Sulfate Resistance Of Mortars Research Articles

Sulfate resistance of mortars under semi-immersion condition: Impact of environmental humidity and fly ash content

Fly ash can effectively improve the sulfate resistance of immersed concrete by refining the pore size. However, increase of capillary pores may not be a good thing for salt crystals. In this paper, the effects of fly ash contents and environmental humidity on the sulfate resistance of semi-immersed mortars was investigated by appearance, mechnical strength, and microstructure. Capillary adsorption capacity, ingressed sulfate concentration and erosion productes were further investigated to analyze damage mechanism of mortar under semi-immersion condition. Lower environmental humidity and higher fly ash content were not conducive to the sulfate resistance of semi-submerged mortar, when the humidity was lower than 55 %, the fly ash content should be further reduced. The migration of sulfate ions in capillary pores and the physical salt crystallization in the region of humidity change are the main reasons for the damage.

Effect of waste stream materials on properties of cement mortars when used as supplementary binding materials

The present study focuses on the effect of waste stream materials on various properties of cement mortar when the waste materials are used as supplementary binding/cementitious materials (SCMs) for partial replacement of binding material. The effect and properties of various types of SCMs that are commonly used in mortar preparation replacing a part of cement (%) like limestone dust (LS), cement kiln dust (CKD), ground granulated blast furnace slag (GGBS), dolomitic limestone (DLS), ladle furnace slag (LDF), silica fume (SF), ceramic wastes (CW), fly ash (FA), pulverized fuel ash (PFA), waste glass sludge (WGS), etc. are studied and presented. Effects and characteristics of various combinations of different supplementary binding materials like the combination of FA with LS, an amalgamation of FA with DLS, the compatibility of FA with WGS, the mixture of GGBS with PFA, blending of GGBS with CKD, etc. are studied and reported. The elemental composition, pore size distribution system and microstructural composition were studied through X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) and discussed. The results of the study revealed that a combination of GGBS and PFA yields better results than the reference mixes made of cement and other blended mixes made of SCMs. The performance of CW and WGS is found good at the later age. The performance of fly ash on mortar properties depended on the dosage and fineness of fly ash. Apart from their better solo performance, a combination of limestone dust and silica fume not only enhances the strength but also the sulphate resistance of mortar. The study revealed that the use of SCMs in mortar contributes to a reduction in cement production and carbon emission.

Research on sulfate resistance of PC, SRPC and CSAC mortars incorporating coral waste filler

• Sulfate resistance of PC, SRPC and CSAC with CSP compared to LSP were studied. • CSP filler (≥20 %) replacing PC and SRPC suffered severe thaumasite attack at 5 °C. • CSAC-CSP specimens possess greater sulfate resistance than PC and SRPC specimens. • CSP filler in contrast with LSP results in less sulfate resistance of mortars. Coral waste filler partial replacing Portland cement facilitates the utilization of coral debris waste, the reduction of the economic cost of oceanic construction as well as the CO 2 emission. Thaumasite-related sulfate attack needs to be concerned because of rich calcium carbonate in form of aragonite in coral waste filler and the sulfate resources in the oceanic environment. The sulfate resistance of Portland cement (PC), sulfate resistant Portland cement (SRPC), and calcium sulfoaluminate cement (CSAC) incorporating coral sand powder (CSP) were studied under corrosion in 5 wt% NaSO 4 solution at 5 and 20 °C up to 540 days. The results show that CSAC-CSP specimens possess greater sulfate resistance than PC and SRPC specimens incorporating with CSP filler. Cracking was the main way for PC and SRPC specimens’ failure under sulfate attack at 20 °C. Exceeding 20 % of CSP filler replacing PC leads to server thaumasite-related sulfate attack exposure at 5 °C for 540 days. The formations of sulfate products including gypsum, ettringite, and thaumasite in PC-CSP and SRPC-CSP specimens were confirmed by XRD and FTIR tests. The ettringite-thaumasite cluster and deteriorated products were detected in PC and SRPC blended specimens. CSP filler in contrast with limestone powder (LSP) filler results in less sulfate resistance of blended specimens.

