Composite Mineral Admixture Research Articles

Effect of steam curing on strength, durability and microstructure of concretes with and without mineral admixtures

This research explores the effect of steam curing on the strength, durability and microstructure of concretes with and without mineral admixtures of fly ash (FA) and ground granulated blast-furnace slag powder (SL). Two types of C55 strength grade concretes (one was pure cement concrete, the other was a concrete made by replacing part of the cement with 12% FA and 18% SL) were prepared and their compressive strength, chloride diffusion coefficient and carbonation depth under standard and steam-curing conditions were measured and compared. The phase composition and microstructure of the concretes under the two curing conditions were tested by X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry. The results showed that, on the one hand, compared with standard curing, steam curing is beneficial to the early strength, but not conducive to the later strength development and chloride permeability resistance of both types of concretes. Furthermore, for the steam-cured concrete, the 28 days carbonation depth of the forming surface is higher than that of the bottom surface. In addition, steam curing can reduce the carbonisation resistance of pure cement concrete and improve the carbonisation resistance of concrete mixed with FA and SL. On the other hand, composite mineral admixtures of FA and SL reduce the early strength and the carbonisation resistance of concrete cured by standard curing, but improve the later strength, the carbonisation resistance and chloride permeability resistance of concrete cured by steam curing. FA and SL are thermally activated under steam curing and can react with the calcium hydroxide formed by cement hydration in the early stage, which produces a larger amount of secondary hydration products to improve the pore structure and interfacial microstructure of the concrete with FA and SL. In this way, the adverse effects of steam curing on later strength and durability of concrete are significantly restrained by composite mineral admixtures of FA and SL.

Splitting Tensile Mechanical Performance and Mesoscopic Failure Mechanisms of High-Performance Concrete under 10-Year Corrosion from Salt Lake Brine

In regions characterized by the challenging combination of brine corrosion in the salt lakes and river sand with alkali silica reaction (ASR) activity in areas of the Northwest, high-performance concrete (HPC) formulated with high-volume composite mineral admixtures as ASR suppression measures has been preferred for civil engineering structures in the region. This study investigates the splitting tensile strength, corrosion products, microscopic structure characteristics, and mesoscopic mechanical mechanisms of splitting failure of such HPC under 10-year corrosion from salt lake brine. The relationship between mechanical properties and corrosion damage, as well as the characteristics of internal crack propagation paths and failure mechanisms of HPC under splitting load, are explored. The findings reveal that as the alkali content within HPC rises, corrosion damage intensifies, resulting in a reduction in splitting tensile strength. Moreover, a linear association between mechanical properties and corrosion damage is observed. Microscopic structural analysis and numerical simulation of the splitting failure process of HPC elucidate that while the substantial presence of mineral admixtures effectively suppresses the ASR risk associated with alkali-reactive aggregates in concrete, uneven ASR gel products persist. These discontinuous micro-fine interface cracks induced by the gel products and the cracks induced by the gel products around the selective alkali-active aggregate particles distributed in the local area are the initiation sources of mortar cracks in HPC splitting failure. In terms of the overall failure state observed during the concrete splitting process, mortar cracks manifest two distinct extension paths: along the coarse aggregate interface and directly through the aggregates themselves. Notably, a greater proportion of coarse aggregates are directly penetrated by mortar cracks, as opposed to the number of interface failures bypassing coarse aggregates. More importantly, the above work establishes a theoretical reference in three dimensions: macroscopic, mesoscopic, and microscopic, for studying concrete corrosion damage in complex environments such as salt lake brine corrosion and ASR inhibition.

Degradation Law and Service Life Prediction Model of Tunnel Lining Concrete Suffered Combined Effects of Sulfate Attack and Drying-Wetting Cycles.

The present study explored the degradation law and service life prediction of tunnel lining concrete with different mineral admixtures under coupled actions of sulfate attack (SA) and drying–wetting (DW) cycles. The deterioration resistance coefficient (DRC) of compressive strength and influence coefficients of sulfate concentration, mineral admixture content, water/binder (w/b) ratio, and curing regime on DRC were studied. After that, a new service life prediction model based on damage mechanics was developed and analyzed. Results show that, by increasing the DW cycles, the DRC first increases and then decreases. DRCs of Ordinary Portland cement (OPC), fly ash (FA), and ground granulated blast-furnace slag (GGBS) concrete linearly decrease with the increase of sulfate concentration, while the silica fume (SF) concrete displays a two-stage process; by increasing the admixture content, the DRCs of FA and GGBS concrete exhibit two distinct stages, while the SF concrete depicts a three-stage process; increasing the w/b ratio linearly decreases the DRC; the DRC of curing regime was sequenced as standard curing (SC) > fog curing (FC) > water curing (WC) > same condition curing (SCC). Based on the experimental results, the service life prediction model is applied and validated. The validation results show that the proposed model can accurately predict the lifetime of concrete with different mix proportions. Furthermore, it is found that the mineral admixture can effectively improve the lifetime of concrete, and the composite mineral admixture is more effective than a single mineral admixture in improving the lifetime of concrete.

