Papers by Keyword: Expansion

Abstract: Without a cure but preventable, Alkali-Silica Reaction (ASR), dubbed the “Concrete Cancer,” happens when alkali in cement bonds with silica in aggregates to form an expansive gel. This research aims to investigate expansion and influence mitigation of ASR in concrete by identifying potentially reactive aggregates causing its onset and using binary blended cement to slow down unwanted gel expansions through the mitigative ability found in its fly ash component. This research also observed variations in expansive behavior and the physical changes that arose after the experiments. Aggregate samples were collected from different quarries in Davao, Philippines, denoted as Deposit A, Deposit B, Deposit C, and Deposit D. These deposits were tested according to the ASTM C1260: Accelerated Mortar Bar Tests (AMBT) to identify a reactive group. Three aggregate groups, Deposit A, Deposit B, and Deposit C, were tagged as reactive due to exhibiting more than a 0.1% increase in lengths, indicating unideal expansion. Additional sets of AMBTs were done for the identified aggregates using blended cement as a binder to test the combinations' ability to minimize expansion. This resulted in an average expansion decrease per set of approximately 78%, 82%, and 85% for A, B, and C, respectively, further strengthening the reputation of fly ash as an effective mitigating SCM against ASR.

Abstract: This research aims to evaluate the properties of basic oxygen furnace slag (BOFS) as aggregates used in Superior Performing Asphalt Pavements (Superpave) mix design. A total of five different aggregates, including one limestone and four BOFS aggregates with different ages, were evaluated by the following aggregate properties: specific gravity, water absorption, Los Angles abrasion, aggregate crushing value, angularity, flakiness, soundness (sulfate chemical and freeze-thaw resistance), and expansion characteristics. Then, the volume stability of the hot mix asphalt (HMA) mixture was also discussed based on the aging effect of BOFS aggregate. Test results indicated that aged BOFS aggregate performs better than unaged BOFS aggregate: Aged BOFS aggregate has lower water absorption, lower aggregate crushing value, higher abrasion resistance, and less expansion. The flakiness and angularity of BOFS aggregates were satisfied with Superpave criteria. However, if free-lime (f-CaO) and free magnesium (f-MgO) in BOFS aggregate exist, it may cause the volume stability of asphalt mixtures with BOFS aggregate. In conclusion, if BOFS is appropriately aged and weathered, BOFS can be an alternative to conventional aggregate.

Abstract: During the steelmaking process, many by-products, such as blast-furnace slag (BFS), basic oxygen furnace slag (BOFS), and ladle slag (LS), are generated. Unlike BFS, utilizing BOFS is limited due to its expansive volumetric characteristics by the transformation process of free lime (f-CaO) and free magnesia (f-MgO) to portlandite (Ca(OH)₂) and brucite (Mg(OH)₂). The natural aging process may help BOFS used as an aggregate in mortar or concrete because harmful elements such as f-CaO and f-MgO could be consumed during this stage. This study evaluated compressive strength and expansion characteristics of mortar mixtures incorporating chronologically aged-BOFS aggregates blended with ground granulated blast furnace slag (GGBFS) and ASTM class F fly ash (FFA). Test results revealed that the longer aged BOFS aggregate, the lower compressive strength, regardless of mixture types. The aging process of BOFS aggregate reduced the expansion of mortar mixtures. Incorporating GGBFS or FFA into mortar mixtures containing BOFS aggregate even more reduced the expansion of the mixture.

Abstract: This study investigates the effect of the metal matrix composition of the friction material on the pre-sintering process through a simulation experiment on the Sprinkle sintering process. No segregation in the pre-sintered microstructure of the free-deposited friction material powder and no cracks are observed at the interface with the steel plate. In the case of a brass composition containing Zn and trace elements having relatively high vapor pressure, expansion occurs due to the volatilization of the composition elements during pre-sintering. On the contrary, in the case of bronze-based powder, the effect is insignificant. Therefore, when the friction material is manufactured using the sprinkle sintering method, the matrix composition must be selected in consideration of the volatilization effect of the metal matrix element.

Abstract: The paper discloses results of durability studies of alkali activated concretes based on different alkali sources using aggregates capable to alkali-silica reaction (ASR). Active aggregates are representing by perlite, andesite, basalt and sandstone. It is shown that the alkali-reactive aggregates, in degree of their influence on expansion deformations occurring in the slag alkaline concretes may be placed in the following row: perlite< sand< sandstone< basalt< andesite, and a growth of expansion deformations is observed with increase in the active silica content in the aggregate. Also it is set that alkaline components, in degree of their influence on the rate of expansion deformations development in the slag alkaline concretes made with reactive aggregates, may be placed in the following sequence: Na₂CO₃<Na₂O SiO₂ < NaOH< Na₂O 2SiO₂.

