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Soilcrete properties modified with two types of polymer up to 0.20 % (% wt. dry weight of cement) were tested and quantified. The stress–strain curve of modified soilcrete with polymers was examined for curing periods up to 28 days and modeled using two different mathematical models. The flowability of the soilcerte was maintained within the range of 105 to 110% as recommended by ASTM standard. Polymers decreased the water/cement ratio ( w / c ) by 14.5 to 25.5%, based on the type and amount of polymers. The compressive strength and modulus of elasticity of soilcrete increased by 72% to 153% and by 55% to 195%, respectively, when the soilcrete was modified with 0.20% of polymers. The nonlinear Vipulanandan p-q equation was employed to predict the stress–strain behavior of the modified soilcrete with polymers and was compared with the β model prediction. Based on the statistical evaluation tools, the Vipulanandan p-q model predicted the stress–strain relationships better than β model. Linear (LM) and nonlinear relationships (NLM) were also used to predict the compressive strength, modulus of elasticity, and toughness of the soilcrete as a function of w/c, curing time, and polymer contents.

We have developed cross-linked polyrotaxane (cPR) that is composed of moveable cross-links and slide-ring components, in its backbone. The cPR is blended with oil well cement to improve elastic properties, and it has demonstrated improvement in elastic modulus with minimum effect on compressive strength. The optimization of curing time, fluid flow behavior, and dynamic strength development in the presence of cPR in cement are also evaluated. The Young’s modulus and compressive strength are measured at 20 MPa and 150°C to simulate downhole conditions. Remarkably, cement—cPR has, revealed a 33% increase in strain compared to neat cement.

Concrete structural properties are compromised largely due to corrosion susceptibility of steel reinforcements. This results in weakening and eventual failure of structures. Several strategies have been employed in past to control corrosion and increase mechanical strength of concretes, in particular for structural applications. In this study, fly ash and polypropylene fibers were utilized as the admixtures for preparation of concrete blocks with variable water-cement (w/c) ratios i.e. 0.45, 0.5 and 0.65. Three different grades of cements were selected in this study namely OPC 43, OPC 53 and sulfate resistant one. Also, two different steel alloys were used i.e. ASTM-615 and ASTM-706, since both of them are very common reinforcement materials (rebars). The curing time of 56 consecutive days was employed before testing and characterization. The results suggest remarkable improvement in the mechanical properties of blocks upon the incorporation of admixtures. However, rebars exhibited highest corrosion rate in the presence of OPC 43 cement at w/c ratio of 0.65.

This research mainly focused on the properties of decorative white cement tiles which made from waste glass and white cement. The ratio of waste glass powder and white cement were studied at 10 : 90, 15 : 85, 20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 by using water content at 30 %wt. All components were mixed and cast into the mould. Decorative white cement tiles were curing at 14, 21 and 28 days. In order to characterize physical and mechanical properties, all tiles were measured density, water absorption and compressive strength. According to the results, it can be obviously seen that density increased and water absorption decreased with increasing waste glass powder content. The highest compressive strength of around 36.5 MPa was found at 20 %wt of waste glass powder. However, compressive strength decreased with increasing waste glass powder over 20 %wt (waste glass powder 20: white cement 80). It was found that the lowest compressive strength of around 30.58 MPa was found at 70 %wt of waste glass powder. Curing time also affected properties as it was found that increasing curing time to 28 days resulted in increasing of density and compressive strength. In order to study how long does essential oil last on decorative white cement tiles, the orange essential oil at 1, 5 and 10 %wt were added into the white cement paste by using waste glass powder : white cement at 20 : 80 with 30 %wt of water. Decorative white cement tiles were smelled by 30 people every morning for 30 days and it can be found that 10 %wt of orange essential oil last longest on the decorative white cement tiles with 22 days.

In an attempt to reduce environmental impact, paper sludge ash (PS ash) has recently been studied for its complementary reuse with cement for soil stabilization. In order to establish the optimal mixture design for combining PS ash and cement in soils, a detailed investigation into the stabilizing mechanism is required. To assess the combined effects of PS ash and cement on the strength development of stabilized clay soil, referred to as PS ash–cement-treated clay, a new critical parameter, the unabsorbed and unretained clay-water/cement ratio W*/C, was proposed. To determine W*/C, a new testing method for evaluating the water absorption and retention performance of PS ash was developed. It was revealed that the water absorption and retention rate Wab of PS ash increased with curing time. Unconfined compression tests conducted on the PS ash–cement-treated clay with various water-cement–PS ash mixture proportions and different curing times affirmed that the strength development was fundamentally governed by the parameter W*/C. This suggests that the water absorption and retention rate Wab obtained by the developed method is an essential material parameter in the mixture design for the PS ash–cement-treated clay. It was also found that the effect of the hybrid treatment method, which uses both cement and PS ash, was better than that of the method which uses cement alone, particularly under high W*/C conditions. This indicates that the water absorption and retention performance of PS ash can be fully utilized when the mixture has sufficient unabsorbed and unretained water for cement hydration.