Research on the sulfate resistance of cement-based materials incorporating dolomite powder

The effects of dolomite powder on the sulfate resistance of cement-based materials with water-binder ratio (w/b) of 0.55 and 0.36 were investigated in this manuscript. Scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and pressure testing machine were used to determine the apparent morphology, micro-morphology, mass increase rate, flexural strength and compressive strength of cement-based materials containing dolomite powder. The sulfate resistance of mortars was improved with increasing dolomite powder dosage. Generally, the flexural strength and compressive strength of mortars in Na2SO4 solution were higher than those in water. Within 150 days of immersion, the corrosion resistance coefficient and compressive corrosion resistance coefficient of mortars increased with increasing dolomite powder dosage. The pore structure of cement-based materials became more compact with the addition of dolomite powder. Accordingly, the sulfate resistance was improved by controlling the dynamics stage due to the fact that the pore structure of cement-based materials was refined with the addition of dolomite powder. The 150-day compressive corrosion resistance coefficients of mortars with a w/b of 0.55 in the case of dolomite powder at 0 and 30 wt% replacement levels were less than 1, suggesting that long-term immersion in sulfate solution increased the deterioration rate of cement-based materials.

Experimental Investigation of MgAl‐NO2 and MgAl‐CO3 LDHs on Durability of Mortar and Concrete

Two kinds of layered double hydroxides (LDHs), MgAl‐NO2 (N‐LDH) and MgAl‐CO3 (C‐LDH), were incorporated to study the durability of mortar and concrete. The LDH contents of mortar were 1%, 2%, and 4% by mass and the LDH contents of concrete were 0.5%, 1%, 2%, 4%, respectively. The effect of LDHs on sulfate resistance of mortar was studied through dry‐wetting cycle test, compressive strength test, and flexural strength test. In addition, the effects of LDHs on pore structure, chloride resistance, carbonation resistance, shrinkage, and creep of concrete were investigated by SEM, mercury injection test, XRD, chloride ion diffusion coefficient test, chloride salt corrosion depth test, carbonation depth test, shrinkage test, and creep test. The results showed that LDHs can improve the ability of resisting ion corrosion, carbonization, shrinkage, and creep, reduce the pore content, and optimize the pore structure of mortar and concrete to some extent. Moreover, 4% LDHs had a better effect on improving the durability of mortar and concrete compared to 0.5%, 1%, and 2% LDHs, and the effect of C‐LDH was better than N‐LDH.

Effect of Mineral Admixtures on the Sulfate Resistance of High-Strength Piles Mortar.

Pre-stressed high-strength concrete piles (PHCP) are widely used in the building industry in China. The main aim of our research was to investigate the utilization of quartz powder, fly ash, and blast furnace slag as mineral additives to prepare PHCP mortar. The samples were prepared using steam and autoclaving steaming. The influence of minerals on the sulfate resistance of mortar was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that when compared to single doped quartz powder samples, samples prepared using fly ash or blast furnace slag improved the sulfate resistance of the PHCP mortar. Furthermore, the resistance to sulfate attack of samples with dual doped quartz powder, fly ash, and blast furnace slag also improved. MIP tests showed that mineral additives can change the pore size distribution after autoclave curing. However, the number of aching holes increased after mixing with 20% quartz powder and caused a decrease in the sulfate resistance.

Influence of pozzolanic materials on the properties of natural hydraulic lime based mortars

To evaluate the influence of pozzolanic materials (slag powder and silica fume) on the properties of natural hydraulic lime (NHL) based mortars, the properties of NHL mortar, slag powder-NHL based mortars (S-NHL) and silica fume-NHL based mortars (F-NHL) were studied deeply from the aspect of physical and mechanical properties, environmental resistance properties, hardening reaction process and micro morphology in this paper, among which S-NHL are prepared with 10% and 20% slag powder to substitute NHL and F-NHL are prepared with 10% and 20% silica fume to substitute NHL, respectively. The results indicate that the NHL mortars have preferable fluidity compared to the S-NHL and F-NHL mortars. In terms of mechanical properties, the compressive strength of S-NHL and F-NHL mortars have been significantly improved, among which the compressive strength of S20-NHL and F20-NHL mortars reached 7.73 MPa and 7.99 MPa at 28 days, respectively. The environmental erosion resistance of S-NHL and F-NHL mortars have been improved by a proportion of NHL is replaced by pozzolanic materials; moreover, the addition of slag powder has a more significant improvement on the sulfate resistance of mortars, and the acid resistance of mortars are improved obviously by the addition of silica fume. The pozzolanic materials and Ca(OH)2 occur pozzolanic reaction with water and produce more calcium silicate (aluminate) hydrate (C-S(A)-H), and CaCO3 crystals are formed by carbonizationreaction in mortar and interweave with hydration products to fill in the air pores of mortar, thereby the micro-structure of mortars have ameliorated, the performance of S-NHL and F-NHL mortars are improved finally. The pozzolanic index P show that the pozzolanic effect of silica fume is higher than slag powder at the early stage (before 28 days) of NHL based mortar hardening, and slag powder is higher than silica fume at the later stage (after 28 days), meanwhile slag powder has better effect for improving the compressive strength of mortar compared to silica fume.

