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Cow dung waste has caused severe environmental pollution and public health issues in China. In this study, the cow dung residues were used as a cheap renewable fiber to modify asphalt binder, providing a new solution for the proper disposal of cow dung waste. Three cow dung fibers with two lengths were prepared using different treatments, including original cow dung fiber (CDF), surface treatments of cow dung fiber (STCDF) and alkali treatments of cow dung fiber (ATCDF). The physicochemical properties of CDF, STCDF and ATCDF were analyzed by scanning electron microscope (SEM) and thermogravimetry (TG). The viscidity, rheological properties and fatigue characteristics of CDF modified asphalt binders (CDFMA) were evaluated using Brookfield viscometer and dynamic shear rheometer. The results showed that the rough surfaces of STCDF and ATCDF improved their thermal stability. STCDF and ATCDF enhanced the resistance to permanent deformation under high temperature conditions of modified asphalt binder. STCDF modified asphalt binders exhibited the best viscosity and rheological performance. The increase of fiber length was positively correlated with the high temperature deformation resistance of CDFMA. CDF, STCDF and ATCDF inhibited fatigue cracking of modified asphalt binders compared to base asphalt binders. ATCDF modified asphalt binders exhibited higher fatigue life and smaller crack under the same cyclic loading. The increase in fiber length had a slight improvement on the fatigue resistance of modified asphalt binders., Pavement Engineering

Internal curing by superabsorbent polymer (SAP) has been applied in alkali-activated slag (AAS) systems by a few previous studies with the purpose to mitigate the autogenous shrinkage. However, the effects of SAP on other properties of AAS have been rarely studied. In this paper, the workability, strength, permeability, and frost resistance of AAS mortar with synthesized SAP are investigated besides the autogenous shrinkage. Two SAP introducing ways (dry mixing and wet mixing) are considered. It is found that the flowability of AAS mortar decreases with the increase of SAP dosage regardless of the introducing way. The strength and permeability increase with the SAP dosage when it is below a certain amount depending on the mixing way. The autogenous shrinkage can be mitigated significantly by the incorporation of SAP and the mitigating effect is more pronounced by wet mixing. The frost resistance becomes better when more SAP is introduced in either way. The mechanisms behind these phenomena are explained based on the characterization results on the reaction kinetics, reaction products and pore structure of the mixtures with SAP., Materials and Environment

The influences of liquid-binder ratio and mixing sequence on the performance of superabsorbent polymer (SAP)-containing alkali-activated slag (AAS) mortar are investigated in this study. It is found that the SAP absorbs much less liquid in upper supernatant of AAS than in water. Mixing SAP with liquid first induces a larger absorption capacity of the SAP than mixing it with solid first. Increasing the liquid-binder ratio improves the flowability but reduces the strength of AAS mortar with SAP. Nonetheless, the strength of internally cured mixtures is higher than that of the reference even with an extra liquid-binder ratio of 0.09. The reason behind lies in the refinement of capillary and gel porosity by internal curing, despite the presence of large voids originated from SAP. The autogenous shrinkage of AAS paste is reduced significantly by the incorporation of SAP but the further mitigating effect of increased liquid-binder ratio is limited., Materials and Environment

Reliable characterization of the pore structure is essentially important for transport-related durability studies of cementitious materials. Mercury intrusion porosimetry has been commonly used for pore structure measurement while the ink-bottle effect significantly affects the trustworthiness of pore size features of cementitious materials. Pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP) is an alternative approach previously reported with the purpose to provide better estimates of pore size results. It is found however that the PDC-MIP greatly overestimates the ink-bottle pore volume owing to the incomplete extrusion of mercury in throat pores after the pressurization-depressurization cycle. Intrusion-extrusion cyclic mercury porosimetry (IEC-MIP), as a further improvement, is then described, which can reliably capture the ink-bottle effect and obtain a clear picture of the distribution of the ink-bottle pores in cementitious materials. The ink-bottle effect of cement pastes is observed being pore size-dependent and the role of critical pores is emphasized. Water-cement ratio primarily changes the effective porosity while plays a minor role in the ink-bottle porosity. The addition of reactive blends substantially enhances the ink-bottle effect during mercury penetration into small pores. IEC-MIP tests, together with a unique data analysis, enable to obtain a more truthful pore size distribution., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Environment

