A strength model for cement-stabilized mud subjected to various curing temperatures and its early-stage quality control

The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength.However,the strength development model is not mature for the extremely early stages.In addition,there is a lack of studies on quality control methods based on early-stage strength development.This paper presents a strength model for cement-stabilized mud to address these gaps,considering various curing temperatures and early-stage behaviors.In this study,a series of laboratory experiments was conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures.The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength.The proposed model,which combines a three-step conversion process and a hyperbolic model at the reference temperature,enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures.With this model,a practical early quality control method is introduced for applying cement-stabilized mud in field projects.The back-analysis parameters obtained from a 36-h investigation at temperature of 60C demonstrated a sufficient accuracy in predicting strength levels in practical applications.

Study on influence factors of cement-stabilized soil compressive strength

The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.

Review on the mesoscale characterization of cement-stabilized macadam materials

The base layer constructed by cement-stabilized macadam(CSM)has been widely used in highway construction due to its low elasticity deformation and high carrying capacity.As a bearing layer,the CSM base is not exempt from fatigue cracking under cyclic loading in the service process.Cracks in the base will create irreversible structural and functional deficiencies,such as the potential for reflective cracking of subsequently placed asphalt concrete overlays.The fracture of the base will shorten the service life of the pavement.The quality of the CSM base is directly related to the bearing capacity and integrity of the whole pavement structure.It is of practical significance to further study the fatigue failure behavior of CSM material for the long-term performance of the pavement.The CSM material is a typical heterogeneous multiphase composite.On the mesoscale,CSM consists of aggregate,cement mortar,pores,and the interface transitional zone(ITZ).On the microscale,the hardened mortar contains a large number of capillary pores,unhydrated particles,hydrated crystals,etc.,which makes the spatial distribution of its material properties stochastic.In addition,cement hydration,dry shrinkage,and temperature shrinkage can also produce micro-crack defects in cement mortar.These microcracks will have crossscale evolution under load,resulting in structural fracture.Macroscopic complex deformation and mechanical response are the reflections of its microscopic and even mesoscale composition and structure.This study summarized the existing studies on the mesoscopic properties of CSM materials,respectively from the three aspects of mesostructure,structural characterization,and mesoscale fatigue damage analysis,to help the development of long-life pavement.The future research direction is to explore the mesoscale characteristics of CSM using multiscale representation and analysis methods,to establish the connection between mesoscale characteristics and macroscopic mechanical properties.

Composition design and performance evaluation of rubber-particle cement-stabilized gravel

To improve the mechanical properties and durability of the cement-stabilized base,rubber particles of three different sizes and with three different contents were optimally selected,the evolution laws of the mechanical strength and toughness of rubber-particle cement-stabilized gravel(RCSG)under different schemes were determined,and the optimal particle size and content of rubber particles were obtained.On this basis,the durability of the RCSG base was clarified.The results show that with an increase in the rubber particle size and content,the mechanical strength of RCSG gradually decreased,whereas the toughness and transverse deformation ability gradually increased.1%content and 2–4 mm sized RCSG can better balance the relationship between mechanical strength and toughness.The 7 d unconfined compressive strength was 17.7%higher than that of the 4–8 mm RCSG.The 28 d toughness index and ultimate splitting strain can be increased by 9.8%and 6.3 times,respectively,compared with ordinary cement-stabilized gravel(CSG).In terms of durability,compared with CSG,RCSG showed a 3.7%increase in the water stability property of cement-stabilized base with 1%content and 2–4 mm rubber particles,5.5%increase in the frozen coefficient,and 80.6%and 37.9%increase in the fatigue life at 0.70 and 0.85 stress ratio levels,respectively.

