Silane based surface impregnants improve the surface characteristics by imparting water repellency. However, wet conditions are not suitable for their effective performance. A concrete surface impregnant consisting of stearic acid, which exhibits both hydrophobicity and hydrophilicity, along with fatty acid to further improve the repellency in wet condition was developed. Concrete specimen surface was applied with varying amounts of impregnant and the surface moisture and surrounding moisture condition were also varied during application and after the application of impregnant to determine the effectiveness of the impregnant. The specimens were subjected to salt immersion test and accelerated carbonation test to evaluate the concrete surface resistance against deteriorating agents. The impregnant was found to be effective when applied under wet condition. The apparent chloride ion diffusion coefficient was suppressed regardless of the moisture condition of the concrete surface and the environment. On the other hand, reduction in water absorption rate and carbonation rate were more pronounced when applied to wet concrete.
Natural fiber reinforced concrete can meet worldwide demand and promote sustainable development. This study aims to find out the effect of jute fiber on the mechanical properties of fresh and hardened concrete. For this purpose, cubes, cylinders and prisms were casted with two different lengths of jute fibers, i.e. 10 mm and 20 mm and five different percentage volume additions 0, 0.25, 0.50, 0.75 and 1 %. The compressive strength of jute fiber reinforced concrete was computed at 7, 28, 56 and 90 days. The split tensile and flexural strength tests was carried out at 90 days of testing. The correlation also stabilized between compressive and flexural strength of concrete. The results were noted down for different fiber length for the early and later ages of testing. The experimental data shows that adding 0.5 % jute fiber gives similar results as compared to the control mix. However, a smaller amount 0.25 % of jute fiber made the hardened properties of the concrete better. The results of the factorial analysis showed that the length and volume of the fibers have an impact on the properties of the hardened concrete. The slump value decreases with the addition of jute fiber. However, it can be maintained by using a suitable amount of super plasticizer. The correlation between compressive and flexural strength was given by fck = 7.381fct + 5.7035 with R2 value as 0.8194 and the correlation between compressive and split tensile strength was found to be fck = 7.1614ft + 6.4129 with R2 value equal to 0.6121.
This study examines the impact of deicers on the compressive strength and microstructure of concrete at ambient temperatures in sub-zero regions. After seven days of curing in plain water, concrete specimens were exposed to four types of deicer chemical solutions: sodium chloride, sodium acetate, calcium nitrate, and urea at concentrations of 3, 6 , and 9 %. The specimens were then tested for compressive strength after 14, 28, and 90 days of exposure. The compressive strength of concrete specimens exposed to sodium chloride, sodium acetate, and urea decreased proportionally with both deicer concentration and exposure duration. In contrast, the compressive strength of concrete specimens exposed to calcium nitrate solutions increased. Sodium acetate, which exhibited the most detrimental effect, reduced the compressive strength of concrete by a maximum of 30.79 % at a 9 % concentration. Conversely, exposure to calcium nitrate increased the compressive strength of concrete by 17 % at a 3 % concentration. The changes in compressive strength were attributed to the formation of new products and alterations in the microstructure morphology of the concrete due to deicer exposure, as evidenced by Field Emission – Scanning Electron Microscopy (FE-SEM) micrographs. The relative intensity of hydrated cement products in concrete specimens exposed to deicer solutions was determined through X-Ray Diffraction (XRD) analysis and compared to control concrete specimens. In conclusion, among the deicers examined, calcium nitrate was the only one found to have a positive impact on concrete compressive strength.
The objective of the proposed hybrid control system is to reduce the response of buildings against the earthquake ground motion using the relatively smaller magnitude of active control force without sacrificing performance against mild to moderate types of earthquakes.The proposed hybrid control system is composed of shape memory alloy passive dampers to reduce the earthquake-induced forces in the structure and an active mass damper to further reduce the responses of building frames. The performance of the proposed hybrid control system is investigated and compared with that of an active control system. It is shown that the theoretical/numerical result of the proposed hybrid control system is very effective in reducing the response of building frames subjected to earthquake-induced excitations. The concept is analytically investigated by numerical simulation of the proposed hybrid control in an idealized eightstory concrete building frame model.
The transfer of external loads from their source to the foundation is highly dependent on the connections present between loadbearing components within reinforced concrete (RC) structures. The reinforcement detailing at the junctions ensure proper transfer of forces and moments from one structural member to other structural member and maintain integrity of structural system. Inadequate design and detailing of connections between beam and column in framed structure cause safety hazard under the effect of lateral loading. To strengthen beamcolumn junctions in RC frame structures, jacketing of Fiber reinforced Polymer (FRP) materials is carried out but debonding of FRP materials from the surface of concrete often leads to the underutilization for strength of the FRP in many scenarios. The high cost of FRP materials, their tendency for brittle failure, and the occurrence of debonding have prompted the search for alternative materials to strengthen structural elements and connections. In the present study application of stainless-steel wire mesh (SSWM) for strengthening of RC beam-column junctions is evaluated. Specimens of beam column junctions are strengthened by bonding SSWM 40×32 in two different configurations. In one configuration, L-shaped SSWM strips are applied at two corners with enclosure of SSWM strip box while in other configuration, L-shaped SSWM strips at corners are enclosed by 45° SSWM strips from both the sides of specimen. To bond the SSWM onto the concrete surface of the beamcolumn junction, epoxy SIKADUR 30LP is utilized. One control and two SSWM strengthened specimens are subjected to monotonic load in vertical downward direction. From the loaddisplacement behaviour of specimens’ strength and ductility are compared. From the present experimental investigation, it is observed that SSWM strengthened specimens carry 14 % to 15 % higher ultimate load in comparison of control specimen. Strengthened specimens also exhibit improvement in energy absorption and ductility. Based on outcome of present study, it is recommended to use SSWM for strengthening of RC beamcolumn junctions.
December 2024
Volume - 98
Number : 12
November 2024
Volume - 98
Number : 11
October 2024
Volume - 98
Number : 10
September 2024
Volume - 98
Number : 09
August 2024
Volume - 98
Number : 08
July 2024
Volume - 98
Number : 07
June 2024
Volume - 98
Number : 06
May 2024
Volume - 98
Number : 05
April 2024
Volume - 98
Number : 04
March 2024
Volume - 98
Number : 03
February 2024
Volume - 98
Number : 02