This paper presents an extensive array of laboratory investigation on collapse behavior and shear strength characteristics of collapsible soils at different initial structures. This study also clarifies the crucial role of chemical stabilization on the mechanical behavior and the workability of the collapsible soils using different percentages of various stabilizer agents. The effect of the curing time and the amount of the agents on the collapsibility, the unconfined compressive strength, the undrained shear strength, and the consistency of the treated collapsible soils were studied. The findings demonstrated that cement outperformed lime and natural pozzolan in improving the strength and engineering properties of these collapsible clays. The results indicated that adding cement to soil minimized the degree of collapsibility significantly and increased the undrained shear strength of soil up to 5 times.

The decarbonization of concrete production requires a multi-pronged approach including the abatement of CO2 emissions from cement production as well as storage of CO2 within concrete itself. This study explores the decarbonization potential of combining bioenergy and carbon capture and storage (CCS) during cement production with the accelerated carbonation of fresh concrete and the natural carbonation of demolished concrete for the life cycle net CO2 of 30 MPa ordinary Portland concrete. As both biomass and concrete reuptake CO2 over time, the timing of CO2 emissions and removals is explicitly accounted for. At current technology levels, the combination of bioenergy and CCS in cement production combined with the carbonation of demolished concrete was seen in our model to allow for net CO2-negative concrete. However, the concrete is CO2-positive until the CO2 of production is reabsorbed by biomass regrowth and the carbonation of demolished concrete at end-of-life. In our model, accelerated carbonation was, by itself, an inefficient CO2 storage mechanism, due to the penalty of energy use and injection losses. However, if it led to a gain in concrete strength, accelerated carbonation could result in lower CO2 via reduced resource demand and cement production.

Este artículo presenta las curvas de desarrollo de resistencia a la compresión a través del tiempo de curado para mezclas de concreto elaboradas con tres tipos de cementos modificados comercializados en Costa Rica, y su combinación con agregado nacional proveniente de fuentes de tajo y río. Se utilizaron los cementos MM/A (E- C) – 28, MM/B (P-C) – 28 y MP A – AR, definidos según el reglamento RTCR 479:2015 Materiales de Construcción. Cementos Hidráulicos. Especificaciones. Debido a la carencia de curvas de desarrollo de resistencia para concretos elaborados con distintos tipos de cementos modificados y agregados comercializados en el país, el objetivo de este trabajo se focalizó en obtener tales curvas y el desarrollo porcentual de resistencia. Se caracterizó todo el material utilizado las respectivas normas ASTM o INTECO; asimismo se comprobó que el agregado y los cementos a utilizarse fuesen adecuados a partir de los parámetros establecidos en la ASTM C33/C33M-18 y la INTE C147:2018, respectivamente. La determinación de la resistencia a la compresión se efectuó por medio de especímenes cilíndricos de 150 mm x 300 mm, con edades de falla de 3, 7, 28 y 56 días; siguiendo un diseño de mezcla determinado a partir del ACI 211-91. A los datos generados se le realizó un análisis estadístico para establecer relaciones y respaldar los resultados obtenidos. Con este trabajo se logró demostrar que los cementos comercializados en Costa Rica con un grado de adición de escoria de alto horno son capaces de presentar una ganancia de resistencia significativa en el concreto después de los 28 días de curado, las mayores resistencias a la compresión en el concreto se generan al utilizar agregado de río, y generalmente la resistencia del concreto no varía significativamente al emplearse el mismo tipo de cemento para distintos tipos de agregados.

Expansive soil is considered to be an unfavorable soil due to its swelling-shrinking behavior. In order to improve the properties of expansive soil, the addition of steel slag powder (SSP) has been used to improve expansive soil that has been mixed with the cement. In this study, a series of cylindrical improved expansive soil specimens were prepared, which were improved either by the addition of cement, cement SSP, or cement SSP sodium hydroxide (NaOH). All of the specimens were prepared with an optimum water content and then subjected to a maximum of 12 closed-system freeze-thaw (F–T) cycles. The specimens were subjected to different curing times and temperatures (−5°C,−10°C and −15°C) during the tests. After each freeze-thaw (F–T) cycle, the volume of each specimen was measured and an unconfined compression strength (UCS) test was performed. The results have shown that as the temperature of the F–T cycle decreased, the volume expansion rate increased with the increase of the length of the F–T cycle. As the curing time increased, the effect of the F–T cycles on the volume change rate of the specimens reduced and the UCS increased. The first F–T cycle had the greatest influence on the volume of the specimen as well as the UCS of the improved expansive soil. After the improved expansive soils had undergone more than eight F–T cycles, the volume change rate of the specimen tended to stabilize. The maximum F–T volume change rate of the improved soil was 1.93%. When the curing age was 60d and 90d, the strength of the specimen with cement SSP sodium hydroxide was 377.3 kPa and 294.7 kPa higher than the specimen with cement only (ES specimen), and its strength degradation rate was 18.737% and 9.97% lower than the ES specimen. The results have shown that the addition of SSP and cement improved the expansive soil; moreover, NaOH inhibited the degradation of the soil during an F–T cycle.

