scholarly journals Influence of Mineral Additives on the Efflorescence of Ettringite-Rich Systems

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5464
Author(s):  
Linglin Xu ◽  
Siyu Liu ◽  
Peiming Wang ◽  
Zhenghong Yang
Keyword(s):  
Pore Structure ◽  
Silica Fume ◽  
Optical Microscope ◽  
Cementitious Materials ◽  
Mineral Admixture ◽  
Limestone Powder ◽  
Capillary Absorption ◽  
In Situ Raman Spectroscopy ◽  
Multi Scale ◽  
Mineral Additives

Efflorescence is aesthetically undesirable to all cementitious materials products and mainly results from the carbonation of hydrates and salt precipitation. Alternative binders without portlandite formation theoretically have much lower efflorescence risk, but in practice, the efflorescence of ettringite-rich systems is still serious. This study reports the impacts of mineral additives on the efflorescence of ettringite-rich systems and the corresponding microstructural evolution. The effects of silica fume, limestone powder, and diatomite on efflorescence and the capillary pore structure of mortars were investigated from a multi-scale analysis. The composition and microstructure of efflorescent phases were revealed by optical microscope (O.M.), in-situ Raman spectroscopy, and Scanning Electron Microscopy (SEM). Results indicate that the addition of mineral additives can efficiently inhibit the efflorescence of reference, especially with silica fume. Similar to the ettringite-rich system, the efflorescence substances of all modifies are composed of ettringite and CaCO3, indicating that the addition of mineral admixture does not lead to chemical reactions, lower capillary absorption coefficient of mineral additives modified specimen, the denser pore structure and the lower efflorescence degree.

scholarly journals Effects of Nano-CaCO3/Limestone Composite Particles on the Hydration Products and Pore Structure of Cementitious Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Huashan Yang ◽  
Yujun Che
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Reaction System ◽  
Cementitious Materials ◽  
Limestone Powder ◽  
Composite Particles ◽  
Gravimetric Analysis ◽  
Hydration Products ◽  
Scanning Calorimetry ◽  
Necked Flask

The agglomeration of nano-CaCO3 (NC) is the largest bottleneck in applications in cementitious materials. If nano-CaCO3 modifies the surface of micron-scale limestone powder (LS), then it will form nano-CaCO3/limestone composite particles (NC/LS). It is known that micron-scale limestone is easily dispersed, and the “dispersion” of NC is governed by that of LS. Therefore, the dispersion of nano-CaCO3 can be improved by the NC/LS in cementitious materials. In this work, the preparation of NC/LS was carried out in a three-necked flask using the Ca(OH)2-H2O-CO2 reaction system. The morphology of NC/LS was observed by a field emission scanning electron microscope (FE-SEM). The effects of NC/LS on the hydration products and pore structure of cementitious materials are proposed. 5% NC/LS was added into cement paste and mortar, and the mechanical properties of the specimens were measured at a certain age. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TG), and backscattered electron imaging (BSE) were conducted on the specimens to investigate the hydration products and pore structure. The properties of specimens with NC/LS were compared to that of control specimens (without NC/LS). The results revealed that NC/LS reduced the porosity and improved the mechanical properties of the cementitious materials.

scholarly journals Study of Hydration and Microstructure of Mortar Containing Coral Sand Powder Blended with SCMs

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4248
Author(s):  
Xingxing Li ◽  
Ying Ma ◽  
Xiaodong Shen ◽  
Ya Zhong ◽  
Yuwei Li
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Silica Fume ◽  
Dilution Effect ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Limestone Powder ◽  
Chemical Effect ◽  
Granulated Blast Furnace Slag ◽  
Coral Sand

The utilization of coral waste is an economical way of using concrete in coastal and offshore constructions. Coral waste with more than 96% CaCO3 can be ground to fines and combined with supplementary cementitious materials (SCMs) such as fly ash, silica fume, granulated blast furnace slag in replacing Portland cement to promote the properties of cement concrete. The effects of coral sand powder (CSP) compared to limestone powder (LSP) blended with SCMs on hydration and microstructure of mortar were investigated. The result shows CSP has higher activity than LSP when participating in the chemical reaction. The chemical effect among CSP, SCMs, and ordinary Portland cement (OPC) results in the appearance of the third hydration peak, facilitating the production of carboaluminate. CSP-SCMs mortar has smaller interconnected pores on account of the porous character of CSP as well as the filler and chemical effect. The dilution effect of CSP leads to the reduction of compressive strength of OPC-CSP and OPC-CSP-SCMs mortars. The synergic effects of CSP with slag and silica fume facilitate the development of compressive strength and lead to a compacted isolation and transfer zone (ITZ) in mortar.

