Alternative Aggregate Research Articles

Sustainable alternative aggregates: Characterization and influence on mechanical behavior of basalt fiber reinforced concrete

Demands to assess the feasibility of utilizing alternative sustainable aggregates in concrete have been raised because of the rapid depletion of virgin aggregates resources. In this study, a comparison of the physio-chemical properties of commonly used natural gabbro aggregates (NGA) and natural limestone aggregates (NLA) and their possible sustainable alternatives recycled concrete aggregates (RCA) and steel slag aggregates (SSA) is presented. The suitability of these alternate aggregates is assessed through several standardized tests. Chemical compositions, mineralogical and morphological properties of these aggregates are also reported. To determine the possible leachates of hazardous metals into the environment when used as concrete aggregates, the inductively coupled-plasma atomic emission spectroscopy was carried out on acid digestions of these aggregates. Additionally, basalt macro-fibers (BMF) were incorporated to improve the mechanical properties of concrete made with RCA and local NLA which are deemed as weak and unfit for use as aggregates in structural concrete. Experimental results revealed that both RCA and SSA could be used as sustainable alternative aggregates to have a cleaner production of structural concrete. They had acceptable leachate limits of the hazardous elements. The soundness test results and expansion under autoclave of SSA were well below the acceptable limits. The concrete made with SSA showed higher mechanical properties than the concretes made with other aggregate types. As expected, BMF improved the mechanical properties of concrete made with the low-strength NLA and RCA.

Propriedades mecânicas de concretos asfálticos dosados com rejeitos do beneficiamento magnético a seco do minério de ferro

Este estudo avalia o comportamento mecânico de três misturas asfálticas, uma de referência e duas com substituição dos agregados naturais por rejeitos finos de minério de ferro. Os rejeitos são provenientes de uma inovadora tecnologia de obtenção, a separação magnética a seco. A metodologia consistiu de um programa experimental dividido em quatro etapas: (i) determinação das características físicas, mineralógicas e ambientais dos agregados; (ii) obtenção as propriedades reológicas e empíricas do cimento asfáltico de petróleo; (iii) dosagem dos materiais de revestimento asfáltico pela metodologia Superpave; (iv) realização de ensaios de dano por umidade induzida, resistência à tração por compressão diametral, fadiga à tensão controlada, módulo de resiliência e uniaxial de cargas repetidas nas misturas asfálticas. Os concretos asfálticos que continham agregados alternativos apresentaram propriedades de rigidez e fadiga similares à mistura de referência. Entretanto, com a utilização de rejeitos de minério de ferro houve maior susceptibilidade ao acúmulo de deformações permanentes.

Development of Self Consolidating Concrete (SCC) Using Crushed Waste Clay Brick as Alternative Aggregate

In housing construction, concrete are materials that will be used extensively to produce a wall structure that accommodates the load. However, the problem is the cost of producing by using natural resources, as it is a major mineral is difficult to find sufficient natural aggregate supply sources since high demand. Therefore, the lack of natural aggregate and its increasing demand leads to an alternative to be developed to replace the natural aggregate. This study investigated the effect of utilization of waste clay brick in Self Compacting Concrete (SCC) on its properties and performance. The waste clay brick (WBS) was replaced as fine aggregate in SCC from 10% to 30%. As the amount of waste clay brick in SCC increases, its workability and also Ultrasonic Pulse Velocity (UPV) quality decreases while the water absorption increases. The highest average compressive strength achieved was 43.3 MPa and for splitting tensile strength was 12 MPa respectively; both at 25% of WCB replacement. All test results showed that the optimum percentage to replace waste clay brick in SCC is 25% and it has the potential to be replaced as fine aggregate in SCC.

Fresh properties of self-compacting concrete incorporating electric arc furnace oxidizing slag (EAFOS) as coarse aggregate

This study investigates the fresh properties of self-compacting concrete incorporating electric arc furnace oxidizing slag as coarse aggregate. A binary blend of 30% fly ash and cement was utilized as binder to improve the performance of concrete in its fresh state. Concrete grades M20, M30 and M40 were developed by replacing natural coarse aggregate with 50% and 100% electric arc furnace oxidizing slag (EAFOS) aggregate. Thus, fresh properties of SCC; slump flow, T500, U box, V funnel and L-box were determined. From the evaluation of fresh properties, it is shown that the grades of concretes developed passed the set standard limits for SCC. The results showed that 50% EAFOS addition to SCC will not deter its fresh properties in any way, however, when EAFOS was added up to 100%, there was reduction in workability properties of the concrete. The study showcases the significant potential of EAFOS as an alternative aggregate in SCC. Thus, the data provided in this study will be useful for concrete constructors.

