Rapid Hardening Cement Research Articles

Mechanical properties, durability and self-healing performance of mortar containing double-layers capsules

To improve the self-healing performance of cementitious materials and minimize the negative impact of self-healing materials on mortar, a novel type of double-layer capsules is developed in this study. The developed double-layer capsule includes the rapid hardening cement as the internal wall and polyvinyl alcohol (PVA) as the external wall. To evaluate its impact on mortar, two factors (i.e., capsule size and dosage) are considered and the correspondent experiments of investigating mechanical properties, durability, and self-healing performance are conducted. Experimental results present that the double-layer capsules reduce the flexural and compressive strength of mortar. With a reduced capsule size and a small ratio of the dosage, the negative impact the capsule gradually weakens. Moreover, the mixing of capsules slightly decreases the chloride penetration resistance and carbonation resistance of mortar specimens, while improves the frost resistance and impermeability greatly when the dosage is within 10%. Furthermore, the capsules can significantly improve the self-healing capacity of mortar. Especially when the capsule size is 2.36–3.2 mm and the dosage is 10%, the healing effect on matrix is highest. In addition, the XRD\\SEM\\XCT results indicated that the healing products mainly include C-S-H gel, CaCO3, Aft and Mg-containing compounds, the filling and bonding effects of which realize the automatic and effective recovery of matrix properties.

Effects of early vibration and resistant strategies on bond performances between high-strength concrete and rebar

The local bond performances between rebar and high-strength concrete (HSC) exposed to early vibration were experimentally investigated in this study. In addition, three vibration-resistant strategies, including additions of special rapid-hardening cement(calcium sulphoaluminate cement, CSA), shrinkage compensation admixture (expansion agent, EA), and toughening metallic fibers (steel fiber), were verified through penetration resistance, compressive, and central pull-out tests, respectively. Finally, two-way ANOVA tests were conducted to understand the significance of each strategy from a statistical perspective. The results demonstrated that early disturbances compromise bond performances by weakening chemical adherence and mechanical interlocking effects, which considerably degrade bond strength and stiffness. The presence of EA delayed the setting and hydration of concrete and prolonged vibration-sensitive duration. However, the later expansive hydrate products effectively strengthen the bond performances and compensate for early-stage vibration-induced damage. In comparison, the synergetic effects between CSA and Portland markedly enhance the hydration reactivity of blends at early stages, which can achieve threshold maturity and vibration resistance within hours. However, excessive CSA (10%) severely compromises the construction time of mixtures and amplifies the cracking potentials of HSC under the constraints of steel bars. The synergetic effects of steel fibers and aggregates formed disordered networks to enhance the vibration resistance and rigid skeletons for bridging cracks of HSC. The two-way ANOVA results indicate that EA significantly improves the mechanical performances of HSC, followed by steel fibers. The additions of expansive agents and steel fibers are highly recommended in engineering with vibration scenarios. In contrast, the dosages of CSA (or similar early-strength agents) should be carefully controlled unless with a robust shrinkage compensation strategy.

Zonal Isolation Material for Low-Temperature Shallow-Depth Application: Evaluation of Early Properties Development

Summary Shallow-depth cementing presents unique challenges due to its low temperature and low pore pressure characteristic. The curing process of the cementitious material is typically prolonged at low temperatures resulting in a delayed curing process. The use of a low-density slurry to mitigate low pore pressure introduces another challenge, as it leads to a reduction in the final compressive strength. On the other hand, the operation requires the material to develop enough strength swiftly to be able to efficiently continue the next drilling operation. In addition, the presence of flow zones such as shallow gas and shallow water flow increases the complexity of the cementing process. There have been many developments in cementitious materials for shallow-depth cementing such as rapid-hardening cement and gas tight cement. However, there is little research focusing on the performance evaluation of each material at low-temperature conditions. This paper aims to present a thorough material evaluation for low-temperature shallow-depth cementing. The incorporated materials are American Petroleum Institute (API) Class G cement, rapid-hardening cement, gas tight cement, and geopolymer. Geopolymer is included to evaluate its potential as the green alternative to Portland-based cement. The sets of characterization were conducted during the liquid, gel, and solid phases. The samples were prepared under wide-ranging low temperatures and typical bottomhole pressures for shallow sections. The result shows different performances of each material and its behavior under low temperatures such as prolonged strength development and low reactivity, which necessitates further development of these materials.

