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SEM examination was used during the concrete alkali active long-term aging tests to understand qualitatively the alkali activity reaction degree and to predict the deterioration trend of the concrete. The Alkali-silica Reaction (ASR) is one of the most important factors affecting the durability of concrete [1].
The alkali−silica reaction (ASR) is a chemical reaction that occurs between hydroxyl ions in the pore solution of a hydrated cement paste and in certain reactive silica phases in the aggregates used in …
Alkali − Silica Activity and Inhibition Measures of Concrete Aggregate in Northwest China Jing Wen 1,2, Jinmei Dong 1,2, *, Chenggong Chang 1,2, Xueying Xiao 1,2 and Weixin Zheng 1, 2, *
During the last several decades, Alkali-activated Materials (AAMs) is a Portland cement-free form, have been intensively researched as a potential alternative for ordinary Portland cement concrete (OPCC), with the objective of lowering CO2 emissions while repurposing a large volume of industrial waste by-products.
Slag (SiO 2 +CaO>70%) is the most commonly used calcium-rich precursor for forming the high calcium alkaline cement, and the main reaction product is an aluminum-substituted calcium silicate hydrate (C-A-S-H gel) which is similar to the product generated during Portland cement hydration (C-S-H), but its Ca/Si ratio is lower than …
A further concern with using gravel containing a number of different rock types as aggregate in concrete is the possibility of Alkali-Silica Reaction (ASR), which could lead to cracking and ...
Concrete Testing Equipment; Material Test Machine; Traffic safety and Pavement Testing Equipment; Mold; NDT Equipment; Soil Testing Equipment; Other instruments; Solutions; Video; Service & Support; News; Contact; Get a Quote Rapid Alkali Activity Tester for Sand and Gravel.
The test procedure involves using high-alkali cement, meeting an alkali content of 0.90 % ± 0.10 % and adding sodium hydroxide to the mix water to raise the cement alkalis to 1.25 %. Concrete prism (from such mix) measuring 75 mm x 75 mm x 285 mm (3-in x 3-in x 11.25-in ) is cured in water for one full year at 38 °C (100 °F).
High-Calcium Alkali-activated Materials include Calcium and Aluminum-rich materials (({SiO}_{2}+CaO) > 70%), resulting in a hydration gel with (Al) in it's structure, in the form of C-A-S-H, analogous to hydration products in Portland Cement (Pacheco-Torgal et Al., 2015).The most common high calcium binder for alkali activation is slag, a …
The use of concrete is associated with immense negative environmental impacts. The current annual production of>4 billion tonnes of ordinary Portland cement (OPC) is responsible for 7% of the global CO 2 emissions [3]. Concrete has an environmental impact of 300 kg eq CO 2 /m 3 on average, of which 90% is attributable …
1. Introduction. Alkali–silica reaction (ASR) is one of the most frequent causes of concrete deterioration [1,2].ASR is a slowly expansive reaction between certain forms of alkali-reactive silica (opaline silica, flint, cryptocrystalline quartz) and/or certain silicate minerals present in concrete aggregates and the hydroxyl ions in concrete pore …
1. Introduction. One of the keynote papers dedicated to the 13th International Congress on the Chemistry of Cement held in Madrid in 2011 focused on the chemistry of alkali-activated binder systems [1].The aim of the current paper is not to provide a detailed overview of all aspects of the history, chemistry and engineering of alkali-activated …
Wadi gravel was classified as potentially reactive in the RILEM AAR-4.1 accelerated concrete prism test, but of 'low reactivity' in the BS 812-123 test over the longer period of 12 months. Overcoming the potential problems of gypsum content and AAR successfully provides a valuable local resource of Wadi gravel aggregate for concrete.
