Abstract
The durability of cement-based structures majorly depends on their resistivity to the aggressive media in the construction environment. The most aggressive ions commonly encountered in construction environment are chloride (Cl−) and sulphate (SO42−). The interactions of these ions with hydrated cement influence their durability and ultimate service life. This paper reports the experimental findings on an investigation on the diffusivity of Cl− and SO42− ions into mortars made from two mixtures: one made from ground calcined clay bricks (GB) and commercial ordinary Portland cement (OPC) and the other consisting of GB and Portland pozzolana cement (PPC). The test media were 3.5% Cl− and 1.75% SO42− solutions. For comparison, commercial OPC and PPC were also investigated. GB was blended with OPC at replacement levels of 25, 35, 45, and 50% to make OPCGB. Similar blends were also made with PPC replacement levels of 15, 20, and 25% to make PPCGB. Mortar prisms measuring 160 mm × 40 mm × 40 mm were cast at the water-to-cement ratios (w/c) of 0.40, 0.50, and 0.60 using each category of cement and cured in water for 3, 7, and 28 days. Compressive strength measurements were taken at each of the curing ages. The 28-day cured mortar prisms were subjected to compressive strength analysis and accelerated Cl− and SO42− ingress for 36 hours at 12 V. Ion profiling was done on the mortars, and diffusion coefficients of the Cl− and SO42− ions were approximated. The results showed that there was an increase in compressive strength after exposure to Cl− and SO42− ions. In addition, the ingress of Cl− and SO42− ions decreased with an increase in depth of cover. Blended cement exhibited lower Cl− and SO42− ingress than OPC. The ingress of Cl− was observed to be higher than that of SO42− ions. The ingress of Cl− and SO42− ions increased with an increase in w/c ratio. The results further showed that there was a drop in the ingress of Cl− and SO42− ions with an increase in replacement up to 35 percent for OPC. A 15 percent replacement showed a better compressive strength development compared with 20 and 25 percent replacement for PPC. Blended cement showed lower apparent diffusion coefficients (Dapp) compared with OPC. PPC, OPCGB-35, and PPCGB-15 exhibited similar performance in terms of strength development, aggressive ions ingress, and Dapp. In conclusion, it was found that the test cements, PPCGB-15 and OPCGB-35, can be used in similar tested environments as commercial PPC.
Highlights
E durability of cement-based structures majorly depends on their resistivity to the aggressive media in the construction environment. e most aggressive ions commonly encountered in construction environment are chloride (Cl− ) and sulphate (SO4 2− ). e interactions of these ions with hydrated cement influence their durability and ultimate service life. is paper reports the experimental findings on an investigation on the diffusivity of Cl− and SO4 2− ions into mortars made from two mixtures: one made from ground calcined clay bricks (GB) and commercial ordinary Portland cement (OPC) and the other consisting of GB and Portland pozzolana cement (PPC). e test media were 3.5% Cl− and 1.75% SO4 2− solutions
Commercial pozzolana was sourced from Ngurunga quarry, Athi River, Machakos County. is is a source of pozzolana for most cement manufacturers in Kenya. e OPC and PPC were obtained from the appointed distributor in ika town, while sand was obtained from commercial distributors at Ruiru
It was observed that w/c ratio greatly influenced the ultimate strength of all test cement mortars in all the days of curing. e compressive strength decreased with an increase in w/c as 0.4 > 0.5 > 0.6 for all the days. is could be attributed to increased porosity at high w/c. e w/c ratio is considered as the most important factor affecting mortar/ concrete strength. is is because it affects the porosity of the hardened paste. e flow of the mixture as well as the cohesion between paste and aggregate is affected by the quantity of water
Summary
Academic Editor: Yuanxin Zhou e durability of cement-based structures majorly depends on their resistivity to the aggressive media in the construction environment. e most aggressive ions commonly encountered in construction environment are chloride (Cl− ) and sulphate (SO4 2− ). e interactions of these ions with hydrated cement influence their durability and ultimate service life. is paper reports the experimental findings on an investigation on the diffusivity of Cl− and SO4 2− ions into mortars made from two mixtures: one made from ground calcined clay bricks (GB) and commercial ordinary Portland cement (OPC) and the other consisting of GB and Portland pozzolana cement (PPC). e test media were 3.5% Cl− and 1.75% SO4 2− solutions. Is paper reports the experimental findings on an investigation on the diffusivity of Cl− and SO4 2− ions into mortars made from two mixtures: one made from ground calcined clay bricks (GB) and commercial ordinary Portland cement (OPC) and the other consisting of GB and Portland pozzolana cement (PPC). Blended cement exhibited lower Cl− and SO4 2− ingress than OPC. E results further showed that there was a drop in the ingress of Cl− and SO4 2− ions with an increase in replacement up to 35 percent for OPC. PPC, OPCGB-35, and PPCGB-15 exhibited similar performance in terms of strength development, aggressive ions ingress, and Dapp. Ground broken bricks (GB) can be put to an economic use by blending it with OPC and Portland pozzolana cement (PPC). The test cements are subject to being degraded by aggressive agents when used in day-today construction. ese aggressive agents may include sulphates, chlorides, moisture, and carbon (IV) oxide [7]
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