Alkali-activated Slag Cement Research Articles

물-결합재 비와 잔골재-결합재 비에 따른 알칼리 활성화 슬래그 모르타르의 기초특성

본 연구는 물-결합재 비 (W/B)와 잔골재-결합재 비 (F/B)에 따른 알칼리 활성화 슬래그 시멘트 (AASC)의 기초 특성에 관한 연구이다. W/B 비는 0.35, 0.40, 0.45, 그리고 0.50를 선정하였다. 그리고 F/B 비는 1.00에서 3.00까지 0.25 크기로 고려하였다. 알칼리 활성화제는 2M과 4M의 NaOH를 사용하였다. 실험은 플로우, 흡수율, 압축강도, 초음파 속도 그리고 건조수축을 측정하여 비교하였다. 플로우, 압축강도, 흡수율, 초음파 속도 그리고 건조수축 모두 W/B 비가 증가하면 감소하였다. 압축강도는 동일 W/B 비에서 F/B 비가 증가할수록 감소하였다. 또한 특정 F/B 비에서 강도가 증가하는 것을 볼 수 있었다. 그리고 S2 (river sand 2)는 S1 (river sand 1)보다 낮은 물리적 특성을 나타냈는데, 이는 조립률 때문으로 판단된다. 본 실험의 결과 AASC의 공학적 특성은 W/B 비와 F/B 비가 영향을 주는 것으로 판단된다. 최적의 F/B 비는 각 W/B 비에 대해 1.75~2.50 인 것으로 생각된다. 또한 W/(B+F) 비가 0.13과 0.14 사이일 때 AASC 모르타르의 배합설계가 효과적일 것으로 판단된다. This study investigates the fundamental properties of the water-binder (W/B) ratio and fine aggregate-binder (F/B) ratio in the alkali-activated slag cement (AASC) mortar. The W/B ratios are 0.35, 0.40, 0.45, and 0.50, respectively. And then the F/B ratios varied between 1.00 and 3.00 at a constant increment of 0.25. The alkali activator was an 2M and 4M NaOH. The measured mechanical properties were compared, flow, compressive strength, absorption, ultra sonic velocity, and dry shrinkage. The flow, compressive strength, absorption, ultra sonic velocity and dry shrinkage decreased with increases W/B ratio. The compressive strength decreases with increase F/B ratio at same W/B ratio. Also, at certain value of F/B ratio significant increase in strength is observed. And S2 (river sand 2) had lower physical properties than S1 (river sand 1) due to the fineness modulus. The results of experiments indicated that the mechanical properties of AASC depended on the W/B ratio and F/B ratio. The optimum range for W/B ratios and F/B ratios of AASC is suggested that the F/B ratios by 1.75~2.50 at each W/B ratios. Moreover, the W/(B+F) ratios between 0.13 and 0.14 had a beneficial effect on the design of AASC mortar.

High strength metahalloysite based geopolymer

The unique properties of aluminosilicates had made them valuable in the wide range of industrial applications. One branch of application represents building materials. A significant factor of the level of the quality of engineering properties of building materials anyhow is the water/binder ratio. It is well known that its decreasing value effectively increases strength and quality of other engineering properties of the material. Due to the accompanying effect impairing workability of the mixture for processing the pressure compaction is needed.The subject of the paper are the results of the study of the properties of metahalloysite based geopolymer prepared under the use of the combination of very low water/metahalloysite ratio (0.08), pressure compaction of the fresh mixture by applying an uniaxial compressive stress of 300MPa and alkali activation. The effect of preparation conditions was systematically studied by thermal analysis (DTA, GTA), mercury intrusion porosimetry, scanning microscopy and compressive strength estimation of the geopolymer. The used metahalloysite was a product of calcination of the source material at 650°C 4h. It was an amorphous material showing an increased thermodynamic unstability and herewith an increased reactivity in comparison with the unheated solid.The metahalloysite based geopolymer pressure compacted paste reached after 24h of the hardening compressive strength of 76.2MPa whereas the reference paste only 0.03MPa. It represents 2540 times increase in behalf of the pressure compacted paste. High compressive strength was evidently the consequence of the found high homogeneous and dense pore structure of the pressure compacted paste.The regression analysis shown for the geopolymer binder systems a polynomial empirical equations as an appropriate configuration. For the alkali activated slag and Portland cement systems the exponential configuration was suitable. The cause of the difference may be apparent phase composition. It was pronouncedly amorphous structure of the geopolymer binder systems opposite to the combined amorphous and crystalline structures distinctive for alkali-activated slag and Portland cement binder systems. Then the resulted different destruction mechanism under the loading, at the strength test of the material.For the elucidation of the causality more detailed research is needed.

