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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 27 Abstracts search results
Document:
SP303-26
Date:
June 1, 2015
Author(s):
Jens Kronemann and Klaus-Juergen Huenger
Publication:
Symposium Papers
Volume:
303
Abstract:
The knowledge of dissolution processes of aggregates and supplementary cementing materials (SCMs) in alkaline solutions can help to describe the expansion of concretes caused by alkali-silica reaction (ASR) and the effects to avoid ASR by using SCMs in more details. Therefore, dissolution experiments in alkaline solutions under different pH values and different temperatures were performed using aggregates in the original grain size and SCMs in different ratios. The concentrations of soluble silica and additionally alumina were determined by ICP-OES. The investigations showed that up to now the “best” conditions to explain the damage behavior of concrete structures are a pH value of 13 (e.g. 0.1 M KOH solution) and a temperature of 80 °C. The evaluation bases on the parameter “excess silica” which is calculated from the dissolved silica and alumina of the aggregates and the SCMs. It was demonstrated that SCMs reduce and sometimes stop the dissolution of aggregates. The efficiency of the SCMs depends on their amount and chemical composition.
DOI:
10.14359/51688146
SP303-23
Robert J. Thomas and Sulapha Peethamparan
Fiber-reinforced polymer (FRP) reinforcement for concrete has gained popularity in the past two decades due to its high strength, cyclic load resistance, and insensitivity to chloride corrosion. This paper presents the results of an experimental evaluation of FRP reinforcing bars made completely from recycled materials with two surface conditions: externally bonded helical glass rovings and lathed circumferential grooves. Tensile testing indicated that only grooved bars provided adequate bonding within concrete systems due to bond failure of the external helical rovings under tensile loading. The performance of 1.0 m (39.4 in.) hollow beams reinforced with grooved recycled bars, commercially available FRP bars, and #2 (6.4 mm or 0.25 in.) steel bars was evaluated. Recycled and commercial FRP-reinforced beams had nearly identical performance, indicating that the recycled bars are feasible for use as reinforcement in concrete, although neither FRP-reinforced beam performed as well as steel-reinforced beams.
10.14359/51688143
SP303-24
Phuong Trinh Bui, Yuko Ogawa, Naoki Doi, Kenji Kawai, and Ryoichi Sato
In the present study, the effects of porous ceramic waste aggregate (PCWA) on the mechanical properties and durability of the steam-cured fly ash concrete are investigated. The replacement ratios of fly ash were 0%, 20% and 40% by mass, and those of PCWA were 0%, 10% and 20% by volume. Three kinds of curing conditions: dried after steam curing (D-Steam), sealed after steam curing (S-Steam), and sealed curing (Sealed), were used. The experimental results show that the compressive strength of the fly ash concrete with 20% replacement of PCWA increased regardless of curing conditions, and the pore volume decreased. The autogenous shrinkage of the S-Steam cured fly ash concrete was reduced significantly by using 20% replacement of PCWA. The carbonation resistance of the D-Steam cured fly ash concrete was also improved by using 10% replacement of PCWA and 40% replacement of fly ash.
10.14359/51688144
SP303-25
Aliakbar Ramezanianpour, Ehsan Jahangiri, Babak Ahmadi, and Faramarz Moodi
Durability based design of RC structures has gained great significance in recent decades and various mathematical models have been proposed. One of the famous models was proposed by fib. The effect of local conditions on the prediction of the models is one of the most important issues. Hence, regional investigations are necessary. The Persian Gulf is one of the most aggressive regions of the world. In this study, the fib model performance was evaluated by comparison with field measurements on some marine RC structures located in this region. The results show that the parameters in the fib model did not result in good agreement with some of field data. The model parameters were modified for application to this environment. In order to do this, a laboratory study was performed and nine different concrete mixtures with various percentages of silica fume were prepared. Evaluation of the modified model results shows that the modifications produced more reliable results than the original model for this environment.
10.14359/51688145
SP303-20
C. Medina, W. Zhu, E.Asensio, I.F. Saéz del Bosque, M. Frías, and M. I. Sánchez de Rojas
The use of superplasticisers to enhance concrete properties is standard practice in concrete manufacture. The present study aimed to assess the compatibility of these admixtures with recycled construction and demolition waste (with or without lightweight materials) aggregate on some the physical and mechanical properties of the resulting concrete. The paper reports on the 0 and 50% replacement of natural coarse aggregate in a conventional concrete with mixed recycled coarse aggregate. The experimental technique used was based on the study of water absorption as well as the compressive and splitting tensile strength of such recycled concretes. The superplasticiser was found to be compatible with this type of recycled aggregate, for no decline in concrete performance was observed.
10.14359/51688140
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