Coarse Portion Research Articles

Replacement of Coarse and Fine Aggregate in Concrete Pavement Mixtures with Recycled Concrete Aggregate

This study considered the effects of recycled concrete aggregate (RCA) as a replacement of both coarse and fine aggregate in concrete. The coarse portion was replaced by 100% RCA and the fine portion was replaced with RCA at various amounts up to 50%. In addition, fly ash and ground granulated blast furnace slag were utilized as partial replacements of cement. All mixtures were prepared using the twostage mixing approach and the coarse and fine RCA were in a partially saturated condition. The use of RCA fine aggregate (RFA) reduced the concrete strength. However, it was found that the concrete can have a statistically similar compressive strength to concrete with 100% coarse RCA and no RFA. The shrinkage for almost all recycled concrete mixes was statistically similar at early ages, but at later ages, concrete containing RFA can potentially shrink more, especially if slag and fly ash are used to replace cement. The findings suggest that, with proper design, both RCA and RFA can be used in concrete pavement applications.

An Experimental Study on using RCA in Bituminous Mixtures to Create Sustainable Pavement Technique

Due of the extensive infrastructure development that India has been experiencing over the past thirty years, conventional stone aggregates are becoming scarcer and more expensive. However, there are plenty of wastes available, such as those from old concrete structures. Recycled concrete aggregate (RCA) wastes have already been the subject of numerous attempts to repurpose in a variety of building applications, including bituminous pavement layers. It's possible that not all bituminous binders that are frequently employed in Indian paving mixtures are compatible with RCA. The purpose of this experimental investigation is to examine how different types of binders affect the performance of densely graded bituminous mixtures in which RCA is used in place of the coarse portion of traditional stone aggregates. The primary goal of this project was to manufacture dense bituminous macadam (DBM) mixtures in accordance with pertinent Indian criteria. Traditional VG 30 and crumb rubber modified binder (CRMB), two forms of bituminous binders that are commonly used in India, were employed in this procedure. In accordance with the primary objective of this investigation, the blends were created and assessed about their technical attributes such as indirect tensile strength and moisture susceptibility traits like residual stability test and tensile strength ratio. The VG30 bitumen provides better and satisfactory results for combinations with an equal proportion of NA and RCA, taking into account all engineering properties evaluated.

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

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

Influence of Asphalt Concrete Internal Structure on their Packing and Mixture Properties

Hot Mix Asphalt (HMA) pavement is most used in road construction in Iraq due to its economic benefits and ease of maintenance. Several factors are affecting the performance of HMA in the field. One of the major factors is aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) specifies limits for the different types of asphalt layers and allows tolerance for the designed aggregate gradation. In the current asphalt industries, it quite difficult for contractors to achieve the required job mix due to difficulties in sieves control. This study concentrates on the effect of aggregate gradation deviations on the required specification performance. A mid gradation of the binder asphalt mixture was selected as a reference mix and more than 20 deviated mixtures were then prepared. Typical Marshall routine trials were performed on the prepared admixtures to evaluate the mixture properties. Bailey packing theory for mixture evaluation (Coarse Aggregate Ratio CA, Coarse Portion of Fine Aggregate FAc ratio) was also used to understand the impact of these deviations on the particle arrangement and mixture performance. Results showed that minor aggregate deviations do not greatly affect the mixture performance, however, a large deviation in coarse aggregate results in a drop in Marshall properties. Results showed that the Bailey method for performance evaluation is a good tool to understand the mixture performance. This paper aims to study the influence of aggregate gradation deviations on the mixture performance.

Preliminary observations of nivation processes, Cathedral Massif, Northwestern British Columbia, Canada

ABSTRACT Nivation, the suite of weathering and transportation processes attributed to late-lying snowpatches, is linked to the formation of cryoplanation terraces (CTs). CTs resemble giant staircases arranged in repeating sequences of low-gradient treads and steep scarps that extend over hundreds of meters. The nivation hypothesis of CT development has been supported in recent literature examining weathering and erosion trends, but the mechanisms involved in transporting sediment across CT treads remain underinvestigated. Sorted stripes, a type of patterned ground encountered on CT treads, have been linked to efficient snow meltwater flow across low gradients, indicating that these features could be an important component of CT formation. In this study, we use short-term soil thermal and moisture records, particle-size analysis, and apparent thermal diffusivity calculations to examine periglacial processes operating on two incipient CTs. Initial results indicate that: (1) the coarse (boulder and cobble size) portions of sorted stripes function as subsurface channels for sediment transportation across gently sloping CT treads (generally < 12°) by flowing water; (2) hillslope hydrology is an important component of the erosion processes sculpting upland periglacial environments; and (3) late-lying snowbank environments are highly dynamic during warm weather, with large amounts of sediment transported over short periods.

