Aggregates Of Grains Research Articles

Validity of Limestone Aggregates for Using in Asphalt Concrete Mixtures for Surface Layer of Roads

In this paper, limestone quarries in the Bazian region, west of Sulaymaniyah city, northern Iraq, were evaluated geotechnically to examine their suitability for developing asphalt concrete for the top layer of roadways. Two samples were collected to perform geotechnical testing, including physical, chemical, and permanence tests. From the physical results, it is evident that the coarse and fine aggregate grain sizes demonstrated conformity to the American Society for Testing and Materials ASTM-C136 as well as the requirements of the fine aggregate standards ASTM-C117, which fall within the coarse, fine, and filler areas. Moreover, the findings revealed that the flat granules are 22% and the longitudinal granules are 35%. Based on these results, it did not go over the limits set by British standards, so it meets the requirements for concrete work. Another promising finding of durability tests was 21.8%, which represented the highest weight loss. This is an important finding in the understanding of the suitability of the aggregate to American and Iraqi standards in concrete work. A further novel finding of stability tests demonstrated the cement's suitability with Iraqi standards and the American standard C131-C535-2003. Finally, the results of Marshall's test for density, creep, and stability reveals the conformity with the Iraqi specification for asphalt concrete works D2726-05, where the density value was 2.292 and the percentages of creep and stability were 12.2 kN and 2.9 mm, respectively. The results of examining the cement asphalt were in accordance with the specifications required for concrete works, where the optimum percentage of asphalt for the design of the asphalt mixture for the surface layer was 4.8. Also, the percentage of airspace was 4.1 according to the American standard D2041.

Investigation of the influence of misorientation-dependent anisotropy on the microstructure evolution under magnetic field: A multi-phase-field study

The influence of magnetic field-driven grain growth in a polycrystalline microstructure is studied via the multi-phase-field approach with the assumptions of isotropic and anisotropic grain boundary (GB) energy. Simulations are carried out using a two-dimensional representative volume element of titanium polycrystalline with the hexagonal crystal structure. The GB energy is a function of the misorientation angle by Read-Shockley equation and is independent of the GB inclination. The simulation results illustrate that the grain growth kinetics and final texture influentially depend on the initial texture when considering the misorientation-dependent anisotropy of GB energy. If the Euler angle φ 2 is randomly distributed for all of the grains, the simulation results are similar for isotropic and anisotropic GB energies. Whereas the simulation results for anisotropic GB energy are significantly different from the isotropic case by considering φ 2 = 0 for all grains. The elongation of grains, the aggregation of grains with analogous orientations, and deceleration of texture evolution and grain growth kinetics are its most important features. Also, the impact of magnetic field intensity is examined and, it is illustrated that the difference in simulation results for isotropic and anisotropic GB energies decreases with increasing the magnetic field intensity.

Importance of Concrete Mesoscale Structure on Bond-Slip Behavior of Externally Bonded CFRP Strips

Currently, the effect of the concrete substrate on the load-bearing capacity of externally bonded carbon fiber-reinforced polymer (CFRP) strips is determined in the guidelines solely on the basis of the concrete strength. In addition to strength, surface preparations can improve the bond resistance by exposing the aggregates of the substrate. However, the interlocking also depends on the parameters that derive from the inner concrete structure such as the aggregate grain dimension and shape, as well as the air void distribution. Therefore, the influence of the concrete inner structure on the bond is investigated with double shear tests by comparing specimens with equivalent concrete strength and varying grain shape and dimension. Bond parameters are calculated using a novel procedure based on optical measurements. Furthermore, crack paths are analyzed by means of computed tomography (CT) scans, which prove to be an essential inspecting technique for characterizing the inner concrete structure. The fracture energy is approximately 30% higher for concrete with a maximum grain size of 8 mm compared to an equivalent mortar with 4 mm maximum grain size.

