scholarly journals Reutilizing Waste Iron Tailing Powders as Filler in Mortar to Realize Cement Reduction and Strength Enhancement

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 541
Author(s):  
Liyun Cui ◽  
Peiyuan Chen ◽  
Liang Wang ◽  
Ying Xu ◽  
Hao Wang
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Economic Cost ◽  
Strength Development ◽  
Effective Utilization ◽  
Strength Enhancement ◽  
Nucleation Effect ◽  
Practical Engineering ◽  
Internal Mechanism ◽  
Massive Accumulation

Recently, the massive accumulation of waste iron tailings powder (WITP) has resulted in significant environmental pollution. To solve this problem, this paper proposes an original mortar replacement (M) method to reuse waste solids and reduce cement consumption. In the experiment, the author employed an M method which replaces water, cement, and sand with WITP under constant water/cement and found that the strength development can be significantly improved. Specifically, a mortar with 20% WITP replacement can obtain a 30.95% improvement in strength development. To study the internal mechanism, we performed experiments such as thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), and SEM. The results demonstrate that the nucleation effect and pozzolanic effect of WITP can help promote cement hydration, and MIP reveals that WITP can effectively optimize pore structure. In addition, 1 kg 20% WITP mortar reduced cement consumption by 20%, which saves 19.98% of the economic cost. Comprehensively, our approach achieves the effective utilization of WITP and provides a favorable reference for practical engineering.

scholarly journals Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3

2020 ◽  
Vol 9 (1) ◽  
pp. 998-1008
Author(s):  
Guo Li ◽  
Zheng Zhuang ◽  
Yajun Lv ◽  
Kejin Wang ◽  
David Hui
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Hardened Concrete ◽  
Optimal Dosage ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Carbonation Depth ◽  
X Ray ◽  
Chloride Resistance

AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

The Pozzolanic Reaction of Silica Fume

2012 ◽  
Vol 1488 ◽  
Author(s):  
Ole M. Jensen
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Cement Hydration ◽  
Theoretical Calculations ◽  
Pozzolanic Reaction ◽  
Interfacial Transition Zone ◽  
Strength Development ◽  
Micro Structure ◽  
Cementitious Binder ◽  
Portland Cement Hydration

ABSTRACTSilica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy of activation of the pozzolanic reaction of silica fume is estimated. The results show that the pozzolanic reaction of silica fume has notable differences from Portland cement hydration.

Cement Hydration and Strength Development-How Can Reproducible Results be Achieved? - Part 1

2014 ◽  
pp. 1057-1060 ◽  
Author(s):  
Dagmar Schmidtmeier ◽  
Geert Warns ◽  
Stefan Kuiper ◽  
Sebastian Klaus ◽  
Friedlinde Götz-Neunhöfer ◽  
...  
Keyword(s):  
Cement Hydration ◽  
Strength Development

scholarly journals The possibility of shrinkage strain reduction in cements mortars

2018 ◽  
Vol 174 ◽  
pp. 02013
Author(s):  
Maciej Gruszczyński ◽  
Grzegorz Bajorek
Keyword(s):  
Cement Hydration ◽  
Shrinkage Strain ◽  
Strength Development ◽  
Action Mechanism ◽  
Chemical Admixtures ◽  
Cement Mortars ◽  
Different Types ◽  
The Subject ◽  
Polymer Dispersions ◽  
Styrene Butadiene

The subject of the paper is presentation of action mechanism and effectiveness estimation of different types of chemical admixtures that make it possible to control the course of shrinkage strains associated with cement hydration process. There are presented tests results from the research program realization in which there were used the basic types of admixtures allowing for producing mortars and concretes with reduced or compensated shrinkage. In conducted tests there were applied admixtures based on calcium oxide, multi-molecule alcohol as well as water polymer dispersions (styrene-acrylic co-polymer - SA and styrene-butadiene latex - SBR). Their influence onto the magnitude of shrinkage strain and strength development for cement mortars was analyzed.

Evaluation of Contributing Factors on Strength Development of Lime Stabilized Artificial Organic Soils Using Statistical Design of Experiment Approach

2014 ◽  
Vol 905 ◽  
pp. 362-368 ◽  
Author(s):  
Felix N.L. Ling ◽  
Khairul Anuar Kassim ◽  
Ahmad Tarmizi Abdul Karim ◽  
S.C. Ho
Keyword(s):  
Organic Matter ◽  
Statistical Design ◽  
Organic Soil ◽  
Curing Temperature ◽  
Organic Soils ◽  
Strength Development ◽  
Test Results ◽  
Contributing Factors ◽  
Strength Enhancement ◽  
Factor Interactions

Lime is widely used as chemical stabilizer in soft soil stabilization. However, lime is reported to be less effective when dealing with organic soil. It is believed that the organic matter in the soil will retard the pozzolanic reaction which is responsible for strength enhancement. The heterogeneity nature of the organic matter in the soil makes the study complicated and reduced the repeatability of the test results. Hence, artificial organic soil with known organic matter and content are preferred by researchers when repeatability of the test results are required in determining the influential effect of each contribution factor. Various factors such as additive contents, effect of aging (curing periods), curing temperature, density of materials and moisture content are reported by previous researchers as the potential contributing factors towards the strength development. It is believed that the interaction of the factors also will contribute to the strength enhancement. Hence, this study is carried out to evaluate the contributing factors and its interactions on strength development of artificial organic soils with known type and contents of organic matter. Statistical design of experiment (DOE) approach was utilized to evaluate the factors and its interaction on the strength development of lime stabilized artificial organic soils by using commercial statistics package. Three main factors were investigated: effect of organic content, effect of curing periods, and effect of additive, while other factors namely curing temperature, molding water content, types of compaction and compactive effort were keep constant through controlled experiments. Processed kaolin (inorganic material) is mixed with humic acid (organic matter) to simulate the organic soil which comprised of inorganic soil and organic matter. The density of the soil specimen and its moisture content were recorded before and after the curing process. General Linear Model (GLM) was utilized to determine the significance of the main factors, two-factor interactions, and three factor interactions. The significance factors and interactions were utilized in multiple regression analysis to develop the strength prediction model which can be utilized to predict the strength of stabilized materials within the inference space defined by the experiment.