Statistical model used to assessment the sulphate resistance of mortars with fly ashes

Abstract The use of low (LCFA) and high (HCFA) calcium fly ashes in the cement industry allows the implementation of European Union proposals on waste management and energy saving. However, the possibility of using HCFA is limited, because the properties of such waste from coal-fired power plants must comply with national regulations. The paper shows the effect of partial replacement of Portland cement (OPC) by these fly ashes on the resistance of the sulphate attack of the mortars immersed in a 5% solution of sodium sulphate. In order to determine the optimal amount of ash additive, a research plan was designed using statistical methods using the Gibbs triangle for mixtures. Samples of control mortars of OPC, binary mixtures of HCFA or LCFA and ternary mixtures of HCFA/LCFA were made. The composition of the blends was designed in accordance with the statistical plan of the experiment for mixtures. The testing program included linear strains, compressive strength and microstructure tests using SEM with EDXA and XRD analysis. The results of laboratory tests and statistical analyzes have shown that fly ash has a positive effect on the sulphate resistance of cementitious composites.

Sulfate resistance of calcined clay – Limestone – Portland cements

Calcined clays emerge as a promising source of supplementary cementitious material, which can provide a significant lowering of the Portland clinker content in blended cements. This study focusses on sulfate resistance of calcined clay (CC) – limestone (L) – Portland cements for mortars exposed to a 0.11 M Na2SO4 solution at 5 and 20 °C after a hydration period of 91 days. The pozzolanicity, compressive strength, pore structure, and sulfate resistance of mortars containing laboratory-made metakaolin or calcined montmorillonite and limestone have been investigated in cements with 35 wt% replacement of a white Portland or an ordinary Portland clinker. The results show that all mortars with CC/(CC + L) ≥ 0.5 exhibit excellent sulfate resistance. The consumption of portlandite by the pozzolanic reactions of the calcined clays and the dilution of the Portland clinker lead to a lower amount of calcium available for the secondary formation of gypsum and ettringite, which is identified as the main reason for the excellent sulfate resistance of the ternary blends. The results suggest that calcined clay – limestone – Portland cements are included in standards as a new type of sulfate-resisting Portland pozzolana cement and Portland composite cement.

Effects of Blaine and Tricalcium Aluminate on the Sulfate Resistance of Nanosilica-Containing Mortars

AbstractThis study set out to determine the effect of dry powder nanosilica (nS) on the sulfate resistance of mortars when paired with portland cements (PCs) of contrastingly different fineness and...

Effect of mineral admixtures on sulfate resistance of mortars under electrical field

This paper presents a study on sulfate resistance of mortars blended with and without silica fume or fly ash under electrical field. Performance of the mortars was determined by various means such as visual examination, sulfate concentration, flexural and compressive strength, as well as mineralogical analysis. The results showed that electrical field accelerated the deterioration induced by sulfate attack, as it sped up the ingress of sulfate ions into the mortar. The use of mineral admixtures improved the sulfate resistance of mortars. However, a relatively great amount of migrated sulfate as well as expansive sulfate products (gypsum and ettringite) were still found in the blended cement mortars under the electrical field, for which their deterioration was also notable. Therefore, the electrical field also accelerated sulfate attack on the mortars blended with mineral admixtures.