The proper disposal of steel slag has always been a great challenge for the metallurgical industry in China and around the world. In this work, the steel slag aggregate (SSA) was surface pretreated (PSSA) and applied into asphalt mixture. The adhesive behavior between the bitumen and five different types of aggregates (i.e., limestone, diorite, diabase, SSA, PSSA) were evaluated based on the contact angle and binder bond strength tests. The pavement performance of three asphalt mixtures which contain normal aggregate, SSA and PSSA respectively, was analyzed by Marshall stability test, wheel-tracking rutting test, low-temperature bending creep test and water sensitivity test. The results showed that surface modification can improve the surface properties of SSA, reduce its contact angle with bitumen, and eventually lead to the improvement of adhesion between them. In addition to the satisfied low-temperature properties, PSSA was found to significantly improve the anti-rutting property and reduce the water sensitivity of asphalt mixture. This work is expected to promote an alternative application for recycling of SSA in pavement engineering., Pavement Engineering

Durability of photocatalytic coatings is a major concern in engineering practice. Here, two types of novel visible light-responsive coatings, both consisting of vinyl chloride/vinyl ester/ethylene copolymer (as a binder) and graphitic carbon nitride (g-C3N4) but different in fabrication, are proposed and applied on the mortar surface. The first type is mono-layer coating (MC), where the g-C3N4 suspension containing the binder is directly sprayed on the mortar. The second type is double-layer coating (DC), where the binder layer is applied on mortar surface before spraying the g-C3N4 layer. Results show that the binder addition leads to a good anchorage of the coatings on both MC and DC mortar substrates, along with desirable resistance to peeling and washing, compared to the g-C3N4 coated mortar without the binder. The well-distributed binder in g-C3N4-based coating inevitably decreases the photocatalytic efficiency of the MC mortar due to masking effect of the binder on the coating surface. The DC mortar, on the contrary, takes full advantage of the binder adhesion by inserting a binder layer and therefore holds strong resistance to peeling and washing without compromising its photocatalytic efficiency. The proposed DC technique provides a promising strategy to fabricate highly cost-effective and durable photocatalytic coatings applied on cementitious materials., Accepted Author Manuscript, Materials and Environment

Conceptual analysis is performed to examine the effects of pore features on the water continuity in unsaturated porous systems. The roles of pore features in relative chloride diffusion coefficient (Drc) of mortar specimens at various degrees of water saturation (Sw) were studied based on mercury intrusion porosimetry and resistivity tests. It is found that the role of pore structure in the Drc-Sw relationship is a result of its effect on the water continuity. Porosity and tortuosity are not relevant to the Drc-Sw relationship. A finer pore size distribution or lower pore connectivity tends to result in a lower Drc. The pore size effect on the Drc is pronounced primarily at high Sw, while the Drc is dominated by the pore connectivity at low Sw. Cement mortar with a higher water-to-binder ratio shows larger chloride diffusion at high relative humidity levels but smaller chloride diffusion at low relative humidity levels., Accepted Author Manuscript, Materials and Environment

Pumping is the most common technique used to transport fresh concrete in construction sites. The large-scale use of concrete all over the world makes the pumping increasingly important. A wide variety of additives and admixtures are incorporated into modern concrete in order for sustainable development. The performance of modern concrete is rather complex and its pumping behavior differs significantly from that of conventional concrete, especially in the fresh stage. This paper presents a comprehensive overview on the state of the art of concrete pumping. The models and methods used for characterizing the concrete pumpability and lubrication layer are described. The factors influencing the pumping behavior are discussed. A couple of ultra-high pumping engineering of concrete conducted in China are introduced., Accepted Author Manuscript, Materials and Environment

