Strength and Durability Evaluation by DEM Approach of Green Concrete Based on Gap-Graded Cement Blending

This paper discusses the particle packing background of cementitious materials. On micro-level the Portland cement and eventually the mineral admixture grains can be considered packed in the watery environment. Particularly for (super) high performance materials, the packing density can be quite significant. An economic and due to fast computer developments reliable way to study packing of the binder, is by modern discrete element modeling (DEM) approach. In this paper use is made of a concurrent algorithm-based dynamic system, HADES. Hydration is simulated based on spherical grains. Thereupon strength can be studied on the basis of packing density. For durability issues, the complex and tortuous 3D pore structure has to be investigated. This paper uses for the assessment of pore characteristics the robotics-inspired DraMuTS system. Hydrated Portland cement is compared with gap-graded rice husk ash-(RHA)-blended (green) Portland cement. Experiments on gap-graded RHA-blended PC concrete are used as reference. Packing density is shown improved by gap-graded packing. What is more spectacular are the effects of gap-grading with RHA on the pore characteristics obtained on the DEM-produced virtual materials. This paper discusses the expected positive effects on transport-based durability issues due to gap-graded packing-induced changes in the pore system

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MODERN ROUTES TO EXPLORE CONCRETE’S COMPLEX PORE SPACE

Image Analysis & Stereology ◽

10.5566/ias.v25.p75-86 ◽

2011 ◽

Vol 25 (2) ◽

pp. 75 ◽

Cited By ~ 11

Author(s):

Piet Stroeven ◽

Zhanqi Guo

Keyword(s):

Pore Space ◽

Pore Network ◽

Cementitious Materials ◽

Particle Packing ◽

Concrete Technology ◽

Network Modelling ◽

Pore Characteristics ◽

Packing Problems ◽

Wide Range ◽

Concurrent Algorithm

This paper concentrates on discrete element computer-simulation of concrete. It is argued on the basis of stochastic heterogeneity theory that modern concurrent-algorithm-based systems should be employed for the assessment of pore characteristics underlying durability performance of cementitious materials. The SPACE system was developed at Delft University of Technology for producing realistic schematizations of realcrete for a wide range of other particle packing problems, involving aggregate and fresh cement, and for the purpose of exploring characteristics in the hardened state of concrete, including of the pore network structure because of obvious durability problems. Since structure-sensitive properties are involved, schematization of reality should explicitly deal with the configuration of the cement particles in the fresh state. The paper concentrates on the stereological and mathematical morphology operations executed to acquire information on particle size, global porosity, and on distribution of porosity and of the connected pore fraction as a result of the near neighbourhood of aggregate grains. Goal is to provide information obtained along different exploration routes of concrete's pore space for setting up a pore network modelling approach. This type of methodological papers is scarce in concrete technology, if not missing at all. Technical publications that report on obtained results in our investigations are systematically referred to.

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Determination of the optimal replacement content of Portland cement by stone powder using particle packing methods and analysis of the influence of the excess water on the consistency of pastes

Revista IBRACON de Estruturas e Materiais ◽

10.1590/s1983-41952019000200002 ◽

2019 ◽

Vol 12 (2) ◽

pp. 210-232 ◽

Cited By ~ 4

Author(s):

H. F. CAMPOS ◽

T. M. S. ROCHA ◽

G. C. REUS ◽

N. S. KLEIN ◽

J. MARQUES FILHO

Keyword(s):

Portland Cement ◽

Silica Fume ◽

Packing Density ◽

Particle Packing ◽

Attractive Alternative ◽

Excess Water ◽

Stone Dust ◽

Powder Content ◽

Substitution Content

Abstract Cement is considered the basic component with the highest environmental impact in construction, in terms of CO2 emissions. As for the aggregates, the process of comminution of rocks, in addition to artificial sand, generates stone powder that ends up being stored outdoors, generating environmental damages. Thus, the replacement of cement by stone powder appears as an attractive alternative towards the sustainable concretes. In this context, the objective of this paper is to determine the maximum packing density in Portland cement, silica fume and stone dust pastes, to determine the optimal cement substitution content for the stone powder. In addition, it is intended to verify the influence of excess water on the consistency of the mixtures produced. The substitution was done in contents equal to 0%, 7%, 14% and 21% by volume and, for each content, the packing density was determined analytically by CPM model and combinations were reproduced experimentally. Excess water was checked by the mini Kantro cone test. The results showed that the higher cement substitution content of the stone powder obtained the higher packing density, experimental and analytical, and the higher workability, allowing economic and environmental advantages. Analyzing each material, the stone powder resulted in the highest packing density and silica fume is the lowest one. Therefore, finer particles resulted in lower packaging densities, due to the greater specific surface area, which demands more water. The agglomeration resulted in more empty gaps between the grains. In addition, mixtures flowability increased with the increase of the stone powder content. As the excess water is responsible for mixture lubrication, a higher packing density for a given volume of water improves the flowability.

