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Showing 1-10 of 404 Abstracts search results

Document: 

SP-336_02

Date: 

December 11, 2019

Author(s):

Nidhi M Modha and Pratanu Ghosh

Publication:

Symposium Papers

Volume:

336

Abstract:

In this research, a natural pozzolanic cementitious material known as zeolite is being utilized to investigate the performance of High-Performance Concrete (HPC). Several binary (cement+zeolite) and ternary (cement+zeolite+other supplementary cementitious material) based concrete mixtures including a control mixture of Ordinary Portland Cement (OPC) with water - cementitious (w/cm) ratios of 0.40 and 0.44 are cast by replacing cement with different percentage level of zeolite material. The purpose of this study is to investigate effectiveness of zeolite material by means of long term compressive strength (7 to 91 days), tensile strength, modulus of elasticity and corrosion resistance in several concrete mixtures from 7 to 28 days. The compressometer is utilized for the measurement of the modulus of elasticity and Universal Testing Machine (UTM) is utilized to measure the compressive and tensile strength of concrete. In addition, a 4-point Wenner Probe resistivity meter is tested to determine the surface electrical resistivity of concrete, which provides an indirect indication of permeability and in turn, chloride induced corrosion durability in reinforced concrete structures. Overall, zeolite based concrete mixtures with 0.40 w/cm ratio and ¾ inch aggregate size provide promising results in terms of compressive strength, tensile strength and remarkable improvement on corrosion resistance in terms of achievement of surface resistivity data.


Document: 

SP-336_05

Date: 

December 11, 2019

Author(s):

Lisa E. Burris, Prasanth Alapati, Kimberly E. Kurtis, Amir Hajibabaee, M. Tyler Ley

Publication:

Symposium Papers

Volume:

336

Abstract:

Cement production is one of the largest contributors to CO2 emissions in the U.S. One method of reducing emissions associated with concrete is through usage of alternative cements (ACMs). Some of the more common ACMs include calcium sulfoaluminate cement, calcium aluminate cement, ternary calcium aluminate-calcium sulfate-portland cements, and chemicallyactivated binders, all of which have been shown to have lower carbon footprints than ordinary portland cement (OPC). However, the durability, and more specifically, the shrinkage behavior, of these cements has not been adequately examined, and must be better understood and able to be controlled before ACM concrete can be effectively used in the field. As a first step in increase understanding of shrinkage in ACMs, this paper examines chemical, autogenous, and drying shrinkage in the ACMs listed above. Results show that, despite greater quantities of chemical shrinkage, CSA, CAC, and chemically activated fly ash binder undergo less autogenous and drying shrinkage than OPC.


Document: 

SP-336_01

Date: 

December 11, 2019

Author(s):

James Lafikes, Rouzbeh Khajehdehi, Muzai Feng, Matthew O’Reilly, David Darwin

Publication:

Symposium Papers

Volume:

336

Abstract:

Supplementary cementitious materials (SCMs) in conjunction with pre-wetted fine lightweight aggregate to provide internal curing are being increasingly used to produce high performance, low-shrinking concrete to mitigate bridge deck cracking, providing more sustainable projects with a longer service life. Additionally, the SCMs aid in concrete sustainability by reducing the amount of cement needed in these projects. This study examines the density of cracks in bridge decks in Indiana and Utah that incorporated internal curing with various combinations of portland cement and SCMs, specifically, slag cement, Class C and Class F fly ash, and silica fume, in concrete mixtures with water-cementitious material ratios ranging from 0.39 to 0.44. When compared with crack densities in low-cracking high-performance concrete (LC-HPC) and control bridge decks in Kansas, concrete mixtures with a paste content higher than 27% exhibited more cracking, regardless of the use of internal curing or SCMs. Bridge decks with paste contents below 26% that incorporate internal curing and SCMs exhibited low cracking at early ages, although additional surveys will be needed before conclusions on long term behavior can be made.


