Low Hydration Heat Research Articles

Effects of Modified Glycerol Distillation Residues (MGDR) on the Performance and Hydration of Portland Cement

The feasibility of modified glycerol distillation residues (MGDR) used for chemical additives of cement was studied. MGDR showed good grinding and strengthen effect which was similar with triethanolamine (TEA), and the performance of MGDR was better in PC 32.5. Samples with MGDR showed lower heat of hydration than samples with same dosages of TEA, and the initial heat rate of hydration was as the order TEA> TEA + MGDR> blank. The hydration products of samples with MGDR were also similar with TEA, but the former showed more AFt crystals and less Ca (OH)2.

Properties of non-standard fly ash – slag cements containing calcareous fly ash

The paper presents the tests results of the properties of non - standard fly ash - slag cements composition. Both natural (unprocessed) and activated by grinding calcareous fly ash was used. It was found that the calcareous fly ash next to the granulated blast furnace slag may be a component of low - clinker cements (ca. 40%). Those cements are characterized by low heat of hydration and overdue of initial setting time in comparison with Ordinary Portland Cement, moreover they have an unfavorable effect on consistency and its upkeep in time. Production of fly ash - slag cements is possible for strength class 32,5 N when the component of cement is raw fly ash, and for strength classes 32,5 N, 32,5 R and 42,5 N when ground fly ash was used. Fly ash activated by grinding was characterized by higher activity.

A Study of the Preparation and Properties of the Concrete for the Bearing Platform of the Xiamen-Zhangzhou Sea-Spanning Bridge

In light of the requirement of mass concrete for the bearing platform of the main tower of the Beicha Main Bridge of the Xiamen-Zhangzhou Sea-spanning Bridge, and in view of the hostile environmental conditions for the project, a study was conducted on the technology of preparing high-performance marine concrete for the bearing platform of the sea-spanning bridge in order to control concrete temperatures and achieve the desired durability for the bridge. With an optimal design which features the binary admixture of fly ash and slag and an optimal concrete mix ratio, high-performance concrete with lower hydration heat and strong resistance to chloride diffusion and cracking was successfully developed for the bearing platform of the sea-spanning bridge.

Development of new cement based matrices for safe disposal of hazardous metals: cadmium and caesium

The innovative multicomponent matrix for immobilising cadmium and caesium introduced in this paper consists of belite cement, gismondine type NaP zeolite and nanoadditions. With this innovative design, the solid blend was able to absorb a high proportion of simulated radioactive liquid waste. Matrix integrity and effect of the high waste/solid ratio were assessed by X-ray diffraction analysis, while BET-N2 surface area, pore size distribution and nanoporosity were determined with nitrogen adsorption isotherms. Matrices whose sole component was fly ash belite cement were used as a reference. This innovative material affords substantial social and environmental benefits, inasmuch as the cement used has a low CO2 content and low heat of hydration. Moreover, both the cement and the zeolite can be synthesised ecoefficiently from an industrial byproduct, thereby eliminating the need to stockpile waste while preserving natural resources and placing valorised byproducts on the market.

Effect of Clay Fines on the Behavior of Self-Compacting Concrete

The technology of concrete has significantly increased in recent years through the use of super plasticizer and availability of mineral additions. One of the most recent materials used as an additive, replacing a portion of cement in concrete, is fine clay fired at a temperature of 800℃ to 900℃. This research is based on trials that complied with artificial pozzolan (waste crushed brick), and their effect on the rheological and mechanical behavior of mortar. The addition of 5% of a waste crushed brick has helped not only to improve the strength (tensile and compression), but also to foster a better rheological behavior in terms of fluidity and stability, with a low heat of hydration compared to control. However, tests of optimizing the content of self-compacting concrete (SCC) in coarse aggregates, sand and binder, led us to confirm that the combined mass of more optimal (better workability and stability) is that based on low in volumetric percentage of sand/paste with a granular skeleton richest gravel low dimensions (2/3 of G 3/8 and 1/3 of G 8/15).

Quasi-static and dynamic compressive mechanical properties of engineered cementitious composite incorporating ground granulated blast furnace slag

The ground granulated blast-furnace slag (GGBS) has been widely used as a supplementary cementitious material in concrete production due to its lower heat of hydration, ability to gain strength over a longer period, superior performance against chemical attacks, and lower environmental impact. Four Engineered Cementitious Composite (ECC) mixtures with 50%, 60%, 70% and 80% substitution amounts of GGBS were prepared and their dynamic compressive mechanical behavior had been investigated by using a split Hopkinson pressure bar (SHPB) system at strain rates ranging from 84.8 to 184.6s−1. The corresponding quasi-static compressive responses of GGBS–ECC were also studied experimentally for contrasting with their dynamic tests. The objective of using GGBS to replace fly ash in ECC was to obtain higher quasi-static compressive strength and dynamic load-carrying capacity. The dynamic compressive stress–strain curves did not show residual strength behavior as that in the quasi-static stress–strain curves. ECC incorporating GGBS exhibited strain rate dependence. The peak stress increased and the peak strain decreased with the increase of strain rates. The toughness ratio under quasi-static compression was lower than that of dynamic compression according to the proposed method in this study. The toughness ratio under dynamic compression showed a slight increase with the GGBS content increasing. The strain rate had little influence on the toughness ratio.

