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.

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 A Mass Balance Approach for Thermogravimetric Analysis in Pozzolanic Reactivity R3 Test and Effect of Drying Methods

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5859
Author(s):  
Kira Weise ◽  
Neven Ukrainczyk ◽  
Eduardus Koenders
Keyword(s):  
Thermogravimetric Analysis ◽  
Mass Balance ◽  
Calcium Hydroxide ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Supplementary Cementitious Materials ◽  
Drying Methods ◽  
Calorimetric Measurement ◽  
Balance Approach ◽  
Mass Balance Approach

The reactivity of supplementary cementitious materials (SCMs) is a key issue in the sustainability of cement-based materials. In this study, the effect of drying with isopropanol and acetone as well as the interpretation of thermogravimetric data on the results of an R3 test for evaluation of the SCM pozzolanic reaction were investigated. R3 samples consisting of calcium hydroxide, potassium hydroxide, potassium sulphate, water, and SCM were prepared. Besides silica fume, three different types of calcined clays were investigated as SCMs. These were a relatively pure metakaolin, a quartz-rich metakaolin, and a mixed calcined clay, where the amount of other types of clays was two times higher than the kaolinite content. Thermogravimetric analysis (TGA) was carried out on seven-day-old samples dried with isopropanol and acetone to stop the reaction processes. Additional calorimetric measurement of the R3 samples was carried out for evaluation of the reaction kinetics. Results show that drying with isopropanol is more suitable for analysis of R3 samples compared to acetone. The use of acetone results in increased carbonation and TGA mass losses until 40 (isothermal drying for 30 min) and 105 °C (ramp heating), indicating that parts of the acetone remain in the sample, causing problems in the interpretation of TGA data. A mass balance approach was proposed to calculate calcium hydroxide consumption from TGA data, while also considering the amount of carbonates in the sample and TGA data corrections of original SCMs. With this approach, an improvement of the linear correlation of TGA results and heat release from calorimetric measurement was achieved.

Effect of Rice Husk Ash Fineness on the Properties of Concrete

2014 ◽  
Vol 554 ◽  
pp. 203-207 ◽  
Author(s):  
Sri Jayanti Dewi ◽  
Putra Jaya Ramadhansyah ◽  
Abdul Hassan Norhidayah ◽  
A. Aziz Md. Maniruzzaman ◽  
Mohd Rosli Hainin ◽  
...  
Keyword(s):  
Rice Husk ◽  
Permeability Coefficient ◽  
Rice Husk Ash ◽  
Gas Permeability ◽  
Blended Cement ◽  
Target Strength ◽  
Cement Concrete ◽  
Mechanical Grinding ◽  
Binder Ratio ◽  
Water To Binder Ratio

In the present research, the effect of rice husk ash fineness on the properties of concrete was studied. Eight different fineness grades of rice husk ash were examined. A rice husk ash dosage of 15% by weight of binder was used throughout the experiments. The water-to-binder ratio was 0.49 to produce concrete having target strength of 40MPa at 28 d. Workability, compressive strength and gas permeability tests were carried out to identify the properties of concrete. The results revealed that increasing the fineness of RHA by mechanical grinding was found to improve the workability of RHA blended cement concrete. In addition, the use of RHA3 with mean particle size of 9.52μm produces the concrete with good strength. Finally, significant improvement was observed in mixtures incorporating RHA in terms of permeability coefficient.

Analysis of the Effect of Fly Ash on Compressive Strength of Concrete Using Neural Network and Parameter Analysis

2020 ◽  
Vol 995 ◽  
pp. 130-135
Author(s):  
Xiao Yong Wang
Keyword(s):  
Neural Network ◽  
Compressive Strength ◽  
Fly Ash ◽  
Network Model ◽  
Neural Network Model ◽  
Parameter Analysis ◽  
Replacement Ratio ◽  
The Neural Network ◽  
Binder Ratio ◽  
Water To Binder Ratio

Compressive strength is a crucial design index of fly ash blended concrete. This study presents an estimation model to show the effect of fly ash on the strength development of concrete. First, a neural network model is proposed to estimate the compressive strength of fly ash blended concrete. The input variables of the neural network are water-to-binder ratio, fly ash replacement ratio, and curing ages. The output result of the neural network is a strength. The range of water-to-binder ratio is from 0.3 to 0.5, the range of fly ash replacement ratio is from 0 to 0.55, and the range of test age is from 3 days to 180 days. The neural network gives an accurate evaluation of compressive strength. Second, parameter analysis is carried out based on the neural network model. The results of parameter analysis show that the effect of fly ash on strength is dependent on water-to-binder ratio. The using of high-volume fly ash with low water-to-binder ratio concrete is a rational option.

scholarly journals Reuse of Sintered Sludge from Municipal Sewage Treatment Plants for the Production of Lightweight Aggregate Building Mortar

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 999
Author(s):  
Changyong Li ◽  
Xiaoyan Zhang ◽  
Bingxin Zhang ◽  
Yunfei Tan ◽  
Fenglan Li
Keyword(s):  
Fly Ash ◽  
Sewage Treatment ◽  
Lightweight Aggregate ◽  
Limestone Powder ◽  
Municipal Sewage ◽  
Dry Density ◽  
Replacement Ratio ◽  
Sewage Treatment Plants ◽  
Binder Ratio ◽  
Water To Binder Ratio

