Impact and mechanism analysis of building fires on the mechanical properties of freshly poured concrete
CHEN Libing
GUO Junhui
WANG Chao
SHI Hua
Abstract：By testing the compressive strength,hardness,pH value,chemically bound water content,hydration products,and mi-croscopic morphology of concrete at different depths after fire exposure,the effects of fire on the mechanical properties,hydration pro-cess,and microstructure of concrete were analyzed.The results showed that the strength loss of concrete after fire gradually decreased with increasing depth.The greatest strength loss occurred in the surface layer,with its strength reduced to 38%of that of normal concrete.After the depth exceeds 50 mm,the loss of compressive strength is significantly reduced.The microhardness of the surface layer was approximately 61%of that of normal concrete.After fire exposure,the pH value of concrete was slightly lower than that of normal concrete,with minimal differences observed across depths.The chemically bound water content increased with depth,remaining comparable to that of normal concrete within 150 mm from the surface.The hydration products of cement paste at different depths showed little variation,primarily consisting of dolomite and tobermorite.SEM characterization revealed that the surface layer of con-crete had low density,with numerous cracks and pores.
Keywords：building firefreshly poured concretecompressive strengthmechanism
Publication Date：2026-02-25
Online Publishing Date：2026-03-25(First online date of this platform, not the publication date of the document)
Pages：4( 72-75 )