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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 33 Abstracts search results
Document:
SP229-21
Date:
September 1, 2005
Author(s):
A.C.J. Evangelista, I.A.E.M. Shehata, and L.C.D. Shehata
Publication:
Symposium Papers
Volume:
229
Abstract:
Nondestructive test methods (NDT) have been used to evaluate concrete strength using curves that correlate the NDT measurements with the compressive strength of concrete established by a laboratory testing program. Usually the parameters that affect these curves are the water-cement ratio, the aggregate type, the maximum aggregate size, and the cement type of the concrete. This work presents a study on the correlations between the compressive strength of concrete and measurements from three nondestructive test methods: ultrasonic pulse velocity, probe penetration, and rebound hammer. The study included 30 different concrete mixtures made with materials used in the city of Rio de Janeiro. The compressive strength and nondestructive tests were carried out at ages of 3, 7, 14, 28, and 90 days. Analysis of variance (ANOVA) was used to investigate the importance of different parameters on the results of the compressive strength and nondestructive tests. Simple and multiple regression analyses of the obtained results lead to the proposed expressions for evaluating the compressive strength of concretes used in Rio de Janeiro from measurements using one or two nondestructive tests.
DOI:
10.14359/14745
SP229-17
V. Ramakrishnan and R.K. Panchalan
A desire to constantly upgrade the structural integrity and life of buildings and bridges has brought about new developments in the area of concrete technology. The use of corrosion free basalt fiber composite bars as reinforcement for concrete is one such innovation. This paper presents the results of an experimental investigation that was carried out for the first time anywhere in the world to evaluate the performance of concrete beams reinforced with basalt fiber composite bars. The experimentally determined ultimate moment capacities of basalt bar reinforced concrete beams were compared with the calculated ultimate moment capacities evaluated according to ACI-318 Building Code recommended design procedures. It was found that the actual ultimate moments of beams reinforced with plain basalt bars were much less than the calculated ultimate moments due to bar pullout failure. The modified basalt bars, which were provided with slots, corrugations and anchors, did not slip and the actual ultimate moments matched or exceeded the calculated moments. The bond strengths between the basalt bars (plain and modified) and concrete were also determined (ASTM C 234).
10.14359/14741
SP229-18
H.C. Lima, Jr. and J.S. Giongo
A theoretical model for steel-fiber-reinforced high strength concrete was developed and calibrated against the test results from 86 high-strength concrete columns tested under axial load. The effects of steel-fibers, the concrete compressive strength, and the transverse and longitudinal reinforcement ratio were accounted for in the proposed stress-strain model. The current model is based on the model developed by Cusson and Paultre, in which the effect of steel-fibers on the concrete ductility was incorporated using the reinforcement index of the volumetric ratio of the steel-fiber addition. The agreement between the model responses and test results was satisfactory.
10.14359/14742
SP229-19
C. Alonso, C. Andrade, E. Menendez, and E. Gayo
A concrete exposed to environments of high temperature or directly to fire undergoes microstructural changes that result in loss of mechanical properties. The present paper deals with the study of high-performance concretes (HPC) and ultra high-performance concretes (UHPC) resistance to high temperatures. Microstructural changes are followed up to temperatures of 700°C. Changes on residual permeability and porosity, together with weight losses, due to moisture, binding water, aggregates and fibre transformations, are considered. The study, performed on a wide variety of concretes, indicates that UHPC seem to be less resistant at high temperatures than HPC, but the addition of fibres improves the fire resistance of UHPC.
10.14359/14743
SP229-14
P. Castro-Borges, C. Andrade, C. Alonso, and E. Pazini Figueiredo
It has been demonstrated that the galvanic current is given by a macrocell which is formed during the curing of the repairs to a concrete member. After this time, the macrocell effect disappears giving place to a microcell behavior that lasts with time in spite of changes to the exposure conditions. This has been demonstrated for concrete containing 0.7% of chloride ion that was repaired, and where the reinforcement was primed with systems that provide protection by repassivation, inhibition, barrier or cathodic protection. However, not enough papers have been published about the electrochemical behavior of the juxtaposed regions (those in non-repaired zones but face to face to the repaired ones) after the repairs. This paper shows that repair approach, as presented here, has no adverse effects in the short and at medium term exposures to different environmental conditions.
10.14359/14738
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