Aggregates Of Grains Research Articles

A qualitative approach to describe the viscosity of flowable concrete made with manufactured sand containing different microfines

The concrete made with different manufactured sands can exhibit complex rheological properties. The prediction of viscosity is crucial in concrete placement, but remains challenging given the varied content and characteristics of microfines in the sands. This paper studies the influence of tuff (TF) and limestone (LS) microfines with disparate particle size distributions on the pseudo-Newtonian viscosity of concrete prepared with crushed sand. The concrete had a fixed water-to-binder mass ratio of 0.32 and polycarboxylate ether superplasticizer (PCE) dosage of 0.14 % by mass of biner. Test results showed that the microfines in manufactured sand can reduce the aggregate-to-excess cement paste ratio, leading to lower contact interactions between the aggregate grains. But the ratio of total powder particles and entrained air to excess interstitial solutions increased for the fluid paste matrix of the concrete, which caused greater flow resistance related to the powder contacts and air bubble deformations. A qualitative approach correlating the volume ratio of aggregate grains to excess cement pastes and that of total powder particles and entrained air to excess interstitial solutions was proposed to describe the pseudo-Newtonian viscosity of concrete, regardless of the different microfine additions in manufactured sand.

Sustainable concrete production: Partial aggregate replacement with electric arc furnace slag

Abstract The pursuit of sustainability in the construction industry has stimulated interest in seeking environmentally friendly alternatives to natural aggregates in concrete production. This study evaluates the behavior of concrete when electric arc furnace (EAF) slag is used as aggregates in its production. The primary research gap filled by this study is to deduce the blend of the fine and coarse EAF slag aggregates that would produce concrete of comparative strengths to concrete made with natural aggregates. Concrete mixtures were formulated using varied EAF slag content in the proportions of 0, 10, 15, 25, and 50%, respectively. The compressive strength values increased as the EAF slag content increased. However, this trend was not evident for the density and tensile strength values. The concrete mixture containing 25% EAF slag with 15% fine and 20% coarse EAF slag aggregates had the greatest density value of 2550.00 kg/m3 and the tensile strength value of 4.8 Pa respectively. This could be due to the distribution of the fine and coarse aggregate grains in the mixture. Since the percentage of fine and coarse aggregate grains were 10 and 15%, respectively, it was a close enough range for the fines to fill in the void spaces. This made the mixture more compact which resulted in a higher density and tensile strength values.

Effect of Coarse Aggregate Type on the Fracture Toughness of Ordinary Concrete

This research work aims to compare the strength and fracture mechanics properties of plain concretes, obtained from different coarse aggregates. During the study, mechanical parameters including compressive strength (fcm) and splitting tensile strength (fctm), as well as fracture parameters involving critical stress intensity factor (KIcS) and critical crack tip opening displacement (CTODc) were evaluated. The effect of the aggregates used on the brittleness of the concretes was also analyzed. For better understanding of the crack initiation and propagation in concretes with different coarse aggregates, a macroscopic failure surfaces examination of the tested beams is also presented. Crushed aggregates covered were basalt (BA), granite (GT), and limestone (LM), and natural peeble gravel aggregate (GL) were used in the concrete mixtures. Fracture toughness tests were performed on an MTS 810 testing machine. Due to the high strength of the rock material, the rough surface of the aggregate grains, and good bonding in the ITZ area between the aggregate and the paste, the concretes with crushed aggregates exhibited high fracture toughness. Both of the analyzed fracture mechanics parameters, i.e., KIcS and CTODc, increased significantly in the case of concretes which were manufactured with crushed aggregates. They amounted, in comparison to concrete based on gravel aggregate, to levels ranging from 20% for concrete with limestone aggregate to over 30% for concrete with a granite aggregate, and to as much as over 70% for concrete with basalt aggregate. On the other hand, the concrete with gravel aggregate showed the lowest fracture toughness because of the smooth surface of the aggregate grains and poor bonding between the aggregate and the cement paste. However, the fracture process in each series of concrete was quasi-plastic in the case of gravel concrete, semi-brittle in the case of limestone concrete, and clearly brittle in the case of the concretes based on granite and basalt aggregates. The results obtained help to explain how the coarse aggregate type affects the strength parameters and fracture toughness at bending.

