Mechanical and Chloride Diffusion Behavior of Kaolinite Clay Modified Cement-Based Material

The effects of kaolinite clay on the microstructure (pore structure, internal structure) and mechanical properties (workability, early-age and long-term flexural strength, chloride diffusion property) of the cementitious composites were tested. It is shown that the addition of clay improves the micro-pore structure in the cement paste and limits the introduction of chloride ions. As a result, it is suggested that the kaolinite clay would act as both filler and accelerator of cement hydration. Compared with the control specimen, the flexural strength of cement paste with 1% kaolinite clay increased by 30.41%, 39.04%, 36.27% and 38.32% at 1, 3, 7 and 90 curing ages, respectively. The 28-day flexural strength increased slightly. It is observed that the clay modified cement mortar has lower chloride diffusion coefficient values compared to the plain mortar, and the 28-day DCl of cement mortar decreased by 53.03% with 5% clay. Compared with the controlled sample, the increase in compressive strength and the reduction in chloride diffusion coefficient of the concrete with 5% clay addition is 28.4% and 18.87% respectively. The chloride diffusion coefficient of concrete decreases with the amount of clay addition exponentially. The 28-day compressive strength increases linearly with the chloride diffusion coefficient of the concrete.     

Preparation of Cementitious Material Based onAlkali GGBS Manganese Alloy Slag System

Manganese alloy slag is an industrial waste produced from manufacture of manganese alloy. Recent years environment pollution of manganese slag has been becoming heavier and heavier with the development of manganese industry. Aiming to sort out this problem, combination of manganese slag and ground granulated blastfurnace slag (GGBS) were applied to prepare alkali activated cementitious material. Compressive strength and flexural strength of cementitious material prepared with combination of alkali slag manganese slag were measured. And micro structure of hydration production was investigated by scanning electro microscope (SEM). It was shown that the flexural and compressive strength of cementitious material with alkali GGBS manganese slag system were decreased with the increase of replacement of GGBS by manganese slag. The increase of the fineness of manganese slag was favorable for strength improvement of the alkali GGBS manganese slag material. It was concluded that ground manganese slag had hydraulic activity in alkali activated cementitious material and the activity was lower than that of GGBS.     

Influence of Rubber Powder Dosage on Performance of Cement Mortar

A number of rubber cement dosage specimens that rubber powder dosage different were obtained using same cement, water and fine aggregates, by adjusting the dosage of rubber powder. Then it was used to research the influence of rubber powder dosage on performance of cement mortar by measuring its liquidity, strength and toughness. The results show that: when water-cement ratio was equal and rubber powder replacing the same volume sand, the fluidity of cement mortar almost linear increased with rubber powder dosage increasing. With dosage of rubber powder increasing, compressive strength and flexural strength of 7 days and 28 days of cement mortar reduced, but toughness and wear resistant present linear growth trend when dosage of rubber powder less 30%.     

Hydration Heat Evolution and Setting Performance of Alkali-slag Cement Activated with Water Glass

The effect of dosage and modulus of water glass on the early hydration and setting performances of alkali-slag cement is very important. The variation of hydration heat and setting time and compressive strength of the alkali-slag cement with its modulus and alkali content are studied. It is found that with the increase of modulus, the hydration heat decreases and the setting time prolongs gradually, and the compressive strength increases first, then decreases. When the dosage of Na2O increases, the hydration heat increases. And the setting time increases slightly and the compressive strength shows the trend of increasing. The reasonable modulus of water glass Ms is about 1.0~2.0, and the dosage is about 3%~6% of the mass of slag.     

Hydraulic potential stimulation and bricks preparation of magnesium slag

The hydraulic potential stimulation of magnesium is significant to its direct utilization. In this paper, magnesium slag which is the main material, and some slag and activator are used to prepare cementitious material and bricks, and the influences of different activators on the hydraulic properties are also investigated. Experiments show a certain hydraulic potential of magnesium slag but with a low strength, however, the compressive strength soars from 1.8 MPa to 27 MPa after composing it with a small amount of blast-furnace slag. The early strength of magnesium slag-blastfurnace slag binder is affected by NaOH, while the gypsum affects the binder’s later strength. Bricks conforming to standard MU20 are successfully fabricated by 80% magnesium and 20% blast furnace slag, after activated, with extra 5% desulfurized gypsum.     