Darriwilian–Sandbian (Middle–Late Ordovician) shallow warm-water deposits in the Upper Yangtze region, South China: A case study from the Qiaojia area, northeastern Yunnan Province

The Middle–Late Ordovician Nuoduo and Huadan formations are well exposed at Songliang of northeastern Yunnan Province, representing rare neritic carbonate sediments deposited in the Yangtze region, South China during that time. Detailed sedimentological analyses support the recognition of ten microfacies from the succession, including shale (MF 1), argillaceous mudstone/dolostone (MF 2), mollusk-ostracod wacke-packstone (MF 3), peloidal wacke- to pack-grainstone/dolostone (MF 4), ooid-cortoid-peloid pack-grainstone/dolostone (MF 5), peloidal bindstone (MF 6), bioclastic wacke-packstone (MF 7), green algae mud-wackestone to floatstone (MF 8), bioclast-lithoclast float-rudstone (MF 9) and green algae bindstone (MF 10). Types A, B and C of shallowing-upward sequences are constructed according to vertical associations of MFs. The Nuoduo Formation mainly comprises Type A and Type B, both being characterized by abundant peloids, ooids, cortoids and aggregate grains. MF 5 and MF 6 cap the Type A and Type B sequences, respectively, suggesting an overall restricted marine environment shifting cyclically from lagoon to shoal, or lagoon to tidal flat, respectively. Type C sequences, occurring in the topmost Nuoduo to Huadan formations, contain various green algae indicative of open-sea, euphotic subtidal zones. The transition from A and B to C sequences is marked by ferruginous ooidal intervals, possibly correlated to relative sea-level rise and/or tectonic activities. A continuous neritic, warm-water environment is proposed for this area from late Middle to Late Ordovician, with the Nuoduo Formation filling the absence of warm-water deposits in the tropical or subtropical Yangtze region during Middle Ordovician. The increasing diversity and abundance of green algae in the Huadan Formation might represent a global radiation event of marine flora during the studied interval. Unique fossils and environments distinct from those of the interior Yangtze region are documented here, leading to a better understanding of the Ordovician System regionally and globally.

Power spectral density-based fractal analyses of sputtered yttria-stabilized zirconia thin films

This study provides information about the surface morphology of sputtered yttria-stabilized zirconia (YSZ) thin films from the atomic force microscope (AFM) spectral analyses using the power spectral density (PSD) function at varying annealing temperatures. Applying fractal and k-correlation fitting models to the PSD data, fractal dimension, Hurst exponent, correlation length, and equivalent root mean square roughness are quantified. The PSDs of the films exhibit an inverse power-law variation at high spatial frequency, which points to the existence of the fractal components in the film’s surface. The annealing temperatures up to 900 ∘C decreased fractal dimension from 2.60 to 2. The surface roughness increased from 0.10 to 13.92 nm and from 0.04 to 3.95 nm, obtained from the statistical analyses of AFM images and the k-correlation model. The films annealed from 500 ∘C to 800 ∘C showed fine grain size morphology with Hurst exponent values from 0.40 to 0.53, indicating a homogeneous spatial roughness distribution. While the film annealed at 900 ∘C exhibited large aggregate grains morphology. The growth of a sample annealed at the temperature of 900 ∘C is more likely to be ruled by the step-edge barrier-induced mound growth and inhomogeneous spatial distribution of roughness. In contrast, normal self-affine behaviour is observed at lower annealing temperatures.

Methods of strengthening the grains of recycled aggregates

Poorer quality indicators than natural aggregates generally characterize recycled aggregates. This is due to the composition of the primary raw material (mostly demolition waste), the method of processing (crushing, sorting) and the typical character of the grains, which, in addition to the original grain of natural aggregate, also contains the original adhered mortar. The resulting grains are heterogeneous, characterized by lower strength, higher porosity, higher absorbency, or the presence of cracks. Improving the quality of these grains is one of the approaches to increase their potential for use in concrete. Several methods of recycled concrete aggregate (RCA) grain strengthening are being studied worldwide, the effect of which on the final quality of recycled aggregates and new concrete is different. The article describes and compares the methods in terms of their impact on selected properties of both. The comparative analysis is based on the collection of results presented in research publications. Based on the evaluation of the results, polymer emulsion treatment can be identified as the most effective way to improve RCA water absorption. Sodium silicate treatment came out the best to improve the compressive strength of concrete mixed with treated RCA.

Using Reclaimed Cement Concrete in Pavement Base Mixes with Foamed Bitumen Produced in Cold Recycling Technology.