Experimental investigation of the influence of Nano TiO2 on rheological properties of binders and performance of stone matrix asphalt mixtures containing steel slag aggregate

The performance characteristics of bitumens and Stone Matrix Asphalt (SMA) Mixtures modified by Nano TiO2 were evaluated through this study. For investigating the physical and rheological behavior of bitumens, penetration grade, softening point, ductility, linear Amplitude Sweep (LAS), Rotational Viscosity (RV), Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and storage stability tests were implemented. In this study, the steel slag was replaced with a coarse portion of aggregate Moreover, Resilient modulus (Mr), Indirect tensile strength (ITS), dynamic creep, wheel track, moisture susceptibility, and Four-Point Beam Fatigue (FPBF) tests were implemented to evaluate the properties of asphalt mixtures. The physical and chemical properties of aggregates were investigated to evaluate their influence on the behavior of mixtures. LAS and MSCR tests result revealed that the utilization of Nano TiO2 causes an enhanced fatigue life and rutting properties of binders. Based on results, utilization of Nano TiO2 enhances the Mr, rutting properties, ITS, fracture energy, and intermediate temperature behavior of specimens. Also, based on results, replacing a coarse portion of the aggregate skeleton by steel slag aggregate result in improving the rutting resistance of mixtures. At the same time it leads to decrease MR, ITS, TSR, and fatigue resistance of mixtures.

Effect of filler on bituminous base layer containing recycled concrete aggregates

Abstract The use of different filler materials is one of the effective techniques adopted to improve pavement quality and performance. The main purpose of this study is to quantify the influence of filler type on the performance of dense graded bituminous mixes containing recycled concrete aggregate (RCA). This RCA is replacing the coarse portion of the conventional natural aggregates (NA). In this present experimental investigation, the dense bituminous macadam (DBM) mixes according to the relevant Indian specifications are compacted using four different types of fillers, such as cement, stone dust, fly ash and carbon black and conventional VG 30 as binder. Eight different sets of Marshall samples are prepared using RCA and NA representing the coarse aggregate fraction and either of the above four binders. Different mixes thus prepared are evaluated in terms of their Marshall parameters, indirect tensile strength, moisture susceptibility characteristics (tensile strength ratio and retained stability) and resilient modulus. From the experiment conducted in the laboratory, it is found that all the mixes, in general satisfy the requirements in terms of Marshall and moisture susceptibility characteristics. Considering all engineering properties studied the mixes with NA and carbon black (CB) as filler material offered higher results comparable with other mixes. However, the mixtures prepared with RCA also offered a promising result compared to mixtures made with NA.

Net incremental indirect external benefit of manufacturing recycled aggregate concrete

Concrete waste (CW) either reaches landfill with mixed waste or crushed to produce crushed concrete (CC) used as a road-base product in Australia. The coarse portion of CC, referred to as recycled concrete aggregate (RCA) has the potential to be used as an aggregate in structural concrete replacing natural aggregate (NA). The environmental performance of RAC has been studied in comparison to NAC, in terms of direct environmental implications (DEI) concerning the processes in the production chain of these products. However, when replacement at industry level is considered, the implications go beyond the DEI, and affect a series of other products/processes within a system boundary, referred to as indirect environmental implications (IEI). This paper quantifies the key IEI associated with the use of RCA in structural concrete and evaluates the external costs and benefits associated with it using economic evaluation methods. The net benefit associated with the avoidance of landfill of CW, extraction of NA, and transportation of waste and by-products are the major externalities identified and quantified in this paper. Evaluation of these suggest that there is a significant net benefit ranging from 9% to 28% of the price of natural aggregate concrete (NAC) with the production of recycled aggregate concrete (RAC), for RCA replacement rates between 30% and 100%.

