Papers by Keyword: Dry Shrinkage

Abstract: In this study we investigate the addition of short polypropylene (PP) fibers in cement mortars for a wide volume percentage range. These fibers are dispersed easily in fresh mortar and create a dense network, whereas have as result the cracking reduction during dry shrinkage and the improvement of post peak response. A modified superplasticizer by lignosulfonate polymers basis was used, that keeps at low level the water to cement ratio and thus resulting to an improved mortar’s workability. Compressive strength, three-point flexural strength, drying shrinkage of hardened mortar, flow table test and air content of fresh mortar were studied in a range of volume percentages. The experimental response according to volume percentage was approximated by suitably attached theoretical models. The comparison of the obtained experimental values was done with unreinforced specimens as reference samples. From results elaboration it is concluded that the addition of PP fibers in cementitious mortars improves mortars post-peak response but weaken their compressive and flexural strengths and worsen their workability.

Abstract: The effects of the ratio of magnesium to phosphorus (Mg/P) on the compressive strength, bond strength, drying shrinkage and pH value of magnesium phosphate cement (MPC) were investigated. The results show that the consistent effect of the ratio of Mg/P on compressive strength and bond strength, as the ratio increases, the strengths are both first increased and then decreased, and the best ratio is 3:1. For setting time and drying shrinkage, the effects of the ratio of Mg/P are both obvious. Mainly manifested as the increase of the ratio, all of them show a decreasing trend. And the setting time can be shortened by 78%, furthermore, 28d the maximum drying shrinkage rate can be reduced by 29%. The effect of the ratio of Mg/P on pH value is mainly that when the ratio increases, the time of the inflection point of pH value is obviously advanced, and their final pH value is close.

Abstract: This paper studies on shrinkage performance of recycled asphalt pavement (RAP) material blended with inorganic binder such as cement, lime-fly ash (lime and fly ash) and three ashes (cement, lime and fly ash), with certain intensity used as base course. The erosion, dry shrinkage and temperature shrinkage tests were conducted on the recycled asphalt pavement (RAP) material blended with the three kinds of inorganic binder, to evaluate and compare different types of cold recycled inorganic material shrinkage resistance capability and anti-erosion properties. After analyzing the fatigue test result of three-additives-stabilized recycled mixture, it showed that the recycled pavement mixture owned preferable anti-erosion properties, anti-temperature shrinkage resistance and anti-dry shrinkage performance.

Abstract: In this study, the slag and metakaolin which contain rich elements of silica and aluminium were used to manufacture three types of composite geopolymer mortar: Type A (100% slag), Type B(70% slagand 30% metakaolin) and Type C(30% slag and70% metakaolin). Both the sodium hydroxide and sodium silicate solution were used as the activators. Experimental parameters included three ratios of SiO₂/Na₂O of 0.6, 0.7 and 0.8, three concentrations of alkali activator (7, 9 and 15%) and three water-to-solid ratios (0.33, 0.45 and 0.55), and four volumetric ratios of fine aggregate to whole mortar of 0, 10, 30, 50%, respectively. Two curing conditions of 50% relative humidity (RH), 25±2°C and 75% RH, 25±2°C were used for the dry shrinkage test. The results of study show that, at age of 28 days, the Type Bgeopolymer had the lowest drying shrinkage in the range between 450 and 760microstrains at 50%RH, and decreased to values between 270 and 340microstrainsat 70% RH.The average compressive strength of 89.3 MPa at age of 28 days for geopolymer mortar without metakaolin decreases to 74.7 MPa and 49.6 MPafor those with added metakaolin by 30 wt% to 70 wt%, respectively.

Abstract: The dry shrinkage deformation of polypropylene fiber mortar was analyzed by ANSYS software and compared with experiment value in this paper. The error of the calculated and experimental results in the 14 days and 28 days are 7.8% and 10.5%. It can be found that the calculated results are in good agreement with test results. The results indicate that the dry shrinkage value of polypropylene fiber mortar is lower than ordinary mortar. Adding polypropylene fibers can inhibit the process of cracking and improve the fracture toughness of cement-based materials.

