碾压水泥混凝土路面施工

通过结合工程的室内外试验,得到了碾压水泥混凝土路面的强度与用水量、水泥用量的关系,探讨了相关的施 工技术问题。

Strength of copolymer grouting material based on orthogonal experiment

Using the orthogonal experimental design method involving three factors and three levels, the flexural strength and the compressive strength of copolymer grouting material were studied with different compositions of water-cement ratio （mass fraction of water to cement）, epoxy resin content, and waterborne epoxy curing agent content. By orthogonal range and variance analysis, the orders of three factors to influence the strength, the significance levels of different factors, and the optimized compound ratio scheme of copolymer grouting material mixture at different curing ages were determined. An empirical relationship among the strength of copolymer grouting material, the water-cement ratio, the epoxy resin content, and the waterborne epoxy curing agent content was established by multivariate regression analysis. The results indicate that water-cement ratio is the most principal and significant influencing factor on the strength. Epoxy resin content and waterbome epoxy curing agent content also have a significant influence on the strength. But epoxy resin content has a greater influence on the 7-day and 28-day flexural strength, and waterborne epoxy curing agent content has a greater influence on the 3-day flexural strength and the compressive strength. The copolymer grouting material with water-cement ratio of 0.4, epoxy resin content of 8% （mass fraction） and waterbome epoxy curing agent content of 2% （mass fraction） is the best one for repairing of cement concrete pavement. The flexural strength and the compressive strength have good correlation, and the ratio of compressive strength to flexural strength is between 1.0 and 3.3.

Characterizing properties of magnesium oxychloride cement concrete pavement

The performance of magnesium oxychloride cement concrete(MOCC)in road engineering in the arid region in northwest China was investigated over a two-year period.Two categories of MOCC pavement,light-burnt magnesia concrete road(Road-L)and dolomite concrete road(Road-D),were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite(1:3 by mass),respectively.Variations in the properties of the MOCC pavement,such as compressive and flexural strength,mineralogical phase,and microstructure,after being exposed to two rainy seasons in the field were monitored.The compressive strength of the cored samples were conducted after being aged for 28 d,and the compressive and flexural strength were tested at ages of 1,2,3,28,90,180,270,360 and 720 d.The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D.Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons,with the major hydration products being 5Mg(OH)2 MgCl28H2O(Phase 5)and 3Mg(OH)2 MgCl28H2O(Phase 3).The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.

Constraints in Using Manufactured Sands in Concrete Pavements in Australia

Due to the shortages of natural sands along the east coast of Australia in particular and the need to fully utilise fines produced in quarry operations, progress has been made in utilising blends of manufactured sands and natural sands in concrete pavements. This paper documents some of the constraints in utilising larger proportions of manufactured sands in concrete pavements. These constraints are mainly caused by the current level of knowledge regarding the impact of manufactured sands on skid and abrasion resistance of concrete pavements. This paper presents a brief review of literature on this subject in the USA, France and UK. It also briefly documents work recently carried out in Australia by CCAA （Cement Concrete and Aggregates Australia）, referring to the skid and abrasion resistance of concrete pavements using manufactured sands. The paper concludes that there is no relationship between the free silica content and the skid resistance. With regard to the abrasion resistance, it is rather the curing conditions and the compressive strength that are more important in achieving good results.

Curling of New Concrete Pavement and Long-Term Performance

Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. Performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.