Sulfate resistance of low energy SFC no-cement mortar

This study presents the sulfate resistance of various low energy no-cement mortars made with SFC binder which was fabricated by purely combining three industrial by-products of ground granulated blast furnace slag (GGBFS) (S), Class F fly ash (FFA) (F), and circulating fluidized bed combustion fly ash (CFA) (C). The sulfate resistance of the mortar was determined based on the effects of sodium sulfate solution (NaSO4, 5%) on its expansion, strength loss, and phase changes. Experimental results showed that the SFC mortars had much better sulfate resistance than that of ordinary Portland cement (OPC) mortars. The increase of FFA amount significantly increased the sulfate resistance of SFC cement mortars with lower expansion and relatively high compressive strengths. The diffusing ions such as Na+ and SO42− from the sulfate environment noticeably activated the pozzolanic reaction of FFA in the hardened SFC binder pastes resulting in stronger microstructure of the mortar specimens. On the contrary, these ions adversely caused undesired expansive damage of OPC mortars resulting from the formulation of excessive ettringite (AFt) and gypsum precipitation.

The Effect of Natural Pozzolan on Sulfate Resisting Cement Exposed to Sodium Sulfate Attack for Attaining Sustainable Building Material

This paper investigates the sulfate resistance of blended cements produced by replacing 10, 20, and 30% of sulfate resisting cement (SRC) with Algerian natural pozzolan. Ordinary and blended cement mortar specimens were cast and immersed in a 5% sodium sulfate solution for 3 years. The sulfate resistance of mortars was evaluated by visual examination, compressive strength, mass change and diffraction (XRD), which was used to identify the degradation products formed by sulfate attack.The test results demonstrated that the sulfate resisting cement incorporating 10% of natural pozzolan was less susceptible to sulfate attack. In addition to improved performance, the results promise the production of a sustainable building material with environmental and economic benefits due to the reduced amount of overly-high-energy-consuming cement used and the potential reduction of the cost of sulfate resisting cement.

Investigation on masonry waste aggregate natural hydraulic lime mortars incorporating diatomite

In order to make the most of energy and resources and obtain mortars with beneficial properties, diatomite is employed in this paper as a partial replacement of natural hydraulic lime (NHL) and masonry waste as aggregate to prepare mortars with different water–binder ratios (w/b). Tests are conducted after 14, 28 and 90 d of curing, namely, compressive and flexural strength, microstructure, mass variation, apparent density, water absorption, sulfate resistance and, additionally, percentage strength and pozzolanic indexes are used to characterise the role of the pozzolanic effect in improving the mortars' strength. The results show that the introduction of diatomite improves the strength of mortars. The enhancement of strength is attributed to the pozzolanic reaction between diatomite and calcium hydroxide in NHL, which proceeds noticeably after 14 d of curing. The diatomite replacement percentage and w/b influenced apparent density, water absorption and strength of mortars; high density and low water absorption are propitious to strength enhancement. Sulfate resistance of mortars prepared with diatomite incorporation is improved greatly. The percentage strength and pozzolanic indexes of mortars indicate that diatomite has a significant pozzolanic effect and is a good active mineral admixture for NHL mortars.

Sulphate Attack Resistance of Cement with Zeolite Additive

Concrete as one of the most common building material, exposed to groundwater, soil and seawater is often object to sulphate attack. Partial replacement of Portland cement by natural zeolite has been proven to be effective in reducing sulphate attack. The results of cement sulphate resistance after 52 weeks in Na2SO4 solution are presented. The sulphate resistance of mortars was examined by determination of linear changes of specimens immersed in Na2SO4 solution. The studies of microstructure of cement mortars were carried out by scanning electron microscope equipped with energy dispersive spectrometer (EDS). Investigation includes also pictures of samples after 32 weeks exposition in corrosion solution.

The Impact of Aluminum- and Iron-Bearing Admixtures on the Resistance of Portland Cement Mortars to Alkali-Silica Reaction and Sulfate Attack

Study of sulfate resistance of mortars with aluminum- and iron-bearing admixtures (Al(OH)3, Al2(SO4)3, FeSO4, Fe2(SO4)3) in conditions close to those established in ASTM C 1012, and the study of the mitigation effect of these admixtures on alkali-silica reaction in accordance with accelerated “mortar bar” test ( GOST 8269.0, ASTM C 1260) were performed. Iron (II) and (III) sulfates show ability for mitigation alkali-silica reaction, while also, in contrast with Al-bearing substances, do not induce the drastic reducing of the initial setting time and do not promote the progress of sulfate corrosion. Compared with FeSO4, iron (III) sulfate has moderate deleterious impact on the early strength of cement paste and can be of interest alone as an inhibitor of ASR. Iron (II) sulfate may be used together with aluminum sulfate to offset the accelerating effect of the latter on the setting of cement paste and to reduce a risk of sulfate corrosion. During prolonged water storage, the mortar elongation and secondary ettringite formation do not occur, even when Al2(SO4)3 is available. Therefore, the investigated admixtures cannot act as agents of internal sulfate attack, however, Al2(SO4)3 can enhance the outer sulfate attack.