Document: 

SP-334-08

Date: 

September 30, 2019

Author(s):

Yasser Khodair, Arif Iqbal, and Mohammed Hussaini

Publication:

Symposium Papers

Volume:

334

Abstract:

This study discusses the results of an experimental program conducted to study the fresh, hardened and unrestrained shrinkage characteristics of self-consolidating concrete (SCC) using fine recycled asphalt pavement (FRAP) and high volume of supplementary cementitious materials (SCMs) including class C fly-ash (FA) and slag (S). Sixteen mixtures were prepared with different percentages of FA, S, and FRAP. SCC mixtures were divided into four groups where each group had a different percentage of FRAP replacing fine aggregate (10%, 20%, 30%, 40%) and Portland cement being replaced by different percentages of SCMs. The water to cementitious material (w/cm) ratio of 0.4 was used for SCC mixtures with a target slump flow higher than 500 mm. The flowability, deformability, filling capacity and resistance to segregation were measured to determine the fresh properties of the mixtures. Moreover, the compressive strength at 14, 28, and 90 days and split tensile strength at 28 days were determined and durability characteristics including unrestrained shrinkage up to 90 days were tested. Analysis of experimental data showed that most of the mixtures satisfied the SCC fresh properties requirements. The addition of FRAP had an adverse effect on the compressive, tensile strength and unrestrained free shrinkage of SCC mixtures.


Document: 

SP-335_08

Date: 

September 20, 2019

Author(s):

Qingxu Jin, Marisol Faraldos, Ana Bahamonde, Behnaz H. Zaribaf, and Kimberly E. Kurtis

Publication:

Symposium Papers

Volume:

335

Abstract:

Due to the ubiquity of concrete in the urban environment and the upscaling of nanomaterial production, the incorporation of nanoparticles into cementitious materials has gained increased attention. This study compares the performance of various titania (TiO2) and silica (SiO2) nanoparticles-modified coatings, including their photocatalytic performance and the quality of their adhesion to the cementitious substrates. The photocatalytic performance with respect to air purification and self-cleaning are evaluated by nitrogen oxide (NOx) and methylene blue (MB) dye photodegradation, respectively. The results show that the Portland cement (OPC)-based cementitious materials exhibit greater photocatalytic efficiency than calcium aluminate cement (CAC)-based ones. It is proposed that the superior performance is due to a greater proportion of finer porosity and the presence of high surface area calcium silicate hydrates (C-S-H) in OPC-based cementitious materials. Interactions between coatings and cementitious substrates are examined through wettability and adhesion. The results show that the inclusion of silica layer can affect the interaction of coated cementitious surface with water, as well as the bond strength between coating and cementitious substrate.


Document: 

SP-335_04

Date: 

September 20, 2019

Author(s):

Douglas Hendrix, Nabil Bassim, and Kay Wille

Publication:

Symposium Papers

Volume:

335

Abstract:

There is significant potential for the use of nanoparticles in cementitious materials, especially in ultra-high performance concrete. These nanoparticles can further increase packing density, accelerate the pozzolanic reaction or can be used to induce new properties to the material, such as air purification or self-cleaning. Little is known about the interaction mechanisms between nanoparticles in cementitious materials, including their dispersion quality. The characterization of these nanoparticles can be challenging, especially when these nanoparticles interact with cementitious materials and their reaction products during hydration. Thorough characterization of the nanoparticle system is essential to understand how to optimize mixing constituents, procedures, and parameters.


Document: 

SP336

Date: 

January 12, 2019

Author(s):

Ralf Leistikow and Kimberly Waggle Kramer

Publication:

Symposium Papers

Volume:

336

Abstract:

ACI Committees 130 and 224 sponsored and moderated two sessions at The ACI Concrete Convention and Exposition – Fall 2017, held in Anaheim, California. The objective of the sessions was to review the use of innovative mixture designs which incorporated sustainable admixtures and supplemental cementitious materials, and the effect these sustainable technologies have on the cracking performance and durability of these concretes. In particular, cracking behavior in sustainable concretes or practices for mitigation of cracking in sustainable concretes was reviewed. This information was shared based on completed research and case studies of sustainable concrete mixture designs. The learning objectives of the two sessions follow: 1) Learn about innovative mixture designs that incorporate sustainable admixtures and supplemental cementitious materials; 2) Learn about the effect these sustainable technologies have on the cracking performance and durability of these concrete mixes; 3) Gain an understanding of the cracking behavior of sustainable concrete mixtures; and 4) Learn about practices used to mitigate cracking in sustainable concrete. Twelve presentations were given, and the presenters came from all over the world. Following the sessions, some of the presenters authored papers that provided more extensive information about their research. This SP include copies of these seven research papers.