The paper presents the results of exploratory research on the use of reclaimed cement concrete in cold-recycled mixes with foamed bitumen. Because reclaimed cement concrete, unlike natural aggregates, is expected to have a residue of the non-hydrated cement covering the aggregate grains, which may result in a secondary cementation process after its application in a road base, this avenue was explored by tracking the time evolution of the compressive strength of the final material. The tests were performed using two mixtures, i.e., a reference mixture and a mixture containing 25% reclaimed cement concrete. The mixtures containing reclaimed cement concrete were characterized by increased uniaxial compressive strengths after each curing period (3, 4, 7, 14 and 28 days)—by 11.5 kPa on average and e.g., 498 kPa vs. 506 kPa after 28 days. The obtained differences between the mixtures were not found to be statistically significant. The small effects of the incorporation of reclaimed cement concrete were attributed to the time passed typically between the demolition and new pavement construction and to the presence of a second binding material—bitumen.

Laboratory investigation of the permeability properties of cement mortar with different sand–cement ratios

The influences of the sand–cement (s/c) ratio and microstructure on the water permeability of cement mortar were examined. Laboratory experiments were carried out to study the influence of the s/c ratio on the seepage failure of cement mortar. The results showed that the contacts of aggregate grains can be divided into three types – wrapped contacts, surface contacts and point contacts. The relationships among water permeability, porosity and wave velocity of cement mortar were also investigated and it was found that the permeability coefficient of cement mortar increases exponentially with an increase in the s/c ratio. It was also found that there is a critical s/c ratio range (around 5–6), at which the porosity and wave velocity change remarkably. When the critical s/c ratio is exceeded, the critical seepage pressure is reached and seepage failure occurs. The relationship between the permeability coefficient and the critical seepage pressure was found to be a power function.

What Influence Does Conventional Tillage Have on the Ability of Soils to Sequester Carbon, Stabilise It and Become Saturated in the Medium Term? A Case Study in a Traditional Rainfed Olive Grove

Soils have the capacity to store three times more carbon (C) than the atmosphere. This fact has focused scientific and governmental attention because it is one way to mitigate climate change. However, there comes a time when the capacity of soils to store C reaches a limit, considering soil organic carbon (SOC) saturation. In the Mediterranean area, agricultural soils are traditionally exposed to conventional tillage (CT), causing soil properties and quality degradation. Therefore, this study aimed to determine whether CT modifies the carbon storage capacity (carbon saturation), linked to soil mineral fractions <20 µm in olive grove soil in a Mediterranean area over 15 years. The results showed losses of SOC and soil organic carbon stock (SOC-S) over the period studied. Moreover, CT significantly affected aggregate grain size, reducing the percentage of small macro-aggregates (2000–250 µm) by 51.1%, 32.9%, 46.6%, and 50.6% for the Ap, Bw, BC, and C horizons, respectively, and promoting an increase in fine fractions (large micro-aggregates (250–53 µm), silt + clay fraction (53–20 µm) and fine silt + clay (<20 µm)). After 15 years, SOC fractionation showed a decrease in SOC concentration within the large macro-aggregate fraction (>2000 µm) of 38.6% in the Bw horizon; however, in the small macro-aggregates (2000–250 µm), an increase in SOC concentration over time, of 33.5%, was observed in the Ap and Bw horizons. This increasing trend continued in the fine soil fractions. Concerning SOC bound to the fine mineral fraction (<20 µm), evolution over time with CT led to an increase in soil sequestration capacity in the first horizons of 44.7% (Ap horizon) and 42.9% (Bw horizon), and a decrease in depth (BC horizon) of 31.3%. Finally, the total saturated soil organic carbon stock (T-SOC-Ssat), after 15 years, experienced an increase of 30.5 Mg ha−1, and these results conditioned the soil organic carbon stock deficit (SOC-Sdef), causing a potential increase in the capacity of soils to sequester carbon, of 15.2 Mg ha−1 in 15 years. With these results, we can affirm that the effect of CT in the medium term has conditioned the degradation of these soils and the low SOC concentrations, and has therefore made it possible for these soils, with the application of sustainable management practices, to have a high carbon storage capacity and become carbon sinks.

