Recent advancements in the use of biochar for cementitious applications: A review

TLDR: In this paper, a review placed enormous emphasis on collating information from recent studies on biochars from agro-sources used as an admixture in cement-based applications.

Abstract: With increasing population and rising demands for improved built environment, there is an expected increase in greenhouse gas emission from the construction industry. Carbon dioxide emission levels are fast approaching a tipping point which could lead to irreversible climate change. The earth's capability to neutralise the CO2 emissions through the natural carbon cycle has been overstretched. Therefore it is imperative to adopt technologies that are able to capture and sequester CO2 in order to cancel out their release from industrial activities such as the construction and building industry. This is important so that cement-based material productions' carbon footprint can be reduced drastically for a positive change to take place in the climate. Biochar holds great promise as an effective CO2 sorptive material in cement-based applications relatively similar to its conventional use for soil amendment. Actually, fragmented researches on biochar as an admixture in cementitious materials have been conducted. Based on this logic, this review placed enormous emphasis on collating information from recent studies on biochars from agro-sources used as an admixture in cement-based applications. Similarly, the review gave up-to-date knowledge about the sources of the biomass and the production processes. Conclusively, the positive effects of biochar for carbon sequestration on some properties of the various cementitious applications were highlighted.

Figures

Fig. 1 . Ef fect of biochar on air con tent of mor tar (adapted from Ref. [ 122 ]).

Fig. 2 . Ef fect of var i ous biochar on the com pres sive strength of con crete (adapted from Ref. [ 107 ]).

Table 1 Some se lected sources for bio mass pro duc tion.

Fig. 4 . SEM of biochar ob tained from wood saw dust (reused with per mis sion from Ref. [ 117 ]).

Fig. 5 . Hy dra tion prod uct for ma tion in biochar pores (a) ex ter nal view (b) in - ter nal; view (reused with per mis sion from Refs. [ 117 ]).

Fig. 3 . Ef fect of biochar size on the com pres sive strength (adapted from Ref. [ 149 ]).

Frequently asked questions

Q1. What have the authors contributed in "Recent advancements in the use of biochar for cementitious applications: a review" ?

The use of biochar has been shown to have great promise as an ef fec tive CO 2 sorp tinder this paper. 

Q2. what is the effect of biochar on the properties of ce men ti tious?

The influence of biochar on the properties of cementitious composites is strongly dependent on the thermo - chemical conversion utilised in terms of the temperature, time, the pressure used in producing the biochar. 

Q3. What is the role of biochar in cementitious composites?

biochar being a carbonaceous material can also be incorporated into cementitious composites for carbon dioxide sequestration due to its porous morphology. 

Q4. What is the effect of biochar on the construction industry?

it is anticipated that the ongoing rapid evolution in the use of biochar in cementitious composites will result in the application of biochar to improve the carbon dioxide sequestration of construction materials. 

Q5. What is the impact of biochar on cementitious composites?

Development of nano biochar: Similar to the evolution of supplementary cementitious materials such as rice husk ash, silica fume, limestone; more understanding of biochar will result in the more development of nano biochars. 

Q6. What is the impact of nano biochar on cementitious composites?

The availability of nano biochar will also create an avenue to enhance the performance of cement - based materials by replacing Portland cement with a very small volume of biochar. 

Q7. how did mo et al. use biochar as a ter nal?

Mo et al. [ 167 ] used biochar as in ter nal cur ing along side mag ne sium ox - ide to re duce au to ge nous shrink age in ce ment pastes. 

Q8. What is the effect of biochar on the flex ural strength of the tar mix?

The study by Muthukr ish nan et al. [ 43 ] also showed that the use of rice husk biochar can be used to slightly in crease the flex ural strength of mor tar mix tures in cor po rat - ing 20% rick husk ash as re place ment of the Port land ce ment. 

Q9. How much biochar can be used in a con crete mix?

Nev er the less, biochar from sources such as wood can be used up to 2% as there is only a slight re duc tion in the split ten sile strength com pared to the con trol with out biochar. 

Q10. How can the biochar be used to store wa ter?

As men tioned ear lier, the abil ity of the biochar to act as an in ter nal cur ing agent can be as cribed to its porous na ture which em bod ied it with space to store wa ter. 

Q11. How many biochars are less flam - mable?

Zhao et al. [ 103 ], re ported that when slow py rol y sis is con ducted on feed stock for biochar pro duc tion, 80% of the biochars are less flam - ma ble. 

Q12. How much biochar is used to increase the com pres sive strength?

Sim i lar to the com pres sive strength, the in cor po ra tion of biochar from wood wastes has been found to en hance the split ten sile strength of con crete up to a dosage of 0.5% [ 42 , 122 , 130 ]. 

Q13. how much CO2 is biochar used in the net green house gas emis sions?

The use of biochar has been found to re - sult in ap prox i mately 900 kg CO 2 re duc tion in the net green house gas emis sions due to the stor age and car bon cap ture of the bio mass used in pro duc ing the biochar [ 171 ].