Sustainable Concrete with Rice Husk Ash (RHA) for Marine Structures

Francisco A Martinez Urtecho,José U Rodriguez Barboza,Luis J Oyanguren Gallo,Elsa Carrera Cabrera,C Chastre,P Mendonça

doi:10.1051/matecconf/201930305002

Francisco A Martinez Urtecho, José U Rodriguez Barboza + Show 4 more

Open Access

https://doi.org/10.1051/matecconf/201930305002

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Abstract

In recent years, attention has focused on addressing the environmental problems caused by the use of construction materials, proposing to develop new environmentally friendly concrete; One of the alternatives that has emerged is to replace cement or aggregates with agricultural waste because its treatment is expensive and not very sustainable; This is the case of rice husk ash (RHA), the main agricultural residue resulting from this cereal, which represents an abundant production worldwide. Marine reinforced concrete structures are in constant exposure to the marine environment, so that their structural capacity and useful life are affected by the breakdown of aggregates, which cause a greater amount of free CaO and MgO in concrete mixtures, and the penetration of chloride ions, which destroy the passive layer of steel and produce cracks in the concrete that cause loss of load and structural damage. In this investigation, cylindrical specimens of conventional concrete and sustainable concrete with cement replacement percentages of 5%, 10% and 15% RHA have been developed. The results show that for a 5% RHA replacement, the compressive strength is greater than conventional concrete at an early age; the disintegration of the aggregates decreases, being for the fine of 9.86% and for the coarse aggregate of 4.34%, the penetrability of sulfate ions decreases as the percentage of RHA replacement increases, the permeability of conventional concrete is much greater with respect to RHA replacement concrete and, finally, the unit cost analysis per cubic meter of RHA concrete is less than conventional concrete

Highlights

In recent years, environmental problems caused by the use of construction materials have been the focus of attention worldwide, with one of the most polluting being excessive cement production; According to [1] cement production has a carbon footprint of 0.8 Ton of CO2; For this reason, the use of agricultural resources is being introduced as a replacement for materials since such wastes are not very sustainable and expensive when doing some treatment
Rice husk ash (RHA) is obtained from the burning of the husk, where its evaporable components are lost during burning leaving silicates as waste; The amount of silicates is a function of the burn time and the combustion temperature
According to the results, considering conventional concrete as a standard concrete, it can be stated that the compressive strength increases as the percentage of RHA increases from 0% to 5% and from there it decreases to the value of 15%

Summary

Introduction

Environmental problems caused by the use of construction materials have been the focus of attention worldwide, with one of the most polluting being excessive cement production; According to [1] cement production has a carbon footprint of 0.8 Ton of CO2; For this reason, the use of agricultural resources is being introduced as a replacement for materials since such wastes are not very sustainable and expensive when doing some treatment. Rice husk ash (RHA) is obtained from the burning of the husk, where its evaporable components are lost during burning leaving silicates as waste; The amount of silicates is a function of the burn time and the combustion temperature. RHA is a fine material with a particle size generally less than 45 μm and an average particle size of 610 μm. This has similar characteristics to cement, starting with the high silica content, making it suitable for use as an addition; the combustion temperature range and burn time must be considered [4].

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