Diagnosis of ASR damage in highway pavement after 15 years of service in wet-freeze climate region

Diagnostic tests were carried out on specimens drilled from a section of jointed, unreinforced highway pavement after 15 years of service. The section of highway was exposed to heavy road traffic, environmental actions of wet-freeze climate zone and associated winter maintenance including application of deicing salt. Premature pavement damage was manifested by visible cracking, mostly along transverse joints and in slab corners. Tests performed on core specimens included petrographic analysis of concrete and its components, using optical and scanning electron microscopy, also evaluation of elastic and transport properties, expansion potential, cracks and air void system. Numerous cracks in the grains of coarse quartzite aggregate were found. Reactive forms of quartz in quartzite aggregate - microcrystalline and cryptocrystalline quartz - were abundant. The gel-like products in cracks in quartzite grains and in surrounding cement paste were identified as alkali-silica reaction products. Expansion of specimens exposed to an alkali-silica reaction-promoting environment indicated the potential for further development of such reaction. Substantial cracking and reduction of modulus of elasticity was correlated with the presence of reactive quartz in quartzite aggregate. The role of additional destructive factors, such as the impact of heavy vehicles traffic and freeze-thaw aggression was indicated by greater cracks in the slow traffic lane compared than in the emergency lane, associated with local marginal air entrainment of concrete.

Geology, geochemistry, and genesis of REY minerals of the late Cretaceous karst bauxite deposits, Zagros Simply Folded Belt, SW Iran: Constraints on the ore-forming process

The present study focuses on the geochemistry and occurrence of REY (rare earth elements and yttrium)-bearing minerals in the Late Cretaceous karst bauxite deposits in the central part of the Zagros Simply Fold Belt (ZSFB), SW Iran. The ore bodies comprise a series of individual pods and/or contiguous lenses that occur as infills of deep karst cavities, depressions, and fractures within the upper neritic carbonates of the Cenomanian–Turonian Sarvak Formation. Karst bauxites from the ZSFB show, overall, the same mineral components, which consists of boehmite, hematite (commonly occurring as Al-rich), anatase, and kaolinite, with lesser amounts of diaspore, goethite, chamosite, rutile, and zircon. Among minor constituents, single crystals rich in rare earth elements (REEs) occur mainly in the form of authigenic REY fluorocarbonate, phosphate, and oxide minerals (bastnasite, parisite, rhabdophane, churchite and cerianite). Some textural features, such as spheroidal concretions, pisoids with cortexes lacking radial and circular fractures, growth of simple cortex around earlier pisoids, and pelitomorphic matrix suggest the ores are mostly autochthonous in origin. R-mode factor analysis revealed several significant interelemental relationships including: (i) significant and positive weightings for TiO2, Al2O3, Cr2O3, Ni, Zr, Nb, Hf, Ta, W, and Th, and a significant, negative weighting for SiO2 represent a later bauxitization stage involving silica depletion under drier conditions, promoting formation and stability of a range of minerals including detrital minerals and Al and Ti oxyhydroxides which also control, through scavenging, cations of first-row transition metals such as Ni2+ and Cr6+; (ii) Supergene conditions, mainly acidic pH, probably played an efficient role in the formation of secondary REE-rich phosphates and Ga-hydroxide; (iii) similar and meaningful weightings for U and V suggest that the redox environment would be most important in controlling the U and V mineral phases; and (iv) the scandium co-variance with Fe2O3 represents the control exerted by iron oxy-hydroxides on the critical metal Sc. In the ZSFB bauxites, the most frequent authigenic REE-bearing minerals are light REE (LREE) fluorocarbonates of the bastnaesite group that forms a solid solution series between end members parisite [CaCe2(CO3)3F2] and bastnäsite (CeCO3F). The mode of occurrence of bastnäsite-Ce and parisite-Ce suggests that cerium as fluoride and/or carbonate–fluoride complexes were readily leached by acidic downward solutions and finally precipitated on the geochemical barrier of the carbonate bedrock under alkaline and reducing conditions. Rhabdophane [(Ce, La) PO4·H2O] as an LREE phosphate mineral appears in two generations with different chemical compositions, an early one as irregular and/or acicular particles within the cavities and a later one along the margin of a goethite microvein that cuts the pelitomorphic matrix. Cerianite (CeO2) occurs mainly as sub-micrometer to micrometer grains in the porous aggregates of the aphanitic matrix and as microdomains or microveins that coexist with Al-oxyhydroxide and goethite. Cerianite precipitation may occur due to the predominance of acidic/oxidizing conditions and the dissolution of Ce-rich fluorocarbonates in the bauxitic profile, respectively. The only heavy REE (HREE) phosphate mineral within the ZFSB bauxite deposits is churchite[Y(PO4)·2(H2O)] that forms as single euhedral crystals at the core of the sub-spheroidal structures under an acidic condition.

