Apichat Suddeepong

Strength development in blended cement admixed saline clay

Abstract Cement stabilization is extensively used to improve engineering properties of soft saline clays. The effect of salinity, which is modified by geological and climate changes, on the strength development in cement admixed saline clay is investigated in this paper. For a particular curing time and salt content, the strength development in saline clay admixed with cement is governed by the clay-water/cement ratio, w c / C . The strength increases with the decrease of w c / C . The increase in salt content for a particular water content decreases the inter-particle attraction of the clay and the cementation bond strength. Hence, for the same clay-water/cement ratio, the strength of the cement admixed saline clay decreases with increasing salt content. In order to increase strength, and improve the economic and environmental impact, fly ash (FA) and biomass ash (BA) can be used to substitute Portland cement. The influence of FA and BA on the strength development of cement admixed saline clay was investigated with unconfined compressive (UC) test and thermogravimetric (TG) analysis. FA and BA were dispersing materials, increasing the reactive surface of the cement grains, and hence strength increases as well. The clay-water/cement ratio hypothesis was used successfully to analyze and assess the strength development of blended cement admixed saline clay at various salt contents. An addition of 25% ash can replace up to 15.8% of cement.

Water-Void to Cement Ratio Identity of Lightweight Cellular-Cemented Material

AbstractLightweight cellular cemented clays have wide range of applications in the infrastructure rehabilitation and in the construction of new facilities. Since the inception of this method, the developments in the plant and machinery as well as associated field techniques have surpassed the basic understanding of strength developments in lightweight cellular cemented clay. In this paper, an attempt is made to identify the dominant parameter, governing the unit weight, strength, and compressibility characteristics of lightweight cellular cemented clay, which helps control input of water, air foam, and cementing agent to attain unit weight and strength development with curing time. From this research, it is discovered that water-void/cement ratio, wV/C is the dominant parameter for the above purposes. From the critical analysis of test results, a mix design method to attain the target strength and unit weight is suggested. This method is useful from both engineering and economic perspectives.

Interface shear behaviours between recycled concrete aggregate and geogrids for pavement applications

ABSTRACT The usage of recycled concrete aggregate (RCA) in pavement applications is a sustainable approach for future infrastructure development, given the significant environmental benefits. Geogrid reinforcement of RCA can also improve the tensile and flexural strengths of the pavement structure to sustain high traffic loadings. The effect of aperture size, tensile strength of geogrids, normal stress and gradation on shear interaction between geogrids and RCA was investigated in this research, with the usage of a large-scale direct shear test (LDST) apparatus. Three types of biaxial geogrids, with different aperture sizes and tensile strengths, and two RCA samples with different gradations were used in this study. The interface shear strength was found to be highly dependent upon the aperture width of the geogrids, D, as well as the RCA particles finer than the aperture width of geogrid, FD. Based on the analysis of test results, a linear relationship between interface shear strength coefficient, α, the ratio of interface shear strength of geogrid/RCA and shear strength of RCA was proposed, with respect to the D/FD ratio. The proposed relationship will be useful for a rapid assessment of the interface shear strength coefficient of geogrid-reinforced RCA based on the aperture size of geogrids and RCA gradation properties.

Effect of cumulative traffic and statistical predictive modelling of field skid resistance

Skid resistance value (SRV) is a significant parameter representing the road safety condition. The measurement of SRV at different times after the construction is time-consuming and costly. To accurately predict the reduction of SRV, the SRV reduction model has been developed based on the aggregate and asphalt concrete mixture characteristics and field cumulative traffic volumes. In this study, three main types of aggregates typically used in pavements in Thailand, being limestone, granite and basalt were used to make asphalt concrete. The standard dense-grade asphalt concrete mixtures of 9.5 and 12.5 mm maximum aggregate sizes were designed and constructed at the studied sites (12 project sites located in 6 provinces). The SRVs were measured at every 50,000 passenger car unit (pcu) by the British pendulum tester for 3–4 years after the end of construction. Based on the statistical analysis of the test results, the SRV at various cumulative traffic volumes can be predicted using asphalt concrete mixture characteristics and initial SRV (after the end of construction) as prime parameters. The model will be recommended for inclusion in the Department of Rural Roads, Thailand preventive scheme for road safety management protocols.