Abstract: Delayed Ettringite Formation (DEF) is an internal sulfate attack caused by heat-induced decomposition and/or prevention of normal ettringite formed during the initial hydration of cement at elevated temperature (above about 70°C) and its re-crystallization in the hardened matrix. This reaction is a physico-chemical phenomenon inducing an expansion of the cement paste that could lead to cracking of cementitious matrix. These cracks result in a decrease in the mechanical performances and durability parameters of the material. However, the internal sulfate attack is characterized by a very slow reaction kinetics and therefore it is difficult to study it in laboratories. This research developed an accelerated method focused on mortar specimens; it is based on electrochemical techniques in order to speed the leaching of alkalis that could be accelerated the DEF.

Abstract: One of the heat-resistant solutions effective application areas is to protect the structures from the high temperatures’ effects in case of fire. Material damage from fires amounts to hundreds millions of rubles. An effective way to improve the fire resistance of the building structures is to apply heat-insulating coatings to the surface. One of the compositions to protect the structures from high temperatures is a heat-resistant solution based on the expanded clay sand and perlite. The effectiveness of the solutions application to protect against high temperatures exposure increases due to the fact that these solutions perform both thermal and decorative functions. In the field of conventional building structures protection from the high temperatures effects, the extensive studies have been carried out by such scientists such as [6,7,8,9,32,10], and the solutions that simultaneously perform the decorative functions and the functions of protection against the effects of high temperatures in the event of fire have been little studied except for the usual restoration solutions. The study of the solutions’ special properties for the protection of small architectural structures such as fire resistance, thermal conductivity and linear thermal expansion coefficient is a rather important task.

Abstract: The aim of the research was verification of influence of aeration and influence of aluminum powder on microstructure and physical mechanical properties of calcium silicate composite material. At the same time, influence of various dosages of alternative raw materials on porous structure of the composite was examined. Tested raw materials are not the ones commonly used in the technology of manufacture of calcium silicate composites, for example chamotte blocks, Lining of silica and foundry sand. It was found that influence of aeration of calcium silicate composite causes reduction of compressive strength by roughly 85%. At the same time, volume weight drops by 50%. As a consequence of the expansion, intensity of diffraction lines of tobermorite detected by X-ray diffraction analysis is reduced because of reaction of aluminum powder with calcium hydroxide. It was found that there is dependency between the amount of replacement of silica sand with foundry sand and silica, and intensity of tobermorite diffraction lines, where the intensity of the diffraction lines was reduced with increased amount of replacement.

Abstract: This paper demonstrates the development of a technology for low-waste zero-draft hot forging of axisymmetric parts, in particular, welding neck flanges, on the basis of an expansion-extrusion deforming procedure. In this study, we carried out a process simulation by means of DEFORM 3D for a qualitative evaluation of the plastic yield. Based on the simulation results, the method was proven feasible, and we set forth the goal to prepare the process and design guidelines for further industrial application. The region of plastic deformation was determined, and a general view of the function for determining kinematic parameters was given according to A.L. Vorontsov’s procedure. The force parameters of the zero-draft hot forging process by the combined expansion-extrusion procedure were analyzed by studying the kinematic conditions of the forging. The general function for determining the force parameters was found.

Abstract: Building structures have been designed such that they are able to withstand the adverse effects of the environment for a certain time. The terms "for a certain time" and "the surrounding environment" are used for a purpose here, and that is because the phenomenon of ageing buildings is currently an increasingly discussed problem that is faced by every larger city. The materials used in the buildings, such as façade cladding, age just as the buildings themselves do. An immense pressure has been currently put on designers to use environmentally friendly materials not only for new buildings but also for the retrofitting of existing ones. The aim of this paper is to demonstrate that wood or wood composite materials are convenient solution for restoration of façades of administrative or commercial buildings, however, since the new cladding have to be connected with an old load-bearing structure, the designers have to overcome many limitations. One of the main difficulties is high thermal and moisture expansion of these materials which has a direct impact on the appearance of the façade. The obtained results showed that expansion properties should be studied closely when using wooden elements in the design and that a neglection can lead to a premature failure of the system.