Pullout behaviour of geosynthetics in a recycled construction and demolition material – Effects of cyclic loading

Abstract In recent years, the use of construction and demolition (C&D) materials as alternative aggregates in geotechnical engineering applications, such as embankments, pavement subbase layers and geosynthetic-reinforced structures has raised increasing attention from researchers and practitioners worldwide. On the other hand, geosynthetics, particularly geogrids and high strength geotextiles, are used as a reinforcement material in some of those applications. When these infrastructures are subjected to repeated loadings (e.g. traffic, wave and seismic loads), the understanding of the interaction properties at the backfill-geosynthetic interfaces under cyclic loading conditions is of primary interest. This paper describes an experimental study carried out using a large-scale pullout test apparatus to assess the load-strain-displacement behaviour of two geosynthetics embedded in a recycled C&D material under cyclic and post-cyclic loading conditions. Test results show that cyclic loading can measurably reduce the post-cyclic pullout resistance of the geotextile (up to 15%), when compared to that obtained from the benchmark monotonic test. Conversely, the cyclic loading did not significantly influence the pullout resistance of the geogrid. The cumulative cyclic displacements over the length of the geosynthetics were found to increase with the load amplitude and the pre-cyclic pullout load level. Moreover, under identical test conditions, the accumulated cyclic deformations along the geotextile length consistently exceeded those for the geogrid, possibly due to the lower tensile stiffness of the geotextile at low strains.

Bond performance of reinforced alkali-activated composites using water-quenched slag as alternative fine aggregates

Pull-out tests and beam-end tests were conducted to study the bond performance of reinforced alkali-activated composites (AAC). A steelmaking waste, water-quenched slag (WQS), was employed as an alternative to river sand fabricating the AAC. The pull-out tests aimed at examining the bond performance of the AAC incorporating different volumes of WQS and embedded different reinforcements. The beam-end tests simulated the stress mode of flexural member and studied the effect of some structural parameters on the bond performance, including the thickness of the concrete covering (Cc), the bond length (la) and the space between two adjacent stirrups (Sst). The results indicated that AAC brought reinforced-concrete specimens better bond performance compared to the ordinary Portland cement (OPC) concrete because of the chemical adhesion between the AAC and steel reinforcements. The involvement of WQS contributed to strong friction effect between the rebar and mortar matrix, which played a role in improvement of bond performance. The results of the beam-end tests revealed that the thickness of concrete cover was an influential factor on the bond performance, and the influence of the other structural parameters on the bond performance relied on the thickness of concrete cover. Based on the tests results, a fitting model was proposed to predict the bond strength using the splitting tensile strength of AAC.

The Influence of Steel Slag as Alternative Aggregate in Permeable Concrete Pavement

This study identifies the pervious concrete with a high direct runoff on the pavement incorporating steel slag. This study is progressing in two stages i.e. 1 st stage is obtaining the best mix design by using cubic concrete samples with dimension of 100mm height based on 7 days compressive strength test. Indeed, different proportion of aggregate and ratio were tested in order to select the highest compressive strength which has reached 10.9 MPa in the first 7 days of curing. The cylindrical concrete sample with the dimension of 200 x 100 mm was used in the 2 nd stage. In addition, steel slag was used in the 2 nd stage besides the granite aggregate. In fact, three different percentages of steel slag are involved; 50% Steel Slag and 50% Granite; 30% Steel Slag and 70% Granite; and 70% Steel Slag and 30% Granite. Hydrologically, 13.8 mm/s is the highest Infiltration rate that pervious concrete has reached which has been recorded throughout permeability test. The rainfall intensity which plays an important role on the pavement was identified. Thus, intensity distribution frequency curve was developed using MSMA and compared within filtration rate results of pervious concrete. Mix design ten (M10) has the ability to perform efficiently during highest rainfall intensity meanwhile strength needed to be increased since 10.9 MPa in the first 7 days of curing is not sufficient.