Effect of Dosage and Modulus of Water Glass on AC Impedance Properties of Alkali-Activated Slag Cement Mortar

Compressive strength and AC impedance of mortar made with water-glass-activated slag were investigated as a dependence of modulus (0.5-2.0) and dosage (2-6%) of the water-glass. Results shown that when the dosage of water glass is 2- 4 %, the modulus of the water glass has a little effect on the compressive strength. In the case of the dosage of water glass is beyond 4 %, when modulus of the water glass change from 0.5-1.0, the compressive strength obviously increases with increase of modulus of water glass and when modulus of the water glass change from 1.0-2.0, the modulus of the water glass has a little effect on the compressive strength. The strength increases with increase of the dosage from 2 to 6%. In the case same dosage and modulus, there is a rather good power correlation between the bulk resistance and the activated age. With increase of the dosage, the bulk resistance significantly decreases when the dosage is below 4%. The decreasing degree is small when the dosage is beyond 4%. The decreasing degree derived from the dosage increases with the activated age. The effect of the modulus on the bulk resistance depends on range of the dosage. However, it can be regarded that when the dosage is 4% and 6%, the modulus has small effect on the bulk resistance in the case of all the dosages.

Experimental Study of Alkali-Activated Red Mud Cement Material

In order to use the alkaline ingredient in red mud, this paper studied the strength variation law of alkali-activated red mud and lime cement material combined with slag. When the content ranged from 0 wt% to 20 wt%, the experiment showed that the flexural strength increased when the content increased, and the compress strength increased when the content increased with the content ranging from 0 wt% to 15 wt%. When the content reached 25 wt%, the strength of alkali-activated red mud cement material was equal with alkali activated slag cement. The SEM test of alkali-activated red mud cement material showed that red mud and lime both participated in hydration reaction fully.

Comparative Study of Different Cement-Based Inorganic Pastes towards the Development of FRIP Strengthening Technology

The development of fiber-reinforced inorganic polymer (FRIP) composites for strengthening reinforced concrete (RC) structures has become an active field of research in recent years. Compared with fiber-reinforced polymer (FRP) strengthening systems, a FRIP strengthening system possesses improved fire resistance but its performance depends largely on appropriate inorganic paste selection. This paper presents a comparative study of four typical inorganic pastes, made from the following: (1) magnesium phosphate cement (MPC), (2) magnesium oxychloride cement (MOC), (3) geopolymer (GP) cement (i.e., alkali-activated slag cement), and (4) polymer-modified mortar (PMM). The aim was to investigate their performance both as a matrix and bonding adhesive for FRIP strengthening systems. The evaluated performance included the workability and mechanical properties of inorganic pastes, the bonding strength of these pastes with both a concrete substrate and dry fiber sheets, the tensile properties of the formed FRIP composites, and the flexural strength of FRIP-strengthened concrete beams. The microstructures of the four types of inorganic matrix and the fiber-to-matrix interface were also examined. The MPC-based and MOC-based inorganic pastes exhibit similar structural performance as commercially available PMM and are well-suited for the development of FRIP strengthening technology. Geopolymer seems to be the most brittle among the four studied inorganic pastes.

실리카 퓸이 알칼리 활성화 슬래그 모르타르의 강도특성에 미치는 영향

이 연구는 물-결합재(W/B) 비에 따른 실리카 퓸이 알칼리 활성화 슬래그 시멘트(AASC)에 미치는 유동성과 강도 특성에 대한 연구이다. W/B비는 0.50에서 0.60까지 0.05 단위로 일정하게 변화시켰다. 실리카 퓸은 고로슬래그 중량의 0%에서 50%까지 치환시켰다. 활성화제는 수산화나트륨(NaOH)를 사용하였고, 농도는 3M로 하였다. W/B 비에 따른 강도는 1, 3, 7 그리고 28일을 측정하였다. 유동성 측정 결과는 실리카 퓸의 치환율이 증가할수록 감소하였다. 압축강도는 실리카 퓸의 치환율이 증가할수록 증가하였다. 또한 W/B 비가 증가할수록 모든 재령에서 강도는 감소하였다. 실리카 퓸은 W/B 비와 실리카 퓸의 치환율에 따라서 활성화 반응을 증대시켜 강도를 증가시키는 것을 알 수 있었다.

Properties of Alkli-Activated Slag Cement Compounded with Soluble Glasses with a High Silicate Modulus

Properties of alkali-activated slag cements compounded with soluble glasse with a high silicate modulus Ms=2.6 were detailedly studied in this paper, including compressive strength and flexure strength characterictics at the ages of 3,7,28 days and flow values of fresh cement mixtures on a jolting table. As a result, with the compressive strength at the age of 28 days of 95.6-107.8 MPa has been developed, and the flow values and strength characteristics of alkali-activated slag cement mortars increased with increase in a water to cement (alkaline activator solution to slag) ratio, and the flow value (determined on the cement mortar mixtures) would reach 145 mm. Moreover, the development speed of strength characteristics of mortar specimens would be affected negatively by increasing of water demand (requirement).

