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International Concrete Abstracts Portal

Showing 1-10 of 1698 Abstracts search results

Document: 

19-039

Date: 

January 1, 2020

Author(s):

Daniel da Silva Andrade, João Henrique da Silva Rêgo, Moisés Frías Rojas, Paulo Cesar Morais, Maria José de Souza Serafim, and Anne Neiry Lopes

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

The present study reports on the pioneering addition of rice husk ash (RHA) and silica fume (SF) into portland cement-based (PC-based) materials, combined with nanosilica (NS), aiming to assess the impact of the RHA on the mechanical and microstructure properties of ternary mixtures. Pastes were prepared to perform compressive strength tests, thermal analysis (DTA/TG), infrared spectroscopy, and mercury porosimetry. The highest reduction in the calcium hydroxide index (CH.I) and the highest calciumsilicate- hydrate (C-S-H) formation are found in the PC-based ternary mixture containing NS plus SF and NS plus RHA after 91 days of hydration. In line with the aforementioned trends, the ternary mixtures containing NS show the highest compressive strength values and reduction of mean diameter of porous. Indeed, we found strong evidence of synergistic effect in ternary mixtures incorporating NS plus RHA or SF, thus supporting their use in fabrication of cementitious materials.

DOI:

10.14359/51720291


Document: 

19-035

Date: 

January 1, 2020

Author(s):

Aravind Tankasala and Anton K. Schindler

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

In this project, the effect of using lightweight aggregate (expanded slate) on the early-age cracking tendency of mass concrete mixtures was evaluated. Concretes representative of mass concrete mixtures—namely, normal-weight concrete, internally cured concrete, sand-lightweight concrete, and all-lightweight concrete—at two different water-cementitious materials ratios (0.38 and 0.45) were tested in cracking frames from the time of setting until the onset of cracking. The development of early-age concrete stresses caused by autogenous and thermal shrinkage effects were measured from setting to cracking. The behavior of concretes containing lightweight aggregates was compared with normal-weight concrete placed under temperature conditions simulating fall placement in mass concrete applications. Increasing the amount of pre-wetted lightweight aggregates in concrete results in systematic decrease in density, reduced modulus of elasticity, and reduced coefficient of thermal expansion. All these factors effectively improve the concrete’s early-age cracking resistance in mass concrete applications.

DOI:

10.14359/51719082


Document: 

19-022

Date: 

January 1, 2020

Author(s):

A. S. Carey, I. L. Howard, D. A. Scott, R. D. Moser, J. Shannon, and A. Knizley

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

This paper evaluated constituent proportions on mechanical and thermal properties of ultra-high-performance concrete. This paper assessed how fine aggregates and fibers at varying proportions enhance cement paste and can improve its mechanical properties to a desired compressive strength, elastic modulus, or tensile strength. Approximately 400 specimens were tested for mechanical properties within four curing regimes and 22 different mixtures. These experiments aimed to add to the body of knowledge found during literature review. Past efforts found in literature have drawn conclusions by varying one ingredient at a time, whereas the current effort systematically varied multiple ingredients. Results showed compressive strength to be due to synergistic relationships between cement paste, fine aggregates, and steel fibers where absence of any ingredient reduced strength. Tensile strength and elastic modulus were dominated by a single ingredient.

DOI:

10.14359/51719076


Document: 

19-017

Date: 

January 1, 2020

Author(s):

Ying-Hua Bai, Kang Shen, Sheng Yu, and Wei Chen

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

This paper studies the effects of VAE emulsion (vinyl acetate-ethylene emulsion, containing 70 to 95% vinyl acetate) on the setting time and mechanical properties of sodium metasilicate-activated slag-fly ash cementitious materials. Sodium metasilicate is used as an activator, and the alkali equivalent (mass percentage of Na2O provided by sodium metasilicate in the cementitious material) is 8%. The content of fixed fly ash, fine slag powder, and Na2SiO3 is 30, 54.26, and 15.74 wt.%, respectively. VAE emulsion is mixed with polymer-cement ratios (mass ratio of emulsion to cementitious material) of 2.5, 5, 7.5, and 10%. The water content in the emulsion is subtracted during the mixing and measuring. In the experiment, the emulsion and the activator are stirred well before they are mixed with the powder. Research shows that C-S-H gel is the main hydration product of sodium metasilicate-activated cementitious material and adding VAE emulsion does not produce new crystal hydration products. When the VAE emulsion content is higher than 5%, some unreacted polymer particles in the slurry exists, which can improve the toughness of the mortar and prolong the setting time of the cementitious material. However, the compressive strength of the mortar decreases and the dry shrinkage rate increases. The results of hydration heat and ion dissolution experiments show that with polymer coated on the surface of sodium metasilicate particles, the dissolution rate is reduced, and the hydration heat release of the cementitious material is slowed down. In addition, the dissolution rate and dissolution amount of sodium metasilicate are reduced, which increases the setting time of the cementitious material.