Evaluation of experimental and simulated gamma ray shielding ability of ZnCo2O4 and ZnCo2O4/graphene nanoparticles

Pristine zinc cobaltite (ZnCo2O4) and graphene zinc cobaltite nanoparticles (NPs) have been successfully synthesized by hydrothermal method. The physical properties of both structures were studied using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). XRD results indicated a formation of spinel structure. The elemental composition of the samples has been determined through EDX analysis. From morphological investigation, the aggregation of grains and nano-sized quasi-spherical grains was observed. Nuclear radiation protection investigation for gamma-ray has been studied for both samples. The protection factors against gamma rays, including linear attenuation coefficients (LAC), mass attenuation coefficients (MAC), transmission Factor (TF), radiation protection efficiency (RPE) mean free path (MFP), half value layer (HVL) and tenth value layer (TVL) were calculated. In addition to the experimental examination, simulation with GEANT4 simulation code was also used for both samples to examine the shielding parameters. The most essential parameters of gamma shielding factors such as mass attenuation coefficients (MAC), mean free path (MFP), half value layer (HVL), tenth value layer (TVL) and linear attenuation coefficients (LAC) were evaluated both practically and by simulation. Practically, these values were: 0.75/0.78 cm2/g, 0.22/0.20 cm, 0.15/0.14 cm, 0.50/0.47 cm, and 4.55/4.86 cm−1, for ZnCo2O4 and ZnCo2O4/graphene samples, respectively. By simulation, these values were: 0.65/0.70 cm2/g, 0.25/0.22 cm, 0.17/0.16 cm, 0.59/0.52 cm, and 3.91/4.38 cm−1, for ZnCo2O4 and ZnCo2O4/graphene samples, respectively. The results show that the presence of graphene has affected all the protection parameters. Keywords: Zinc cobaltite, structural properties, gamma shielding, hydrothermal method.

EXTRA FINE-GRAINED CONCRETE FROM WASTE OF MINING CONCENTRATION PLANT FOR CONSTRUCTION PRODUCTS

The theoretical substantiation of the production of especially fine-grained concrete (EFC) from the waste of the Poltava Mining Concentration Plant as a fine-grained aggregate has been performed. Its structure is substantiated taking into account the contacts between the angular aggregate grains, the possibility of increasing strength by introducing mineral fillers and microfillers with particles 5 times smaller than the aggregate grains and cement particles, respectively, is proved. The determination of the composition of EFC from the waste of the Poltava MCP was substantiated by determining and ensuring the optimal value of the coefficient of displacement of aggregate grains by cement paste m opt = 1.89 with the inclusion of dusty fractions of the aggregate. The optimal composition of EFC Aggregate : Cement : Water = (3–3.15):1:0.5 with mandatory use of superplasticizer additive to ensure W/C = 0.5 was determined and experimentally confirmed. The dependences of compressive and tensile strength of EFC on: type and content of superplasticizer additives were experimentally investigated; ratio of aggregate content to cement content; microsilica content; pressing pressure. It was established that the maximum strength of EFC is achieved in the case of the use of superplasticizers: polycarboxylate 1.5 % or sulfonaphthalinformaldehyde 1 % by weight of cement. It was also established that with the same A:C = 3:1 and W/C = 0.5, the strength of EFC on the waste of Poltava MCP exceeds the strength of fine-grained concrete on natural, especially fine-grained sand: in compression - by 2 times, in tension - by 1.9 times and reaches 35 MPa at the age of 28 days. The addition of microsilica in the amount of up to 15 % of the mass of cement allows to further increase the compressive strength by 44 %, and the tensile strength by 20 %. It is proposed to form EFC products by layer-by-layer pressing with a layer thickness of 5 mm. It was experimentally established that the maximum strength is achieved at a pressing pressure of 12 MPa.

Selective crushing, enrichment by friction properties and hydrophobization for obtaining the sustainable blast furnace slag aggregate for road subbase

Air-cooled blast furnace slag is a metallurgical waste that can be used to produce the slag aggregate for pavement subbase. Slag aggregate is much cheaper than natural stone aggregate, but differs in heterogeneity in strength (from 2 to 40 MPa), tendency to absorb water, and low resistance to freezing-thawing. The paper suggests the use of methods of enrichment by friction properties, selective crushing, and hydrophobization to increase slag aggregate resistance to freezing-thawing cycles, crushing, and water penetration. Selection of the most strength (low porous) 75 % slag aggregate grains due to enrichment by friction properties decreases the total water absorption of the sample from 4.45 % to 3.64 %, decreases the sample mass loss after tests for resistance to freezing-thawing cycles from 5.05 % to 2.82 %, reduces the aggregate crushing value (ACV) from 30.71 % up to 23.80 %. Hydrophobization of the pre-enriched slag aggregate additionally reduces its water absorption to 1.08–––1.3 %.

