A Binder of Phosphogypsum-Ground Granulated Blast Furnace Slag-Ordinary Portland Cement

A new hydraulic cementitious binder was developed by mainly utilizing industrial byproducts phosphogypsum（PG）and ground granulated blast furnace slag（GGBFS）with small addition of ordinary portland cement（OPC）.The hydration process and microstructure were studied by X-ray diffraction（XRD） and scanning electronic microscopy（SEM）.OPC hydrated first at early age to form primarily C-S-H gel,ettringite and calcium hydroxide（CH）.GGBFS activated by CH and sulfate ions hydrated continuously at later age,producing more and more hydration products,C-S-H gel and ettringite.Thus the paste developed a denser microstructure and its strength increased.The 28 d compressive strength of the mixture of 50%PG,46% GGBFS and 4%OPC exceeded 45 MPa.The setting time was faster and 3 d and 7 d strength were higher when the proportion of OPC increased.But the 28 d strength decreased when OPC exceeded 4%due to large amount of ettringite formed at late hydration age which damaged the microstructure.

Influence of Carbonation on Fatigue of Concrete with High Volume of Ground Granulated Blast-furnace Slag

The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the infl uence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.

Modeling Tensile Strength of Concrete on Partial Replacement of Ce­ment and Sand with Quarry Dust Ground Granulated Blast Furnace and Slag Silica Fumes

Tensile strength of concrete were examined on its partial replacement of cement and sand using ground granulated blast furnace and quarry dust.The study examines its behaviour at different dimensions.This is to monitor the variation effect of these parameters on the growth rates of tensile to the optimum curing age.These include non linear conditions of tensile state,non-elastic and its brittle behaviour at all times as it express zero conditions in tension.This means that it has the ability to with stand pull force.It also reflects its weak ability to handle shear stress thus tends to cause deformation in material as it has poor elasticity.The reflection of its brittle influence the rate of tensile behaviour from concrete ductility.These are known to be a material on modern mechanics of concrete.These are also considered as quasi brittle material.This behaviour was reflected as the system considered evaluating the growth rate of tensile strength that replaced cement and sand with these locally sourced addictives.The developed model monitor other reflected influential parameters such as variation of concrete porosity due it compaction in placements,tensile behaviour reflects these effect that subject it to mechanical properties of concrete.The study expressed the reaction of these parameters in the simulation,the evaluation of these affected the details variation of tensile growth rate at different water cement ratios and curing age.The tensile behaviour that was monitored are based on these factors in the study.The derived model were validated with the a researcher results[24],and both parameters developed best fits correlation.The study is imperative because the system expressed the behaviour of tensile strength from concrete at different dimensions.Experts can applied these concept to monitor tensile behaviour considering these parameters in its growth rates.

Sulfuric Acid Resistance of Concrete with Blast Furnace Slag Fine Aggregate

The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag have been examined. It was shown that by using the blast furnace slag fine aggregate and blast furnace slag fine powder, it is possible to enhance the resistance of mortar and concrete to sulfuric acid. The resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate in the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus, improving the resistance to sulfuric acid. Furthermore, it has been proved that the relationship between the erosion depth by sulfuric acid attack and the product of immersion period and concentration of sulfuric acid can be expressed linearly. However, this relationship is dependent on the type of materials of concrete.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part Two: Durability

This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na2CO3): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.

TiO_2 nanoparticles' effects on properties of concrete using ground granulated blast furnace slag as binder

In the present study, compressive strength, pore structure, thermal behavior and microstrncture characteristics of concrete containing ground granulated blast furnace slag and TiO2 nanoparticles as binder were investigated. Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were investigated. Al- though it negatively impacts the properties of concrete at early ages, ground granulated blast furnace slag up to 45 wt% was found to improve the physical and mechanical properties of concrete at later ages. TiO2 nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were measured. TiO2 nanoparticle as a partial replacement of cement up to 3 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca（OH）2 amount at the early age of hydration and hence increase compressive strength of concrete. The increased TiO2 nanoparticles＇ content of more than 3 wt% may cause reduced compressive strength because of the decreased crystalline Ca（OH）2 content required for C-S-H gel formation and unsuitable dispersed nanoparticles in the concrete matrix. TiO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and less-harm pores.