Properties of Cemented Copper Tailings Backfill with Steel Slag-Blast Furnace Slag-Fluorgypsum-Based Cementation Material

Cement is a traditional tailings cementation material, which causing the high tailings backfill cost. However, the utilization rate of industrial waste residue, such as steel slag and fluorgypsum, is low. So the steel slag-blast furnace slag-fluorgypsum-based cementation materials preparation with industrial waste residue substitutes for cement. As a result, its cementation tailings performances must be studied. According to mortar fluidity and bleeding quantity of tailing cementation slurry at different time and compressive strength change trend at different hydration ages, the performance of steel slag-blast furnace slag-fluorgypsum-based cementation materials is significantly better than P·O42.5 grade cement and two kinds of commonly used cementation agents in China. After soaking for three days, the pH value of these tailings solidification bodies leaching liquid is less than 9.0, which is much lower than the pH values of three kinds of high alkaline tailings cementation materials mentioned before. Leaching liquid fluorine ion concentration is extremely low. With less impact on environment. SEM analysis also show that these tailings solidification bodies mixing with the steel slag-blast furnace slag-fluorgypsum-based cementation materials have relatively dense microstructure.     

Properties of Portland Cement with Magnesium Slag

Two kinds of magnesium slag from different places were added in clinker respectively to manufacture portland cement, and the essential properties of cement, such as water requirement of normal consistency, setting time and strength, were studied. The influence of magnesium slag on the drying shrinkage of portland cement was investigated. Meanwhile, effects of magnesium slag in portland cement were analyzed on the basis of XRD, DSC/TG and SEM microscopic experiments. The results show: magnesium slag plays roles in water-reducing and set-retarding as a composite material of cement; when the contents of magnesium slag range from 10%～30% (weight ratio) and 35%～40% (weight ratio), cement samples reach Composite Portland Cement 42.5R and 32.5R standard, separately; the drying shrinkage of mortar can be restrained as the contents of magnesium slag range from 30%～40%; and the structure of cement pastes is more compacted as magnesium slag reacts with the hydrations of clinker.     

Sulphate Attack Resistance of the Concrete with Additives and Its Assessment

The influence of three kinds of additives: silica fume,slag and fly ash on the sulphate attack resistance of concrete were studied.The experiment results show that these three kinds of additives can improve sulphate attack resistance of the concrete and the order of their efficiency from high to low is silica fume,slag and fly ash;the development of mortar expansion value is closely related to the degree of sulphate attack resistance of the concrete;integrated assessing two concrete properties: mortar expansion value and compressive strength ratio can more exactly assess the sulphate attack resistance of the concrete.     

Influence of Ca(OH)2 on Strength of Low Proportional Cemented Soil

Laboratory experimental research is performed by strengthing three different types of soil with low proportional cement to test the unconfined compressive strength of such cemented soil under different dosages of Ca(OH)2 and the different ages. The variation rules and causes of the unconfined compressive strength of these three types of age-different cemented soil with increasing the dosage of Ca(OH)2 are analyzed. The results shows that the intensity of red clay cement improves most obviously with Ca(OH)2 content increased, followed by silty clay, and sand is the weakest. The reason is that the fineness of the soil affect the strength of the cement greatly. The finer the soil, the more clay minerals in soil. The increase in Ca(OH)2 content promotes the ion exchange and the occurrence of volcanic ash, which improves the strength of cemented soil. Among the three types of soil in this experiment, the fineness of red clay particles is the best, so the intensity of red clay cement improves most obviously with Ca(OH)2 content increased.     

Strength and Microstructure of Sulphoaluminate Cement Containing Ultra- Fine CaCO3

The existence of ettringite in sulphoaluminate cement hardened paste is mainly in the form of pole-like crystal,which causes unfavorable effect on the cement.In this paper the strength and microstructure of the sulphoaluminate cement containing ultra-fine CaCO_3 weze discussed.Experimet results show that the strength of sulphoaluminate cement was obviously improved by adding 3% of ultra-fine CaCO_3.After curing for 28d,the compressive strength of cement paste and mortar is 100.6MPa and 94.1MPa respectively,and the bending strength of the mortar reached 12.5MPa.SEM study on hardened paste of sulphoaluminate cement containing ultra-fine CaCO_3 showed that its structure was dense and homogeneous,there was hardly any massive crystall detected.     

