“…The results indicated that the heat of hydration of the cement reference sample after 7 days is 303.9 J/g and the depletion in the flow of cumulative heat of the blended study samples (TF1, TF2, TF3, TF4, TF5, TF6, and TF7) is greater than the reference sample and it occurs between 269.9 and 289.6 J/g, where the lack between the cement reference sample and the lowest one is 35 J/g while the difference between the studied samples' values during seven days is negligible. Subsequently, there is a positive impact on decreasing the accumulation of heat flow in the structure of concrete mass when replacing part of the cement with the studied tuffs samples 40 . Figure 7 The graphic pattern of the effect of various tuffs on heat of hydration of mortar samples.…”
Rhyolite rocks extend from southern Egypt to northern Egypt in the Eastern Desert, and no effective economic exploitation of them has been discovered so far. The pozzolanic activities of different volcanic tuffs (VT) supplied from the Eastern Desert located in Egypt have been investigated as natural volcanic pozzolan materials to develop new green cementitious materials for achieving sustainability goals in the construction field. Experimentally in this paper, the pozzolanic activities of seven diverse specimens of Egyptian tuffs taken with standardized proportions of 75:25% (Cement: volcanic tuffs) were investigated. Pozzolanic features of such tuffs are examined comparatively via strength activity index (SAI), TGA, DTA, and the Frattini’s test. Chemical composition, petrographic, and XRD analysis were also performed for tuffs samples. The pozzolanic reaction degrees were determined according to the compressive strengths at 7, 28, 60 and 90 days with different replacement ratios (20, 25, 30 and 40%) of tuffs samples. Additionally, the micro-filler effects in mortar and concrete were determined by measuring the heat of hydration in mortar samples and the compressive strength of concrete with different additive ratios for tuffs samples besides, the concrete slump test. The results show that TF6 gives a lower cement heat of hydration value which is less than 270 J/g at 7 days. Also, its performance in concrete is better than silica fume at late strength (28 days) since the concrete index value is 106.2% by compared to the concrete index of silica fume 103.9 and therefore it can be used as an alternative to high price and quality variable silica fume (SF) for producing high-performance green concrete. Due to the good pozzolanic behavior proved by nearly most volcanic tuffs, along with their low cost, this study will be profitable for very auspicious the use of Egyptian volcanic tuffs for developing sustainable and eco‑friendly blended cement.
“…The results indicated that the heat of hydration of the cement reference sample after 7 days is 303.9 J/g and the depletion in the flow of cumulative heat of the blended study samples (TF1, TF2, TF3, TF4, TF5, TF6, and TF7) is greater than the reference sample and it occurs between 269.9 and 289.6 J/g, where the lack between the cement reference sample and the lowest one is 35 J/g while the difference between the studied samples' values during seven days is negligible. Subsequently, there is a positive impact on decreasing the accumulation of heat flow in the structure of concrete mass when replacing part of the cement with the studied tuffs samples 40 . Figure 7 The graphic pattern of the effect of various tuffs on heat of hydration of mortar samples.…”
Rhyolite rocks extend from southern Egypt to northern Egypt in the Eastern Desert, and no effective economic exploitation of them has been discovered so far. The pozzolanic activities of different volcanic tuffs (VT) supplied from the Eastern Desert located in Egypt have been investigated as natural volcanic pozzolan materials to develop new green cementitious materials for achieving sustainability goals in the construction field. Experimentally in this paper, the pozzolanic activities of seven diverse specimens of Egyptian tuffs taken with standardized proportions of 75:25% (Cement: volcanic tuffs) were investigated. Pozzolanic features of such tuffs are examined comparatively via strength activity index (SAI), TGA, DTA, and the Frattini’s test. Chemical composition, petrographic, and XRD analysis were also performed for tuffs samples. The pozzolanic reaction degrees were determined according to the compressive strengths at 7, 28, 60 and 90 days with different replacement ratios (20, 25, 30 and 40%) of tuffs samples. Additionally, the micro-filler effects in mortar and concrete were determined by measuring the heat of hydration in mortar samples and the compressive strength of concrete with different additive ratios for tuffs samples besides, the concrete slump test. The results show that TF6 gives a lower cement heat of hydration value which is less than 270 J/g at 7 days. Also, its performance in concrete is better than silica fume at late strength (28 days) since the concrete index value is 106.2% by compared to the concrete index of silica fume 103.9 and therefore it can be used as an alternative to high price and quality variable silica fume (SF) for producing high-performance green concrete. Due to the good pozzolanic behavior proved by nearly most volcanic tuffs, along with their low cost, this study will be profitable for very auspicious the use of Egyptian volcanic tuffs for developing sustainable and eco‑friendly blended cement.
