Siliceous Aggregates Research Articles

Predictive quantitative model for assessing the asphalt-aggregate adhesion quality based on aggregate chemistry

Asphalt-aggregate adhesion quality is a key factor in the mechanical performance of asphalt pavements. This work presents a predictive model of moisture damage in asphalt-aggregate systems based on aggregate chemistry. The study included seven siliceous aggregates and two calcareous aggregates, and one source of asphalt binder. Specimens composed of an aggregate core, a 20 μm thick asphalt film and a metallic stub were tested via a pull-off debonding experimental setup after multiple water conditioning processes. The experimental results i.e. maximum load at failure, Fmax , work of fracture, Wf , and adhesive failure area at the surface of the aggregate, A % show that for siliceous aggregates, the SiO2 content increases moisture susceptibility while the opposite is seen for Fe2O3 and CaO, and that for calcareous aggregates, moisture susceptibility increases with their SiO2 content. These results were used to propose, for the first time, an empirical moisture damage predictive model for siliceous aggregates based on aggregate chemistry.

Environmental and mechanical impacts of waste incinerated acidic sludge ash as filler in hot mix asphalt

In this paper, the feasibility of employing waste incinerated acidic sludge ash (IASA) as a viable alternative to the mineral fillers in hot mix asphalt (HMA) with a siliceous aggregate source from environmental and mechanical aspects was investigated. Environmental impacts were analyzed considering four factors: ignitability, reactivity, corrosivity using pH test, and toxicity using toxicity characteristic leaching procedure test. Mechanical properties of mixtures were obtained using indirect tensile strength (ITS), resilient modulus, moisture sensitivity, and permanent deformation tests. Results revealed that all metal concentrations leached from IASA modified HMA and pH of IASA modified samples comply with the United States Environmental Protection Agency (EPA). It was also demonstrated that incorporation of IASA in HMA leads to enhancement of HMA mechanical properties. ITS and resilient modulus of mixtures containing IASA were higher than those of the control mixtures. Replacing 50 wt.% of siliceous stone dust filler with IASA causes an increment about twofold in the flow number and reduction of the rut depth by about 26 % compared to those of the control sample. Moreover, the hydrophobicity and impermeability properties of IASA modified HMA and the stronger interfacial reaction between asphalt and IASA, resulted in improving the moisture susceptibility of the mixture containing IASA. This paper provides more insights on IASA waste management through its application in an environmentally friendly HMA.

Hydraulic Tiles Produced with Fine Aggregates and Pigments Reclaimed from Iron Ore Tailings

Confronted with the growing ecological awareness of the consumer market, the construction industry has been seeking strategies to promote a higher insertion of waste in the production chain while contributing to the technological improvement of processes and products, as well as mitigation of social and environmental impacts and, at the same time, conferring intangible value to the product. In this sense, the present work describes how iron ore tailings (IOT) can be used in the production of cement-based (hydraulic) tiles. The physical, chemical, and mineralogical characterizations carried out demonstrated that the IOT beneficiation (segregation) process resulted in a high-quality siliceous aggregate and a Fe-rich clay. The latter can be used as a pigment, whose pigmentation and cementing potentials improve with calcination and grinding. Compared to hydraulic tiles prepared with conventional materials, those obtained with the IOT-based materials displayed a pleasing appearance and the expected physical–mechanical performance.

Factors Affecting Kinetics and Gel Composition of Alkali–Silica Reaction in Alkali-Activated Slag Mortars

Alkali activation of metallurgical slags produces low-carbon cementitious binders for sustainable concrete production. However, the potential deleterious reaction of internal alkalis in alkali-activated slag (AAS) with siliceous aggregates is a serious durability concern. In this work, the alkali–silica reaction (ASR) in alkali-activated ground granulated blast furnace slag mortars with various activator dosages and types, aggregate reactivity, as well as incorporation of pulverized fly ash or silica fume is studied. The ASR-induced length expansion and microstructural damage in AAS mortars are studied by a modified accelerated mortar bar test and scanning electron microscopy with X-ray energy-dispersive spectroscopy. The results show that the kinetics of ASR-induced damage, as well as the gel composition and spatial distribution, in AAS mortars is highly dependent on the alkali dosage, activator type, and aggregate reactivity. The ASR-induced length expansion is approximately proportional to the volumetric fraction of dissolved glassy aggregates. However, AAS mortars show noticeable autogenous shrinkage at the initial stage of immersion, making the conventional judgment of ASR risks using length expansion as the sole indicator invalid. The dissolution kinetics of aggregate, which is influenced by the level of alkalinity and availability of reactive silica, seems to be the rate-limiting reaction of ASR-induced damage in AAS mortars under accelerated testing conditions.