Physicochemical Characteristics of Non-Starch Polysaccharides Extracted from Cassava Tubers

This research mainly focused on isolation of non-starch polysaccharide (NSP) from different parts of cassava tuber by using water extraction and to evaluate the effect of NSP addition into flour on nutritional composition, swelling and solubility, pasting properties and dough characteristics by farinograph and extensograph. Three origins of (NSP) extracted were used: cassava peels, coarse and fine portions from cassava flesh. The isolation of NSP was done by using water extraction method and designated as water-extractable (WEP) and water un-extractable non starch polysaccharides (WUP). The percentage yield of WEP (0.24 - 1.64%) from water extraction was significantly lower as compared to WUP (2.58 - 4.33%). Upon the incorporation of 5% NSP, the cassava flour showed lower moisture content compared to the sample without the addition of NSP, while fats and crude fiber content of cassava flours were found to be increased upon the incorporation of 5% NSP from all origins. Swelling power and solubility of cassava flour were being reduced upon the incorporation of 5% of NSP from cassava peel and coarse portion of cassava flesh. The changes in dough characteristics showed that water absorption of the samples upon the addition of 5% NSP into wheat flour was found to be higher compared to control wheat flour. In contrast, dough stability and extensibility, tolerance index, resistance to extension, as well as the work input necessary for dough deformation from wheat flour with addition of 5% NSP resulted lower than control wheat flour. Overall, NSP extracted from cassava peels and coarse portion of cassava flesh performed similar characteristics and functional properties upon the incorporation into the flour.

Financial assessment of manufacturing recycled aggregate concrete in ready-mix concrete plants

Concrete waste is crushed in the present recycling operation to produce crushed concrete (CC), which is mostly used as a road base filler material. The coarse portion of CC, referred to as recycled concrete aggregate (RCA) can be used in structural concrete replacing coarse natural aggregate (NA). The resultant concrete which is referred to as recycled aggregate concrete (RAC), would create a sustainable end use for concrete waste, and reduce the demand for NA, leading to its preservation. However, the concrete industry has been reluctant to embrace production of RAC to its full potential. Beside uncertainty regarding material performance, options available to effectively set up the existing plant operations to manufacture RAC is yet to be explored. This paper attempts to simulate the manufacturing set up to produce RAC by integrating processes involved in concrete waste recycling and readymix concrete (RMC) production environments. It presents a model to evaluate the financial effect of manufacturing RAC in lieu of normal concrete, calibrated with data from RMC manufacturing and recycling plants. Analysis of the response to produce RAC highlights that the price of RAC differ significantly based on the type of RMC manufacturing plant and the cement content of the mix. It is observed that it is highly probable that the price of RAC is 0–10% higher than that of natural aggregate concrete (NAC). Probabilistic estimation of the price difference between RAC and NAC concludes that RMC plants having aggregate feeding mechanism with front-end loader (FEL) would be an appropriate entry for industrial scale manufacturing of RAC.

Experimental and Numerical Investigation of Stress Condition in Unstable Soil

In unstable soils, a special erosion process termed suffusion can occur under the effect of relatively low hydraulic gradient. The critical hydraulic gradient of an unstable soil is smaller than in stable soils, which is described by a reduction factor α. According to a theory of Skempton and Brogan (1994) [1], this reduction factor is related to the stress conditions in the soil. In an unstable soil, the average stresses acting in the fine portion are believed to be smaller than the average stresses in the coarse portion. It is assumed that the stress ratio and the reduction factor for the hydraulic gradient are almost equal. In order to prove this theory, laboratory tests and discrete element modelings are carried out. Models of stable and unstable soils are established, and the stresses inside the sample are analysed. It is found that indeed in unstable soils the coarse grains are subject to larger stresses. The stress ratios in stable soils are almost unity, whereas in unstable soils smaller stress ratios, which are dependent on the soil composition and on the relative density of the soil, are obtained. A comparison between the results of erosion tests and numerical modeling shows that the stress ratios and the reduction factors are strongly related, as assumed by Skempton and Brogan (1994) [1].

Effect of Pozzolan Content and Fineness on Early Hydration of Interground Blended Cements

The chemical composition and heat evolution of <45 μm (fine), and > 45 μm (coarse) portions of interground, natural pozzolan-blended cements were investigated. Cements with four different pozzolan contents were ground to 300 m2/kg, 500 m2/kg, and 600 m2/kg fineness and sieved through a 45 μm sieve. Clinker, pozzolan, and gypsum contents in the fine and coarse portions after sieving were determined and compared with the unsieved cements. Heat of hydration evolution of the samples were determined up to 48 h using isothermal calorimetry. The fine portions of the cements always contained more gypsum, had higher pozzolan-to-clinker ratios, and slightly higher tricalcium silicate contents, which influenced the rate of heat development at early ages. The fine portions contribute more to the total early heat evolved than the coarse portions. A small amount of pozzolan enhances early hydration. The heat evolved up to 24 h was related linearly to the heat evolved up to 48 h. Such observations could be useful in the modeling of early hydra-tion of blended cements.