Effect of blended steel slag–GBFS mineral admixture on hydration and strength of cement

The possibility of using steel slag and granulated blast furnace slag (GBFS) as a blended mineral admixture for concrete is investigated. The results show that GBFS can weaken the negative effects of steel slag on the properties of concrete, such as decrease of the strength and introduction of harmful pores. The steel slag–GBFS blended mineral admixture containing 30–50% steel slag can enable the mortar to have a satisfactory strength. Steel slag has an excellent ability to retard the setting time, decrease hydration heat, and improve the fluidity of concrete comparing with GBFS. The blended mineral admixture composed of 50% steel slag and 50% GBFS is more efficient than fly ash in decreasing the early hydration heat of binder. Steel slag and GBFS are mutually complementary in many properties, and an ideal blended mineral admixture which endows the concrete satisfactory strength, long setting time, low hydration heat, and good fluidity can be obtained by mixing steel slag and GBFS at proper ratios.

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.

Microstructure and mechanical properties of CaCO3 whisker-reinforced cement

Composite Portland cement (PC) played an important role in various kinds of construction engineering owing to low hydration heat, low-cost, and application of solid industrial waste, but its brittleness and low strength limited its use in stress-bearing locations. The aim of this study is to improve the toughness and fracture resistance by incorporating CaCO3 whisker in cement matrix. Effect of different content of calcium carbonate whiskers on the mechanical properties of PC was investigated. The results showed that the flexural strength, impact strength and split tensile strength were increased by 39.7%, 39.25% and 36.34% at maximum, respectively. Microstructure and elements of the whiskers in hardened cement were observed and analyzed by SEM/EDS. The mechanisms of the reinforcement of CaCO3 whisker on cement were also discussed, and the conclusion was that the improvement could be correlated to energy-dissipating processes owing to crack bridging, crack deflection, and whisker pull-out at the crack tips.

벨라이트계 혼합 결합재의 수화열 특성에 관한 연구

전국적으로 토목 및 건축 구조물의 대단위 공사 및 정비 사업이 발족 및 추진되어 부재 크기가 큰 매스 콘크리트 구조물이 많이 건설되고 있다. 대규모 콘크리트 구조물의 콘크리트 매트릭스 내 높은 수화열 발생은 콘크리트의 품질 및 시공 기간을 좌우하는 가장 중요한 요인이 되고 있다. 이로 인해 발생되는 내부 균열이 콘크리트의 내구성, 수밀성 및 강도를 저하 시키게 된다. 벨라이트계 저열 포틀랜드 시멘트와 산업부산물을 이용한 수화열을 저감시키는 방법으로 이 연구에서는 고로 슬래그 또는 플라이애쉬를 7단계로 치환한 2성 분계 결합재와 4단계로 치환한 3성 분계 결합재를 사용하였고, 혼화재의 치환율 변화가 재령에 따른 수화 발열량, 강도 및 SEM, XRD 등의 기초 물성에 미치는 영향을 비교 분석하였다. 플라이애쉬가 치환된 2성 분계 결합재의 28일 누적 수화열은 플라이애쉬 함유량의 증가함에 따른 높은 수화열 저감 효과를 보여주며, 고로 슬래그가 치환된 2성 분계 결합재의 28일 누적 수화열은 고로 슬래그 치환율이 증가함에 따라 감소하지만 수화열 감소 효과는 높은 치환율 대비 낮은 결과를 나타내었다. 3성 분계 결합재의 28일 누적 수화열의 경우 플라이애쉬 치환율이 높아짐에 따라 낮은 수화열 결과를 보여주며 특히 40% 플라이애쉬 및 30% 고로 슬래그 결합재는 벨라이트계 저열 포틀랜드 시멘트 대비 50%의 저열 효과를 보여주었다. 연구 결과를 통해 수화열 발생이 낮고 시공 가능한 압축강도를 가진 벨라이트계 혼합 결합재를 사용하여 콘크리트 내 온도 상승이 감소된 것을 보여주었다.