This study investigated the effects of relative humidity ( $$R_{h}$$ ) or total suction condition during curing on small-strain shear modulus (G0) of a cement-treated silty sand using free-free resonant frequency tests (FFR). The moduli were determined on samples cured at different suctions corresponding to three $$R_{h}$$ values of 7%, 75%, and 100%, in both unsoaked and soaked conditions. Soil–water retention curves (SWRCs), and unconfined compression strength (UCS) were also determined along with x-ray diffraction (XRD) analysis. The cement-treated SWRCs showed a much flatter slope than the non-treated ones, and the air-entry suction increased with cement content. The values of G0 increased with cement content and curing time. The highest modulus was achieved in 75% $$R_{h}$$ curing condition. The 7% $$R_{h} $$ condition resulted in a significant drop in modulus, even close to the non-treated G0 for the 2% cement case. At the same UCS value, the soaked cement-treated samples had higher modulus than the non-treated ones in the unsoaked condition, indicating that the effect of suction on modulus was smaller than the effect of cementation. XRD analysis revealed a greater availability of C3S in 7% $$R_{h}$$ curing condition at 7-day curing period suggesting that the hydration process was still not complete, which explained the decrease in G0 in this curing condition.

Mechanical properties are important indexes to evaluate the improvement effect and engineering performance of cement-stabilized loess (CSL). This paper presents a comparison of the mechanical properties of CSL compacted using hammer quasi-static compaction method (QSCM) and vertical vibration compaction method (VVCM). The compaction properties, unconfined compressive strength (UCS), splitting strength (SPS), and resilient modulus (RM) of the laboratory-compacted CSL using VVCM and QSCM are tested and compared. Furthermore, the effects of compaction method, cement content, compaction coefficient, and curing time of the CSL specimens are investigated. In addition, field measurements are carried out to validate the laboratory investigations. The results show that the laboratory-compacted CSL using VVCM has a larger dry density and smaller optimum water content than that using QSCM. And the compaction method has a great influence on the mechanical strength of CSL. The UCS, SPS, and RM of the specimen produced using VVCM are averagely 1.17 times, 1.49 times, and 1.17 times that of CSL produced using QSCM, respectively, and the UCS, SPS, and RM of the specimens produced using these two methods increase linearly as the cement content and compaction coefficient increase, while the mechanical strength growth curve experiences three periods of increasing sharply, increasing slowly, and stabilizing with the curing time increased. Moreover, the results also show that the mechanical properties of laboratory-compacted CSL using VVCM have a better correlation of 83.8% with the field core samples.

Expansive soil, as an unsaturated cohesive soil, is considered a harmful geological soil due to its tendency to expand with water and shrink with loss of water. Especially in the alternating environment between dry and wet (D–W) cycles, it can cause engineering accidents because of its deformation. Steel slag powder (SSP) was used as a new curing agent to improve the expansive soil by combining cement. The variation rules of strength characteristics of improved expansive soil were studied under the condition of the D–W cycles. Through the laboratory test, the unconfined compressive strength (UCS) characteristics of the expansive soil (ES) and improved expansive soil (improved by cement (Es-C) and by steel slag powder and cement (Es-SSP-C) and by steel slag powder and cement and NaOH (Es-SSP-C-N)) were studied under different curing age and different D–W cycles. The testing results show that the strength of improved expansive soils increases with the curing time. The strength degradation of Es-SSP-C-N samples was the least when they have performed the D–W cycles, which indicates that Es-SSP-C-N is a good method to improve expansive soil in the D–W circulation environment.

The formation of CA2 and CA6 in calcium aluminate cement bonded castables lead to a large volume expansion, which probably results in the generation of cracks, thereby increasing slag penetration and decreasing mechanical strength. In this study, the influence of curing time on the dimensional stability of calcium aluminate cement bonded castables is considered to improve the volumetric stability. Phase compositions and morphologies evolution of matrix samples and castables are characterized by XRD and SEM, respectively. The results indicate that the volume stability of castables is greatly improved by increasing curing time from 0.5 days to 6 days after firing at 1600 °C. This can be attributed to two main reasons. First, the improvement in migration of CaO through extending curing time favors more uniform distribution of in situ CA6. Second, more hydrates after dehydration creates more micro-pores, thereby providing space for the generation of in situ CA6.