The ordinary Portland cement (P.O 42.5) with a specific surface area of 345 m 2 /kg and a density of 3.15 g/cm 3 was used, which was provided by Shijiazhuang Quzhai cement co. LTD. Slag and fly ash were produced in Lingshou, Shijiazhuang. The slag with a specific surface area 455 m 2 /kg and a density of 2.82 g/cm 3 was classified as S105 …
Alkali Silica Activity and Inhibition Measures of Concrete Aggregate in Northwest China Jing Wen 1,2, Jinmei Dong 1,2, *, Chenggong Chang 1,2, Xueying Xiao 1,2 and Weixin Zheng 1,2, *
occurs when the water soluble alkali content of the cement was abQut 0.6% Na20 equivalent which corresponds to an acid soluble alkali CQntent of about 0.8%. By contrast, with slowly expanding aggregates such as greywackes and hornfels expansion increases with the alkali content of the cement, at least up to an acid soluble alkali …
Conventional porous concrete is fabricated with gravel and cement, showing low P removal efficiency due to low porosity, inferior surface area, and low active components of gravel. Accordingly, a novel porous concrete (C-A) is synthesized by replacing gravel with alkali-activated aggregate (compressive strength of 90.12 MPa …
Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its …
What is Alkali-silica reactivity? Alkali-silica reactivity (ASR) remains a major durability issue affecting concrete structures, including heavy civil infrastructure, such as dams, bridges, pavements, and nuclear power plants — despite over 70 years of investigations. (See references [1]–[4] below.) How does ASR impact concrete?
e been developed for assessing the potential alkali-reactivity of aggregates. These …
reaction leads to delayed concrete expansion and destruc-tion. Also micro-crystalline or imperfectly crystallised quartz (stressed quartz) may be the reason for alkali reac-tivity in similar slow alkali-reactive aggregates [8]. In recent years, many researchers have noted an in-crease of new types of rocks which are alkali-reactive in concrete.
The now well-known alkali-activated cement (AAC), which has a lower carbon footprint, and excellent durability in some applications, ... The alkali activities of the ES and EP were evaluated using the ASTM C1260 standard (Standard Test Method for Potential Alkali Reactivity of Aggregates). The accelerated mortar bar test assessed by the length ...
2. Background. AAMs are synthesized by the reaction of an aluminosilicate-based precursor (xSiO 2 ∙ yAl 2 O 3), alkali activators (MOH and M 2 SiO 3; where M is either alkali ion Na + or K +) and water (H 2 O). No Portland cement is required to produce alkali-activated binders, but AAMs could also be added as a supplementary …
THE 9TH INTERNATIONAL CONFERENCE ON ALKALI-AGGREGATE REACTION IN CONCRETE Hl92 alkali-silicareactivity, but are equally relevant to the detection of alkali-reactivecarbonate rocks. The underlying strategy and principals ... (ii) A sand or gravel deposit with a potentially reactive constituent such as chert (2) A constituent within only …
a Concrete pore solution is dominated by Na, K, and OH (with minor amounts of Ca). If the silica in the aggregate is reactive — the OH and then the Na and K will react with the SiO 2.. b The product of the reaction is in alkali-silica gel composed of Na, K, Ca, and Si The gel forms around and within the aggregate.c The gel imbibes …
In addition, the alkali content from cement pose a stronger effect on the AAR expansion of RCA. By studying the AAR of recycled concrete incorporating 30% replacement of RCA when using low and high alkali cement respectively. The RCA concrete using high alkali cement expanded more than twice that of using low alkali …
By using of accelerated mortar bar test (AMBT), concrete prism method (CPM), and rock column method (RCM), it confirms that aggregates of W1# are the aggregates with potential alkali-silica activity. It is advisable to use a variety of methods to evaluate whether the aggregates have the potential activity.
The huge demand for sand and gravel resources in road engineering construction leads to excessive consumption of resources and environmental damage. Recycling waste concrete and industrial solid waste as a road material is a promising alternative. In order to explore the application of these solid wastes in the road base, this …
For this method the aggregate reactivity is related to the expansion …
occurs when the water soluble alkali content of the cement was abQut …
This test method is generally considered the most reliable for evaluating aggregate …
The concrete industry is a major carbon emitter and polluter, with severe human health impacts. ... sand, gravel and stone aggregate). Manufacturing Portland Cement, the most common form used ...
Alkali activity and main parameters of aggregate. The slates and rhyolite …
Quality Counts. Make sure that your concrete producer purchases good-quality aggregate as verified by regular aggregate test results in compliance with ASTM C 33, "Standard Specifications for Concrete Aggregates." A history of good performance of a local aggregate also provides an indication of how well the material performs in service.
of alkali-activated cementitious materials [4], but there is limited research on the double damage of chloride ion corrosion and freeze-thaw damage of alkali-activated coal gangue cementitious materials. Calcined coal gangue has better activity when it reaches 700 C [5,6], and then the alkali-activated coal gangue-slag can be employed as a cement.
Research on alkali-activated cement has investigated the possibility of using recycled concrete for alkali activation (Borrachero, 2022; Viswanath, 2021), crack development (Matalkah, 2019), and ...