A rapid-hardening cement emulsified asphalt (CEA) mortar prepared from magnesium phosphate cement

Cement emulsified asphalt (CEA) mortar is the key component material of high-speed railway track slabs, and it is prone to damage under the coupling effect of environment and load. For severely damaged CEA mortar, the strategy of replacing the filling layer is required. However, the daily idle period of high-speed railways is extremely short in China, which makes Portland cement-based CEA mortar unable to meet the time and material performance requirements of high-speed railway maintenance. Therefore, a novel magnesium phosphate cement-based CEA (MEA) mortar is prepared in this study, and the effects of key parameters on its fresh properties, strength, and durability are systematically investigated. A MEA mortar with a setting time within 30 min and a compressive strength of 15–45 MPa is developed. Increasing the emulsified asphalt to cement (EA/C) ratio reduces the strength, water resistance, and frost resistance of MEA mortars, mainly because increasing the EA/C ratio leads to decreased reaction products and increased porosity. Meanwhile, increasing the EA/C ratio also leads to a higher volume expansion of the MEA mortar. In addition, adding an appropriate amount of emulsified asphalt with low water content can increase the setting time and failure strain of the MEA mixture compared with the plain magnesium phosphate cement component, and it performs better than emulsified asphalt with high water content. This study demonstrates acceptable performance of MEA mortar prepared with appropriate EA/C ratio and type of emulsified asphalt, which provides an alternative material for track slab maintenance.

Quantitative Verification of Concrete Formwork-Striking-Time Reduction by High Blaine Ordinary Portland Cement.

Type Ⅰ high Blaine ordinary Portland cement (IHB) possesses the same composition as that of type Ⅰ ordinary Portland cement; however, due to its high fineness, IHB exhibits properties that are similar to those of type Ⅲ rapid-hardening Portland cement, which can reduce the formwork striking time. However, to date, no quantitative research results regarding the construction-time-reduction effect of IHB have been reported. Therefore, this study conducted experiments to verify the formwork-striking-time reduction effect of concrete using IHB. Considering seasonal changes, the strength-development characteristics, according to the outside air temperature, were examined by modifying the curing temperature conditions (5, 10, and 20 °C). Furthermore, the achievable reduction in the concrete formwork striking time was quantitatively determined by comparing and analyzing with the linear interpolation and maturity methods for improving the accuracy of the formwork striking time. The experimental results indicated that, compared with ordinary cement, early formwork striking is possible using IHB, due to earlier strength development. Thus, IHB was confirmed to be effective for construction-time reduction through early formwork striking, and it can be used as a sufficient substitute for expensive rapid-hardening cement in sites and weather conditions where rapid hardening is required.

Belitic calcium sulfoaluminate cement subjected to sulfate attack and sulfuric acid

Belitic calcium sulfoaluminate (BCSA) cement is a hydraulic rapid-setting cement with a different composition and properties compared to portland cement. There is currently limited information about its sulfate resistance and its resistance to sulfuric acid is not known. The ASTM C1012, Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution and a modified ASTM C1012 accelerated method were used to compare the sulfate resistance of BCSA cement, portland cement (PC), and PC-fly ash blends. BCSA cement, citric acid dosages in BCSA cement mixes, PC, and PC-fly ash blends were examined through mortar bar expansion. The most sulfate-resistant mixes contained BCSA cement or a blend of PC and class F fly ash. Citric acid dosage did not appear to affect resistance of BCSA cement to sulfate attack. Resistance of PC, PC-fly ash blends, and BCSA cement to a sulfuric acid solution was also compared. Compressive strength and volumetric changes were measured after prolonged immersion in sulfuric acid. Water to cementitious material (w/cm) ratios and curing time for BCSA were also analyzed to establish if these factors influenced resistance to sulfuric acid attack. The most acid resistant mix contained a blend of PC and class F fly ash. A higher w/cm (0.56) was found to be more resistant against sulfuric acid attack when using BCSA, while differing cure times did not clearly indicate sulfuric acid resistance.

