Guangcheng Long

Efficiency of waste tire rubber aggregate on the rheological properties and compressive strength of cementitious materials

A serial of experiments were carried out to investigate the efficiency of waste tire rubber on consistency and rheological behavior of cementitious materials at fresh state and on the mechanical strength at hardened state was evaluated. Results indicate that the addition of rubber aggregates significantly influences yield stress of the sample in the fresh state and the compressive strength at 28 days, depending on the grain size distribution of the rubber aggregate and its volume percentage in the mixture. The yield stress of the sample in fresh state is more influenced by an increasing volume of rubber compared to adding sand with equal grain size distribution. The percentage of reduction of compressive strength of cementitious materials caused by increasing the volume of rubber aggregates by 1% is about 4.5%.

Self-Compacting Concrete Reinforced by Waste Tyre Rubber Particle and Emulsified Asphalt

For the sake of developing new cementitious materials with high toughness and excellent workability, an extensive research programme was set up to investigate the properties of self-compacting concrete (SCC) with waste tyre rubber particles and emulsified asphalt in fresh state and hardened state. The effects of rubber particles and emulsified asphalt on strength, dynamic elastic modulus, stress-strain response and impact toughness of hardened SCC were analyzed in detail. Results indicate that rubber particle and emulsified asphalt remarkably influence mechanical properties of SCC. Incorporating rubber particles together with emulsified asphalt is conducive to improve self-compactability of fresh SCC. The strain capability and toughness of SCC can be greatly enhanced by addition of rubber particle and emulsified asphalt. A combination of rubber particles and emulsified asphalt is an effective way to prepare new SCC with excellent dynamic mechanical properties.

Application of Non-Destructive Technology in Evaluating Concrete to Sulfate Attack

The deterioration on sulfate attack was investigated both in physical crystallization and the chemical erosion. Specimens that suffered long-term immersion and dry-wet cycles in saturated sodium sulfate solution are compared to trace the physical attack. And the chemical erosion was conducted by comparing specimens which have been suffered long-term immersion in saturated sodium sulfate solution and saturated limestone solution. In the investigation, the non-destructive detecting indexes, such as the ultrasonic velocity, and the dynamic modulus of elasticity were measured. The permeability, the porosity and mechanical strength at 28-day age were measured. The flexural/compressive strength was measured after 90 wet-dry cycles. And then all the specimens were cut into cubes to take the measure of compressive strength. Based on the experiments, feasibility of various parameters, such permeability, relative dynamic modulus of elasticity, ultrasonic velocity and relative flexural/compressive strength, were investigated to evaluate the concrete deterioration. The results indicate that there is a close relationship between the deterioration by sulfate attack and concrete permeability, so the reduction of permeability is effective in promoting the resistance. The index of the resistance expressed by the dynamic modulus of elasticity ratio is comparable to that expressed by the relative flexural strength. A novel method was suggested in evaluating concrete by sulfate attack, namely, combined with some mechanical tests, the parameter of relative dynamic modulus of elasticity can be used to evaluate the deterioration; the permeability denoted as the amount of transporting charges within 6 hours can be used to evaluate the properties to sulfate attack.

Experimental study on performance of imitative RPC for sulphate leaching

Abstract This paper presents a manufacturing process to make an imitative RPC material. The blend was regularly composed of cement, silica fume, and certain content of rubber powder. The granular size distribution of dry blend was optimized to reduce the porosity of set material and the imitative RPC material was characterized by high silica fume content and with very low water to binder ratio. Furthermore, fine crushed aggregate and local natural medium crude sand were used to form mineral skeleton. Properties of various reference concrete series were investigated by conducting multiple tests, including permeability and mechanical strength test, the salt solution absorption test, the accelerated sulphate attack test, etc. The results show that the imitative RPC is an environmental-friendly civil engineering material which owns favorable mechanical strength, high impermeability and qualified excellent durability in sulphate contained environment.

Efficiency of Scrap Rubber Particles on Strength of Cementitious Materials

An extensive research programme was set up to investigate the efficiency of scrap rubber particles on strength of cementitious materials. The index of strength loss rate of paste and mortar sample caused by increasing 1% volume rubber particles was proposed to analyze the efficiency of rubber particles in cementitious materials. And the corresponding mechanism was also discussed in this paper. Results indicate that in the investigated area, the loss rate in compressive strength both for paste and mortar almost ranges from 2% to 5% caused by increasing 1% rubber particles depending on the total volume of rubber particle added into sample. However, the loss rate in flexural strength of mortar by increasing 1% volume rubber particles is obviously different from that. Three roles of scrap rubber particles played in cementitious materials, named as deformation effect, equivalent-pore effect and hydrophobic effect, are responsible for the efficiency of scrap rubber particles on strength of cementitious material. The efficiency of rubber particles on strength of paste and mortar differs from each other due to the different microstructure between paste and mortar.