Airport Cement Concrete with Ceramic Dust of Increased Thermal Resistance.

The impact of aircraft on airport pavements is varied and closely related to their operational durability. The article presents the impact of the annealing process related to the forced impact of airplanes on airport pavements. The composition of cement concrete with ceramic dust, which is characterized by increased thermal resistance, has been proposed. Two research cycles were programmed, differentiated by the annealing scheme and the way in which the temperature influences the annealing time. Samples stored at a temperature of 20 ± 2 °C were subjected to testing. The tests were carried out for two diagrams: A and B. The first—diagram A—included the continuous impact of the flue gas stream on the samples for a period of 350 min with a test step every 25 min. For the second—diagram B—the samples were alternately heated (1 min) and cooled (15 min). The influence of the proposed pavement mix on changes in the internal structure of cement concrete and the increase in its resistance to high temperatures was determined. In the microstructure of the CC-1 concrete matrix, it was found that there were plate-granular portlandite crystals up to 10 µm in size and ettringite crystals with a length of 8 µm. In the CC-2 concrete, the ettringite crystals were less numerous and had a length of up to 5 µm, there were also continuous contact zones between the aggregate grains and the cement matrix (diagrams A). The alternating annealing/cooling (diagram B) resulted in the ettringite crystals in the CC-1 matrix being up to 10 µm long, and in the CC-2 concrete up to 7 µm long. The contact zone between the aggregate grain and the matrix in CC-2 concrete was continuous, and the microcracks in CC-1 concrete were up to 8 nm. Regardless of the heating diagram, in the surface zone, there were larger microcracks in the CC-1 concrete than in the CC-2 concrete. For diagram A they were 14 µm and 4 µm and for diagram B they were 35 µm and 5 µm, respectively. It was found that concrete with ceramic dust is characterized by a lower and more stable temperature increase. In scheme A, the average temperature increase on the heated surface ranged from 46 °C to 79.5 °C for CC-1 concrete, and from 33.3 °C to 61.3 °C for CC-2 concrete. However, in scheme B, the temperature after 350 heating cycles for CC-1 concrete increased to 129.8 °C, and for CC-2 concrete to 116.6 °C. After the cooling period, the temperature of CC-1 and CC-2 concrete was comparable and amounted to 76.4 C and 76.3 °C, respectively. CC-2 concrete heats to lower values, and favorable changes in internal structure translate into higher strength and durability (after 350 heating cycles according to scheme A, the strength of CC-1 concrete was 67.1 MPa and of CC-2 concrete 83.9 MPa, while in scheme B, respectively, 55.4 MPa for CC-1 and 75 MPa for CC-2).

Electrical installations running through masonry walls: developing waste generation indicators for environmental performance analysis

Waste generation is one of the most relevant environmental aspects of the construction industry. About 47 million tons of construction and demolition waste are collected annually by Brazilian municipalities. One of the activities that generates waste is cutting chases on walls for installations. However, there are no waste generation indicators for this activity. Understanding waste generation processes enables managers to prevent them and promote their proper environmental management. This study assessed the generation of waste resulting from the cutting of clay bricks for electrical installations using three tools: milling cutter, marble saw, and cold chisel. The study included data collected from residential construction works and experimental data collected from the construction of real-scale walls. In a laboratory, five different wall configurations were built and the three tools mentioned were used to cut a chase on the walls. The results were statistically analyzed to define a waste generation index (WGI) by linear regression. The type of tool employed had no influence on the waste generation index, which was 26.5 ± 2.6 kg/m2. However, the tools used directly influenced the quality of the service, productivity, and the volume of waste generated. The waste from the milling cutter showed the smallest maximum aggregate size and the largest bulk density, followed by the waste resulting from the marble saw and the cold chisel. The marble saw and cold chisel waste samples had around 78% of their composition in the coarse aggregate grain size range. The milling cutter waste samples were the finest and had on average 60% of their composition in the fine aggregate grain size range. The width of the chases made with the milling cutter were smaller and more consistent than those made with the cold chisel, which showed irregularities and larger dimensions than necessary. From the waste generation indicators obtained in this study, construction managers will be able to choose more appropriate cutting tools and improve their planning and management systems to minimize associated environmental impacts.

