Study on Basic Mechanical Properties of Alkali-Activated Slag Cementitious Material Block Masonry

Author:Jiao Zhen Zhen

Supervisor:zheng wen zhong

Database:Doctor

Degree Year:2019

Download:108

Pages:167

Size:12083K

Keyword:

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 Mb25Mb130,compressive strength of alkali-activated slag mortar with pottery sand strength is between Mb15Mb90,which were higher than that of Mb7.5Mb20 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 MU7.5MU20 as well as alkali-activated slag mortar with pottery sand at Mb20Mb60,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 Mb15Mb60 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 Mb25Mb130 of alkali-activated slag paste and Mb25Mb80 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 Mb20Mb65 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 Mb25Mb90 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.