ABOUT THE 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.

International Concrete Abstracts Portal

Showing 1-5 of 107 Abstracts search results

Document: 

19-320

Date: 

July 1, 2020

Author(s):

Bruce Menu, Thomas Jacob-Vaillancourt, Marc Jolin, and Benoit Bissonnette

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

The experimental program reported in this paper sought to evaluate the efficiency of a range of curing methods in view of minimizing the evaporation rate at the surface of freshly placed shotcrete and preventing the detrimental consequences of early-age shrinkage. CSA A23.1-14 states that severe drying conditions should be considered to exist when the surface moisture evaporation rate exceeds 0.50 kg/m2/h (0.1 lb/ft2/h). In fact, the environmental conditions that lead to such evaporation rates are regularly experienced on construction sites, requiring that adequate protection of the concrete surface be carried out in a timely manner after placement. This research effort is aimed at quantifying the influence of selected curing methods upon the early-age moisture loss and the resulting shrinkage. The results show that early-age volume change of freshly sprayed shotcrete can be significantly reduced by adequate surface protection. Among the investigated methods, moist curing is found to be the most effective.

DOI:

10.14359/51724624


Document: 

18-512

Date: 

July 1, 2020

Author(s):

Mahdi Valipour and Kamal H. Khayat

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

Ultra-high-performance concrete (UHPC) can be vulnerable to variations in materials properties and environmental conditions. In this paper, the sensitivity of UHPC to changes in mixing, casting, curing, and testing temperatures ranging between 10 and 30 ± 2°C (50 and 86 ± 3.5°F) was investigated. The investigated rheological properties, mechanical properties, and shrinkage of UHPC are shown to be significantly affected by temperature changes. UHPC made with either binary or ternary binder containing fly ash (FA) or slag cement exhibited greater robustness than mixtures prepared with 25% silica fume. UHPC made with 60% FA necessitated the lowest high-range water-reducing admixture demand. With temperature increase, the yield stress of UHPC mixtures increased by up to 55%, and plastic viscosity decreased by up to 45%. This resulted in accelerating initial and final setting times by up to 4.5 and 5 hours, respectively. The increase of temperature from 10 to 30 ± 2°C (50 ± to 86 ± 3.5°F) led to a 10 to 75% increase in compressive, splitting tensile, and flexural strengths and modulus of elasticity and 15 to 60% increase in autogenous shrinkage.

DOI:

10.14359/51724613


Document: 

19-253

Date: 

May 1, 2020

Author(s):

K. Tamanna, M. Tiznobaik, N. Banthia, and M. Shahria Alam

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

Using recycled scrap tire and construction and demolition waste as aggregates in concrete will not only facilitate an environmentally sustainable solution to solid waste disposal but also will significantly contribute to alleviating the ever-growing demand for natural aggregates in concrete production. However, only limited studies focused on the use of rubberized recycled aggregate concrete (RRAC), which lacks in-depth scrutinization of its material behavior with respect to conventional concrete. The first stage of this study is focused on investigating the effect of pre-treatment of crumb rubber (CR) with three levels of NaOH concentration on rubberized mortar specimens. The second stage consists of an experimental investigation on the mechanical behavior of concrete comprising CR and recycled concrete aggregate (RCA) each at three replacement levels of natural fine and coarse aggregates, respectively, at a water-cement ratio (w/c) of 0.34. The results indicate RRAC yields satisfactory compressive and flexural behavior for use in structural concrete.

DOI:

10.14359/51722409


Document: 

18-307

Date: 

May 1, 2020

Author(s):

M. M. Al-Zahrani, K. A. Alawi Al-Sodani, M. Maslehuddin, O. S. Baghabra Al-Amoudi, and S. U. Al-Dulaijan

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

One of several methods used to minimize reinforcement corrosion is the use of service-life prediction models to calculate mixture design and construction variables for the desired service life of a structure. Although several models are available for this purpose, very few incorporate the effect of environmental temperature on chloride diffusion. Moreover, most of the earlier studies were conducted under laboratory conditions and they are not based on actual field data. In the reported study, chloride diffusion in Type V and silica fume cement concretes was evaluated under laboratory and field conditions. Large-size concrete specimens were exposed in the tidal zone of a marine exposure site for 1, 2, 5, and 10 years while the laboratory specimens were exposed to a chloride solution maintained at 22, 35, 50, and 60°C (71.6, 95, 122, and 140°F) for 1 year. The coefficient of chloride diffusion (Da) for Type V cement concrete specimens placed in the field was noted to be much more than that of silica fume cement concrete specimens at all exposure periods. However, the Da for both Type V and silica fume cement concrete specimens decreased by 1.3 to 3 times with increasing period of exposure. The Da for the laboratory concrete specimens increased by 2.2 to 3.8 times as the exposure temperature was increased from 22 to 60°C (71.6 to 140°F). Furthermore, the Da for Type V cement concrete specimens was 2.9 to 5 times more than that of silica fume cement concrete specimens. Empirical models correlating the field and laboratory data were developed. These models could be useful for calculating the Da for field conditions from the laboratory data.

DOI:

10.14359/51724589


Document: 

18-563

Date: 

January 1, 2020

Author(s):

Hisham Qasrawi

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

Green self-consolidating concrete (SCC) is the aim of the construction industry nowadays. The accumulation of steel slag wastes causes severe environmental problems. These wastes can be recycled and replace natural aggregates, resulting in sustainable green SCC. In this research, natural aggregates in SCC are replaced, wholly or partly, by steel slag coarse aggregates (SSA) that were produced by crushing by-product boulders obtained from the steel industry. The fresh properties, (workability, stability, and bleeding), can all be attained when the suitable amount of SSA is used. SSA concrete increased the air content. Higher values are reported under hot conditions. The study shows that the 28-day compressive strength of SCC increased by approximately 10% when natural aggregate is replaced by SSA. However, adverse effects are reported when the ratio of SSA is more than 50%. Under hot weather, the strength was less and the optimum replacement ratio is 25%. The tensile strength of SCC increased by approximately 20% when natural aggregate is replaced by SSA. Adverse effects are reported when the ratio of SSA is more than 75%. Under hot weather, the same is observed but the value of the 28-day strength was lower. Special strength development mathematical relations are obtained and discussed. The modulus of elasticity increased by the increase in slag. The optimum value was at 50% for both conditions. An adverse effect is observed when the ratio of slag exceeds 75%. The drying shrinkage of concrete was lower for concrete containing SSA.

DOI:

10.14359/51719072


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.