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We investigated the effects of different barium compounds on the thaumasite form of sulphate attack(TSA)resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhibition mechanisms within different types of barium salts,namely BaCO_3 and Ba(OH)_2,on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%,1.0%,and 1.5% were immersed in 5%(by weight)MgSO_4 solution at 5 ℃ to mimic TSA.Appearance,mass,and compressive strength of the mortar samples were monitored and measured to assess the generaldegradation extent of these samples.The products of sulphate attack were further analyzed by XRD,FTIR,and SEM,respectively.Experimentalresults show that different degradation extent is evident in allmortars cured in MgSO_4 solution.However,barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form,which may be due to their solubility difference in alkaline cement pore solution,and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controlsamples.
We investigated the effects of different barium compounds on the thaumasite form of sulphate attack (TSA) resistance of cement-based materials when they were used as admixtures in mortars. Moreover, we analyzed the inhibition mechanisms within different types of barium salts, ie BaCO 3 and Ba (OH) _2, on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%, 1.0%, and 1.5% were immersed in 5% by weight MgSO_4 solution at 5 ℃ to mimic TSA. Appearance, mass, and compressive strength of the mortar samples were monitored and measured to assess the general severity of these samples. The products of sulphate attack were further analyzed by XRD, FTIR, and SEM, respectively. Experimental results show that different different degradation extent is evident in allmortars cured in MgSO_4 solution. Host, barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbona te form, which may be due to their solubility difference in alkaline cement pore solution, and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controls samples.