Effects of Al_2O_3 nanoparticles on properties of self compacting concrete with ground granulated blast furnace slag (GGBFS) as binder

In this work, strength assessments and percentage of water absorption of self compacting concrete containing ground granulated blast furnace slag （GGBFS） and A1203 nanoparticles as binder have been investigated. Portland cement was replaced by different amounts of GGBFS and the properties of concrete specimens were investigated. Although it negatively impacts the physical and mechanical properties of concrete at early ages of curing, GGBFS was found to improve the physical and mechanical properties of concrete up to 45 wt% at later ages. A1203 nanoparticles with the average particle size of 15 nm were added partially to concrete with the optimum content of GGBFS and physical and mechanical properties of the specimens were measured. A1203 nanoparticle as a partial replacement of cement up to 3.0 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca（OH）2 amount at the early ages and hence increase strength and improve the resistance to water permeability of concrete specimens. The increase of the A1203 nanoparticles＇ content by more than 3.0 wt% would cause the reduction of the strength because of the decreased crystalline Ca（OH）2 content required for C-S-H gel formation. Several empirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of the peaks related to hydrated products in X-ray diffraction results, all indicate that A1203 nanoparticles could improve mechanical and physical properties of the concrete specimens.

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.

Effects of Steel Slag Powder on Workability and Durability of Concrete

The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag（GGBFS） alone or with a combined admixture of GGBFS-steel slag powder were investigated by X-ray diffraction（XRD）. Furthermore, the mechanism of chemically activated steel slag powder was also studied. The experimental results showed that when steel slag powder was added to concrete, the slumps through the same time were lower. The initial and fi nal setting times were slightly retarded. The dry shrinkages were lower, and the abrasion resistance was better. The chemically activated steel slag powder could improve compressive strengths, resistance to chloride permeation and water permeation, as well as carbonization resistance. XRD patterns indicated that the activators enhanced the formation of calcium silicate hydrate（C-S-H） gel and ettringite（AFt）. This research contributes to sustainable disposal of wastes and has the potential to provide several important environmental benefi ts.

Properties and Mechanism on Flexural Fatigue of Polypropylene Fiber Reinforced Concrete Containing Slag

Properties and mechanism were investigated on flexural fatigue of concrete containing polypropylene fibers and ground granulated blast furnace slag（GGBFS）.Four polypropylene fibers’volume fractions and five slag proportions were considered.An experiment was conducted to obtain the fatigue lives at three stress levels in 20 Hz frequency and at a constant stress level of 0.59 in four frequency respectively.Mechanism and evaluation were investigated based on the experimental data.Fatigue life span models were established.The results show that the addition of polypropylene fibers improves the flexural fatigue cumulative strength and fatigue life span.It is proposed that the slag particles and hydrated products improve Interfacial Transition Zone（ITZ）structure and benefit flexural fatigue performance.A composite reinforce effect is found with the incorporation of slag and polypropylene fibers.The optimum mixture contents 55%slag with 0.6%polypropylene fiber for the cumulative fatigue stress.Fatigue properties are decreased as the stress level increasing,the higher frequency reduces the fatigue strength more than lower frequency at a constant stress level.

Tests on Alkali-Activated Slag Foamed Concrete with Various Water-Binder Ratios and Substitution Levels of Fly Ash

To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.

Optimum Level of Replacement Slag in OPC-Slag Mortars

The present paper reports the testing of 14 OPC-slag mortars and 2 controls OPC and slag mortars. The main aim is to determine the optimum level of replacement slag for achievement to the highest early strength with reasonable flow. Variable was the level of GGBFS in the binder. In this experimental work, two types of sands were used that are： silica and mining sands. It is determined that the optimum level of replacement slag is 40% and use of silica sand in OPC is preferable to mining sand and reversely, use of mining sand is preferred in GG100 to silica sand. All mortars had W/B and S/B 0.33 and 2.25, respectively.

Evaluating Simultaneous Impact of Slag and Tire Rubber Powder on Mechanical Characteristics and Durability of Concrete

In this experimental study,the impact of Portland cement replacement by ground granulated blast furnace slag(GGBFS)and micronized rubber powder(MRP)on the compressive,flexural,tensile strengths,and rapid chloride migration test(RCMT)of concrete were assessed.In this study,samples with different binder content and water to binder ratios,including the MRP with the substitution levels of 0%,2.5%and 5%,and the GGBFS with the substitution ratios of 0%,20%and 40%by weight of Portland cement were made.According to the results,in the samples containing slag and rubber powder in the early ages,on average,a 12.2%decrease in the mechanical characteristics of concrete was observed,nonetheless with raising the age of the samples,the impact of slag on reducing the porosity of concrete lowered the negative impact of rubber powder.Regarding durability characteristics,the RCMT results of the samples were enhanced by using rubber powder because of its insulation impact.Moreover,adding slag into the MRP-included mixtures results in a 23%reduction in the migration rate of the chloride ion averagely.At last,four mathematical statements were derived for the mechanical and durability of concrete containing the MRP and GGBFS utilizing the genetic programming method.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part One: Hydration and Mechanical Properties

High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na2CO3 into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.

