scholarly journals Experimental Investigations on Interface between Ordinary and Lightweight Aggregate Concretes Cast at Different Times

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1664
Author(s):  
Michał Gołdyn ◽  
Tadeusz Urban
Keyword(s):  
Load Capacity ◽  
Lightweight Aggregate ◽  
Shear Plane ◽  
Adhesive Bond ◽  
Lightweight Aggregate Concrete ◽  
Experimental Investigations ◽  
Model Code ◽  
Smooth Interface ◽  
Model Code 2010 ◽  
Conservative Estimation

Experimental investigations on 12 push-off specimens with dimensions of 600 × 300 × 180 mm (200 × 180 mm shear plane) were presented. Models reflected the connection between ordinary concrete (NWC) substrate and lightweight aggregate concrete (LWAC) overlay. The main purpose of the study was to investigate behaviour of the interface between concretes cast at different times. Two different interface conditions were considered: Smooth and rough (obtained by graining). In the selected elements, additional reinforcement consisting of one ∅8 bar was injected. The elements were tested under load control. The failure of the specimens without interface reinforcement was violent and resulted from breaking of the adhesive bond. Specimens with shear reinforcement failed in a ductile manner, however, due to the low reinforcement area, the residual load capacity was much lower than the load recorded just before cracking. It was found that mechanical roughening of the surface can lead to degradation of the concrete structure. As a result, the load-carrying capacities of elements with smooth interface proved to be higher than the ultimate loads of elements with deliberately roughened contacts. Comparative analysis showed that the existing design procedures ACI 318-19, Eurocode 2, Model Code 2010, and AASHTO can lead to safe but conservative estimation of the actual resistance of the concrete interface.

Pre-Failure Deflection and Residual Load Capacity of Reinforced Lightweight Aggregate Concrete Beams under High-Cycle Fatigue

2010 ◽  
Vol 146-147 ◽  
pp. 926-936 ◽  
Author(s):  
How Ji Chen ◽  
Te Hung Liu ◽  
Chao Wei Tang
Keyword(s):  
Fatigue Testing ◽  
Load Capacity ◽  
Fatigue Behavior ◽  
Lightweight Aggregate ◽  
Fatigue Loading ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Rc Beams ◽  
Aggregate Concrete ◽  
Normal Weight Concrete

The present study experimentally investigated the pre-failure and post-fatigue behavior of reinforced concrete (RC) beams constructed with lightweight aggregate concrete (LWAC) in comparison with that constructed of normal weight concrete (NWC) of the same compressive strength (40 MPa). A total of twelve RC beams were tested under different fatigue loadings. Based on the experimental observations, the midspan total deflection measured in the fatigue testing consisted of the elastic and plastic components. The mechanismof the two deflection components developed with load cycles was different. The experimental results showed that the fatigue resistance of LWAC beams was better than that of NWC beams for the same fatigue loading levels. It was reflected in both the lower evolution of fatigue damage and the smaller growth of midspan residual deflection. After 2 million cycles, an average increase in residual load capacity of about 8% was found in the NWC beams, while that in the LWA beams remained virtually unchanged.

Performance of Fibre Reinforced Concrete Structures - Modelling of Damage and Reliability

2016 ◽  
Vol 711 ◽  
pp. 690-697
Author(s):  
Radomír Pukl ◽  
Tereza Sajdlová ◽  
Jan Červenka ◽  
Vladimir Červenka
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Construction Material ◽  
Experimental Investigations ◽  
Fibre Reinforced Concrete ◽  
Shear Cracks ◽  
Element Analysis ◽  
Steel Fibre Reinforced Concrete ◽  
Model Code ◽  
Model Code 2010

Steel fibre reinforced concrete (FRC) has higher ductility, it can save amount of convention reinforcement, labour and in consequence costs of the structure. However, broader use of SFRC as construction material is limited among others by lack of design codes. According to the previous study, reliability and safety of ordinary reinforced engineering can be verified using non-linear finite element analysis and several safety formats that are proposed in fib Model Code 2010. In the presented paper, safety formats are applied for fibre reinforced structures such as tunnel lining precast segment and individual approaches are compared. As tensile and shear cracks or compressive crushing can develop in the fibre reinforced concrete under severe conditions, the design combining numerical and experimental investigations together with safety formats is appropriate method how to obtain safe and reliable structure. Finite element method and advanced material models taking into account FRC properties such as shape of tensile softening branch, high toughness and ductility are described in the paper. Since the variability of FRC material properties is rather high, full probabilistic analysis seems to be the most appropriate format for evaluation of structural performance, reliability and safety.