Selected issues concerning the use of Shredded Rubber Waste (SRW) in binder-bound mixtures

This paper presents the results of a composite consisting mainly of industrial waste bound by a hydraulic binder. The composite consists of unburnt coal-mining slate, shredded rubber waste (SRW), fly ash and CEM I cement. The purpose of using the above components was to protect the unburnt coal-mining slate from the negative effects of water, which causes degradation of the aggregate grain size and significantly affects the load-bearing capacity of the aggregate. This was achieved through the use of a binder consisting of shredded waste rubber, fly ash and cement, which imparts hydrophobic properties to the composite. The composite is to be used in road pavement construction and earthworks as a substitute for standard materials. This paper focuses on testing the effects of 5, 10 and 15% additions of shredded rubber waste (SRW) on the physical and mechanical parameters of the composite, mainly compressive strength, water absorption by mass, capillary rise and deformability under cyclic loading. The composite was tested under cyclic loading conditions using a measurement system based on digital image correlation (DIC), with which the deformations occurring on the surface of the test specimens were determined. The results obtained showed the influence of shredded rubber waste additives on the decrease in compression strength (after 7 and 28 days of specimen care), mass water absorption and capillary rise, as well as an increase in the deformability of the composite under destructive loading and cyclic loading.

Acclimatize experimental approach to adjudicate hydraulic coefficients under different bed material configurations and slopes with and without weir

The primary purpose of this study was to evaluate the hydraulic coefficient of coarse aggregate grain size beds and hydraulic parameters under random and perpendicular bed configurations, as well as to explore the discharge coefficient for rectangular weirs. The research objectives were to compare flow resistance coefficients, evaluate the discharge coefficient for rectangular weirs, investigate the relationship between roughness coefficient and hydraulic parameters, and validate the theoretical hydraulic equation for the rectangular weir. This was achieved by analysing different bed configurations, bed slopes, and 20 and 30-mm bed materials. Sieve analysis was conducted on bed materials using American-standard sieves to determine their particle size distribution. The experiment was performed in a rectangular flume measuring 12 m in length, 0.31 m in width, and 0.45 m in depth. In a laboratory experiment, water was pumped into a flume using centrifugal pumps, and a rectangular weir was attached downstream for discharge measurement. The experiment investigated factors such as Manning roughness coefficient, bed material geometry, bed slope, and weir shapes. Approximately 1680 tests were conducted to analysed the impact of these factors on discharge and the coefficient of discharge. The average Manning's roughness coefficients for a grain size of 20 mm were 0.019 (with weir) and 0.019 (without weir) in a random bed configuration, and 0.028 (with weir) and 0.027 (without weir) in a perpendicular flow bed configuration. For a grain size of 30 mm, the coefficients were 0.023 (with weir) and 0.022 (without weir) in a random bed configuration, and 0.033 (with weir) and 0.026 (without weir) in a perpendicular flow bed configuration. The presence of a weir has affected Manning's roughness coefficients and discharge coefficients. With a weir, the roughness coefficients have generally been higher compared to without a weir, indicating increased roughness in the channel. The discharge coefficient for a rectangular weir with a grain size of 20 mm ranged from 0.39 to 0.84 (random bed) and 0.27 to 0.68 (perpendicular flow bed), while for a grain size of 30 mm it ranged from 0.31 to 0.81 (random bed) and 0.23 to 0.48 (perpendicular flow bed). The discharge coefficients have varied depending on the grain size and bed configuration, reflecting different flow efficiencies over the weir. Rough particles influenced flow and Manning's roughness coefficient value, then reduced discharge and velocity values. Under two bed configurations and slopes, beds with a grain size of 30 mm have higher roughness coefficients compared to those with a grain size of 20 mm. The models have shown that the roughness coefficient is inversely proportional to the discharge and directly proportional to the tailgate water levels. The coefficient of roughness and discharge coefficient are mainly influenced by the channel slopes, bed roughness, bed grain size, and bed configuration. A randomly configured bed with a 20 mm grain size gravel bed is preferred over a perpendicular bed configuration to handle high discharges. Using a 20 mm grain-size gravel bed in open-channel flow is more suitable than a 30 mm grain-size bed. Relying on the constant friction factor, Manning's n, is not recommended as it may result in design errors. These findings have the potential to improve hydraulic engineering design practices, enhancing the accuracy and efficiency of open-channel flow systems.