Influence of the aggregate type on delayed ettringite formation

The studies carried out aimed to define the influence of the aggregate type on the simultaneous occurrence of the alkali-silica reaction and delayed ettringite formation. In their composition, sand or calcium aggregate and aggregates containing 6% opal with graining of 0.5 to 1.0 mm, were used. Mortars from each type of aggregate and Portland cement containing 1.2% Na2Oe and 4.5% SO 3 were prepared, and then cured in water at 90°C. Studies have shown a great influence of the type of aggregate on the expansion caused by the delayed ettringite formation. In this case, the calcium aggregate visibly reduces the expansion of a mortar caused by delayed ettringite formation, while it has a much smaller influence on the expansion of the bars, caused by the potassium reaction with opal. Microstructure observations have shown that sodium-potassium-calcium silicate gel and ettringite around the aggregate grains, are responsible for expansion in the case of sand with opal addition.

Investigating Mechanical Performance of Ravelling in Hot Mix Asphalt Containing Plastic Waste

One of the road damages on the flexible pavement is ravelling. Ravelling caused by the release of aggregate grains from the asphalt mixture. The interaction between the wheels of the vehicle and the surface of the pavement causes friction that pushes the aggregate out. The plastic waste on road pavements has been widely used to improve the performance of road pavement structures. Most of previous study focused on Hot Mix Asphalt (HMA) ravelling using Cantabro test. The purpose of this study was to investigate the ravelling performance of plastic waste material in hot mix asphalt mixtures. In addition, the use of plastic waste can reduce the environmental impact due to the high volume of plastic waste. The test is carried out in the laboratory using a rotation abrasion device based on the principle of rotating wheel load with loading, speed, and testing time parameters. Furthermore, the ravelling resistance value of HMA was obtained in dry and wet conditions. The addition of plastic waste into asphalt can increase the ravelling resistance of HMA mixes. The results of the wet test have greater ravelling resistance than dry test.

Effect of aggregate size and polyethylene sheet curing on me-chanical and microstructural properties of lightweight expanded clay aggregate concrete

This study assessed the effect of lightweight expanded clay aggregate (LECA) grain size and curing with polyethylene concrete curing film (PCCF) on microstructure, interfacial transition zone (ITZ), and compressive strength of structural lightweight aggregate concrete (LWAC) produced with two different Dmax (16 or 22.4 mm). To this end, 2 series of normal weight aggregate concretes (NWAC) and 6 series of LWAC incorporating 40% by vol. unprewetted LECA having (0-3, 3-8, or 8-16 mm) grain sizes were evaluated by using unit weight, compressive strength tests at 1, 7, and 28 days and SEM-EDX observations. Preventing the moisture loss from fresh concrete through PCCF curing had positive effects on compressive strength up to 14 and 9% for 1 and 28 days respectively. Shell thickness of LECA considerably increased with the decrease in LECA grain size. Thus, the compressive strength of LECA and LWAC increased by the decrease in LECA grain size. LWAC containing 0-3 mm LECA, achieved up to 21% higher compressive strength to weight ratio compared with the NWAC with the aid of the pozzolanic reactivity of fine LECA particles.

NUMERICAL MODELLING OF INTERLAYER ADHESION IN THE LAYER OF RECYCLED MATERIAL WITH THE USE OF THE LEUTNER APPARATUS AND COMPUTED TOMOGRAPHY SCANNING

The work has investigated the actual mechanism of the adhesion between successive asphalt layers, taking into account the macrostructure of the pavement layers, which are made of heterogeneous materials. The interaction between the joined layers was determined by applying a cohesion contact model. The parameters of the model were identified using the results obtained in the course of the actual Leutner tests. The heterogeneity of the structure was mapped based on a digital image of a tomographic cross-section. The separation of the materials included in the individual layers was performed with the use of a script in the MatLab program. Thanks to this, the batch file for the Abaqus program was prepared thoroughly. As a result, it was possible to map as closely as possible the profile of the deformation caused by the loss of the interlayer adhesion. Based on the data analysis, it was found that in the layer of the base course constructed from cold-applied recycled materials, the loss of interlayer adhesion is related to the state of non-linear mastic deformation. As a consequence, it was found that large deformations in the mastic structure would cause losses of aggregate grains in the recycled layer. In addition, a large horizontal displacement within the layer of the base course made of recycled material is one of the likely causes of edge fractures in the road structure.