Use of unconventional aggregates in hot mix asphalt concrete

The study investigates use of dolomite sand waste as filler or/and sand material plus blast oxygen furnace steel slag as fine and coarse aggregate for design of high performance asphalt concrete. Both environmental and economic factors contribute to the growing need for the use of these materials in asphalt concrete pavements. This is particularly important for Latvia, where local crushed dolomite and sandstone do not fulfill the requirements for mineral aggregate in high and medium intensity asphalt pavements roads. Annually 100–200 thousand tons of steel slag aggregates are produced in Latvia. However, it has not been used extensively in asphalt pavement despite of its high performance characteristics. Dolomite sand waste, which is a byproduct of crushed dolomite production, is another widely available polydisperse by-product in Latvia. Its quantity has reached a million of tons and is rapidly increasing. This huge quantity of technological waste needs to be recycled with maximum efficiency. Various combinations of steel slag, dolomite sand waste and conventional aggregates were used to develop asphalt concrete AC 11 mixtures. The mix properties tests include resistance to permanent deformations (wheel tracking test, dynamic creep test) and fatigue resistance. Laboratory test results showed that asphalt concrete mixtures containing steel slag and local limestone in coarse portion and dolomite sand waste in sand and filler portions had high resistance to plastic deformations and good resistance to fatigue failure

Rendering the loss of strength in dry concretes with addition of milled asphalt through microscopic analysis

Milled asphalt removed from old pavement carpets requires tenable handling easily reachable through its incorporation within other paving materials. This work deals with the effects of such incorporation to dry compacted concretes. Fine, intermediate, coarse and whole portions of milled asphalts were blended to a reference concrete. Mechanical tests disclosed remarkable losses on its strengths and modulus of elasticity; for the stereoscope and scanning microscopy pointed out impaired transition zones between the cement paste and the milled aggregates involved by thin asphalt films. Nevertheless, the mechanical results shown that the concretes with incorporated milled asphalt aggregates are suitable for use in pavement layers as bases and sub-bases even with reduced mechanical parameters.

Laboratory evaluation of warm mix asphalt mixtures containing electric arc furnace (EAF) steel slag

This paper presents the results of a laboratory study which was aimed to verify possibility of using electric arc furnace (EAF) steel slag (SS) in substitution of natural limestone (LS) aggregates in warm mix asphalt (WMA) mixture. The SS was used as fine and coarse portion of aggregate gradation in HMA mixtures, and as coarse portion of aggregate gradation in WMA mixture. The surface texture of both LS and SS aggregates was observed through scanning electron microscope (SEM). The results illustrated that the porosity and the roughness of the SS aggregate are higher than that of the LS aggregate. Moreover, laboratory tests results indicated that use of coarse SS aggregate in WMA mixture enhances Marshall stability, resilient modulus, tensile strength, resistance to moisture damage and resistance to permanent deformation of the mixture. Hence use of coarse electric arc furnace steel slag aggregate in production of WMA mixture is recommended.

Asphalt concrete performance with conventional and waste aggregates

This paper investigates the use of dolomite sand waste and BOF steel slag for replacing conventional fine and coarse aggregates for design of high performance asphalt concrete. Annually 200 thousand tons of steel slag are being produced in Latvia making it the most available waste aggregate. Dolomite sand waste, which is co-product of crushed dolomite production, is the second widely available waste material in Latvia. At the same time local crushed dolomite and sandstone does not fulfill the requirements for mineral aggregate in high and medium intensity roads. This has raised great interest of highway engineers to find locally available and waste materials as substitute for natural mineral aggregates. This research has showed that physical and mechanical properties of steel slag aggregates and dolomite waste sand are comparable with the characteristics of natural aggregates. Sixteen different combinations of steel slag, dolomite sand waste and conventional aggregates were used to develop AC 11 asphalt mixtures with modified and unmodified bitumen. The mixture performance tests include resistance to permanent deformations (wheel tracking test, dynamic creep test) and fatigue resistance. Tests results showed that asphalt concrete mixture combinations containing steel slag and local limestone in coarse portion and dolomite sand waste in sand and filler portions had high resistance to plastic deformations and good resistance to fatigue failure.