Evaluation of Basic Properties of Cement Asphalt Mortar Depending on Specific Surface Area of Nonionic Emulsified Asphalt

This study was designed to evaluate the physical properties of cement asphalt mortar (CA mortar) according to the specific surface area (SSA) of nonionic emulsified asphalt. CA mortar specimens were prepared using 3 types of nonionic emulsified asphalt with different SSA and 1 type of rapid hardening cement and sand, additives. The physical properties of CA mortar were evaluated by measuring the temperature variation, bleeding ratio, flow value, air content, compressive strength, and expansion ratio. Test results showed no temperature variation and bleeding in any CA mortar specimens, indicating that SSA change of emulsified asphalt did not induce material separation of the mortar. As a result of the flow value test and compressive strength test, it was confirmed that the flow value and compressive strength increase of specimen CAM-A3, with the largest SSA of emulsified asphalt, increased the hydration reaction rate between cement and emulsified asphalt. CAM-A1 and CAM-A2, which did not satisfy the standard of air content, required adjustment of amount of added anti-foaming agent (AFA) and air entraining agent (AEA). The expansion ratio of CAM-A1 exceeded the standard, because the amount of self-shrinkage caused by hydration reaction is less than the amount of expansion caused by addition of aluminum. To accurately analyze the effect on SSA of emulsified asphalt, additional studies such as tissue observation through a scanning electron microscope are needed.

Matching the Color Difference Between Asphalt Mixture and Cement Grouting Paste Used in Semi-flexible Pavement

In order to match the color difference between black asphalt mixture and light-colored cement grouting paste in semiflexible pavement, carbon black (CB) with four mass ratios (i.e., 2, 4, 6, and 8%) was incorporated into a rapid-hardening cement grouting paste. The fluidity, color difference, spectrum reflectance, thermal conductivity, and flexural and compressive strength of the aforementioned cement pastes were experimentally investigated. The results show that the mass ratios of the component in cement paste could ensure the good fluidity of cement grouting paste. Three parameters such as thermal conductivity, flexural strength, and compressive strength all reduced, compared with control paste. However, the compressive strength of the 8% CB paste was still much higher than that of the asphalt mixture. According to the color difference results, CB significantly improved the black color of cement paste, of which the black color of the asphalt mixture was between that of 6 and 8% CB cement paste. Besides, the spectrum reflectance of all the pastes reduced, especially the average reflectance of 2% CB cement paste was 51.7% lower than that of control paste. The findings in this study are expected to help design more advanced cement grouting materials to improve the optical and mechanical performances of semiflexible asphalt pavement.

Using ground blast-furnace slag grouts with biopolymer additives for improving sandy soils

The mechanical performance of microfine ground-granulated blast-furnace slag grouts for improving sandy soils was evaluated using unconfined compressive strength, drained triaxial compression and Brazilian tensile strength tests of grouted sand specimens. Two activator types, namely sodium hydroxide and rapid-hardening cement (RHC), and two biopolymer additives, namely xanthan gum (XG) and diutan gum (DG), were investigated for slag-based grouts prepared at various water–binder (w/b) ratios. The bench-scale investigation examined the cured strength properties of grouted sand specimens. It was observed that the RHC activator with modest biopolymer additive and smaller w/b ratio resulted in markedly higher strength gains. In terms of activator type, compared to sodium hydroxide, the RHC resulted in significantly better performance, mobilising increased cohesion in specimens tested in drained triaxial compression. When used together with slag grouts, XG and DG mostly showed comparable strength improvements, but DG proved more effective at lower dosage in increasing tensile strength of grouted sand.

Thermo-alkali activation of talc for the production of a novel white one-part alkali-activated magnesia-based cement

This work focuses on the fabrication of white one-part alkali-activated magnesia-based cement (AAMC) using the vitrification of talc (Tc) in the presence of NaOH or NaAlO2. The results revealed that regardless of Na2O-source, increasing alkali-activator content (up to Na2O/Tc of 0.15) enhances the transformation of Tc from crystalline into amorphous structure with high hydraulic reactivity. Comparing to white Portland cement, one-part-AAMC synthesized in the presence of NaAlO2 shows higher early compressive strength, higher whiteness, and lower bulk density. This improves the capability of utilizing this mixture as a lightweight and a rapid-hardening cement in prestige construction projects and decorative works.