Influence Of Volcanic Scoria On Mechanical Strength, Chemical Resistance And Drying Shrinkage Of Mortars

Abstract In the study, three types of cement have been prepared; one CEM I type (the control sample) and two blended cements: CEM II/A-P and CEM II/B-P (EN 197-1), each of them with three replacement levels of volcanic scoria: (10 %, 15 %, 20 % wt.) and (25 %, 30 %, 35 % wt.), respectively. Strength development of mortars has been investigated at 2, 7, 28 and 90 days curing. Evaluation of chemical resistance of mortars containing scoria-based cements has been investigated through exposure to 5 % sulphate and 5 % sulphuric acid solutions in accordance with ASTM C1012 & ASTM 267, respectively. Drying shrinkage has been evaluated in accordance with ASTM C596. Test results showed that at early ages, the mortars containing CEM II/B-P binders had strengths much lower than that of the control mortar. However, at 90 days curing, the strengths were comparable to the control mortar. In addition, the increase of scoria significantly improved the sulphate resistance of mortars. Further, an increase in scoria addition improved the sulphuric acid resistance of mortar, especially at the early days of exposure. The results of drying shrinkage revealed that the CEM II/B-P mortar bars exhibited a greater contraction when compared to the control mortar, especially at early ages. However, drying shrinkage of mortars was not influenced much at longer times.

Durability-related properties of mortar and concrete containing copper tailings as a cement replacement material

This paper reports the results of research investigating the impact of copper tailings on some durability properties of cement pastes, mortars and concretes. Four mixtures incorporating copper tailings at 0% to 15% cement substitution levels by mass were used. Minor reductions in sulfate resistance of mortars and improved performance against autoclave expansion of pastes were observed in mixtures containing copper tailings. Despite increased water absorption and total permeable voids in concrete samples containing copper tailings, sample compressive and tensile strengths comparable to those of the control specimens were obtained. Resistance to acid attack and chloride penetration improved as the copper tailings content of mixtures increased. Moreover, chloride penetration depths obtained from immersion tests suggest that because the rapid chloride permeability test is an indicator of sample conductivity rather than chloride permeability, it may not be appropriate for evaluating mixtures with high-conductivity copper tailings. The high conductivity of concretes containing copper tailings could potentially be utilised in the de-icing of roadways and electromagnetic shielding of electrical and electronic devices.

Cement mixtures containing copper tailings as an additive: durability properties

The effects of copper tailings as an additive, on some durability properties of cement mixtures were investigated. In each mixture, copper tailings addition levels by mass were 0%, 5% and 10%. Compared to the control samples, copper tailings blended pastes showed superior performance against autoclave expansion while insignificant decreases in sulfate resistance of mortars were observed. Copper tailings increased the water absorption and total permeable voids of concretes slightly. However, the compressive and flexural strengths of blended concretes were higher than those of the control samples. Similarly, improved resistance to acid attack and chloride penetration as the copper tailings content of concretes increased were also observed. Results further showed that the ASTM C 1202 rapid chloride permeability test may not be a valid indicator of chloride migration in mixtures containing conductive copper tailings. These results suggest that copper tailings can potentially enhance the durability properties of cement based materials.

Durability of mortar and concretes containing slag with low hydraulic activity

Granulated blast furnace slag has been widely used as a partial substitute for Portland cement in many applications because of advantages which include cost reduction, reduction in heat evolution and improvement of durability properties. However, the effectiveness of slag depends on its hydraulic reactivity. In this paper, the results of an experimental study on the effect of slag with low hydraulicity on the mechanical and durability properties of concrete and the performance of mortar under sulfate attack are discussed. Special attention is given to gas permeability and water absorption of slag concrete. The durability of slag concrete is improved at long term at low Water/Binder ratio. Sulfate resistance of mortar is improved by slag replacement up to 30%.