Preparation And Characterization Of Reactive Powder And Fiber Co-reinforced Lightweight Concrete Produced In Situ By Chemical Foaming

Lightweight aggregate concrete(LAC) has significant advantages of lightweight, high strength, promising durability, etc. It has a broad application in the long-span bridges,high-rise building, and the flexible foundation construction. In the development of modern concrete, their lightweight and high strength behaviors have become into an important characterics. Currently, some special projects have the excessive demands on the high behavior lightweight building materials, and it is very important and necessary to further improve the performance of the lightweight & high-strength of the LAC products.Based on the LAC specimens with foam formed in situ(which being abbrievated as FLAC), this paper aimed to improve the performance of FLAC specimens by both ways.Firstly, the FLAC specimens have prepared using the method of enhancement with short polypropylene fiber(PF). Secondly, the SPF enhanced FLAC(abbrievated as SFLAC)specimens have further improved by the method of using reactive powder(of silica fume and fine quartz powder) as additive mixtures.In the investigation of the preparation and characterization for SFLAC specimens, it was found that the adding of suitable amount of PF could improve the mechanical and practical properties of resulting PFLAC specimens. Their properties were elevated with the increase of amount of SPF, and it concluded the increased strength(especially the splitting tensile strength) and specific strength, as soon as the deceased water sbsorption and shrinkage. As the adding amount of PF being 2kg per cubic meter of PFLAC, the resulting PFLAC specimen had the 28 d compressive strength of 17.9 MPa, the 28 d splitting tensile strength of 2.27 MPa, the water absorption of 10.2%, and dry shrinkage of 377?10-6(this value being decreased by 10% as compared with the resulting FLAC specimen, namely without SPF)As the reactive powder(RP) of silica fume was used to further promote the properties of PFLAC specimen with PF adding amount of 2kg/m3, in the adding amount range of RP be ? 8%, the specific strength and splitting tensile strength of resulting PFLAC specimens were increased with the adding amount of RP, and their thermal conducting coefficients were reduced with the increase of adding amount of RP, whereas their properties of water absorption and dry shrinkage were changed less with the increase of adding amount of RP.As the silica fume adding amount being 8%, the resulting LAC specimen had the bulkdensity of 1041 kg/m3, the 28 d splitting strength of 1.83 MPa, the specific strength of19.1 ? 10-3 MPa ? m3/kg(this value being increased by 18% as compared with that of resulting PFLAC specimen without silica fume).As the silica fume was replaced by fine quartz powder to act as the RP at the same adding amount rage of being ?8%, the bulk density and mechanical strength(28 d compressive strength and 28 d splitting tensile strength) were increased with the increase of RP amount for the resulting PFLAC specimens, and their specific strength were increased less with the increase of RP amount, whereas their water sborption and dry shrinkage were decreased with the increase of RP adding amount. As the fine quartz powder adding amount being 8%, the resulting PFLAC specimen had the specific strength being 16.9×10-3 MPa ? m3/kg, the 28 d compressive strength being 18.9 MPa, the 28 d splitting tensile strength being 1.9 MPa, the water absorption being 10%, and the dry shrinkage being 411 ? 10-6. The above mentioned investigating results verified that the suitable amounts PF and RP(silica fume and fine quarts powder) can improve the comprehensive properties of LAC specimens with foam formed in situ.