• Spent coffee grounds (SCG) leach organic compounds that hinder the hydration reaction and compressive strength of concrete.
• SCG pyrolysed at 350 and 500 °C show strong bond formation with the cement matrix.
• 15 vol% replacement of sand with pyrolysed SCG at 350 °C provides ∼30% improvement in concrete strength.
• Spent coffee grounds (SCG) leach organic compounds that hinder the hydration reaction and compressive strength of concrete.
• SCG pyrolysed at 350 and 500 °C show strong bond formation with the cement matrix.
• 15 vol% replacement of sand with pyrolysed SCG at 350 °C provides ∼30% improvement in concrete strength.