Effect of silica fume on the behavior of lightweight reinforced concrete beams made from crushed clay bricks

Crushed over-burnt clay bricks(COBCBs)are a promising alternative to the natural gravel aggregate in lightweight concrete(LWC)production because of their high strength-to-weight ratio.Besides,COBCBs are considered a green aggregate as they solve the problem of solid waste disposal.In this paper,a total of fifteen reinforced concrete(RC)beams were constructed and tested up to failure.The experimental beams were classified into five groups.The con-trol beams were cast with normal weight concrete(NWC),while the remaining four groups of beams were prepared from LWC.The test parameters were the concrete type,reinforcement ratio and silica fume(SF)content.The behavior of beams was evaluated in terms of the crack pattern,failure mode,ultimate deflection,and ductility.The experimen-tal results suggested that the weight and strength of the concrete prepared satisfied the requirements of LWC.In addition,the increase in the reinforcement ratio and SF content improved the behavior of the beams.It is noteworthy that the SF addition caused measurable enhancements to the majority of the performance characteristics of LWC beams.Thus,COBCBs were successfully used as coarse aggregates in the production of high-quality LWC.Both ACI 318-19 and CSA-A23.3-19 made acceptable predictions of the cracking moment,ultimate capacity and mid-span deflection.

Laboratory evaluation of cement treated aggregate containing crushed clay brick

The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5 % cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density （MDD） and a higher optimum moisture content （OMC）. Moreover, the unconfined compressive strength （UCS）, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pave- ment design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% （5 % cement content in the mixture）. Furthermore, it needs to be noted that the cement treated aggre- gate which contains crushed clay bricks should be cautiously used in the cold region due to its insuffi- cient frost resistance performance.