Effects of biochar on cement-stabilised peat soil

Abstract

Peat is a soft soil with very high organic content, which makes it highly susceptible to extreme differential settlement. Although cement stabilisation is highly effective, it is not a common practice due to the high cost of treatment associated with large amount of binder dosage. In this paper, the use of a novel material, biochar as a potential replacement for cement and as an alternative filler to sand, was investigated. Biochar is more sustainable than traditional construction materials and has carbon sequestration ability. It could potentially be cheaper than cement or sand, depending on the source of feedstock used. Cement treated peat with sand was used as a benchmark to assess the performance of biochar enhanced cement treated peat. The samples with biochar finer than 75 µm performed better than sand equivalent, over 50 % increase in compressive strength. Furthermore, it was found that the samples with 100 kg/m 3 cement and 400 kg/m 3 biochar had comparable performance to the control sample with 200 kg/m 3 cement only, without biochar, highlighting the potential of biochar to partially replace cement. Scanning Electron Microscopy and X-ray Diffraction tests results showed that the mechanisms behind the performance gain in biochar samples are of both mechanical and chemical nature.

Stabilisation of Soft Clay, Quick Clay and Peat by Industrial By-Products and Biochars

“…Here, biochar was observed to be far more effective compared to the IBPs, with a strength increase of up to 80% for BC4. These results are similar to previous findings on peat stabilisation [27,31,95]. The stabilisation effect can possibly be attributed to the water retention (high absorption capacity) of the biochar and densification [32,96].…”

“…These results are similar to previous findings on peat stabilisation [27,31,95]. The stabilisation effect can possibly be attributed to the water retention (high absorption capacity) of the biochar and densification [32,96]. This could be a larger effect in peat with a very high water content and high porosity compared to clays with considerably lower porosity, as indicated by the water content determinations (Table 2).…”

“…[27,31,95]. The stabilisation effect can possibly be attributed to the water r absorption capacity) of the biochar and densification [32,96]. This could be in peat with a very high water content and high porosity compared to clay erably lower porosity, as indicated by the water content determinations (Ta In contrast to their positive stabilisation effect on clay, most of the IBPs effect on the strength of the peat.…”

“…Previous research has also shown that a lower liquidity index could imply a higher strength [98], but the opposite effect was observed herein as the liquidity indices were approximately 0.9-1.0 and 1.5-2.0 for the Onsøy and Tiller-Flotten clays, respectively. [27,31,95]. The stabilisation effect can possibly be attributed to the water r absorption capacity) of the biochar and densification [32,96].…”

“…It is characterised by a high porosity and large surface area and, hence, a high water-absorption capacity [26,27], and has several potential benefits, including soil fertility improvement and contaminant immobilisation [28]. Recent studies have also shown that biochar in mixtures with cement can have a positive stabilisation effect in soils [27,[29][30][31][32][33][34][35][36][37][38][39], meaning that it can be used as an alternative binder along with its carbon sequestration potential. Since 1.0 kg of biochar contains a minimum of approximately 0.75 kg of carbon (C), it can sequester over ~2.7 kg of CO 2 eq as no decomposition or erosion takes place in low permeable thick clay deposits.…”