Experimental study of waste tire rubber, wood-plastic particles and shale ceramsite on the performance of self-compacting concrete

In recent decades, the utilization of waste tires, plastic and artificial shale ceramsite as alternative fine aggregate to make self-compacting concrete (SCC) has been recognized as an eco-friendly and sustainable method to... | Find, read and cite all the research you need on Tech Science Press

Money Supply, Stock Prices and the Efficient Market Hypothesis: The Case of Malaysia

The purpose of the present study is to investigate the empirical relationships between money supply and stock prices in the Kuala Lumpur Stock Exchange (KLSE) using monthly data that span from January 1978 to September 1992. More specifically, we tested market informational efficiency in the KLSE by testing the causal relationships between money supply and stock prices using the co-integration technique. In the analysis, we used alternative monetary aggregates namely, the Simple-Sum and Divisia monies. Results from- our error-correction model suggest that market informational efficiency hypothesis can be rejected for KLSE with respect to the growth of money supply (for both Simple-sum and Divisia monetary aggregates).

Preliminary studies on calcinated chicken eggshells as fine aggregates replacement in conventional concrete

The growing demands for cement have proportionally affect the environment such as ecosystem alterations and pollutions. Therefore, this study was conducted to investigate the potential of chicken eggshell as an alternative fine aggregate in concrete mixture due to its similar high calcium carbonate (CaCO3) content with limestone. The experimental program was developed by substituting the sands (by volume) in the conventional concrete formulation with 10%, 20%, 30% and 40% of chicken eggshell powder (CEP). The eggshells were calcinated at 900 °C to produce calcium oxide (CaO) or quicklime. The samples were undergoing wet curing for the period of 28 days. Primary concrete characteristics such as pH, carbonation depth, compressive strength and sorptivity were studied. From the results, the additions of calcium oxide in the aggregates are strongly pronounced in carbonation rate (up to 42%) and compression strength (up to 58.4%). It is believed that the mechanical component of the bond has been improved with the additional calcium oxide. There are no significant differences of pH and sorptivity values between CEP and conventional concretes. The highest replacement percentage of 40% is beneficial for acceleration rate of carbonation and compressive strength. However, formulation modification is not required if the specifier is looking for pH and sorptivity performances enhancement.

Workability Strength and Elastic Properties of Cement Mortar with Pond Ash as Fine Aggregates

Natural sand obtained from river beds are normally used as fine aggregates in preparation of cement mortar. Due to increased demand and excessive extraction of river sand; there is an acute shortage in different parts of the world. Various research agencies are striving to investigate the properties of mortar with alternate fine aggergates such as M-sand, Pond ash, slag sand etc. Present study investigates flow, strength, density and elastic properties of cement mortar at various replacement levels of alternate fine aggregate, Pond Ash. Masonry and two types of plastering mortars were prepared with river sand as fine aggregate. Flow characteristics of masonry and plastering mortar were studied till attainment of flow of 85 and 110% respectively. River sand was replaced by pond ash at replacement levels of 20, 40, 60, 80, and 100% and flow test was conducted. Effect of replacement on flow characteristics was studied. Mortar cubes and prisms were cast and tested for compressive strength and Modulus of elasticity. Results indicate that water cement ratio required to attain the target flow increases with pond ash. The compressive strength of mortar decreases with increase of pond ash. Reduced density and modulus of elasticity were observed in pond ash mortar when compared to river sand mortar. Hence pond ash can be used as an alternate to river sand in production of lean mortar and blocks

Mixed aggregation functions for outliers detection

A scenario that often encounters in the event of aggregating options of different experts for the acquisition of a robust overall consensus is the possible existence of extremely large or small values termed as outliers in this paper, which easily lead to counter-intuitive results in decision aggregation. This paper attempts to devise a novel approach to tackle the consensus outliers especially for non-uniform data, filling the gap in the existing literature. In particular, the concentrate region for a set of non-uniform data is first computed with the proposed searching algorithm such that the domain of aggregation function is partitioned into sub-regions. The aggregation will then operate adaptively with respect to the corresponding sub-regions previously partitioned. Finally, the overall aggregation is operated with a proposed novel consensus measure. To demonstrate the working and efficacy of the proposed approach, several illustrative examples are given in comparison to a number of alternative aggregation functions, with the results achieved being more intuitive and of higher consensus.