The treatment of contaminated soil is a crucial issue in geotechnical and environmental engineering. This study proposes to incorporate appropriate polypropylene fibers and cements as an effective method to treat heavy metal contaminated soil (HMCS). The objective of this paper is to investigate the effects of fiber content, fiber length, cement content, curing time, heavy metal types and concentration on the mechanical properties of soils. To this end, a series of direct shear test, unconfined compression strength (UCS) test, dry-wet cycle and freeze-thaw cycle test are performed. The results confirm that the appropriate reinforcement of polypropylene fibers and cement is an effective way to recycle HMCS as substitutable fillers in roadbed, which exhibits benefits in environment and economy development.

Fractures in the craniofacial region are a serious problem in terms of treatment. The most reasonable solution is the use of individual implants dedicated to a specific patient. The aim of this study was to develop the implant system specifically for treatment of the orbital floor defects of blowout fractures of maxillofacial region, using polypropylene yarn and bone cement. Three types of bone cement were used to fix the polypropylene yarn: unmodified, antibiotic-loaded, and modified with nanometals. The following research was carried out: selection of cement production parameters, assessment of the curing time, measurement of polymerization temperature, an analysis of microstructure and surface topography, evaluation of wettability, measurement of microhardness, and studies of bactericidal effectiveness. The research confirms the possibility of using bone cement and polypropylene yarn for an individual implant, dedicated to the fractures treatment in the maxillofacial region. Moreover, the bactericidal properties of the proposed modifications for bone cement have been verified; hence, bioactive cements are recommended for use in the case of infectious complications.

Foam-cemented paste backfill (FCPB) has become a trend to solve the problem of roof-contacted filling. In order to solve the time-consuming and labor-intensive disadvantages of laboratory uniaxial compressive strength (UCS) tests, a hybrid artificial intelligence model which combines random forest (RF) algorithm and grid search optimizer (GSO) was proposed for FCPB strength prediction. Moreover, the effects of foaming agent on cement hydration and pore structure characteristics were studied. The results showed that GSO can effectively tune the hyper-parameters of the proposed GSO-RF model and the developed model is an efficient and accurate tool to predict the UCS for FCPB. Though the foaming agent will not change the influence trend of cement-tailings ratio, solid content and curing time, the influence degree will be weakened by the foaming agent. The ranking of the relative importance of influencing variables is: cement-tailings ratio > curing time > foaming agent dosage > solid content. In addition, the foaming agent has no significant effect on the hydration of cement. The foaming agent mainly changes the strength by changing the pore structure characteristics (especially the large pore volume). This research can provided some guidance for developing UCS prediction model for FCPB.

The catastrophic events faced by the Oil and Gas industry in the past depict the importance of maintaining the integrity of the well. The cement acts as a crucial barrier throughout the life cycle of the well. The contamination of the cement occurs due to inefficiency in cementing practices and operations. Experimental investigations have been done on the reduction in mechanical properties of different API class cement considering contamination with water-based mud and oil-based mud. This study focuses on analyzing the changes in mechanical properties of API Class C cement on varying the following parameters: OBM contamination (0%, 0.6%, 1.1%, 2.2%, 4.3%) Curing time (4 hrs, 6 hrs, 8 hrs, 1 day, 3 days, 7 days) Temperature (25˚C, 75 ˚C) API recommendations were followed for preparing the cement slurries. The destructive, as well as non-destructive tests were carried out on the cement samples at ambient room temperature to measure the uniaxial compressive strength (UCS) for OBM contaminated class C cement slurries. The general trend observed is that the UCS increases with an increase in curing time and temperature. UCS decreases with an increase in OBM contamination. Logarithmic trends were obtained for UCS vs curing time for different contaminations at a given temperature. Exceptions were observed at lower curing times where contaminated samples showed better results than the neat cement slurries. These observations play a critical role in understanding contaminated cement behavior. This widespread work was carried out only on API Class C cement to provide reliable data for future references. The correlations presented in this paper will help operators estimate the deterioration in mechanical properties of Class C cement in the presence of low OBM contamination. Email: nachiket.arbad@ou.edu & cteodoriu@ou.edu

In this study, the effect of volcanic tuff mineral additive in concrete manufacture on the compressive strength of concrete was investigated using the artificial neural network (ANN). Cement mixtures were produced by adding volcanic tuff (VT) in the ratio of 0% (control), 10%, 15%, and 20%. The effect of curing time was investigated by applying 28- and 90-day periods. The main inputs for the ANN model were cement, VT, super-plasticizer (SP), and aggregates with 4 different mesh sizes and outputs were 28- and 90-day compressive strengths. In the comparison of obtained results by artificial neural networks with the experimental data, good agreements have been seen. It was also seen that the optimum volcanic tuff rate was 20% in concrete in terms of compressive strengths.

