Incorporation of bamboo charcoal for cement-based humidity adsorption material

Abstract

Abstract This paper investigates the incorporation of bamboo charcoal (BC) in cement to prepare cement-based humidity adsorption material. Cement pastes with BC were prepared and their flowability, compressive strength, drying shrinkage and humidity adsorption were measured. Pore information of hardened paste was determined by both N2 adsorption (NAD) and mercury intrusion porosimetry (MIP) analyses. Results indicate that BC decreases flowability of cement paste but favorable flowability of blended paste with BC can be provided by adjusting superplasticizer dosage. BC decreases compressive strength of hardened cement paste before 7 d while its influence on later strength depends on its particle size and replacement ratio. Specifically, BC with average size of 8 μm increases compressive strength at later ages at 10% replacement ratio. But this improvement is diminishing with the increase of either BC size or replacement ratio and adverse effects on compressive strength are found for mixtures with BC of larger size, especially at higher replacement ratios. BC of 23 μm shows little influence on drying shrinkage of mixtures while that of 8 μm significantly increases this value as replacement ratio rises. The humidity adsorption results demonstrate that BC increases the humidity adsorption capacity of cement paste and this improvement is more prominent when BC ratio is higher or BC is finer. The calculated humidity adsorption results show a favorable agreement with experimental ones with the deviation probably attributed to experiment technique limits. It is inferred that humidity adsorption promotion is mainly due to the combined effects of BC on pore volume and specific surface area of hardened paste.