Thermal conductivity of concrete at high temperatures for thermal energy storage applications: Experimental analysis

Thermal conductivity plays an important role in energy storage when the materials are charging and discharging. This paper presents an experimental investigation of the evolution of thermal conductivity up to 600 °C in different concretes. Moreover, the thermal conductivity was measured during thermal fatigue cycles when temperature ranged between 300 and 600 °C, simulating the operation conditions in a storage system of molten salts in a Concentrating Solar Power Plant (CSP). Five concrete compositions were analysed using diverse types of aggregates with different thermal response, covering a wide range of the initial thermal conductivity. The results confirm that the loss of thermal conductivity with temperature during the first heating is mainly due to the free water loss. Moreover, the type of aggregate influences the overall thermal performance of concrete due to its thermal conductivity and the volumetric differences with the cement paste. Siliceous aggregates underwent the highest decrease of thermal conductivity of concrete (+50%) with regard to room temperature. Regarding the cooling phase, thermal conductivity recovers between 20% and 40% depending on the type of aggregate. The outcomes of the present study demonstrate that the assumption of a constant thermal conductivity value in numerical simulations to predict its thermal capacity for energy storage is not appropriate.

Analytical characterization of the almohad rammed-earth wall of Cáceres, Spain

The aim of this work is to characterize the Rammed-Earth from the Almohad wall of Cáceres, Spain. Since the knowledge on the mechanical and physical properties of this historical structure is scarce, despite the significance of this archaeological ensemble, declared a World Heritage Site by UNESCO in 1986, this work contributes with the knowledge of the construction mode of the Rammed-Earth, providing useful information about the original building techniques, the raw materials and the production technology used in this defensive structure built eight centuries ago. An advanced knowledge of the materials state used in the construction of this historical wall is required for a possible reliable restoration and preservation in which compatible materials may be used. For this purpose, an experimental campaign was carried out on the constituent materials of this monument, mainly composed by Rammed-Earth. In this work 12 different zones of the old city wall of Cáceres were analyzed by X-ray diffractometry, thermogravimetric analysis, infrared spectroscopy, compressive strength and mercury intrusion porosimetry. The results, presented and discussed, showed that this Rammed-Earth can be considered like an authentic concrete, made of lime and siliceous aggregates, mainly coming from granites and quartzites fragments, abundant local geomaterials, and that their good physical and mechanical properties are comparables to other ancient concretes. With this work, it is possible to fill the gap that exists in this field, characterizing the materials used in this ancient rampart, never previously studied.

Prediction of temperature distribution and fire resistance of RC slab using artificial neural networks

This paper present the use of artificial neural networks as alternative approach for predicting the temperature distribution of RC slab and its fire resistance according thermal criteria (the temperature of reinforcement criteria and the temperature of unexposed surface criteria). The predicted fire resistance compared with target fire resistance in codes of EN 1992-1-2 and ACI 216.1. Two set of data are used in training and testing two different ANNs. Dataset 1 which consists of temperature profile for siliceous aggregate concrete slab presented in EN 1992-1-2. Dataset 2 represents the temperature profile for carbonate concrete slab presented in ACI 216.1. Two ANNs models have been constructed. The first ANN is used to predict the temperature distribution in RC section. Second ANNs have been used to predict the fire resistance of RC slab. These models are used to study the effect of different parameters include aggregate type, slab thickness, concrete cover and reinforcement type on the fire resistance of RC slab. The results showed that ANNs can predict the temperature in RC slab section and its fire resistance with a good accuracy. Also, the ANNs models are succeed in predicting the effect of different parameters in the fire resistance of RC slab.