Structural concrete measurements: New distributed approach for standard specimens

Concrete structures are widely used in construction because of their many advantages, including high corrosion resistance, durability, low operating costs, and the ability to design any geometry. However, they also have some disadvantages, such as their high dead weight and susceptibility to cracking. Although this material is widely used globally, new types of concrete, such as high-strength or lightweight aggregate-based, are still being developed. This requires constant control and testing in both laboratory and field conditions. Concrete is a heterogeneous material due to the influence of aggregate grains and local discontinuities, voids or pores. Given these characteristics, it is clear that most conventional diagnostic solutions, such as spot foil strain gauges or extensometers, are unable to accurately analyse these localised effects as they average local strains over the measurement base. In contrast, distributed fibre optic sensing (DFOS) enables strain readings to be taken with millimetre geometric resolution, significantly extending the structural assessment capability. The article describes research on standard concrete cylinders equipped with surface-mounted optical fibres for simultaneous measurements of distributed strains in both the longitudinal direction (compression zone) and circumference direction (tension zone). The novelty of the proposed approach, apart from the way of arranging the sensing fibres on the specimens, lies mainly in the new diagnostic approach that allow (1) the evaluation of the homogeneity of the concrete using statistical parameters, (2) the identification of microcracking and (3) the identification of near-to-failure state based on Poisson’s ratio analysis. Twenty cylindrical specimens were laboratory tested using reference techniques to validate the performance of the DFOS-based system and to provide data for statistical evaluation. The results indicate the possibility of detecting the approaching damage even without knowledge of the material properties of the specimen or the initial stress level at the moment of starting the measurements. The discussion also covered future research directions and potential improvements.

Impact of simultaneous increase in CO2 and temperature on soil aggregates, associated organic carbon, and nutritional quality of rice–wheat grains

AbstractBackgroundFood and nutritional security remain a major thrust area in the under developed and developing countries. These problems are exaggerated by the unprecedented challenges of climate change.AimsThe aim of this study was to assess the impact of climate change on grain quality of wheat and rice genotypes as well as their effect on soil aggregate fractions and aggregate associated carbon.MethodologyIn the context, the present study was formulated by considering four predicted climate scenarios, namely, T0C0 (ambient condition), T0C1 (approx. 25% higher CO2), T1C0 (2°C higher temperature) and T1C1 (25% higher CO2 + 2°C higher temperature) and their impact on grain quality of wheat (HD2967, HD2733, DBW17, and HD3093) and rice (IR83376‐B‐B‐24‐2, IR84895‐B‐127‐CRA‐5‐1‐1, R Bhagwati, and IR64) genotypes as well as soil aggregate fractions and aggregate associated carbon.ResultsThe result revealed that T0C1 has a negative impact on grain nitrogen and protein content. On an average, nitrogen content in wheat and rice showed a decrease of about 15.55% (5.52%–25.32%) and 11.44% (3.33%–23.86%), respectively. Interestingly, the concurrent effect of elevated CO2 and temperature resulted in higher nitrogen and protein content as compared to other climate conditions. Further, P (P) content in the wheat and rice grains also improved under the elevated CO2 condition, whereas the content of potassium was not significantly influenced. Apart from major nutrients, micronutrients (Zn and Fe) were significantly influenced by climatic variables. The study revealed that grain Zn and Fe content of both the crops were reduced due to elevated CO2. The data on soil aggregate fractions revealed that elevated CO2 favors the formation of macro‐aggregate, whereas an increase in temperature favors micro‐aggregate fractions in the soil. Further, the elevation of CO2 also resulted in the accumulation of more carbon in the macro‐aggregates.ConclusionWe conclude that elevated CO2 and temperature cause specific changes in soil aggregate formation and grain nutrient quality. Based on molar ratio of P/Zn and P/Fe, we identified varieties of rice (IR83376‐B‐B‐24‐2) and wheat (HD2733) with higher bioavailability to address the nutritional security with changing climate in developing countries.