Upcycling sintering red mud waste for novel superfine composite mineral admixture and CO2 sequestration

To utilize the sintering red mud waste（SRM）on a large scale and sequester CO2, a room temperature in-situ wet carbonation method was proposed for activation of SRM. The wet carbonation reaction process of SRM was investigated, and the evolution of phase composition, microstructure and pore structure during carbonation of the SRM was revealed by XRD, TG/DTG, FT-IR, NMR, SEM and nitrogen adsorption. Moreover, the feasibility of carbonated SRM (C-SRM) as a high value-added mineral admixture was explored. The results showed that the carbonation of SRM produced a large number of fine calcite crystals and silica-alumina gel with high polymerization. After 3 h of carbonation, the SRM achieved a CO2 sequestration rate of 15.3%, calcite (Cc) yield of 86.5% and Na+ leaching rate of 81.8%. The C-SRM possessed a high pozzolanic reactivity and fine particle size, showing its potential as a cement mineral admixture.

Influence of Steel Slag-Superfine Blast Furnace Slag Composite Mineral Admixture on the Properties of Mortar and Concrete

A composite mineral admixture was prepared by steel slag and superfine blast furnace slag. The influence of superfine blast furnace slag content of the composite mixture on the mortar and concrete was investigated. The results show that the composite mineral admixture may decrease the strength of concrete at the early age but improve the strength development over time. Increasing the content of superfine blast furnace slag can reduce the degradation of the early strength. The reduction of the autogenous shrinkage and adiabatic temperature rise is significant when the composite mineral admixture is added. The reduction is more obvious when the water-to-solid ratio (w/s) is low. The results show that with steel slag and superfine blast furnace slag playing as complementary parts in the composite mineral admixture, it can be used as an effective substitute of cement.

Effects of different composite mineral admixtures on the early hydration and long-term properties of cement-based materials: A comparative study

The exploration of sustainable and green cement-based materials prepared from industrial solid wastes is an important research direction in the development of new building materials. This paper carried out a quantitative comparative study of the influences of different composite mineral admixtures prepared with fly ash, steel slag, and ground granulated blast furnace slag (GBFS) as supplementary cementitious materials (SCMs) on the early hydration, long-term (360 d and 720 d) mechanical properties and penetrability of cement-based systems. The results show that adding GBFS and steel slag has the greatest influence on the early hydration of cement due to their synergistic reactions. Over time, it becomes increasingly apparent that adding composite admixtures containing GBFS and fly ash can refine the long-term pore structure, reduce the brittleness, improve the long-term strength and chloride ion penetrability resistance of concrete to the greatest extent. However, adding composite admixtures containing steel slag and fly ash has no positive impact on the long-term properties of concrete. From a comprehensive perspective, considering early hydration, long-term properties and economic costs, composite admixtures containing GBFS and steel slag have potential for wide popularization and applications which can promote the sustainable utilization of steel slag and cleaner production of green concrete.

Experimental Study on Early Drying Shrinkage of Self-compacting Barite Concrete

In this paper, raw materials such as fly ash-S95 grade mineral powder composite mineral admixture, barite coarse and fine aggregate and polycarboxylic acid water reducer are selected to successfully formulate C30 self-compacting barite concrete with good performance. It also analyzes the development law of early drying shrinkage of self-compacting barite concrete with age, and discusses the effects of fly ash and slag mixing ratio and water reducer content on concrete work, compressive strength and early drying shrinkage. The results show that: the drying shrinkage of self-compacting barite concrete develops rapidly within 1 day of age, and the drying shrinkage rate at 1 day accounts for 50% to 66% of that at 7 days of age, and then the growth trend is slow; as the proportion of fly ash increases, the performance of the concrete mixture improves. While the strength of concrete decreases in the early and mid-term, the strength gradually increases in the later period, and the shrinkage strain of concrete in the early stage also increases significantly; the proper amount of water-reducing agent can greatly improve the fluidity of the mixture. In the dosage range of 1.2%~1.4%, with the increase of the amount of water reducing agent, the compressive strength first increases and then decreases, reaching the maximum when the dosage is 1.3%, and the early drying shrinkage strain of concrete increases slightly.

Study on the properties of composite mineral admixture material for rapid repair

In this paper, the active mineral admixture was used to prepare the quick repair material that meets the requirements of 24h service. The development of the late strength, the shrinkage performance and wear resistance of the 60days were studied. The experimental results show that the composite mineral admixture is used to prepare the material for rapid repair, not only the early strength is high, but also the later strength is steadily increasing, and the dry age of 60 days is reduced, and the wear resistance is good. The use of industrial waste has certain economic and social benefits.

