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.

scholarly journals Enhanced Metakaolin Reactivity in Blended Cement with Additional Calcium Hydroxide

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 367
Author(s):  
Kira Weise ◽  
Neven Ukrainczyk ◽  
Aaron Duncan ◽  
Eduardus Koenders
Keyword(s):  
Calcium Hydroxide ◽  
Blended Cement ◽  
Initial Mixture ◽  
Pozzolanic Reaction ◽  
Replacement Ratio ◽  
Pozzolanic Reactivity ◽  
Thermogravimetric Data ◽  
Binder Ratio ◽  
Water To Binder Ratio ◽  
Mass Balance Approach

This study aims to increase the pozzolanic reactivity of metakaolin (MK) in Portland cement (PC) blends by adding additional calcium hydroxide (CH_add) to the initial mixture. Cement paste samples were prepared with PC, MK and water with a water-to-binder ratio of 0.6. Cement replacement ratios were chosen from 5 to 40 wt.% MK. For higher replacement ratios, i.e., 20, 30 and 40 wt.% MK, CH_add was included in the mixture. CH_add-to-MK ratios of 0.1, 0.25 and 0.5 were investigated. Thermogravimetric analysis (TGA) was carried out to study the pozzolanic reactivity after 1, 7, 28 and 56 days of hydration. A modified mass balance approach was used to normalize thermogravimetric data and to calculate the calcium hydroxide (CH) consumption of samples with CH_add. Results showed that, without CH_add, a replacement ratio of 30 wt.% or higher results in the complete consumption of CH after 28 days at the latest. In these samples, the pozzolanic reaction of MK turned out to be restricted by the amount of CH available from the cement hydration. The increased amount of CH in the samples with CH_add resulted in an enhanced pozzolanic reaction of MK as confirmed by CH consumption measurements from TGA.

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%.

scholarly journals Structure and nanomechanical characterization of synthetic calcium-silicate-hydrate with poly-methacrylic acid

2020 ◽  
Vol 13 (5) ◽  
Author(s):  
Fernando Pelisser ◽  
Philippe Jean Paul Gleize ◽  
Alexandre Mikowski
Keyword(s):  
Elastic Modulus ◽  
Methacrylic Acid ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Construction Materials ◽  
Physical And Mechanical Properties ◽  
Polymer Complexes ◽  
Cement Pastes ◽  
Ft Ir

ABSTRACT: The principal phase of hardened Portland cement pastes is calcium silicate hydrate (C-S-H), which influences the physical and mechanical properties of construction materials. In this work, calcium silicate hydrate (C-S-H) was synthesized, with the addition of poly-methacrylic acid with sodium (PMA), for the development of C-S-H/ polymer nanocomposites. Among the polymers available, PMA is indicated in the literature as one of those viable for producing C-S-H/polymer complexes. However, no consensus exists regarding the type of interaction this produces. The resulting compounds were characterized by XRD, FT-IR, TGA, carbon content (CHN), TEM, SEM and elastic modulus and hardness were measured by instrumented indentation. A significant change was verified in the nanomechanical properties of C-S-H with PMA, resulting in reduction in the elastic modulus and hardness. The set of results presented do not confirm the intercalation of PMA in the interlayer space of C-S-H, but presented evidence of the potential for intercalation, since changes in the microstructure clearly occurred.

scholarly journals Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

2021 ◽  
Vol 14 (4) ◽  
Author(s):  
Vanessa Fernandes Cesari ◽  
Fernando Pelisser ◽  
Philippe Jean Paul Gleize ◽  
Milton Domingos Michel
Keyword(s):  
Transition Zone ◽  
Cement Paste ◽  
Calcium Silicate ◽  
High Performance ◽  
Calcium Silicate Hydrate ◽  
Interfacial Transition Zone ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Nanomechanical Properties ◽  
Cementitious Matrix

abstract: Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

Use of Algerian Natural Mineral Deposit as Supplementary Cementitious Materials

2018 ◽  
Vol 34 ◽  
pp. 48-58 ◽  
Author(s):  
Karima Arroudj ◽  
Saida Dorbani ◽  
Mohamed Nadjib Oudjit ◽  
Arezki Tagnit-Hamou
Keyword(s):  
Mechanical Strength ◽  
Calcium Hydroxide ◽  
Cement Paste ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Heat Of Hydration ◽  
Cement Industry ◽  
Supplementary Cementitious Materials ◽  
Natural Mineral ◽  
Different Ages

