Experimental Study on Alkali Activated Slag Concrete Mixes by Incorporating PS Ball as Fine Aggregate

Abstract

Improved road connectivity is essential for any country to progress. Well designed and constructed concrete pavements are essential for the development of sustainable highway infrastructure. The increase in infrastructure and urban development activities desire to discover sustainable materials, replacing the natural raw materials required for concrete production. The higher demand for concrete roads and other construction projects has increased Ordinary Portland Cement (OPC) production. However, cement production is associated with environmental issues such as a higher carbon footprint, highly energy-intensive, and exploitation of natural resources. Cement production uses a significant amount of natural resources. Nearly 2tonnes of raw material required to produce 1ton of cement, which emits 850kg of carbon-di-oxide into the atmosphere. The present research community is focusing on developing alternative binders to minimize the production of OPC. Alkali Activated Binders (AABs) such as Alkali Activated Slag (AAS), Alkali Activated Slag Fly Ash (AASF), Geopolymers, etc., can be considered as potential alternatives to OPC. Precious Slag (PS) ball is an industrial by-product obtained from Ecomaister steel beads. PS ball has been identified as an alternative to fine aggregates for concrete production. In the present study, PS ball was considered fine aggregates to evaluate the performance of in Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly Ash Concrete (AASFC). The AASC and AASFC mixes are designed to attain a minimum strength of M40 grade and compared with conventional concrete. Sodium Silicate (SS) and Sodium Hydroxide (SH) are used as the alkaline activators. The alkaline liquid to binder ratio of 0.35 was kept constant for all the mixes. The influence of SH (i.e., 8, 10, 12, and 14M) and SS to SH ratios (i.e., 1, 1.5, 2, and 2.5) on the properties of fresh and hardened concrete were analyzed. AASC mixes are prepared with 100% GGBFS as a sole binder, while AASFC mixes are prepared by mixing GGBFS and Fly ash (FA) in different proportions, i.e., 90:10, 80:20, 70:30, and 60:40. Preliminary tests were carried out to identify the optimal NaOH concentration and dosage of alkaline activators for AASC and AASFC mixes.x The fresh and hardened properties such as workability, setting time, compressive strength, split tensile strength, modulus of elasticity, flexural strength, and abrasion resistance of different concretes were evaluated as per the standard test procedure. The durability of concrete mixes was evaluated by conducting resistance to sorptivity, hydrochloric acid, sulphuric acid, nitric acid. The water absorption and Volume of Permeable Voids (VPV) were evaluated. The flexural fatigue performance of various concrete mixes was evaluated by carrying out repeated load test on beam specimens. The fatigue life data obtained were represented and analyzed using S-N curves. Probabilistic analysis of fatigue data was carried out using Weibull distribution. Survival probability analysis to predict the fatigue lives of concrete mixes with required probability of failure was carried out. The laboratory test results indicate that the incorporation of PS ball as fine aggregates in AASC and AASFC mixes improved mechanical strength. The fatigue life improved in AASC and AASFC mixes. The fatigue data of concrete mixes can be modeled by using Weibull distribution. Improved durability performance of AASC and AAFC mixes were observed. The higher water absorption and subsequent increase inVolume of Permeable Voids (VPV) was observed at the low NaOH concentration and silicate content, due to lower hydroxyl ion concentration in the activator solution. It was observed that the activator concentration has a larger influence on the mechanical properties of AASC and AASFC mixes. High sorptivity was reported for the mixes with 8M NaOH with a gradual drop in compressive strength. The permeability property of alkali activated material was dependent on total Na2O content in the activator solution. The alkali activated mix showed good resistance towards sulphate, nitrate, and chloride attacks. The AASC and AASFC mix with PS ball as fine aggregates proved to be a good concrete for pavement.