The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Vivek Bindiganavile - One of the best experts on this subject based on the ideXlab platform.
-
cellulose nanofibres cnf for Sulphate Resistance in cement based systems
Cement & Concrete Composites, 2019Co-Authors: Jose R A Goncalves, Mounir Elbakkari, Yaman Boluk, Vivek BindiganavileAbstract:Abstract Cellulose nanofibres (CNF) are employed for the first time to address Sulphate penetration and subsequent dimensional change in the cementitious system. Using four different Portland cement based binders, paste and mortar mixtures were prepared to have up to 0.5% dry CNF by volume fraction. After 28 days of moist curing, the specimens were subjected to accelerated Sulphate attack for 12 weeks. Unidirectional penetration of Sulphate was determined according to a modified ASTM C114 method. Alongside, the change in length was measured as per ASTM C 1012. The results show that CNF visibly reduces the penetration of Sulphate ions inside the cementitious system. As well, it effects a marked reduction in the Ettringite produced and the associated expansion. Of particular significance to the construction industry is that at 0.3–0.5%, CNF imparts as much Resistance to Type GU Portland cement against Sulphate attack, as the specially formulated Sulphate resistant cements.
-
evaluating Sulphate Resistance of cement based systems by Sulphate content determination after exposure
Key Engineering Materials, 2016Co-Authors: Vivek Bindiganavile, Chi Qian Ou, Zheng Chen, Yaman BolukAbstract:This paper describes approaches to evaluating the Resistance of cement-based composites to Sulphate attack. The conventional approach of evaluation by means of measuring expansion is discussed in comparison with the Sulphate diffusion, which was quantified as a function of depth. Besides CSA Types GU and HS, a 30:70 blend of fly ash and cement Type GU was also examined. The specimens so produced were immersed in a Sulphate solution as per ASTM C1012 and retrieved variously after 7, 14, 28, 56 and 84 days of exposure. As expected, Type HS cement performed best with minimum expansion and Sulphate ingress. On the other hand, the Type GU cement showed lower expansion and Sulphate ingress in comparison to the fly ash blended binder. Although bearing identical porosity, the blended binder had the smallest median pore size. Therefore, the Sulphate ingress and consequent ettringite production likely cracks the blended system more than the other two. Significantly, after longer durations of Sulphate exposure, the blended system showed higher tensile strength which implies a healing of cracks through ettringite formation.
-
Sulphate Resistance of fibre reinforced cement based foams
Construction and Building Materials, 2011Co-Authors: Muhammad Mamun, Vivek BindiganavileAbstract:Abstract This paper describes the results of an investigation on the Resistance of plain and fibre reinforced cement-based foams to Sulphate exposure. A synthetic foaming agent was used to produce foamed cementitious composites with essentially a closed cellular structure at 1200 kg/m 3 , 750 kg/m 3 , and 475 kg/m 3 . Polymeric microfibres were introduced at 0% and 0.2% volume fraction to result in 6 mixes. Prismatic specimens were immersed in a sodium Sulphate solution to be tested in flexure, after specific intervals of exposure, according to ASTM C1609. A comparison with the response of unexposed specimens reveals that the heavier cement-based foams are more susceptible to Sulphate attack and perform poorly with an increase in the duration of exposure. On the other hand, the lightest of the mixes—at 475 kg/m 3 —registered higher flexural strength and toughness factors up to 30 days of exposure before succumbing to Sulphate attack. This self-healing response was attributed to the space available in such highly porous composites that allows for the unhindered growth of ettringite without attendant cracking. The presence of microfibres facilitated self-healing, as evident from the flexural toughness factor.
V Rahhal - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate Resistance of type v cements with limestone filler and natural pozzolana
Cement & Concrete Composites, 2000Co-Authors: Edgardo F Irassar, M Gonzalez, V RahhalAbstract:Sulphate performance of concrete depends primarily on permeability. Under severe conditions of Sulphate exposure, low-permeability concrete is prescribed and it must also be made with high Sulphate resisting cement. For portland cement, the Sulphate Resistance depends on the C3A content and the amount of CH produced at early stages of hydration. Some parameters that modify the quantity of early CH in the hardened cement paste are investigated in this paper. Two type V cements with quite different C3S content and blended cements containing natural pozzolana or limestone filler were used. Expansion, flexural and compressive strength of mortar, immersed until 1 yr in sodium Sulphate solution, with pH-controlled are presented. Results show that the Sulphate performance of portland cement with high C3S content is very poor compared with low C3S portland cement. Addition of natural pozzolana provides the maximum Sulphate Resistance while the addition of 20% limestone filler declining Sulphate performance of low C3A cements. This behaviour can be attributed to the reaction between Sulphate ions with CH into the paste that produces an alteration of the predominant mechanism of Sulphate attack.