Document: 

SP327-30

Date: 

November 1, 2018

Author(s):

Trevor N. S. Billows and Ahmad Rteil

Publication:

Symposium Papers

Volume:

327

Abstract:

The current state of North America’s infrastructure system is in dire straits. The cost of repair is estimated at over $3.6 trillion in the United States alone. As an alternative to the current strengthening methods, fabric reinforced cementitious mortar (FRCM) is proposed to aid the civil engineering industry in removing the infrastructure spending gap. This research initiative set out to determine the flexural strength improvement on RC beams with different textile ratios, different fabric materials and different anchorage methods. Five full-scale (200 x 300 x 4000 mm) (8 in x 12 in x 13 ft) reinforced concrete beams (1 control, 4 strengthened) were cast and tested under monotonic four-point bending conditions. Ultimate flexural capacity, pseudo-ductility, stiffness, and failure mode were taken as performance indicators. The study found that flexural strength was improved by up 81% over the control value.


Document: 

SP327-38

Date: 

November 1, 2018

Author(s):

Cristian Sabau, Cosmin Popescu, Gabriel Sas, Thomas Blanksvärd and Björn Täljsten

Publication:

Symposium Papers

Volume:

327

Abstract:

This paper summarizes the state-of-the-art on the topic of structural wall panels strengthened using fabric reinforced cementitious matrix composites (FRCM) composites. A systematic review of the literature is carried out to identify gaps in the available literature. A database of experimental tests, relevant for structural panels, was created and used to assess the influence of parameters such as test method, fiber type and material compressive strength, on the performance of FRCM strengthening. Since experimental investigations on walls strengthened with FRCM composites is still limited and mostly focused on shear, further investigations on walls as compression members can be considered timely, especially walls with openings, which have been overlooked. Experimental tests performed by the authors on reinforced concrete walls with openings are presented and assessed relative to the complete database. It was shown that FRCM composites are suitable repair solutions when new openings need to be created in existing walls.


Document: 

SP-330-10

Date: 

September 26, 2018

Author(s):

Luigi Coppola, Denny Coffetti, and Elena Crotti

Publication:

Symposium Papers

Volume:

330

Abstract:

Since replacement of portland cement by other cementations materials is one of the main strategies to reduce the environmental impact of cementitious mixture, several innovative portland-free binders have been investigated. This paper is aimed to study a ground granulated blast furnace slag (precursor) activated with a mixture in powder form (activator) of sodium metasilicate pentahydrate, potassium hydroxide and sodium carbonate to manufacture portland-free mortars for conservation, restoration and retrofitting of existing masonry buildings and concrete structures. Several activator/precursor combinations (2%-32% by mass) were used to investigate the effect of alkali activation on the rheological, elastic and physical performances of repair mortars. The experimental data show that by changing the activator/precursor combination it is possible to “tailor” the 28-day compressive strength of the mortar. The activator dosage represents the key parameter influencing not only mechanical performance but also the hydraulic shrinkage: the higher the activator dosage, the more pronounced the mortar shrinkage. Shrinkage values for alkali-activated mortars (AAM) are significantly higher (2000 – 4000 ∙ 10-6) compared with those of cement-based mortars with the same compressive strength. Consequently, a reduction of shrinkage by means of shrinkage reducing (SRA) and/or water retention admixtures is necessary. However, although shrinkage is very high, the modulus of elasticity is about 40% lower than that of a portland cement mortar of the same strength level. On the basis of the experimental data AAMs seem to be more promising for a sustainable future in construction since the GER (Gross Energy Requirement) and GWP (Global Warming Potential) are dramatically reduced by 80 - 90% and 70 - 80%, respectively compared with traditional portland cement mortars with the same compressive strength.


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