scholarly journals Ink-bottle Effect and Pore Size Distribution of Cementitious Materials Identified by Pressurization–Depressurization Cycling Mercury Intrusion Porosimetry

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1454 ◽  
Author(s):  
Yong Zhang ◽  
Bin Yang ◽  
Zhengxian Yang ◽  
Guang Ye
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Mercury Intrusion Porosimetry ◽  
Cementitious Materials ◽  
Limestone Powder ◽  
Accurate Estimation ◽  
Mercury Intrusion ◽  
Pore Size Distributions

Capturing the long-term performance of concrete must be underpinned by a detailed understanding of the pore structure. Mercury intrusion porosimetry (MIP) is a widely used technique for pore structure characterization. However, it has been proven inappropriate to measure the pore size distribution of cementitious materials due to the ink-bottle effect. MIP with cyclic pressurization–depressurization can overcome the ink-bottle effect and enables a distinction between large (ink-bottle) pores and small (throat) pores. In this paper, pressurization–depressurization cycling mercury intrusion porosimetry (PDC-MIP) is adopted to characterize the pore structure in a range of cementitious pastes cured from 28 to 370 days. The results indicate that PDC-MIP provides a more accurate estimation of the pore size distribution in cementitious pastes than the standard MIP. Bimodal pore size distributions can be obtained by performing PDC-MIP measurements on cementitious pastes, regardless of the age. Water–binder ratio, fly ash and limestone powder have considerable influences on the formation of capillary pores ranging from 0.01 to 0.5 µm.

Strength and Transport Properties of Concretes Modified with Coarse Limestone Powder to Compensate for Dilution Effects

2012 ◽  
Vol 2290 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Narayanan Neithalath ◽  
Hieu T. Cam
Keyword(s):  
Pore Structure ◽  
Silica Fume ◽  
Dilution Effect ◽  
Limestone Powder ◽  
Structure Parameter ◽  
Pore Structure Parameter ◽  
Replacement Level ◽  
Chloride Permeability ◽  
Cement Replacement ◽  
The Impact

The use of a coarse limestone powder (median particle size of approximately 70 μm, five times larger than cement particles) as a cement replacement material results in a dilution effect. The magnitude of strength and transport property reduction is found to be greater than the magnitude of the cement replacement level. In this paper, methodologies to proportion concrete containing 10% to 15% of coarse limestone powder, in which the dilution effect is compensated through a combination of reduction in water-to-powder ratio and addition of 5% of silica fume, are discussed. Limestone–silica fume blended concretes at a reduced water-to-powder ratio (0.37 or 0.34, depending on limestone replacement level) show similar or higher 56-day compressive strengths than does the benchmark plain concrete with a water-to-cement ratio of 0.40. The rapid chloride permeability and non–steady state migration values of the modified concretes are evaluated along with their pore structure parameter extracted from electrical impedance data. The impact of water-to-powder reduction and silica fume incorporation is quantified through this pore structure parameter.

scholarly journals Efficiency Concepts and Models that Evaluates the Strength of Concretes Containing Different Supplementary Cementitious Materials

2019 ◽  
Vol 5 (1) ◽  
pp. 18 ◽  
Author(s):  
Rahul Biswas ◽  
Baboo Rai
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Research Work ◽  
Cementitious Materials ◽  
Mineral Admixture ◽  
Supplementary Cementitious Materials ◽  
Hardened Concrete ◽  
Effective Utilization ◽  
Natural Pozzolans ◽  
Quantitative Understanding

The usage of Supplementary Cementitious Materials (SCM) is very much acknowledged due to the several improvements possible in the concrete composites, and because of the general economy. Research work till date suggests that utilization of SCMs enhance a significant number of the performance characteristics of the hardened concrete. The idea of efficiency can be utilized for comparing the relative performance of different pozzolans when incorporated into concrete. The efficiency concept, which was initially developed for fly ash, can be effortlessly connected to other advantageous s as well, such as silica fume, slag and natural pozzolans. A quantitative understanding of the efficiency of SCMs as a mineral admixture in concrete is essential for its effective utilization. The paper reviews the literature pertaining to the different efficiency concepts and models present to date that evaluates the strength of concretes containing different SCMs. This short survey demonstrates that there is a need for a superior comprehension of the SCMs in concrete for its powerful usage. Also, it is an effort directed towards a specific understanding of the efficiency of SCMs in concrete.