Modification of AC Thermal Properties to Mitigate UHI Effects

Abstract An analysis of the asphalt concrete (AC) pavement material properties that affect surface temperatures is presented. These properties affect the contribution to the urban heat island effects. Its goal is to analyze the effect of various alternative aggregate materials, such as limestone, silica, polymer, glass, and graphite, on AC pavement surface temperatures under various environmental conditions. Pavement surface temperatures were analyzed for two extreme weather locations in the United States, namely South Texas and Northern Minnesota. Long-Term Pavement Performance weather data over a year-long period were analyzed for each location using the computer model Temperature Estimate Model for Pavement Structures. The average and range of pavement temperatures were compared at a depth of 0.01 m. It was concluded that the higher the coefficient of thermal conductivity, heat capacity, and albedo of the pavement surface layer, the lower the average and maximum surface temperatures are during the summer months. Graphite was shown as a promising limestone aggregate substitute producing significant reductions in AC surface temperatures. It reduced the peak daily surface temperatures by between 3.5°C and 5°C. On the other hand, the modified AC mixtures showed mechanical properties not quite at par with those of conventional ACs.

Potential use of granite waste sourced from rock processing for the application as coarse aggregate in high-performance self-compacting concrete

The granite waste (GW) generated during mining extraction is responsible for environmental degradation. Millions of tonnes of stored GW are currently still not being reused. This paper describes a disposal process for this material, where GW can be used as an alternative aggregate for advanced concrete. The awareness of the impact of coarse aggregate morphology on the behavior of fresh concrete mixture, as well as on the deformation and compressive strength of the hardened concrete, favors the creation of the efficiency of Self-Compacting High-Performance Concrete (SCHPC). In this study, regular and irregular aggregates separated from granite waste coarse aggregate were analyzed, the morphology of which was described using microscale laboratory tests. As a result of digital image analysis, the morphological parameters of the aggregates were determined and a detailed statistical analysis of these parameters was conducted. Laboratory tests of the properties of fresh concrete mixtures diversified in terms of their share of regular and irregular aggregates, as well as samples of the hardened concrete, were then carried out. Due to the observed important effect of aggregate morphology on the fresh mixture properties of SCHPC, as well as on the mechanical features of hardened concrete, in order to understand the nature of this phenomenon, its mechanism has been explained.

Utilization of red mud as an alternative mineral filler in asphalt mastics to replace natural limestone powder

With the view of reducing the consumption of non-renewable limestone resources, the waste-derived secondary resource can be considered as the limestone powder replacement for hot asphalt mixtures. This study unravels the feasibility of using a red mud-derived alternative filler aggregate to replace the commonly used limestone powder in asphalt mastics, and further improves the red-mud-modified asphalt mastic by using hydrated lime and white mud. The experimental tests, including direct tension (DT), Positest AT-A bonding strength, as well as dynamic shear rheometer (DSR), were performed to characterize the cracking resistance, the moisture damage, the fatigue behavior, as well as the rheological properties of asphalt mastic. Due to surface morphology and mineralogical composition of red mud, its replacement of limestone powder improved the elastic recovery of asphalt mastic, but it had detrimental effect on properties of the cracking resistance, the moisture damage and the fatigue life. When incorporating the hydrated lime and white mud, both materials can improve the low-temperature cracking resistance of red mud asphalt mastic. Moreover, the incorporation of the white mud into the red mud asphalt mastic can enhance its moisture resistance of aggregate-mastic bonding under both short- and long-term moisture attack as well as its fatigue resistance.

Investigation of mechanical and micro structural properties of geopolymer concrete blended by dredged marine sand and manufactured sand under ambient curing conditions

AbstractGeopolymers, an unique class of inorganic polymers are new promising binders which are manufactured by the activation of a solid state alumina‐silicate with a highly alkaline activating solution using thermal drive. In the recent past, geopolymer binders have been found to be the best alternate to cement binders owing to its environmental sustainability (greener materials lead to cleaner environment). Further, its performance in aggressive environment is promising and these binders could become a replacement for cement concrete in aggressive situation where cement concrete turns to be vulnerable. In this paper, an attempt is made to investigate the mechanical and micro structural properties of geopolymer concrete produced using alternative fine aggregates namely dredged marine sand (DMS) and manufactured sand (M‐Sand) in the place of conventional scarce fine aggregate (river sand) under ambient curing conditions. All the tests namely compression, split tensile, flexural and micro structural evaluation have been performed by varying the percentage of DMS and M‐Sand. The experimental investigation followed by micro structural evaluation clearly indicate that DMS can very well be substituted in the place of scarce fine aggregate (river sand) under ambient curing conditions.