Magnesium phosphate cement (MPC), a new type of inorganic cementitious material, is favored in engineering and construction because of its fast setting speed and high bonding strength, but is limited in practical application due to its high production cost and excessive release of hydration heat. Relevant research has investigated the application of discarded oyster shell powder (OSP) replacing cement mortar and has reported certain improvements to its performance. Consequently, focusing on discovering more effects of OSP on MPC performance, this study, by using a typical three-point bending test, used 45 cuboid specimens to investigate the influences of OSP mass content on flexural properties of MPC at different curing times. Results illustrated that MPC flexural strength was first increased and then decreased, and 3% is the critical value for OSP mass content. Similarly, the stiffness of all specimens presented a tendency to increase first and then decrease, with a maximum value of 36.18 kN/mm appearing at 3%, i.e., the critical OSP mass content. Finally, scanning electron microscope (SEM) and X-ray diffraction (XRD) were employed to analyze the microstructure and composition of specimens, confirming that the specimens generated not only the hydration product potassium phosphate magnesium (MgKPO4·6H2O, MKP), but also another new reactant (CaHPO4·2H2O).

As a kind of porous material, the pore characteristics of cemented paste backfill (CPB) is strongly correlated to its mechanical properties. In this study, CPB specimens were prepared with tailings/cement ratio (T/C ratio) of 4, 6, and 10, and cured for 3, 7, 14, 28 days. Pore structures characteristics of CPB specimens were analysed using nuclear magnetic resonance (NMR) and scanning electronic microscopy (SEM). The uniaxial compressive strength (UCS) was used to describe the mechanical property of CPB specimens. The effect of T/C ratio and curing time on the pore characteristics of CPB specimens and the effect of pore structure changes on the UCS was investigated. The results indicated that: (i) the integrity of CPB microstructure was closely related to the development status of the pore structure, which can be represented by micro-parameters like porosity, average pore area, et al. The more integrate CPB microstructure was, the higher the UCS was; (ii) with the same curing time and different T/C ratio, the pore size was mainly between 10 and 100 nm, and a “λ” shape distribution was observed. As the curing time increased, the maximum of the “λ” distribution shifted left, meaning that the size of pores in CPB decreased; (iii) At the same curing time, the pores size of less than 10 nm gradually decreased with a higher T/C ratio while those with size of 10-100 nm and ＞1000nm gradually increased. and (iv) the extension of small pores lead to the cross-connection of pores and resulted in the fracture of CPB, which was shown as a crack on the main section. This work analysed the heterogeneity of CPB in detail, and can provide a basis for studying the constitutive relations of CPB.

Recycled construction and demolition (C&amp, D) waste can reduce the rebuild cost, and is environmentally friendly when recycled asphalt pavement (RAP) aggregate constitutes the main part. This paper investigated the mechanical performance of RAP concrete, and the applicability of RAP in road base layers also was discussed. Several mechanical laboratory tests were selected, including the unconfined compressive-strength, splitting-strength, and compressive-resilience modulus tests. The RAP concrete had a good road performance in a cold region, which was proved by the temperature-shrinkage test, dry-shrinkage test, freeze–thaw-cycle test, and water-stability test. Based on various cement dosages from 3.5% to 5.5% in RAP concrete mix design, three RAP aggregate replacement ratios (30%, 40%, and 50%) were selected to study the variation of mechanical properties with increasing curing time, and the optimal aggregate substitute ratio was determined. A scanning electron microscope (SEM) was used to observe the inner-structure interface between the asphalt binder and cement stone. A numerical model is presented to simulate the RAP compressive strength with respect to the effect of multiple parameters. The research results can provide a technical reference for RAP use in the reconstruction and expansion of low-grade highway projects.

This paper describes the effect of stabilizer content, curing time and moisture content on the UCS based upon 150 samples of stabilized soil. The results indicate an optimum value of lime or cement...

Sands reinforced by hydraulic binders (cement) have constituted in recent decades a major asset for the expansion of several areas of engineering. The mechanical behavior of sand-cement mixtures has undergone some controversies studied on the Chlef sand. In this paper, we present an experimental study to investigate the mechanical behavior of a sandy soil reinforced by a hydraulic binder (cement), using the direct shear apparatus emphasizing on the shear strength characteristics and the vertical deformation variation of cemented reinforced sand. The parameters used in this study are mainly: relative density (Dr = 80%), normal stress (σn = 100, 200, 400 kPa), water content (3, 7 and 10%), cement content (2.5, 5, 7.5 and 10 %) and cure time (7, 14 and 28 days). The experimental results show that the mechanical characteristics in terms of internal cohesion (C) and internal frication angle (φ) give a better mechanical performance with the binder inclusion, and the cure conditions play an effective role on the improvement of the shear strength. This result also showed that 10% of the cement content gave us a maximum value of shear strength and an optimal influence on the mechanical characteristics. The addition of cement not only improves the shear strength of soil, but also provides diversity in the resistance against the deformations imposed load, which can be established by a dilatant character.