Strength and Water-Repelling Properties of Cement Mortar Mixed with Water Repellents.

In this study, the compressive strength and water contact angle of mortar specimens prepared by mixing two types of water repellent with ordinary Portland cement (OPC) and rapid-hardening cement mortar were measured before and after surface abrasion. In addition, the hydration products and chemical bonding of cement mortar with the repellents were examined using X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), and Fourier-transform infrared spectroscopy (FT-IR) to evaluate the performance of these cement mortar mixtures as repair materials. We found that the fast-hardening cement mortar mixture containing the oligomer water repellent showed the best performance with a high compressive strength and large water contact angle. With the oligomer water repellent, the rapid-hardening cement mortar mixture showed contact angles of 131° and 126° even after a 2 mm abrasion, thereby confirming that the water repellent secured hydrophobicity through strong bonding with the entire cement mortar as well as its surface. The compressive strengths were found to be 34.5 MPa at 3 h and 54.8 MPa at 28 days, confirming that hydration occurred well despite the addition of water repellent.

Mechanical and Durability Properties of Latex-Modified Hybrid Fiber-Reinforced Roller-Compacted Rapid-Set Cement Concrete for Pavement Repair.

This study evaluated the mechanical properties and durability performance of latex-modified hybrid fiber-reinforced roller-compacted rapid-set cement concrete (LMHFRCRSC) for emergency repair of concrete pavement. Experimental parameters included the blend ratio of the hybrid fiber, which comprised natural jute fiber (0–0.2 vol.%) and structural synthetic fiber (0–2 vol.%). The mechanical performance of LMHFRCRSC of various blend ratios was evaluated in terms of compressive, flexural, and splitting tensile strength. Durability assessment included chlorine ion penetration and abrasion resistance measurements. Compressive and flexural strength values of 21 and 3.5 MPa, respectively, were the set targets after 4 h of curing; a compressive strength of 35 MPa, a flexural strength of 4.5 MPa, a splitting tensile strength of 4.2 MPa, and chloride ion penetration of 2000 C or less were required after 28 days of curing. Our test results confirmed that all mix proportions satisfied the target values, regardless of the blend ratio of the hybrid fiber. Specifically, the mechanical performance of the concrete improved as the blend ratio of the structural synthetic fiber increased. With regard to durability, a greater amount of jute fiber, a hydrophilic fiber, enhanced the concrete’s durability. Additionally, incorporating jute fiber of 0.6 kg/m3 provided excellent chlorine ion penetration resistance. The optimal blend ratio for the hybrid fiber was natural jute fiber at 0.6 kg/m3 and structural synthetic fiber at 13.65 kg/m3 (mix: J0.6 + P13.65); with this mix proportion, a chloride ion penetration amount of 1000 C or less and maximum mechanical performance were achieved.

Strength and Durability of Hybrid Fiber-Reinforced Latex-Modified Rapid-Set Cement Preplaced Concrete for Emergency Concrete Pavement Repair

The benefits of using reinforcing fibers in latex-modified rapid-set cement preplaced concrete for emergency pavement repairs were examined in terms of strength, permeability, and durability as functions of the type of fiber. Single-type fibers, including jute, poly (vinyl alcohol) (PVA), and nylon fibers, as well as hybrid fiber mixtures prepared with two of the aforementioned fibers at a 1:1 weight ratio, were evaluated. Fibers were incorporated into the concrete mixture at 1.2 kg/m3. A vibratory press compactor that simulates roller compaction was used to increase compaction and densification of the resulting pavement repair material. The hybrid fiber-reinforced latex-modified rapid-set cement preplaced concrete (HFLMC) was manufactured to satisfy the criteria for opening traffic, i.e., compressive strength of 21 MPa or higher, and flexural strength of 3.5 MPa or higher after 4 h. Pavement requiring repair was removed and replaced with coarse aggregate. The rapid-set binder, fibers, and latex were then mixed and placed onto the coarse aggregate layer. The repair was considered complete after compaction. The resulting HFLMC satisfied all of the test criteria. Furthermore, concretes made with hybrid fibers were more mechanically sound than those made with a single fiber variety. Hybrid fiber concretes made with PVA and nylon fibers exhibited the best properties for emergency pavement repair. These results indicate that HFLMC is suitable for emergency pavement repair.