Experimental Study of Ratio Between Splitting Tensile Strength and Compressive Strength for PVA Fiber Cementitious Composites

An experimental study of the splitting tensile strength and compressive strength were carried out. Effects of PVA fiber was analyzed on ratio between splitting tensile strength and compressive strength. The dimensions of cubic specimens were 100 mm×100 mm ×100 mm. PVA fiber were added at the volume fractions of 0, 0.5%, 1%, 1.5%, 2% and the fly ash content were 30%, 50%. The test results indicate that, the compressive strength varies very little after incorporation with PVA fiber, however, the splitting tensile strength increases from 42.64% to 135.12% and the ratio between splitting tensile strength and compressive strength increases from 36.82% to 134.27%. What's more, the compressive strength of cementitious composite including fly ash at the ratio of 30% is 20% higher than that of 50%,and there is no obvious improvement on the splitting tensile strength with the change of fly ash content. This paper also shows that the compressive test cube of PVA fiber cementitious composites has multiple cracks and is hardly crumbled in the degradation process, and then the compressive toughness can be enhanced significantly.     

Spalling and Physical Properties of Cement-Based Material Under Instantaneous High Temperature

Cement-based material has different spalling and physical properties after exposing to different high temperatures. The spalling and physical properties of cement-based material with different additives after exposing to instantaneous high temperature were analyzed. The results show that: all samples have no spalling both at 100℃ and 300℃, but spalling completely at 600℃. The compressive strength and flexural strength of the cement-based material at 100℃ decrease by the rate of 15% and 30%, and the value at 300℃ is close to that at room temperature and decreases rapidly after exposing to 600℃. Both the compressive and the flexural strength of samples with 20% slag powder and 10% silica fume increase with the increase of the temperature when the temperature is below 300℃. SEM reflects that after exposing to 600℃ for 2 hours, C-S-H has changed into a looser structure, and the continuously cement paste is separated into segments.     

A Primary Investigation on Concrete Made from Iron and Steel Slags for Building Ecological Artifical Reefs

A method of orthogonal test was used to optimize the strength of the cementitious material for preparing the concrete of high-strength artifical reefs.The results show that with the ratio of iron slag:steel slag=7:1,and when 10% cement clinker and 10% gypsum of Flue Gas Desulfurization Waste (FGDW) was mixed with 80% iron and steel slags powder,the mixed cementitious material had an optimized strength.The optimized specific surface area are 480 m 2/kg and 550 m 2/kg for iron slag and steel slag powder respectively.The ordinary portland cement can be totally substituted by such a mixed cementitious material with iron and steel slags as its major components in preparing the concrete for building high-strength artificial reefs.A concrete with a compressive strengh over 65MPa can be prepared by using such a mixture as a cementitious material and steel slag grains as its fine and coarse aggregats which have been stubilized by a hot-simmering method. Hydration processes of net slurry were analysized by XRD and SEM methods. The results show that the hydration products in the system are mainly AFt and C-S-H gel. The results also show that the pozzolanic reaction of iron slags could be largely promoted by the coordinations of steel slags,clinker and FGDW.     

The Effect of the Components of VAE Latex Modified Cementitious Compound Waterproofing Coating on Its Properties

In this paper the effect of the components of VAE latex modified cementitious waterproofing coating on its properties is studied. The results show that the tensile strength, bond strength and water resistance of the compound water proofing coating increase greatly in comparison with those of the coating without addition of cement. This compound coating is a new type of waterproofing material with excellent performance.     

STUDY ON THE LOW TEMPERATURE CALCINATION AND THE BEHAVIOUR OF STEEL SLAG COLOUR CLINKER CEMENT

The colourcd clinker cement which fired directly from kiln has the advantages of low cost,bright colour and good colour durability.This paper studies the possibility of using calcium flouridc and gypsum combined mineralizer to calcine the col-outed clindcr cement at low temperature.Different methods such as X-ray diffraction ana ysis,scanning electron microscopy,infrared spectra analysis,combined water content chemical asysis,compressive strength test and so on arc used to study the clinder minerals,the colour,the physical and mechanics properties and behaviour of the coloured clinker cement which made both with high quality raw materials and with electric furnace reduced slag additive.     