On the Durability of Concrete under the Action of Ultra-Low (up to -196 °C) Technological Temperatures

2021 ◽  
Vol 887 ◽  
pp. 406-414
Author(s):  
V.N. Yarmakovsky ◽  
D. Kadiev
Keyword(s):  
Lightweight Aggregate ◽  
Normal Weight ◽  
Air Separation ◽  
Inert Gases ◽  
Lightweight Aggregate Concrete ◽  
Experimental Investigations ◽  
Cryogenic Temperatures ◽  
Aggregate Concrete ◽  
Normal Weight Concrete ◽  
Structural Lightweight Aggregate Concrete

The article presents the physical-chemical bases and as result – the technological bases of concrete resistance to ultra-low cryogenic (up to-196 °C) technical (engineering) temperatures, which is applied to the reinforced concrete structures of engineering constructions such as storage tanks for liquefied gases (in particular, liquid nitrogen and oxygen with cryogenic temperatures), as well as the enclosing structures of blocks (units) for air separation for various inert gases. The above-mentioned physical and chemical bases of concrete resistance to the ultralow cryogenic technical temperatures are developed, using the results of the analysis of modern ideas (hypotheses and theories) about the mechanism of low negative temperatures exposure on structural lightweight aggregate concrete and normal weight concrete due to the characteristics of their macro-and microstructure. The resistance of structural lightweight aggregate concrete in comparison with equal-strength normal weight concrete to the cyclic exposure of cryogenic temperatures was performed by the authors based on the results of the relevant analytical and experimental investigations. The results of these investigations are considered in the article as a modern scientific basis for the development of the main provisions for the manufacturing technology of structural lightweight aggregate concrete and normal weight concrete with high durability (frost resistance and water resistance) in conditions of cyclic exposure to cryogenic temperatures. The results of changes in strength and deformative characteristics of concrete in the process of cyclic freezing and thawing are accepted as evaluation criteria of the resistance of concrete, manufactured using the above-mentioned technologies, to such temperature exposure.

scholarly journals Experimental Investigations on Punching Shear of Flat Slabs Made from Lightweight Aggregate Concrete

2018 ◽  
Vol 64 (4) ◽  
pp. 293-306 ◽  
Author(s):  
M. Gołdyn ◽  
Ł. Krawczyk ◽  
W. Ryżyński ◽  
T. Urban
Keyword(s):  
Lightweight Concrete ◽  
Variable Parameter ◽  
Lightweight Aggregate ◽  
Reinforcement Ratio ◽  
Punching Shear ◽  
Lightweight Aggregate Concrete ◽  
Experimental Investigations ◽  
Concrete Slabs ◽  
Aggregate Concrete ◽  
Flat Slabs

Abstract In the paper the results of experimental investigations concerning flat slabs made from reinforced lightweight concrete with sintered fly ash aggregate CERTYD were presented. In the research program 6 models made in a natural scale were included. The main variable parameter was slab longitudinal reinforcement ratio. The aim of investigation was the experimental verification of efficiency of double-headed studs as punching shear reinforcement. In the existing technical approvals such kind of reinforcement was allowed only in normal concrete slabs. It was demonstrated that double-headed studs can be an effective transverse reinforcement of lightweight aggregate concrete slabs. The use of double-headed studs resulted in increase in the ultimate load from 19% to 44%, depending on the slab reinforcement ratio which ranged from 0.5% to 1.2%. The comparative analysis showed that the Eurocode 2 provisions were conservative in relation to the experimental results, which were on average 42% higher than the theoretical ones however with a very low 7% coefficient of variation.

scholarly journals Post-peak Behaviour of Composite Column Using a Ductile Lightweight Aggregate Concrete

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Mohammad Reza Hamidian ◽  
Payam Shafigh
Keyword(s):  
Load Capacity ◽  
Compressive Load ◽  
Lightweight Aggregate ◽  
Steel Tube ◽  
Normal Weight ◽  
International Standards ◽  
Lightweight Aggregate Concrete ◽  
Green Composite ◽  
Composite Column ◽  
Normal Weight Concrete

AbstractOil palm shell (OPS) concrete filled steel tube (CFT) columns are acknowledged to be a new type of sustainable composite column. In this type of column, the conventional coarse aggregate was partially replaced with OPS lightweight aggregate to provide a green composite column. This type of CFT column showed higher energy absorption and flexibility compared to CFT columns with normal weight concrete. This research studied the effect of the strength of OPS concrete on the axial compressive behaviour of CFT columns for two grades of OPS concretes. The behaviour was comparable to that of CFT columns with two grades of normal concrete. The results showed that the CFT columns with OPS concrete achieved a new post-peak behaviour. The experimental results of the axial compressive load were compared with the estimation of two international standards. EC4-1994 and ACI318-14 showed a reliable and conservative estimation of the axial load capacity of CFT columns, respectively.

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