FREEZE/THAW PERFORMANCE OF CONCRETE USING GRANULATED RUBBER CRUMB

This paper evaluates the properties and use of recycled rubber tyres in the form of rubber crumb as a freeze/thaw protection agent when used in concrete.Reusing scrap tyres in the form of rubber crumb in concrete could benefit the environment by contributing to the percentage of tyres used for a variety of recycling processes such as carpet underlay or tyre derived fuel,thus reducing disposal of tyres to landfill sites and the chemical usage of air entraining agents as a means of achieving freeze/thaw protection.Concrete cubes of 100mm were produced from design mixes which have been classified as plain,air entrained and rubber crumb and subjected to freeze/thaw cycles at 5 days of age.Thawing was conducted in water to ensure full saturation of pores and maximum stress on the concrete samples.The rubber crumb and plain concrete mixes were compared against the freeze/thaw performance of that entrained with air.Air entrainment is known to protect against freeze/thaw action.Rubber crumb when used at a 0.5%addition by volume provided the optimum freeze/thaw protection whilst maintaining the maximum compressive strength.The research shows that rubber crumb was effective at providing freeze/thaw protection albeit with a reduced compressive strength when compared to air entrained concrete.The practical constraints of the test program were time and freezer space so the test was limited to 50 freeze/thaw cycles,which was sufficient for conclusions to be drawn.This paper contributes to the understanding of the effects of varying doses of rubber crumb in concrete when used as a freeze/thaw protection additive.The final compressive strength of the concrete mixes tested at freeze/thaw and non freeze/thaw conditions are determined.The compaction of concrete is raised as an area of concern with regard to rubber particle separation within the plastic phase of the concrete’s life.

Comparative proteomics analysis of tea leaves exposed to subzero temperature:Molecular mechanism of freeze injury

Tea freeze injury is one of the most severe agro-meteorological disasters,which leads to sizable losses of tea production in China.The freezing resistant ability of overwintering tea trees becomes weaker and weaker from early-spring to late-spring.If it decreases to critical temperature of-2℃or lower in the stage with one or two leaves,tea trees suffer from freeze injury and the yield or quality of spring tea production could decrease greatly.Although measurements have been taken to prevent such damage,the physiological and biochemical mechanism of how tea(Camellia Sinensis)plant response to freeze injury is still to be elucidated.A comparative proteomics analysis was made on tea leaves at the two-leaf stage.The differential image analysis showed 46 spots with density changes(29 spots increased and 17 spots decreased;p<0.01)in the freeze injury group compared with the control group.Thirty eight differential protein spots(p<0.01)with good resolution and relatively high abundance in MS were subjected to further protein identification.Among them,all 17 up-regulated spots were collected whereas only six of the down-regulated spots were selected.These differentially expressed proteins including heat shock protein 70,oxygen-evolving enhancer protein,adenosine triphosphate synthase,S-adenosylmethionine synthetase and some enzymes involved in carbohydrate metabolism,were shown responsive to freeze injury.The results would greatly increase the comprehension of the molecular mechanism for freeze injury and provide a better decision making for freeze protection and control.