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POROSIMETRY BY RANDOM NODE STRUCTURING IN VIRTUAL CONCRETE

Image Analysis & Stereology ◽

10.5566/ias.v31.p79-87 ◽

2012 ◽

Vol 31 (2) ◽

pp. 79 ◽

Cited By ~ 3

Author(s):

Piet Stroeven ◽

Nghi L.B. Le ◽

Lambertus J Sluys ◽

Huan He

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Pore Space ◽

Cementitious Materials ◽

Discrete Element Modeling ◽

Concurrent Algorithm ◽

Random Node ◽

Volume Measurements ◽

3D Information

Two different porosimetry methods are presented in two successive papers. Inspiration for the development came from the rapidly-exploring random tree (RRT) approach used in robotics. The novel methods are applied to virtual cementitious materials produced by a modern concurrent algorithm-based discrete element modeling system, HADES. This would render possible realistically simulating all aspects of particulate matter that influence structure-sensitive features of the pore network structure in maturing concrete, namely size, shape and dispersion of the aggregate and cement particles. Pore space is a complex tortuous entity. Practical methods conventionally applied for assessment of pore size distribution may fail or present biased information. Among them, mercury intrusion porosimetry and 2D quantitative image analysis are popular. The mathematical morphology operator “opening” can be applied to sections and even provide 3D information on pore size distribution, provided isotropy is guaranteed. However, aggregate grain surfaces lead to anisotropy in porosity. The presented methods allow exploration of pore space in the virtual material, after which pore size distribution is derived from star volume measurements. In addition to size of pores their continuity is of crucial importance for durability estimation. Double-random multiple tree structuring (DRaMuTS), introduced earlier in IA&S (Stroeven et al., 2011b) and random node structuring (RaNoS) provide such information.

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Improving Environmental Efficiency of Reverse Filling Cementitious Materials through Packing Optimization and Fiber Incorporation

Molecules ◽

10.3390/molecules26030647 ◽

2021 ◽

Vol 26 (3) ◽

pp. 647

Author(s):

Yang Liu ◽

Lou Chen ◽

Keren Zheng ◽

Qiang Yuan

Keyword(s):

Mechanical Property ◽

Silica Fume ◽

Packing Density ◽

High Performance ◽

Steel Fiber ◽

High Performance Concrete ◽

Cementitious Materials ◽

Environmental Efficiency ◽

Fiber Reinforced Concrete ◽

Filling System

To improve the environmental efficiency of the reverse filling system, three strategies aim to optimize the packing density, and the mechanical property were adopted in this study. Based on the compressive packing model (CPM), the relationship between the D50 ratio and maximum theoretical packing density for a reverse filling system with 25% and 30% superfine Portland cement was established. For comparison, silica fume and steel fiber were also added to the reverse filling system, respectively. The improvement of packing density by adjusting the D50 ratio was verified through the minimum water demand method, CPM, and modified Andreasen and Andersen (MAA) model. Compared to the reverse filling system added with 3 wt % silica fume, which possesses a comparable mechanical property with the optimized group (adjusted D50 ratio), the incorporation of steel fiber shows a more significant increase. The environmental efficiency of all the samples was quantified into five aspects through the calculation based on the mix proportion, compressive strength, and hydration degree. The comprehensive evaluation demonstrated that the optimized reverse filling system exerts a lower environmental impact and possesses a much higher cement use efficiency compared to the majority of ultra-high performance concrete (UHPC)/ ultra-high performance fiber-reinforced concrete (UHPFRC) reported in published papers.