Study on the effect of selected parameters on the alkali-silica reaction of aggregate in ground glass fiber and fly ash-based geopolymer mortars

In this study, the effect of selected parameters on the alkali-silica reaction (ASR) of aggregate in ground glass fiber (GGF) and fly ash-based geopolymer mortar was investigated. This work focuses on three main objectives: 1) to study the effect of the binder composition, 2) to study the effect of the ASR accelerating environment, and 3) to study the effect of the chemical/mineralogical composition of aggregate, on the ASR behavior of geopolymer mixtures. To study the effect of paste composition on the ASR behavior of GGF-based geopolymer mortars were compared to a fly ash-based geopolymer mixture and an ordinary Portland cement mixture. To investigate the effect of curing condition, mortar bars were cured in two ASR accelerating environments; mortar bars were either immersed in a high alkali solution or exposed to a high relative humidity environment. To evaluate the effect of the chemical composition of aggregate, two types of ASR-reactive aggregate, one mainly composed of glassy silica and one mainly composed of limestone with chert impurities were used for the ASR study, and the results were compared to a mixture with non-reactive limestone aggregate. To evaluate the ASR behavior of geopolymer mixtures, length expansion, and the change in dynamic modulus of elasticity (DME) of mortar bars that were exposed to either of the ASR accelerating conditions were monitored for ten weeks. Based on the results obtained from this study, both geopolymer mixtures showed lower levels of expansion in comparison to the OPC mixture. However, despite the lower expansion level, a significant loss in DME was observed for fly ash-based geopolymer specimens made with siliceous aggregate and cured in a high alkali environment. Finally, curing the specimens in a high relative humidity environment did not seem to be an effective procedure in the evaluation of the ASR behavior of aggregate, as this method failed to discriminate the ASR-reactive aggregate used in this study.

Effect of moderate temperatures on compressive strength of ultra-high-performance concrete: A microstructural analysis

Concrete with two types of steel fibres and a polypropylene fibre prevented spalling and preserved the compressive strength at 300 °C, which makes these concretes suitable for long-term applications up to 300 °C, such as for steam collectors or thermal energy storage systems. The compressive strength behaviour of three types of ultra-high-performance fibre-reinforced concrete manufactured with the same matrix was investigated. For this purpose, a complete characterisation of all the raw materials and the three types of fibres used was performed. The morphology of all concrete mixtures at room temperature was analysed using scanning electron microscopy–energy-dispersive X-ray spectroscopy. From the results, it was ascertained that the steel fibres and coarse siliceous aggregates were not in contact (being separated by ≥3.41 μm) and were surrounded by the binder (of ≥1 μm in thickness) for all the mixtures studied. Rosenhahnite and/or quartz Dauphiné-twinned phases improved the compressive strength (as determined by X-ray diffraction).

A SLOT-CUTTING TECHNIQUE FOR REPAIR AND REHABILIATION OF CONCRETE DAMS AFFECTED BY ALKALI-SILICA REACTION

The combined impacts of earthquake damage and aging of concrete material on vulnerable aged dam systems have been typical causes of structural failure. The possible malfunction or loss of these vital systems and components can have serious socio-economic consequences and impacts on potable water resource availability, crop irrigation, and electric power generation. Worldwide extensive work has been done to evaluate the structural safety of aged concrete dam system components and to develop suitable remedial action and rehabilitation strategies. This paper reports a Chemo-Thermo-Mechanical Finite Element model developed by the authors which was used to demonstrate the use of the Finite Element Method (FEM) to model the behavior of a synthetic dam if the concrete is affected by Alkali-Silica Reaction (ASR), applying the slot cutting rehabilitation technique. ASR is a destructive chemical reaction between the cement paste and siliceous aggregate components in concrete materials that causes long-term expansion and degradation of concrete structures, including dams. Slot cutting is recognized as one of the promising techniques suitable to repair concrete dams suffering from ASR. The results show that the FE model could predict the stress and displacement field before and after the sawing of the slot in an assumed dam affected by ASR and demonstrate a promising capability for modeling the repair strategies in real dams suffering from ASR.