Prediction of Particle Packing Density of Alternative Fine Aggregates by Artificial Neural Network Applications

Particle packing density mainly influences the behavior of concrete. Experimental determination of particle packing density is arduous and time-consuming. Thus, artificial neural network (ANN) is a tool that helps in determining particle packing density faster and accurately. ANN is used to predict the properties of the concrete with natural aggregates only. However, utilization of alternative fine aggregates is a need of hour. The aim of this paper is to apply ANN to predict particle packing density of combined aggregates, viz. coarse, intermediate and fine aggregates. In addition, alternative fine aggregates, namely crushed rock sand (CRS), recycled fine aggregate (RFA) and coal bottom ash (CBA) are used. In this study, the main constraints used to design ANN are size distribution and packing density of individual aggregates. Feedforward network is used to determine particle packing density of combined aggregates. A total of 231 experimental datasets are used to train ANN for each alternative fine aggregate, and the results were compared. It was observed that the error percentages are well below 5% of experimental and ANN optimization analyses. The optimum packing proportions for river sand, CRS, RFA and CBA were 40:20:40, 30:30:40, 30:30:40 and 30:20:50, respectively.

Alkali-activated metakaolin mortars using glass waste as fine aggregate: Mechanical and photocatalytic properties

In the present study, properties such as density, absorption, porosity, compressive strength, thermal conductivity and photocatalytic activity of alkali-activated mortars based on metakaolin added with TiO2 particles were evaluated. TiO2 particles were incorporated in proportion of 10 wt%. Ground glass (GB) obtained from glass bottle waste was used as an alternative fine aggregate in proportion up to 100% as replacement of natural sand (S). The alkaline activator was a mix of potassium silicate and hydroxide. The photocatalytic activity was measured by the removal of Rhodamine B and the microstructure of the developed material was studied by scanning electron microscopy. The results obtained in this study reveal a reduction in the percentage of absorption of 16.3%, and porosity of 7% for mortars when S is replaced by GB. The mortar prepared with 100% GB reached a compressive strength of 31.5 MPa compared to 28.0 MPa for reference mortar (100% S). The thermal conductivity was reduced by approximately 25%. Finally, the self-cleaning photocatalytic capacity using GB as fine aggregate increased 72.4%. This type of cementitious materials contributes to mitigate environmental pollution and reduces the maintenance costs of structures.

Evaluating Potential Sources of Aggregation Bias with a Structural Optimization Model of the U.S. Forest Sector.

Structural economic optimization models of the forestry and land use sectors can be used to develop baseline projections of future forest carbon stocks and annual fluxes, which inform policy dialog and investment in programs that maintain or enhance forest carbon stocks. Such analyses vary in terms of the degree of spatial, temporal, and activity-level aggregation used to represent forest resources, land cover, and markets. While the statistical and econometric modeling communities widely discuss the effects of aggregation bias and have developed correction techniques, there is limited prior research investigating how aggregation bias may affect structural optimization models. This paper explores potential aggregation bias using the Land Use and Resource Allocation model (LURA), a detailed spatial allocation partial equilibrium model of the U.S. forest sector. We ran a series of projections representing alternative aggregation approaches including averaging forest stocks at plot, county, state, and regional levels, across one-, five, or ten-year age classes, and by two or fourteen forest types. We compared the resulting projections of forest carbon stocks and harvesting activities across each aggregation scenario. This allows us to isolate the effect of aggregation on key variables of interest (e.g., GHG emissions and supply costs), while holding all other structural characteristics of the modeling framework constant. We find that age-class and forest type aggregations have the greatest impact on modeling results, with the potential to substantially impact market and greenhouse gas projections. On the other hand, spatial aggregation has a small impact on national carbon stock projections. Importantly, regional results are greatly impacted by different aggregation approaches, with projected regional cumulative carbon stocks differing by more than 25% across scenarios.

Preparation and properties of reactive powder concrete by using titanium slag aggregates

In this research, titanium slag (TS) was used as an alternative aggregate to prepare reactive powder concrete (RPC). The mechanical properties, hydration characteristics, and interface structure of the RPC was investigated. The results showed that the porous, low-activity TS aggregate had high water adsorption and proper secondary hydration during moulding and hardening. This accelerated the early-age hydration reaction of RPC and significantly improved the interfacial structure between paste and aggregate. Ca2+, Mg2+, and Si4+ present in TS leached out and generated additional C-S-H around the aggregate during hydration, which filled the gap between paste and aggregate