Monitoring Hardening Behavior of Cementitious Materials Using Contactless Ultrasonic Method.

We propose a novel contactless ultrasonic method for monitoring the hardening behavior of cementitious materials. The goal of this method is to obtain high-quality data to compare the unique hardening process between rapid setting cement (RSC) and ordinary Portland cement (OPC) mortars without physical coupling to the surface of the specimens. To monitor the hardening behavior of cementitious materials, conventional approaches use contact or embedded-type sensors, which limit field application. Our solution is to measure leaky Rayleigh waves at the interface between air and cementitious materials, which allows for the estimation of the physical state of the medium in real time. The modulus development was back-calculated based on the increment of wave velocity using the developed sensor array and transform-based signal processing. We experimentally demonstrated that the proposed method possibly exhibits unique hardening information about flash setting, effects of a retarder, and modulus increments from RSC specimens.

Exploring the Effects of Pozzolans on Different types of Portland Cements in Sustainable Cement-Based Applications

The sources of pozzolans could be natural, industrial and agricultural wastes that are recycled into concrete and mortar applications. There have also been many studies and recommendations guiding the use of blending these pozzolans from multiple sources with cement with the aim of producing more durable, greener and sustainable mortar/concrete. These investigations are mostly based on testing these pozzolans with a certain type of cement and making recommendations on the optimum percentage replacements. This type of study underscores that a pozzolan can behave differently with other types of Portland cements with varying distinct chemical compositions that associate the cement with its type. This could result to a particular pozzolan having different optimum percentage cement replacements with different types of cement and hence results in less durable concrete of which this study intends to address. The pozzolan used in this study is Pulverized Calcined Clay (PCC) and the types of cement is based on the British and American standards classification. The cement variants used in this study is broadly rapid hardening and low heat cement form the two (2) major cement brands in Nigeria. The X-Ray Fluorescence (XRF) analysis was performed on the cements and the PCC to determine their oxide compositions and classify the pozzolan, the Strength activity index (SAI) of the pozzolan was also determined. The optimum percentage replacements (replacement level with maximum strength) of the cements with the pozzolan was also determined. The results indicate that the optimum replacements for the low-heat cement was at 20% replacement with PCC and substantially higher for the rapid-hardening cement. This could be adduced to the difference in the chemical compositions as shown in the XRF analysis. It was concluded that the optimum replacement of different cement types with a pozzolan could vary, resulting to less durable concrete when a single optimum replacement is recommended across all cement types. It is therefore recommended that the optimum replacements of cements with pozzolans should be specific to a cement type and recommended that optimum replacement for other cement types with same pozzolan be determined and not generalized across all cements.

Rheological and strength properties of fly ash incorporated rapid hardening cement mix

Rapid Hardening Portland Cement (RHPC) is used in sites where high initial strength is required and or at instances where removal of formwork is to be done at an early stage. It is widely used in the manufacture of concrete bricks and in mining plants. The main issue regarding RHPC is its high heat of hydration. Addition of Fly Ash can be taken as one of the solutions for this problem. This project investigates in reducing the heat of hydration of RHPC using fly ash. For determining the most optimum cement-fly ash mixture, compressive strength of each mixture with varying fly ash composition was obtained. The cubes were cast with 15%, 25% and 35% of both Class-F and Class-C fly ash. As a result of consistency test, water cement ratio for each mixture was found and used for the proper casting of the cubes. The influence of fly ash on the, mechanical properties (compressive strength) and rheological (yield stress and plastic viscosity) properties of rapid hardening cement as well as the chemical interaction between fly ash and rapid hardening cement were systematically investigated. As a result, the mixture with 25% Class-F showed the maximum compressive strength. It is also observed that yield stress and plastic viscosity changes with fly ash percentage and type.

