effects of the water-binder ratio (w/b) and material mass fraction on the rheological and mechanical properties of FRCTG and determine the optimum mixing ratio. Comparative analyses were performed of the grouting effect of FRCTG and pure OPC grouting materials based on concrete self-compacting tests and COMSOL simulations. Combined X-ray diffraction (XRD) and scanning electron microscopy-energy spectroscopy (SEM-EDS) microstructural characterization were used to reveal the factors influencing FRCTG mechanical properties. The results showed that when the water-binder ratio (w/b) was 0.5, ITS substitution percentage for OPC was 10 %, BF dosage was 0.2 %, BF length was 6 mm, and FA substitution percentage for OPC was 8 %, FRCTG had better rheological properties and flexural strength than pure OPC grouting materials. In addition, FRCTG self-compacting concrete also had stronger compressive strength and splitting strength. FRCTG showed a better filling capacity and diffusion effect, which preliminarily verified the feasibility of rockfill dam grouting. ITS inhibited the hydration reaction of the cementitious material and prolonged the setting time of the slurry. The interlocking structure formed by FA and hydration products indirectly enhanced the flexural strength of the grouting material. BF not only provided FRCTG reinforcement but also acted as the hydration product skeleton. FRCTG demonstrated better economic and environmental performance than traditional cement material while effectively utilizing ITS and FA solid waste.

Evaluation of the addition of cassava flour fermented with lactic acid bacteria on the sensorial and nutritional properties of a baked product

Due to the existing uncertainties regarding the fermentation of non-traditional flours with lactic acid bacteria for the partial replacement of wheat flour in baked products, this research focused on evaluating the substitution of 10 %, 15 % and 20 % of wheat flour in white bread with cassava fermented dough. Cassava flour was fermented with L. plantarum at a concentration of 1 × 106 CFU/g for 32 h at 32 °C. This dough was added in different percentages of partial substitution to a baked product to analyze its impact on the sensory and nutritional properties. The results reveal a more balanced proximate composition in those supplemented products, obtaining a higher amount of protein, fiber and ash, as well as better physical properties such as hardness. Sensory evaluation shows no significant difference, indicating that the sensory properties were not affected in a statistically significant manner after the replacement. Therefore, fermenting cassava flour is advantageous for wheat flour substitution in baked products.

Internal Curing Utilising Recycled Concrete Aggregate: A Sustainable Approach for Improving High-Strength Concrete’s Performance

AbstractHigh-strength concrete (HSC) makes up the vast majority of materials used in the construction sector due to its exceptional mechanical characteristics and outstanding long-term behaviour. However, in cement-based materials with a low water-to-binder ratio (w/b), excessive autogenous shrinkage has become a prevalent issue. This work suggests the sustainable use of recycled concrete aggregate (RCA) to internally cure HSC in order to reduce autogenous shrinkage during the hydration and curing processes. RCA was employed with various volumetric replacement percentages with natural coarse aggregate as a water storage agent (0%, 8%, 16%, 24%, 32%, 50%, 75%, and 100%) under sealed and unsealed conditions. The efficiency of the adopted materials for internal curing was investigated by determining the autogenous shrinkage in addition to unconfined compressive and flexural strength. The laboratory results reveal that the studied properties significantly improved by incorporating RCA into HSC, and the improvement depends on the substitution rate of the coarse aggregate. A better shrinkage behaviour can be obtained by raising the substitution percentage of coarse aggregate with RCA; in contrast, the strengths decrease with increased RCA. RCA can be utilised as an internal curing material for HSC to alleviate autogenous shrinkage with a percentage of around 40%, with the adopted ambient conditions in the early age of HSC with full replacement of virgin coarse aggregate. It is recommended to use 24% RCA as a substitution for natural coarse aggregate for internal curing to improve the characteristics of HSC and the sustainability advantages and reduce its negative environmental impacts.

