Study On Basic Mechanical Properties Of Alkali-Activated Slag Cementitious Material Block Masonry

Alkali-activated slag cementitious material has the characteristics of fast hardening,early strength,high strength and high temperature resistance.The shrinkage of alkali-activated slag cementitious material is 3⁵ times that of ordinary Portland cement,it is easy to crack during the forming process,which limited the engineering application.It is assumed that the shrinkage of alkali-activated slag cementing material can be reduced if there is no shrinkage filler in the alkali-activated slag cementing material.The alkali activated slag cementitious material is mixed with ceramsite and pottery sand to produce alkali activated slag mortar and alkali activated slag ceramsite concrete hollow block.And the alkali-activated slag ceramsite concrete block masonry was made with alkali-activated slag paste or alkali-activated slag mortar with pottery sand.The compressive strength of alkali-activated slag paste is between Mb25^Mb130,compressive strength of alkali-activated slag mortar with pottery sand strength is between Mb15^Mb90,which were higher than that of Mb7.5^Mb20 for the mixed mortar and cement mortar.Therefore,the mechanical properties of alkali-activated slag ceramsite concrete block masonry should have its own new features.This paper was carried out as the following work:?1?In order to investigate the workability,mechanical performance and drying shrinkage of alkali-activated slag paste and alkali-activated slag mortar with pottery sand,the effects of water to slag ratio,sodium silicate modulus,Na₂O content,Na₂CO₃/NaOH?mass ratio of Na₂CO₃ to NaOH?and sand to slag ratio on the properties of alkali-activated slag paste and mortar.By means of XRD,FTIR,SEM-EDS and MIP analysis,the hydration products and pore size distribution of alkali-activated slag paste were obtained.For the waterglass activated slag pastes and mortars,the fluidity increased as the silicate modulus increased.When the Na₂O content was between 6%and 10%,the compressive strength and the fluidity were highest at Na₂O content of 8%,the drying shrinkage increased as the silicate modulus increased.For the Na₂CO₃-NaOH activated slag pastes and mortars,the setting time increased with an increase of Na₂CO₃/NaOH.The late compressive strength increased as the Na₂CO₃/NaOH increased.When Na₂O content was 4%,the drying shrinkage increased with the increase of Na₂CO₃/NaOH,but when Na₂O content was 6%and 8%,the addition of Na₂CO₃ can effectively reduce the drying shrinkage.?2?In order to study the axial compression performance of alkali activated slag ceramsite concrete masonry,60 masonry specimens of the alkali-activated slag ceramsite concrete hollow block at MU7.5^MU20 as well as alkali-activated slag mortar with pottery sand at Mb20^Mb60,and 66 masonry specimens of the alkali-activated slag ceramsite concrete solid brick at MU25 and MU30 as well as alkali-activated slag mortar with pottery sand at Mb15^Mb60 were tested.Based on the experimental results,the full stress strain relationship curve equation of this new type of masonry is proposed.Based on the calculation formula of axial compressive strength for ordinary masonry,by introducing the characteristic coefficient of alkali-activated slag mortar with pottery sand and adjusting the correction coefficient of the axial compressive strength for mortar,a formula for the axial compressive strength of the alkali-activated slag ceramsite concrete masonry was proposed.The formulas for calculating the peak strain,the ultimate strain and the elastic modulus of the new masonry are established.?3?To investigate the shear performance of alkali-activated slag ceramsite concrete hollow block masonry,108 masonry prisms with Mb25^Mb130 of alkali-activated slag paste and Mb25^Mb80 of alkali-activated slag mortar with pottery sand were carried out.The experimental results show that the shear strength of masonry increased as the compressive strength of alkali-activated slag paste and mortar increased.The effects of water to cementitious materials ratios,Na₂O contents and sand to cementitious materials ratios on the shear strength of masonry should not be ignored.The shear strength of masonry with alkali-activated slag mortars was higher than that with alkali-activated slag paste.Based on the experimental results,the formulae for the shear strength of alkali-activated slag ceramsite concrete hollow block masonry with alkali-activated slag pastes and mortars were developed,respectively.?4?In order to investigate the axial tensile strength of the masonry with alkali-activated slag mortar with pottery sand,60 hollow block masonry specimens with Mb20^Mb65 of alkali-activated slag mortar with pottery sand was completed.The experimental results show that the axial tensile strength of hollow block masonry with alkali-activated slag mortar with pottery sand was lower than the ordinary masonry.Based on the water to cementitious material ratio,sand to cementitious material ratio,Na₂O content,silicate modulus and the compressive strength of alkali-activated slag mortar with pottery sand,the calculation formula of the axial tensile strength of hollow block masonry was established.?5?To study the bending tensile performance of alkali-activated slag ceramsite concrete hollow block masonry,108 masonry specimens with Mb25^Mb90 of alkali-activated slag mortar with pottery sand were carried out.It was found that the bending tensile strength of alkali-activated slag ceramsite concrete hollow block masonry was not only related to the compressive strength of alkali-activated slag mortar with pottery sand,but also affected by the factors of water to cementitious material ratio,sand to cementitious material ratio,Na₂O content and silicate modulus.Based on the experimental results,the formulae for the bending tensile strengths of alkali-activated slag ceramsite concrete hollow block masonry along straight joint and slot joint were developed,respectively.