Red clay belongs to region special soil.It has engineering geological properties that are different from general soils.The natural red clay has high ratio void ratio,high moisturecontent,low density and so on.But red clay has non-corresponding high strength,bearing capacity of foundation and low compressibility. With the high speed development of China economy,the main soil named red clay in South is used as bearing stratum of many building foundations.However,when red clay is used as foundation,it is regarded as gerenal clay to consider its bearing capacity of foundation.So this will cause two disadvantages.First,potential is not given full play,resulting in considerable waste.Second,red clay has some special properties,such as high woid ratio,softening in water.These properties will bring hidden troubles,causing some bad accidents.These are caused by lacking of knowledge to engineering properties.Xiamen locates in southeast of China,and red clay is widely distributed.It is formed by accumulation through laterization of granites and basalts.So it is essential to study red clay.In this article,literatures of red clay in Xiamen are collected.Indoor conventional geotechnical tests are done,some engineering property parameters are obtained.

In order to investigate factors influencing workability of recycled aggregates (RA) concrete, such as water amount, sand ratio and RA replacement percentage, 10 pitch of RA concrete was prepared for measurement of workability and a formula was used for calculating effect of water amount on slump of RA concrete. Experimental results and formula induction indicated that there are logarithmic relationship between flowability of fresh concrete and water amount and ratio of aggregates to cement . The flowability will logarithmically increase with increase of water amount and decrease of aggregates cement ratio. The optimum sand ratio for RA concrete can be determined by measurement of slump. Slump decreases with RA replacement percentage and there is a very good linear relationship between them. When water amount increases, slump increases and when replacement percentage of RA increases, slump decrease. Under different water amount, effect degrees of replacement percentage of RA on slump are very similar and under different replacement percentage of RA, effect degrees of water amount on slump are also very similar.

This work has launched a comprehensive investigation on the macro performance and micro structure of mass concrete produced with alkali-active sand slate powder (ASSP) for use as the mineral admixture and a thorough analysis on its technical and economic effects is also conducted. Results indicated ternary blend with hybrid of 5–8 wt.% silica fume (SF) and 15–20 wt.% ASSP has the optimal compressive and flexural strength. ASSP particle participates in hydration, accelerates hydration of cement clinker within 8.5 hours, and reduces the autogenous strain of pastes by 164 × 10−6 in case of dosage less than 25% by mass. Improvement in the mechanical and deformation properties of concrete produced with the hybrid of SF and ASSP is attributed to better particles gradation, compactness enhancement, and transformation in products of hydration. On the whole, it provides another new approach for use of alkali-active rock after second processing as mineral admixture in hydraulic concrete in terms of good performance and economic effects.