For economical and ecological reasons, supplementary cementitious materials (SCM) are increasingly used in concrete. Although having a lot of advantages, concretes with SCM have different cement matrices and do not have the same evolution as a function of time as CEM I concretes. In this paper, the microstructure of various cement pastes with/without SCM (slag GGBS, fly ash FA and metakaolin MK), has been investigated as a function of the curing time. The microstructure was characterized not only by usual techniques such as XRD and TGA-DTA, but also by 29Si and 27Al NMR spectroscopy. The use of a combination of techniques for microstructural characterization allowed to quantify the proportion of each cementitious phase. This quantification showed the evolution of the cementitious matrices as a function of the binder content and of the curing time. For example, the alumina content in the C-S-H and the average length of C-S-H chains are higher for cement pastes with SCM than for OPC ones. Hydrated alumina phases proportions (AFt, AFm and TAH) are also higher in SCM cement paste. For MK and FA cement pastes, in addition to pozzolanic reactions, it seems that a small part of calcium from clinker hydration is used to form these aluminate phases.

Raveling, as one of the key distresses of the chip seal, affects the performance of the chip seal. A new cold-mixed ultra-thin (CMUT) chip seal consisting of modified emulsion, single particle size aggregate, and cement was designed. The wet track abrasion test (WTAT) was used to study the effects of curing conditions, submersion durations, amounts of aggregate, emulsion, and cement on both the early raveling and wet raveling resistance of the CMUT chip seal. In addition, the binder bond strength (BBS) test was also used to evaluate the moisture-induced damage with the prolonging of submersion durations. Additionally, the one-way analysis of variance was used to analyze the sensitivity of different factors. The results indicate that both temperature and curing time could significantly affect the raveling resistance of the CMUT chip seal. It is confirmed that submersion duration has significant influences on aggregate losses and pull-off strengths. With the prolonging of submersion duration, the moisture damage was severe but tending stable. Therefore, the raveling potential of specimens after being submerged for 6d was used to evaluate the wet raveling potential. According to the sensitivity analysis, it is confirmed that the emulsion dosage is the most significant factor affecting both the early and wet raveling resistance. Cement dosage is recognized to have dramatic effects on wet raveling resistance, while the effects are negligible when it comes to early raveling resistance. Furthermore, the amount of aggregate can hardly influence the raveling resistance of the CMUT chip seal.

A simple formula with no fitting parameters is proposed, with which the strength of cement-treated soil can be calculated at any curing time with the known cement-water ratio (the ratio of the cement mass to the mass sum of the water in the soil and the water in the cement paste) of the cement-treated soil and the corresponding strength at a certain short curing time. The results obtained with this formula basically reflect the law whereby the strength of cement-treated soil increases with the curing time. To further facilitate the use of this formula, the conversion relation of the cement-water ratio to the cement-mixed ratio and the water-cement ratio of the cement paste were presented. In such a way, the strength of cement-treated soil can be predicted directly using the common proportioning parameter of the cement-treated soil. In addition, with the known long-term (within 180 d) target strength of the cement-treated soil, its short-term strength can also be speculated through this formula, on whose basis a formulation design for cement-treated soil may be conducted as well.

To characterize the mechanical-strength growth of cement-stabilized macadam (CSM), the effects of different cement dosages, aggregate types, aggregate gradations, and curing times on the mechanical strength of CSM produced using the vertical-vibration-compaction method (VVCM) are studied. Then, a mechanical-strength-prediction equation and model for VVCM-compacted CSMs are proposed. The mechanical-strength ratio between the VVCM-compacted CSM laboratory specimens and the field cores exceeds 92%. The strength-growth rate of the VVCM-compacted CSM is very high at a curing time within 14 days and tends to be gentle after 28 days, settling eventually after 90 days. The correlation coefficient R2 of the proposed mechanical-strength-growth equation exceeds 0.98; the mechanical strength can be predicted when the cement dosage, aggregate type, and aggregate gradation are known. R2 of the established mechanical-strength-prediction model of CSM is as high as 0.97; thus, when the aggregate types and the mechanical strength at the curing time of 3 days are known, this prediction model can effectively predict the mechanical strength of the CSM with any curing time (T ≥ 3). Empirical on-field data, in comparison with proposed growth equation and prediction model, deviates only slightly, which can facilitate the design and construction of unique CSM bases.

This paper proposed a novel and efficient fluid for use in oil and gas well of deep-water weakly consolidated formation to prevent the oil and gas leak from the wellbore. The proper placement techniques are suggested to make the annulus and formation consolidated at the same time. The evaluation of compressive strength and thickening time of cementing fluid illustrated that the cementing fluid is suitable to use as oil well cement and formation curing agent. The optimal parameter of grouting pressure, grouting time, curing time, water/solid ratio and undrained shear strength of formation are proposed by depth of penetration, compressive strength and shear bonding strength tests. The reaction mechanism and solidification pattern of cementing fluid are revealed. After the operation of cementing fluid, the strength transition zone formed in the adjacent area of wellbore. Thus, the bonding strength of cement-formation interface was enhanced, and the leakage of oil and gas can be prevented.