Adsorption of Calcium Lignosulphonate Water Reducer on Alkali-Activated Slag Cement Pastes

This paper shows how calcium lignosulphonate（CSL）water reducer affects the adsorption and rheological properties of alkali-activated slag cement (AASC) pastes activated by NaOH. It was concluded that the adsorption of water reducer on AASC pastes depended directly on the dosage of the water reducer and the retarder. Slag particles grounded with the retarder YP-3 adsorbed one and a half times of water reducer CSL as much as pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the retarder YP-3 is 14.00mV, compared with 9.25mV in the system without YP-3. Besides, the AASC pastes activated by NaOH containing the retarder YP-3 show better rheological properties and lower fluidity loss over time.

Effect of Quartz Powder on the Strength and Shrinkage of Alkali-Activated Slag Cement

Quartz powder with different fineness were added into alkali activated slag cement to reduce the drying shringkage of the hardened cement paste. Experimental results showed that partially replacing the slag powder with quartz powder will reduce the water requirement of normal consistency, dry shrinkage and early age compressive and flexural strength of alkali-activated slag cement (AASC), however, the flexural/compressive strength ratio and the fracture toughness will be increased and so does the later strength. The fracture section of specimen of quartz powder modified alkali-activates slag cement paste has a rougher texture than that of pure alkali-activates slag cement paste.

Adsorption of Naphthalene-Based Water Reducer on Alkali-Activated Slag Cement

In this work, the adsorption of naphthalene-based water reducer (FDN) on slag ground with or without the composite retarder YP-3 and PN (YP) in alkali-activated slag cement (AASC) activated by water glass (WG) has been studied in detail. The results show that the effect of the adsorption of water reducer on AASC depends directly on the dosage of the water reducer and on the composite retarder used. For example, mixed slag particles adsorb thrice as much water reducer FDN than pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the composite retarder is 8.61 mV, compared with 1.99 mV in the system without the composite retarder. Moreover, the AASC pastes activated by WG containing the retarder YP show better rheological properties and lower fluidity loss over time.

Adsorption Characteristics of Surfactant on Slag in Alkali Activated Slag Cement System

Alkali activated slag cement was a new green cementing material with many performances. Whereas, high viscosity and bad workability of the fresh mixture were the matters to embarrass its application. For exploring the special superplasticizer, the adsorption characteristics of surfactant on slag was studied, by UV Vis Absorption Spectrum Method. The results showed, first, the adsorbed amount of cationic surfactant [CH3(CH2)11N(CH3)3]Cl was the highest value among the five surfactants, 12.8 mg/g. Second, the effect of alkali on the adsorbed amount of surfactant was complex. Cationic surfactant had cooperativity with alkali. But, adding water glass, the adsorbed amounts of the surfactants on slag were negative, because it was both colloid property and alkali solution property. Finally, the retarder of YP-3 made the adsorbed amount of ionic surfactant to increase, due to YP-3 contracted electric double layer in the surface of slag.

EFFECTS OF CIRCULATING FLUIDIZED BED COMBUSTION FLY ASH ON THE PROPERTIES OF ALKALI-ACTIVATED SLAG CEMENT MORTARS

This paper illustrates the result of a study on the influence of circulating fluidized bed combustion (CFBC) fly ash, sodium hydroxide (NaOH), sodium silicate (Na2SiO3), sodium phosphate (Na3PO4), and sodium carbonate (Na2CO3) as activators on the workability, bleeding, setting time, compressive strength, shrinking, and absorption of the alkali-activated slag (AAS) cement mortars. The addition of CFBC fly ash, Na3PO4, and Na2CO3 shows decrease of workability. But with Na2SiO3, the workability increase was observed. The setting time of Na3PO4, NaOH, Na2SiO3, and Na2CO3 activated slag cement mortars was found to be much faster than the setting time of slag cement mortars. Slag cement mortars activated with CFBC fly ash show similar strength properties to slag cement mortars. CFBC fly ash activated slag cement mortars gained higher early compressive strength and developed 50MPa compressive strength at the age of 56 days. CFBC fly ash activated slag cement mortars were found providing higher compressive strength than other activated slag cement mortars.

Durability of Alkali-Activated Slag Cement in Seawater Environment

Durability of Alkali-Activated Slag Cement in Seawater Environment

Durability of Alkali-Activated Slag Cement in Seawater Environment

The durability of alkali-activated slag mortar in seawater environment, compared with that of ordinary portland cement mortar, was studied by drying-wetting test in accelerated laboratory seawater. The drying-wetting resistance, porosity, performance mechanism, and depth of chloride ingress were analyzed. The results show the mechanical properties of the AAS mortars were improved after 40 cycles, opposite to that of the OPC mortar, which is mostly due to the difference of porosity and pore structure. The chloride penetration resistance of AAS mortar was better, comparing to conventional OPC mortar.

