Effect of Rice Husk Ash on the Durability Properties of Concrete Subject to Aggressive Chemical Environment

Abstract

One of the most common material used for construction purpose worldwide is concrete, with its major constituent being cement. The production of this cement leads to overburden on natural resources used in its production, and its production also results in environmental pollution as CO₂ gas is constantly emitted. The construction industry is increasingly finding an alternative to the use of environmentally friendly materials in order to meet the sustainable aspect required by modern technology. Consequently, for the last two decades, the increase global warming due to the extensive use of Portland cement have raised concerns and led to the expansion of this concept of alternative cementitious materials. However, too much emphasis is given to compressive strength as a measure for quality index with little or no consideration given to durability property. The concrete can be made strong but not durable especially when it is subjected to chemical aggressive environments. The main purpose of this study was to evaluate the durability properties of concrete produced with rice husk ash as partial cement replacement and cured in H₂O, H₂SO₄ and MgSO₄ curing environment and tested at 7, 14, 21, 28, 56 and 90 days. The water-cement ratios were maintained at 0.50, with variable RHA replacement ratio which range in between 0% to 30% of cement by weight. The results show that at 28 days’ hydration period, 0% replacement shows higher strength while above 28 days 5% and 10% cement replacement with RHA shows improved strength. The result also shows an increase in compressive strength of about 1.35%, 2.11%, 2.15% for concrete samples with 10% RHA replacements than 0% replacements cured in normal environment (H₂O), H₂SO₄ and MgSO₄ respectively, at 90 days. Concrete samples made with 10% RHA replacements have high resistance to abrasion and less sorptivity than other replacements in both normal water and chemical aggressive environments at 90 days. Overall, the results showed that RHA is a highly water absorbing material, which also act as an internal curing agent concrete. The utilization of RHA in OPC production improves compressive, splitting tensile strength, flexural strength and durability of concrete. Therefore, it is recommended to be used to produce a strong, dense and durable concrete which can be used both in normal (H₂O) and chemically aggressive environments.