钢渣粉对高强混凝土力学性能和耐久性的影响

超细矿渣是制备高强混凝土的优质矿物掺合料,但是超细矿渣水化放热量较大、凝结较快,不利于高强混凝土的强度和耐久性发展。而钢渣粉具有延缓水泥水化、降低水化放热的作用,可以充当“缓凝剂”。通过在高强混凝土中复掺钢渣粉和超细矿渣,研究了钢渣粉对高强混凝土性能的影响。结果表明复掺15%钢渣粉时初凝时间和终凝时间分别比纯水泥组延长53.0%和35.9%。同时早期强度降低,但与超细矿渣复掺后28 d和90 d强度分别为77.3 MPa和84.6 MPa,比对照组高4.3%和8.6%。此外,钢渣粉有效降低了高强混凝土的绝热温升和自收缩率。单掺15%超细矿渣时7 d自收缩率为1189.63×10^(-6),约为纯水泥组的2.5倍;复掺15%钢渣粉时自收缩率为211.62×10^(-6),比纯水泥组降低了52%。复掺钢渣粉的高强混凝土与纯水泥制备的混凝土的抗氯离子渗透性等级均为“低”。

热养护对大体积混凝土不同活性矿物掺合料早期水化性能的影响

研究了大体积混凝土中粉煤灰和矿粉在热养护条件下对水泥早期抗压强度的影响,并通过水化热、XRD以及TGA等技术手段阐述了水化反应过程。结果表明:常温时,粉煤灰和矿粉加入均会大幅度降低早期强度;热养护时,粉煤灰-水泥体系的早期强度仍远低于空白组;但随着矿粉用量的增加和热养护温度的升高,体系早期强度与空白组的差距逐渐减小;50℃养护时,矿粉-水泥体系的早期强度高于空白组。这说明在热激发条件下,粉煤灰的早期火山灰反应仍然有限,但矿粉的早期水化活性显著提高,通过火山灰反应和自水化反应完成水化产物的积累。

磷石膏协同多元固废制备矿山充填材料

为解决磷石膏利用率低、对环境危害大与低成本矿山充填材料研制的问题,本文以粉煤灰、钢渣、高炉矿渣为胶凝材料组分,协同磷石膏制备一种新型的磷石膏基矿山充填材料。通过抗压强度、流动度、凝结时间、浸出毒性和微观试验研究了充填材料的工程与环境特性。结果表明:所研制的矿山充填材料的抗压强度、流动度、凝结时间均能满足规范,达到工程应用需求;在养护28 d后,充填材料的重金属元素的浸出浓度都可以满足地下水Ⅲ级标准的要求,不会污染环境和危害人体健康。当钢渣和高炉矿渣的掺量逐渐增加时,抗压强度逐渐升高,流动度和凝结时间逐渐降低;充填材料中主要的水化产物是钙矾石和C—(A)—S—H凝胶,两者都为充填材料提供了主要的强度,且C—(A)—S—H凝胶可以包裹住重金属离子。

掺粉煤灰和矿渣粉大流动度混凝土的碳化性能

研究了复掺Ⅱ级粉煤灰和同等细度矿渣粉且同时加入高效减水剂的大流动度 (约1 80mm)混凝土的抗碳化性能 .试验中改变了取代水泥量 (最大为 80 % )及掺合料中粉煤灰和矿渣粉的比例等条件 .混凝土碳化深度随时间的变化可用幂函数d =atb 表示 ,其中b值大多位于 0 .3～ 0 .4.复掺可使取代水泥量提高 .对设计寿命为 50年的混凝土 ,在其他性能满足工程要求的条件下 ,仅就碳化性能而言 ,可掺加 40 %的粉煤灰 .若采用粉煤灰与矿渣粉复掺 ,则在掺合料总掺量分别为 60 % ,70 %及 80 %时 ,相应地可掺加 40 % ,3 0 %及 1 5%的粉煤灰 .

高性能矿渣基复合掺合料的研究

矿渣粉较高的价格以及大掺量矿渣混凝土的泌水一直是其在建筑工程中大规模应用的主要障碍。本研究选用转炉钢渣粉、石灰石粉和粉煤灰作为矿渣基掺合料的辅助原料,重点考察了掺合料组成与性能之间的关系。结果表明:转炉钢渣粉具有减水增密和抵抗泌水的突出功效。石灰石粉具有一定的早强作用。粉煤灰对胶砂流动度和强度发展有不良影响,但混凝土试验结果与之有所不同。当复合10%～20%转炉钢渣的矿渣基掺合料在混凝土中的掺量高达50%时,其新拌混凝土流动性和稳定性俱佳,28d抗压强度稍优于纯矿渣粉,而生产成本可降低30%以上。实现矿渣基复合掺合料在低成本前提下高性能化的关键在于掺合料在颗粒级配上的优化以及它们对水化进程的协同促进作用。