DOI:

10.14359/51719080


Document: 

18-564

Date: 

January 1, 2020

Author(s):

Michał Bołtryk, Anna Krupa, and Edyta Pawluczuk

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

The paper discusses the possibilities of using ecological, organic materials such as sawdust and shavings for the production of lightweight cement composites. First, the method for determining the approximate constitution of such composites was proposed. A plan was prepared for four different assumed amounts of cement (250, 300, 350, and 400 kg/m3) of the mixture. For each quantity of cement, three series with a different total sum of components were prepared. The compressive strength test results were indicated in an equilateral triangle with the numerical values of the basic components on each side. The triangle was divided into four zones facilitating the selection a composite recipe depending on amount of cement, apparent density, and its compressive strength. Next, the production technology of blocks based on organic waste with an expanded polystyrene insert, characterized by a very low thermal conductivity (<0.15 W/m2·K [<0.026 BTU/(h·ft2·°F)]), was developed.

DOI:

10.14359/51719073


Document: 

D116-M06

Date: 

November 1, 2019

Author(s):

Helarisi Abeyruwan and Ravindra B. Herath

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Disc. 116-M10/From the January 2019 ACI Materials Journal, p. 103 Study of Temporal Change in Chloride Diffusion Coefficient of Concrete. Paper by Hongfa Yu, Yongshan Tan, and Taotao Feng


Document: 

18-514

Date: 

November 1, 2019

Author(s):

Andrés A. Torres-Acosta, Francisco Presuel-Moreno, and Carmen Andrade

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The potential use of the electrical resistivity (ρ) and the saturated electrical resistivity (ρS) for the durability design of new concrete structures and the forecasting for in-service concrete structures has been increasing in the past three decades. Many investigations have proven the ease of the method and the possibility of it being a quality control/assurance tool during construction of new concrete infrastructure. Some previous investigations even consider the ρS test a feasible one to remove other, more complicated and expensive tests used in cement-based materials as durability indicators; a few of them defined correlations between ρS and the other indexes. The present investigation uses published data to determine if empirical correlations exist between ρS and rapid chloride permeability (RCP), and between ρS and the apparent chloride diffusion coefficient (DAP). A literature search was done on the three durability indexes in question (ρS, RCP, and DAP) and some empirical equations were derived. Good empirical correlations were observed for ρS versus RCP and ρS versus DAP. The latter correlation, obtained from data of different sources, supported that ρS and chloride diffusivity follows the well-defined Einstein law of diffusion with minor modifications for cement-based materials.

DOI:

10.14359/51718057


Document: 

18-507

Date: 

November 1, 2019

Author(s):

Saranya P, Praveen Nagarajan, and A. P. Shashikala

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Development of geopolymer concrete (GPC) with industrial by-products is a solution to the disposal of the industrial wastes, thus making the concreting process sustainable. This paper focuses on the development of GPC using ground-granulated blast-furnace slag (GGBS) and dolomite (by-product from rock crushing plant) as source materials. Strength properties of slag-based GPC are studied with different proportions of dolomite. It is observed that the addition of dolomite into slag-based GPC reduces the setting time, enhances workability, and rapidly improves the early-age strength. Addition of dolomite into slag GPC also improves the durability properties, such as high resistance towards water absorption, sorptivity, marine attack, and chemical attack.

DOI:

10.14359/51716981


Document: 

18-440

Date: 

November 1, 2019

Author(s):

Arturo D’Alessandro, David J. Corr, and Surendra P. Shah

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Ferrocement is a construction material that (in comparison to traditional reinforced concrete) provides superior crack control, impact resistance, and toughness. However, while extensive literature exists on the deterioration mechanisms and maintenance of reinforced concrete structures, little attention has been given to the durability of ferrocement. In this study, the adoption of ethyl silicate, a newly developed nanomaterial, is investigated to improve durability of ferrocement. Such nanomaterials are expected to penetrate the cementitious matrix without changing the appearance of the surface. Once penetrated, pozzolanic behavior is displayed forming calcium silicate hydrate and consequently increasing durability and mechanical performance. Particular attention is given to the carbonation-induced corrosion of reinforcement, which should be considered a major concern in ferrocement due to the initially small diameter of the mesh wires and the thin mortar cover. Despite its importance, there is a limited amount of literature on carbonation-induced corrosion of ferrocement structural elements.

DOI:

10.14359/51716821


Document: 

18-412

Date: 

November 1, 2019

Author(s):

Zhiyong Liu, Sen Gao, Weiwei Chen, Yunsheng Zhang, and Cheng Liu

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Unlike traditional experimental testing, some procedures have been developed for the characterization of microstructures of cement-based materials. Based on the microstructure of the cement hydration model obtained from a digital image-based model, the parameters of pore structure were in-place continuously determined by CEMHYD3D. The characteristic parameters of pore include total porosity, the continuous pore, isolated pore, dead-end pore, connectivity, pore size distribution, specific surface area, and tortuosity. According to the combustion algorithm, the three-dimensional (3-D) voxel-erosion method, the mercury intrusion porosimetry simulation, the continuous PSD algorithm, and the random walk algorithm, the physical models are developed into program to obtain the characteristic parameters of pore structure evolution. The results show that the dead-end pores and the isolated pores begin to decrease after the continuous pores disappear. The pore size distribution of the pore structure is calculated with finer resolution. The water-cement ratio (w/c) and hydration degree have a significant effect on the specific surface area of the pores. With the increase of the degree of hydration, the tortuosity of the pore structure increases gradually. Finally, the simulation results are compared to the experimental values and the literature data that have a good agreement.

DOI:

10.14359/51716978


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