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Heat flow curves of specimens with different binder constitutes in the absence of anhydrite (A) and with sufficient anhydrite (B) measured with a water to solid ratio of 1.0.
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Context 1
... hydration heat liberation rate curves within 70 h are illustrated in Fig. 5. For the binary mixtures without anhydrite (Fig. 5A), the hydration starts immediately after water is added into the binder, generating a heat release until 36 min. After a dormant period of about 2 h, the main thermopositive peak corresponding to the formation of AFt can be observed. Moreover, it could be also noticed that the ...
Context 2
... hydration heat liberation rate curves within 70 h are illustrated in Fig. 5. For the binary mixtures without anhydrite (Fig. 5A), the hydration starts immediately after water is added into the binder, generating a heat release until 36 min. After a dormant period of about 2 h, the main thermopositive peak corresponding to the formation of AFt can be observed. Moreover, it could be also noticed that the replacement of CSA cement clinker by coral filler has ...
Context 3
... smaller. Beyond 30 h, no additional peak is visible in the differential calorimetric curve. Additionally, in the mixtures with sufficient anhydrite, similar thermopositive peaks corresponding to the formation of AFt can be observed. the replacement of CSA cement clinker by coral filler and quartz filler can slightly promote the hydration kinetics (Fig. 5B), which may be attributed to the dominance of the high amount of anhydrite in the hydration process. Fig. 6 illustrates the total heat release amount of all the mixtures. As can be seen, the hydration heats of mixtures with fillers are lower than that of CSA cement clinker. Coral and quartz filler decrease the hydration heat of cement, ...
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... Recently, using coral wastes material instead of coarse and fine aggregate and even Portland-cement has considered, especially in marine environments and islands which can reduce CO 2 emission of shipping raw materials, construction cost, and delay [31,189]. Using coral wastes because of loose structure has detrimental effects on the mechanical strength and permeability of concrete [31,[190][191][192][193][194]. If its powder replaces Portland-cement, besides strength and durability issues, chloride binding decreases because of C 3 A dilution and competition of carbonate and chloride ions to form AFm phase [195,196]. ...
As an available and high-quality supplementary cementing materials (SCMs), Consumption of Metakaolin (MK) was proposed by many research to replace Portland cement to improve concrete quality and reduce the negative effects of cement industry on the environment. With that being said, it is necessary to summarize the recent finding and gaps on the effect of replacing Portland-cement by MK in different replacement levels on various fresh and hardened properties of concrete. This review paper presents an overview of recent investigations on MK effect on fresh properties, mechanical strength, and corrosion resistance of concrete and mortars. Besides, the synergic effect of MK and other SCMs, its optimum replacement level for different purposes, and application of in different types of concretes are discussed as well. The literature indicates that using MK, up to a certain replacement level, improves the pore structure of concrete; consequently, increases its durability against chloride-induced corrosion. Because of the high aluminum (Al) composition of MK, using MK increases chloride binding as well. In the case of carbonation, using MK was reported to increase the carbonation depth mostly under high CO2 concentrations. Nevertheless, under the conventional concentration of CO2, MK containing specimens show acceptable performance against carbonation, especially combined to the limestone. From another perspective, MK can play a major role to reduce the direct and indirect CO2 emission of cement industry, and using it seems an inevitable step toward more sustainable cement industry and concrete construction.
... The critical temperature for ettringite (C 6 AsH 32 , Et), AFm phases (C 4 AXH n ), calcium hydroxide (CH), gibbsite (Gb) were identified according to Refs. [15,[23][24][25][26]. The content of CH referring to the hydrated blend can be directly calculated from the weight loss between 410 and 500 � C [25,27,28]. ...
In order to prolong the service life of reinforced concrete structures either serving in chloride-rich environment or prepared with chloride contaminated ingredients, the chloride binding behaviors of cementitious materials with alumina compound addition are investigated in this work. The chloride binding capacity, phase conversion and solution chemistry of mixtures during chloride exposure were discussed. The applied alumina compounds are γ-Al 2 O 3 , γ-Al(OH) 3 and colloidal nano-alumina, and metakaolin is used as a reference additive. The results show that alumina compounds exhibit obviously higher potential of forming AFm-type phases than metakaolin and therefore significantly improve the chloride binding capacity. During chloride exposure, the charge-balancing anions like hydroxyls, carbonates and sulfates can be replaced by chlorides to form Friedel'salt and increases the pH of exposure solution. The released sulfates reacting with SO 4-AFm lead to delayed ettringite formation, binding large amount of mixing water and reducing calcium hydroxide content. Besides, the transformation of carboaluminate to Friedel'salt also accounts for partial reduction of calcium hydroxide in hydrated blended after chloride exposure, due to the released carbonates precipitating with calcium ions in the system.
... But CSC exhibits higher dying shrinkage and capillary water absorption [2]. Also, the use of coral filler in replacing cement clinker in Calcium sulpho-aluminate cements has been studied and reported that the replacement could provide similar compressive strength and better flexural strength [3]. The performance of the coral stone as a masonry material is not yet reported with respect to durability. ...
Fire is a serious natural disaster that can ruin not only the functionality but also the heritage value of ancient monuments. This paper addresses the direct examination of the extent of microcrack formation and mineralogical changes to evaluate the degree of fire damage in a granite structure. The study described in the paper is conducted on a masonric heritage temple from South India which was recently affected by fire. Advanced microstructure characterization techniques like X-ray diffraction, Secondary Electron Microscopy and Mercury Intrusion Porosimetry are used to assess the disintegration. The evidence from the microanalytical investigations was able to help determine the possible temperatures of exposure of the granite, as well as the extent of deterioration of the granite, which was critical in deciding upon the need for restoration or replacement of the granite structural elements. This is important from the aspects of both economy and preserving cultural value.