Polyvinyl alcohol fiber cement-stabilized macadam:A review and performance evaluation

This review evaluated research results on polyvinyl alcohol fiber cement-stabilized macadam(PVA-FCSM)to further improve the long-term durability of road structures and promote its in-depth study and high-quality application.The suitable PVA fiber technical indexes for ordinary cement-stabilized macadam(CSM)were recommended.The difference in the mechanical properties between CSM and PVA-FCSM was described.The extent to which PVA fibers enhance the durability of CSM were clarified.Additionally,the mechanism of enhancement of CSM by PVA fibers was revealed.Finally,the performance of each type of fiber cement-stabilized macadam(FCSM)was compared and evaluated.The results indicated that the suggested PVA fiber length and content for CSM were 12-30 mm and 0.6-1.2 kg/m^(3),respectively.At different ages,the mean degree of improvement in the unconfined compressive strength was 14%,20%,and 14%,that in the compressive resilience modulus was 8%,11%,and 6%,and that in the splitting strength was 29%,15%,and 22%,respectively.At different ages,the mean degree of decreased in the dry shrinkage coefficient was 21%,16%,and 15%and that in the temperature shrinkage coefficient(20℃-30℃)was 23%,23%,and 18%,respectively.The coefficients increased with extended curing age.Moreover,at the same stress level,PVA-FCSM has a higher fatigue life compared to CSM.The bridging effect,high strength,and high modulus of PVA fiber enhance the strength and anti-cracking of CSM.The recommended fiber type for CSM is PVA fiber.

Structural characteristics of cement-stabilized soil bases with 3D finite element method

Cement-stabilized soil bases have been widely used in expressways due to its high strength,appropriate stiffness,good water resistance,and frost resistance.So far,the structural characteristics and mechanical behaviors of cement-stabilized soil bases were not investigated so much.In this paper,the 3D elastic-plastic finite element method(FEM)was used to analyze the mechanical behaviors and structural characteristics of cementstabilized soil bases from construction to operation.The pavement filling and the traffic loading processes were simulated,and a contact model was used to simulate the contact behavior between each layer of the pavement.Considering the construction process,the structural characteristics and mechanical behaviors of cementstabilized soil bases were studied under asphalt-concrete pavement conditions.Furthermore,the general rules of deformations and stresses in cement-stabilized soil bases under different conditions were discussed,and some suggestions were put forward for the design and construction of cement-stabilized soil bases.

Assessment of Cement-Lime as Stabilizer on Mud Bricks

The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric analysis was used to characterize the various stabilizers and the clay used, and tests of resistance and water absorption were also carried out. The clay was found to be an aluminosilicate (15.55% to 17.17% Al2O3 and 42.12% to 44.15% SiO2). The lime contains 90.84% CaO and the cement has 17.80% SiO2, 3.46% Al2O3, 2.43% Fe2O3 and 58.47% CaO in the combined form of tricalcium silicate, dicalcium silicate, tricalcium aluminate and ferro-tetra calcium aluminate. The results showed that the insertion of locally available stabilizers (lime and cement) improved the strength of the material by almost 80% when the lime was increased from 0% to 14% for 14 days. For compressed cement, a 65% increase in strength was observed under the same conditions. Strength increases with drying time, with a 52% increase in strength at 28 days compared to 14 days. Furthermore, compressed cement bricks have a more compact structure, absorbing very little water (32%). In view of all these results, cement appears to be the best stabilizer, and compression improves compressive strength and reduces water absorption.

Strength characteristics of modified polypropylene fiber and cement-reinforced loess

The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified polypropylene(MPP) fiber and cement,samples were prepared with six different fiber contents,three different cement contents,three different curing periods and three kinds of fiber length.The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength(UCS),the splitting tensile strength and the compressive resilient modulus.The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days.With an increase in cement content,the specimens exhibited brittle fracture.However,the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic.The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm,for which the unconfined compressive strength and tensile strength reached their maxima.Based on the analysis of failure properties,cement-reinforced loess specimens were susceptible to brittle damage under pressure,and the effect of modified polypropylene fiber as the connecting "bridge" could help the specimens achieve a satisfactory level of ductility when under pressure.

