Optimum Level of Partial Replacement of Cement with Ground Rice Husk Ash (GRHA) in Concrete

Abstract

For Rice Husk Ash (RHA) to be effective as a pozzolana, the fraction of Silica in amorphous state which exhibits high reactivity should be maximized by controlled burning. Due to practical difficulties, RHA produced in power plants and brick kilns in most parts of Sri Lanka does not contain significant fractions of amorphous Silica and thus have not shown high replacement potential of Cement in mortar or concrete. Thus, this study focussed on grinding RHA with high crystalline Silica content with the intention of producing higher reactive particle surface area to be used for partially replacing Cement in concrete. Main objective of the study was to find optimum partial replacement fraction of Cement by Ground Rice Husk Ash (GRHA) in concrete in terms of compressive strength.For the study, RHA samples from brick kilns around Anuradhapura, where higher burning temperatures are used, were collected and ground in a ball mill for a fixed duration for the transformation into GRHA with a similar fineness as Cement. Prescribed concrete mix proportions were used with Cement replaced by GRHA. Standard concrete cubes were tested for compressive strength and other related tests, such as tensile strength, permeability and heat of hydration, were conducted to check for deviations. These studies revealed that a 35% replacement of Cement by GRHA is the optimum value to satisfy relevant parameters of the prescribed concrete mix.

A Review on Partial Replacement of Cement in Concrete by Three Supplementary Materials

“…This section summarized the tensile strength of concrete made from different percentages of fly ash, RHA and lime. 0 -20 Optimum strength and workability is found nearly at 10% of replacement (Arulkumaran et al, 2019) 0 -50 35% replacement produces high strength as compared to control concrete (Shukla et al, 2011) 0 -20 Strength reduces at every % of replacement (Siddika et al, 2018) 0 -15 Strength reduces at every % of replacement (Liew et al, 2017) 0 -25 Replacing 35% produces high strength Lime (Maheswaran et al, 2011) 0 -30 Strength reduces significantly (Anbuchezian and Kumar, 2018) 0 -20 Strength progressively reduces at every % of replacement…”

“…RHA has pozzolanic properties so some attempts have been made in rice producing countries to use RHA as partial replacement of hydraulic cement in concrete. RHA provides several advantages, improved workability and durability properties in the produced mortar or concrete are notable among that (Arulkumaran et al, 2019). This material is actually a super pozzolan since it has silica about 85% to 90% (Washington et al, 2017).…”

“…This material is actually a super pozzolan since it has silica about 85% to 90% (Washington et al, 2017). Ideal level of replacement for strength and durability properties of concrete is analyzed by (Washington et al, 2017;Lee et al, 2019;Arulkumaran et al, 2019;Khan et al, 2014). After having a close look at their data it is noted that 10% to 15% replacement of cement by RHA shows positive outcome in terms of compressive, tensile and flexural strength.…”