Evaluation of Concrete Durability Based on Cloud Model and D-S Evidence Theory

The environment in alpine region is complex and harsh, and the durability of concrete is seriously affected by freeze-thaw and salt invasion. In this paper, the relative dynamic modulus of elasticity, chloride permeability coefficient, mass loss rate and carbonation depth are selected as the evaluation indexes of concrete durability in Northeast China. Based on prior knowledge and expert group decision-making, the durability grade is divided and the evaluation standard is established; The evaluation model of concrete durability based on cloud model and D-S evidence theory is established. According to the engineering experimental data, the membership degree of concrete durability evaluation index in different grades is obtained through the correlation measurement of cloud model. The normalized evidence is formed and fused by D-S evidence theory. The results show that the durability grade of concrete is grade I, which is consistent with the actual project. It shows that using cloud model and evidence theory evaluation model to evaluate the durability of concrete is a new and effective method.

Evaluation of synergic methods for corrosion protection of reinforced steel

Purpose This study aims to evaluate the effect of pH on the reinforced concrete steel protection for rebars coated with paint formulations containing talc and free from it. As the presence of talc in paints can offer high pH which cordially affects the protection behavior of the coated rebars. Additionally, this study includes evaluating the durability of concrete mixes in presence of some replacements of ordinary cement such as meta-kaolin (MK) and ground granulated blast furnace slag (GGBFS). Design/methodology/approach Two paint formulations were prepared containing the same ingredients except that (P1) is free from talc and (P2) contains talc. The anticorrosive behavior of painted steel in the blended concrete mixes containing MK and GGBFS was studied by using different electrochemical techniques in chloride solution. The concrete durability was evaluated by the means of compressive and bond strength beside chloride permeability. Different concrete mixes containing mineral groups or pozzolanic materials were prepared by replacing (10, and 30%) GGBFS and (5, 10 and 15%) MK as binary from cement CEM I with (w/b) 0.45 with superplasticizer ratio (SP) 2% of the binder Findings It was found that the presence of talc, in spite of its ability to offer high pH, has affected positively the corrosion behavior of reinforced concrete steel by forming a complex with concrete even if it is present in paint formulation and not free in the medium. Originality/value The results revealed that concrete blended with (30% GGBFS and 10% MK) with coated rebars with P2 containing talc showed the highest corrosion protection performance in addition to modified permeability and compression resistance.

Replacement of Conventional Concrete by Light Weight Concrete

Lightweight concrete (LWC) allows for larger spans, fewer piers, and longer bridge designs due to its lower weight and improved durability. Because superstructures with broader shoulders or additional lanes may be improved without requiring extensive work on the substructure, LWC is a particularly desirable construction material at the moment. The goal of this research was to determine the density (unit weight), splitting tensile strength, and elastic modulus of LWC mixtures under various curing circumstances in order to gain a better knowledge of LWC qualities that are critical for long-lasting and costeffective buildings. The researchers also looked at the relationship between the results of the fast chloride permeability test and the outcomes of other tests and the Werner probe surface resistance test to see if the latter may be used to forecast the permeability of LWC mixtures because it is faster and more convenient. Keywords: Light weight aggregate, pumice, compressive strength, density,

The Durability of High-Strength Concrete Containing Waste Tire Steel Fiber and Coal Fly Ash

The demands for high-strength concrete (HSC) have been increasing rapidly in the construction industry due to the requirements of thin and durable structural elements. HSC is highly brittle. Therefore, to augment its ductility behavior, expensive fibers are used. These negative drawbacks of HSC can be controlled by incorporating waste materials into its manufacturing instead of conventional ones. Therefore, this study assessed the performance of HSC produced with different quantities of waste tire steel fiber (WSF) and fly ash (FA). WSF was used at two doses, namely, 0.5% and 1%, by volume in HSC, with low-to-medium volumes of FA, that is, 10%–35%. The studied durability parameters included rapid chloride permeability (RCP) and chloride penetration depth (CPD) by immersion method (28 and 120 days) and acid attack resistance (AAR) (28 and 120 days). Various basic mechanical properties of HSC were also analyzed, such as compressive strength (fCM), modulus of elasticity (ECM), splitting-tensile strength (fCTM), and modulus of rupture (fCRM). The results revealed that the damaging effect of WSF on the RCP resistance of HSC is probably due to the high conductivity of steel fibers. However, test results of CPD showed that WSF produced insignificant changes in chloride permeability of HSC. Furthermore, when made with FA, WSF-reinforced HSC yielded very low chloride permeability. Both WSF and FA contributed to the improvement in the AAR of HSC. WSF was highly useful to tensile properties while it showed minor effects on compressive properties (fCM and ECM). Optimum ductility and durability can be achieved with HSC incorporating 1% WSF and 10%–15% FA.