Study on Ultra-Strength Mortar Prepared with Mineral Admixture

2011 ◽  
Vol 675-677 ◽  
pp. 1073-1076
Author(s):  
Zu Quan Jin ◽  
Peng Zhang ◽  
Tie Jun Zhao ◽  
Bao Rong Hou
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Pore Structure ◽  
Silica Fume ◽  
Mineral Admixture ◽  
Replacement Rate ◽  
River Sand ◽  
Optimum Proportion ◽  
Curing Age

In this paper, preparation, property study of ultra-strength mortars with mineral admixture and clear river sand was carried out. The mineral admixture include fly ash, ultra-fine GGBS and silica fume. The experimental results show that the compressive strength of mortar improves with increasing amount of silica fume or ultra-fine GGBS. When the content of silica fume or ultra-fine GGBS is 30~35%, the compressive strength and flexural strength of mortar in curing age of 7 days are 100 MPa and 20MPa, respectively. But strength of mortar decreases with the increase replacement rate of fly ash. When the mortar mixes with combined of silica fume and ultra-fine GGBS, the optimum proportion of siliaca fume to ultra-fine GGBS is 2:3. And the compressive strength of mortar in curing age of 7 days is 75~100MPa when the mixed mineral admixture is 40~60%. The compressive strength of mortar is about 90MPa as it mix 60% of cement, 15% of silica fume, 15% of GGBS and 10% of fly ash. Moreover, the ultra strength mortar refines its pore structure and its capiliary pore (≥100nm) amount reduces by 78% compared to ordinary mortar.

Physical Filling Effects of Limestone Powders with Different Particle Size

2010 ◽  
Vol 163-167 ◽  
pp. 1419-1424 ◽  
Author(s):  
Yu Li Wang ◽  
Wei Dong Wang ◽  
Xue Mao Guan
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Mineral Admixture ◽  
Limestone Powder ◽  
Cement Stone ◽  
Particle Sizes ◽  
Powder Mixtures ◽  
Mass Proportion ◽  
Void Structure ◽  
Compressive Strength Of Concrete

Physical filling effects of limestone powders, which are stated by compactness change of mixtures of limestone powders and cement, play an important role in the pore structure and strength of cement stone. The compactness of mixture of limestone powders and cement has been analyzed by the method of wet packing density, tested the void structure of cement stone by mercury intrusion porosimetry(MIP) and strength of cement stone. Effects of limestone powders with specific areas of individually 416m2/kg, 841m2/kg, 1243m2/kg on compactness of cement, compressive strength of concrete as mineral admixture, and pore structure of cement stone were studied when its cement is substituted for the mass proportion of 5, 10, 15% with it. The results show that the compactness of powder mixtures and compressive strength of concrete are biggest, and the improvement of pore structure of cement stone is the best when limestone powder is 10%; the compactness of powder mixtures and compressive strength of concrete are bigger, and the improvement of pore structure of cement stone is better when limestone powder is finer. That is to say, the proportion of limestone powder is the best substitution at 10%; physical filling effects of limestone powder are better when limestone powder is finer from particle sizes. It is important guiding meaning for the application of limestone powder in cement materials.

Testing of Composite Mortars Based on Supplementary Cementitious Materials: Estimating Durability and Thermal Properties

2016 ◽  
Vol 27 ◽  
pp. 27-35 ◽  
Author(s):  
N. Latroch ◽  
A.S. Benosman ◽  
N. Bouhamou ◽  
B. Belbachir ◽  
Y. Senhadji ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Composite Materials ◽  
Silica Fume ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Experimental Methodology ◽  
Natural Pozzolan ◽  
Adhesion Properties ◽  
Mineral Additives ◽  
Polymer Latex

