The Phase Transformation of Recycling Concrete in Recalcination

2013 ◽  
Vol 743-744 ◽  
pp. 175-179 ◽  
Author(s):  
Zhi Gang Zhang ◽  
Zong Hui Zhou ◽  
De Cheng Zhang ◽  
Xin Cheng
Keyword(s):  
Phase Transformation ◽  
Calcium Hydroxide ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Eutectic Temperature ◽  
Experimental Results ◽  
Industrial Wastes ◽  
Cement Clinker ◽  
Temperature Range ◽  
Natural Aggregates

In this paper, the artificial aggregates were prepared by limestone and industrial wastes in accordance with the ratio of cement raw meal, to obtain the recycling concrete replacing natural aggregates. Cement clinker could be regenerated by these recycling concrete and the aim of recycling could be realized. After these concrete was cured for 90 days, then was crushed and grinded, the phase transformation of recycling concrete in recalcination would been studied by XRD and so on. The experimental results showed that the composition of the recycling concrete met the demand of clinker modulus and C2S, C3S, C4AF, C3A were well crystallized at 1400 °C. So these recycling concrete could be directly calcined. The calcium hydroxide dehydrated around the temperature of 500°C. The calcium silicate hydrate was dehydrated gradually between the temperature of 400°C and 1000°C. At the same time, C2S crystallized during the temperature range. C4AF and C3A stared to crystallize around the temperature of 1000°C. Due to the composition of these concrete was complex, the lowest eutectic temperature dropped. C3S started to crystallize around the temperature of 1250°C and the best crystallization was achieved at the temperature of 1400°C.

Study of Mass Changes of Cement Pastes as a Function of Age Using Thermogravimetry

2015 ◽  
Vol 824 ◽  
pp. 43-47
Author(s):  
Lenka Scheinherrová ◽  
Anton Trník ◽  
Tereza Kulovaná ◽  
Robert Černý
Keyword(s):  
Czech Republic ◽  
Portland Cement ◽  
Heating Rate ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Argon Atmosphere ◽  
Mass Change ◽  
Cement Pastes ◽  
The Czech Republic ◽  
Temperature Range

We study the hydration and pozzolanic reactions of cement pastes made from Portland cement (CEM I 32.5 R) from the Czech Republic as a function of age, using thermogravimetry. The measurements are done for 2, 7, 28, 90, and 180 days cured samples in order to monitor the rate of hydration. The investigation is performed in the temperature range from 25 °C to 1000 °C with a heating rate 5 °C/min in an argon atmosphere. The mass change during the decomposition of calcium silicate hydrate gels, portlandite, and calcite are determined, and the changes in the portlandite amount are estimated in dependence on the time of hydration.

scholarly journals Thermal expansion of nickel-chromium ChS88U alloy at high temperatures

2021 ◽  
Vol 2057 (1) ◽  
pp. 012116
Author(s):  
Yu M Kozlovskii ◽  
S V Stankus
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Temperature Dependence ◽  
High Temperatures ◽  
Reference Values ◽  
Experimental Results ◽  
Temperature Range ◽  
Nickel Chromium ◽  
Estimated Error

Abstract The experimental results of the study of thermal expansion of nickel-chrome alloy in the temperature range of 293.15–1400 K are presented. The phase transformation of the first kind in the alloy is observed. The estimated error of the obtained data is 3%. Approximation equations and a table of reference values for the temperature dependence of the studied properties are obtained.

scholarly journals Characterization of Early Pozzolanic Reaction of Calcium Hydroxide and Calcium Silicate Hydrate for Nanosilica Modified Cement Paste

2013 ◽  
Vol 4 (3) ◽  
pp. 6-10
Author(s):  
J.Z. Chong ◽  
N.M. Sutan ◽  
I. Yakub
Keyword(s):  
Calcium Hydroxide ◽  
Cement Paste ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Pozzolanic Reaction ◽  
Pozzolanic Reactivity ◽  
Characterization Technique ◽  
Binder Ratio ◽  
Ft Ir

This  study  intends  to  investigate  the  early   pozzolanic  reaction  of  Nanosilica (nS)         modified cement paste (NMCP)  by  the characterization technique  of Calcium Hydroxide (CH) and Calcium Silicate Hydrate (C-S-H ) using Fourier Transform Infrared Spectroscopy (FT-IR). NMCP samples were prepared with water-binder ratio of 0.50. nS of 5-15nm particle size were used as 1%, 3% ,5% ,7% and 10% replacement of cement by weight. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared and tested at day 1,7,21 and 28. It was found that characterization technique used were able to give satisfactory qualitative indication of pozzolanic reactivity of NMCP by the presence and absence of C-S-H and C-H that can indicate which replacement has higher pozzolanicity. NMCP exhibited a higher pozzolanic reactivity compare to conventional cement paste by which cement performance was enhanced.

Preparation of Low-Heat Portland Cement Clinker with Coal Gangue

2011 ◽  
Vol 306-307 ◽  
pp. 861-864
Author(s):  
Guang Li Chen ◽  
Xing Hua Fu ◽  
Wen Hong Tao
Keyword(s):  
Portland Cement ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Raw Materials ◽  
Coal Gangue ◽  
Cement Clinker ◽  
Mix Proportion ◽  
Portland Cement Clinker ◽  
Hydration Characteristics

A kind of low-heat Portland cement clinker was prepared with coal gangue, limestone and gypsum through optimizing the mix proportion of raw materials, and its properties and hydration characteristics were studied. The results showed that the cement clinker meeting the demands of mid (low)-heat Portland cement standard could be prepared with 35% (by weight, the same below) coal gangue, 57-60% limestone and 6-8% gypsum. The raw materials were burned at 1380°C for 40 minutes. The main hydrates were calcium silicate hydrate (C-S-H) gel, ettringite (AFt), monosulfate (AFm) and Ca(OH)2.

Hydration Products, Microstructure and Durability of Concrete with Metakaolin Addition

2016 ◽  
Vol 680 ◽  
pp. 420-428
Author(s):  
Qiu Li ◽  
Hai Ning Geng ◽  
Yun Huang ◽  
Zhong He Shui
Keyword(s):  
Diffusion Coefficient ◽  
Calcium Hydroxide ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Analytical Techniques ◽  
Pozzolanic Reaction ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Hydration Products ◽  
Durability Of Concrete

The durability, microstructure and hydration products of concrete containing 0-6wt% metakaolin (MK) were studied by analytical techniques. The hydration products were calcium hydroxide (CH), ettringite and calcium silicate hydrate gels in the control concrete, and additional monocarboaluminate and hemicarboaluminate were identified in concrete containing MK. CH content decreased by 28 days hydration in concrete containing MK, due to the pozzolanic reaction between MK and CH. Chloride diffusion coefficient decreased with the increase of MK content. By addition of 6wt% MK, chloride diffusion coefficient decreased by 60%.

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