The Effect of Surfactant and Alkali on the Surface Tension of Simulated Solutions of Alkali Activated Slag Cement System

Alkali activated slag cement and concrete are high strength, rapid hardening, low heat of hydration, good durability and so on. Whereas, too high viscosity and bad workability of the fresh mixture is the crux of the matter to embarrass application of alkali-activated slag cement and concrete. Development of special superplasticizer for alkali activated slag cement and concrete is a worth exploring way to solve the problem, and the study on the surface tension of simulated solutions of alkali activated slag cement system is one of the basic researches about the special superplasticizer. In this paper, the surface tension of surfactant-alkali-water was studied by Wilhelmy method. The results showed, first, water-glass had the best efficacity of several alkali activators, when the modulus of water-glass was 1.5 and dosage of water-glass by Na2O was 8%, the surface tension was reduced by 33 mN/m and reduced to 39.9mN/m; second, [CH3(CH2)9]2N(CH3)2Cl had the best efficacity of several surfactants, when the concentration of [CH3(CH2)9]2N(CH3)2Cl was 50g/L, the surface tension was reduced by 35.3 mN/m and reduced to 32.5 mN/m; finally, the effect of surfactant and alkali together on the surface tension of water was complex, surfactants had hardly effective in water glass.

Factors Influencing the Strength of Alkali-Activated Slag Cement

In this paper, water glass was chosen as activator to prepare Alkali-activated slag(AAS) cement. Effects of modulus and dosage of water glass, and admixture (fly ash, slag and silica fume) on the strength of AAS cement was investigated. It was found that the modulus of water glass had great effect on the strength of AAS cement when the mixing amount of water glass was less than 12%. With the incorporation of fly ash or slag, the strength of AAS cement decreased, however the incorporation of silica fume could promote the flexural and compressive strength of AAS cement slightly.

Influence of New Type Water Reducer Agent YC on Properties of Alkali-Activated Slag Cement Mortar

Through test on influence of water reducer agent YC on properties of alkali activated slag cement mortar, it is shown that water reducer agent YC has favorable plasticizing effect on alkali activated slag cement. When the alkali component is NaOH, the water reducer agent YC gives a water reduction rate of 22.0% to the alkali activated slag cement mortar and the flow ability loss with time is small. The water reducer agent can be adsorbed on the surface of slag and enhance theξpotential of the alkali activated slag cement system.

FT-IR Study on Early-Age Hydration of Alkali-Activated Slag Cement

The hydration process of alkali-activated slag cement, especially at early-age, was studied by FT-IR, compared with that of Portland cement. The results show that during the hydration of alkali activated slag cement, two processes have taken place, the dissolution of Al3+ from the slag and then the recombination of Al3+ ions with the silicate anions. The former associated with the break of the glass network of slag and the later with the re-polymerization of the silicate and aluminosilicate anions. The rate of break of the glass network increases with the dosage of water glass, which completed in 24 h when the dosage of the water glass solution equivalent to Na2O exceeds 6% of the slag powder. It is confirmed by the IR study that Ca(OH)2 is absent in the hardened alkali activated slag cement paste.

Physical effects of natural pozzolana on alkali-activated slag cement

The alkali-activated slag (AAS) cement is an interesting building material, confronting to the new economical and ecological challenges. In order to enhance its physical properties in comparison with ordinary Portland cement (OPC), we used natural pozzolana as a mineral addition. The parameters studied are: the fineness of the addition (5350 and 5650 cm2/g), and its percentage (0 to 30%). The activator used is NaOH (5M) and the curing temperature was fixed at 20°C. The results show the possibility to obtain compound alkali-activated slag cement with better stability and a compressive strength higher than 35 MPa.

A model for the C-A-S-H gel formed in alkali-activated slag cements

For first time, an experimental and computational study has been conducted to define a structural model for the C-A-S-H gel forming in alkali-activated slag (AAS) pastes that would account for the mechanical properties of these materials. The study involved a comparison with the C-S-H gel forming in a Portland cement paste. The structure of the C-A-S-H gels in AAS pastes depends on the nature of the alkali activator. When the activator is a NaOH, the structure of the C-S-H gel falls in between tobermorite 1.4 nm with a mean chain length of five, and tobermorite 1.1 nm with a mean length of 14. When waterglass is the activator the structure of the C-A-S-H gel is indicative of the co-existence of tobermorite 1.4 nm with a chain length of 11 and tobermorite 1.1 nm with a chain length of 14. This very densely packed structure gives rise to excellent mechanical properties.