Abstract: Effect of fly ash and slag on internal relative humidity (IRH) and dry shrinkage of light weight aggregate concrete (LWC) are studied in this paper. As indicated in this test, mixed with mineral additives can reduce dry shrinkage of concrete. The more volume of fly ash and slag ash, the lower decrease speed of IRH is, which contribute to the decreases of dry shrinkage rate too. At the same curing-age and dosage, the relative humidity inside the fly ash concrete is higher than the slag one. As consequence, the rate of dry shrinkage of fly ash concrete is lower than slag concrete. Also, there is a significant linear correlation between the lowered values of IRH and dry shrinkage rate.

Abstract: the influence of mixing amount of mineral admixture, volume content of fine and coarse aggregate have been systematical studied on the workability, mechanical properties and volume stability of self-compacting concrete. Test results showed that with the fly ash content increased, the workability of self-compacting concrete improved significantly, early compressive strength decreased, but increase rate of later strength improved remarkably, and the mixing amount of fly ash inhibited significantly the dry shrinkage of self-compacting concrete; with the volume content of coarse aggregate increased, the workability of self-compacting concrete decreased significantly, but the volume stability of self-compacting concrete improved obviously, thus the optimum volume content of coarse aggregate of self-compacting concrete was range from 0.30 to 0.34; when the volume content of fine aggregate varied at the range of 0.40~0.50, there may be little effects on the workability of self-compacting concrete, but the increase self-compacting concretes volume content could reduce obviously the dry shrinkage of self-compacting concrete. Moreover, the variation in the volume content of coarse and fine aggregate should have slight influence on the early strength of self-compacting concrete, and the influence of the volume content variety on the later strength of self-compacting concrete could be neglected eventually.

Abstract: The basic mechanical properties of RAP used as semi-rigid cement stabilized macadam base were researched. To add fiber to improve the crack resistance of the cement stable macadam mixture, reduce pavement reflection crack. Sixteen groups orthogonal experiment were arranged by the factors as cement, fiber, waste asphalt concrete and fly ash, the unconfined compression test, split test and drying shrinkage experiment were carried out. The results showed that the effect of the factors on the sensitivity of unconfined compression strength is obviously different, and from large to small order is cement, fly ash, fiber, waste asphalt concrete. RAP fiber cement stabilized macadam can satisfied with the strength requriments of base and subbase of all levels of the road. It should set cement and fly ash as the main control factors in the optimization design of RAP fiber cement stabilized macadam.

Abstract: In order to study the effect of several factors on the shrinkage performance of lime-fly ash stabilized crushed stone, temperature shrinkage coefficients and dry shrinkage coefficients of mixtures with different gradations, lime and fly content and age were measured. Results indicate that mixture with a stone-on-stone contact has better shrinkage-resistance performance; For the same gradation, both dry shrinkage coefficient and temperature coefficient become improved with lime-fly content increasing; when the lime-fly content is the same, temperature shrinkage coefficient increases with longer age; Results of analysis of variance show that to the temperature shrinkage coefficient, the effect of age and lime and fly content are important, and the latter is greater. To the dry shrinkage coefficient, gradation and lime and fly content are important factors, and the former is greater.

Abstract: Inorganic polymers using slag as cementitious materials have the advantage of a short setting time, high early strength, but the sensitivity of the reaction rate to temperature and the likelihood to subsequently crack, which leads to reduction of strength, limit its application. This article, by configuring different proportion of fly ash and slag, studied its dry shrinkage with the different kinds of activator, the effects of fly ash on the hydration heat release curves, differences of setting time and strength with different configuration, and then explored the effect of fly-ash in inorganic polymer. Experiments had shown that through rational configuration, the addition of fly ash can effectively reduce the rate of heat release and the amount of heat, meanwhile can solve the problem about short setting time of alkali-activated cementitious materials without reducing its strength.