Investigation of microstructure characterization of mortars from 800 years old heritage structures in Southern part of India

The paper describes the details of the masonry mortars of 800 years old heritage sites, namely Ramappa Temple, a candidate UNESCO World Heritage (2019–2020) site, and secondly, an ancient fort both in Southern part of India. These heritage structures require maintenance repairs particularly at masonry joints for posterity. Characterization of these ancient mortars is essential to understand the quality and also for developing compatible repair mortars. The physical analysis including porosity, bulk density and specific gravity of ancient mortars were computed and it was found that the mortar samples were highly porous. Analytical techniques like XRD, SEM-EDS, XRF, TG-DTA and FTIR were conducted to study the mineralogical and chemical composition of the ancient mortars. From TG-DTA, it can be observed that the binders varied from weak to moderately hydraulic. This was further confirmed from the hydraulic index of binders in mortar samples of these heritage structures. The FTIR analysis inferred possible presence of carbohydrates. The mineralogical analysis signifies the presence of calcite and quartz minerals along with traces of vaterite and aragonite-which are the polymorphs of calcium carbonate (CaCO3) along with feldspar. The lime was of calcitic origin with siliceous aggregates.

Correlation between asphalt concrete induced healing and rheological properties of asphalt binder

The induction heating-induced healing of asphalt concrete is an innovative method of crack repairing. As concluded in previous studies, the temperature of asphalt concrete, raised through the induction heating, directly affect the process of the induced healing. As the speculation in this study, not only the temperature level but also the rheological properties of asphalt binder at the relevant temperature affects the induced healing process in asphalt concrete. In this study, the correlation between zero shear viscosity of asphalt binder and induced healing efficiency of asphalt concrete was scrutinized. The neat and modified asphalt binders with carbon black and activated carbon were utilized in the asphalt concrete comprised of limestone and siliceous aggregates. Initially, the influences of specimen dimension on the rate of induction heating were investigated. Then, the zero shear viscosity of asphalt binders, resembling the low-speed movement of melted asphalt binder, was identified based on data acquired from the rotational viscometer test. The semi-circular bending test was conducted for assessing the induced healing process of the asphalt concrete under repeated cracking-healing loading scenarios. The analysis of the induced healing index for different asphalt concrete types confirms the concurrent influences of temperature level and rheological properties of asphalt binders. Moreover, it can be deduced that the zero shear viscosity and capability of asphalt binder to move at far low-speed play a pivotal role in the accomplishment of induced healing in asphalt concrete. The proposed approach can be beneficially used to characterize the induction heating-induced healing characteristics of asphalt concrete specimens made of different ingredients.

Menshikovite Pd3Ni2As3 and Associating Minerals of Sulfide Ores at the Eastern Flank of the Oktyabrsky Deposit (Norilsk Ore Field)

Considerable amounts of menshikovite (the rare palladium–nickel arsenide Pd3Ni2As3) have been found at the eastern flank of the Oktyabrsky deposit (Norilsk ore field) near the contact of solid and impregnation sulfide Co–Ni–Cu ores within the magnetite–plagioclase–fassaite skarns. The sulfide material of the ores consists of aggregates of chalcopyrite, pentlandite, pyrrhotite, and cubanite produced by subsolidus transformations of high-temperature Iss3, Iss4 and subordinate Mss solid solutions, with ingrowth of later Se‑galena. Menshikovite associated to mertieite II, Ag-gold (756–706 fineness), Au-electrum (694–672 fineness), kotulskite, moncheite, rare altaite, hessite, naldrettite, and melonite consists of fine (30 μm or less) metasomatic ingrowths at the contact of silicate mass and aggregates of sulfides. The composition of menshikovite is close to the theoretical data: (Pd2.98Ru0.03)3.01(Ni1.89Fe0.08Co0.01)1.98 (As2.94Se0.04Bi0.02Sn0.01)3.01. Sperrylite metacrystals truncate the borders of menshikovite accretions along with other minerals of noble metals and contain their “corroded” inclusions. This association of pneumatolytic minerals of noble metals was formed under increased activity of As, Te, Sb, and Bi in fluids with low Sn activity. Menshikovite is characteristic for the Pd-richest Oktyabrsky deposit. Another palladium–nickel arsenide, that is, mayakite PdNiAs, is of quite wide occurrence in the Talnakh and Norilsk 1 deposits. The distribution of Pd and Ni arsenides is probably an element of the mineral zonality of the Norilsk ore field.

