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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP243-10

Date: 

April 1, 2007

Author(s):

L. Coppola, P. Marcassoli, and S. Lorenzi

Publication:

Symposium Papers

Volume:

243

Abstract:

This paper deals with variability in the performances of seven different superplasticizers chosen among those of most common use belonging to the naphthalene (NSF) and polycarboxylate-based (PCE) families. In particular, compatibility of two naphthalene-based and five polycarboxylate-based admixtures with six different cements available on the Italian market was evaluated by measuring water reduction to manufacture mortars with the same workability at the end of mixing. Two different lots of the same cement (same plant) were used: lot 1 and 2 produced, respectively, on September 2005 and March 2006. Flow retention up to sixty minutes and tendency to entrap air in the mortars were measured. Results confirmed that the average water reduction and flow retention properties are better for PCE compared to NSF superplasticizers. However, experimental data confirm as performances of PCE admixtures are more strongly dependent on the cement type than those of NSF polymers. No differences were detected in terms of the air entrapped between the two superplasticizer families, except for the ACR5 superplasticizer.

DOI:

10.14359/18748


Document: 

SP243-09

Date: 

April 1, 2007

Author(s):

G.J. Kurgan, G. Crawford, J.I. Mullarky, S. Vanikar, J.M. Ruiz, and D.K. Rozycki

Publication:

Symposium Papers

Volume:

243

Abstract:

The balance between productive construction operations and a quality final product is a constant challenge facing today’s owners and contractors. In the pavement industry, innovative technologies such as the HIPERPAV® II system allow this balanced goal to be obtainable. The software is also a viable option for addressing forensic studies of premature distress. Both proactive and forensic applications are addressed through case studies in this paper. HIPERPAV® models the impact of specific construction operations, concrete mixtures, geometric design, and environmental factors on early age strength and stress development during the construction phase. These combined factors in addition to the traffic loading affect the overall long-term performance of the pavement. The first three case studies review the proactive scheduling of the sawing operations, changes that can be made to minimize the risk of high thermal stresses when a cold front is expected soon after concrete placement, and the time of concrete placement during high temperature conditions. The last case study addresses a forensic investigation where the effect of coarse aggregate type on a continuously reinforced concrete pavement (CRCP) is determined. All case studies emphasize the influence of HIPERPAV® II during the construction planning phase or the usefulness of the software in a forensic investigation.

DOI:

10.14359/18747


Document: 

SP243-08

Date: 

April 1, 2007

Author(s):

R.K. Panchalan and V. Ramakrishnan

Publication:

Symposium Papers

Volume:

243

Abstract:

This paper presents the results of an experimental investigation to determine the validity of 0.45-power chart in obtaining the optimized aggregate gradation for improving the strength characteristics of high-performance concrete (HPC). Historically, the 0.45 power chart has been used to develop uniform gradations for asphalt mixture designs; however it has now been widely used to develop uniform gradations for portland cement concrete mixture designs. Some reports have circulated in the industry that plotting the sieve opening raised to the 0.45 power may not be universally applicable for all aggregates. In this paper the validity of 0.45 power chart has been evaluated using quartzite aggregates. Aggregates of different sizes and gradations were blended to fit exactly the gradations of curves raised to 0.35, 0.40, 0.45, 0.50 and 0.55. Five mixtures, which incorporated the aggregate gradations of the five power curves, were made and tested for compressive strength and flexural strength. A control mixture was also made whose aggregate gradations did not match the straight-line gradations of the 0.45 power curve. This was achieved by using a single size aggregate and sand. The water-cement ratio and the cement content were kept constant for all the six mixtures. The results showed that the mixture incorporating the 0.45 power chart gradations gave the highest strength when compared to other power charts and the control concrete. Thus the 0.45 power curve can be adopted with confidence to obtain the densest packing of aggregates and it may be universally applicable for all aggregates.

DOI:

10.14359/18746


Document: 

SP243

Date: 

April 1, 2007

Author(s):

Editor: V.M. Malhotra

Publication:

Symposium Papers

Volume:

243

Abstract:

This publication contains the proceedings from the Ninth CANMET/ACI International Conference on Recent Advances in Concrete Technology, held in Warsaw, Poland, in May 2007. The nine papers include optimization of mixture proportions of normal, high-performance, and self-consolidating concrete; reactive powder concrete mixtures for producing thin precast elements; and efflorescence of concrete products for interlocking block pavements. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-243

DOI:

10.14359/18695


Document: 

SP243-07

Date: 

April 1, 2007

Author(s):

T.H. Liu, H.J. Chen, H.W. Liao, and C.I. Lin

Publication:

Symposium Papers

Volume:

243

Abstract:

Self-compacting concrete (SCC), characterized by the high flowability and high re-sistance to segregation, is due to the high amount of paste (including cement and mineral admixtures) in contrast with normal concrete (NC). However, the high amount of paste will limit the volume fractions of coarse aggregate and reduce the tendency of coarse aggregate to suppress drying shrinkage deformations. For this reason, SCC can be expected to produce higher values of drying shrinkage than NC. In order to assess the drying shrinkage of SCC quantitatively for application to offshore caisson foundations, the formulas presented in the literature (ACI 209 and CEB-FIP) are used to predict the values of drying shrinkage in SCC according to the cor-responding mixture proportioning. Additionally, a finite element (FE) model, which as-sumes concrete to be a homogeneous and isotropic material and follows the actual size and environmental conditions of the caisson, is utilized to simulate situations of stress distribution and deformations in the SCC caisson resulting from the drying shrinkage. The likelihood of cracking and the behavior of drying shrinkage of the SCC caisson are drawn from the analytic results calculated by the FE model proposed in this paper.

DOI:

10.14359/18745


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