Corn Cob Ash versus Sunflower Stalk Ash, Two Sustainable Raw Materials in an Analysis of Their Effects on the Concrete Properties.

Adrian Alexandru Șerbănoiu,Bogdan Vasile Șerbănoiu,Radu Muntean,Cătălina Mihaela Grădinaru,Nicanor Cimpoeșu

doi:10.3390/ma15030868

Adrian Alexandru Șerbănoiu, Bogdan Vasile Șerbănoiu + Show 3 more

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https://doi.org/10.3390/ma15030868

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Abstract

The increased CO2 emissions determined by the cement industry led to continuous and intensive research on the discovery of sustainable raw materials with cementitious properties. One such raw material category is agricultural waste. This study involved research on the effects of corn cob ash and sunflower stalk ash, respectively, on compressive strength measured after 28 days and 3 months, the flexural and splitting tensile strengths, the resistance to repeated freeze–thaw cycles, and on the resistance to chemical attack of hydrochloric acid of the concrete. A 2.5% and 5% replacement of the cement volume with corn cob ash (CCA) of A and B quality was applied, and with sunflower stalk ash (SSA) at A and B quality, respectively. The obtained results revealed that CCA and SSA decreased the compressive and tensile strength, but led to higher resistance of the concrete on repeated freeze–thaw cycles and to hydrochloric acid. The mixes with 2.5% SSA at A quality obtained the best results regarding splitting the tensile strength and resistance to repeated freeze–thaw cycles, the mixes with 2.5% SSA at B quality led to the highest resistance to hydrochloric acid, and those with 2.5% CCA at A quality led to the best values of compressive strength and flexural tensile strength.

Highlights

The world’s cement production has been estimated to around 4.1 billion metric tons [1]; it emitted around 2.3 gigatons of CO2 in 2019, this value being around 7% of total CO2 emissions [2], and it is expected to reach 4.83 billion metric tons in 2030 [3]
If we look at the composition of the vegetal ashes, it can be observed that Si lacks the B quality of sunflower stalk ash (SSA), Al and Fe are present only in the B quality of corn cob ash (CCA), and Ca content is a little smaller in the SSA at A and B quality and in a much smaller rate in the CCA at A and B quality
If we look to the other two elements present in cement, namely K and S, it can be observed that the K content is much higher, whereas the S content is quite similar or a little smaller in CCA and it lacks in SSA

Summary

Introduction

The world’s cement production has been estimated to around 4.1 billion metric tons [1]; it emitted around 2.3 gigatons of CO2 in 2019, this value being around 7% of total CO2 emissions [2], and it is expected to reach 4.83 billion metric tons in 2030 [3]. A solution for decreasing the CO2 emissions determined by the cement industry is its replacement by supplementary cementitious materials (SCMs). These SCMs can contribute to reduce the environmental impact and costs related to the cement and concrete industry, since they need less process heating and emit smaller CO2 levels [4], enhance sustainability, and improve some of the concrete’s properties [5]. Previous studies showed that lignocellulosic ash containing significant rates of silica and alumina can develop pozzolanic activity in the presence of calcium hydroxide, leading to improved properties of concrete [15,16]. Maize crops are cultivated mainly in China, USA, South Africa, and Eastern Europe, whereas sunflower crops are grown in southern South America, Southern Europe, South Africa, and South and European Russia [19]

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