Chemical, Mechanical, and Durability Properties of Concrete with Local Mineral Admixtures under Sulfate Environment in Northwest China

Abstract

Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment.

Effect of sea water and MgSO4 solution on the mechanical properties and durability of self-compacting mortars with fly ash/silica fume

“…Some authors studied the effect of fly ash on the resistance of concrete/mortar to sulfate attack and pointed out that using sufficient amount of fly ash, especially low-calcium or F class fly ash can effectively increase the resistance of the concrete against sulfate attack [3,[7][8][9]. Nie et al and Irassar et al [10,11] investigated that mineral admixtures such as fly ash and blast furnace slag or additional admixture cementing materials (SCM) can be used in Portland cement concrete and have been documented to improve the durability of concrete such as sulfate resistance. Sumer [12] noticed that, regardless of the fly ash type, the fly ash addition increases the resistance of the concrete to sulfate attack.…”

Effect of fly ash on the corrosion performance and structural integrity of stainless steel concrete rebars in acid rain and saline environments

“…The T American Concrete Institute defines fly ash as "the finely divided residue that results from the combustion of ground or powdered coal and that is transported by flue gases from the combustion zone to the particle removal system" [27]. The beneficial effect of FA on the corrosion performance of reinforced and bare concrete has been reported in several investigations [25,26,[28][29][30]. Through the pozzolanic reaction, fly ash transforms Ca(OH)2 from the cement hydration process into C-S-H (calcium silicate hydrate of variable stoichiometry 0.6-2.0CaO•SiO 2 •0.9-2.5H 2 O, often also incorporating partial substitution of Al for Si), as follows [25]: [31].…”

“…Papadakis has proposed a series of reactions describing the pozzolanic activity of a high-Ca fly ash with Portland cement [32]. C-S-H is more resistant than Ca(OH) 2 to attacks of aggressive species, such as sulphates and chlorides [30]. The formation of C-S-H causes a decrease in the hydration heat release, drying shrinkage, porosity and permeability of concrete [24,25].…”

Influence of Mud Content in Sand and Gravel on Water Reducer in Concrete

“…Their impacts on the mechanics and microstructures of concrete have also been explored. However, there is no report on the bonding properties of water reducers and other components of concrete, namely, sand, gravel and mud [9,10].…”