Edgardo F Irassar - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate Resistance of type v cements with limestone filler and natural pozzolana
Cement & Concrete Composites, 2000Co-Authors: Edgardo F Irassar, M Gonzalez, V RahhalAbstract:Sulphate performance of concrete depends primarily on permeability. Under severe conditions of Sulphate exposure, low-permeability concrete is prescribed and it must also be made with high Sulphate resisting cement. For portland cement, the Sulphate Resistance depends on the C3A content and the amount of CH produced at early stages of hydration. Some parameters that modify the quantity of early CH in the hardened cement paste are investigated in this paper. Two type V cements with quite different C3S content and blended cements containing natural pozzolana or limestone filler were used. Expansion, flexural and compressive strength of mortar, immersed until 1 yr in sodium Sulphate solution, with pH-controlled are presented. Results show that the Sulphate performance of portland cement with high C3S content is very poor compared with low C3S portland cement. Addition of natural pozzolana provides the maximum Sulphate Resistance while the addition of 20% limestone filler declining Sulphate performance of low C3A cements. This behaviour can be attributed to the reaction between Sulphate ions with CH into the paste that produces an alteration of the predominant mechanism of Sulphate attack.
M Ofarrell - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate Resistance of mortar containing ground brick clay calcined at different temperatures
Cement and Concrete Research, 1997Co-Authors: S. Wild, Jamal M. Khatib, M OfarrellAbstract:Abstract The Sulphate Resistance of mortar containing ground calcined brick clay (GCBC) calcined at different tempertaures (600–1100 °C) and ground sand (GS) as cement replacement materials is investigated. Also the porosity, pore size distribution and strength of a selection of these mortars are determined. Mortars containing GCBC calcined at a temperature higher than 900 °C show superior Sulphate Resistance to those containing GCBC calcined at temperatures below 900 °C. Although the intruded pore volume is higher at early ages of curing, the inclusion of GCBC in the mortars leads to refinement of pore structure and its contribution to strength is significant after a curing period of 90 days. The influence of the incorporation of GCBC (calcined at different temperatures) on the Sulphate Resistance of mortar, is discussed in terms of fundemental mechanisms.
I. Janotka - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate Resistance and passivation ability of the mortar made from pozzolan cement with zeolite
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: I. Janotka, L’. KrajčiAbstract:Sulphate Resistance and passivation ability of the mortars made from pozzolan cement of CEM IV/A (P) type according to European Standard EN 197-1 (zeolite blended cement with 60.82 mass% of PC clinker, 35.09 mass% of zeolite and 4.09 mass% of gypsum abbreviated as ZBC) and ordinary Portland cement (abbreviated as PC) are introduced. Resistance tests were performed in water and 5% sodium Sulphate solution (both 20°C) for 720 days. The increased Sulphate Resistance of pozzolan cement relative to that of PC was found. The key quantitative insight into the hydrate phase behaviour is given by thermal analysis. This is due to pozzolanic reaction of zeolite with PC resulting in reduction of the formed Ca(OH)_2 opposite to the reference PC. Ability of pozzolan cements with 15 to 50 mass% of zeolite to protect steel against corrosion was verified in 20°C/85% RH-wet air within 180-day cure. Steel was not corroded in the mortars made with pozzolan cement containing up to 35 mass% of zeolite. Pozzolan cement of CEM IV/A (P) type containing 35 mass% of zeolite is a suitable cementitious material for concrete structures exposed to Sulphate attack. Steel is protected against corrosion by this pozzolan cement in the same measure as the reference PC.
-
Hidratación y resistencia al ataque por sulfatos de cementos portland y cementos con zeolita natural
Materiales De Construccion, 2003Co-Authors: I. Janotka, S. C. MojumdarAbstract:The objective of this paper is to characterise Sulphate Resistance of mortars made from ordinary Portland cement ( PC ) and Portland-pozzolan cement with 35 wt.% of zeolite addition (zeolite-blended cement-ZBC ). Mortars with two different cement types were tested in water and 5% sodium Sulphate solution for 720 days. A favourable effect of zeolite on increased Sulphate Resistance of the cement is caused by decrease in free Ca(OH) 2 content of the mortar There is not sufficient of Ca(OH) 2 available for reacting with the Sulphate solution to form voluminous reaction products. A decreased C 3 A, content due to 35 wt.% replacement of PC by zeolite is the next pronounced factor improving Resistance of the mortar with such blended cement.
