Optimization of technical measures for improving high-temperature performance of asphalt-rubber mixture

Asphalt-rubber pavements often become dam-aged in high-temperature regions and appear rutted or wavy, and experience slippage. To improve the high-temperature performance of the asphalt-rubber mixture, technical measurements, such as, the optimal adjustment of gradation, technique of composite modification, and control of compaction were investigated. An optimal adjustment of aggregate gradation based on stone matrix asphalt improves the high-temperature stability of the asphaltrubber mixture significantly. Through composite modifi- cation, the effect of asphalt-rubber modification was enhanced, and the dynamic stability and relative defor- mation indices of the asphalt-rubber mixture were improved significantly. Furthermore, compaction parame- ters had a significant influence on the high-temperature stability of the asphalt-rubber mixture. The rolling times for compacting the asphalt-rubber mixture should be controlled to within 18-20 round-trips at a molding temperature at 180℃; if the rolling time is a 12 round-trip, the compaction temperature of the asphalt-rubber mixture should be controlled between 180 and 190℃.

Optimization of clay material mixture ratio and filling process in gypsum mine goaf

Because there is neither waste rock nor mill tailings in the gypsum mine, and the buildings on the goaf of gypsum mine are needed to be protected, the research proposed the scheme of the clay filling technology. Gypsum, cement, lime and water glass were used as adhesive, and the strength of different material ratios were investigated in this study. The influence factors of clay strength were obtained in the order of cement, gypsum, water glass and lime. The results show that the cement content is the determinant influence factor, and gypsum has positive effects, while the water glass can enhance both clay strength and the fluidity of the filing slurry. Furthermore, combining chaotic optimization method with neural network, the optimal ratio of composite cementing agent was obtained. The results show that the optimal ratio of water glass, cement, lime and clay (in quality) is 1.17:6.74:4.17:87.92 in the process of bottom self-flow filling, while the optimal ratio is 1.78:9.58:4.71:83.93 for roof-contacted filling. A novel filling process to fill in gypsum mine goaf with clay is established. The engineering practice shows that the filling cost is low, thus, notable economic benefit is achieved.

Moroccan Phosphogypsum Use in Road Engineering:Materials and Structure Optimization

Morocco produces annually large quantities of phosphogypsum(PG),which permanent stacking rises technical and environmental constraints.However,the valorization of this coproduct in civil engineering and especially in roads building,is a promising solution within a circular economy frame.A first experimental one-kilometer-long pilot,incorporating four different PG based formulations with a 7%cement addition,built at Safi in 2017,allowed positive mechanical assessment(by deflector)and environmental one(by leaching test).In order to further evaluate PG use as road material,our experimental approach focuses here on optimizing material mixtures-made of phosphogypsum(maximum content desired)treated with cement(to be minimized so as to reduce the cost)and sand or steel slag as granular corrector-to meet mechanical requirements of a road base material.We first identified and characterized phosphogypsum produced at the Jorf Lasfar plant and other materials used.Design of experiment is used for modeling desired physical and mechanical responses and to establish domains meeting the required criteria for using the mixture material either as road subgrade layer or foundation layer.In addition,through a parametric study,we evaluated the effects of traffic level,soil bearing capacity and mechanical performance of treated phosphogypsum mixtures on pavement design for three different pavement structures(mixed,reverse and structure with treated sub-base)and determined that the best to adopt for maximizing PG recycling is the pavement structure with subbase treated with hydraulic binder.

Optimization of the separation of a mixture of unknown composition by reversed-phase HPLC

A method is presented for the computer-assisted optimization of mobile phase selection for the separation of a synthetic intermediate of unknown composition by reversed- phase HPLC.The method is based on recognition of the order of the peaks by comparison of peak area ratio and followed by the BSOS-L(Binary Solvent Optimization System for HPLC)method.Excellent agreement was obtained between predicted data and experimental results.

Impacts of climate change on optimal mixture design of blended concrete considering carbonation and chloride ingress

Many studies on the mixture design of fly ash and slag ternary blended concrete have been conducted.However,these previous studies did not consider the effects of climate change,such as acceleration in the deterioration of durability,on mixture design.This study presents a procedure for the optimal mixture design of termary blended concrete considering climate change and durability.First,the costs of CO2 emissions and material are calculated based on the concrete mixture and unit prices.Total cost is equal to the sum of material cost and CO2 emissions cost,and is set as the objective function of the optimization.Second,strength,slump,carbonation,and chloride ingress models are used to evaluate concrete properties.The effect of different climate change scenarios on carbonation and chloride ingress is considered.A genetic algorithm is used to find the optimal mixture considering various constraints.Third,ilustrative examples are shown for mixture design of ternary blended concrete.The analysis results show that for termary blended concrete exposed to an atmospheric environment,a rich mix is necessary to meet the challenge of climate change,and for termary blended concrete exposed to a marine environment,the impact of climate change on mixture design is marginal.

Theoretical search for solutions to minimize negative influence of segregation in mixing of particulate solids

The objective of this study is to examine several optimization problems in the batch mixing of segregating particulate solids that can be set up and solved using Markov chain models. To improve the adequacy of such models and exclude some physical contradictions that arise in the linear form, a non-linear Markov chain model for the mixing of segregating components is proposed. Optimal solutions are obtained by controlling the particle flow outside the mixing operating volume while the components are being loaded, modifying particle circulation inside the mixing zone during the process, and by structuring the load in the mixing zone. Solutions are found that not only reduce the negative influence of segregation, but also exclude it altogether. The gain resulting from optimization grows with the rate of segregation. The optimal solutions presented here can be used to improve the design of mixers.