Corrosion Inhibitors for Reinforced Concrete: A Review

The objective of the topic is to review the recent trends in corrosion inhibitors for reinforced concrete and their application in the laboratory and field conditions. Inhibitors are chemical substances which when added to the concrete in small concentrations will inhibit or prolong the time to initiation of corrosion in concrete structures. This chapter focuses on the type of inhibitors used in concrete based upon their mode of action and the way of application. The section deals with anodic, cathodic, mixed inhibitors; performance of admixed inhibitor vs. migrating/surface applied inhibitor and their evaluation studies; and electrochemical injection of corrosion inhibitor (EICI) in concrete and electrochemical chloride extraction techniques has been reviewed

Stress Corrosion Behavior of Ungrouted Pretensioned Concrete Beams

Prestressed concrete beams of size 150 × 150 × 1000 mm were designed, and two bonded cold-drawn 7 mm steel wires were stressed at 70% UTS under service conditions before concreting. The beams were cast with M40 grade concrete mix with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of cement and cured for 28 days. After 28 days, the stretching forces were released, the prestressing steel wire was allowed to regain its original length, the tensile stresses were transformed into a compressive stress in the concrete, and the stress corrosion behavior was assessed. Stress corrosion cracking (SCC) is due to the simultaneous action of stress, corrosive media, and material properties. The stress corrosion behavior of ungrouted pretensioned steel was assessed by using various electrochemical techniques such as electrochemical noise, open-circuit potential measurement, AC impedance, and potentiodynamic polarization measurements. The same experiments were conducted for rebars embedded in the concrete beam with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of chloride. After 30 days of exposure, the beams were tested for their flexural strength measurements to find out the load-bearing capacity

Strength and Durability Performance of Alkali-Activated Rice Husk Ash Geopolymer Mortar

This paper describes the experimental investigation carried out to develop the geopolymer concrete based on alkali-activated rice husk ash (RHA) by sodium hydroxide with sodium silicate. Effect on method of curing and concentration of NaOH on compressive strength as well as the optimum mix proportion of geopolymer mortar was investigated. It is possible to achieve compressive strengths of 31 N/mm2 and 45 N/mm2, respectively for the 10 M alkali-activated geopolymer mortar after 7 and 28 days of casting when cured for 24 hours at 60°C. Results indicated that the increase in curing period and concentration of alkali activator increased the compressive strength. Durability studies were carried out in acid and sulfate media such as H2SO4, HCl, Na2SO4, and MgSO4 environments and found that geopolymer concrete showed very less weight loss when compared to steam-cured mortar specimens. In addition, fluorescent optical microscopy and X-ray diffraction (XRD) studies have shown the formation of new peaks and enhanced the polymerization reaction which is responsible for strength development and hence RHA has great potential as a substitute for ordinary Portland cement concrete

Microstructure Characteristics of Fly Ash Concrete with Rice Husk Ash and Lime Stone Powder

Abstract Industrial wastes and recycled materials are being utilized in the construction industry for preserving the environment, saving of materials, and enhancing durability of the construction material. Blending of cement with supplementary cementitious materials like fly ash, rice husk ash, and silica fume makes concrete more durable. The main objective of this study is to make use of the rice husk ash and lime powder (LP) as a replacement of Portland pozzolana cement considering various replacement levels. The engineering and durability performance in concrete with LP were performed through compressive strength and void measurement. The microstructure in the concrete with LP was characterized through XRD, SEM/EDS, and TG/DTA. Optimum replacement ratio for rice husk ash and LP were obtained through pozzolanic reaction based CSH formation

Standardization, Calibration, and Evaluation of Tantalum-Nano rGO-SnO2 Composite as a Possible Candidate Material in Humidity Sensors

The present study focuses the development and the evaluation of humidity sensors based on reduced graphene oxide—tin oxide (rGO-SnO2) nanocomposites, synthesized by a simple redox reaction between GO and SnCl2. The physico-chemical characteristics of the nanocomposites were analyzed by XRD, TEM, FTIR, and Raman spectroscopy. The formation of SnO2 crystal phase was observed through XRD. The SnO2 crystal phase anchoring to the graphene sheet was confirmed through TEM images. For the preparation of the sensors, tantalum substrates were coated with the sensing material. The sensitivity of the fabricated sensor was studied by varying the relative humidity (RH) from 11% to 95% over a period of 30 days. The dependence of the impedance and of the capacitance with RH of the sensor was measured with varying frequency ranging from 1 kHz to 100 Hz. The long-term stability of the sensor was measured at 95% RH over a period of 30 days. The results proved that rGO-SnO2 nanocomposites are an ideal conducting material for humidity sensors due to their high sensitivity, rapid response and recovery times, as well as their good long-term stability

Comparative Study of Strength and Corrosion Resistant Properties of Plain and Blended Cement Concrete Types

The relative performances of mechanical, permeability, and corrosion resistance properties of different concrete types were compared. Concrete types were made from ordinary Portland cement (OPC), Portland pozzolana cement (PPC), and Portland slag cement (PSC). Compressive strength test, effective porosity test, coefficient of water absorption, short-term accelerated impressed voltage test, and rapid chloride permeability test (RCPT) were conducted on M30 and M40 grades of concrete designed with OPC, PPC, and PSC cements for 28- and 90-day cured concrete types. Long-term studies such as microcell and electrochemical evaluation were carried out to understand the corrosion behaviour of rebar embedded in different concrete types. Better corrosion resistant properties were observed for PSC concrete by showing a minimum current flow, lowest free chloride contents, and lesser porosity. Besides, PSC concrete has shown less coefficient of water absorption, chloride diffusion coefficient (CDC), and lower corrosion rate and thereby the time taken for initiation of crack extended