Towards a Bacteria-Based Agent to Make Concrete Self-Healing

2012 ◽  
Vol 1488 ◽  
Author(s):  
Renee M. Mors ◽  
Henk M. Jonkers
Keyword(s):  
Cement Hydration ◽  
Calcium Lactate ◽  
Strength Development ◽  
Self Healing ◽  
Standard Mixture ◽  
Organic Salts ◽  
Organic Mineral ◽  
Healing Agent ◽  
Polycarboxylate Ether ◽  
Concrete Matrix

ABSTRACTA bacteria-based healing agent for concrete is currently under development in the Microlab of TU Delft. The agent consists of organic mineral precursor compound and bacteria in a protective reservoir. Cracks in the concrete matrix may be sealed and blocked by calcium carbonate based crystals, formed by bacterial conversion of mineral precursor compound. Given the solubility of the agent components, healing agent material may be prematurely released during the wet mixing stage, potentially influencing cement hydration and functionality of other concrete additions. Several materials have been selected as potential mineral precursor compound, being organic salts and a carbohydrate. Tests on standard mortar specimens show that strength development is not compromised when calcium lactate is added to the standard mixture. Calcium lactate was added to the mortar mixture either pure or in combination with a superplasticizer, either based on sulfonated naphthalene or modified polycarboxylate ether, to determine possible interferential effects.

scholarly journals Peat soil mass stabilization using geopolymeric hybrid material in early age

2019 ◽  
Vol 276 ◽  
pp. 05003
Author(s):  
Gunawan Wibisono ◽  
Erwin ◽  
Alfian Kamaldi ◽  
Monita Olivia
Keyword(s):  
Fly Ash ◽  
Cement Hydration ◽  
Peat Soil ◽  
High Water ◽  
Organic Soil ◽  
Soil Mass ◽  
High Water Content ◽  
Strength Development ◽  
Initial Strength ◽  
Pozzolanic Material

Peat is an organic soil, highly compressible and has high water content. The soil needs to be stabilized chemically by incorporating binders such as cement and lime into the soil that will change the properties and soil strength. However, stabilization using cement solely is not recommended since the organic acid in peat soil could delay cement hydration process. Furthermore, mass stabilization using pozzolanic material also could improve strength development of peat soil. In this research, the pozzolanic material in the form of geopolymer hybrid or geopolymer with the addition of Ordinary Portland Cement was investigated. Geopolymer was produced by activating fly ash with a combination of NaOH and sodium silicate. OPC addition improves initial strength and assists geopolymerization at ambient temperature. Variables studied were binder content and a percentage of OPC, and percentage of fly ash. Unconfined Compressive Stress (UCS) at 7 days was measured for all specimens. Mass stabilization using fly ash geopolymer hybrid could improve strength development of peat soil.

scholarly journals Comparative study on mechanisms for improving mechanical properties and microstructure of cement paste modified by different types of nanomaterials

2021 ◽  
Vol 10 (1) ◽  
pp. 370-384
Author(s):  
Tao Meng ◽  
Kanjun Ying ◽  
Xiufen Yang ◽  
Yongpeng Hong
Keyword(s):  
Mechanical Properties ◽  
Cement Paste ◽  
Cement Hydration ◽  
Inhibitory Effect ◽  
Test Methods ◽  
Cement Clinker ◽  
Hydration Products ◽  
Nucleation Effect ◽  
Nano Graphene ◽  
Nano Titanium Dioxide

Abstract Filling and nucleation are the mechanisms of modifying cement paste with nanomaterials, as investigated by previous studies, and are difficult to reflect the different effects of nanomaterials, especially on the changes of cement clinker and hydration products in the cement hydration process. In this study, the mechanisms of modifying cement paste with nano-calcium carbonate (NC), nano-graphene oxide (NG), nano-silica (NS), and nano-titanium dioxide (NT) were investigated by determining the mechanical properties of cement paste treated with nanomaterials and analysing the changes in the cement clinker (tricalcium silicate and dicalcium silicate), hydration products (portlandite and ettringite), and microstructure through many micro-test methods. The results indicate that the incorporation of nanomaterials could improve the early strength of cement paste specimens due to more consumption of cement clinker. Meanwhile, different nanomaterials promote the formation of different hydration products at early ages. C–A–S–H gel, flower-like ettringite, and C–S–H seeds are widely distributed in the cement paste with the incorporation of NC, NG, and NS, respectively. NT exhibits insignificant nucleation effect and has inhibitory effect on portlandite precipitation. This study provides key insights into the mechanism of nanomaterials from the perspective of cement hydration, which may promote the further research and application of nanomaterials in the cement and concrete industries.

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