Much of the current research on concrete engineering has been focused on including siliceous additions as supplementary cementitious materials (SCMs). Silica reacts with Calcium hydroxide release during cement hydration, and produces more C-S-H. The latter contributes to increase compactness, mechanical strengths and sustainability of concrete. This paper explores the hydration characteristics of cement paste based on various natural mineral additions, that are very abundant in Algeria and present a high silica content (ground natural pozzolana “PZ” and ground dune sand “DS”). For this purpose, several analyses were carried out on modified cement pastes and mortars. TheseSCMswere introduced by replacement levels of 15, 20 and 25 by weight of cement. We first, studied the effect of these SCMs on the heat of hydration and mechanical strength of mortars at different ages. The evolution of hydration of modified paste was studied, by using Thermal analysis (TG/TDA) at different ages, to analyze the Calcium Hydroxide (CH) content of the modified pastes. It is shown that the CH content of the mixes including SCMs is lower than that of the plain cement paste, indicating that silica reacts with the cement paste through a pozzolanic reaction. Increased pozzolanic activity results in higher amounts of Calcium Silicate Hydrate in the paste, which in turn results in higher compressive strength for modified cement mortars. Due to its crystalline morphology, the ground DS particles present a partial pozzolanic effect, compared to PZ which is semi-crystalline. Modified mortars by 20% DS can be the optimal composition. It presents satisfactory results: good mechanical strength and low heat of hydration. It can lead to an economic and sustainable concrete. Ground DS is very abounded in Africa and free of any impurities and can be a good alternativeSCMsin cement industry.

Thermal Activation on Phase Formation of Alkaline Activated Kaolin Based System

2013 ◽  
Vol 770 ◽  
pp. 262-266 ◽  
Author(s):  
Somsak Boonjaeng ◽  
Kedsarin Pimraksa ◽  
Arnon Chaipanich ◽  
Sutin Kuharuangrong ◽  
Prinya Chindaprasirt
Keyword(s):  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Thermal Activation ◽  
Pozzolanic Reaction ◽  
Zeolite X ◽  
High Concentration ◽  
Phase Development ◽  
Naoh Solution ◽  
Calcium Aluminosilicate ◽  
Alkali Activated

The research aim was to investigate phase development after pozzolanic reaction between metakaolin (MK) and calcium hydroxide (CH) with alkaline and thermal activations. The CH to MK ratio (C/M) of 0.4 generating CaO/SiO2 of 1.18 was selected in this study. Various concentrations of NaOH solutions (0.01, 0.1, 1, 3, 5 and 10 M) were used. The alkali activated samples were thermally activated at 25 °C, 70 °C, 90 °C and 130 °C for 4 h. Phase development under thermal activation of alkali activated metakaolin based system were investigated. At every temperature, C/M mixtures with 0.01 and 0.1 M NaOH promoted the formations of poorly crystalline calcium silicate hydrate (C-S-H(I)) and calcium aluminosilicate hydrate (CASH) compounds. With 3 and 5 M NaOH activations, sodium aluminosilicate hydrate (NASH) and sodium calcium silicate hydrate (NCSH) was formed. 1 M NaOH was found to be a boundary of phase transformation from C-S-H(I) and CASH to NASH and NCSH. In addition, zeolite X and sodalite appeared when NaOH solution reached 10 M. Thermal activation significantly affected phase development at high concentration of alkaline activation (1-10 M). At 1 M NaOH, NASH compounds in a form of gmelinite and zeolite ZK-14 were found at 70-90 °C. At 3-5 M, katoite was found at 70-130 °C. At 10 M, zeolite X was found at 70-90 °C. Sodalite was also found at 130 °C with 10 M NaOH.

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