Influence of steel slag-silica fume composite mineral admixture on the properties of concrete

A composite mineral admixture was prepared by grinding a mixture of steel slag and silica fume (steel slag/silica fume ratio is 92:8 or 84:16, by mass). A layer of silica fume was uniformly adsorbed on the steel slag particles. The influence of this steel slag-silica fume composite mineral admixture on the hydration of a cement-based composite binder and the properties of its concrete were investigated. The results show that the silica fume in the composite mineral admixture contributes significantly to the consumption of Ca(OH)2 and enhances the connection between the steel slag particles with the surrounding C-S-H gel. The activity of the composite mineral admixture improves with an increase in the silica fume content. The retarding effect of the composite mineral admixture on the early hydration of cement is significant. However, a proper cement replacement by the composite mineral admixture can improve the late-age pore structure of hardened paste as well as the strength, chloride ion resistance, carbonation resistance, and sulfate attack resistance of concrete. The proper addition of the composite mineral admixture can reduce the drying shrinkage of concrete.

Application of Ground Granulate Blast Furnace Slag-Steel Slag Composite Binder in a Massive Concrete Structure under Severe Sulphate Attack

A composite mineral binder was prepared by mixing ground granulate blast furnace slag (GGBS) and steel slag (GGBS/steel slag ratios are 1 : 1 or 3 : 2 by mass). The application of a composite binder in a massive concrete structure under severe sulphate attack is discussed by determining the hydration heat, adiabatic temperature increase, compressive strength, elastic modulus, chloride ion permeability, and sulphate attack resistance. The results show that the hydration heat of the composite binder decreases greatly when the cement replacement ratio increases to 50% at 45°C. The adiabatic temperature rise of the concrete containing the composite mineral admixture decreases significantly. Concrete containing the composite mineral admixture has a lower early elastic modulus and satisfactory late-age compressive strength. The composite mineral admixture can improve the resistance to chloride ion permeability and sulphate attack resistance of concrete, especially during temperature match curing.

Impact of Composite Mineral Admixture on Carbonization Resistance of High Performance Concrete

Fly ash, silica fume and ground steel slag are chosen to make up composite mineral admixtures. Through the orthogonal test, carbonization resistance property of High Performance Concrete (HPC) mixed with composite mineral admixtures is studied. Test results show that the carbonization resistance property of HPC can be improved with defined amount of composite mineral admixture mixed, in addition, the effect of ternary composite admixture of ground steel slag, fly ash and silica fume is more obvious than that of binary composite admixture.

Long-term properties of concrete containing ground granulated blast furnace slag and steel slag

In this paper, the influence of six different mineral admixtures on the long-term properties of concrete within 1080 d is investigated; these admixtures include steel slag, ground granulated blast furnace slag (GGBS) and composite mineral admixtures with four different GGBS-to-steel slag ratios. The results show that steel slag and composite mineral admixtures with a high content of steel slag have many negative effects on the long-term properties of concrete, such as decreasing strength, increasing porosity and chloride penetrability, and decreasing carbonation and sulfate resistance. GGBS tends to improve the long-term properties of concrete. Concrete containing composite mineral admixture with a high content of GGBS can achieve similar long-term strength, porosity, chloride penetrability, and carbonation and sulfate resistance to Portland cement concrete. The influence of the composite mineral admixture composed of 80% GGBS and 20% steel slag on the long-term properties of concrete might be very close to that of GGBS. All the mineral admixtures tend to decrease the long-term drying shrinkage of concrete. The effect of composite mineral admixtures with higher GGBS content on the long-term drying shrinkage of concrete is more significant.

Activity Index of Steel Slag-GGBS Composite Mineral Admixture at Different W/B Ratios

The activity index of steel slag-GGBS composite mineral admixture with different steel slag contents at the W/B of 0.3, 0.4, and 0.5 was investigated. The results show that the activity index of the composite mineral admixture with higher GGBS content is larger, and this phenomenon is more obvious at later ages. At lower W/B, the gap of activity index of different composite mineral admixtures is smaller. The activity index of each composite mineral admixture is higher at lower W/B and at later age. The steel slag-GGBS composite mineral admixture is more suitable to be used in high strength concrete than in low strength concrete. As far as the long-term properties of concrete are concerned, the activity index of the composite mineral admixture at the late age should be adopted.