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Study on Sulphate Resistance of Often-Used Cementitious Material of High Performance Concrete for Marine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.450-451.94 ◽

2012 ◽

Vol 450-451 ◽

pp. 94-101

Author(s):

Kun Peng Gu ◽

Cheng Qi Wang

Keyword(s):

Corrosion Resistance ◽

Portland Cement ◽

High Performance ◽

Ordinary Portland Cement ◽

High Performance Concrete ◽

Cementitious Materials ◽

Resistance Coefficient ◽

Cementitious Material ◽

Corrosion Mechanism ◽

Better Than

Corrosion resistance coefficient and expansion ratio of different cementitious materials are tested under the sulphate corrosion experimental condition, sulphate resistance of often-used cementitious material of high performance concrete for marine is studied and evaluated. The results show that sulphate resistance of portland cement is better than ordinary portland cement, and both of them are low, often-used cementitious material of high performance concrete for marine have certain sulphate resistance, which are better than ordinary portland cement and portland cement, and some of them have strong or very strong sulphate resistance. The evaluation results of the sulphate resistance of often-used cementitious material of high performance concrete for marine are not unanimous completely by corrosion resistance coefficient method and expansion rate method. Sulphate corrosion mechanism of different kinds of cementitious material is analyzed.

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Evaluation of strength of concrete on different initial exposure condition

Current Materials Science ◽

10.2174/2666145413999201224112446 ◽

2020 ◽

Vol 13 ◽

Author(s):

Sri Ram Krishna Mishra ◽

Pradeep Kumar Ghosh ◽

Manoj Kulshreshtha

Keyword(s):

Portland Cement ◽

High Strength ◽

Cementitious Materials ◽

General Purpose ◽

Supplementary Cementitious Materials ◽

Exposure Condition ◽

Portland Cement Concrete ◽

Initial Exposure ◽

Skilled Manpower ◽

Standard Practices

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

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Special Issue: Supplementary Cementitious Materials in Concrete, Part I

Materials ◽

10.3390/ma14092291 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2291

Author(s):

Alessandro P. Fantilli ◽

Daria Jóźwiak-Niedźwiedzka

Keyword(s):

Environmental Impact ◽

Portland Cement ◽

Building Materials ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Special Issue ◽

Cement Production ◽

Concrete Part

The environmental impact of the Portland cement production and the large use of cement-based building materials is a growing problem [...]

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A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽

10.3390/ma13163467 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3467

Author(s):

Ankit Kothari ◽

Karin Habermehl-Cwirzen ◽

Hans Hedlund ◽

Andrzej Cwirzen

Keyword(s):

Carbon Dioxide ◽

Portland Cement ◽

Ordinary Portland Cement ◽

Cementitious Materials ◽

Cold Climate ◽

Supplementary Cementitious Materials ◽

Short Exposure ◽

Chemical Admixtures ◽

Composite Cements ◽

Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

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Durability Study on High-Performance Fiber-Reinforced Mortar under Simulated Wastewater Pipeline Environment

Materials ◽

10.3390/ma14143781 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3781

Author(s):

Tianyu Wang ◽

Yahong Zhao ◽

Baosong Ma ◽

Cong Zeng

Keyword(s):

Mass Loss ◽

Pore Volume ◽

High Performance ◽

Mechanical Performance ◽

High Performance Concrete ◽

Cementitious Materials ◽

Economic Losses ◽

Structural Deterioration ◽

Simulated Wastewater ◽

Corrosive Environments

The acid–alkaline-inducd corrosive environments inside wastewater concrete pipelines cause concrete structural deterioration and substantial economic losses all over the world. High-performance concrete/mortar (HPC) was designed to have better resistance to corrosive environments, with enhanced service life. However, the durability of HPC in wastewater pipeline environments has rarely been studied. A high-performance mortar mixture (M) reinforced by supplemental materials (including fly ash and silica fume) and polyvinyl alcohol (PVA) fibers, together with a mortar mixture (P) consisting of cement, sand and water with similar mechanical performance, were both designed and exposed to simulated wastewater pipeline environments. The visual appearance, dimensional variation, mass loss, mechanical properties, permeable pore volume, and microstructure of the specimens were measured during the corrosion cycles. More severe deterioration was observed when the alkaline environment was introduced into the corrosion cycles. Test results showed that the M specimens had less permeable pore volume, better dimensional stability, and denser microstructure than the P specimens under acid–alkaline-induced corrosive environments. The mass-loss rates of the M specimens were 66.1–77.2% of the P specimens after 12 corrosion cycles. The compressive strength of the M specimens was 25.5–37.3% higher than the P specimens after 12 cycles under corrosive environments. Hence, the high-performance mortar examined in this study was considered superior to traditional cementitious materials for wastewater pipeline construction and rehabilitation.

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