Performance of asphalt concrete with dolomite sand waste and bof steel slag aggregate

The rapid growth of traffic loads in Latvia increases the demands for asphalt carrying capacity on large motorways. The dolomite and sandstone that can be found in Latvia lacks the mechanical strength and for most of the large motorways the aggregates are imported from other countries causing increase of costs and growth of emissions from transportation. On the other hand, large amounts of Basic Oxygen Furnace (BOF) steel slag aggregates with good qualities are being produced in Latvia and put to waste. During the recent decades, the dolomite sand waste has also been accumulated and its quantity has reached a million of tons and is rapidly increasing. This huge quantity of technological waste needs to be recycled with max efficiency. The lack of experience in the use of steel slag and dolomite sand waste requires an accelerated evaluation of the asphalt performance-based characteristics. This paper presents the testing results of dense graded asphalt concrete AC 11 mixtures made of four types of aggregate: steel slag, dolomite sand waste, conventional imported dolomite aggregates and conventional local crushed quartz sand that were proportioned to develop a mixture that would satisfy the requirements of permanent deformation and stiffness. Analysis of the results showed that the mixes with steel slag and dolomite waste sand or unconventional aggregate combination with dolomite in coarse portion, crushed quartz sand in sand portion plus dolomite waste sand in sand and filler portions had high resistance to plastic deformations and fatigue failure. These mixes can fully satisfy and in some cases significantly overcome the requirements of local asphalt specifications for highly loaded motorways.

Performance Characterization of Bituminous Mixtures With Dolomite Sand Waste and BOF Steel Slag

Abstract The rapid growth of transport load in Latvia increases the demands for asphalt carrying capacity on large motorways. The limestone and sandstone that can be found in Latvia lack the mechanical strength and, for most of the large motorways, the aggregates are imported from other countries causing increase of the costs and growth of emissions from transportation. On the other hand, large amounts of basic oxygen furnace (BOF) steel slag aggregates with good qualities are being produced in Latvia and put to waste. During recent decades, the dolomite sand waste has been accumulating and its quantity has reached a million tons and is rapidly increasing. This huge quantity of technological waste needs to be recycled with maximum efficiency. The lack of experience on the use of steel slag and sand waste requires an accelerated evaluation of the asphalt performance-based characteristics. This paper presents the testing results of different combinations of steel slag, dolomite sand waste, and local limestone aggregates that were proportioned to develop a mixture that would satisfy the requirements of permanent deformation and fatigue. Analysis of the results showed that mixes with steel slag and local limestone in coarse portion and dolomite sand waste in sand and filler portions had high resistance to plastic deformations and good resistance to fatigue failure. These mixes can fully satisfy and, in some cases, significantly overcome the requirements of local asphalt specifications for highly loaded motorways.

Experimental investigation of stone matrix asphalt mixtures containing steel slag

Significant quantities of steel slag are produced as by-product every year from steel industries in Iran. Although it can be used as an artificial source of aggregates, it is sent to landfills for disposal. The disposal of steel slag occupies a significant portion of landfills and causes many serious environmental problems. This study aims to investigate the feasibility of utilizing steel slag aggregates in Stone Matrix Asphalt (SMA) mixtures. The results show that the use of steel slag as the coarse portion of aggregates can enhance Marshall stability, resilient modulus, tensile strength, resistance to moisture damage and resistance to the permanent deformation of SMA mixtures.

Performance Based Evaluation on the Use of Different Waste Materials in Asphalt

The dolomite and sandstone that can be found in Latvia, lacks the mechanical strength and for most of the large motorways the aggregates are imported from other countries causing increase of the costs and growth of emissions from transportation. On the other hand, large amounts of BOF steel slag aggregates with good qualities are being produced in Latvia and put to waste. During the recent decades, the dolomite sand waste has been accumulating and its quantity has reached a million of tons and is rapidly increasing. This huge quantity of technological waste needs to be recycled with maximum efficiency.The lack of experience on the use of steel slag and dolomite sand waste requires an accelerated evaluation of the asphalt performance-based characteristics. This paper presents the testing results of dense graded asphalt concrete AC 11 mixtures made of four types of aggregate: steel slag, dolomite sand waste, conventional imported dolomite aggregates and conventional local crushed quartz sand that were proportioned to develop a mixture that would satisfy the requirements of permanent deformation and stiffness. Analysis of the results showed that mixes with steel slag and dolomite waste sand or unconventional aggregate combination with dolomite in coarse portion, crushed quartz sand in sand portion and dolomite waste sand in sand and filler portions had high resistance to plastic deformations. These mixes can fully satisfy and in some cases significantly overcome the requirements of local asphalt specifications for highly loaded motorways.