The recycled layer in full-depth reclamation (FDR) method is a mixture of coarse aggregates and reclaimed asphalt pavement (RAP) which is stabilized by a stabilizer agent. For design and quality control of the final product in FDR method, the unconfined compressive strength of stabilized material should be known. This paper aims to develop a mathematical model for predicting the unconfined compressive strength (UCS) of soil-RAP blend stabilized with Portland cement based on multivariate adaptive regression spline (MARS). To this end, two different aggregate materials were mixed with different percentages of RAP and then stabilized by different percentages of Portland cement. For training and testing of MARS model, total of 64 experimental UCS data were employed. Predictors or independent variables in the developed model are percentage of RAP, percentage of cement, optimum moisture content, percent passing of #200 sieve, and curing time. The results demonstrate that MARS has a great ability for prediction of the UCS in case of soil-RAP blend stabilized with Portland cement (R2 is more than 0.97). Sensitivity analysis of the proposed model showed that the cement, optimum moisture content, and percent passing of #200 sieve are the most influential parameters on the UCS of FDR layer.

Silt has a poor geotechnical performance. In this study, an investigation on silt solidification was performed by incorporating lime, mixture of lime and cement (LC), and a self-developed lab-made binder (named SEU-2 binder). The properties of solidified silt cured in standard curing and immersion curing for 7, 28 and 90 days, respectively, were determined in relation to unconfined compressive strength (UCS) and water stability. The solidification mechanism was further analyzed by the technologies of scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. Results revealed that the UCS of lime solidified silt had an optimum value when the dosage of lime was 8%, while the UCS of LC and SEU-2 binder solidified silt increased with an increase of LC and SEU-2 binder content. The water stability coefficient (WSC) of lime solidified silt increased first and then stabilized, whereas the WSC of LC solidified silt hardly changed with water curing time. However, WSC of SEU-2 binder solidified silt has insignificant change with SEU-2 binder content. With the increase of binder content, the WSC of lime solidified silt increased first and then decreased, and the WSC of LC solidified silt hardly changed. However, for SEU-2 binder solidified silt, WSC showed no obvious correlation with SEU-2 binder content. Generally, SEU-2 binder solidified silt had superior mechanical properties relative to that solidified by lime or LC, which can be further explained by SEM and XRD analyses.

In order to guarantee the safety of oil and gas exploration and development and ocean environment, the influence of components properties comprised of casing size, cement strength and formation strength on sealing ability of cementing isolation system in deep-water shallow formation was investigated by using the simulated cementing isolation system device in this paper. Results show that casing size has little effect on the sealing ability of cementing isolation system, and the sealing ability is not related to the casing size. When the cement strength is lower than formation, the cement strength decides the sealing ability, and the maximum sealing pressure of highest strength cement (2.15 MPa) is about 2 MPa. When the cement strength is higher than formation, the unconsolidated formation is the weakness and sealing failure area, and the maximum sealing pressure of highest strength formation (2.46 MPa) is about 3 MPa. Increasing the cement strength grade and extending the curing time can improve the sealing ability of cementing isolation system to a certain extent, however, solidifying and enhancing the loose formation is the most effective method to improve the sealing ability of cementing isolation system in deep-water shallow formation.

This paper presents the development of the unconfined compressive (qu) and the splitting tensile strength (qt) of a chemically stabilized silt soil. For this, specimens with a volume of 196,35 cm3 were prepared using cement contents of 3%, 5%, 7% and 9% and then tested after 7 days of cure. The porosity/volumetric cement content (η/Civ) was used as the main parameter of the results analysis. The results show that with the decrease in the ratio η/Civ the values of qu and qt increase. Thus, the decrease in porosity meant an increase in qu and qt. A general estimation equation for qu and qt was developed to estimate the resistance of the mixtures with the use of η/Civ adjusted to a scalar equal to 0,45. The equations showed that it is possible to estimate the value of qu and qt of treated soil among the amounts of cement, η/Civ ratio and curing time employed in the present work. Finally, a constant ratio of qt/qu=0,15, which is independent of the voids and the volumetric content of cement, was calculated.