How are microstructural defect interactions linked to simultaneous intergranular and transgranular fracture modes in polycrystalline systems?

The major objective of this investigation is to fundamentally understand and predict how intergranular (IG) and transgranular (TG) fracture modes nucleate and propagate in f.c.c. polycrystalline systems due to defects, such as total and partial dislocation densities and grain boundary (GB) structures and misorientations. A dislocation density crystalline plasticity (DCP) formulation based on the evolution and interaction of total and partial dislocation densities was integrated with a recently developed fracture approach to investigate the fracture nucleation and propagation of simultaneous multiple fracture events, including both IG and TG fracture events. The aggregate grains and GB orientations and morphologies are based on EBSD measurements that are representative of polycrystalline copper aggregates with a broad range of random high angle and low angle GBs. The predictions indicate that dislocation density pileups induce IG fracture due to interrelated stress, slip, and total and partial dislocation density accumulations and interactions for both high angle GBs (HAGBs) and low angle GBs (LAGBs). TG fracture nucleation and propagation occurred due to normal stress accumulations, which exceeds the fracture stress, along cleavage planes. Furthermore, it is shown how IG cracks transition from the GB plane to the cleavage planes as cracks nucleate and propagate. Accumulated plastic zones due to different slip system activities can impede and blunt crack propagation and fronts. These plastic zones form due to high Lomer and Shockley partial dislocation densities. These predictions, which are consistent with experimental observations, provide a fundamental understanding of how simultaneous failure modes initiate and propagate for physically representative microstructures.

Microbial community structure and carbon transformation characteristics of different aggregates in black soil.

Previous research on whole-soil measurements has failed to explain the spatial distribution of soil carbon transformations, which is essential for a precise understanding of the microorganisms responsible for carbon transformations. The microorganisms involved in the transformation of soil carbon were investigated at the microscopic scale by combining 16S rDNA sequencing technology with particle-level soil classification. In this experiment,16S rDNA sequencing analysis was used to evaluate the variations in the microbial community structure of different aggregates in no-tillage black soil. The prokaryotic microorganisms involved in carbon transformation were measured before and after the freezing and thawing of various aggregates in no-tillage black soil. Each sample was divided into six categories based on aggregate grain size: >5, 2-5, 1-2, 0.5-1, 0.25-0.5, <0.25 mm, and bulk soil. The relative abundance of Actinobacteria phylum in <0.25 mm aggregates was significantly higher compared to that in other aggregates. The Chao1 index, Shannon index, and phylogenetic diversity (PD) whole tree index of <0.25 mm aggregates were significantly smaller than those of in bulk soil and >5 mm aggregates. Orthogonal partial least-squares discrimination analysis showed that the microbial community composition of black soil aggregates was significantly different between <1 and >1 mm. The redundancy analysis (RDA) showed that the organic carbon conversion rate of 0.25-0.5 mm agglomerates had a significantly greater effect on their bacterial community structure. Moreover, humic acid conversion rates on aggregates <0.5 mm had a greater impact on community structure. The linear discriminant analysis effect size (LEfSe) analysis and RDA analysis were combined. Bradyrhizobium, Actinoplane, Streptomyces, Dactylosporangium, Yonghaparkia, Fleivirga, and Xiangella in <0.25 mm aggregates were positively correlated with soil organic carbon conversion rates. Blastococcus and Pseudarthrobacter were positively correlated with soil organic carbon conversion rates in 0.25-0.5 mm aggregates. In aggregates smaller than 1 mm, the higher the abundance of functional bacteria that contributed to the soil's ability to fix carbon and nitrogen. There were large differences in prokaryotic microbial community composition between <1 and >1 mm aggregates. The <1 mm aggregates play an important role in soil carbon transformation and carbon fixation. The 0.25-0.5 mm aggregates had the fastest organic carbon conversion rate and increased significantly more than the other aggregates. Some genus or species of Actinobacteria and Proteobacteria play a positive role in the carbon transformation of <1 mm aggregates. Such analyses may help to identify microbial partners that play an important role in carbon transformation at the micro scale of no-till black soils.

