Globally the emissions of carbon dioxide from anthropogenic activities are an issue regarding the future of our planet. Today the building industry is a large contributor with approximately 10 percent of the total emissions coming from energy usage in the building industry, where about 7 percent of the global CO2 emissions are connected to the cement industry. Since cement is important and today, a non-replaceable material in concrete mixture considering the mechanical properties this is considered as a problem. Concrete is essential to the building and infrastructure industry and therefore it is of great value for society. To be able to lower the impact of concrete manufacturing, different materials are investigated to replace a part of the cement. Today, alternative materials are implemented in the cement compositions to improve the environmental impact. One material commonly used is fly ash, a waste material from coal combusting industries. However, a renewable and carbon emission sinking product could have a great impact on the total emissions from concrete manufacturing. A product that could be suitable for this is biochar, a product from pyrolysis of biomass. Previous studies show properties that could be desirable in concrete manufacturing such as high specific surface area, low bulk density, low thermal conductivity, and sound-absorbing function. Also, there are studies of biochar in cementitious material with promising results. To further investigate the biochar impact on concrete this thesis is conducted. A literature review of previous studies of biochar applications and biochar addition to concrete was conducted. This is to analyse the properties of biochar and the effect of the application on the concrete properties. Also, an experimental study was conducted to further analyse the concrete and compare the findings to previous studies. In this thesis concrete with biochar ratios of 5, 8, and 10 percentages according to the weight of the cement were compared to evaluate the performance properties. This was conducted by a laboratory test where 100 mm cubes were cast and tested for their compressive strength after 28 and 56 days. Other properties which were evaluated were the workability, density, microstructure, and chemical properties. The result showed that the workability was significantly lower for concrete mixtures with biochar addition. Also, the density decreased as the ratio of biochar increased. The same happened to the compressive strength where the comparison species had a compressive strength of 72 MPa after 28 days and the sample with 10 percent had a compressive strength of 52 MPa. However, the sample with 10 percent of biochar had the highest increase of compressive strength after additional 28 days of curing. The FTIR could not show any significant changes between samples with zero biochar addition and the samples with biochar addition / Utsläpp av koldioxid är ett globalt problem som hotar framtiden för vår planet. Idag är byggindustrin en stor bidragande faktor till dessa utsläpp där omkring 10 % av de globala utsläppen kan kopplas till energiförbrukningen i byggindustrin. 7% av de globala utsläppen kommer från cementindustrin. Då cement är ett så pass viktigt material och det saknas ersättande material med samma egenskaper anses detta vara ett problem. Betong är grundläggande för bygg- och infrastrukturmarknaden och är därför viktigt för samhället. För att kunna minska påverkan av betongtillverkningen så utreds olika material för att kunna minska cementandelen i betongen.  Idag finns alternativa material som ersätter en del av cementen för att minska klimatavtrycket. Ett sådant material är flygaska, vilket är ett restmaterial från industrier. Att i stället ersätta detta med ett förnybart bio-baserat material med koldioxidsänkande egenskaper skulle kunna innebära en förbättring av de miljöpåverkande egenskaper som finns hos betongtillverkningen. En produkt som skulle kunna vara lämplig för detta är biokol vilket är en produkt från anaerob förbränning av biomassa. Tidigare studier visar att egenskaper som skulle kunna vara fördelaktiga vid betongtillverkning finns hos biokol. Dessa egenskaper är hög specifik ytarea,låg skrymdensitet, låg värmekonduktivitet och ljudabsorberande egenskaper. Det finns även tidigare studier där biokol har applicerats till betong där resultatet har varit lovande.  Detta examensarbete har skrivits för att ytterligare analysera biokolets inverkan på betongen. För att göra detta har en litteraturstudie sammanställts med tidigare studier av biokol och biokolets inverkan på betong. Detta för att analysera biokolets karaktärsdrag och vilka effekter det har på betongens egenskaper. Till detta har även en experimentell studie gjorts för att ytterligare analysera betongens beteende vid applicering av biokol och för att kunna jämföra resultat från tidigare studier. I detta examensarbete har cementet i betongen ersatts med 5, 8 och 10% biokol av cementets vikt för att kunna jämföra egenskaperna mellan de olika proverna. Detta gjordes genom ett laboratorietest där 100 mm kuber gjöts och testades för tryckhållfastheten efter 28 och 56 dagar. Andra egenskaper som kontrollerades var konsistensen, densiteten och mikrostrukturen genom FTIR test. Resultatet visade att konsistensen påverkades kraftigt då biokol adderades till betongen. Densiteten minskade desto större andel av cementet som byttes ut. Liknande resultat uppmättes för tryckhållfastheten där den minskade från 71,9 MPa för proverna utan biokol till 51,6 MPa för betongen med 10% biokol, detta efter 28 dagar. Dock så kunde det ses att den största tillväxten av hållfasthet efter ytterligare 28 dagars härdning kunde uppmätas i provet med högst andel biokol (10%). Resultatet från FTIR testet kunde inte visa några tydliga skillnader mellan proverna med och utan biokol.

Concrete is good as a construction material regarding fire and its properties regarding strength. However, the concrete expands and cracks due to fire resulting in structural damage. According to the literature the concrete usually loses its strength during and after fire exposure due to themechanical and physical changes.Concrete consists of cement, water, aggregates of different sizes, and usually some sort of plasticiser depending on its final use. Globally the concrete production releases about 4.5 billionmetric tons of carbon dioxide, which is about 8% of all the emissions of carbon dioxide in the world (Naturskyddsföreningen, 2022).The main components in cement are limestone and marlstone which are melted and turned to clinker. The clinker is mixed with sand and gypsum to make cement. Due to the high releases of carbon dioxide from the production of cement and the destruction of the environment mining of the raw materials, Sweden had a concrete-crisis in the summer of 2021, this was due to the government denied the main cement company Cementa AB to continue to mine limestone on the island of Gotland. Due to this decision new sustainable components to replace the components to produce concrete is critical. An alternative material called biochar may be suitable as a component in concrete. Biochar is a renewable product from pyrolysis of biomass. The favorable properties of biochar such as low density, high specific area and low thermal conductivity has the potential to lower the carbon footprint of concrete. This thesis evaluates the properties and performance for different biochar ratios mixed within concrete before and after exposure to fire in a furnace that followed the standard ISO 834 curve up to 650 ℃. In particular, experiments were conducted to observe how the mechanical properties (e.g., tensile and compressive strengths) are affected by exposure to fire that caused a temperature rise of up to 650 ℃. By analyzing the results from the experiments, it is seen that the workability of the concrete decreases with higher ratios of biochar due to the biochar’s water absorption properties. The compressive and tensile strength tests before fire exposure, for both aggregate and cement replaced samples, resulted in the average strength decreasing with higher ratios of biochar. Interestingly, iiithe results after fire exposure represented higher compressive strengths for both cement and aggregate replaced samples for all ratios of biochar. However, the tensile strength after fire exposure generally decreased with higher ratios of biochar. Differential scanning calorimetry and infrared spectroscopy were performed to gain an insight into the reason for the increase in compressive strength after fire exposure. Most probably, when the silica, present in the cement, was exposed to 650 °C under fire, it softened and fused the other components, which led to stronger compressive strengths.