Reemplazo del Agregado Fino por Residuo de Ladrillo Refractario en Concreto Expuesto a Elevadas Temperaturas

Refractory brick waste, added to the fires originated in structures, makes it possible to bring together two problems to contribute to sustainable construction and introduce new aggregate alternatives in concrete. The objective of the study was to produce concrete with less fine aggregate and to evaluate a more sustainable concrete, using refractory brick residues (RBR) to replace fine aggregate in five percentages 10 %, 20 %, 30 %, 40 % and 50 % to be exposed to direct fire. The design was based on a water-cement w/c ratio of 0.71 and the production of 144 RBR-based concrete specimens. The fresh samples were subjected to slump and fresh unit weight tests, the cylindrical specimens prepared after 28 days of curing were subjected to compressive strength at room temperature and various temperatures (200 to 1 000 °C) for different times of 15, 30 and 60 minutes. In addition, a Three Factor statistical analysis of variance was performed with respect to the compressive strength at 28 days. The results showed that the RBR influences the concrete mix are less workable and reduce the fresh unit weight at higher substitution percentages. On the other hand, the ideal dosage was with the percentage of 40RBR as opposed to the other dosages subjected to heat, being insignificant at 15-minute exposure, but relevant at 30 and 60 minutes. It is concluded that RBR significantly influences the improvement of its mechanical properties under high heat and the amount of residues is limited to a specific dosage, providing a sustainable constructive approach to direct controlled fire exposures.

Effect of incorporating biomass bottom ash and construction and demolition waste powder on the physical-mechanical properties and micro-structure of ternary-blended mortars

Biomass bottom ash (BBA) and construction and demolition waste (CDW) are two waste types whose recycling requires immediate actions due to the high quantities in which they are generated worldwide. Since the cement industry is currently facing a real challenge on a global scale due to the environmental cost implicit in cement production, the objective of this study was to evaluate the possibility of reusing those wastes as an addition in ternary-blended eco-cements with a lower impact than common cements. To achieve this, the chemical, physical, mechanical and micro-structural characterisation of the pastes and mortars manufactured with substitution percentages of 10–40% and 1:1 ratio was carried out. The results showed that the mixture of biomass bottom ash and construction and demolition waste powder in the same proportion had the capacity to fix lime and that the new ternary-blended eco-cements made with 20%, 30% and 40% substitution can be classified as CEM IV/A or CEM IV/B pozzolanic cements pursuant to the EN 197–1 standard. All of the new eco-cements also met the regulatory requirements for initial setting time and soundness, with no workability problems recorded. Finally, the mortars made with cement substitutions up to 20% developed similar or greater compressive strength and presented lower porosity at a later age than the reference mortar, making them suitable for use in construction.

Effect of the Incorporation of Olive Tree Pruning Sawdust in the Production of Lightweight Mortars

In order to reduce energy consumption in buildings, this study used olive pruning sawdust (OTPS) instead of natural sand in the production of lightweight mortars. Different percentages of natural sand substitution were tested: 0, 10, 25, and 50% by volume of sand over 7 and 28 days of curing time. Additionally, the influence of a chemical pretreatment in an aqueous solution of calcium hydroxide on the OTPS was also evaluated to mineralize the wood before its addition to the mortar mixture. Mortars with OTPS incorporations were characterized by volumetric shrinkage, bulk density, and capillary water absorption. Mechanical behavior was tested through compression and flexural tests. The addition of this byproduct decreased bulk density and increased mortar porosity. Pretreating olive pruning sawdust with an aqueous solution of calcium hydroxide was effective for wood mineralization, resulting in physical and mechanical properties superior to mortars without pretreatment. The results showed that a maximum addition of 10% by volume of OTPS treated with calcium hydroxide solution produced lighter mortars with similar mechanical properties to the control mortar. Adding higher amounts of pretreated olive pruning (25–50% by volume) led to a more pronounced deterioration of mechanical properties.

Assessing the zeolite’s effectiveness on the mechanical performance of cement-stabilised sand through triaxial test and microstructure analysis

ABSTRACT In this research, a series of consolidated drained compression triaxial tests were carried out to investigate the mechanical performance of Babolsar sand. Next, the parameters such as cement zeolite substitution percentage, cement content, and curing time were determined. The results revealed significant mechanical strength of specimens by replacing zeolite up to 35% compared with cemented sand mixtures for all ranges of cement percentages. Also, the samples showed more ductile behaviour due to increasing strains at failure. Increasing the zeolite substitution by up to 35% generated shearing band failure. However, exceeding the 35% substitution, the barrelling shear mode was predominant. All samples were compressed initially until reaching a point of instant zero dilation and then dilated until the end of the tests. The dilation tendency was higher in zeolite percentages up to 35%. Moreover, increasing the cement content enhanced the dilation of specimens due to hardening and interlocking cement and sand with zeolite. Finally, microstructure analysis results showed the Si/Ca ratio as a key index to approximate triaxial shear strength development.