Mechanical Properties of Concrete with Compound Mineral Admixtures

The influence of multi-component composite mineral admixtures on the mechanical properties and workability of concrete is studied in this paper, such as steel slag (SS), blast furnace slag (BFS) and fly ash (FA). Considering the above-mentioned factors, the optimal mixture ratio and substituted amount of composite mineral admixtures replacing equally cement are obtained. The results showed that composite mineral admixtures reduced the early compressive strength of concrete with composite admixtures, but significantly improved the workability and later compressive strength of concrete with composite admixtures. On the other hand, the optimal mixture ratio and substituted amount of double-mixing mineral admixtures are different.

Properties of Concrete with High-Volume Limestone Powder under Low Temperature Conditions

This paper studies the effects of high-volume composite mineral admixture made of limestone powder and low-quality fly ash on the properties of concrete,and studies the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment.Through experiments, this paper makes clear the workability of fresh concrete and analyzes the law of strength development of concrete. The experimental results indicate that the concrete with high-volume limestone powder as composite mineral admixture has good fresh properties; due to low water consumption per unit volume, medium-and-high-strength concrete can be prepared. As new type concrete mineral admixture, the composite mineral admixture made of limestone powder and low-quality fly ash will play an active role in the sustainable development of concrete industry. After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200d, gypsum attack-led destruction is caused to the concrete test cube, without thaumasite sulfate attack.

Properties of Concrete with High-Volume Limestone Powder as Composite Mineral Admixture

This paper studies the effects of high-volume composite mineral admixture made of limestone powder and low-quality fly ash on the properties of concrete. Through experiments, this paper makes clear the workability of fresh concrete and analyzes the law of strength development of concrete. The experimental results indicate that the concrete with high-volume limestone powder as composite mineral admixture has good fresh properties; due to low water consumption per unit volume, medium-and-high-strength concrete can be prepared. As new type concrete mineral admixture, the composite mineral admixture made of limestone powder and low-quality fly ash will play an active role in the sustainable development of concrete industry.

Experimental Study on Impermeability and Frost Resistance of High Strength Concrete Used in Shaft of Coal Mine

This paper presents results of impermeability and frost resistance tests of a series of high strength concrete which will be used in Yuncheng coal mine shaft lining. And the shaft is one of the most difficult to construct using freezing method because of the extreme thick overburden soil. The results show the impermeability and frost resistance of the selected concrete mix proportion options can meet the special requirements of the shaft construction. It’s due to the low water-cement ratio, admixture and water-reducing agent decreases void caused by excess water. And the composite mineral admixture forms bubbles to cut off the tiny water permeable channels in cement stone. Also the filling effect and pozzolanic effect caused by fly ash contribute a lot. The research on high strength concrete used in shaft of coal mine with thick overburden soil is still rare worldwide.

The relationship between autogenous shrinkage and pore structure of cement paste with mineral admixtures

In this paper, the combination of fly ash and silica fume, or fly ash and blast furnace slag were used as the composite mineral admixtures in cement paste. The autogenous shrinkage and the pore structure of the hardened cement paste with mineral admixtures were tested, and the relationship of the autogenous shrinkage and pore structure also was discussed. The results indicate that fly ash can reduce the autogenous shrinkage, and silica fume can increase the autogenous shrinkage, and the effect of blast furnace slag is between the two above; although both silica fume and blast furnace slag can weaken the porosity and the mean diameter of cement paste, and increase the volumetric percentage of pores whose diameter is between 5 and 50 nm and pore specific surface, silica fume is better than blast furnace slag in changing the pore structure. The relationship between the autogenous shrinkage and volumetric percentage of pores whose diameter is between 5 and 50 nm is obviously proportional.

Properties and microstructure of marine concrete with composite mineral admixture

The influences of compositing mineral admixtures on the regularity of mechanical property, workability, durability and microstructure of C50 marine concrete were investigated. The results show that the incorporation of mineral admixtures can improve the mechanical properties and workability of C50 marine concrete, 3 min-doped mineral admixture had excellent resistance to chloride ion permeability. The microscopic structure mixing mineral admixtures system was well-distributed and compact, little macroporeare can be found.

Effect of Curing Conditions on Property of High Performance Concrete with Composite Mineral Admixture

In this paper, the development of cubic compressive strength of concrete with the age was studied first. Four kinds of concrete, which were made from the mixes by using 0%, 20%, 30% and 40% Composite Mineral Admixture (CMA) as the replacement of the cement for each kind of concrete, were used in the study. Test results showed that the concrete with 30% CMA had the best properties compared with others both under standard-curing condition and steam-curing condition. Furthermore, the normal concrete (without CMA ) and the high performance concrete (with 30% CMA) were chosen as the main materials in comparative tests to study the effect of curing conditions on the property of high performance concrete, such as the basic mechanical properties, the property against chloride penetration, and the property against carbonization. The results indicated that the curing temperature would increase the concrete strength in early age but not in long term. The curing condition would affect the property of concrete against carbonization but not the property of concrete against chloride penetration obviously.