In recent years, the sludge produced by municipal sewage treatment plants has become an important recyclable resource for producing green building materials. After the systematic processing of incineration and particle formation, the sintered sludge can be processed into fine lightweight aggregate to produce building mortar with the controlled leaching of heavy metals and radioactivity. In this paper, to increase its economic and environmental benefits, mortar with sintered sludge aggregate was made by cement admixing of fly ash or limestone powder. The water-to-binder ratio was set at three levels—0.82, 0.68, and 0.62—and either flay ash or limestone powder was used to replace equal masses of cement at 10%, 20%, or 30%. Eighteen groups of mortar were studied to evaluate their workability, air content, compressive strength, tensile adhesive strength, dry density, and thermal conductivity. The results indicate that with a proper water-to-binder ratio, and the replacement ratio of fly ash or limestone powder, the mortar can be produced with good workability, consistency, water-retention rate, layering degree, and setting time. The mortar made with sintered sludge lightweight aggregate, designated by the mix-proportion method for conventional lightweight aggregate mortar, did not meet the target strength, although the compressive strength of mortar was no less than 3.0 MPa, which meets the strength grade M2.5. The tensile adhesive strength reached 0.18 MPa. The mortar was super lightweight with a dry density less than 400 kg/m3, and a thermal conductivity within 0.30~0.32 W/(m⋅K). The effects of water-to-binder ratio and replacement ratio of fly ash or limestone powder on the above properties are discussed with test results. The study provides a basis for using sintered sludge lightweight aggregate for building mortar.

Support Vector Machine (SVM)-Based Optimal Design Procedure of Fly Ash Blended Concrete

2021 ◽  
Vol 894 ◽  
pp. 103-108
Author(s):  
Tae Wan Kim ◽  
Jong Yeon Lim ◽  
Xiao Yong Wang ◽  
Yi Han
Keyword(s):  
Support Vector Machine ◽  
Compressive Strength ◽  
Fly Ash ◽  
Optimal Design ◽  
Design Procedure ◽  
Support Vector ◽  
Replacement Ratio ◽  
Svm Model ◽  
Binder Ratio ◽  
Water To Binder Ratio

A support vector machine (SVM) is widely used for predicting the properties of fly ash blended concrete. However, the studies about the optimal design of fly ash blended concrete based on SVM are very limit. This study shows an SVM-based optimal design procedure of fly ash blended concrete. First, we built an SVM model and evaluated the compressive strength of fly ash blended concrete considering the effects of water to binder ratio, fly ash replacement ratio, and test ages. Second, we made parameter studies based on the SVM model. The parameter studies show that fly ash can improve the late age strength of concrete. This improvement is obvious for concrete with lower water to binder ratio. The optimal fly ash replacement ratio increases as the water to binder ratio decreases.

scholarly journals Analysis Technique on Water Permeability in Concrete with Cold Joint considering Micro Pore Structure and Mineral Admixture

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Se-Jin Choi ◽  
Suk-Pyo Kang ◽  
Sang-Chel Kim ◽  
Seung-Jun Kwon
Keyword(s):  
Water Permeability ◽  
Mineral Admixture ◽  
Portland Cement Concrete ◽  
Replacement Ratio ◽  
Water Permeation ◽  
Analysis Technique ◽  
Binder Ratio ◽  
Joint Width ◽  
Water To Binder Ratio ◽  
Representative Element Volume

Cold joint in concrete due to delayed concrete placing may cause a reduced shear resistance and increased water permeation. This study presents an analytical model based on the concept of REV (Representative Element Volume) to assess the effect of water permeability in cold joint concrete. Here, OPC (Ordinary Portland Cement) concrete samples with cold joint are prepared and WPT (Water Permeability Test) is performed on the samples cured for 91 days. In order to account for the effect of GGBFS (Granulated Ground Blast Furnace Slag) on water permeability, concrete samples with the same W/B (Water to Binder) ratio and 40% replacement ratio of GGBFS are tested as well. Utilizing the previous models handling porosity and saturation, the analysis technique for equivalent water permeability with effective cold joint width is proposed. Water permeability in cold joint increases to 140.7% in control case but it decreases to 120.7% through GGBFS replacement. Simulation results agree reasonably well with experimental data gathered for sound and cold joint concrete.

scholarly journals Experimental Investigation and Theoretical Modeling of Nanosilica Activity in Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Han-Seung Lee ◽  
Hyeong-Kyu Cho ◽  
Xiao-Yong Wang
Keyword(s):  
Compressive Strength ◽  
Calcium Hydroxide ◽  
Blended Cement ◽  
Bound Water ◽  
Pozzolanic Reaction ◽  
Theoretical Modeling ◽  
Experimental Investigations ◽  
Hydration Reaction ◽  
Degree Of Hydration ◽  
Water Contents

This paper presents experimental investigations and theoretical modeling of the hydration reaction of nanosilica blended concrete with different water-to-binder ratios and different nanosilica replacement ratios. The developments of chemically bound water contents, calcium hydroxide contents, and compressive strength of Portland cement control specimens and nanosilica blended specimens were measured at different ages: 1 day, 3 days, 7 days, 14 days, and 28 days. Due to the pozzolanic reaction of nanosilica, the contents of calcium hydroxide in nanosilica blended pastes are considerably lower than those in the control specimens. Compared with the control specimens, the extent of compressive strength enhancement in the nanosilica blended specimens is much higher at early ages. Additionally, a blended cement hydration model that considers both the hydration reaction of cement and the pozzolanic reaction of nanosilica is proposed. The properties of nanosilica blended concrete during hardening were evaluated using the degree of hydration of cement and the reaction degree of nanosilica. The calculated chemically bound water contents, calcium hydroxide contents, and compressive strength were generally consistent with the experimental results.

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