Investigating the properties of asphalt concrete containing recycled brick powder as filler

One of the major problems caused by the construction and demolition of buildings is the environmental pollution due to the disposal of the large volume of generated waste materials. In addition to the protection of environment, the recycling and reusing of the waste materials are an economical measure. In this research, the viability of using the recycled brick powder as a partial or full replacement of mineral filler in asphalt concrete has been investigated. The primary natural siliceous aggregate filler, as control filler, has been replaced in different percentages, with the secondary recycled brick powder, and the mixtures have been evaluated in terms of, Marshal Stability, flow, indirect tensile strength, moisture damage and volumetric characteristics. The results show that, the Marshal Stability increases and the flow decreases with increasing the brick powder content in the mixture. The results show that full replacement of the natural filler with brick powder results in the highest resistance against permanent deformation and indirect tensile strength. It is also shown that the mixtures containing brick powder are more resistant against moisture damage than the control mixture. The replacement of the mineral filler with the brick powder does not significantly affect the volumetric properties of the mixture.

Rheology of Alkali-Activated Mortars: Influence of Particle Size and Nature of Aggregates

The effect of two precursors (slag and fly ash), different particle size distribution, and three types of aggregate (siliceous sand, limestone, and recycled concrete) on alkali-activated material (AAM) mortar rheology were studied and compared to their effect on an ordinary Portland Cement (OPC) mortar reference. Stress growth and flow curve tests were conducted to determine plastic viscosity and static and dynamic yield stress of the AAM and OPC mortars. In both OPC and AAM mortars, a reduction of the aggregate size induces a rise of the liquid demand to preserve the plastic consistency of the mortar. In general terms, an increase of the particle size of the siliceous aggregates leads to a decrease of the measured rheological parameters. The AAM mortars require higher liquid/solid ratios than OPC mortars to attain plastic consistency. AAM mortars proved to be more sensitive than OPC mortars to changes in aggregate nature. The partial replacement of the siliceous aggregates with up to 20% of recycled concrete aggregates induced no change in mixing liquid uptake, in either AAM or OPC mortars. All the AAM and OPC mortars studied fitted to the Bingham model.

A bottom-up approach to study the moisture susceptibility of bio-modified asphalt

Causes and remedies for moisture damage at the interface of binder and siliceous stone aggregates is not fully understood and is considered as one of the most elusive and intractable pavement distresses. In recent years, increasing environmental awareness and decreasing availability of virgin materials have promoted the use of bio-materials to decrease adverse environmental impacts from petroleum-based products and support sustainable practices. Considering source dependency and composition variation in bio-materials, it is important to relate composition to fundamental materials properties in order to ensure adequate overall performance particularly in terms of resistance to moisture. Therefore, the current study uses a bottom-up approach to evaluate the performance of an asphalt binder additive from swine manure (Bio-modifier) as a means of not only improving but also understanding moisture resistance in asphalt pavement. Bio-modification was found to show improved moisture resistance at the binder level and the mixture level when compared to two other commercially available additives. Further analysis of the binder doped with representative molecules of the additives showed varying differences in adhesion and moisture susceptibility. To provide in-depth understanding of the underlying interaction mechanisms between water and binder, molecular dynamic simulations were performed on a blend of asphaltene and dopant molecules placed on a silica oxide substrate and exposed to water molecules. Study results revealed the passivation mechanism of bio-modifiers as a dominant factor contributing to enhanced resistance to moisture damage. It was found that bio-modifiers molecules occupy active sites of silica oxide preventing nucleation and growth of acidic compounds at the binder-silica interface. Such acidic compounds are water soluble and their presence at the interface can be detrimental leading to moisture damage. Study results showed anchored bio-modifiers molecules further interact with asphaltene molecules to provide bridging mechanism between binder and silica. This in turn leads to enhanced resistance to moisture damage in bio-modified binders adhered to siliceous surfaces such as quartz and granite stone aggregates.