해양구조물 적용을 위한 경량골재콘크리트의 기초물성에 관한 연구

The various properties of concrete have been required, as civil engineering structures are getting larger and complicated. Therefore, the high performance of concrete, such as high strength, high fluidity, and low hydration heat, has been investigated largely. In this study, the properties of lightweight concrete-reducing self-weight of structure member have been studied in order to check the applicability of lightweight aggregate concrete to structural material. The experiments on compressive strength, splitting tensile strength, unit weight, and modulus of elasticity have been conducted with varying PLC, LWCI, LWCII, LWCII-SF5, LWCII-SF15 to check the basic properties. The compressive strength of 21MPa was obtained easily by using lightweight aggregate concrete and the addition of silica fume to increase the compressive strength slightly. To use lightweight aggregate concrete for civil engineering structures, systematic and rigorous studies are necessary.

Monitoring Study of Shaft Lining Concrete Strain in Freezing Water-Bearing Soft Rock During Mine Shaft Construction Period in West China

Abstract In the water-bearing soft rock strata of West China, a field measurement is carried out on the shaft lining in bedrock section. The shaft lining is built with freezing method. From the measurement, some changes of regularity in construction, thawing and post thawing period are obtained, including the temperature, freezing pressure and the vertical and hoop strain of the shaft lining. Measurement studies have shown that: during the plastic stage of shaft construction period, with the release of hydration heat, the thermal expansion occurs in the concrete and the strain gauge, leading to tensile strain. In the earlier stage, the elastic modulus and strength of concrete increases rapidly. When the shaft lining temperature reaches its maximum, the cooling and growth in the freezing pressure make the hoop strain increase sharply. However, the hoop strain is at lower tensile or compressive value. In the early stage and mature stage, the strain change is mainly affected by temperature. In the thawing and post thawing period, the concrete strain is also primarily influenced by temperature change. During the measurement, when the maximum compressive strain is less than ultimate value, the shaft lining is in a safe state. To ensure the security of the shaft lining, the concrete strength growth and sidewall temperature should be controlled in the similar shaft condition. In addition, the reinforcement ratio should not be too small for the shaft lining in frozen bedrock. And further, the fiber reinforced concrete, shrinkage-compensating concrete and low hydration heat concrete technology can also be adopted to reduce the cracks as much as possible and to avoid penetrating cracks. For the soft aquifers in West China, the further field measurement is still needed to obtain the stress and deformation regularities of the shaft lining, which can not only provide a basis for security assessment of the shaft, but also guide its design and optimization to improve the design theory.

Multi-powder dam concrete with high performance and low adiabatic temperature rise

Based on the fluidity, strength, heat of hydration and loop crack resistance experiment of multi-powder paste, the components and proportion of multi-powder were optimized and the concrete properties were studied. The multi-powder consists of limestone powder, slag, fly ash and moderate heat Portland cement (PMH cement). The results show that the compressive strength of the multi-powder paste and mortar is close to those of PMH cement, fly ash paste and mortar currently used in dam concrete, yet the flexural strength is relatively higher. The multi-powder paste is featured by larger fluidity, lower heat of hydration and delayed cracking time. In comparison, less unit water consumption and cement is used in multi-powder concrete, and under premise of equal mechanical performance, deformation, thermal performance and durability, the adiabatic temperature rise at 28 d is reduced by 2 °C. In this way, the crack resistance is improved and it is feasible both technically and economically to produce HPC for dam concrete.

분쇄된 플라이애시를 혼합한 3성분계 시멘트의 유동특성

In this study, rheological properties of ternary system cement containing ground fly ash(F3, Blaine specific surface area 8,100 ㎠/g) were investigated using mini slump, coaxial cylinder viscometer and conduction calorimeter. In the results, the segregation resistance was observed at high W/B and PC area while the replacement ratio of F3 was increasing. The 2:5:3 system was shown in higher fluidity and lower hydration heat than 3:4:3 system. The segregation range of cement pastes occurred over 175 ㎜ in average diameter by mini slump and below 10 dynesec/㎠ of the plastic viscosity or below 50 cP of the yield stress by coaxial cylinder viscometer. It was observed that even if BFS and FA blended together admixture properties would remaine as they were separately. The properties of admixture would not be changed. On the above results, the decreased replacement ratio of OPC and increased replacement ratio of admixtures would be possible.