Rheological properties are of significant importance in successful placement and performance of self-compacting concrete (SCC). In this work, the rheological properties of SCC, combined with a powder-viscosity modifying admixture, were investigated based on a series of experimental studies. The modified Bingham model was applied to determine the rheological parameters and shear thickening behavior of SCC. The effects of mixing procedures, including charging sequence, mixing time and mixing speed, were analyzed. The results show that the shear thickening of SCC is reduced by first mixing the aggregate and water and then adding other raw materials. The direct contact between aggregate and water leads to a large amount of free water to be adsorbed by the aggregate system, resulting in an increase of the yield stress. In order to ensure an excellent fluidity and a low shear thickening behavior of SCC, the mixing time should be controlled at 4-5 min and the mixing speed at 30-45 r/min., Materials and Environment

Microstructure-property relationship has drawn strong attention in modern material science. The progress achieved in this field relies on a common basis that the material performance originates from the microstructure. This paper brings together new insights and facts from experiments regarding the pore size dependent connectivity and its relation to ionic transport property in saturated cementitious materials. An innovative measurement, i.e. intrusion-extrusion cyclic mercury porosimetry (IEC-MIP), is proposed to distinguish between the small capillary pores that are present within clusters of hydration products and the large capillary pores that are left out of hydration products. The distribution of connectivity as a function of pore size in cementitious materials is analyzed. A novel transport parameter, i.e. connectivity of small capillary pores, is introduced and quantified by IEC-MIP measurements. The ionic transport was measured by means of rapid chloride migration tests. A power relationship is established between connectivity of small capillary pores and chloride migration coefficient for cementitious materials irrespective of the binder type., Accepted Author Manuscript, Materials and Environment

Concrete is rarely saturated. Reliable durability design of marine concrete structures requires a solid understanding of the long-term chloride transport in unsaturated concretes. This paper presents a critical analysis of the time-dependent chloride diffusion coefficient in unsaturated cementitious materials exposed to marine environment. Evolutions of pore structure and chloride diffusion coefficient in saturated cementitious materials, along with the role of the degree of water saturation in long-term chloride diffusion, are analyzed. It is emphasized that the long-term sharp decrease of the chloride diffusion coefficient in marine cementitious materials is not primarily caused by densification of the microstructure due to hydration, but by the decreasing degree of water saturation with depth in the surface part of the materials. The effects of water/binder ratio and supplementary cementitious materials on chloride diffusion coefficient are different between saturated and unsaturated cementitious materials., Accepted Author Manuscript, Materials and Environment

Capturing the long-term performance of concrete must be underpinned by a detailed understanding of the pore structure. Mercury intrusion porosimetry (MIP) is a widely used technique for pore structure characterization. However, it has been proven inappropriate to measure the pore size distribution of cementitious materials due to the ink-bottle effect. MIP with cyclic pressurization-depressurization can overcome the ink-bottle effect and enables a distinction between large (ink-bottle) pores and small (throat) pores. In this paper, pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP) is adopted to characterize the pore structure in a range of cementitious pastes cured from 28 to 370 days. The results indicate that PDC-MIP provides a more accurate estimation of the pore size distribution in cementitious pastes than the standard MIP. Bimodal pore size distributions can be obtained by performing PDC-MIP measurements on cementitious pastes, regardless of the age. Water-binder ratio, fly ash and limestone powder have considerable influences on the formation of capillary pores ranging from 0.01 to 0.5 μm., Materials and Environment

The internal relative humidity (RH) plays a crucial role in most of the concrete properties. Self-desiccation caused by continuous cement hydration is a major factor affecting the RH of concrete. This paper investigates the relationship between RH and microstructure for cementitious systems in the case of self-desiccation. A series of paste specimens prepared with different binder and water-binder-ratio (w/b) were cured under sealed conditions from 1 day to 1.5 years. The RH and microstructure of the paste specimens were measured. The microstructure characteristics under study include porosity, pore size, evaporable and non-evaporable water content. The results reveal that the RH of cementitious system drops to a great extent in the first 105 days' hydration and decreases slowly afterwards. The blended materials such as fly ash, slag or limestone powder have different influences on the RH. A mathematical model between RH and the average pore diameter is proposed for cementitious systems under self-desiccation, regardless of age, w/b or cement type., Materials and Environment