Effect of sand gradations on the fresh properties of 3D printable concrete

Sand is frequently used as a fine aggregate in concrete mixtures, but the performance of concrete can be considerably impacted by regional variations in sand gradation. In this work, the effect of sand gradations on the fresh properties of three-dimensionally printable concrete (3DPC) mixtures was systematically investigated. The binder combinations (cement, fly ash, silica fume, limestone powder, ground granulated blast-furnace slag) and the water/binder ratio were kept constant throughout the trials. The sands used in the mixtures were standard Ennore sand (ES) (grades I, II and III) and locally available river sand (RS). The mini-slump heights and flow values of mixes made with RS and with optimal packing of binary and ternary combinations of the standard ESs were evaluated and compared with those of the unary packing of ESs and RS. A correlation between the fineness modulus of different sand gradations and printable flow time was determined. The influence of sand gradations and fineness modulus on buildability, shape retention, open time and extrudability were evaluated. It was found that the performance of the fresh 3DPC was influenced by the aggregate's gradation and grain size in addition to its fineness. In conclusion, different fine aggregate specifications must be chosen depending on the various 3D printing building conditions and design requirements.

ВЛИЯНИЕ МИКРОБНОЙ КАРБОНАТНОЙ БИОМИНЕРАЛИЗАЦИИ НА ПРОЧНОСТЬ ЦЕМЕНТНОГО КАМНЯ

An intensive urbanization, renovation of housing stock, emergencies and natural disasters lead to difficulties arise in the management of concrete waste. In this regard, recycling construction and demolition waste is an effective solution for saving material and energy resources in the construction field. The article discusses the possibility of optimizing the structure and increasing the strength characteristics of concrete by selecting the grain composition of the aggregate based on recycled concrete scrap and the use of microbial carbonate biomineralization. The distribution of aggregate grains (0.315–5 mm), which is crushed ordinary stone SKTs, into fractions has an impact on the nature of the formation of contact zones between the cement matrix and the aggregate. This determines a decrease in strength characteristics according to the following relationship: with a decrease in the size of the aggregate, the strength of cement concrete increases. The addition of a biomineralizing solution to the cement mixture leads to improved adhesion of the cement paste to the surface of the aggregate due to the formation of additional crystallization centers in the area of the contact layer, clogging of the pore space with induced new formations, which increases the strength of concrete, both at brand age and in the forecast period.

Experimental assessment of appropriate time for aggregate exposure at the surface of cement concrete pavement

ABSTRACT Exposed aggregate concrete (EAC) pavement is a commonly employed technology in Europe for the construction of highways. The technical challenges associated with pavement construction include achieving both a comfortable ride and the desired skid resistance, while ensuring the long-term concrete durability. Maintaining uniformity of concrete mix, precise dosing of retarding agents, optimal selection of brushing time, and ensuring adequate curing conditions are identified as critical factors for achieving the designed ride performance. This study is focused on determining the appropriate time for the brushing operation, conducted to expose aggregate grains at the surface of the pavement. Laboratory tests were performed on concrete mixes designed to replicate job mixes for the upper layer of a two-layer concrete pavement. Measurements of the mass of evaporated water from the cement paste, isothermal calorimetry tests, and modified Vicat tests were employed to predict the appropriate brushing time. The texture depth was determined using a laser profiler as a function of brushing time. Compressive strength, the rate of chloride ion migration, and scaling resistance were determined through tests conducted on specimens cut from exposed aggregate slabs. Results revealed the suitability of the developed test method for determining the appropriate time for brushing EAC pavements.

Biogenic synthesis of silver nanoparticles from the leaf extract of Enicostema axillare (Poir. ex Lam.) A. Raynal and its alpha amylase inhibition activity

Due to its numerous applications, commercial demand for silver nanoparticles produced by biological means is rising. This procedure has no adverse effects, is inexpensive, takes little time, and is non-toxic. The current work uses leaf extracts from Enicostema axillare (Mamajavo) to synthesise silver nanoparticles. The nanoparticles may be characterised by UV–VIS, FT-IR, SEM, TEM, and EDAX. The effectiveness of the screening inhibition assay and alpha-amaylase inhibitory activities is assessed using methanolic leaf extracts and silver nanoparticles. The outcome shows that AgNps exhibit aggregates of grains with a restricted size distribution range between 60 and 80 nm. In comparison to leaf extract, silver nanoparticles made from methanolic leaf extracts have high alpha-amaylase inhibitory action. This study showed that Enicostema axillare's AgNps decrease in the presence of alpha-amylase inhibitors.