Fresh, Mechanical, and Durability Properties of Self-Compacting Mortar Incorporating Alumina Nanoparticles and Rice Husk Ash

This paper presents a comprehensive evaluation on self-compacting (SC) mortars incorporating 0, 1, 3, and 5% alumina nanoparticles (NA) as well as 0% and 30% rice husk ash (RHA) used as Portland cement replacement. To evaluate the workability, mechanical, and durability performance of SC mortars incorporating NA and RHA, the fresh properties (slump flow diameter and V-funnel flow time), hardened properties (compressive strength, flexural strength, and ultrasonic pulse velocity), and durability properties (water absorption, rapid chloride permeability, and electrical resistivity) were determined. The results indicated that the addition of NA and RHA has negligible effect on the workability and water absorption rate of the SC mortars. However, significant compressive and flexural strength development was observed in the SC mortars treated with NA or the combination of NA and RHA. The introduction of RHA and NA also reduced the rapid chloride permeability and enhanced the electrical resistivity of the SC mortars significantly. It is concluded that the coexistence of 30% RHA and 3% NA as cement replacement in SC mortars can provide the best mechanical and durability performance.

The Donnan-dominated resting state of skeletal muscle fibers contributes to resilience and longevity in dystrophic fibers

Duchenne muscular dystrophy (DMD) is an X-linked dystrophin-minus muscle-wasting disease. Ion homeostasis in skeletal muscle fibers underperforms as DMD progresses. But though DMD renders these excitable cells intolerant of exertion, sodium overloaded, depolarized, and spontaneously contractile, they can survive for several decades. We show computationally that underpinning this longevity is a strikingly frugal, robust Pump-Leak/Donnan (P-L/D) ion homeostatic process. Unlike neurons, which operate with a costly “Pump-Leak–dominated” ion homeostatic steady state, skeletal muscle fibers operate with a low-cost “Donnan-dominated” ion homeostatic steady state that combines a large chloride permeability with an exceptionally small sodium permeability. Simultaneously, this combination keeps fiber excitability low and minimizes pump expenditures. As mechanically active, long-lived multinucleate cells, skeletal muscle fibers have evolved to handle overexertion, sarcolemmal tears, ischemic bouts, etc.; the frugality of their Donnan dominated steady state lets them maintain the outsized pump reserves that make them resilient during these inevitable transient emergencies. Here, P-L/D model variants challenged with DMD-type insult/injury (low pump-strength, overstimulation, leaky Nav and cation channels) show how chronic “nonosmotic” sodium overload (observed in DMD patients) develops. Profoundly severe DMD ion homeostatic insult/injury causes spontaneous firing (and, consequently, unwanted excitation–contraction coupling) that elicits cytotoxic swelling. Therefore, boosting operational pump-strength and/or diminishing sodium and cation channel leaks should help extend DMD fiber longevity.

Effects of Polyvinyl Alcohol fibers in engineered cementitious composite concrete

The present work majorly focused on the effect of Polyvinyl Alcohol fibers (PVA) in engineered cementitious composite concrete. However, PVA fibers are used as added to the ECC concrete with propotion of 0% to 2% of weight to cementitious materials. All the concrete samples are prepared with mix proportion of 1 cement: 1.1 silica fume: 0.36 ratio of sand/binder: 0.30 ratio of water/binder: 0.01 water reducer. whereas compressive, flexural, split tensile, water absorption and rapid chloride permeability tests are evaluated in order find out the performance of ECC with addition of PVA fibers. Thus, the results, ECC concrete has better mechanical and durability performance than conventional concrete and also its high early strength. From this study concludes that upto 1.5% of PVA fibers can be used in the ECC concrete, which has 60.12MPa and 18% of strength increment than the reference mix.

Experimental Investigation of Snail Shell-Based Cement Mortar: Mechanical Strength, Durability and Microstructure

Snail shells are the discarded bio-shell waste from restaurants, and oceans creating huge environmental problems for society. Living organisms are harmed when these shells are released. As previously stated, the work focuses primarily on the utilisation of snail shell powder as a raw ingredient in cement mortar. The mechanical and durability features of snail shell-based cement mortar were compared to the nominal mortar in this study. Snail shell powder, ranging from 0% to 35%, was used to partially substitute cement in mortar, with a variation of 5%. XRD (X-Ray Diffraction) was used to determine the chemical composition of both mixes. The mechanical properties of mortar for both mixes were determined using a compressive strength test. The tests on cement mortar viz., Water Absorption, Sorptivity, Acid Durability, and Rapid Chloride Permeability Test (RCP Test) were compared with nominal mortar mix. According to the results of the investigation, the optimum use of snail shell powder is 30%. The durability of both mixes increased by the increase of the snail shell powder. To detect the C-S-H gel formations, microstructural analysis was performed for both mixes.