Activation and Toxicity of Slag-fly Ash-fluorgypsum Cementitious Material

Effect and mechanism of activation of activator to fluorgypsum, strength, softening coefficient and leaching toxicity of composite cementitious material are studied. Through activation testing of NaOH, Na2SO4 and NaF, the optimum adding quantity was defined as 1%. On the basis of it, 80% fluorgypsum was further processed to improve its quality with slag, fly ash and clinker. With 1% Na2SO4, 25% slag, 5% fly ash and 89% fluorgypsum, the cementitious material properties were excellent; the 28-day compressive strength could reach 12.25 MPa; the softening coefficient was 0.70; and the concentration of fluoride could be reduced to 0.7485 mg/L. The analysis of SEM and XRD show that gypsum, a few calcium silicate hydrate, ettringite and calcium fluoride are filled and packed each other, which hampers water enter particle structures, increases the water resistance of cementitious material and reduces leaching toxicity of cementitious material.     

Experimental Investigation of Stabilized Soft Soil by New GSC

Soft clay is stabilized by desulphurization gypsum and steel slag-slag blended cementitious materials (GSC), which can not only reuse industrial waste and decrease second pollution, but also can conserve mineral resources and protect natural ecology. The variation of unconfined compressive strength of the clay improved by GSC with different mixing ratios and water-GSC ratio and ages was studied through the laboratory experiments. The long-term strength of stabilized soil is predicted with GSC by quasi-water-GSC ratio. The results show that the more the mixing ratios is, the better the stabilized effect of soft soil is. With increase of curing period, the strength increasing of GSC-soil is consistent with cement-soil, and it has lower strength in the early stage. When mixing ratios of GSC is more than those of cement by 3%, if the water-GSC ratio is less than those of cement, it has the higher strength than cement-soil, after 28 days. The results show that GSC stabilized soil is feasible and it can meet the demand of cure strength.     

Preliminary Discussion on Mixing Design of Porous Concrete

Porous concrete is an eco-concrete with high porosity and high strength,whose application was restricted to some extent,because there is lack of appropriate and unitive mixing design method.According to the features of porous concrete,proportion design idea of porous concrete whose major design parameter was porosity and strength was satisfied by changing variety of cementing material and aggregate size.The design method of porous concrete was that the raw materials were selected according to design requirement at first,secondly,aggregate dosage per unit volume of porous concrete was calculated,thirdly,dosage of cementing material was calculated by apparent density of aggregate and porosity of design requirement,finally,cement dosage of the unit physical volume and water dosage were calculated by water cement ratio deter mined by requirement of forming process.The test result indicated that this mixing design method of porous concrete was reliable and feasible.     

Effects of Cement Additives on Properties of CSA Cement from MSWI

Municipal solid waste incineration fly ash (MSWI) was successfully used as raw material in sintering and preparing a calcium sulphoaluminate (CSA) cement clinker in laboratory. The effects of different types and different addition percentages of cement additives on compressive strength and hydration properties were investigated. The results showed that lime (LI) powder / slag (SL) powder was compatible in CSA cement system while the activities of fly ash(FA)/ MSWI was low. Adding these four types of cement additives in CSA cement system respectively, there were negative effects on compressive strengths of hardened cement at early age while LI/SL improved the compressive strength at later age. The performance of combined additives was better, especially, the specimens with 10%LI+10%SL, 10%LI+10%MSWI, and 5%LI+15%SL.     

Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened With Ferrocement Mortar

Experimental research on flexural behavior of the different grade RC beams strengthened with ferrocement mortar through six RC beams is carried out. The matching of original component concrete to the composite mortar strength rank is studied and its influence on bending strength, the crack-resisting capacity and the bending stiffness of RC beams is analyzed. Based on plane cross-section assumption and the experimental results, the formulas of the theoretical ultimate strength capacity and stiffness are brought forward. The calculated results fit well with the experimental results, to provide a theoretical reference for actual engineering designs.