Diagnosis of Pathological Manifestations and Characterization of the Mortar Coating from the Facades of Historical Buildings in Porto Alegre — Brazil: A Case Study of Château and Observatório Astronômico

ABSTRACT This article presents the diagnosis of pathological manifestations on the mortar coating from the facades of two historical buildings of scientific and social importance in Porto Alegre, Brazil. Documental investigation, visual survey, percussion and thermography tests, mapping of damages, and characterization of the coatings were performed. Coatings were characterized by determining the binder:aggregate proportion and the aggregate particle size distribution; X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and qualitative test of soluble salts were performed. The damage maps present the extension of anomalies, like detachments and areas with moisture, which were located with support of thermography results. Mortar samples extracted from the buildings indicated binder:aggregate proportions, in dry mass, ranging from 1:1 to 1:2.7. In the binder, it was verified mainly the existence of calcite and quartz through XRD; with XRF, magnesium oxide was additionally verified and calcite was also found with TGA. Chlorides and sulfates were identified by XRF and test of soluble salts. The fineness module and the particle size distribution of siliceous aggregates from different samples were similar.

Composition and Size Dependent Sorting in Preplanetary Growth: Seeding the Formation of Mercury-like Planets

Abstract In an earlier work, we found that large metallic iron fractions in dust aggregates and strong magnetic fields boost preplanetary growth. This sets an initial bias for the formation of Mercury-like planets in the inner part of protoplanetary disks. We extended these experiments here by adding pure quartz aggregates to the iron-rich aggregates. Magnetic boost still leads to the formation of larger clusters of aggregates. These clusters now include silicate aggregates, which can also be connecting bridges between chains. However, at least a certain fraction of iron-rich aggregates are needed to trigger magnetic boost. Without a magnetic field, the sticking properties of the aggregates and their constituents determine the composition of clusters of a given size. This introduces a new fractionation and sorting mechanism by cluster formation at the bouncing barrier.

Liquid-glass concrete of variable density

Research results of porous compositions based on sodium liquid glass and fillers of various origins are presented. Materials, regulating rheological properties and thermal transformations of liquid glass compositions were used as the fillers. Feasibility of multicomponent fillers introduction into thermal expansion compositions was substantiated. Combined fillers matching a gel-forming component and thermosetting materials that emit a gas phase are preferred for improving molding properties of compositions and forming a highly porous polymodal material. A porous aggregate with a density of 250 – 300 kg/m3 was synthesized, providing high thermal resistance of the building envelope. Advantages of a liquid-glass matrix for producing lightweight concrete with a porous silicate aggregate are shown. Genetic commonality of an aggregate and a matrix contributes to the formation of durable concrete of a porous structure. Variants of the structure of variastropic liquid glass concrete, consisting of layers of various densities were proposed. Lightweight concrete of variatropic structure with a density of 800 kg/m3 and compressive strength of 10 MPa has been developed. The integrated use of liquid glass to obtain aggregate and concrete will ensure a compact technological scheme. The research is aimed at creating a technology of heat-insulating materials that combine high porosity with shape stability.

Friction and Texture Retention of Concrete Pavements

In the late 1980s and early 1990s, the Alabama Department of Transportation (ALDOT), U.S., noticed a decline in skid trailer numbers on concrete pavements shortly after grinding operations. The engineers at the time suspected that the coarse aggregate caused the decline in these numbers and the resulting conclusion led to a ban of carbonate aggregates in mainline concrete pavement in Alabama that is still in place. This detailed laboratory study re-examines the fundamental friction issues that led to this policy. A total of 48 aggregate, grinding, and grooving combinations were tested as part of this study. Three aggregate sources were examined: a siliceous source, a “hard” limestone source, and a “soft” limestone source. Two blade spacings were examined for grinding operations: 52 blades/ft and 60 blades/ft. Some ground specimens were also grooved. Finally, a set of specimens had the Next Generation Concrete Surface (NGCS) applied to them. The specimens were polished with the National Center for Asphalt Technology (NCAT) three-wheel polishing device (TWPD). The dynamic friction tester was used to evaluate friction values at various points through the polishing process. After the polishing, the macrotexture was characterized using the circular track meter. Across the board, the highest performing texture was that with no grooves and 52 blades/ft. Very generally, the loss of friction decreased with increasing siliceous content. However, some of the trends were extremely minor and, in a few cases, siliceous aggregates caused higher friction loss. There were numerous instances when blended carbonate/siliceous concrete pavement surfaces performed better than sole siliceous concrete pavement surfaces.