The growing need for building material resources, and the requirements to preserve the environment, in a vision of sustainable development, has become necessary to study reinforcement techniques, using composite materials. Using local organic or inorganic materials in construction fields and public works is particularly important. Polymer mortar composites (PMC) are usually employed in the building industry as finishing materials, tile adhesive (mortar-adhesive) or façade coating. In repair applications, the addition of soluble polymer (latex) allows improving the adhesion properties of the materials used as coating. The use of mineral additives as partial substitutes for cement, in construction sites as well as in ready-to-use mortars, is an unknown practice in our country. For this reason, we thought it is crucial to study and assess the influence of these additions on the properties of cured composite. Supplementary cementitious materials (SCM) used in this study are silica fume and natural pozzolan, which necessarily need to be valorized.The present research work aims to use a specific experimental methodology that is able to identify the relationship between the degree of substitution by the mineral additives, the polymer and the modifications to the properties of fresh and hardened cement mixtures. Therefore, five PMC combinations were formulated from different percentages of additions, i.e. natural pozzolan (NP: 25%w), silica fume (Sf: 5%w) and polymer latex (P: 0, 5, 7.5, 10, 12.5 and 15%w). Their durability factors, such as the porosity accessible to water and capillary absorption rate (sorptivity), were characterized, at different maturities. An attempt was also made to determine the thermal coefficients. The results obtained were compared with those of the reference mortars, made with Portland cement (CEMI). They showed that the decrease in porosity, sorptivity and thermal conductivity depends on the pair “SCMs/polymer”. But overall, the addition of polymer latex and pozzolanic additions have a beneficial effect on the durability and thermal properties of the composite materials.

scholarly journals Chemical Analysis of Silica Fume Infused Self Healing Concrete

2020 ◽  
Vol 8 (6) ◽  
pp. 1430-1432
Keyword(s):  
Silica Fume ◽  
Thin Section ◽  
Healing Process ◽  
Xrd Analysis ◽  
Silica Content ◽  
Mineral Admixture ◽  
Limestone Powder ◽  
Self Healing ◽  
Healing Property ◽  
Thin Section Analysis

Self healing technique using mineral and chemical admixtures are gaining momentum nowadays. Admixtures like silica fume, marble dust, fly ash, ground granulated blast furnace slag, limestone powder are being experimented nowadays as self healing agents. In this experimental examination, silica fume has been used as a healing agent (12.5% replacement). Cracks were induced and the specimens were subjected to continuous water exposure for 28 days. After 28 days, the specimens were tested for healing effect and the healing products were chemically analyzed by means of FESEM analysis, EDAX, thin section test and XRD analysis. From FESEM and EDAX analysis, for silica fume mix, portlandite formation was evident. Thin section analysis showed the morphology of anorthite feldspar. XRD analysis showed that excess silica content in silica fume actively involved in faster healing process resulting in the formation of calcite, calcium hydroxide and calcium carbonate. All the test results indicated that self healing property can be achieved using silica fume as mineral admixture. In addition to the healing property, incorporating silica fume reduces the consumption of cement, thereby reducing the air pollution caused by the cement industries as well as resulting in the production of eco-friendly concrete.

Methodological Approaches to 3D Pore Structure Exploration in Cementitious Materials

2012 ◽  
Vol 517 ◽  
pp. 305-314 ◽  
Author(s):  
Piet Stroeven ◽  
L.B Nghi Le ◽  
Huan He
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Blended Cement ◽  
Cementitious Materials ◽  
Quantitative Image Analysis ◽  
Mineral Admixture ◽  
Strength Development ◽  
Cement Production ◽  
Quantitative Image ◽  
3D Information

About 6% of global CO2 emissions are due to cement production. Blending of Portland cement with a significant fraction of mineral admixture could therefore be instrumental in reducing such emissions. Use of an admixture of vegetable origin such as rice husk as will additionally contribute to waste management and its incineration produces energy. This paper will stress the importance of properly designing such blends. Preferably gap-graded concepts should be employed, since blending efficiency in terms of strength development is promoted as shown in earlier publications. The paper therefore only briefly covers these aspects. Assessment of this blending concept on durability of cementitious materials constitutes a far more complicated problem. This requires careful porosimetry. Mostly, this problem is approached by MIP or by quantitative image analysis. Both can provide 3D information, although that of MIP is generally significantly biased. Quantitative image analysis is however time-consuming and laborious, and thus expensive. Moreover, it does not provide information on continuity of pores. Present day computer facilities offer therefore a better alternative. When using a proper DEM system, the concrete can be simulated in a realistic way. The paper describes new methods for investigating the pore structure in virtual concrete and presents some data on pure cement and blended cement. Differences will have impact on durability risks.

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