Analisis Karakteristik Serbuk Sabut Kelapa (Cocopeat) Sebagai Agregat Halus pada Campuran Beton

The advantages of coconut coir powder (cocopeat) are resistant to microorganisms, weathering and resistant to mechanical spelling, namely friction and blows. Based on these advantages, cocopeat can be used as a blend of fine aggregates in the manufacture of concrete. The sieve test was conducted on the cocopeat to determine the initial feasibility analysis of cocopeat as a blend of fine aggregates in the concrete manufacturing. The results of the cocopeat sieve test are that cocopeat is included in Region II which is classified as a fine module of slightly coarse grains with a fine module of fine aggregate grains of 2.37. This shows that cocopeat has a fairly good value in normal concrete mixtures but is not suitable for high resistance concrete mixtures that exceed 25 MPa. This was followed by a subsidence test that gave subsidence values for mixtures of concrete with a cocopeat composition of 25%, 50% and 75%, is 7.5 cm; 5.3 cm; and 2.2 cm. While a good subsidence ratio is used in the range of 6-18 cm. In addition, the concrete with a 25% blend of cocopeat has a stronger physical form and there are no fungus growing on the surface of the concrete. Meanwhile, concrete with a mixture of 50% and 75% cocopeat looks more fragile and forms molds on the surface of the concrete. Thus the concrete with a mixture of 25% cocopeat has better results.

Alkali-silica reaction of sanitary ware ceramic wastes utilized as aggregate in ordinary and high-performance mortars

Waste management has been the foremost concern in the last decades. Utilizing sanitary ware ceramic (SWC) wastes in concrete has been found to be beneficial in terms of sustainability and cost in previous studies; however, deleterious alkali-silica reaction (ASR) potential of this waste aggregate, albeit it’s high SiO2 content, has not been taken into account. This study aims to examine ASR potential of SWC wastes as well as the effects of permeability, w/c ratio, and reactive powder content of mixtures on the ASR-induced expansions in detail. Accelerated mortar bar, total and capillary water absorptions, and chloride ion penetration tests were conducted for %20, %40, %60, %80, and %100 replacement ratios at the first part of the study. The SWC aggregate showed ASR-induced expansions in “pessimum proportions”. With a 9-day delay, similar patterns (trends) of ASR expansions were observed in the mixtures with a w/c ratio of 0.3 as compared with those of 0.5 w/c ratio. While the ASR expansions had meaningful relations with the water absorption tests and w/c ratio, there was no noteworthy correlation with the rapid chloride ion penetration test results, since the SWC aggregate effected the properties of pore solution. The effect of the finer grains of the SWC aggregate on ASR was investigated in the second part of the study. For this purpose, the SWC aggregate finer than 250 µm was replaced with same sized limestone aggregate. The results revealed that the finer grains of SWC aggregate were responsible for the reductions observed in the first part of the study not due to “pessimum effect” phenomenon but rather to the pozzolanic activity of the finer grains.

Influence of Polymer Modifiers on Selected Properties and Microstructure of Cement Waterproofing Mortars.

This paper presents the results of research on the influence of polymer modifiers: styrene-acrylic copolymer, vinyl acetate/ethylene (EVA), vinyl acetate/acrylic copolymer (VAAc), and VA/VeoVa/acrylic terpolymer on the water permeability and adhesion of cement-containing waterproofing mortars in concrete. The content of the polymers in the composition of the mortars was 15, 20 and 26% (m/m) in relation to the weight of the dry ingredients. Using microscopic methods, an attempt was made to analyse the relationship between the microstructure of the mortars and the properties of these polymers. The EVA and the vinyl acetate/acrylic copolymer, which were used in the form of dry powders, had the most favourable effect on water permeability and adhesion to the concrete substrate. They may prove to be useful for the production of one-component cement-containing waterproofing mortars. On the other hand, the VA/VeoVa/acrylic terpolymer modifier had the least favourable effect on the tested properties. For mortars with this modifier, the desired water-permeability parameters were not achieved. Depending on the amount of polymer modifier, the mortars were characterized by differences in watertightness, as established on the basis of changes in porosity and differences in the adhesion of the cement-polymer paste to the surface of aggregate grains. It was determined that the type of polymer and its dispergation properties influence the water permeability of mortars, as well as their adhesion to concrete substrates.