Properties of light-weight concrete congaing lightweight expanded clay aggregate differ from the ones of normal-weight concrete containing natural normal-weight aggregate. Particularly, when compared with natural normal-weight aggregate, these differences are due to lightweight aggregate being characterized by significantly lower strength and bulk weight as well as higher absorptivity. Properties of expanded clay lightweight aggregate influence the ones of light-weight concrete, too. Parameters obtained by means of Schmidt impact hammer non-destructive testing are influenced by series of factors, among others also concrete moisture. Moisture of light-weight concrete containing lightweight aggregate influences rebound number of Schmidt impact hammer. As to Schmidt impact hammer type N (2.25 Nm impact energy), rebound number on dry concrete exceeds the one on waterlogged concrete by 21 %. Correction coefficients for rebound number correction were defined taking into account moisture of light-weight concrete under testing.
This research effort aims to evaluate the mechanical properties of concrete with two aggregate type, light weight and normal weight at elevated temperatures. To understand the mechanical properties at elevated temperature, normal and light weight concrete of 60 MPa grade was exposed to temperature range 20 to 700°C under 0%, 20%, 40% load conditions and compressive strength, elastic modulus, thermal strain and transient creep at target temperature were inspected. Experimental results show that light weight concrete has higher compressive strength, although the strength of normal weight concrete degenerated more sharply than the light weight concrete at elevated temperature. Moreover, the thermal strain (0% unstressed) and total strain (20%, 40% stressed) of normal weight concrete was higher than that of light weight concrete. Loading conditions significantly influenced the mechanical properties of normal weight concrete compared to that of light weight concrete at high temperature.
To avoid the creep rupture of GFRP bar in RC members, not exceeding 20% design tensile strength (ffu)) is recommended as design limit for sustained stress level in GFRP bar in current ACI 440.1R-06 guideline. In this paper, the effects of using light weight concrete (LWC) is studied to investigate the sustained stress level in GFRP bar RC bridge decks by a parametric study. Results show that the sustained stress in GFRP bar in LWC bridge decks is in between 2.8-5.7% of ffu, while it is about 3.44-7.52% for normal weight concrete (NWC) deck.
Nowadays, one of the most essential environmental issues around the world is to deal with the scrap tire problem. Tires that are used, rejected or unwanted are classified as scrap tires and need to be managed responsibly. In this paper, the scrap tires were shredded into pieces and used to mix with normal weight concrete. Extensive laboratory tests were carried out and the focus of this paper was to characterize the mechanical and permeability properties of concrete containing scrap tires. The main parameters studied were chipped tire content and size. The results showed that the scrap-tire chips without adding special bonding agents apparently showed an even distribution in the mortar and concrete matrix. The elastic modulus, compressive and tensile strengths of scrap tire concrete in general were found lower than that of the control concrete and the differences became significant when the content and size of chipped tires in the mix were increased. Besides, the coefficients of water permeability of concrete were found to increase with increase of chipped tires in the mix.
This study presents experimentally the bond behavior of light-weight concrete specimens with grouted reinforcing bars in comparison with conventional concrete specimens. A total of (9) pull-out specimens were studied; (3) specimens of conventional concrete, (3) specimens of light-weight concrete, and other (3) specimens of grouted light-weight concrete. Two variables are adopted in this investigation: specimen width and type of concrete (conventional concrete, light-weight concrete and grouted light-weight concrete). The study contains a discussion of the general behavior of the specimens in addition to the study of the ultimate bond capacity, maximum bond stresses and the relationship between the stress and the slip for different pull-out specimens. Results show that bond strength is highest for the largest specimen size (bond strength of grouted light-weight concrete specimen with specimen width 400 mm is higher than that of the specimen with (200 mm) width by about (13.13%)). Also, bond strength is highest for the grouted light-weight concrete specimen (bond strength of grouted light-weight concrete specimen is higher than conventional concrete specimen by (11.11%)).
Concrete is a major material used in the construction of buildings and structures in the world. Gravel and sand are the major ingredients of concrete but are non-renewable natural materials. Therefore, the utilisation of palm oil clinker (POC), a solid waste generated from palm oil industry is proposed to replace natural aggregate in this research to reduce the demand for natural aggregates. One mix of ordinary concrete as control concrete; while four mix proportions of oil palm clinker concrete were obtained by replacing 25 %, 50 %, 75 %, and 100 % of gravel and sand of control concrete with coarse and fine oil palm clinker respectively by volume, with same cement content and water cement ratio. Compressive strength test was carried out of concretes with different percentages of oil palm clinker; whereas water absorption test according to respective standard, were carried out to determine the durability properties of various mixes. Based on the results obtained, the study on the effect of percentage of clinker on strength and durability properties was drawn. According to ACI classification of light weight concrete only the 100 percentage replacement can achieve the definition of light weight concrete since its density less than 1900 kg/m3 and strength larger than 17 MPa. Eventually the 25 % replacement of the normal aggregate by the OPC will improve the strength and durability of the concrete.
Nowadays lightweight concrete is used on a large scale for structural purposes and to reduce the self-weight of structures. Specific grav- ity, compressive strength, strength/weight ratio and modulus of elasticity are important factors in the mechanical behavior of structures. This work studies these properties in lightweight aggregate concrete (LWAC) and normal-weight concrete (NWC), comparing them. Spe- cific gravity was evaluated in the fresh and hardened states. Four mixture proportions were adopted to evaluate compressive strength. For each proposed mixture proportion of the two concretes, cylindrical specimens were molded and tested at ages of 3, 7 and 28 days. The modulus of elasticity of the NWC and LWAC was analyzed by static, dynamic and empirical methods. The results show a larger strength/ weight ratio for LWAC, although this concrete presented lower compressive strength.
Failure of Plain Cocrete under Combined Stresses (Axisymmetrically Triaxial Compression) : Part 2, Comparison of Normal Weight Concrete with Light Weight Concrete