Field Performance of Low-Cracking Concretes for the Closure Pours and Overlays of Bridge Decks

Joints, wide cracks, and poor quality concretes facilitate the intrusion of chlorides, causing corrosion in bridge decks and substructures that limit the service lives. Distress in deck concretes can adversely affect ride quality and structural integrity. The objective of this study was to eliminate the joints in existing bridges and to improve the surface conditions of the decks by overlays. Two parallel bridges in Virginia were selected for study. The performance of the closure pours and overlays was observed for 4–5 years. Joints were replaced with closure pours (also known as link slabs) consisting of fiber-reinforced concretes resistant to wide cracking and intrusion of solutions. Polyvinyl alcohol, polypropylene, and steel fibers were used in the closure pours; a compressive strength of 3,000 psi (pounds per square inch) at 24 h was sought. In the overlays, silica fume concrete alone and with shrinkage reducing admixture, lightweight coarse aggregate, and lightweight fine aggregate was investigated for crack control and low permeability, and compared with the control of latex-modified concrete with rapid set cement. A compressive strength of 3,000 psi at 3 days was sought. Test results and surveys showed that satisfactory strengths and permeability were achieved; the closure pours containing steel and polyvinyl alcohol fibers had tight cracks (most less than 0.1 mm with a few up to 0.2 mm). All overlays were performing well except for one section placed in adverse weather conditions and exposed to a truck fire. There were a few areas patched where poor surface preparation had led to delamination.

Assessment of Leaching Characteristics for Cerium and Cesium as Surrogates for Radioactive Materials

The leaching behavior of cerium and cesium from different mixtures of rapid setting cement (RSC) with deionized water (DIW) and artificial seawater (ASW) under both dynamic and static leach conditions was investigated according to the method in American National Standard ANSI/ANS-16.1-2003. The leachate solution was collected, diluted with HNO3, and analyzed using inductively coupled plasma–mass spectrometry after leaching periods of 2, 7, and 24 h and 2, 3, 4, 5, 14, 28, 43, and 90 days. Two models [the first-order reaction model (FRM) and the diffusion model (DM)] and their combination [the first-order reaction/diffusion model (FRDM)] were fitted to assess the leaching parameters and identify the type of immobilized radionuclides in the RSC matrix. The result indicated that leaching of 140Ce and 133Cs from the RSC matrices with DIW and ASW under both dynamic and static leach conditions was less than 20% and suggested that the leaching behavior of 140Ce and 133Cs approximated that of a semi-infinite medium. The leaching phenomena of 140Ce and 133Cs could not be fully represented with a single model (the FRM and the DM), and the FRDM was best fitted to these experimental data sets. Overall, the average leachability index L values for 140Ce and 133Cs were greater than the minimum limit indicating their acceptance for disposal recommended by the International Atomic Energy Agency. It could also be stated that RSC with DIW or ASW had a potential for immobilizing radioactive materials.

Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period

Abstract This research investigates the effect of capillary pressure and the length of the hydration dormant period on the plastic shrinkage cracking tendency of SCC by studying specimens produced with different w/c ratios, cement types and SP dosages. A relationship between the capillary pressure rate and the length of the hydration dormant period is defined, which can explain the cracking severity of the concrete when the volumetric deformation is unknown. The results show, that the cracking tendency of SCC was the lowest in case of w/c ratio between 0.45 and 0.55, finer and more rapid hardening cement, and lower dosage of SP. The dormant period was prolonged by increasing the w/c ratio, using coarser cement, and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure buildup rate and the length of the dormant period.

Strength and durability of rapid set PVA fiber reinforced LMC for pavement repair

This study evaluated the strength properties, chloride ion permeability and abrasion resistance of styrene–butadiene latex-modified polyvinyl alcohol (PVA) fibre-reinforced rapid-set cement concrete (LMFRRSC) for application to emergency repair of concrete pavements. Experiments were conducted to measure the compressive strength, flexural strength, splitting tensile strength, bond strength, chloride ion penetration and abrasion resistance of LMFRRSC for variable PVA fibre content (0, 0.05 and 0.10%); test results showed that these test parameters increased with the volume fraction of PVA fibre, satisfying all traffic-opening criteria for emergency concrete pavement repair. The PVA fibre additive effectively minimized crack formation generated as a result of high hydration heat in the early material stages and inhibited fibre ball development. Thus, the addition of PVA fibre enhanced the performance of LMFRRSC for emergency repair of concrete pavements.