Modification of nanoparticles for the strength enhancing of cementstabilized dredged sludge

This paper investigates the effectiveness of nano-modification on the strength enhancement of cementstabilized dredged sludge(CDS).Three types of nanoparticles including nano-SiO2(NS),nano-Al2O3(NA)and nano-MgO(NM)were used as cement admixtures for dredged sludge stabilization.Effects of single nanoparticle content,mass ratio of composite nanoparticles and curing time on the strength development of CDS were evaluated via a series of unconfined compressive strength(UCS)tests.The pH evolutions of CDS caused by nanoparticles were also examined by a range of pH tests.Furthermore,micromechanisms reflecting the strength evolutions were analyzed by performing scanning electron microscopy(SEM)and X-ray diffraction(XRD)tests.The results indicated that adding nanoparticles can significantly improve the UCS of CDS.For single nano-modification,the optimum contents of NS,NA and NM were 4%e6%,6%and 8%,which can increase the 7-and 28-d UCSs of CDS by 38%and 50%,17%and 35%,65%and 67%,respectively.Compared with single nano-modification,composite nano-modifications were more effective in improving the strength gain of CDS.The optimum mass ratios of composite nanoparticles,namely NS/NA,NS/NM and NA/NM,were 9/1,3/7 and 3/7,respectively.Based on the strength growth rate,the composite nanoparticles with NS/NM of 3/7 were highly recommended.The addition of nanoparticles obviously affected the pH evolution of CDS,which was mainly determined by the difference of OHproduction and consumption inside nano-modified CDS.The microstructural analysis revealed that C-S-H and C-A-H gels are the main cementitious products,and the addition of nanoparticles can obviously contribute to a denser and more homogenous microstructure of CDS.

The Stabilizing Granular Soil with Slow-setting and Slight-expansive Cement

According to the characteristics of granular soil,the technological requirements of the special-purpose cement for stabilizing granular soil are put forward to meet the demands of implementation of highway base engineering.A kind of slow-setting and slight-expansive cement is developed by the cross experiment method in slag-clinker-gypsum-alkaline system,the final setting time of the cement can be prolonged to 8h,and it has properties of low dry shrinkage,high flexural strength and good crack resistance.The strength of granular soil stabilized by the cement is increased by 20% compared with that stabilized by Chinese 425-Grade slag cement.

Exploring alkali-source,pore-filling and cementation damage effects in cemented clay with typical industrial waste binders

Various industrial waste binders(IWBs)are being recycled in soil stabilization to save cement consumption.However,the coupled effects brought out by combined IWBs on stabilized soils are still unclear.IWBs are categorized into two typical categories(IWB-A and IWB-B)referring to their chemical role in this study.The alkali-source effect,pore-filling effect and cementation damage effect by IWBs in soil stabilization are explored.A series of mechanical and microscopic tests is performed on stabilized clay with different proportions of IWB-A and IWB-B.Moreover,initial water contents and cement contents of cement-stabilized clay are varied to examine the evolution of coupled effect with void ratio and cementation level.The results indicate that the alkali-source effect strengthens the cementation bonds and increases the early strength by 0.5e1.3 times,whereas the pore-filling effect improves the microfabric especially for the specimen with a large void ratio.The alkali-source effect increases soil cohesion cu at the pre-yield stage,and the pore-filling effect increases frictional angle 4u at the post-yield stage.The cementation damage effect is remarkable at a low void ratio,which may result in many extruded pores among soil aggregates.The strength evolution with IWB proportions can be well stimulated by considering the coupled alkali-source effect,pore-filling effect and cementation damage effect.The optimal proportion of IWBs corresponds to an optimal combination of coupled effect.

Effect of superabsorbent polymer on mechanical properties of cement stabilized base and its mechanism

Superabsorbent polymers(SAPs)are cross-linked polymers that can absorb and retain large amounts of water.In recent years,a growing interest was seen in applying SAPs in concrete to improve its performance due to its efficiency in mitigating shrinkage.This paper presents findings in a study on effect of SAPs on performance of cement-treated base(CTB),using the experience of internal curing of concrete.CTB specimens with and without SAPs were prepared and tested in the laboratory.Tests conducted include mechanical property testing,dry shrinkage testing,differential thermal analysis,mercury intrusion porosimetry and scanning electron microscope testing.It was found that 7-day and 28-day unconfined compressive strength of CTB specimens with SAPs was higher than regular CTB specimens.28d compressive strength of CTB specimens with SAPs made by Static pressure method was 5.87 MPa,which is 27%higher than that of regular CTB specimens.Drying shrinkage of CTB specimens with SAPs was decreased by 52.5%comparing with regular CTB specimens.Through the microstructure analysis it was found that CTB specimens with SAPs could produce more hydration products,which is also the reason for the strength improvement.