“…The Ca + released during C 3 S hydration can be adsorbed on the surface, weakening the oriented growth of the Ca(OH) 2 in the weak interface transition zone, providing nucleation points for hydration products, promoting the precipitation of the cement hydration products, and accelerating the formation of the C-S-H gel [26,27]. The FT can fill the interstice in the composite cementitious system, reduce the porosity in the system, improve the density, and thus increase the strength of the cement mortar [28,29]. In addition, the finer the tuff powder particles, the lower the SiO 2 content in the 28d hydration products; this is because the finer the tuff powder particles, the faster the ion precipitation, the faster the secondary hydration reaction rate, so that more SiO 2 can be consumed [4].…”
Section: The Hydration Mechanism Of Tuff Powdermentioning
Abundant tuff mineral resources offer a promising solution to the shortage of fly ash (FA) and silica fume (SF) resources as emerging supplementary cementitious materials. However, a lack of clarity on its hydration mechanism has hindered its practical engineering application. In this study, high SiO2-content tuff powder (TP) was examined to assess the mechanical and workability performance of mortar specimens with varying particle sizes of the TP as complete replacements for FA or SF. Microscopic analysis techniques, including X-ray diffraction (XRD), differential thermal analysis (DTG), and energy-dispersive X-ray spectroscopy (EDS), were employed to elucidate the hydration mechanism of the TP and its feasibility as a substitute for SF or FA. Results indicated that TP primarily functions as nuclei and filler, promoting cement hydration, with smaller particle sizes amplifying the hydration ability and increasing Ca(OH)2 and C-S-H gel content. The specimens with TP (median particle size 7.58 μm) demonstrated 9.2% and 29.9% higher flexural and compressive strengths at 28 days, respectively, compared to the FA specimens of equal mass. However, fluidity decreased by 23.1% accordingly. Due to TP’s smaller specific surface area compared to SF, the TP specimens exhibited higher fluidity but with decreased strength relative to the SF specimens. Overall, TP shows potential as a replacement for FA with additional measures to ensure workability.
“…Yu [18] found that NaOH and sodium silicate with applicable concentrations could activate tuff powder; the porosity was improved and the mechanical properties were significantly enhanced after 28 days of curing under high temperature conditions. In addition, some studies have shown that using tuff powder to replace some cement can reduce the hydration rate and total heat release in the early stage, but it has a slight adverse effect on the mechanical properties and durability in the later stage [16], and with the increase of its content, the porosity also increases [19]. Abali [20] also pointed out that the use of tuff powder can reduce the fluidity of the mixture and increase the setting time.…”
There are some limitations in the application of tuff powder as a supplementary cementitious material (SCM). Exploring its feasibility in new fields will consume a large amount of silica-alumina mine solid wastes. This study has investigated the mechanical properties and mechanism in contact-hardening of tuff powder with a method of compression molding. The compressive strength of specimens was tested, and the X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and Mercury intrusion porosimetry (MIP) methods were used to reveal the mechanism of contact-hardening of tuff powder from a micro-perspective. The results indicated that the compressive strength of specimens was higher when activated by sodium hydroxide compared to calcium hydroxide. Compared to calcium hydroxide, the compressive strength of TFS20 and TFF20 activated by sodium hydroxide was improved by 20% and 23%, respectively. The hydration degree of tuff powder was very low, with a water–cement ratio (w/c) of 0.15, while the hydration degree of coal gangue powder was higher. The results of TGA and SEM indicated that the sodium hydroxide had a better activating effect on slag and fly ash. Therefore, more C-S-H gels were generated in those samples activated by sodium hydroxide. Furthermore, the structure of samples was more compacted, and there was a reduction of porosity by 10% and 11% for TFS20 and TFF20, respectively, especially the proportion of harmful pores.
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