Strength Development Properties of Core Specimens Taken from Structural Concrete Test Specimens Prepared All Over Japan

AbstractThis study investigated the mechanical behavior of normal strength (NS) and high strength (HS) concrete containing recycled fine aggregates (RFAs). A high slump mixing design was employed, which may be potentially used as filled structural concrete. The compressive strength, tensile strength, and elastic modulus were measured according to the RFA replacement ratio and curing time. In addition, the shrinkage strain was measured in a temperature and humidity chamber over 260 days. The compressive strength and elastic modulus of RFA concrete were approximately 70–90% of those of virgin concrete. The decreases in the compressive strength and elastic modulus for NS concrete were larger than those for HS concrete. This could be explained by the difference in failure mechanism between NS and HS concrete. The average ratio of the compressive strength at 190 days to that at 28 days was 1.15–1.3, and the ratio of the tensile strength at 190 days to that at 28 days was 1.15–1.25. These demonstrate good strength development. The ratios between the elastic modulus and compressive strength for RFA concrete were dissimilar to those for virgin concrete but similar to those for recycled coarse aggregate concrete. ACI 318-14 (Building code requirements for structural concrete and commentary, 2014) and Model Code (Fib model code for concrete structures, 2010) overestimated the elastic modulus of RFA concrete. Therefore, this study suggested an empirical expression to approximate the elastic modulus of RFA concrete. The increase in shrinkage owing to the use of RFA was at most 5–6% of the ultimate compressive strain of concrete.

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Spiritual transformation and character strength development

PsycEXTRA Dataset ◽

10.1037/e502102008-001 ◽

2008 ◽

Author(s):

Sarah A. Schnitker ◽

Justin L. Barrett ◽

Robert A. Emmons

Keyword(s):

Spiritual Transformation ◽

Strength Development ◽

Character Strength

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Improvement Of The Method Of Winter Concreting With The Use Of Heating Wires

Promyshlennoe i Grazhdanskoe Stroitel stvo ◽

10.33622/0869-7019.2019.06.51-58 ◽

2019 ◽

pp. 51-58

Keyword(s):

Harmful Effect ◽

Electric Heating ◽

Strength Development ◽

Construction Sites ◽

Dominant Position ◽

Heating Wire ◽

Hands On ◽

Basic Parameters ◽

Monolithic Structures

Long-term experience of application of a method of electric heating by heating wires of the monolithic concrete and reinforced concrete structures erected in winter conditions is analyzed. This method, developed by the author of the article, took a dominant position on the construction sites due to the simplicity and efficiency in comparison with the mass applied in those years, the method of electric heating of concrete with steel round and strip electrodes. The data on labor intensity, material and energy costs in comparison with the method of rod electric heating are presented. Step-by-step technological operations on preparatory works and electric heating of monolithic structures with the use of extensive hands-on material, which formed the basis for the development of technological regulations, supplemented by a number of new proposals to improve the technology of works, are concretized. In order to work out the optimal mode of heat treatment, the studies of the concrete thermal conductivity factor in the process of its heating and strength development were carried out. The method for calculation of the basic parameters of concrete electric heating is presented. For simplification of calculations, for a wide contingent of masters, superintendents and technical personnel, the nomogram , making it possible with sufficient accuracy under the construction conditions to calculate the necessary heating parameters, was developed. The necessity of grounding the heating wire remaining in the concrete to reduce the harmful effect of magnetic radiation from various appliances and household appliances on the human body is noted.

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