Laboratory evaluation of a complex treatment technology for reducing water absorption of the pavement subbase aggregate from the blast-furnace slag

When smelting each ton of pig iron, approximately 500 kg of blast-furnace slag is formed and requires recycling. Air-cooled blast-furnace slag can be used for the manufacture of slag aggregate for the pavement subbase layers, as an alternative to natural stone aggregate. The wide use of slag in this area is limited by its high water absorption. This paper proposes a complex technology to reduce water absorption of slag aggregate. This technology includes selective crushing, which allows separating low-porosity aggregate grains from high-porosity ones, and impregnation of selected low-porosity grains with hydrophobic agent (surface hydrophobization). The results of a laboratory evaluation of this technology effectiveness are presented. Article also contains optimal parameters of this complex technological process which allowed to reduce the water absorption of the slag aggregate from 4.54% to 1.05%.

High strength concretes based on the choice of the best particle size distribution in aggregate

The requirements of the modern (high-end) construction industry demand the development of new types of concrete of high, and especially very high strength and with significantly improved properties in terms of durability. They provide new possibilities in the field of concrete technology of high strength and performance. When designing the composition of high-strength concrete (HSC), a special attention should be paid to the particle size distribution of aggregates, which should be chosen so as to achieve an "optimal" packing of the aggregate grains. The maximum grain size has been reduced to 2 mm. The Funk-Dinger formula was used to calculate the particle size distribution, which also takes into account fine particles of mineral powder additives. CEM I 52.5R, pure quartz sand, quartz filler, silica fume, powerful superplasticizer and low water/binder ratio were chosen for making HSC. In total, five different concrete mixtures were made. The paper presents the results of testing important properties of hardened concrete at ages from 1 day to 90 days and statistical processing of the obtained test results.

Relating early-age hydration and flow loss of mortar prepared with manufactured sand

Cement-based materials prepared with manufactured sand can exhibit quick loss of fluidity. However, the estimation of the flow loss remains difficult given the variable contents and physiochemical properties of the microfines in various sands. This paper studies the fluidity loss of mortar mixtures made with different manufactured sands varying in mineral composition and content of microfines. The effect of microfines on accelerating the early-age hydration of cement before the deceleration period was evaluated by quantifying the generation of early hydration products. Test results show that the growth of yield stress corresponding to the loss of mini-slump flow of mortar mixtures were mainly determined by the formation of early hydration products, in addition to the volume fraction and packing density of aggregate grains and powder particles. An approach was then proposed that can assess the loss of mini-slump flow of mortar mixtures prepared with manufactured sand, regardless of the type and content of the microfine materials in the sand.

Evaluasi Nilai Stabilitas Pada Aspal AC-WC Dengan Metode SNI 06-2489-1991

Asphalt concrete is a combination of aggregate, asphalt, with or without additives. To obtain high stability in asphalt concrete, it is necessary to have an aggregate that is well graded, dense, and has small voids between aggregate grains. Asphalt concrete performance testing can be done through the Marshall test. The Marshall Test Tool is used to determine the characteristics of a road pavement layer. One of the Marshall test kits that is still widely used in laboratories is the analog Marshall test kit. This study used an experimental method in the laboratory of the Jombang Regency Public Works Office with core test objects (KOR) made of a mixture of wear-resistant steel (AC-WC) with a thickness of 4 cm each. In this test, 4 core specimens were used in accordance with the 2010 General Highways Specifications (revision 3). With the composition of the constituent materials consisting of Aggregate 0-5 mm (42.2%), Aggregate 5 - 10 mm (33%), Aggregate 10 - 15 mm (16.9%), Filler Cement (1.9%), Asphalt Content (6%) those who get the value of 91.3% (stability) is the final residual stability value, before obtaining this value there are several values listed, namely; value 2,292gr/cm3 (Bj Mix), 5.274% (effective asphalt content), 0.772% (absorption of asphalt), 4.71% (VIM), VMA 16.80% (VIM), 71.97% (VFB ), 1178kg (initial marshall stability) , 3.55mm (flow), 332kg/mm (Marshall quetient).