Hydration of coal–biomass fly ash cement

This paper presents possibilities of use of fly ashes from co-combustion bituminous coal and biomass in cement production process. Both fly ashes coming from co-combustion bituminous coal and biomass and the ones from bituminous coal combustion were analysed. The following properties of cement were tested: heat of hydration, Ca(OH) 2 content, unreacted C 3S content and microstructure. The results showed that fly ashes from co-combustion coal and biomass retard cement hydration. Cement samples containing coal-biomass fly ashes demonstrate adverse features like lower heat of hydration, higher Ca(OH) 2 content and lower rate of C 3S hydration in comparison to the ones containing fly ashes from bituminous coal. The incorporation of coal-biomass fly ashes in cement results in an increase of porosity of cement paste, leading to a microstructure of lower density.

Long term durability at 40°C of ecoefficient belite cement-mortar exposed to sulfate attack

The durability of cement-based materials with respect to exterior aggressions is one of the current priorities in civil engineering. Depending on their use, the cement-based materials can be exposed to different types of aggressive environments. For instance, damage to concrete structures in contact with a sulfate and saline environment are of most importance. Belite cements have excellent durability against determined expansive attacks and lower heat of hydration than that of Portland cements. These properties convert belite cements into good candidates for the immobilisation of low-level liquid waste and medium-level liquid waste. In this work, the authors present a long-term durability study at 40°C of a kind of belite cement from coal fly ash class C as alternative raw material. The aggressive was a 0·5 mol/l sodium sulfate (Na2SO4) solution, which is common in some evaporator concentrate solutions of medium-level liquid waste and low-level liquid waste. The attack was evaluated by means of flexural strength changes of mortars over 180 days. Furthermore, the changes in microstructure were followed by mercury intrusion porosimetry and mineralogy by X-ray diffraction.

Estimation of Adiabatic Temperature Rise of HVFA Concrete by Simplified Method

There is a large demand in consumption of fly ash due to current increase of coal power plants. Fly ash in concrete as admixture contributes to decrease heat of hydration. The larger amount of fly ash is in concrete, the lower heat of hydration is generated in the early age. This is caused by substitution of fly ash for cement, which implies that less cement is mixed in the concrete. Present paper describes adiabatic temperatures of the high volume fly ash concrete. The estimated adiabatic temperature in the concrete standard specification evaluates a little higher for amounts less than 200kg/m3 of cement in concrete, and an equation of adiabatic temperature for these amounts of cement is herein proposed.

Numerical Simulation of Autogenous Shrinkage of Eco-Friendly Blended Portland Cements Using a Multi-Component Hydration Model

Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry. Due to excellent durability, low heat of hydration, energy-saving, resource-conserving, and generally less expensive than ordinary Portland cement, blends Portland cements is used increasingly in construction industry. Both ecology benefit and economic benefit can be achieved by using blended Portland cement. Addition of blended components to cement, especially such as fly ash or silica fume, will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, based on the multi-component hydration model, a numerical program is built to predict autogenous shrinkage of ordinary Portland cement and blended Portland cement. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

Pozzolanic reaction of a spent fluid catalytic cracking catalyst in FCC-cement mortars

This work presents the relation between the pozzolanic activity, the hydration heat and the compressive strength developed by blended mortars containing 10 and 35% of a spent fluid catalytic cracking catalyst (FCC). The results show that, in comparison with 100% Portland cement mortar, a mortar with 10% FCC increases the hydration heat all over the period of testing. This hydration heat increasing is due to the pozzolanic effect, therefore the resulting compressive strength is higher than the reference mortar. Whereas, in a mortar with 35% of FCC, the hydration heat is higher than 100% PC mortar, until 10 h of testing. After this age, the substitution degree predominates over the pozzolanic activity, showing in this case, lower hydration heat and developing lower compressive strength than 100% PC mortar.

Some principles of service life calculation of reinforcements and in situ corrosion monitoring by sensors in the radioactive waste containers of El Cabril disposal (Spain)

Reinforced concrete is the most usual material used in engineered barriers in low-level nuclear waste disposal facilities. The record of modern concrete is no longer than about 100 years. During this time, it has been noticed that the material gives a good performance in many environments, however several chemical aggressive species in water, soil or the atmosphere may react with the cement mineralogical phases and perturb its integrity. El Cabril repository has a design life objective of longer than 300 years and therefore, these structures should maintain their main characteristics during this target service life. The potential aggressive conditions that the cement-based materials can suffer have been identified to be: carbonation, water permeation (leaching) and reinforcement corrosion. More unlikely may be the biological attack. Chlorides are not in the environment but they are inside the drums as part of analytical wastes. Vaults and containers are made of a very similar concrete composition while the mortar is specifically designed to be pumpable, with low hydration heat, low shrinkage and of low permeability. In this paper results of concrete characteristics are given as well as the monitoring of the behaviour of reinforcement corrosion parameters from 1995 on the same environmental conditions of the actual waste. This monitoring has been made in a buried structure with embedded sensors. The effect of temperature is commented.