This paper has been prepared in the frame of a research focused on the development of Cold Mix pavement materials made with calcium-alginate Capsules (CMC) instead of with just bitumen emulsion, as it is normally made. The initial objective was to remove most of the water in cold mix asphalt by encapsulating bitumen droplets. The encapsulation method allowed the preparation of polynuclear capsules with bitumen emulsion encapsulated, which membrane was made of calcium-alginate. Capsules were mixed with aggregates at the ambient temperature. During mixing, the capsules containing bitumen emulsion would break, release their content and coat the aggregates. To study CMC, an extensive experimental programme has been carried out to evaluate the effect of compaction energy, cement content, curing time and binder type on the mechanical properties of CMC. It was found that CMC test samples increased their Marshall stability linearly with the increase of the compaction energy. Test samples could be demoulded immediately after compaction. Furthermore, the Marshall stability of CMC increased with the curing time, and the general strength improved with the increasing amount of capsules in the mixture. It was found that the bitumen in CMC did not have an important role on the strength of the pavement material, which came mainly from the alginate in the capsules. In short, cold mix pavement materials made with calcium-alginate (Ca-alginate) capsules is a novel material for pavements that has shown potential to be an alternative for conventional cold mix asphalt made with bitumen emulsion.

This research work examines the utilization of cement in order to improve low plasticity clay soil. The soil samples treated with 2, 4 and 6% cement percents and cured for different curing times extended to 90 days. Laboratory investigations include unconfined compression, indirect tensile, gas permeability and microstructural tests, which were conducted on the tested samples. The soil-water retention behavior has been also investigated. The test results showed that the cement addition improved both the compressive and tensile strength properties of soil specimens. These strength properties were also increased with curing times. pH and electrical conductivity values were good indicators for the enhancement in the strengths properties. The results of micro structural tests illustrated that the natural soil specimens contain voids and the open structure. Further, these tests showed the cementation of soil grains and filling the voids among soil grains with cementing compounds. Gas permeability and soil-water retention behavior of soil specimens are strongly related to the variations in the soil structures. Further examination illustrated that in the case of low cement content, the pore size distribution (PSD) and the efficiency of gas permeability are more sensitive to curing times.

In this paper, a series of unconfined compressive strength (UCS) tests were performed to study the effect of cement content, zeolite content, initial moisture content, number of freeze–thaw cycles, and curing time on the UCS of low-plasticity silty sand–clayey sand. The results indicate that zeolite can be used along with cement as a stabilizer to enhance mechanical behavior of the soils. The specimens containing cement and zeolite show better response with a higher UCS than the stabilized samples with cement or zeolite alone. The addition of zeolite has an important effect on the increase in both UCS value and failure strain of cement-stabilized specimen. However, the stress–strain curve of stabilized specimens is not influenced significantly by the increase of zeolite content from 3 to 9%. The UCS values of the stabilized specimens decreased as the number of freeze–thaw cycles increased. The cement-stabilized samples have freeze–thaw durability when zeolite content increases from 3 to 9%. The stabilized specimens with 6% cement and 9% zeolite have slightly higher freeze–thaw durability than other specimens. The UCS of the specimens compacted on the dry side is more than that of the compacted sample on the OMC or wet side of optimum for given additives contents. The specimens compacted on the dry side of optimum exhibited a lower failure strain. The implication of this work is significant in geotechnical practice; it provides a general knowledge of stabilization of soils using cement and zeolite and the quantities to use to achieve the desired geotechnical properties.

This paper presents the results of the fracture toughness of concretes containing two mineral additives. During the tests, the method of loading the specimens according to Mode I fracture was used. The research included an evaluation of mechanical parameters of concrete containing noncondensed silica fume (SF) in an amount of 10% and siliceous fly ash (FA) in the following amounts: 0%, 10% and 20%. The experiments were carried out on mature specimens, i.e., after 28 days of curing and specimens at an early age, i.e., after 3 and 7 days of curing. In the course of experiments, the effect of adding SF to the value of the critical stress intensity factor&mdash, KIcS in FA concretes in different periods of curing were evaluated. In addition, the basic strength parameters of concrete composites, i.e., compressive strength&mdash, fcm and splitting tensile strength&mdash, fctm, were measured. A novelty in the presented research is the evaluation of the fracture toughness of concretes with two mineral additives, assessed at an early age. During the tests, the structures of all composites and the nature of macroscopic crack propagation were also assessed. A modern and useful digital image correlation (DIC) technique was used to assess macroscopic cracks. Based on the conducted research, it was found the application of SF to FA concretes contributes to a significant increase in the fracture toughness of these materials at an early age. Moreover, on the basis of the obtained test results, it was found that the values of the critical stress intensity factor of analyzed concretes were convergent qualitatively with their strength parameters. It also has been demonstrated that in the first 28 days of concrete curing, the preferred solution is to replace cement with SF in the amount of 10% or to use a cement binder substitution with a combination of additives in proportions 10% SF + 10% FA. On the other hand, the composition of mineral additives in proportions 10% SF + 20% FA has a negative effect on the fracture mechanics parameters of concretes at an early age. Based on the analysis of the results of microstructural tests and the evaluation of the propagation of macroscopic cracks, it was established that along with the substitution of the cement binder with the combination of mineral additives, the composition of the cement matrix in these composites changes, which implies a different, i.e., quasi-plastic, behavior in the process of damage and destruction of the material.