Deliverables
Advanced experimental studies were performed on the deformational behaviour of LWAC in the phase of hardening. Emphasis was on mixtures for High Strength LWAC (HSLWAC). High strength concrete made with normal weight aggregates are generally made with a low water/cement ratio and exhibit, for that reason, a large autogenous shrinkage and are prone to cracking in the early stage of hardening. If made with water saturated lightweight aggregates, these low water/cement ratio mixtures hardly exhibit autogenous shrinkage. Some LWAC mixtures even exhibit swelling throughout the hydration process. Experimental studies are performed on deformational behaviour and development of stresses at early ages on different LWAC mixtures. It was found that:
-LWAC mixture made with saturated LWA exhibit swelling, which swelling compensates the autogenous shrinkage of the cement paste.
-If 25% by volume of the coarse normal weight aggregate is replaced by water saturated LWA the autogenous shrinkage of the mixtures is reduced by more than 50%.
-In semi-adiabatic studies the risk of cracking of HSLWAC was mainly determined by the thermal strains of the concrete.
The results were reported jointly with SINTEF (No) in a report entitled: Evaluation of the early age cracking of lightweight aggregate concrete.
URL: http://www.sintef.no/bygg/sement/elcon/index.htm
TU Delft was active in co-ordinating, writing and final editing the state-of-the-art report on materials properties of lightweight aggregate concrete. The work resulted in the state-of-the-report on materials properties, entitled LWAC Materials Properties State-of-the-Art. The report, which is available on the internet, is a reference work for all those who are interested in lightweight aggregate concrete. Subsequent chapters cover Introduction, Potentials, Mix design and production, Materials behaviour are early age, Porosity and permeability, Thermal properties and fire resistance, Mechanical properties, Time dependent properties, Durability of LWAC and Evaluation. In the Evaluation a list of research needs is listed. This list has formed the basis for in-depth experimental research. An extensive list of references provides the reader with the possibility of consult the relevant literature on specific topics.
URL: http://www.sintef.no/bygg/sement/elcon/index.htm
Long-term effects in LWAC: Strength under sustained loading:
Because of a lower strength of LWA compared to normal strength aggregate, LWAC is expected to demonstrate a higher sensitivity to failure under sustained loading than normal weight concrete (NWC). Up to now little experimental data is available to confirm this expectation. Therefore, experimental studies were performed on the strength of LWAC under sustained loading. It was found that failure of LWAC while under sustained loading occurred sooner than in case of normal weight concrete. This finding is important in view of safety considerations in LWAC structures. Results are reported by in a report on time-dependent behaviour of LWAC, entitled: Time dependent behaviour of high strength LWAC
Note: This experimental study was performed instead of a theoretical study on numerical simulations of moisture transport in hydrating LWAC. This change was made because of the need for experimental data on this important design problem.
Long-term effects in LWAC: Shrinkage of high strength LWAC
Experimental studies were performed on shrinkage of high strength LWAC. The effect of the degree of saturation of the LWA particles and of the size of the specimen was investigated. It was found that particularly when shrinkage started at early ages, the shrinkage predictions with formulae given in currently used design codes are not accurate and need reconsideration. Results are reported in a report entitled: Time dependent behaviour of high strength LWAC
URL: http://www.sintef.no/bygg/sement/elcon/index.htm
Searching for OpenAIRE data...
There was an error trying to search data from OpenAIRE
No results available