Water Sorptivity and Permability of New-Old Concrete Composite System

Several experiments were carried out to investigate the effects of water to binder ratio(w/b) and mineral admixtures on water sorptivity and permeability of new-old concrete composite system in this paper in order to further understand the transport properties and thus degradation mechanism of new-old concrete repair system. Results indicate that a reasonable choice of w/b of new concrete is of great importance for obtaining new-old concrete composite with a low water sorptivity. Addition of ultrafine powder such as silica fume as one of component of repairing materials will benefit for effectively reducing water sorptivity and permeability of new-old concrete repair system in practice. The linear correlative coefficient between capillary sorption coefficient, coulomb electricity and porosity of new-old concrete composite sample is bad and lower compared with those of corresponding new concrete samples. The total porosity of new-old concrete composite sample is not an exclusive factor determined its water sorptivity and permeability. The pore structure of new-old concrete composite sample, especially interfacial transition zone between new and old concrete plays more important role on transport properties of sample.

Experiment on Cement-Based Materials with Various Compositions against Sulfate Attack

According to the method of semi-immersion in 5% sodium sulfate solution, the property against sulfate attack of cement-based materials with various compositions are studied with the indexes of the amount of crystal salt in unit exposing area and the ratio of total mass change. The experiment indicates that the order of mortar with w/c=0.4 against sulfate attack from high to low are SAC 42.5>PO 42.5>Clinker>HAC 42.5. When w/b is constant and the cement was replaced by the same quantity of salic material, the order of mortar against sulfate attack are Clinker> PO 42.5> SAC 42.5> HAC 42.5. The replacement of SAC and HAC with the same quantity of salic material leads to the sharp decrease of its property against sulfate attack while the result is opposite for the clinker serial and PO 42.5 serial. Addition of redispersible polymer powder can lead to decrease of penetration and increase the properties of products to sulfate attack. Then, it comes to the conclusion that multi-binder with PO.42.5cement 70%–80% (quality percentage), and internal mixing of 5%–10% silica fume, 10%–15% fly ash can meet the high corrosion resistance requirements.

Ultraviolet irradiation of crumb rubber on mechanical performance and mechanism of rubberised asphalt

Nowadays, researchers have studied influences of ultraviolet on crumb rubber (CR)-modified asphalt (AR) and attempted to comprehensively understand mechanisms of ultraviolet on asphalt or AR entirety. In this article, ultraviolet influences on CR are discussed: mechanical performances of matrix asphalt, AR and strong ultraviolet-irradiated CR-modified asphalt are evaluated by dynamic mechanical analysis, bending beam rheometer and dynamic shearing rheometer (DSR); mechanisms of ultraviolet on CR, irradiated CR on asphalt and morphologies of CR are analysed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Results implied: (i) CR barely reacts with asphalt but irradiated CR reacts vigorously with asphalt by its new chemical bonds and growing internal crosslinkings; (ii) CR has a rough surface with porous shape and size but ultraviolet makes it become dense caused by oxidation; (iii) irradiated CR weakens low-temperature performances but enhances high-temperature anti-shearing performances of asphalt.

Effect of Strain Rate on Compressive Behavior and Modeling of Cement and Asphalt Mortar

AbstractThe compressive behavior of cement and asphalt mortar (CA mortar, including Types I and II CA mortar, namely CAI and CAII) under strain rates ranging from 10−5/s to 10−2/s was experimentall...

Properties of Self-Compacting Concrete Incorporating Rubber and Expanded Clay Aggregates

Self-Compacting Concrete (SCC) incorporating a blend of normal aggregate and waste rubber or expanded clay aggregate were prepared in present paper. And then the properties of SCC incorporating combined aggregates in fresh state and hardened state, including workability, dynamic elastic modulus, compressive strength and chloride ion permeability were investigated by experiments. Results indicate that utilization of rubber particles as a fine aggregate or expanded clay particles as a coarse aggregate by partially replacing sand or coarse aggregate of the same volume can successfully produce the SCC with suitable workability. The addition of rubber or expanded clay particles results in a remarkable reduction of mechanical strength and dynamic elastic modulus of SCC. And the compressive strength and dynamic elastic modulus of SCC with expanded clay aggregate replacing coarse aggregate is higher than that of SCC with the same volume rubber replacing sand. The incorporation of rubber or expanded clay aggregate in concrete exhibits a reduction in chloride ion permeability as compared to normal concrete. It is of great importance for further understanding the effect of waste rubber and expanded clay aggregate on workability, mechanical properties and durability of SCC.